fix: Add example file with CAWG X.509 signing (#948)

cawg_identity/src/tests/examples/mod.rs

@@ -0,0 +1,15 @@
+// Copyright 2025 Adobe. All rights reserved.
+// This file is licensed to you under the Apache License,
+// Version 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
+// or the MIT license (http://opensource.org/licenses/MIT),
+// at your option.
+
+// Unless required by applicable law or agreed to in writing,
+// this software is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR REPRESENTATIONS OF ANY KIND, either express or
+// implied. See the LICENSE-MIT and LICENSE-APACHE files for the
+// specific language governing permissions and limitations under
+// each license.
+
+#[cfg(not(target_arch = "wasm32"))]
+mod x509_signing;

cawg_identity/src/tests/examples/x509_signing.rs

@@ -0,0 +1,102 @@
+// Copyright 2025 Adobe. All rights reserved.
+// This file is licensed to you under the Apache License,
+// Version 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
+// or the MIT license (http://opensource.org/licenses/MIT),
+// at your option.
+
+// Unless required by applicable law or agreed to in writing,
+// this software is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR REPRESENTATIONS OF ANY KIND, either express or
+// implied. See the LICENSE-MIT and LICENSE-APACHE files for the
+// specific language governing permissions and limitations under
+// each license.
+
+//! Test case that demonstrates generating a new C2PA asset (JPEG in this case)
+//! with a C2PA claim signer signature and a CAWG identity assertion with its
+//! own X.509 signature from a different credential holder.
+
+use std::io::{Cursor, Seek};
+
+use c2pa::{Builder, Reader, SigningAlg};
+use c2pa_crypto::raw_signature;
+
+use crate::{
+    builder::{AsyncIdentityAssertionBuilder, AsyncIdentityAssertionSigner},
+    tests::fixtures::{cert_chain_and_private_key_for_alg, manifest_json, parent_json},
+    x509::{X509CredentialHolder, X509SignatureVerifier},
+    IdentityAssertion,
+};
+
+const TEST_IMAGE: &[u8] = include_bytes!("../../../../sdk/tests/fixtures/CA.jpg");
+const TEST_THUMBNAIL: &[u8] = include_bytes!("../../../../sdk/tests/fixtures/thumbnail.jpg");
+
+#[cfg_attr(not(target_arch = "wasm32"), tokio::test)]
+#[ignore] // We'll only run this occasionally if we need to update this test.
+async fn x509_signing() {
+    let format = "image/jpeg";
+    let mut source = Cursor::new(TEST_IMAGE);
+    let mut dest = Cursor::new(Vec::new());
+
+    let mut builder = Builder::from_json(&manifest_json()).unwrap();
+    builder
+        .add_ingredient_from_stream(parent_json(), format, &mut source)
+        .unwrap();
+
+    builder
+        .add_resource("thumbnail.jpg", Cursor::new(TEST_THUMBNAIL))
+        .unwrap();
+
+    let mut c2pa_signer = AsyncIdentityAssertionSigner::from_test_credentials(SigningAlg::Ps256);
+
+    let (cawg_cert_chain, cawg_private_key) =
+        cert_chain_and_private_key_for_alg(SigningAlg::Ed25519);
+
+    let cawg_raw_signer = raw_signature::async_signer_from_cert_chain_and_private_key(
+        &cawg_cert_chain,
+        &cawg_private_key,
+        SigningAlg::Ed25519,
+        None,
+    )
+    .unwrap();
+
+    let x509_holder = X509CredentialHolder::from_async_raw_signer(cawg_raw_signer);
+    let iab = AsyncIdentityAssertionBuilder::for_credential_holder(x509_holder);
+    c2pa_signer.add_identity_assertion(iab);
+
+    builder
+        .sign_async(&c2pa_signer, format, &mut source, &mut dest)
+        .await
+        .unwrap();
+
+    // Write the sample file.
+    std::fs::write("src/tests/examples/x509_signing.jpg", dest.get_ref()).unwrap();
+
+    // --- THE REST OF THIS EXAMPLE IS TEST CODE ONLY. ---
+    //
+    // The following code reads back the content from the file that was just
+    // generated and verifies that it is valid.
+    //
+    // In a normal scenario when generating an asset with a CAWG identity assertion,
+    // you could stop at this point.
+
+    dest.rewind().unwrap();
+
+    let manifest_store = Reader::from_stream(format, &mut dest).unwrap();
+    assert_eq!(manifest_store.validation_status(), None);
+
+    let manifest = manifest_store.active_manifest().unwrap();
+    let mut ia_iter = IdentityAssertion::from_manifest(manifest);
+
+    let ia = ia_iter.next().unwrap().unwrap();
+    assert!(ia_iter.next().is_none());
+
+    let x509_verifier = X509SignatureVerifier {};
+    let sig_info = ia.validate(manifest, &x509_verifier).await.unwrap();
+
+    let cert_info = &sig_info.cert_info;
+    assert_eq!(cert_info.alg.unwrap(), SigningAlg::Ed25519);
+    assert_eq!(
+        cert_info.issuer_org.as_ref().unwrap(),
+        "C2PA Test Signing Cert"
+    );
+}

cawg_identity/src/tests/mod.rs

@@ -20,6 +20,7 @@
 
 mod builder;
 mod claim_aggregation;
+mod examples;
 pub(crate) mod fixtures;
 mod identity_assertion;
 mod internal;