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]>

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="));
+    }
+}