General Improvements 4

src/principal.rs

@@ -233,26 +233,26 @@ pub fn sign_credential(
     Ok(format!("{}.{}", payload_b64, sig_b64))
 }
 
-/// Verify and decode a signed credential, returning the claims if valid.
+/// Verify the cryptographic signature and expiry of a signed credential.
 ///
-/// Checks performed:
-/// 1. Signature verification (HMAC-SHA256)
-/// 2. Expiry verification
-/// 3. Pod identity binding
+/// This performs only the pure cryptographic checks that require no external state:
+/// 1. Parse the credential format
+/// 2. Verify HMAC-SHA256 signature
+/// 3. Check expiry
 ///
-/// Revocation and attempt-active checks require external state (database) and
-/// must be performed by the caller after this returns `Ok`.
-pub fn verify_credential(
+/// Returns the verified claims on success. The caller is responsible for
+/// performing persistence-level validation (pod binding, attempt active,
+/// revocation) after this returns `Ok`.
+pub fn verify_signature(
     credential: &str,
     secret: &[u8],
-    expected_pod_id: Uuid,
 ) -> Result<CredentialClaims, CredentialError> {
     use base64::Engine;
     use hmac::{Hmac, Mac};
     use sha2::Sha256;
 
-    let (payload_b64, sig_b64) = SignedCredential::parse(credential)
-        .ok_or(CredentialError::MalformedPayload)?;
+    let (payload_b64, sig_b64) =
+        SignedCredential::parse(credential).ok_or(CredentialError::MalformedPayload)?;
 
     // Decode payload
     let payload_bytes = base64::engine::general_purpose::URL_SAFE_NO_PAD
@@ -276,6 +276,25 @@ pub fn verify_credential(
         return Err(CredentialError::Expired);
     }
 
+    Ok(claims)
+}
+
+/// Verify and decode a signed credential, returning the claims if valid.
+///
+/// Checks performed:
+/// 1. Signature verification (HMAC-SHA256)
+/// 2. Expiry verification
+/// 3. Pod identity binding
+///
+/// Revocation and attempt-active checks require external state (database) and
+/// must be performed by the caller after this returns `Ok`.
+pub fn verify_credential(
+    credential: &str,
+    secret: &[u8],
+    expected_pod_id: Uuid,
+) -> Result<CredentialClaims, CredentialError> {
+    let claims = verify_signature(credential, secret)?;
+
     // Check pod binding
     if claims.pod_id != expected_pod_id {
         return Err(CredentialError::PodMismatch);