Merge pull request #813 from jku/upgrade-sigstore

Upgrade sigstore dependency

Author: Lukas Pühringer

.github/workflows/test-sigstore.yml

@@ -1,11 +1,10 @@
 name: Run Sigstore Signer tests
 
 on:
-  ## Disabled temporarily: #781
-  #push:
-  #  branches:
-  #    - main
-  #pull_request:
+  push:
+    branches:
+      - main
+  pull_request:
   workflow_dispatch:
 
 permissions: {}

mypy.ini

@@ -20,9 +20,6 @@ ignore_missing_imports = True
 [mypy-asn1crypto.*]
 ignore_missing_imports = True
 
-[mypy-sigstore.*]
-ignore_missing_imports = True
-
 [mypy-sigstore_protobuf_specs.*]
 ignore_missing_imports = True
 

pyproject.toml

@@ -52,7 +52,7 @@ azurekms = ["azure-identity", "azure-keyvault-keys", "cryptography>=40.0.0"]
 awskms = ["boto3", "botocore", "cryptography>=40.0.0"]
 hsm = ["asn1crypto", "cryptography>=40.0.0", "PyKCS11"]
 PySPX = ["PySPX>=0.5.0"]
-sigstore = ["sigstore~=2.0"]
+sigstore = ["sigstore~=3.0"]
 vault = ["hvac", "cryptography>=40.0.0"]
 
 [tool.hatch.version]

requirements-sigstore.txt

@@ -1 +1 @@
-sigstore==2.1.5
+sigstore==3.0.0

securesystemslib/signer/_sigstore_signer.py

@@ -1,13 +1,7 @@
 """Signer implementation for project sigstore.
-
-NOTE: SigstoreSigner and -Key are disabled temporarily around
-the Securesystemslib 1.0 release as the cyclic dependency
-(securesystemslib -> sigstore-python -> tuf -> securesystemslib)
-is problematic during API deprecations.
-See issue #781.
 """
 
-import io
+import json
 import logging
 from typing import Any, Dict, Optional, Tuple
 from urllib import parse
@@ -66,37 +60,38 @@ def to_dict(self) -> Dict:
 
     def verify_signature(self, signature: Signature, data: bytes) -> None:
         # pylint: disable=import-outside-toplevel,import-error
-        result = None
         try:
-            from sigstore.verify import VerificationMaterials, Verifier
+            from sigstore.errors import VerificationError as SigstoreVerifyError
+            from sigstore.models import Bundle
+            from sigstore.verify import Verifier
             from sigstore.verify.policy import Identity
-            from sigstore_protobuf_specs.dev.sigstore.bundle.v1 import Bundle
+        except ImportError as e:
+            raise VerificationError(IMPORT_ERROR) from e
 
+        try:
             verifier = Verifier.production()
             identity = Identity(
                 identity=self.keyval["identity"], issuer=self.keyval["issuer"]
             )
-            bundle = Bundle().from_dict(signature.unrecognized_fields["bundle"])
-            materials = VerificationMaterials.from_bundle(
-                input_=io.BytesIO(data), bundle=bundle, offline=True
-            )
-            result = verifier.verify(materials, identity)
+            bundle_data = signature.unrecognized_fields["bundle"]
+            bundle = Bundle.from_json(json.dumps(bundle_data))
 
-        except Exception as e:
-            logger.info("Key %s failed to verify sig: %s", self.keyid, str(e))
-            raise VerificationError(
-                f"Unknown failure to verify signature by {self.keyid}"
-            ) from e
+            verifier.verify_artifact(data, bundle, identity)
 
-        if not result:
+        except SigstoreVerifyError as e:
             logger.info(
                 "Key %s failed to verify sig: %s",
                 self.keyid,
-                getattr(result, "reason", ""),
+                e,
             )
             raise UnverifiedSignatureError(
                 f"Failed to verify signature by {self.keyid}"
-            )
+            ) from e
+        except Exception as e:
+            logger.info("Key %s failed to verify sig: %s", self.keyid, str(e))
+            raise VerificationError(
+                f"Unknown failure to verify signature by {self.keyid}"
+            ) from e
 
 
 class SigstoreSigner(Signer):
@@ -189,9 +184,9 @@ def from_priv_key_uri(
 
         key_identity = public_key.keyval["identity"]
         key_issuer = public_key.keyval["issuer"]
-        if key_issuer != token.expected_certificate_subject:
+        if key_issuer != token.federated_issuer:
             raise ValueError(
-                f"Signer identity issuer {token.expected_certificate_subject} "
+                f"Signer identity issuer {token.federated_issuer} "
                 f"did not match key: {key_issuer}"
             )
         # TODO: should check ambient identity too: unfortunately IdentityToken does
@@ -246,9 +241,7 @@ def import_via_auth(cls) -> Tuple[str, SigstoreKey]:
 
         # authenticate to get the identity and issuer
         token = Issuer.production().identity_token()
-        return cls.import_(
-            token.identity, token.expected_certificate_subject, False
-        )
+        return cls.import_(token.identity, token.federated_issuer, False)
 
     def sign(self, payload: bytes) -> Signature:
         """Signs payload using the OIDC token on the signer instance.
@@ -273,12 +266,12 @@ def sign(self, payload: bytes) -> Signature:
 
         context = SigningContext.production()
         with context.signer(self._token) as sigstore_signer:
-            result = sigstore_signer.sign(io.BytesIO(payload))
-
-        bundle = result.to_bundle()
-
+            bundle = sigstore_signer.sign_artifact(payload)
+        # We want to access the actual signature, see
+        # https://github.com/sigstore/protobuf-specs/blob/main/protos/sigstore_bundle.proto
+        bundle_json = json.loads(bundle.to_json())
         return Signature(
             self.public_key.keyid,
-            bundle.message_signature.signature.hex(),
-            {"bundle": bundle.to_dict()},
+            bundle_json["messageSignature"]["signature"],
+            {"bundle": bundle_json},
         )

tests/check_sigstore_signer.py

@@ -20,6 +20,10 @@
 from tempfile import TemporaryDirectory
 from unittest import mock
 
+from securesystemslib.exceptions import (
+    UnverifiedSignatureError,
+    VerificationError,
+)
 from securesystemslib.signer import (
     SIGNER_FOR_URI_SCHEME,
     Signer,
@@ -100,8 +104,19 @@ def test_sign(self):
             signer = Signer.from_priv_key_uri(uri, public_key)
 
         sig = signer.sign(b"data")
+
+        # Successful verification
         public_key.verify_signature(sig, b"data")
 
+        # Signature mismatch
+        with self.assertRaises(UnverifiedSignatureError):
+            public_key.verify_signature(sig, b"incorrect data")
+
+        # Broken bundle
+        sig.unrecognized_fields["bundle"]["verificationMaterial"] = None
+        with self.assertRaises(VerificationError):
+            public_key.verify_signature(sig, b"data")
+
 
 if __name__ == "__main__":
     unittest.main(verbosity=4, buffer=False)

tox.ini

@@ -63,6 +63,7 @@ commands =
 deps =
     -r{toxinidir}/requirements-pinned.txt
     -r{toxinidir}/requirements-lint.txt
+    -r{toxinidir}/requirements-sigstore.txt
 commands =
     black --check --diff  .
     isort --check --diff  .