fix(connect): preserve signature precedence across chain parsing

rustfs/src/connect/offline/enrollment.rs

@@ -286,7 +286,7 @@ struct DocumentSignature {
 struct ChallengeRouting {
     connect_key_id: String,
     issued_at: String,
-    trust_chain: Vec<SignedDocument>,
+    trust_chain: Vec<serde_json::Value>,
 }
 
 #[derive(Deserialize)]
@@ -382,26 +382,33 @@ impl OfflineEnrollment {
         let issued_at = parse_timestamp(&routing.issued_at)?;
 
         // The frozen decision order classifies the top-level signature before
-        // parsing any trust-link routing fields. Otherwise a malformed first
-        // link could mask a malformed artifact signature with DOCUMENT_MALFORMED.
+        // parsing any trust-link envelope or routing fields. Otherwise a
+        // malformed link could mask a malformed artifact signature with
+        // DOCUMENT_MALFORMED.
         let signature = decode_signature(&envelope.signature)?;
 
         let first = routing.trust_chain.first().ok_or(EnrollmentError::MalformedDocument)?;
-        let first_bytes = decode_document_bytes(&first.bytes)?;
+        let first_bytes = first
+            .get("bytes")
+            .and_then(serde_json::Value::as_str)
+            .ok_or(EnrollmentError::MalformedDocument)
+            .and_then(decode_document_bytes)?;
         let first_routing: TrustLinkRouting =
             serde_json::from_slice(&first_bytes).map_err(|_| EnrollmentError::MalformedDocument)?;
         if !is_key_id(&first_routing.issuer_key_id) {
             return Err(EnrollmentError::MalformedDocument);
         }
 
+        // The pinned-root decision precedes full chain-envelope validation.
+        if first_routing.issuer_key_id != root.key_id {
+            return Err(EnrollmentError::EnrollmentRootUnknown);
+        }
+        let trust_chain: Vec<SignedDocument> = serde_json::from_value(serde_json::Value::Array(routing.trust_chain))
+            .map_err(|_| EnrollmentError::TrustChainInvalid)?;
+
         // Steps 3 to 5.
-        let connect_key = verify_trust_chain(
-            &routing.trust_chain,
-            &routing.connect_key_id,
-            &first_routing.issuer_key_id,
-            issued_at,
-            root,
-        )?;
+        let connect_key =
+            verify_trust_chain(&trust_chain, &routing.connect_key_id, &first_routing.issuer_key_id, issued_at, root)?;
 
         // Step 6. The detached signature must name the same chained key whose
         // public key verifies it. A different well-formed key id is a signature

rustfs/tests/connect_offline_enrollment.rs

@@ -594,6 +594,25 @@ fn malformed_top_level_signature_precedes_malformed_first_link_routing() {
     assert_eq!(error.reason(), "SIGNATURE_MALFORMED");
 }
 
+#[test]
+fn malformed_top_level_signature_precedes_malformed_second_link_envelope() {
+    let source = accept_vector_named("challenge signed by a chained signing key under the pinned root");
+    let now = unix(field(&source, "evaluationTime"));
+    let mut challenge_envelope = source["document"].clone();
+    challenge_envelope["signature"]["algorithm"] = Value::String("ES384".to_string());
+
+    let mut challenge = signed_document(&challenge_envelope);
+    challenge["trustChain"].as_array_mut().expect("challenge carries a chain")[1]
+        .as_object_mut()
+        .expect("trust link envelope is an object")
+        .remove("signature");
+    challenge_envelope["bytes"] = Value::String(encoded_document(&challenge));
+
+    let error = OfflineEnrollment::verify_challenge(&envelope(&challenge_envelope), now)
+        .expect_err("a malformed top-level signature and second-link envelope must not verify");
+    assert_eq!(error.reason(), "SIGNATURE_MALFORMED");
+}
+
 #[test]
 fn unpinned_root_precedes_a_malformed_chain_shape() {
     let source = accept_vector_named("challenge signed by a chained signing key under the pinned root");