(fix): cert chain crash and bundle creation (#615)

Signed-off-by: Sachin Sampras M <sampras343@gmail.com>

Author: sampras343

src/model_signing/_signing/sign_certificate.py

@@ -72,8 +72,11 @@ def __init__(
                 "the public key paired with the private key"
             )
 
-        self._trust_chain = x509.load_pem_x509_certificates(
-            b"".join([path.read_bytes() for path in certificate_chain_paths])
+        chain_bytes = b"".join(
+            [path.read_bytes() for path in certificate_chain_paths]
+        )
+        self._trust_chain = (
+            x509.load_pem_x509_certificates(chain_bytes) if chain_bytes else []
         )
 
     @override

src/model_signing/_signing/sign_pkcs11.py

@@ -244,16 +244,21 @@ def __init__(
                 "the public key paired with the private key"
             )
 
-        self._trust_chain = x509.load_pem_x509_certificates(
-            b"".join([path.read_bytes() for path in certificate_chain_paths])
+        chain_bytes = b"".join(
+            [path.read_bytes() for path in certificate_chain_paths]
+        )
+        self._trust_chain = (
+            x509.load_pem_x509_certificates(chain_bytes) if chain_bytes else []
         )
 
     @override
     def _get_verification_material(self) -> bundle_pb.VerificationMaterial:
         def _to_protobuf_certificate(certificate):
             return common_pb.X509Certificate(
-                raw_bytes=certificate.public_bytes(
-                    encoding=serialization.Encoding.DER
+                raw_bytes=base64.b64encode(
+                    certificate.public_bytes(
+                        encoding=serialization.Encoding.DER
+                    )
                 )
             )
 
@@ -268,5 +273,6 @@ def _to_protobuf_certificate(certificate):
         return bundle_pb.VerificationMaterial(
             x509_certificate_chain=common_pb.X509CertificateChain(
                 certificates=chain
-            )
+            ),
+            tlog_entries=[],
         )