fix(iam): disambiguate OIDC virtual parent IDs (#5700)

crates/iam/src/federation/model.rs

@@ -64,10 +64,13 @@ impl FederatedAuthorization {
             return None;
         }
 
-        let mut source = Vec::with_capacity(8 + subject.len() + issuer.len());
+        let subject_len = u64::try_from(subject.len()).ok()?;
+        let issuer_len = u64::try_from(issuer.len()).ok()?;
+        let mut source = Vec::with_capacity(23 + subject.len() + issuer.len());
         source.extend_from_slice(b"openid:");
+        source.extend_from_slice(&subject_len.to_be_bytes());
         source.extend_from_slice(subject.as_bytes());
-        source.push(b':');
+        source.extend_from_slice(&issuer_len.to_be_bytes());
         source.extend_from_slice(issuer.as_bytes());
         let digest = HashAlgorithm::SHA256.hash_encode(&source);
         Some(base64_simd::URL_SAFE_NO_PAD.encode_to_string(digest.as_ref()))
@@ -145,7 +148,7 @@ mod tests {
     }
 
     #[test]
-    fn oidc_virtual_parent_matches_minio_and_is_issuer_scoped() {
+    fn oidc_virtual_parent_is_issuer_scoped() {
         let first = authorization(Vec::new(), Vec::new());
         let mut second = first.clone();
         second
@@ -155,7 +158,7 @@ mod tests {
 
         assert_eq!(
             first.oidc_virtual_parent().as_deref(),
-            Some("TwyekekG2eMes0qk9Tgh7KXEitwGi1z2W1f2KccrXGA")
+            Some("HwDfWftzOy4jiuS3WjKytC_Sg_A2hKhrRAFtBDhoBr0")
         );
         assert!(!rustfs_policy::auth::contains_reserved_chars(
             first.oidc_virtual_parent().as_deref().expect("virtual parent")
@@ -163,6 +166,24 @@ mod tests {
         assert_ne!(first.oidc_virtual_parent(), second.oidc_virtual_parent());
     }
 
+    #[test]
+    fn oidc_virtual_parent_length_delimits_identity_parts() {
+        let mut first = authorization(Vec::new(), Vec::new());
+        first.claims.sub = "subject".to_string();
+        first.claims.raw.insert(
+            "iss".to_string(),
+            Value::String("https://issuer.example/path:https://other.example".to_string()),
+        );
+        let mut second = authorization(Vec::new(), Vec::new());
+        second.claims.sub = "subject:https://issuer.example/path".to_string();
+        second
+            .claims
+            .raw
+            .insert("iss".to_string(), Value::String("https://other.example".to_string()));
+
+        assert_ne!(first.oidc_virtual_parent(), second.oidc_virtual_parent());
+    }
+
     #[test]
     fn oidc_virtual_parent_requires_verified_identity_parts() {
         let mut missing_issuer = authorization(Vec::new(), Vec::new());