feat(saml): wire SAML 2.0 SSO end-to-end (pure-Rust) + Settings/Storage UI consolidation (v0.5.1)

SAML SSO (the config was storage-only since v0.4.5; now it logs you in):
- New openpxe-core::saml — pure-Rust SP built on bergshamra (XML-DSig +
  exclusive c14n via RustCrypto, no OpenSSL/xmlsec/libxml2). The static
  musl binary stays C-free; samael was rejected for hard-requiring OpenSSL.
  * metadata.rs   — parse IdP EntityDescriptor (SSO URLs + signing certs),
                    build our SP metadata.
  * authn_request.rs — build + HTTP-Redirect-encode AuthnRequests.
  * response.rs   — verify the signature against the pinned IdP cert
                    (trusted_keys_only + strict_verification for XSW),
                    then enforce Status/Destination/Audience/time-bounds/
                    signature-scope. Stateless; returns the IDs the HTTP
                    layer needs.
- http-api saml_routes: GET /api/sso/login (302 to IdP), POST /api/sso/acs
  (verify -> InResponseTo correlation / IdP-initiated gating / assertion
  replay guard -> mint operator session -> 302), GET /api/sso/metadata.
  Added to the pre-auth allowlist; /api/sso config stays gated.
- SsoConfig gains entity_id (SP Entity ID, defaults to public base URL)
  and allow_idp_initiated (default off), mirroring FleetDM.
- Access model: any IdP-authenticated, cryptographically-verified user gets
  an operator session (single-tier; local admin remains the fallback owner).
- Login page: the "Sign in with <IdP>" button now drives the real flow and
  surfaces sso_error redirects.

UI consolidation:
- Removed the Advanced sidebar tab; folded its webhook-notifications +
  API-reference cards into a collapsible "Advanced" disclosure at the
  bottom of Settings.
- Merged the Storage tab's separate SMB and NFS cards into one "Remote
  shares" card with a protocol dropdown and a unified, protocol-badged
  table. No backend changes — same /api/smb-shares + /api/nfs-shares.

Tests: 17 SAML core tests (accept + reject tampered/unsigned/wrong-key/
wrong-audience/expired/future/wrong-issuer/non-success) and 6 ACS
integration tests (happy path, IdP-initiated gating, SP correlation,
replay, garbage). Full workspace: 206 tests green, clippy clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

Cargo.toml

@@ -12,7 +12,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.5.0"
+version = "0.5.1"
 edition = "2021"
 rust-version = "1.95"
 license = "MIT OR Apache-2.0"
@@ -71,6 +71,20 @@ nfs3_types = "0.5"
 # to match reqwest and stay musl-static-friendly — no OpenSSL.
 lettre = { version = "0.11", default-features = false, features = ["smtp-transport", "tokio1-rustls-tls", "builder", "hostname"] }
 
+# v0.5.1: pure-Rust SAML 2.0 Service Provider. bergshamra does XML-DSig
+# verification + exclusive c14n with RustCrypto (no OpenSSL/xmlsec/libxml2
+# C deps), so the static musl binary stays OpenSSL-free — samael was
+# rejected precisely because it hard-requires OpenSSL. We build the thin
+# SP layer (AuthnRequest, metadata parse, SAMLResponse semantics) on top.
+bergshamra = "0.4"
+roxmltree = "0.21"
+quick-xml = "0.40"
+x509-parser = "0.18"
+# flate2 default backend is miniz_oxide (pure Rust) — do NOT enable the
+# zlib/zlib-ng C backends, which would break the musl-static build.
+flate2 = "1.1"
+base64 = "0.22"
+
 openpxe-core = { path = "crates/core" }
 openpxe-dhcp-proxy = { path = "crates/dhcp-proxy" }
 openpxe-tftp = { path = "crates/tftp" }

crates/core/Cargo.toml

@@ -25,5 +25,19 @@ tokio = { workspace = true, features = ["sync", "rt", "macros", "time"] }
 # for per-ISO boot passwords; just re-exported here.
 bcrypt.workspace = true
 
+# v0.5.1: pure-Rust SAML 2.0 SP. bergshamra = XML-DSig verify + exclusive
+# c14n (no OpenSSL/C). roxmltree/quick-xml parse + build SAML XML;
+# x509-parser pulls the IdP signing cert out of metadata; flate2+base64
+# encode the HTTP-Redirect binding's SAMLRequest.
+bergshamra.workspace = true
+roxmltree.workspace = true
+quick-xml.workspace = true
+x509-parser.workspace = true
+flate2.workspace = true
+base64.workspace = true
+
 [dev-dependencies]
 tempfile = "3.12"
+# v0.5.1: generate a throwaway self-signed signing cert/key so SAML
+# verification tests can produce genuinely signed SAMLResponses.
+rcgen = "0.13"

crates/core/src/lib.rs

@@ -14,6 +14,7 @@ pub mod log_bus;
 pub mod metrics;
 pub mod notify;
 pub mod queue;
+pub mod saml;
 pub mod settings;
 pub mod sso;
 pub mod wol;
@@ -23,7 +24,6 @@ pub use auth::{AdminAccount, AdminPublic, AdminStore};
 pub use boot_log::{BootEvent, BootLog};
 pub use branding::{ext_for_mime, BrandingStore, ALLOWED_LOGO_MIMES, MAX_LOGO_BYTES};
 pub use client::{ClientEvent, ClientRegistry, ClientSnapshot};
-pub use sso::{SsoConfig, SsoStore};
 pub use config::{Config, DhcpMode, NetworkConfig, Paths, ServerConfig};
 pub use error::{Error, Result};
 pub use host_bindings::{normalize_mac, HostBinding, HostBindings};
@@ -31,4 +31,6 @@ pub use log_bus::{LogBus, LogBusLayer, LogLine};
 pub use metrics::{HttpRoute, Metrics};
 pub use notify::{NotifyConfig, NotifyKind, NotifyStore};
 pub use queue::{DeploymentQueue, QueueEntry};
+pub use saml::{IdpMetadata, SamlError, SpParams, VerifiedPrincipal, VerifiedResponse};
 pub use settings::{Settings, SettingsStore, TimeoutAction};
+pub use sso::{SsoConfig, SsoStore};

crates/core/src/saml/authn_request.rs

@@ -0,0 +1,188 @@
+//! AuthnRequest construction + HTTP-Redirect binding encoding.
+//!
+//! For SP-initiated login we build an `<AuthnRequest>`, then encode it for the
+//! HTTP-Redirect binding: raw DEFLATE (RFC 1951) → base64 → percent-encode,
+//! appended as the `SAMLRequest` query parameter. AuthnRequests are sent
+//! unsigned in this release (the IdP must not require client signatures).
+
+use std::fmt::Write as _;
+use std::io::Write as _;
+
+use base64::Engine;
+use flate2::write::DeflateEncoder;
+use flate2::Compression;
+use time::format_description::well_known::Rfc3339;
+use time::OffsetDateTime;
+
+use super::{SamlError, SpParams};
+
+const NS_PROTOCOL: &str = "urn:oasis:names:tc:SAML:2.0:protocol";
+const NS_ASSERTION: &str = "urn:oasis:names:tc:SAML:2.0:assertion";
+const NAMEID_EMAIL: &str = "urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress";
+const BINDING_POST: &str = "urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST";
+
+/// A built AuthnRequest, ready to redirect the browser to the IdP.
+#[derive(Debug, Clone)]
+pub struct AuthnRequest {
+    /// The request `ID` — the caller records this so the matching response's
+    /// `InResponseTo` can be correlated (replay/CSRF protection).
+    pub id: String,
+    /// The full IdP URL to 302 the browser to (includes `SAMLRequest` and,
+    /// when supplied, `RelayState`).
+    pub location: String,
+}
+
+/// Build an AuthnRequest targeting `idp_sso_url` and encode it for the
+/// HTTP-Redirect binding. `relay_state`, if given, round-trips back to us via
+/// the response (we use it to send the operator to their intended page).
+pub fn build(
+    sp: &SpParams,
+    idp_sso_url: &str,
+    relay_state: Option<&str>,
+) -> Result<AuthnRequest, SamlError> {
+    let id = format!("_{}", uuid::Uuid::new_v4().simple());
+    let issue_instant = OffsetDateTime::now_utc()
+        .replace_nanosecond(0)
+        .unwrap_or_else(|_| OffsetDateTime::now_utc())
+        .format(&Rfc3339)
+        .map_err(|e| SamlError::Timestamp(e.to_string()))?;
+
+    let xml = format!(
+        r#"<samlp:AuthnRequest xmlns:samlp="{NS_PROTOCOL}" xmlns:saml="{NS_ASSERTION}" ID="{id}" Version="2.0" IssueInstant="{instant}" Destination="{dest}" ProtocolBinding="{BINDING_POST}" AssertionConsumerServiceURL="{acs}"><saml:Issuer>{issuer}</saml:Issuer><samlp:NameIDPolicy Format="{NAMEID_EMAIL}" AllowCreate="true"/></samlp:AuthnRequest>"#,
+        instant = issue_instant,
+        dest = xml_escape(idp_sso_url),
+        acs = xml_escape(&sp.acs_url),
+        issuer = xml_escape(&sp.entity_id),
+    );
+
+    let encoded = deflate_base64(&xml)?;
+
+    let sep = if idp_sso_url.contains('?') { '&' } else { '?' };
+    let mut location = format!("{idp_sso_url}{sep}SAMLRequest={}", pct_encode(&encoded));
+    if let Some(rs) = relay_state {
+        location.push_str("&RelayState=");
+        location.push_str(&pct_encode(rs));
+    }
+
+    Ok(AuthnRequest { id, location })
+}
+
+/// Raw-DEFLATE then base64 — the HTTP-Redirect binding's `SAMLRequest` payload.
+fn deflate_base64(xml: &str) -> Result<String, SamlError> {
+    let mut enc = DeflateEncoder::new(Vec::new(), Compression::default());
+    enc.write_all(xml.as_bytes())
+        .and_then(|()| enc.try_finish())
+        .map_err(|e| SamlError::Xml(format!("deflate: {e}")))?;
+    let compressed = enc
+        .finish()
+        .map_err(|e| SamlError::Xml(format!("deflate: {e}")))?;
+    Ok(base64::engine::general_purpose::STANDARD.encode(compressed))
+}
+
+/// Percent-encode a query-string component (RFC 3986 unreserved set passes
+/// through; everything else is `%XX`).
+fn pct_encode(s: &str) -> String {
+    let mut out = String::with_capacity(s.len() * 3);
+    for b in s.bytes() {
+        match b {
+            b'A'..=b'Z' | b'a'..=b'z' | b'0'..=b'9' | b'-' | b'_' | b'.' | b'~' => {
+                out.push(b as char);
+            }
+            _ => {
+                let _ = write!(out, "%{b:02X}");
+            }
+        }
+    }
+    out
+}
+
+fn xml_escape(s: &str) -> String {
+    let mut out = String::with_capacity(s.len());
+    for c in s.chars() {
+        match c {
+            '&' => out.push_str("&amp;"),
+            '<' => out.push_str("&lt;"),
+            '>' => out.push_str("&gt;"),
+            '"' => out.push_str("&quot;"),
+            '\'' => out.push_str("&apos;"),
+            _ => out.push(c),
+        }
+    }
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use flate2::read::DeflateDecoder;
+    use std::io::Read;
+
+    fn sp() -> SpParams {
+        SpParams {
+            entity_id: "https://pxe.example.com".into(),
+            acs_url: "https://pxe.example.com/api/sso/acs".into(),
+        }
+    }
+
+    fn pct_decode(s: &str) -> Vec<u8> {
+        let bytes = s.as_bytes();
+        let mut out = Vec::with_capacity(bytes.len());
+        let mut i = 0;
+        while i < bytes.len() {
+            if bytes[i] == b'%' && i + 2 < bytes.len() {
+                let hi = (bytes[i + 1] as char).to_digit(16).unwrap();
+                let lo = (bytes[i + 2] as char).to_digit(16).unwrap();
+                out.push((hi * 16 + lo) as u8);
+                i += 3;
+            } else {
+                out.push(bytes[i]);
+                i += 1;
+            }
+        }
+        out
+    }
+
+    #[test]
+    fn id_is_ncname_and_location_has_request() {
+        let req = build(&sp(), "https://idp.example.com/sso", Some("/dashboard")).unwrap();
+        assert!(req.id.starts_with('_'));
+        assert!(req
+            .location
+            .starts_with("https://idp.example.com/sso?SAMLRequest="));
+        assert!(req.location.contains("&RelayState=%2Fdashboard"));
+    }
+
+    #[test]
+    fn redirect_payload_round_trips_to_our_authn_request() {
+        let req = build(&sp(), "https://idp.example.com/sso", None).unwrap();
+        // Pull SAMLRequest value out of the query string.
+        let q = req.location.split("SAMLRequest=").nth(1).unwrap();
+        let val = q.split('&').next().unwrap();
+        let compressed = base64::engine::general_purpose::STANDARD
+            .decode(pct_decode(val))
+            .unwrap();
+        let mut inflate = DeflateDecoder::new(&compressed[..]);
+        let mut xml = String::new();
+        inflate.read_to_string(&mut xml).unwrap();
+
+        let doc = roxmltree::Document::parse(&xml).unwrap();
+        let root = doc.root_element();
+        assert_eq!(root.tag_name().name(), "AuthnRequest");
+        assert_eq!(root.attribute("ID").unwrap(), req.id);
+        assert_eq!(
+            root.attribute("AssertionConsumerServiceURL").unwrap(),
+            "https://pxe.example.com/api/sso/acs"
+        );
+        let issuer = root
+            .descendants()
+            .find(|n| n.tag_name().name() == "Issuer")
+            .unwrap();
+        assert_eq!(issuer.text().unwrap(), "https://pxe.example.com");
+    }
+
+    #[test]
+    fn existing_query_uses_ampersand_separator() {
+        let req = build(&sp(), "https://idp.example.com/sso?foo=bar", None).unwrap();
+        assert!(req.location.contains("?foo=bar&SAMLRequest="));
+    }
+}

crates/core/src/saml/metadata.rs

@@ -0,0 +1,241 @@
+//! IdP metadata parsing + SP metadata generation.
+//!
+//! We parse only what the SP flow needs: the IdP Entity ID, its
+//! `SingleSignOnService` endpoints (HTTP-Redirect / HTTP-POST), and the
+//! X.509 signing certificate(s). Everything else in the document is ignored.
+
+use base64::Engine;
+
+use super::{SamlError, SpParams};
+
+/// SAML 2.0 binding URIs.
+pub const BINDING_REDIRECT: &str = "urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect";
+pub const BINDING_POST: &str = "urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST";
+
+/// The subset of an IdP's `EntityDescriptor` the SP flow consumes.
+#[derive(Debug, Clone)]
+pub struct IdpMetadata {
+    /// The IdP's Entity ID — we require incoming assertions to be issued by it.
+    pub entity_id: String,
+    /// SSO endpoint for the HTTP-Redirect binding (where we send AuthnRequests).
+    pub sso_redirect_url: Option<String>,
+    /// SSO endpoint for the HTTP-POST binding (fallback target).
+    pub sso_post_url: Option<String>,
+    /// DER-encoded X.509 signing certificate(s). More than one appears during
+    /// key rotation; verification tries each.
+    pub signing_certs_der: Vec<Vec<u8>>,
+}
+
+impl IdpMetadata {
+    /// Parse an IdP `EntityDescriptor` document.
+    ///
+    /// Robust to namespace-prefix variation (matches on local element names),
+    /// since IdPs disagree on prefixes (`md:`, `ns0:`, default, …).
+    pub fn parse(xml: &str) -> Result<Self, SamlError> {
+        let doc = roxmltree::Document::parse(xml).map_err(|e| SamlError::Xml(e.to_string()))?;
+        let root = doc.root_element();
+
+        // The signing IDP descriptor. Some metadata wraps multiple
+        // descriptors (AA, SP) in one document; we want IDPSSODescriptor.
+        let idp_desc = root
+            .descendants()
+            .find(|n| n.is_element() && n.tag_name().name() == "IDPSSODescriptor")
+            .ok_or_else(|| SamlError::Metadata("IDPSSODescriptor".into()))?;
+
+        // Entity ID lives on the EntityDescriptor (root, or an ancestor of the
+        // IDPSSODescriptor when several are nested).
+        let entity_id = idp_desc
+            .ancestors()
+            .find_map(|n| {
+                if n.tag_name().name() == "EntityDescriptor" {
+                    n.attribute("entityID")
+                } else {
+                    None
+                }
+            })
+            .or_else(|| root.attribute("entityID"))
+            .map(str::to_owned)
+            .ok_or_else(|| SamlError::Metadata("entityID".into()))?;
+
+        let mut sso_redirect_url = None;
+        let mut sso_post_url = None;
+        for sso in idp_desc
+            .children()
+            .filter(|n| n.is_element() && n.tag_name().name() == "SingleSignOnService")
+        {
+            let binding = sso.attribute("Binding").unwrap_or("");
+            let location = sso.attribute("Location").map(str::to_owned);
+            match binding {
+                BINDING_REDIRECT if sso_redirect_url.is_none() => sso_redirect_url = location,
+                BINDING_POST if sso_post_url.is_none() => sso_post_url = location,
+                _ => {}
+            }
+        }
+
+        // Signing certs: KeyDescriptor with use="signing" or no use attribute
+        // (a bare KeyDescriptor is valid for both signing and encryption).
+        let mut signing_certs_der = Vec::new();
+        for kd in idp_desc
+            .children()
+            .filter(|n| n.is_element() && n.tag_name().name() == "KeyDescriptor")
+        {
+            match kd.attribute("use") {
+                Some("signing") | None => {}
+                Some(_) => continue, // encryption-only key — skip
+            }
+            for cert_node in kd
+                .descendants()
+                .filter(|n| n.is_element() && n.tag_name().name() == "X509Certificate")
+            {
+                let b64: String = node_text(&cert_node)
+                    .chars()
+                    .filter(|c| !c.is_whitespace())
+                    .collect();
+                if b64.is_empty() {
+                    continue;
+                }
+                let der = base64::engine::general_purpose::STANDARD
+                    .decode(b64.as_bytes())
+                    .map_err(|e| SamlError::Base64(e.to_string()))?;
+                signing_certs_der.push(der);
+            }
+        }
+
+        if signing_certs_der.is_empty() {
+            return Err(SamlError::NoSigningCert);
+        }
+
+        Ok(Self {
+            entity_id,
+            sso_redirect_url,
+            sso_post_url,
+            signing_certs_der,
+        })
+    }
+
+    /// Preferred SSO destination for an outbound AuthnRequest: HTTP-Redirect
+    /// if advertised, otherwise HTTP-POST.
+    pub fn sso_destination(&self) -> Option<&str> {
+        self.sso_redirect_url
+            .as_deref()
+            .or(self.sso_post_url.as_deref())
+    }
+}
+
+/// Build our SP `EntityDescriptor` XML so an IdP admin can import OpenPXE as a
+/// relying party. Advertises the ACS URL (HTTP-POST binding) and an emailAddress
+/// NameID format — matching what the response path expects.
+pub fn build_sp_metadata(sp: &SpParams) -> String {
+    let entity = xml_escape(&sp.entity_id);
+    let acs = xml_escape(&sp.acs_url);
+    format!(
+        r#"<?xml version="1.0" encoding="UTF-8"?>
+<EntityDescriptor xmlns="urn:oasis:names:tc:SAML:2.0:metadata" entityID="{entity}">
+  <SPSSODescriptor AuthnRequestsSigned="false" WantAssertionsSigned="true" protocolSupportEnumeration="urn:oasis:names:tc:SAML:2.0:protocol">
+    <NameIDFormat>urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress</NameIDFormat>
+    <AssertionConsumerService Binding="{BINDING_POST}" Location="{acs}" index="0" isDefault="true"/>
+  </SPSSODescriptor>
+</EntityDescriptor>
+"#
+    )
+}
+
+/// Collect the concatenated text of an element's direct text children.
+fn node_text(n: &roxmltree::Node<'_, '_>) -> String {
+    n.children()
+        .filter(roxmltree::Node::is_text)
+        .filter_map(|c| c.text())
+        .collect()
+}
+
+/// Minimal XML attribute/text escaping for the values we interpolate.
+fn xml_escape(s: &str) -> String {
+    let mut out = String::with_capacity(s.len());
+    for c in s.chars() {
+        match c {
+            '&' => out.push_str("&amp;"),
+            '<' => out.push_str("&lt;"),
+            '>' => out.push_str("&gt;"),
+            '"' => out.push_str("&quot;"),
+            '\'' => out.push_str("&apos;"),
+            _ => out.push(c),
+        }
+    }
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // A trimmed-down Keycloak-style IdP descriptor (cert body is a stand-in;
+    // signing tests build real certs in the parent module's tests).
+    const SAMPLE: &str = r#"<md:EntityDescriptor xmlns:md="urn:oasis:names:tc:SAML:2.0:metadata"
+        xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
+        entityID="https://idp.example.com/realms/fleet">
+      <md:IDPSSODescriptor protocolSupportEnumeration="urn:oasis:names:tc:SAML:2.0:protocol">
+        <md:KeyDescriptor use="signing">
+          <ds:KeyInfo><ds:X509Data><ds:X509Certificate>
+            QUJDREVG
+          </ds:X509Certificate></ds:X509Data></ds:KeyInfo>
+        </md:KeyDescriptor>
+        <md:KeyDescriptor use="encryption">
+          <ds:KeyInfo><ds:X509Data><ds:X509Certificate>WlpaWg==</ds:X509Certificate></ds:X509Data></ds:KeyInfo>
+        </md:KeyDescriptor>
+        <md:SingleSignOnService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect"
+            Location="https://idp.example.com/realms/fleet/protocol/saml"/>
+        <md:SingleSignOnService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"
+            Location="https://idp.example.com/realms/fleet/protocol/saml"/>
+      </md:IDPSSODescriptor>
+    </md:EntityDescriptor>"#;
+
+    #[test]
+    fn parses_entity_sso_and_signing_cert() {
+        let m = IdpMetadata::parse(SAMPLE).unwrap();
+        assert_eq!(m.entity_id, "https://idp.example.com/realms/fleet");
+        assert_eq!(
+            m.sso_redirect_url.as_deref(),
+            Some("https://idp.example.com/realms/fleet/protocol/saml")
+        );
+        assert!(m.sso_post_url.is_some());
+        // Only the signing KeyDescriptor's cert is collected (ABCDEF), not the
+        // encryption one (ZZZZ).
+        assert_eq!(m.signing_certs_der.len(), 1);
+        assert_eq!(m.signing_certs_der[0], b"ABCDEF");
+    }
+
+    #[test]
+    fn missing_signing_cert_is_rejected() {
+        let xml = r#"<EntityDescriptor xmlns="urn:oasis:names:tc:SAML:2.0:metadata" entityID="x">
+            <IDPSSODescriptor>
+              <SingleSignOnService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect" Location="https://x/sso"/>
+            </IDPSSODescriptor></EntityDescriptor>"#;
+        assert!(matches!(
+            IdpMetadata::parse(xml),
+            Err(SamlError::NoSigningCert)
+        ));
+    }
+
+    #[test]
+    fn missing_idp_descriptor_is_rejected() {
+        let xml = r#"<EntityDescriptor xmlns="urn:oasis:names:tc:SAML:2.0:metadata" entityID="x"></EntityDescriptor>"#;
+        assert!(matches!(
+            IdpMetadata::parse(xml),
+            Err(SamlError::Metadata(_))
+        ));
+    }
+
+    #[test]
+    fn sp_metadata_contains_entity_and_acs() {
+        let sp = SpParams {
+            entity_id: "https://pxe.example.com".into(),
+            acs_url: "https://pxe.example.com/api/sso/acs".into(),
+        };
+        let xml = build_sp_metadata(&sp);
+        assert!(xml.contains(r#"entityID="https://pxe.example.com""#));
+        assert!(xml.contains("https://pxe.example.com/api/sso/acs"));
+        assert!(xml.contains(BINDING_POST));
+        // Must be well-formed.
+        roxmltree::Document::parse(&xml).unwrap();
+    }
+}

crates/core/src/saml/mod.rs

@@ -0,0 +1,92 @@
+//! Pure-Rust SAML 2.0 Service Provider (v0.5.1).
+//!
+//! This module implements the SP half of a SAML Web-Browser-SSO profile:
+//!
+//! * [`metadata`] — parse the IdP's `EntityDescriptor` (SSO URLs + signing
+//!   certificates) and build *our* SP metadata for the IdP admin to import.
+//! * [`authn_request`] — build an `AuthnRequest` and encode it for the
+//!   HTTP-Redirect binding.
+//! * [`response`] — decode a `SAMLResponse`, **verify its XML signature**
+//!   against the IdP's pinned certificate (via the pure-Rust `bergshamra`
+//!   crate — no OpenSSL/libxml2/xmlsec, so the static musl binary stays
+//!   C-free), then enforce the SP-side semantic checks (Status, Destination,
+//!   Audience, time bounds) that are where SAML SPs actually get attacked.
+//!
+//! Stateful checks (replay of assertion IDs, correlating `InResponseTo`
+//! against requests *we* issued, gating IdP-initiated login) live in the
+//! HTTP layer — [`response::consume`] is deliberately stateless and returns
+//! the IDs the caller needs to perform them.
+//!
+//! Access model: any assertion the IdP authenticates and we cryptographically
+//! verify yields an operator [`VerifiedPrincipal`]. OpenPXE is single-tier —
+//! there is no per-user role table — and the local admin account remains a
+//! guaranteed fallback owner regardless of SSO state.
+
+pub mod authn_request;
+pub mod metadata;
+pub mod response;
+
+pub use authn_request::AuthnRequest;
+pub use metadata::IdpMetadata;
+pub use response::{VerifiedPrincipal, VerifiedResponse};
+
+use thiserror::Error;
+
+/// Default clock-skew tolerance applied to assertion time bounds. SAML IdPs
+/// and SPs rarely have perfectly synced clocks; 60s matches common practice
+/// (Shibboleth/FleetDM defaults are in this ballpark).
+pub const DEFAULT_CLOCK_SKEW_SECS: i64 = 60;
+
+/// Runtime SP parameters, derived from [`crate::SsoConfig`] + the advertised
+/// public base URL by the HTTP layer.
+#[derive(Debug, Clone)]
+pub struct SpParams {
+    /// Our SP Entity ID (the `<Issuer>` we send and the `Audience` we require
+    /// in responses). Defaults to the public base URL when the operator left
+    /// the Entity ID field blank.
+    pub entity_id: String,
+    /// The Assertion Consumer Service URL the IdP POSTs the response to —
+    /// `<public_base_url>/api/sso/acs`.
+    pub acs_url: String,
+}
+
+/// Everything that can go wrong consuming a SAML response. Kept coarse on
+/// purpose: the HTTP layer logs the detail and shows the operator a generic
+/// "SSO sign-in failed" — we never leak which specific check tripped to the
+/// browser, since that aids an attacker probing the SP.
+#[derive(Debug, Error)]
+pub enum SamlError {
+    #[error("SAML XML parse error: {0}")]
+    Xml(String),
+    #[error("IdP metadata is missing a required element: {0}")]
+    Metadata(String),
+    #[error("no usable IdP signing certificate in metadata")]
+    NoSigningCert,
+    #[error("signature verification failed: {0}")]
+    Signature(String),
+    #[error("the signature does not cover the assertion we read")]
+    SignatureScope,
+    #[error("SAML response status was not Success: {0}")]
+    Status(String),
+    #[error("response is missing a required element: {0}")]
+    MissingElement(String),
+    #[error("encrypted assertions are not supported in this release")]
+    EncryptedAssertionUnsupported,
+    #[error("expected exactly one assertion, found {0}")]
+    AssertionCount(usize),
+    #[error("issuer mismatch: response was not issued by the configured IdP")]
+    IssuerMismatch,
+    #[error("audience mismatch: assertion is not addressed to this service provider")]
+    AudienceMismatch,
+    #[error("response destination does not match our ACS URL")]
+    DestinationMismatch,
+    #[error("assertion is expired or not yet valid")]
+    TimeBounds,
+    #[error("invalid SAML timestamp: {0}")]
+    Timestamp(String),
+    #[error("base64 decode failed: {0}")]
+    Base64(String),
+}
+
+#[cfg(test)]
+mod tests;

crates/core/src/saml/response.rs

@@ -0,0 +1,294 @@
+//! SAMLResponse consumption: signature verification + SP-side validation.
+//!
+//! [`consume`] is intentionally **stateless** — it verifies the XML signature
+//! against the IdP's pinned certificate(s) and enforces every check that can
+//! be made from the response alone (Status, Destination, Issuer, Audience,
+//! time bounds, signature scope). It then returns the `assertion_id` and
+//! `in_response_to` so the HTTP layer can perform the *stateful* checks it
+//! owns: replay rejection, correlating the request we issued, and gating
+//! IdP-initiated login.
+
+use roxmltree::{Document, Node};
+use time::format_description::well_known::Rfc3339;
+use time::{Duration, OffsetDateTime};
+
+use super::metadata::IdpMetadata;
+use super::{SamlError, SpParams};
+
+const STATUS_SUCCESS: &str = "urn:oasis:names:tc:SAML:2.0:status:Success";
+
+/// The verified subject of a SAML assertion. OpenPXE is single-tier, so this
+/// is all an operator session needs.
+#[derive(Debug, Clone)]
+pub struct VerifiedPrincipal {
+    /// The `<NameID>` value (an email, per our requested NameID format).
+    pub name_id: String,
+    /// Email used as the session identity. Equals `name_id` for the
+    /// emailAddress NameID format.
+    pub email: String,
+    /// Human-readable display name, if the IdP sent one as an attribute.
+    pub display_name: Option<String>,
+}
+
+/// Result of a successful [`consume`]. The IDs/expiry feed the HTTP layer's
+/// stateful checks.
+#[derive(Debug, Clone)]
+pub struct VerifiedResponse {
+    pub principal: VerifiedPrincipal,
+    /// `InResponseTo` from the response, if present. `None` = unsolicited
+    /// (IdP-initiated) — the HTTP layer only accepts that when the operator
+    /// enabled it.
+    pub in_response_to: Option<String>,
+    /// The assertion's `ID` — used by the caller as the replay-guard key.
+    pub assertion_id: String,
+    /// The assertion's expiry (`Conditions/@NotOnOrAfter`) — the replay
+    /// guard can drop the consumed ID after this instant.
+    pub assertion_expiry: OffsetDateTime,
+    /// `AuthnStatement/@SessionIndex`, if present (useful for future SLO).
+    pub session_index: Option<String>,
+}
+
+/// Verify and validate a decoded `SAMLResponse` XML document.
+pub fn consume(
+    xml: &str,
+    sp: &SpParams,
+    idp: &IdpMetadata,
+    now: OffsetDateTime,
+    clock_skew: Duration,
+) -> Result<VerifiedResponse, SamlError> {
+    // 1. Cryptographically verify the signature against the pinned IdP cert(s).
+    //    `trusted_keys_only` ignores any cert embedded in the document's
+    //    KeyInfo, so an attacker can't substitute their own key.
+    let verified_uris = verify_signature(xml, &idp.signing_certs_der)?;
+
+    // 2. Parse for semantic validation.
+    let doc = Document::parse(xml).map_err(|e| SamlError::Xml(e.to_string()))?;
+    let root = doc.root_element();
+    if root.tag_name().name() != "Response" {
+        return Err(SamlError::MissingElement("Response".into()));
+    }
+    let response_id = root.attribute("ID").map(str::to_owned);
+    let in_response_to = root.attribute("InResponseTo").map(str::to_owned);
+
+    // 3. Status must be Success.
+    let status_value = root
+        .descendants()
+        .find(|n| n.is_element() && n.tag_name().name() == "StatusCode")
+        .and_then(|sc| sc.attribute("Value"))
+        .unwrap_or("");
+    if status_value != STATUS_SUCCESS && !status_value.ends_with(":Success") {
+        return Err(SamlError::Status(status_value.to_owned()));
+    }
+
+    // 4. Destination (if the IdP set one) must be our ACS.
+    if let Some(dest) = root.attribute("Destination") {
+        if !urls_equal(dest, &sp.acs_url) {
+            return Err(SamlError::DestinationMismatch);
+        }
+    }
+
+    // 5. Exactly one (unencrypted) Assertion.
+    if root
+        .descendants()
+        .any(|n| n.is_element() && n.tag_name().name() == "EncryptedAssertion")
+    {
+        return Err(SamlError::EncryptedAssertionUnsupported);
+    }
+    let assertions: Vec<Node<'_, '_>> = root
+        .children()
+        .filter(|c| c.is_element() && c.tag_name().name() == "Assertion")
+        .collect();
+    if assertions.len() != 1 {
+        return Err(SamlError::AssertionCount(assertions.len()));
+    }
+    let assertion = assertions[0];
+    let assertion_id = assertion
+        .attribute("ID")
+        .map(str::to_owned)
+        .ok_or_else(|| SamlError::MissingElement("Assertion/@ID".into()))?;
+
+    // 6. The signature must actually cover the assertion we're about to trust:
+    //    either the assertion itself, the enclosing response, or the whole
+    //    document. (bergshamra's strict_verification already constrains where
+    //    the signed element may sit; this ties it to *our* assertion.)
+    let covers_assertion = verified_uris.iter().any(|u| {
+        u.is_empty()
+            || u == &format!("#{assertion_id}")
+            || response_id
+                .as_ref()
+                .is_some_and(|rid| u == &format!("#{rid}"))
+    });
+    if !covers_assertion {
+        return Err(SamlError::SignatureScope);
+    }
+
+    // 7. Issuer must be the configured IdP.
+    let issuer = first_child(assertion, "Issuer")
+        .map(text_of)
+        .unwrap_or_default();
+    if !idp.entity_id.is_empty() && issuer != idp.entity_id {
+        return Err(SamlError::IssuerMismatch);
+    }
+
+    // 8. Subject → NameID + SubjectConfirmationData time/recipient checks.
+    let subject = first_child(assertion, "Subject")
+        .ok_or_else(|| SamlError::MissingElement("Subject".into()))?;
+    let name_id = first_child(subject, "NameID")
+        .map(text_of)
+        .filter(|s| !s.is_empty())
+        .ok_or_else(|| SamlError::MissingElement("NameID".into()))?;
+    if let Some(scd) = subject
+        .descendants()
+        .find(|n| n.is_element() && n.tag_name().name() == "SubjectConfirmationData")
+    {
+        if let Some(recipient) = scd.attribute("Recipient") {
+            if !urls_equal(recipient, &sp.acs_url) {
+                return Err(SamlError::DestinationMismatch);
+            }
+        }
+        if let Some(noa) = scd.attribute("NotOnOrAfter") {
+            let noa = parse_instant(noa)?;
+            if now >= noa + clock_skew {
+                return Err(SamlError::TimeBounds);
+            }
+        }
+    }
+
+    // 9. Conditions: time window + audience.
+    let conditions = first_child(assertion, "Conditions");
+    if let Some(cond) = conditions {
+        if let Some(nb) = cond.attribute("NotBefore") {
+            let nb = parse_instant(nb)?;
+            if now < nb - clock_skew {
+                return Err(SamlError::TimeBounds);
+            }
+        }
+    }
+    let assertion_expiry = conditions
+        .and_then(|c| c.attribute("NotOnOrAfter"))
+        .map(parse_instant)
+        .transpose()?
+        .ok_or_else(|| SamlError::MissingElement("Conditions/@NotOnOrAfter".into()))?;
+    if now >= assertion_expiry + clock_skew {
+        return Err(SamlError::TimeBounds);
+    }
+
+    let audience_ok = conditions.is_some_and(|c| {
+        c.descendants()
+            .filter(|n| n.is_element() && n.tag_name().name() == "Audience")
+            .any(|a| text_of(a) == sp.entity_id)
+    });
+    if !audience_ok {
+        return Err(SamlError::AudienceMismatch);
+    }
+
+    // 10. Optional: SessionIndex + display-name attribute.
+    let session_index = assertion
+        .descendants()
+        .find(|n| n.is_element() && n.tag_name().name() == "AuthnStatement")
+        .and_then(|a| a.attribute("SessionIndex"))
+        .map(str::to_owned);
+
+    let display_name = extract_display_name(assertion);
+
+    Ok(VerifiedResponse {
+        principal: VerifiedPrincipal {
+            email: name_id.clone(),
+            name_id,
+            display_name,
+        },
+        in_response_to,
+        assertion_id,
+        assertion_expiry,
+        session_index,
+    })
+}
+
+/// Verify the document's XML-DSig against each pinned IdP cert in turn
+/// (handles key rotation), returning the verified `<Reference>` URIs.
+fn verify_signature(xml: &str, certs_der: &[Vec<u8>]) -> Result<Vec<String>, SamlError> {
+    let mut last_err = String::from("no signing certificate matched");
+    for der in certs_der {
+        let key = match bergshamra::keys::loader::load_x509_cert_der(der) {
+            Ok(k) => k,
+            Err(e) => {
+                last_err = e.to_string();
+                continue;
+            }
+        };
+        let mut km = bergshamra::keys::KeysManager::new();
+        km.add_key(key);
+        // trusted_keys_only: only ever trust the pinned IdP key, never an
+        // inline KeyInfo cert. strict_verification: XSW positional defense.
+        let ctx = bergshamra::DsigContext::new(km)
+            .with_trusted_keys_only(true)
+            .with_strict_verification(true);
+        match bergshamra::verify(&ctx, xml) {
+            Ok(bergshamra::VerifyResult::Valid { references, .. }) => {
+                return Ok(references.into_iter().map(|r| r.uri).collect());
+            }
+            Ok(bergshamra::VerifyResult::Invalid { reason }) => last_err = reason,
+            Err(e) => last_err = e.to_string(),
+        }
+    }
+    Err(SamlError::Signature(last_err))
+}
+
+/// Pull a display name from the assertion's attribute statement, trying the
+/// common attribute names IdPs use (FleetDM checks the same set).
+fn extract_display_name(assertion: Node<'_, '_>) -> Option<String> {
+    const WANTED: &[&str] = &[
+        "name",
+        "displayname",
+        "cn",
+        "urn:oid:2.5.4.3",
+        "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name",
+    ];
+    for attr in assertion
+        .descendants()
+        .filter(|n| n.is_element() && n.tag_name().name() == "Attribute")
+    {
+        let key = attr
+            .attribute("Name")
+            .or_else(|| attr.attribute("FriendlyName"))
+            .unwrap_or("")
+            .to_ascii_lowercase();
+        if WANTED.contains(&key.as_str()) {
+            if let Some(val) = attr
+                .descendants()
+                .find(|n| n.is_element() && n.tag_name().name() == "AttributeValue")
+            {
+                let v = text_of(val);
+                if !v.is_empty() {
+                    return Some(v);
+                }
+            }
+        }
+    }
+    None
+}
+
+fn first_child<'a, 'i>(n: Node<'a, 'i>, local: &str) -> Option<Node<'a, 'i>> {
+    n.children()
+        .find(|c| c.is_element() && c.tag_name().name() == local)
+}
+
+fn text_of(n: Node<'_, '_>) -> String {
+    n.children()
+        .filter(Node::is_text)
+        .filter_map(|c| c.text())
+        .collect::<String>()
+        .trim()
+        .to_owned()
+}
+
+/// Parse an `xs:dateTime` (e.g. `2026-05-31T12:00:00.000Z`).
+fn parse_instant(s: &str) -> Result<OffsetDateTime, SamlError> {
+    OffsetDateTime::parse(s.trim(), &Rfc3339).map_err(|e| SamlError::Timestamp(format!("{s}: {e}")))
+}
+
+/// Compare two URLs for SAML endpoint-matching purposes: exact, or differing
+/// only by a single trailing slash.
+fn urls_equal(a: &str, b: &str) -> bool {
+    a == b || a.trim_end_matches('/') == b.trim_end_matches('/')
+}

crates/core/src/saml/tests.rs

@@ -0,0 +1,287 @@
+//! End-to-end SAML SP tests.
+//!
+//! We mint a throwaway self-signed cert/key with `rcgen`, sign a SAML Response
+//! template with `bergshamra::sign` (the same engine that verifies it), and
+//! drive [`response::consume`] through the accept path and every reject path.
+//! This proves both the signature wiring and the SP-semantic checks.
+
+use time::format_description::well_known::Rfc3339;
+use time::{Duration, OffsetDateTime};
+
+use super::metadata::IdpMetadata;
+use super::{response, SamlError, SpParams};
+
+const SP_ENTITY: &str = "https://pxe.example.com";
+const ACS: &str = "https://pxe.example.com/api/sso/acs";
+const IDP_ENTITY: &str = "https://idp.example.com/realms/fleet";
+const EMAIL: &str = "[email protected]";
+
+struct TestIdp {
+    cert_der: Vec<u8>,
+    key_pem: String,
+}
+
+fn test_idp() -> TestIdp {
+    let ck = rcgen::generate_simple_self_signed(vec!["idp.example.com".to_string()]).unwrap();
+    TestIdp {
+        cert_der: ck.cert.der().as_ref().to_vec(),
+        key_pem: ck.key_pair.serialize_pem(),
+    }
+}
+
+fn fmt(t: OffsetDateTime) -> String {
+    t.replace_nanosecond(0).unwrap().format(&Rfc3339).unwrap()
+}
+
+/// Knobs for building a response template — defaults are a valid response.
+struct Resp {
+    issuer: String,
+    audience: String,
+    status: String,
+    not_before: OffsetDateTime,
+    not_on_or_after: OffsetDateTime,
+    in_response_to: Option<String>,
+    recipient: String,
+}
+
+impl Default for Resp {
+    fn default() -> Self {
+        let now = OffsetDateTime::now_utc();
+        Self {
+            issuer: IDP_ENTITY.into(),
+            audience: SP_ENTITY.into(),
+            status: "urn:oasis:names:tc:SAML:2.0:status:Success".into(),
+            not_before: now - Duration::minutes(5),
+            not_on_or_after: now + Duration::hours(1),
+            in_response_to: Some("_req-abc".into()),
+            recipient: ACS.into(),
+        }
+    }
+}
+
+impl Resp {
+    /// The unsigned template (a `<ds:Signature>` with empty values).
+    fn template(&self) -> String {
+        let now = fmt(OffsetDateTime::now_utc());
+        let irt = self
+            .in_response_to
+            .as_ref()
+            .map(|v| format!(r#" InResponseTo="{v}""#))
+            .unwrap_or_default();
+        format!(
+            r##"<samlp:Response xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol" xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion" ID="_resp1" Version="2.0" IssueInstant="{now}" Destination="{ACS}"{irt}>
+  <saml:Issuer>{issuer}</saml:Issuer>
+  <samlp:Status><samlp:StatusCode Value="{status}"/></samlp:Status>
+  <saml:Assertion ID="_assertion1" Version="2.0" IssueInstant="{now}">
+    <saml:Issuer>{issuer}</saml:Issuer>
+    <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
+      <ds:SignedInfo>
+        <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
+        <ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256"/>
+        <ds:Reference URI="#_assertion1">
+          <ds:Transforms>
+            <ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/>
+            <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
+          </ds:Transforms>
+          <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
+          <ds:DigestValue></ds:DigestValue>
+        </ds:Reference>
+      </ds:SignedInfo>
+      <ds:SignatureValue></ds:SignatureValue>
+    </ds:Signature>
+    <saml:Subject>
+      <saml:NameID Format="urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress">{EMAIL}</saml:NameID>
+      <saml:SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:bearer">
+        <saml:SubjectConfirmationData Recipient="{recipient}" NotOnOrAfter="{noa}"{irt}/>
+      </saml:SubjectConfirmation>
+    </saml:Subject>
+    <saml:Conditions NotBefore="{nb}" NotOnOrAfter="{noa}">
+      <saml:AudienceRestriction><saml:Audience>{audience}</saml:Audience></saml:AudienceRestriction>
+    </saml:Conditions>
+    <saml:AuthnStatement AuthnInstant="{now}" SessionIndex="sess-123">
+      <saml:AuthnContext><saml:AuthnContextClassRef>urn:oasis:names:tc:SAML:2.0:ac:classes:Password</saml:AuthnContextClassRef></saml:AuthnContext>
+    </saml:AuthnStatement>
+    <saml:AttributeStatement>
+      <saml:Attribute Name="displayName"><saml:AttributeValue>Miles Ward</saml:AttributeValue></saml:Attribute>
+    </saml:AttributeStatement>
+  </saml:Assertion>
+</samlp:Response>"##,
+            issuer = self.issuer,
+            status = self.status,
+            audience = self.audience,
+            recipient = self.recipient,
+            nb = fmt(self.not_before),
+            noa = fmt(self.not_on_or_after),
+        )
+    }
+}
+
+fn sign(template: &str, key_pem: &str) -> String {
+    let key = bergshamra::keys::loader::load_pem_auto(key_pem.as_bytes(), None)
+        .expect("load test signing key");
+    let mut km = bergshamra::keys::KeysManager::new();
+    km.add_key(key);
+    let ctx = bergshamra::DsigContext::new(km);
+    bergshamra::sign(&ctx, template).expect("sign test response")
+}
+
+fn sp() -> SpParams {
+    SpParams {
+        entity_id: SP_ENTITY.into(),
+        acs_url: ACS.into(),
+    }
+}
+
+fn idp(cert_der: Vec<u8>) -> IdpMetadata {
+    IdpMetadata {
+        entity_id: IDP_ENTITY.into(),
+        sso_redirect_url: None,
+        sso_post_url: None,
+        signing_certs_der: vec![cert_der],
+    }
+}
+
+fn consume(xml: &str, cert_der: Vec<u8>) -> Result<response::VerifiedResponse, SamlError> {
+    response::consume(
+        xml,
+        &sp(),
+        &idp(cert_der),
+        OffsetDateTime::now_utc(),
+        Duration::seconds(60),
+    )
+}
+
+#[test]
+fn good_response_yields_principal() {
+    let t = test_idp();
+    let signed = sign(&Resp::default().template(), &t.key_pem);
+    let out = consume(&signed, t.cert_der).expect("valid response should verify");
+    assert_eq!(out.principal.email, EMAIL);
+    assert_eq!(out.principal.name_id, EMAIL);
+    assert_eq!(out.principal.display_name.as_deref(), Some("Miles Ward"));
+    assert_eq!(out.in_response_to.as_deref(), Some("_req-abc"));
+    assert_eq!(out.assertion_id, "_assertion1");
+    assert_eq!(out.session_index.as_deref(), Some("sess-123"));
+}
+
+#[test]
+fn tampered_assertion_is_rejected() {
+    let t = test_idp();
+    let signed = sign(&Resp::default().template(), &t.key_pem);
+    // Flip the subject email after signing — breaks the digest.
+    let tampered = signed.replace(EMAIL, "[email protected]");
+    assert_ne!(signed, tampered);
+    assert!(matches!(
+        consume(&tampered, t.cert_der),
+        Err(SamlError::Signature(_) | SamlError::SignatureScope)
+    ));
+}
+
+#[test]
+fn unsigned_response_is_rejected() {
+    let t = test_idp();
+    // Feed the *unsigned* template (empty SignatureValue) straight in.
+    let unsigned = Resp::default().template();
+    assert!(matches!(
+        consume(&unsigned, t.cert_der),
+        Err(SamlError::Signature(_))
+    ));
+}
+
+#[test]
+fn wrong_signing_key_is_rejected() {
+    let signer = test_idp();
+    let other = test_idp(); // different keypair pinned as the "IdP" cert
+    let signed = sign(&Resp::default().template(), &signer.key_pem);
+    assert!(matches!(
+        consume(&signed, other.cert_der),
+        Err(SamlError::Signature(_))
+    ));
+}
+
+#[test]
+fn wrong_audience_is_rejected() {
+    let t = test_idp();
+    let r = Resp {
+        audience: "https://someone-else.example".into(),
+        ..Resp::default()
+    };
+    let signed = sign(&r.template(), &t.key_pem);
+    assert!(matches!(
+        consume(&signed, t.cert_der),
+        Err(SamlError::AudienceMismatch)
+    ));
+}
+
+#[test]
+fn expired_assertion_is_rejected() {
+    let t = test_idp();
+    let now = OffsetDateTime::now_utc();
+    let r = Resp {
+        not_before: now - Duration::hours(2),
+        not_on_or_after: now - Duration::hours(1),
+        ..Resp::default()
+    };
+    let signed = sign(&r.template(), &t.key_pem);
+    assert!(matches!(
+        consume(&signed, t.cert_der),
+        Err(SamlError::TimeBounds)
+    ));
+}
+
+#[test]
+fn future_assertion_is_rejected() {
+    let t = test_idp();
+    let now = OffsetDateTime::now_utc();
+    let r = Resp {
+        not_before: now + Duration::hours(1),
+        not_on_or_after: now + Duration::hours(2),
+        ..Resp::default()
+    };
+    let signed = sign(&r.template(), &t.key_pem);
+    assert!(matches!(
+        consume(&signed, t.cert_der),
+        Err(SamlError::TimeBounds)
+    ));
+}
+
+#[test]
+fn wrong_issuer_is_rejected() {
+    let t = test_idp();
+    let r = Resp {
+        issuer: "https://evil-idp.example".into(),
+        ..Resp::default()
+    };
+    let signed = sign(&r.template(), &t.key_pem);
+    assert!(matches!(
+        consume(&signed, t.cert_der),
+        Err(SamlError::IssuerMismatch)
+    ));
+}
+
+#[test]
+fn non_success_status_is_rejected() {
+    let t = test_idp();
+    let r = Resp {
+        status: "urn:oasis:names:tc:SAML:2.0:status:Requester".into(),
+        ..Resp::default()
+    };
+    let signed = sign(&r.template(), &t.key_pem);
+    assert!(matches!(
+        consume(&signed, t.cert_der),
+        Err(SamlError::Status(_))
+    ));
+}
+
+#[test]
+fn idp_initiated_has_no_in_response_to() {
+    // No InResponseTo => the HTTP layer must gate it behind allow_idp_initiated.
+    let t = test_idp();
+    let r = Resp {
+        in_response_to: None,
+        ..Resp::default()
+    };
+    let signed = sign(&r.template(), &t.key_pem);
+    let out = consume(&signed, t.cert_der).expect("unsolicited but otherwise valid");
+    assert!(out.in_response_to.is_none());
+}

crates/core/src/sso.rs

@@ -1,16 +1,17 @@
-//! SAML SSO configuration — FleetDM-shaped, storage-only for v0.4.5.
+//! SAML SSO configuration — FleetDM-shaped.
 //!
 //! The operator pastes their IdP's metadata XML (or its URL) and a
-//! human-readable label; v0.4.5 just persists it. The actual SAML
-//! response-validation / JIT-provisioning flow lands in a later release
-//! — for now we cover the "configurable" half so an operator can teach
-//! OpenPXE about their IdP today and flip the switch on next upgrade.
+//! human-readable label. As of v0.5.1 the SAML login flow is wired
+//! end-to-end (see [`crate::saml`]): SP-initiated AuthnRequest, the ACS
+//! endpoint, pure-Rust signature verification, and operator-session
+//! minting. This module owns only the persisted *configuration*.
 //!
 //! Shape borrowed from <https://github.com/fleetdm/fleet>'s app-config
-//! SSO block, minus the user-RBAC fields (OpenPXE is single-tier: you
-//! have access or you don't). Entity ID is omitted from the operator
-//! UI per the v0.4.5 brief — it defaults to the advertised public base
-//! URL when SAML wiring lands, which is what most IdPs expect anyway.
+//! SSO block, minus the user-RBAC fields (OpenPXE is single-tier: any
+//! IdP-authenticated user the SP cryptographically verifies gets an
+//! operator session; there is no per-user role table). Entity ID is
+//! exposed (FleetDM-style) but defaults to the advertised public base
+//! URL when blank, which is what most IdPs expect anyway.
 
 use parking_lot::RwLock;
 use serde::{Deserialize, Serialize};
@@ -47,6 +48,18 @@ pub struct SsoConfig {
     /// future SAML flow; not validated here beyond a basic length cap.
     #[serde(default)]
     pub metadata_url: String,
+    /// SP Entity ID advertised to the IdP — mirrors FleetDM's "Entity ID".
+    /// Must exactly match the SP/Relying-Party entry configured on the IdP.
+    /// Empty falls back to the advertised public base URL at runtime, which
+    /// is what most IdPs expect. Length-capped at [`MAX_URL_LEN`].
+    #[serde(default)]
+    pub entity_id: String,
+    /// Allow IdP-initiated login — an unsolicited `<Response>` POSTed to the
+    /// ACS with no `InResponseTo`. Mirrors FleetDM's "Allow SSO login
+    /// initiated by identity provider". Default off; SP-initiated (the
+    /// "Sign in with X" button) is always allowed regardless.
+    #[serde(default)]
+    pub allow_idp_initiated: bool,
 }
 
 impl SsoConfig {
@@ -56,8 +69,7 @@ impl SsoConfig {
     /// surface a yellow "configured but not live yet" hint.
     #[must_use]
     pub fn is_usable(&self) -> bool {
-        self.enabled
-            && (!self.metadata.trim().is_empty() || !self.metadata_url.trim().is_empty())
+        self.enabled && (!self.metadata.trim().is_empty() || !self.metadata_url.trim().is_empty())
     }
 }
 
@@ -108,6 +120,12 @@ impl SsoStore {
         cfg.idp_logo_url = cfg.idp_logo_url.trim().to_string();
         cfg.metadata = cfg.metadata.trim().to_string();
         cfg.metadata_url = cfg.metadata_url.trim().to_string();
+        cfg.entity_id = cfg.entity_id.trim().to_string();
+        if cfg.entity_id.len() > MAX_URL_LEN {
+            return Err(Error::Invalid(format!(
+                "entity_id exceeds {MAX_URL_LEN}-char cap"
+            )));
+        }
         if cfg.metadata.len() > MAX_METADATA_BYTES {
             return Err(Error::Invalid(format!(
                 "metadata XML exceeds {MAX_METADATA_BYTES}-byte cap"
@@ -217,6 +235,8 @@ mod tests {
             metadata: String::new(),
             metadata_url: "https://idp.example.com/metadata".into(),
             idp_logo_url: String::new(),
+            entity_id: String::new(),
+            allow_idp_initiated: false,
         })
         .unwrap();
         drop(s);
@@ -239,6 +259,8 @@ mod tests {
             metadata: xml.into(),
             metadata_url: String::new(),
             idp_logo_url: String::new(),
+            entity_id: String::new(),
+            allow_idp_initiated: false,
         })
         .unwrap();
         assert!(s.snapshot().is_usable());
@@ -254,6 +276,8 @@ mod tests {
             metadata: String::new(),
             metadata_url: String::new(),
             idp_logo_url: String::new(),
+            entity_id: String::new(),
+            allow_idp_initiated: false,
         });
         assert!(matches!(r, Err(Error::Invalid(_))));
         // …and a disabled blank config is fine.
@@ -270,6 +294,8 @@ mod tests {
             metadata: String::new(),
             metadata_url: "ftp://idp.example.com/metadata".into(),
             idp_logo_url: String::new(),
+            entity_id: String::new(),
+            allow_idp_initiated: false,
         });
         assert!(matches!(r, Err(Error::Invalid(_))));
     }
@@ -287,6 +313,8 @@ mod tests {
             metadata: String::new(),
             metadata_url: String::new(),
             idp_logo_url: "data:image/png;base64,...".into(),
+            entity_id: String::new(),
+            allow_idp_initiated: false,
         });
         assert!(matches!(r, Err(Error::Invalid(_))));
         // Real HTTPS URL is fine.
@@ -296,9 +324,51 @@ mod tests {
             metadata: String::new(),
             metadata_url: String::new(),
             idp_logo_url: "https://idp.example.com/logo.png".into(),
+            entity_id: String::new(),
+            allow_idp_initiated: false,
         })
         .unwrap();
-        assert_eq!(s.snapshot().idp_logo_url, "https://idp.example.com/logo.png");
+        assert_eq!(
+            s.snapshot().idp_logo_url,
+            "https://idp.example.com/logo.png"
+        );
+    }
+
+    #[test]
+    fn entity_id_and_idp_initiated_round_trip() {
+        // v0.5.1: SP Entity ID + IdP-initiated toggle persist across reload.
+        let dir = tempdir().unwrap();
+        let s = SsoStore::load_or_default(dir.path());
+        s.replace(SsoConfig {
+            enabled: true,
+            idp_name: "Keycloak".into(),
+            metadata: String::new(),
+            metadata_url: "https://idp.example.com/metadata".into(),
+            idp_logo_url: String::new(),
+            entity_id: "https://pxe.example.com".into(),
+            allow_idp_initiated: true,
+        })
+        .unwrap();
+        drop(s);
+        let cfg = SsoStore::load_or_default(dir.path()).snapshot();
+        assert_eq!(cfg.entity_id, "https://pxe.example.com");
+        assert!(cfg.allow_idp_initiated);
+    }
+
+    #[test]
+    fn entity_id_cap_enforced() {
+        let dir = tempdir().unwrap();
+        let s = SsoStore::load_or_default(dir.path());
+        let r = s.replace(SsoConfig {
+            enabled: false,
+            idp_name: String::new(),
+            metadata: String::new(),
+            metadata_url: String::new(),
+            idp_logo_url: String::new(),
+            entity_id: "x".repeat(MAX_URL_LEN + 1),
+            allow_idp_initiated: false,
+        });
+        assert!(matches!(r, Err(Error::Invalid(_))));
     }
 
     #[test]
@@ -312,6 +382,8 @@ mod tests {
             metadata: oversize,
             metadata_url: String::new(),
             idp_logo_url: String::new(),
+            entity_id: String::new(),
+            allow_idp_initiated: false,
         });
         assert!(matches!(r, Err(Error::Invalid(_))));
     }

crates/http-api/Cargo.toml

@@ -44,6 +44,8 @@ parking_lot.workspace = true
 # OpenSSL-free.
 reqwest.workspace = true
 lettre.workspace = true
+# v0.5.1: decode the base64 SAMLResponse at the ACS endpoint.
+base64.workspace = true
 
 [dev-dependencies]
 tokio = { workspace = true, features = ["macros", "rt", "rt-multi-thread", "time"] }
@@ -54,3 +56,8 @@ time = { workspace = true }
 # v0.4.61: integration tests need to generate real PNG bytes for the
 # `/branding/pxe-logo` compositor; hand-rolled CRCs are too fragile.
 image = { version = "0.25", default-features = false, features = ["png"] }
+# v0.5.1: the SAML ACS integration tests mint a throwaway IdP keypair
+# (rcgen) and sign a SAMLResponse with bergshamra so the happy-path,
+# replay, and IdP-initiated-gating flows exercise real signatures.
+rcgen = "0.13"
+bergshamra = { workspace = true }

crates/http-api/src/app.rs

@@ -116,14 +116,16 @@ pub fn build_router(state: AppState) -> Router {
         .route("/api/login", post(auth_api::api_login))
         .route("/api/logout", post(auth_api::api_logout))
         .route("/api/me", get(auth_api::api_me))
-        .route(
-            "/api/me/credentials",
-            put(auth_api::api_update_credentials),
-        )
-        // v0.4.5: SAML SSO configuration (FleetDM-shaped, storage-only).
-        // The actual sign-in flow lands in a later release; this just
-        // gives operators a place to paste their IdP metadata today.
+        .route("/api/me/credentials", put(auth_api::api_update_credentials))
+        // SAML SSO configuration (FleetDM-shaped). Gated behind auth — the
+        // operator pastes their IdP metadata, Entity ID, and toggles here.
         .route("/api/sso", get(api_sso_get).put(api_sso_put))
+        // v0.5.1: SAML SP login flow (pre-auth — see the require_auth
+        // allowlist). /login redirects to the IdP, /acs consumes the signed
+        // response + mints a session, /metadata serves our SP descriptor.
+        .route("/api/sso/login", get(crate::saml_routes::sso_login))
+        .route("/api/sso/acs", post(crate::saml_routes::sso_acs))
+        .route("/api/sso/metadata", get(crate::saml_routes::sso_metadata))
         .route("/api/clients", get(api_list_clients))
         .route("/api/status", get(api_status))
         .route("/api/settings", get(api_get_settings).put(api_put_settings))
@@ -138,13 +140,19 @@ pub fn build_router(state: AppState) -> Router {
         // modules (Unraid), and no container-side configuration could
         // load a host kernel module. `smbclient` speaks SMB over a
         // plain TCP socket in userspace, works in every container.
-        .route("/api/smb-shares", get(api_smb_shares_list).post(api_smb_shares_add))
+        .route(
+            "/api/smb-shares",
+            get(api_smb_shares_list).post(api_smb_shares_add),
+        )
         .route("/api/smb-shares/:id", delete(api_smb_shares_remove))
         .route("/api/smb-shares/:id/scan", post(api_smb_shares_scan))
         // v0.4.67: NFSv3 share manager (pure-Rust in-process client).
         // Ships alongside SMB. Routes are parallel so the UI can
         // reuse the same form/error/hint rendering for both.
-        .route("/api/nfs-shares", get(api_nfs_shares_list).post(api_nfs_shares_add))
+        .route(
+            "/api/nfs-shares",
+            get(api_nfs_shares_list).post(api_nfs_shares_add),
+        )
         .route("/api/nfs-shares/:id", delete(api_nfs_shares_remove))
         .route("/api/nfs-shares/:id/scan", post(api_nfs_shares_scan))
         // Phase 4: Network info (read-only) + DNS edit.
@@ -204,9 +212,7 @@ async fn api_sso_get(State(state): State<AppState>) -> Json<SsoConfig> {
 async fn api_sso_put(State(state): State<AppState>, Json(body): Json<SsoConfig>) -> Response {
     match state.sso.replace(body) {
         Ok(cfg) => (StatusCode::OK, Json(cfg)).into_response(),
-        Err(Error::Invalid(msg)) => {
-            (StatusCode::BAD_REQUEST, msg).into_response()
-        }
+        Err(Error::Invalid(msg)) => (StatusCode::BAD_REQUEST, msg).into_response(),
         Err(e) => (StatusCode::INTERNAL_SERVER_ERROR, format!("{e}")).into_response(),
     }
 }
@@ -251,8 +257,7 @@ async fn index(State(state): State<AppState>) -> Response {
 /// with the `?v=<version>` query string in index.html, the practical
 /// upper bound on caching across an upgrade is "until the operator
 /// reloads".
-const ASSET_CACHE_CONTROL: HeaderValue =
-    HeaderValue::from_static("no-cache, must-revalidate");
+const ASSET_CACHE_CONTROL: HeaderValue = HeaderValue::from_static("no-cache, must-revalidate");
 
 async fn ui_js() -> Response {
     (
@@ -347,9 +352,7 @@ async fn ui_pxe_logo(State(state): State<AppState>) -> Response {
     // iPXE/our compositor can consume. SVG (or a missing/unreadable
     // file) yields `None`, which composes the default background.
     let raster: Option<Vec<u8>> = match (state.branding.logo_path(), state.branding.logo_mime()) {
-        (Some(path), Some(mime)) if mime != "image/svg+xml" => {
-            tokio::fs::read(&path).await.ok()
-        }
+        (Some(path), Some(mime)) if mime != "image/svg+xml" => tokio::fs::read(&path).await.ok(),
         _ => None,
     };
 
@@ -693,9 +696,7 @@ async fn iso_raw(
             };
             match stream_file_range(&path, headers.get(header::RANGE)).await {
                 Ok(r) => r,
-                Err(e) => {
-                    (StatusCode::INTERNAL_SERVER_ERROR, format!("{e}")).into_response()
-                }
+                Err(e) => (StatusCode::INTERNAL_SERVER_ERROR, format!("{e}")).into_response(),
             }
         }
         IsoSource::Smb {
@@ -710,7 +711,10 @@ async fn iso_raw(
             if headers.get(header::RANGE).is_some() {
                 return Response::builder()
                     .status(StatusCode::RANGE_NOT_SATISFIABLE)
-                    .header(header::CONTENT_RANGE, format!("bytes */{}", meta.size_bytes))
+                    .header(
+                        header::CONTENT_RANGE,
+                        format!("bytes */{}", meta.size_bytes),
+                    )
                     .body(Body::empty())
                     .unwrap();
             }
@@ -1048,10 +1052,7 @@ async fn api_storage_disk(State(state): State<AppState>) -> Json<serde_json::Val
 
 // ─── Branding (custom logo) ───────────────────────────────────────────────
 
-async fn api_branding_upload(
-    State(state): State<AppState>,
-    mut multipart: Multipart,
-) -> Response {
+async fn api_branding_upload(State(state): State<AppState>, mut multipart: Multipart) -> Response {
     while let Ok(Some(field)) = multipart.next_field().await {
         let name = field.name().unwrap_or("").to_string();
         if name != "file" && name != "logo" {
@@ -1072,9 +1073,7 @@ async fn api_branding_upload(
         // hitting disk. Logos are tiny by definition.
         let bytes = match field.bytes().await {
             Ok(b) => b,
-            Err(e) => {
-                return (StatusCode::BAD_REQUEST, format!("read body: {e}")).into_response()
-            }
+            Err(e) => return (StatusCode::BAD_REQUEST, format!("read body: {e}")).into_response(),
         };
         if bytes.len() > MAX_LOGO_BYTES {
             return (
@@ -1102,9 +1101,7 @@ async fn api_branding_upload(
                 )
                     .into_response()
             }
-            Err(e) => {
-                return (StatusCode::INTERNAL_SERVER_ERROR, format!("{e}")).into_response()
-            }
+            Err(e) => return (StatusCode::INTERNAL_SERVER_ERROR, format!("{e}")).into_response(),
         }
     }
     (StatusCode::BAD_REQUEST, "no 'file' part").into_response()
@@ -2064,10 +2061,7 @@ async fn api_hosts_remove(
 /// common "same VLAN as OpenPXE" case with zero network config. We only
 /// wake MACs that are actually bound — keeps this from being an open
 /// "spray packets at any MAC" endpoint.
-async fn api_hosts_wol(
-    State(state): State<AppState>,
-    AxumPath(mac): AxumPath<String>,
-) -> Response {
+async fn api_hosts_wol(State(state): State<AppState>, AxumPath(mac): AxumPath<String>) -> Response {
     if state.hosts.lookup(&mac).is_none() {
         return (
             StatusCode::NOT_FOUND,
@@ -2097,8 +2091,7 @@ async fn api_hosts_wol(
     // The send is a blocking std UDP call; push it off the async
     // executor.
     let mac_owned = mac.clone();
-    let result =
-        tokio::task::spawn_blocking(move || wol::wake(&mac_owned, &broadcasts)).await;
+    let result = tokio::task::spawn_blocking(move || wol::wake(&mac_owned, &broadcasts)).await;
     match result {
         Ok(Ok(n)) => {
             // Fire-and-forget notification — nice "someone woke a box"
@@ -2111,7 +2104,11 @@ async fn api_hosts_wol(
             Json(json!({ "ok": true, "broadcasts": n })).into_response()
         }
         Ok(Err(e)) => (StatusCode::BAD_REQUEST, format!("{e}")).into_response(),
-        Err(e) => (StatusCode::INTERNAL_SERVER_ERROR, format!("wol task failed: {e}")).into_response(),
+        Err(e) => (
+            StatusCode::INTERNAL_SERVER_ERROR,
+            format!("wol task failed: {e}"),
+        )
+            .into_response(),
     }
 }
 
@@ -2122,10 +2119,7 @@ async fn api_notify_get(State(state): State<AppState>) -> Json<NotifyConfig> {
     Json(state.notify.snapshot().redacted())
 }
 
-async fn api_notify_put(
-    State(state): State<AppState>,
-    Json(cfg): Json<NotifyConfig>,
-) -> Response {
+async fn api_notify_put(State(state): State<AppState>, Json(cfg): Json<NotifyConfig>) -> Response {
     match state.notify.replace(cfg) {
         Ok(saved) => (StatusCode::OK, Json(saved.redacted())).into_response(),
         Err(e) => (StatusCode::BAD_REQUEST, format!("{e}")).into_response(),
@@ -2191,10 +2185,7 @@ async fn api_updates_check() -> Response {
                 .and_then(|v| v.as_str())
                 .unwrap_or("")
                 .to_string();
-            let update_available = version_is_newer(
-                latest_tag.trim_start_matches('v'),
-                current,
-            );
+            let update_available = version_is_newer(latest_tag.trim_start_matches('v'), current);
             Json(json!({
                 "current": current,
                 "latest": latest_tag,
@@ -2241,7 +2232,11 @@ fn gitea_releases_api_url() -> Option<String> {
 fn version_is_newer(latest: &str, current: &str) -> bool {
     fn parts(v: &str) -> Vec<u64> {
         v.split('.')
-            .map(|p| p.chars().take_while(char::is_ascii_digit).collect::<String>())
+            .map(|p| {
+                p.chars()
+                    .take_while(char::is_ascii_digit)
+                    .collect::<String>()
+            })
             .map(|s| s.parse::<u64>().unwrap_or(0))
             .collect()
     }

crates/http-api/src/auth.rs

@@ -140,9 +140,16 @@ fn cookie_attrs(value: &str, max_age: Option<i64>) -> String {
     // never overflow i64, but clippy's `cast_possible_wrap` lint wants
     // us to be explicit. `cast_signed` is the documented form.
     let lifetime = max_age.unwrap_or_else(|| SESSION_TTL.as_secs().cast_signed());
-    format!(
-        "{SESSION_COOKIE}={value}; Path=/; HttpOnly; SameSite=Lax; Max-Age={lifetime}"
-    )
+    format!("{SESSION_COOKIE}={value}; Path=/; HttpOnly; SameSite=Lax; Max-Age={lifetime}")
+}
+
+/// Build the `Set-Cookie` header value that establishes a fresh operator
+/// session with the default 24h TTL. Exposed so the SAML ACS handler can
+/// attach an operator session to its post-login redirect, exactly as the
+/// Forms-login path does via [`login_response`].
+#[must_use]
+pub fn session_cookie(session: &str) -> String {
+    cookie_attrs(session, None)
 }
 
 fn parse_cookie(headers: &axum::http::HeaderMap) -> Option<String> {
@@ -169,9 +176,18 @@ fn is_public_path(path: &str) -> bool {
         return true;
     }
     // Auth surface and iPXE long-poll endpoints (no cookie available).
+    // The SAML SP endpoints are pre-auth by nature — the operator hasn't a
+    // session yet when they start (or arrive from) the IdP. `/api/sso`
+    // (the config GET/PUT, no trailing slash) stays gated.
     matches!(
         path,
-        "/api/setup" | "/api/login" | "/api/logout" | "/api/me"
+        "/api/setup"
+            | "/api/login"
+            | "/api/logout"
+            | "/api/me"
+            | "/api/sso/login"
+            | "/api/sso/acs"
+            | "/api/sso/metadata"
     ) || path.starts_with("/api/queue/join")
         || path.starts_with("/api/queue/poll/")
 }
@@ -222,10 +238,7 @@ pub struct SetupBody {
 /// guards against a leaked WebUI being re-bootstrapped by an attacker
 /// who's seen the deployment URL. After bootstrap, the new session
 /// cookie is set so the operator goes straight to the dashboard.
-pub async fn api_setup(
-    State(state): State<AppState>,
-    Json(body): Json<SetupBody>,
-) -> Response {
+pub async fn api_setup(State(state): State<AppState>, Json(body): Json<SetupBody>) -> Response {
     if state.admin.is_configured() {
         return (
             StatusCode::CONFLICT,
@@ -280,10 +293,7 @@ pub async fn api_login(State(state): State<AppState>, Json(body): Json<LoginBody
     login_response(StatusCode::OK, &pub_, &session)
 }
 
-pub async fn api_logout(
-    State(state): State<AppState>,
-    headers: axum::http::HeaderMap,
-) -> Response {
+pub async fn api_logout(State(state): State<AppState>, headers: axum::http::HeaderMap) -> Response {
     if let Some(t) = parse_cookie(&headers) {
         state.sessions.revoke(&t);
     }
@@ -449,8 +459,14 @@ mod tests {
     fn public_path_allowlist() {
         // PXE + chrome paths bypass auth.
         for p in [
-            "/", "/assets/app.js", "/boot.ipxe", "/boot/fake.ipxe",
-            "/iso/fake.iso", "/ipxe/snponly.efi", "/healthz", "/readyz",
+            "/",
+            "/assets/app.js",
+            "/boot.ipxe",
+            "/boot/fake.ipxe",
+            "/iso/fake.iso",
+            "/ipxe/snponly.efi",
+            "/healthz",
+            "/readyz",
             "/metrics",
             // v0.4.6: iPXE fetches this for `console --picture` before
             // it can possibly have a session cookie.
@@ -462,6 +478,10 @@ mod tests {
         for p in ["/api/setup", "/api/login", "/api/logout", "/api/me"] {
             assert!(is_public_path(p), "expected {p} to be public");
         }
+        // v0.5.1: SAML SP endpoints are pre-auth (no session yet).
+        for p in ["/api/sso/login", "/api/sso/acs", "/api/sso/metadata"] {
+            assert!(is_public_path(p), "expected {p} to be public");
+        }
         // iPXE long-poll endpoints are public (no cookie available).
         assert!(is_public_path("/api/queue/join"));
         assert!(is_public_path("/api/queue/poll/abc"));
@@ -483,8 +503,7 @@ mod tests {
         let mut h = axum::http::HeaderMap::new();
         h.insert(
             header::COOKIE,
-            HeaderValue::from_str(&format!("foo=bar; {SESSION_COOKIE}=abc123; baz=qux"))
-                .unwrap(),
+            HeaderValue::from_str(&format!("foo=bar; {SESSION_COOKIE}=abc123; baz=qux")).unwrap(),
         );
         assert_eq!(parse_cookie(&h).as_deref(), Some("abc123"));
         // Different name → None.

crates/http-api/src/lib.rs

@@ -19,6 +19,7 @@ pub mod ipxe_script;
 pub mod iso_fs;
 pub mod log_stream;
 pub mod notify;
+pub mod saml_routes;
 pub mod state;
 pub mod terminal;
 pub mod uploads;

crates/http-api/src/saml_routes.rs

@@ -0,0 +1,338 @@
+//! SAML 2.0 Service Provider HTTP endpoints (v0.5.1).
+//!
+//! * `GET  /api/sso/login`    — SP-initiated: build an AuthnRequest, record its
+//!   ID, and 302 the browser to the IdP.
+//! * `POST /api/sso/acs`      — Assertion Consumer Service: verify + validate
+//!   the IdP's `SAMLResponse`, perform the stateful checks (InResponseTo
+//!   correlation, IdP-initiated gating, assertion replay), mint an operator
+//!   session, and 302 to the dashboard. (Mirrors FleetDM's `/sso/callback`.)
+//! * `GET  /api/sso/metadata` — serve our SP metadata XML for IdP import.
+//!
+//! Stateless crypto + semantic validation live in `openpxe_core::saml`; this
+//! module owns only the HTTP glue and the in-memory state the SP needs.
+
+use std::collections::HashMap;
+use std::sync::Arc;
+use std::time::{Duration as StdDuration, Instant};
+
+use axum::{
+    body::Body,
+    extract::{Form, Query, State},
+    http::{header, StatusCode},
+    response::{IntoResponse, Response},
+};
+use base64::Engine;
+use parking_lot::Mutex;
+use serde::Deserialize;
+use time::{Duration, OffsetDateTime};
+
+use openpxe_core::saml::{self, metadata::IdpMetadata, SamlError, SpParams};
+use openpxe_core::SsoConfig;
+
+use crate::auth;
+use crate::state::AppState;
+
+/// Outstanding AuthnRequest IDs live at most this long before a matching
+/// response is considered stale (covers a slow human at the IdP login form).
+const REQUEST_TTL: StdDuration = StdDuration::from_mins(10);
+/// How long we fetch-cache IdP metadata loaded from a URL.
+const METADATA_FETCH_TIMEOUT: StdDuration = StdDuration::from_secs(10);
+
+/// In-memory SAML runtime state. Cheap to clone (Arc-shared).
+#[derive(Clone, Default)]
+pub struct SamlRuntime {
+    /// request_id → issued_at. Correlates a response's `InResponseTo` to a
+    /// request *we* actually sent (replay / CSRF defense for SP-initiated).
+    outstanding: Arc<Mutex<HashMap<String, Instant>>>,
+    /// assertion_id → expiry. A consumed assertion may not be replayed.
+    consumed: Arc<Mutex<HashMap<String, Instant>>>,
+    /// Cache of IdP metadata fetched from a URL: (url, parsed).
+    metadata_cache: Arc<Mutex<Option<(String, IdpMetadata)>>>,
+}
+
+impl SamlRuntime {
+    /// Record an AuthnRequest we just sent.
+    pub fn register_request(&self, id: &str) {
+        let mut g = self.outstanding.lock();
+        prune(&mut g);
+        g.insert(id.to_owned(), Instant::now());
+    }
+
+    /// Consume an outstanding request ID, returning `true` if it was present
+    /// and still fresh. A miss means the response doesn't correlate to any
+    /// live request we issued.
+    pub fn take_request(&self, id: &str) -> bool {
+        let mut g = self.outstanding.lock();
+        prune(&mut g);
+        g.remove(id).is_some()
+    }
+
+    /// Record a consumed assertion. Returns `false` if it was already
+    /// consumed (a replay) — in which case the caller must reject.
+    pub fn record_assertion(&self, id: &str, expiry: OffsetDateTime) -> bool {
+        let mut g = self.consumed.lock();
+        prune(&mut g);
+        if g.contains_key(id) {
+            return false;
+        }
+        let ttl = (expiry - OffsetDateTime::now_utc())
+            .max(Duration::ZERO)
+            .unsigned_abs();
+        g.insert(id.to_owned(), Instant::now() + ttl);
+        true
+    }
+
+    fn cached_metadata(&self, url: &str) -> Option<IdpMetadata> {
+        let g = self.metadata_cache.lock();
+        match &*g {
+            Some((cached_url, md)) if cached_url == url => Some(md.clone()),
+            _ => None,
+        }
+    }
+
+    fn cache_metadata(&self, url: String, md: IdpMetadata) {
+        *self.metadata_cache.lock() = Some((url, md));
+    }
+}
+
+/// Drop expired entries so neither map grows unbounded.
+fn prune(map: &mut HashMap<String, Instant>) {
+    let now = Instant::now();
+    // For the request map this over-prunes (entries store issued_at, not
+    // expiry), so cap by REQUEST_TTL; the consumed map stores absolute
+    // expiry instants. Using saturating logic keeps both correct: request
+    // entries older than REQUEST_TTL go, consumed entries past expiry go.
+    map.retain(|_, &mut t| now.saturating_duration_since(t) < REQUEST_TTL || t > now);
+}
+
+// ─── GET /api/sso/login ───────────────────────────────────────────────────
+
+#[derive(Debug, Deserialize)]
+pub struct LoginQuery {
+    /// Optional local path to return to after login (becomes RelayState).
+    #[serde(default)]
+    pub next: Option<String>,
+}
+
+pub async fn sso_login(State(state): State<AppState>, Query(q): Query<LoginQuery>) -> Response {
+    let cfg = state.sso.snapshot();
+    if !cfg.is_usable() {
+        return redirect("/?sso_error=unavailable");
+    }
+    let idp = match resolve_idp_metadata(&state, &cfg).await {
+        Ok(m) => m,
+        Err(e) => {
+            tracing::warn!(target: "openpxe::saml", "sso_login: metadata unavailable: {e}");
+            return redirect("/?sso_error=metadata");
+        }
+    };
+    let Some(dest) = idp.sso_destination().map(str::to_owned) else {
+        tracing::warn!(target: "openpxe::saml", "sso_login: IdP metadata has no SSO endpoint");
+        return redirect("/?sso_error=metadata");
+    };
+    let sp = sp_params(&state, &cfg);
+    let relay = safe_local_path(q.next.as_deref());
+    match saml::authn_request::build(&sp, &dest, Some(&relay)) {
+        Ok(req) => {
+            state.saml.register_request(&req.id);
+            redirect(&req.location)
+        }
+        Err(e) => {
+            tracing::warn!(target: "openpxe::saml", "sso_login: build AuthnRequest failed: {e}");
+            redirect("/?sso_error=request")
+        }
+    }
+}
+
+// ─── POST /api/sso/acs ──────────────────────────────────────────────────────
+
+#[derive(Debug, Deserialize)]
+pub struct AcsForm {
+    #[serde(rename = "SAMLResponse")]
+    pub saml_response: String,
+    #[serde(rename = "RelayState", default)]
+    pub relay_state: Option<String>,
+}
+
+pub async fn sso_acs(State(state): State<AppState>, Form(form): Form<AcsForm>) -> Response {
+    let cfg = state.sso.snapshot();
+    if !cfg.is_usable() {
+        return redirect("/?sso_error=unavailable");
+    }
+    let xml = match base64::engine::general_purpose::STANDARD.decode(form.saml_response.as_bytes())
+    {
+        Ok(bytes) => String::from_utf8_lossy(&bytes).into_owned(),
+        Err(e) => {
+            tracing::warn!(target: "openpxe::saml", "acs: base64 decode failed: {e}");
+            return redirect("/?sso_error=1");
+        }
+    };
+    let idp = match resolve_idp_metadata(&state, &cfg).await {
+        Ok(m) => m,
+        Err(e) => {
+            tracing::warn!(target: "openpxe::saml", "acs: metadata unavailable: {e}");
+            return redirect("/?sso_error=metadata");
+        }
+    };
+    let sp = sp_params(&state, &cfg);
+
+    // Signature verification + semantic checks are CPU-bound — keep them off
+    // the async executor.
+    let now = OffsetDateTime::now_utc();
+    let skew = Duration::seconds(saml::DEFAULT_CLOCK_SKEW_SECS);
+    let verify = {
+        let xml = xml.clone();
+        let sp = sp.clone();
+        tokio::task::spawn_blocking(move || saml::response::consume(&xml, &sp, &idp, now, skew))
+            .await
+    };
+    let verified = match verify {
+        Ok(Ok(v)) => v,
+        Ok(Err(e)) => {
+            // Never leak which specific check failed to the browser.
+            tracing::warn!(target: "openpxe::saml", "acs: response rejected: {e}");
+            return redirect("/?sso_error=1");
+        }
+        Err(join) => {
+            tracing::error!(target: "openpxe::saml", "acs: verify task panicked: {join}");
+            return redirect("/?sso_error=1");
+        }
+    };
+
+    // Stateful checks the core deliberately left to us.
+    match &verified.in_response_to {
+        Some(id) => {
+            if !state.saml.take_request(id) {
+                tracing::warn!(target: "openpxe::saml", "acs: InResponseTo matches no live request");
+                return redirect("/?sso_error=1");
+            }
+        }
+        None => {
+            if !cfg.allow_idp_initiated {
+                tracing::warn!(target: "openpxe::saml", "acs: IdP-initiated login is disabled");
+                return redirect("/?sso_error=idp_initiated");
+            }
+        }
+    }
+    if !state
+        .saml
+        .record_assertion(&verified.assertion_id, verified.assertion_expiry)
+    {
+        tracing::warn!(target: "openpxe::saml", "acs: assertion replay rejected");
+        return redirect("/?sso_error=1");
+    }
+
+    // Success → mint an operator session keyed to the verified email.
+    let session = state.sessions.create(&verified.principal.email);
+    tracing::info!(
+        target: "openpxe::saml",
+        email = %verified.principal.email,
+        idp_initiated = verified.in_response_to.is_none(),
+        "SAML SSO sign-in"
+    );
+    // safe_local_path already maps None / unsafe values to "/".
+    let relay = safe_local_path(form.relay_state.as_deref());
+    redirect_with_session(&relay, &session)
+}
+
+// ─── GET /api/sso/metadata ──────────────────────────────────────────────────
+
+pub async fn sso_metadata(State(state): State<AppState>) -> Response {
+    let cfg = state.sso.snapshot();
+    let sp = sp_params(&state, &cfg);
+    let xml = saml::metadata::build_sp_metadata(&sp);
+    (
+        StatusCode::OK,
+        [(header::CONTENT_TYPE, "application/samlmetadata+xml")],
+        xml,
+    )
+        .into_response()
+}
+
+// ─── helpers ────────────────────────────────────────────────────────────────
+
+/// Derive runtime SP parameters from config + the advertised public base URL.
+fn sp_params(state: &AppState, cfg: &SsoConfig) -> SpParams {
+    let base = state.public_base_url.trim_end_matches('/');
+    let entity_id = if cfg.entity_id.trim().is_empty() {
+        base.to_owned()
+    } else {
+        cfg.entity_id.trim().to_owned()
+    };
+    SpParams {
+        entity_id,
+        acs_url: format!("{base}/api/sso/acs"),
+    }
+}
+
+/// Resolve the IdP metadata: prefer the metadata URL (fetched + cached) per
+/// the "URL wins" rule, else parse the pasted XML.
+async fn resolve_idp_metadata(state: &AppState, cfg: &SsoConfig) -> Result<IdpMetadata, SamlError> {
+    let url = cfg.metadata_url.trim();
+    if !url.is_empty() {
+        if let Some(md) = state.saml.cached_metadata(url) {
+            return Ok(md);
+        }
+        let body = fetch_metadata(url).await?;
+        let md = IdpMetadata::parse(&body)?;
+        state.saml.cache_metadata(url.to_owned(), md.clone());
+        return Ok(md);
+    }
+    if !cfg.metadata.trim().is_empty() {
+        return IdpMetadata::parse(&cfg.metadata);
+    }
+    Err(SamlError::Metadata("no metadata source configured".into()))
+}
+
+async fn fetch_metadata(url: &str) -> Result<String, SamlError> {
+    let client = reqwest::Client::builder()
+        .timeout(METADATA_FETCH_TIMEOUT)
+        .build()
+        .map_err(|e| SamlError::Metadata(format!("http client: {e}")))?;
+    let resp = client
+        .get(url)
+        .send()
+        .await
+        .map_err(|e| SamlError::Metadata(format!("fetch {url}: {e}")))?;
+    if !resp.status().is_success() {
+        return Err(SamlError::Metadata(format!(
+            "fetch {url}: HTTP {}",
+            resp.status()
+        )));
+    }
+    resp.text()
+        .await
+        .map_err(|e| SamlError::Metadata(format!("read {url}: {e}")))
+}
+
+/// Only permit a same-site path (single leading slash) as a redirect target —
+/// blocks open-redirect / protocol-relative (`//evil.com`) abuse of RelayState.
+fn safe_local_path(p: Option<&str>) -> String {
+    match p {
+        Some(p) if p.starts_with('/') && !p.starts_with("//") => p.to_owned(),
+        _ => "/".to_owned(),
+    }
+}
+
+fn redirect(location: &str) -> Response {
+    Response::builder()
+        .status(StatusCode::FOUND)
+        .header(header::LOCATION, location)
+        .body(Body::empty())
+        .map_or_else(
+            |_| StatusCode::INTERNAL_SERVER_ERROR.into_response(),
+            IntoResponse::into_response,
+        )
+}
+
+fn redirect_with_session(location: &str, session: &str) -> Response {
+    Response::builder()
+        .status(StatusCode::FOUND)
+        .header(header::LOCATION, location)
+        .header(header::SET_COOKIE, auth::session_cookie(session))
+        .body(Body::empty())
+        .map_or_else(
+            |_| StatusCode::INTERNAL_SERVER_ERROR.into_response(),
+            IntoResponse::into_response,
+        )
+}

crates/http-api/src/state.rs

@@ -1,5 +1,6 @@
-use crate::uploads::UploadSessions;
 use crate::auth::SessionStore;
+use crate::saml_routes::SamlRuntime;
+use crate::uploads::UploadSessions;
 use openpxe_core::{
     AdminStore, BootLog, BrandingStore, ClientRegistry, DeploymentQueue, HostBindings, LogBus,
     Metrics, NotifyStore, SettingsStore, SsoStore,
@@ -34,9 +35,13 @@ pub struct AppState {
     /// process restart (sessions are tied to UI state, not persisted —
     /// matches Sonarr/Radarr behaviour).
     pub sessions: SessionStore,
-    /// SAML SSO configuration. v0.4.5 stores it; the actual SSO login
-    /// flow ships in a later release.
+    /// SAML SSO configuration (persisted IdP metadata, Entity ID, toggles).
     pub sso: SsoStore,
+    /// v0.5.1: in-memory SAML runtime state — outstanding AuthnRequest IDs
+    /// (for InResponseTo correlation), consumed-assertion replay guard, and
+    /// a cache of fetched IdP metadata. Tied to process lifetime, like
+    /// `sessions`; a restart simply invalidates any in-flight SSO login.
+    pub saml: SamlRuntime,
     /// v0.5.0: webhook / email notification config (Slack/Teams/Discord/
     /// SMTP). Drives the fire-and-forget pings on boot events and powers
     /// the Advanced tab's config + "Send test" button.

crates/http-api/tests/full_flow.rs

@@ -116,6 +116,7 @@ async fn build_state() -> (AppState, tempfile::TempDir) {
         admin,
         sessions,
         sso,
+        saml: openpxe_http_api::saml_routes::SamlRuntime::default(),
         notify,
         metrics,
         smb: None,
@@ -559,7 +560,10 @@ async fn notify_config_round_trips_and_redacts_smtp_password() {
     assert_eq!(v["kind"], "smtp");
     let pw = v["smtp_password"].as_str().unwrap_or("");
     assert_ne!(pw, "s3cret", "raw password must never be returned");
-    assert!(!pw.is_empty(), "a set password should surface as a sentinel");
+    assert!(
+        !pw.is_empty(),
+        "a set password should surface as a sentinel"
+    );
 }
 
 #[tokio::test]
@@ -1459,7 +1463,7 @@ async fn storage_disk_endpoint_reports_volume_stats() {
     let avail = v["available_bytes"].as_u64().unwrap();
     let used = v["used_bytes"].as_u64().unwrap();
     assert!(total >= avail, "{v}");
-    assert!(total >= used,  "{v}");
+    assert!(total >= used, "{v}");
     assert!(v["path"].as_str().unwrap().contains("isos"), "got {v}");
 }
 
@@ -1551,7 +1555,11 @@ async fn put_json(router: &axum::Router, path: &str, body: &str) -> (StatusCode,
 
 // ─── v0.4.5: Forms auth + SSO ─────────────────────────────────────────────
 
-async fn post_collect(router: &axum::Router, path: &str, body: &str) -> (StatusCode, Vec<u8>, Vec<axum::http::HeaderValue>) {
+async fn post_collect(
+    router: &axum::Router,
+    path: &str,
+    body: &str,
+) -> (StatusCode, Vec<u8>, Vec<axum::http::HeaderValue>) {
     let res = router
         .clone()
         .oneshot(
@@ -1962,7 +1970,10 @@ async fn pxe_background_falls_back_to_default_for_svg_upload() {
     let body = axum::body::to_bytes(res.into_body(), usize::MAX)
         .await
         .unwrap();
-    assert!(body.starts_with(b"\x89PNG"), "should serve default PNG for SVG");
+    assert!(
+        body.starts_with(b"\x89PNG"),
+        "should serve default PNG for SVG"
+    );
     let width = u32::from_be_bytes([body[16], body[17], body[18], body[19]]);
     assert_eq!(width, 1024);
 }
@@ -1974,10 +1985,7 @@ async fn pxe_logo_composes_to_1024x768_png() {
     // the iPXE menu always paints at consistent dimensions.
     let (state, _dir) = build_state().await;
     let png = tiny_png();
-    state
-        .branding
-        .set_logo("image/png", "png", &png)
-        .unwrap();
+    state.branding.set_logo("image/png", "png", &png).unwrap();
     let app = build_router(state);
     let res = app
         .clone()
@@ -2017,10 +2025,7 @@ async fn pxe_logo_endpoint_is_public_after_admin_setup() {
     // auth allowlist gates `/api/*` only.
     let (state, _dir) = build_state().await;
     let png = tiny_png();
-    state
-        .branding
-        .set_logo("image/png", "png", &png)
-        .unwrap();
+    state.branding.set_logo("image/png", "png", &png).unwrap();
     let app = build_router(state);
     // Configure an admin so the middleware kicks in.
     let (s, _, _) = post_collect(
@@ -2034,3 +2039,305 @@ async fn pxe_logo_endpoint_is_public_after_admin_setup() {
     let (s, _) = get(&app, "/branding/pxe-logo").await;
     assert_eq!(s, StatusCode::OK);
 }
+
+// ─── v0.5.1: SAML SSO flow ──────────────────────────────────────────────────
+//
+// The core crate exhaustively tests signature verification + semantic
+// validation (crates/core/src/saml/tests.rs). These integration tests cover
+// the HTTP wiring the core can't: routing, base64 decode, session minting,
+// the InResponseTo / IdP-initiated gating, and assertion-replay rejection.
+
+use base64::Engine as _;
+use openpxe_core::SsoConfig;
+use time::format_description::well_known::Rfc3339;
+use time::{Duration as TimeDuration, OffsetDateTime};
+
+const SP_BASE: &str = "http://127.0.0.1"; // build_state's public_base_url
+const SP_ACS: &str = "http://127.0.0.1/api/sso/acs";
+const IDP_ENTITY: &str = "https://idp.test/realms/fleet";
+const IDP_SSO: &str = "https://idp.test/realms/fleet/protocol/saml";
+
+struct TestIdp {
+    cert_b64: String,
+    key_pem: String,
+}
+
+fn make_idp() -> TestIdp {
+    let ck = rcgen::generate_simple_self_signed(vec!["idp.test".to_string()]).unwrap();
+    let der = ck.cert.der().as_ref().to_vec();
+    TestIdp {
+        cert_b64: base64::engine::general_purpose::STANDARD.encode(der),
+        key_pem: ck.key_pair.serialize_pem(),
+    }
+}
+
+fn idp_metadata_xml(cert_b64: &str) -> String {
+    format!(
+        r#"<md:EntityDescriptor xmlns:md="urn:oasis:names:tc:SAML:2.0:metadata" xmlns:ds="http://www.w3.org/2000/09/xmldsig#" entityID="{IDP_ENTITY}">
+  <md:IDPSSODescriptor protocolSupportEnumeration="urn:oasis:names:tc:SAML:2.0:protocol">
+    <md:KeyDescriptor use="signing"><ds:KeyInfo><ds:X509Data><ds:X509Certificate>{cert_b64}</ds:X509Certificate></ds:X509Data></ds:KeyInfo></md:KeyDescriptor>
+    <md:SingleSignOnService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect" Location="{IDP_SSO}"/>
+  </md:IDPSSODescriptor>
+</md:EntityDescriptor>"#
+    )
+}
+
+/// Build + sign a SAMLResponse with the test IdP key. `in_response_to: None`
+/// makes it an unsolicited (IdP-initiated) response.
+fn signed_response(idp: &TestIdp, in_response_to: Option<&str>) -> String {
+    let now = OffsetDateTime::now_utc().replace_nanosecond(0).unwrap();
+    let fmt = |t: OffsetDateTime| t.format(&Rfc3339).unwrap();
+    let irt = in_response_to
+        .map(|v| format!(r#" InResponseTo="{v}""#))
+        .unwrap_or_default();
+    let template = format!(
+        r##"<samlp:Response xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol" xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion" ID="_resp1" Version="2.0" IssueInstant="{now}" Destination="{SP_ACS}"{irt}>
+  <saml:Issuer>{IDP_ENTITY}</saml:Issuer>
+  <samlp:Status><samlp:StatusCode Value="urn:oasis:names:tc:SAML:2.0:status:Success"/></samlp:Status>
+  <saml:Assertion ID="_assertion1" Version="2.0" IssueInstant="{now}">
+    <saml:Issuer>{IDP_ENTITY}</saml:Issuer>
+    <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
+      <ds:SignedInfo>
+        <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
+        <ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256"/>
+        <ds:Reference URI="#_assertion1">
+          <ds:Transforms>
+            <ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/>
+            <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
+          </ds:Transforms>
+          <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
+          <ds:DigestValue></ds:DigestValue>
+        </ds:Reference>
+      </ds:SignedInfo>
+      <ds:SignatureValue></ds:SignatureValue>
+    </ds:Signature>
+    <saml:Subject>
+      <saml:NameID Format="urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress">[email protected]</saml:NameID>
+      <saml:SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:bearer">
+        <saml:SubjectConfirmationData Recipient="{SP_ACS}" NotOnOrAfter="{noa}"{irt}/>
+      </saml:SubjectConfirmation>
+    </saml:Subject>
+    <saml:Conditions NotBefore="{nb}" NotOnOrAfter="{noa}">
+      <saml:AudienceRestriction><saml:Audience>{SP_BASE}</saml:Audience></saml:AudienceRestriction>
+    </saml:Conditions>
+    <saml:AuthnStatement AuthnInstant="{now}" SessionIndex="sess-1">
+      <saml:AuthnContext><saml:AuthnContextClassRef>urn:oasis:names:tc:SAML:2.0:ac:classes:Password</saml:AuthnContextClassRef></saml:AuthnContext>
+    </saml:AuthnStatement>
+  </saml:Assertion>
+</samlp:Response>"##,
+        now = fmt(now),
+        nb = fmt(now - TimeDuration::minutes(5)),
+        noa = fmt(now + TimeDuration::hours(1)),
+    );
+    let key = bergshamra::keys::loader::load_pem_auto(idp.key_pem.as_bytes(), None).unwrap();
+    let mut km = bergshamra::keys::KeysManager::new();
+    km.add_key(key);
+    let ctx = bergshamra::DsigContext::new(km);
+    bergshamra::sign(&ctx, &template).unwrap()
+}
+
+fn urlencode(s: &str) -> String {
+    let mut out = String::with_capacity(s.len() * 3);
+    for b in s.bytes() {
+        match b {
+            b'A'..=b'Z' | b'a'..=b'z' | b'0'..=b'9' | b'-' | b'_' | b'.' | b'~' => {
+                out.push(b as char);
+            }
+            _ => {
+                out.push('%');
+                out.push(char::from_digit((b >> 4) as u32, 16).unwrap().to_ascii_uppercase());
+                out.push(char::from_digit((b & 0xf) as u32, 16).unwrap().to_ascii_uppercase());
+            }
+        }
+    }
+    out
+}
+
+fn configure_sso(state: &AppState, metadata: String, allow_idp_initiated: bool) {
+    state
+        .sso
+        .replace(SsoConfig {
+            enabled: true,
+            idp_name: "Test IdP".into(),
+            idp_logo_url: String::new(),
+            metadata,
+            metadata_url: String::new(),
+            entity_id: String::new(),
+            allow_idp_initiated,
+        })
+        .unwrap();
+}
+
+async fn post_acs(router: &axum::Router, signed_xml: &str) -> axum::response::Response {
+    let b64 = base64::engine::general_purpose::STANDARD.encode(signed_xml.as_bytes());
+    let body = format!("SAMLResponse={}", urlencode(&b64));
+    router
+        .clone()
+        .oneshot(
+            Request::builder()
+                .method("POST")
+                .uri("/api/sso/acs")
+                .header("content-type", "application/x-www-form-urlencoded")
+                .body(Body::from(body))
+                .unwrap(),
+        )
+        .await
+        .unwrap()
+}
+
+fn has_session_cookie(resp: &axum::response::Response) -> bool {
+    resp.headers().get_all(header::SET_COOKIE).iter().any(|v| {
+        let s = v.to_str().unwrap_or("");
+        s.starts_with("openpxe_session=")
+            && !s.contains("openpxe_session=;")
+            && !s.contains("Max-Age=0")
+    })
+}
+
+fn location(resp: &axum::response::Response) -> String {
+    resp.headers()
+        .get(header::LOCATION)
+        .and_then(|v| v.to_str().ok())
+        .unwrap_or("")
+        .to_owned()
+}
+
+#[tokio::test]
+async fn sso_login_redirects_to_idp() {
+    let (state, _dir) = build_state().await;
+    let idp = make_idp();
+    configure_sso(&state, idp_metadata_xml(&idp.cert_b64), false);
+    let app = build_router(state);
+    let resp = app
+        .clone()
+        .oneshot(
+            Request::builder()
+                .uri("/api/sso/login")
+                .body(Body::empty())
+                .unwrap(),
+        )
+        .await
+        .unwrap();
+    assert_eq!(resp.status(), StatusCode::FOUND);
+    let loc = location(&resp);
+    assert!(loc.starts_with(IDP_SSO), "redirect to IdP, got {loc}");
+    assert!(
+        loc.contains("SAMLRequest="),
+        "carries SAMLRequest, got {loc}"
+    );
+}
+
+#[tokio::test]
+async fn sso_login_unavailable_when_disabled() {
+    let (state, _dir) = build_state().await;
+    let app = build_router(state); // SSO never configured
+    let resp = app
+        .oneshot(
+            Request::builder()
+                .uri("/api/sso/login")
+                .body(Body::empty())
+                .unwrap(),
+        )
+        .await
+        .unwrap();
+    assert_eq!(resp.status(), StatusCode::FOUND);
+    assert!(location(&resp).contains("sso_error"));
+}
+
+#[tokio::test]
+async fn sso_metadata_is_served() {
+    let (state, _dir) = build_state().await;
+    let app = build_router(state);
+    let (status, body) = get(&app, "/api/sso/metadata").await;
+    assert_eq!(status, StatusCode::OK);
+    let xml = String::from_utf8(body).unwrap();
+    assert!(xml.contains("SPSSODescriptor"));
+    assert!(xml.contains(SP_ACS));
+    assert!(xml.contains(SP_BASE));
+}
+
+#[tokio::test]
+async fn acs_idp_initiated_mints_session() {
+    let (state, _dir) = build_state().await;
+    let idp = make_idp();
+    configure_sso(&state, idp_metadata_xml(&idp.cert_b64), true);
+    let app = build_router(state);
+    let signed = signed_response(&idp, None);
+    let resp = post_acs(&app, &signed).await;
+    assert_eq!(resp.status(), StatusCode::FOUND);
+    assert_eq!(location(&resp), "/");
+    assert!(
+        has_session_cookie(&resp),
+        "ACS must set an operator session cookie"
+    );
+}
+
+#[tokio::test]
+async fn acs_idp_initiated_blocked_when_disabled() {
+    let (state, _dir) = build_state().await;
+    let idp = make_idp();
+    configure_sso(&state, idp_metadata_xml(&idp.cert_b64), false); // gate OFF
+    let app = build_router(state);
+    let signed = signed_response(&idp, None);
+    let resp = post_acs(&app, &signed).await;
+    assert_eq!(resp.status(), StatusCode::FOUND);
+    assert!(location(&resp).contains("sso_error"));
+    assert!(
+        !has_session_cookie(&resp),
+        "no session when IdP-initiated is disabled"
+    );
+}
+
+#[tokio::test]
+async fn acs_sp_initiated_without_known_request_is_rejected() {
+    let (state, _dir) = build_state().await;
+    let idp = make_idp();
+    configure_sso(&state, idp_metadata_xml(&idp.cert_b64), true);
+    let app = build_router(state);
+    // A valid signature but an InResponseTo we never issued => reject.
+    let signed = signed_response(&idp, Some("_never-issued"));
+    let resp = post_acs(&app, &signed).await;
+    assert_eq!(resp.status(), StatusCode::FOUND);
+    assert!(location(&resp).contains("sso_error"));
+    assert!(!has_session_cookie(&resp));
+}
+
+#[tokio::test]
+async fn acs_replayed_assertion_is_rejected() {
+    let (state, _dir) = build_state().await;
+    let idp = make_idp();
+    configure_sso(&state, idp_metadata_xml(&idp.cert_b64), true);
+    let app = build_router(state);
+    let signed = signed_response(&idp, None);
+    // First use succeeds…
+    let first = post_acs(&app, &signed).await;
+    assert!(has_session_cookie(&first));
+    // …replaying the identical assertion is rejected.
+    let second = post_acs(&app, &signed).await;
+    assert_eq!(second.status(), StatusCode::FOUND);
+    assert!(location(&second).contains("sso_error"));
+    assert!(!has_session_cookie(&second));
+}
+
+#[tokio::test]
+async fn acs_garbage_is_rejected_without_500() {
+    let (state, _dir) = build_state().await;
+    let idp = make_idp();
+    configure_sso(&state, idp_metadata_xml(&idp.cert_b64), true);
+    let app = build_router(state);
+    let body = "SAMLResponse=not%20valid%20base64%21%21";
+    let resp = app
+        .oneshot(
+            Request::builder()
+                .method("POST")
+                .uri("/api/sso/acs")
+                .header("content-type", "application/x-www-form-urlencoded")
+                .body(Body::from(body))
+                .unwrap(),
+        )
+        .await
+        .unwrap();
+    assert_eq!(resp.status(), StatusCode::FOUND);
+    assert!(location(&resp).contains("sso_error"));
+    assert!(!has_session_cookie(&resp));
+}

crates/openpxe/src/main.rs

@@ -168,6 +168,7 @@ async fn main() -> anyhow::Result<()> {
         admin: admin.clone(),
         sessions: sessions.clone(),
         sso: sso.clone(),
+        saml: openpxe_http_api::saml_routes::SamlRuntime::default(),
         notify: notify.clone(),
         metrics: metrics.clone(),
         smb: Some(smb.clone()),

crates/webui/src/app.css

@@ -797,3 +797,46 @@ tr.unbootable td:first-child { border-left: 3px solid var(--warn); }
 .logo-preview .info { flex: 1; min-width: 0; }
 .logo-preview .info .name { color: var(--fg); font-weight: 600; }
 .logo-preview .info .meta { color: var(--fg-dim); font-size: 12px; margin-top: 2px; }
+
+/* v0.5.1: collapsible "Advanced" disclosure at the bottom of Settings
+   (the former Advanced sidebar tab). A quiet, full-width toggle that
+   expands to reveal the notification + API-reference cards. */
+.advanced-disclosure { width: 100%; }
+.advanced-summary {
+  list-style: none;
+  cursor: pointer;
+  user-select: none;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  padding: 10px 14px;
+  color: var(--fg-dim);
+  font-size: 13px;
+  font-weight: 600;
+  background: var(--bg-panel-2);
+  border: 1px solid var(--border);
+  border-radius: var(--radius);
+}
+.advanced-summary:hover { color: var(--fg); }
+.advanced-summary::-webkit-details-marker { display: none; }
+.advanced-summary::before {
+  content: "▸";
+  font-size: 11px;
+  transition: transform 0.15s ease;
+}
+.advanced-disclosure[open] .advanced-summary::before { transform: rotate(90deg); }
+
+/* v0.5.1: protocol tag on a unified Remote-shares row (SMB / NFS). */
+.proto-badge {
+  display: inline-block;
+  font-size: 10px;
+  font-weight: 700;
+  letter-spacing: 0.04em;
+  padding: 1px 6px;
+  margin-right: 8px;
+  border-radius: 4px;
+  vertical-align: middle;
+  background: var(--bg-panel-2);
+  border: 1px solid var(--border);
+  color: var(--fg-dim);
+}

crates/webui/src/app.js

@@ -684,19 +684,46 @@
           ])
         : el('div', {class:'empty'}, 'No images yet. Upload an ISO or add an SMB share.');
 
-      // ── SMB shares section (v0.4.65) ──
-      // Replaces the kernel-mount NFS card. SMB shares are consumed
-      // in userspace via Samba's `smbclient` CLI — no kernel modules,
-      // no CAP_SYS_ADMIN, works in any container. This is the same
-      // approach Bootimus uses.
-      const smbMsg = el('div', {class:'msg'});
+      // ── Remote shares section (v0.5.1) ──
+      // SMB + NFS unified into one "Remote shares" card with a protocol
+      // dropdown. The two protocols keep their own backend endpoints
+      // (/api/smb-shares, /api/nfs-shares) and the same add/scan/remove
+      // UX; the form just swaps the relevant fields. This declutters the
+      // Storage tab and leaves room for a future "Config files" card.
+      const shareMsg = el('div', {class:'msg'});
+
+      // Shared structured-error renderer ({error, stderr, hint}) for both
+      // protocols' add calls.
+      const showShareError = async (r) => {
+        let bodyJson = null;
+        let raw = null;
+        try { bodyJson = await r.clone().json(); }
+        catch (_) { raw = await r.text().catch(() => 'connect failed'); }
+        const msg = bodyJson && bodyJson.error ? bodyJson.error : (raw || 'connect failed');
+        const hint = bodyJson && bodyJson.hint;
+        const parts = [el('div', {}, [
+          el('strong', {}, 'Connect failed: '),
+          document.createTextNode(msg),
+        ])];
+        if (hint) {
+          parts.push(el('div', {style:'margin-top:6px;opacity:.78;font-size:12px'}, hint));
+        }
+        shareMsg.replaceChildren(...parts);
+        shareMsg.className = 'msg err';
+      };
+
+      // Protocol picker — swaps which field block is visible.
+      const protoSelect = el('select', {}, [
+        el('option', {value:'smb'}, 'SMB / CIFS'),
+        el('option', {value:'nfs'}, 'NFS (NFSv3)'),
+      ]);
+
+      // SMB inputs.
       const smbServer = el('input', {type:'text', placeholder:'192.168.1.51'});
       const smbShare = el('input', {type:'text', placeholder:'isos'});
       const smbGuest = el('input', {type:'checkbox'}); smbGuest.checked = true;
       const smbUser = el('input', {type:'text', placeholder:'(disabled when Guest)'});
       const smbPass = el('input', {type:'password', placeholder:'(disabled when Guest)'});
-      // Toggle username/password fields based on the Guest checkbox so
-      // operators don't get confused about which fields matter.
       const syncAuthDisabled = () => {
         smbUser.disabled = smbGuest.checked;
         smbPass.disabled = smbGuest.checked;
@@ -705,58 +732,23 @@
       };
       smbGuest.addEventListener('change', syncAuthDisabled);
       syncAuthDisabled();
+      const smbFields = el('div', {}, [
+        el('div', {class:'form-row cols-2'}, [
+          el('label', {class:'field'}, [el('span', {class:'name'}, 'SMB server'), smbServer]),
+          el('label', {class:'field'}, [el('span', {class:'name'}, 'Share name'), smbShare]),
+        ]),
+        el('div', {class:'form-row cols-3', style:'margin-top:14px'}, [
+          el('label', {class:'check'}, [smbGuest, el('span', {}, 'Guest (anonymous read)')]),
+          el('label', {class:'field'}, [el('span', {class:'name'}, 'Username'), smbUser]),
+          el('label', {class:'field'}, [el('span', {class:'name'}, 'Password'), smbPass]),
+        ]),
+      ]);
 
-      const addSmb = el('button', {onclick: async () => {
-        if (!smbServer.value || !smbShare.value) {
-          smbMsg.replaceChildren(document.createTextNode('Server and share name are required.'));
-          smbMsg.className='msg err'; return;
-        }
-        if (!smbGuest.checked && !smbUser.value) {
-          smbMsg.replaceChildren(document.createTextNode('Username is required when Guest is unchecked.'));
-          smbMsg.className='msg err'; return;
-        }
-        smbMsg.replaceChildren(document.createTextNode('Connecting…'));
-        smbMsg.className = 'msg';
-        const body = {
-          server: smbServer.value,
-          share: smbShare.value,
-          guest: smbGuest.checked,
-        };
-        if (!smbGuest.checked) {
-          body.username = smbUser.value;
-          body.password = smbPass.value;
-        }
-        const r = await postJSON('/api/smb-shares', body);
-        if (r.ok) {
-          smbMsg.replaceChildren(document.createTextNode('Connected.'));
-          smbMsg.className = 'msg ok';
-          render('storage');
-        } else {
-          // The API returns a structured {error, stderr, hint} JSON
-          // body on failure so the raw smbclient error and the
-          // actionable hint render as two distinct lines.
-          let bodyJson = null;
-          let raw = null;
-          try { bodyJson = await r.clone().json(); }
-          catch (_) { raw = await r.text().catch(()=> 'connect failed'); }
-          const msg = bodyJson && bodyJson.error ? bodyJson.error : (raw || 'connect failed');
-          const hint = bodyJson && bodyJson.hint;
-          const parts = [el('div', {}, [
-            el('strong', {}, 'Connect failed: '),
-            document.createTextNode(msg),
-          ])];
-          if (hint) {
-            parts.push(el('div', {style:'margin-top:6px;opacity:.78;font-size:12px'}, hint));
-          }
-          smbMsg.replaceChildren(...parts);
-          smbMsg.className = 'msg err';
-        }
-      }}, 'Add share');
-
-      const smbRows = shares.length ? shares.map(m => el('div', {class: 'nfs-row' + (m.reachable ? '' : ' down')}, [
+      const smbRowEls = shares.map(m => el('div', {class: 'nfs-row' + (m.reachable ? '' : ' down')}, [
         el('span', {class: 'dot ' + (m.reachable ? 'ok' : 'err')}),
         el('div', {}, [
-          el('div', {class:'id'}, '//' + m.server + '/' + m.share),
+          el('div', {class:'id'}, [el('span', {class:'proto-badge'}, 'SMB'),
+            document.createTextNode('//' + m.server + '/' + m.share)]),
           el('div', {class:'meta'},
             (m.guest ? 'guest' : ('user: ' + (m.username || '?'))) + ' · ' +
             (m.reachable ? m.iso_count + ' isos' : 'not reachable')),
@@ -773,59 +765,75 @@
           render('storage');
         }}, 'Remove'),
         el('span'),
-      ])) : [el('div', {class:'empty'}, 'No SMB shares configured.')];
+      ]));
 
-      // ── NFS shares section (v0.4.67) ──
-      // Parallel to SMB shares above. The NFSv3 client is in-process
-      // (nfs3_client crate) so NFS-sourced ISOs support HTTP Range
-      // requests — SMB-sourced ones don't (smbclient CLI can't seek
-      // mid-stream). Otherwise the UX is identical: server + export,
-      // submit, scan, remove.
-      const nfsMsg = el('div', {class:'msg'});
+      // NFS inputs. The NFSv3 client is in-process (nfs3_client crate) so
+      // NFS-sourced ISOs support HTTP Range — SMB-sourced ones can't seek
+      // mid-stream. No auth fields: NFSv3 access is gated by client IP on
+      // the server's export list, not client-supplied credentials.
       const nfsServerIn = el('input', {type:'text', placeholder:'10.0.0.5'});
       const nfsExportIn = el('input', {type:'text', placeholder:'/srv/isos'});
-      const addNfs = el('button', {style:'margin-top:14px', onclick: async () => {
-        if (!nfsServerIn.value || !nfsExportIn.value) {
-          nfsMsg.replaceChildren(document.createTextNode('Server and export are required.'));
-          nfsMsg.className = 'msg err'; return;
-        }
-        nfsMsg.replaceChildren(document.createTextNode('Connecting…'));
-        nfsMsg.className = 'msg';
-        const r = await postJSON('/api/nfs-shares', {
-          server: nfsServerIn.value,
-          export: nfsExportIn.value,
-        });
-        if (r.ok) {
-          nfsMsg.replaceChildren(document.createTextNode('Connected.'));
-          nfsMsg.className = 'msg ok';
-          render('storage');
-        } else {
-          // Structured {error, stderr, hint} same as SMB.
-          let bodyJson = null;
-          let raw = null;
-          try { bodyJson = await r.clone().json(); }
-          catch (_) { raw = await r.text().catch(()=> 'connect failed'); }
-          const msg = bodyJson && bodyJson.error ? bodyJson.error : (raw || 'connect failed');
-          const hint = bodyJson && bodyJson.hint;
-          const parts = [el('div', {}, [
-            el('strong', {}, 'Connect failed: '),
-            document.createTextNode(msg),
-          ])];
-          if (hint) {
-            parts.push(el('div', {style:'margin-top:6px;opacity:.78;font-size:12px'}, hint));
+      const nfsFields = el('div', {}, [
+        el('div', {class:'form-row cols-2'}, [
+          el('label', {class:'field'}, [el('span', {class:'name'}, 'NFS server'), nfsServerIn]),
+          el('label', {class:'field'}, [el('span', {class:'name'}, 'Export path'), nfsExportIn]),
+        ]),
+      ]);
+
+      // Swap the visible field block + clear any stale message.
+      const syncProto = () => {
+        const nfs = protoSelect.value === 'nfs';
+        smbFields.style.display = nfs ? 'none' : '';
+        nfsFields.style.display = nfs ? '' : 'none';
+        shareMsg.replaceChildren();
+        shareMsg.className = 'msg';
+      };
+      protoSelect.addEventListener('change', syncProto);
+
+      // One add button; dispatches to the selected protocol's endpoint.
+      const addShare = el('button', {style:'margin-top:14px', onclick: async () => {
+        if (protoSelect.value === 'smb') {
+          if (!smbServer.value || !smbShare.value) {
+            shareMsg.replaceChildren(document.createTextNode('Server and share name are required.'));
+            shareMsg.className = 'msg err'; return;
           }
-          nfsMsg.replaceChildren(...parts);
-          nfsMsg.className = 'msg err';
+          if (!smbGuest.checked && !smbUser.value) {
+            shareMsg.replaceChildren(document.createTextNode('Username is required when Guest is unchecked.'));
+            shareMsg.className = 'msg err'; return;
+          }
+          shareMsg.replaceChildren(document.createTextNode('Connecting…'));
+          shareMsg.className = 'msg';
+          const body = { server: smbServer.value, share: smbShare.value, guest: smbGuest.checked };
+          if (!smbGuest.checked) { body.username = smbUser.value; body.password = smbPass.value; }
+          const r = await postJSON('/api/smb-shares', body);
+          if (r.ok) {
+            shareMsg.replaceChildren(document.createTextNode('Connected.'));
+            shareMsg.className = 'msg ok';
+            render('storage');
+          } else { await showShareError(r); }
+        } else {
+          if (!nfsServerIn.value || !nfsExportIn.value) {
+            shareMsg.replaceChildren(document.createTextNode('Server and export are required.'));
+            shareMsg.className = 'msg err'; return;
+          }
+          shareMsg.replaceChildren(document.createTextNode('Connecting…'));
+          shareMsg.className = 'msg';
+          const r = await postJSON('/api/nfs-shares', { server: nfsServerIn.value, export: nfsExportIn.value });
+          if (r.ok) {
+            shareMsg.replaceChildren(document.createTextNode('Connected.'));
+            shareMsg.className = 'msg ok';
+            render('storage');
+          } else { await showShareError(r); }
         }
       }}, 'Add share');
 
-      const nfsRows = nfsShares.length ? nfsShares.map(m => el('div', {class: 'nfs-row' + (m.reachable ? '' : ' down')}, [
+      const nfsRowEls = nfsShares.map(m => el('div', {class: 'nfs-row' + (m.reachable ? '' : ' down')}, [
         el('span', {class: 'dot ' + (m.reachable ? 'ok' : 'err')}),
         el('div', {}, [
-          el('div', {class:'id'}, m.server + ':' + m.export),
+          el('div', {class:'id'}, [el('span', {class:'proto-badge'}, 'NFS'),
+            document.createTextNode(m.server + ':' + m.export)]),
           el('div', {class:'meta'},
-            'NFSv3 · ' +
-            (m.reachable ? m.iso_count + ' isos' : 'not reachable')),
+            'NFSv3 · ' + (m.reachable ? m.iso_count + ' isos' : 'not reachable')),
           m.last_error ? el('div', {class:'err'}, '⚠ ' + m.last_error) : null,
           m.last_hint ? el('div', {style:'margin-top:4px;opacity:.78;font-size:12px'}, m.last_hint) : null,
         ]),
@@ -839,7 +847,13 @@
           render('storage');
         }}, 'Remove'),
         el('span'),
-      ])) : [el('div', {class:'empty'}, 'No NFS shares configured.')];
+      ]));
+
+      const totalShares = shares.length + nfsShares.length;
+      const remoteRows = totalShares
+        ? [...smbRowEls, ...nfsRowEls]
+        : [el('div', {class:'empty'}, 'No remote shares configured.')];
+      syncProto();
 
       const diskCard = diskSpaceCard(disk);
 
@@ -849,77 +863,36 @@
           el('header', {}, el('h2', {}, 'Upload ISO')),
           el('div', {class:'body'}, [drop, file, prog, upMsg]),
         ]),
+        // v0.5.1: SMB + NFS unified into one "Remote shares" card with a
+        // protocol dropdown. Backend endpoints are unchanged; this is a
+        // pure UI consolidation that declutters the Storage tab.
         el('div', {class:'card'}, [
           el('header', {}, [
-            el('h2', {}, 'SMB shares'),
-            el('span', {class:'sub'}, shares.length + ' configured'),
+            el('h2', {}, 'Remote shares'),
+            el('span', {class:'sub'}, totalShares + ' configured'),
           ]),
           el('div', {class:'body'}, [
             el('div', {class:'form-row cols-2'}, [
               el('label', {class:'field'}, [
-                el('span', {class:'name'}, 'SMB server'),
-                smbServer,
-              ]),
-              el('label', {class:'field'}, [
-                el('span', {class:'name'}, 'Share name'),
-                smbShare,
+                el('span', {class:'name'}, 'Protocol'),
+                protoSelect,
               ]),
+              el('span'),
             ]),
-            el('div', {class:'form-row cols-3', style:'margin-top:14px'}, [
-              el('label', {class:'check'}, [
-                smbGuest, el('span', {}, 'Guest (anonymous read)'),
-              ]),
-              el('label', {class:'field'}, [
-                el('span', {class:'name'}, 'Username'),
-                smbUser,
-              ]),
-              el('label', {class:'field'}, [
-                el('span', {class:'name'}, 'Password'),
-                smbPass,
-              ]),
-            ]),
-            addSmb, smbMsg,
-            el('div', {style:'margin-top:18px;display:grid;gap:8px'}, smbRows),
+            el('div', {style:'margin-top:14px'}, [smbFields, nfsFields]),
+            addShare, shareMsg,
+            el('div', {style:'margin-top:18px;display:grid;gap:8px'}, remoteRows),
             el('p', {class:'msg', style:'margin-top:14px'},
-              'SMB shares are read in userspace via Samba’s smbclient — ' +
-              'no kernel modules, no CAP_SYS_ADMIN, works in any container ' +
-              '(Unraid, OpenShift restricted SCC, plain Docker, etc.). Most NAS ' +
-              'appliances expose ISO libraries as guest-readable; check the box ' +
-              'above when that’s the case. ISOs are streamed on demand at PXE ' +
-              'boot time — no local cache, no double disk usage.'),
-          ]),
-        ]),
-        // v0.4.67: NFS shares card sits right below SMB so operators
-        // can see both protocols at a glance. The form is simpler
-        // (no auth) because NFSv3 access control is by client IP on
-        // the server side, not by client-supplied credentials.
-        el('div', {class:'card'}, [
-          el('header', {}, [
-            el('h2', {}, 'NFS shares'),
-            el('span', {class:'sub'}, nfsShares.length + ' configured'),
-          ]),
-          el('div', {class:'body'}, [
-            el('div', {class:'form-row cols-2'}, [
-              el('label', {class:'field'}, [
-                el('span', {class:'name'}, 'NFS server'),
-                nfsServerIn,
-              ]),
-              el('label', {class:'field'}, [
-                el('span', {class:'name'}, 'Export path'),
-                nfsExportIn,
-              ]),
-            ]),
-            addNfs, nfsMsg,
-            el('div', {style:'margin-top:18px;display:grid;gap:8px'}, nfsRows),
-            el('p', {class:'msg', style:'margin-top:14px'},
-              'NFSv3 shares are read in-process via a pure-Rust client — ' +
-              'no kernel modules, no mount.nfs, no CAP_SYS_ADMIN. Works in ' +
-              'every container the SMB path works in (Unraid included). ' +
-              'NFSv3 auth is AUTH_SYS only; gate access on the server side ' +
-              'by allowing this OpenPXE host’s IP in the export list. ' +
-              'ISOs are streamed on demand and HTTP Range requests work — ' +
-              'NFSv3 READ3 takes an explicit offset, so clients can seek ' +
-              'into a 5 GB ISO without reading what comes before.'),
+              'Remote ISO libraries are read on demand — no local cache, no ' +
+              'double disk usage. SMB/CIFS is read in userspace via Samba’s ' +
+              'smbclient; NFSv3 via a pure-Rust in-process client. Both work in ' +
+              'any container (Unraid, OpenShift restricted SCC, plain Docker) with ' +
+              'no kernel modules and no CAP_SYS_ADMIN. SMB supports guest or ' +
+              'user/password; most NAS appliances expose ISO libraries as ' +
+              'guest-readable. NFSv3 auth is AUTH_SYS only — gate access by ' +
+              'allowing this OpenPXE host’s IP in the server’s export list. ' +
+              'NFS-sourced ISOs also support HTTP Range (seek into a 5 GB ISO ' +
+              'without reading what precedes the offset); SMB streams sequentially.'),
           ]),
         ]),
         el('div', {class:'card'}, [
@@ -1204,12 +1177,16 @@
     },
 
     settings: async () => {
-      const [status, me, sso] = await Promise.all([
+      const [status, me, sso, notify, docs] = await Promise.all([
         getJSON('/api/status'),
         getJSON('/api/me').catch(() => ({})),
         getJSON('/api/sso').catch(() => ({
           enabled:false, idp_name:'', metadata:'', metadata_url:'',
         })),
+        // v0.5.1: the former Advanced tab folds in here, so Settings
+        // fetches the notify config + API docs it needs too.
+        getJSON('/api/notify').catch(() => ({ enabled:false, kind:'slack' })),
+        getJSON('/api/docs').catch(() => ({ groups: [] })),
       ]);
       const hasLogo = !!status.custom_logo;
 
@@ -1507,18 +1484,26 @@
         ]),
       ]);
 
-      // v0.5.0: the API reference moved to the Advanced tab; Settings
-      // now holds just account / SSO / branding.
-      return el('div', {class:'grid'}, [accountCard, ssoCard, logoCard]);
+      // v0.5.1: the former "Advanced" sidebar tab now lives here, folded
+      // into a collapsible disclosure beneath the core settings cards —
+      // webhook/email notifications + the API reference. Keeps Settings
+      // clean by default while leaving the knobs one click away.
+      const [notifyCard, apiCard] = views._advancedCards(notify, docs);
+      const advanced = el('details', {class:'advanced-disclosure', style:'margin-top:18px'}, [
+        el('summary', {class:'advanced-summary'}, 'Advanced'),
+        el('div', {class:'grid', style:'margin-top:14px'}, [notifyCard, apiCard]),
+      ]);
+      return el('div', {}, [
+        el('div', {class:'grid'}, [accountCard, ssoCard, logoCard]),
+        advanced,
+      ]);
     },
 
-    // v0.5.0: Advanced settings — webhook/email notifications, and the
-    // API reference (relocated from the bottom of Settings).
-    advanced: async () => {
-      const [notify, docs] = await Promise.all([
-        getJSON('/api/notify').catch(() => ({ enabled:false, kind:'slack' })),
-        getJSON('/api/docs').catch(() => ({ groups: [] })),
-      ]);
+    // v0.5.1: builds the two "Advanced" cards — webhook/email notifications
+    // and the API reference. There is no longer an Advanced sidebar tab;
+    // the Settings view folds these into a collapsible disclosure and
+    // passes in the pre-fetched `notify` + `docs` payloads.
+    _advancedCards: (notify, docs) => {
 
       // ── Notification config ──
       const nMsg = el('div', {class:'msg', style:'margin-top:12px'});
@@ -1600,7 +1585,7 @@
       const saveBtn = el('button', {style:'margin-top:16px', onclick: async () => {
         nMsg.textContent = 'Saving…'; nMsg.className = 'msg';
         const r = await putJSON('/api/notify', collectNotify());
-        if (r.ok) { nMsg.textContent = 'Saved.'; nMsg.className = 'msg ok'; render('advanced'); }
+        if (r.ok) { nMsg.textContent = 'Saved.'; nMsg.className = 'msg ok'; render('settings'); }
         else { nMsg.textContent = 'Save failed: ' + (await r.text()); nMsg.className = 'msg err'; }
       }}, 'Save notification settings');
       const testBtn = el('button', {class:'ghost', style:'margin-top:16px;margin-left:8px',
@@ -1656,7 +1641,7 @@
                 'No API documentation returned by /api/docs.')),
       ]);
 
-      return el('div', {class:'grid'}, [notifyCard, apiCard]);
+      return [notifyCard, apiCard];
     },
 
     about: async () => {
@@ -1770,7 +1755,6 @@
     hosts: 'Hosts',
     terminal: 'Terminal',
     settings: 'Settings',
-    advanced: 'Advanced',
     about: 'About',
   };
 
@@ -1910,16 +1894,28 @@
     const err = el('div', {class:'auth-err', style:'display:none'});
     const submit = el('button', {class:'submit', type:'submit'}, 'Sign in');
 
+    // v0.5.1: surface a failed/blocked SSO round-trip. The ACS handler
+    // redirects back to "/?sso_error=..." on any failure; we show a
+    // generic, non-leaky message and scrub the query so a refresh is clean.
+    const ssoErr = new URLSearchParams(window.location.search).get('sso_error');
+    if (ssoErr) {
+      err.textContent = ssoErr === 'idp_initiated'
+        ? 'IdP-initiated SSO is disabled. Use the “Sign in with …” button, or enable it under Settings → SSO.'
+        : (ssoErr === 'unavailable' || ssoErr === 'metadata')
+          ? 'Single sign-on is unavailable right now. Sign in with the local admin, or check the SSO settings.'
+          : 'SSO sign-in failed. Please try again, or sign in with the local admin.';
+      err.style.display = '';
+      window.history.replaceState({}, '', window.location.pathname);
+    }
+
     const ssoButton = ssoConfig && ssoConfig.enabled && (ssoConfig.metadata_url || ssoConfig.metadata)
       ? el('button', {type:'button', class:'sso-btn', onclick: () => {
-          // SSO login flow lands in a later release — for now we
-          // surface a friendly note so the operator knows the config
-          // landed but the runtime hookup is pending.
-          err.textContent = 'SSO sign-in is configured but the runtime flow ships in a future release. Sign in with the local admin for now.';
-          err.style.display = '';
+          // SP-initiated SAML login (v0.5.1): hand off to the IdP. The
+          // /api/sso/acs endpoint verifies the response, mints the
+          // operator session, and redirects back to the dashboard.
+          window.location.assign('/api/sso/login');
         }}, [
           el('div', {}, 'Sign in with ' + (ssoConfig.idp_name || 'SSO')),
-          el('div', {class:'meta'}, 'configured · runtime flow pending'),
         ])
       : null;
 

crates/webui/src/index.html

@@ -53,7 +53,6 @@
       </a>
       <a data-view="terminal">Terminal</a>
       <a data-view="settings">Settings</a>
-      <a data-view="advanced">Advanced</a>
       <a data-view="about">About</a>
     </nav>
     <div class="footer">