fix: holder DID must match the signing key for vc+sd-jwt

identity-wallet/src/state/credentials/reducers/handle_oid4vp_authorization_request.rs

@@ -43,6 +43,7 @@ use oid4vc::oid4vp::{
 
 use identity_credential::{credential::Jwt, presentation::Presentation};
 use identity_iota::core::Url;
+use identity_iota::did::DIDUrl;
 use jsonwebtoken::Algorithm;
 use jsonwebtoken::Header;
 use sd_jwt::{KeyBindingJwtBuilder, RequiredKeyBinding, SdJwt};
@@ -342,26 +343,28 @@ async fn get_vp_token(
     let dcql_query = &oid4vp_authorization_request.body.extension.dcql_query;
     let mut builder = VpTokenBuilder::builder_dcql_query(dcql_query.clone());
 
-    let key_id = subject_manager
-        .key_id(did_method, signing_algorithm)
-        .await
-        .ok_or_else(|| AppError::Error(format!("Failed to get signing method ID for DID method {did_method}")))?;
-
-    let full_did = subject_manager
-        .identifier(did_method, signing_algorithm)
-        .await
-        .map_err(|e| AppError::Error(format!("Failed to get DID identifier: {e}")))?;
-
-    let holder_url: Url =
-        Url::parse(&full_did).map_err(|e| AppError::Error(format!("Failed to parse DID as URL: {e}")))?;
-
     // TODO: Move most of this logic to `openid4vc` crates.
     for (credential_query_from_dcql, vc_value) in selected_verifiable_credentials {
         let credential_query_id = credential_query_from_dcql.id.clone();
         let format_from_query = credential_query_from_dcql.format;
 
         let presentation_format_item = match format_from_query {
             Format::JwtVcJson => {
+                let key_id = subject_manager
+                    .key_id(did_method, signing_algorithm)
+                    .await
+                    .ok_or_else(|| {
+                        AppError::Error(format!("Failed to get signing method ID for DID method {did_method}"))
+                    })?;
+
+                let full_did = subject_manager
+                    .identifier(did_method, signing_algorithm)
+                    .await
+                    .map_err(|e| AppError::Error(format!("Failed to get DID identifier: {e}")))?;
+
+                let holder_url: Url =
+                    Url::parse(&full_did).map_err(|e| AppError::Error(format!("Failed to parse DID as URL: {e}")))?;
+
                 let raw_vc_jwt_string = vc_value
                     .as_str()
                     .ok_or(AppError::InvalidCredentialFormatError)?
@@ -457,12 +460,39 @@ async fn get_vp_token(
                     .parse::<SdJwt>()
                     .map_err(|err| AppError::Error(format!("Failed to parse VCDM 2.0 SD-JWT: {err}")))?;
 
+                // TODO: unify holder DID/key selection into a single helper.
+                // "Which DID/key do we sign with?" is answered differently at every call site: the `cnf`
+                // claim here, from `credentialSubject.id` when signing a DACT, and from the preferred
+                // DID method elsewhere. Each answer has to match the DID the credential was issued to, so they
+                // all need to behave identically. This should be unified into a single helper. 
+                let Some(RequiredKeyBinding::Kid(cnf_kid)) = vcdm2_sd_jwt.claims().cnf.as_ref() else {
+                    return Err(AppError::Error(
+                        "Unsupported `cnf` claim in VCDM 2.0 SD-JWT".to_string(),
+                    ));
+                };
+
+                let cnf_jwk = subject_manager
+                    .resolve_public_key(cnf_kid)
+                    .await
+                    .map_err(|e| AppError::Error(format!("Failed to resolve `cnf` key from DID URL: {e}")))?;
+
+                let algorithm = cnf_jwk
+                    .alg()
+                    .ok_or_else(|| AppError::Error("JWK missing `alg` parameter".to_string()))?;
+
+                let holder_did = DIDUrl::parse(cnf_kid)
+                    .map_err(|e| AppError::Error(format!("Failed to parse 'cnf' DID URL: {e}")))?
+                    .did()
+                    .to_string();
+                let holder_url =
+                    Url::parse(&holder_did).map_err(|e| AppError::Error(format!("Failed to parse holder URL: {e}")))?;
+
                 let id = VcDataUrl::parse(&format!("data:application/vc+sd-jwt,{vcdm2_sd_jwt}"))
                     .map_err(|e| AppError::Error(format!("Failed to parse VcDataUrl: {e}")))?;
                 let enveloped_credential = EnvelopedVc::new(id);
 
                 let mut properties = IotaObject::default();
-                properties.insert("iss".to_string(), full_did.clone().into());
+                properties.insert("iss".to_string(), holder_did.clone().into());
                 properties.insert("aud".to_string(), verifier_audience.clone().into());
                 properties.insert("nonce".to_string(), required_nonce.clone().into());
                 properties.insert("iat".to_string(), Utc::now().timestamp().into());
@@ -476,21 +506,6 @@ async fn get_vp_token(
                     .build_v2()
                     .map_err(|e| AppError::Error(format!("Failed to build Presentation: {e}")))?;
 
-                let Some(RequiredKeyBinding::Kid(cnf_kid)) = vcdm2_sd_jwt.claims().cnf.as_ref() else {
-                    return Err(AppError::Error(
-                        "Unsupported `cnf` claim in VCDM 2.0 SD-JWT".to_string(),
-                    ));
-                };
-
-                let cnf_jwk = subject_manager
-                    .resolve_public_key(cnf_kid)
-                    .await
-                    .map_err(|e| AppError::Error(format!("Failed to resolve `cnf` key from DID URL: {e}")))?;
-
-                let algorithm = cnf_jwk
-                    .alg()
-                    .ok_or_else(|| AppError::Error("JWK missing `alg` parameter".to_string()))?;
-
                 let jwt_header = Header {
                     alg: Algorithm::from_str(algorithm).unwrap(),
                     kid: Some(cnf_kid.clone()),