key helpers: verification key to object: In progress

Asciinema: https://asciinema.org/a/627150
Asciinema: https://asciinema.org/a/627165
Asciinema: https://asciinema.org/a/627183
Signed-off-by: John Andersen <[email protected]>

docs/registration_policies.md

@@ -93,6 +93,7 @@ from jsonschema import validate, ValidationError
 
 from scitt_emulator.scitt import ClaimInvalidError, CWTClaims
 from scitt_emulator.verify_statement import verify_statement
+from scitt_emulator.key_helpers import verification_key_to_object
 
 
 def main():
@@ -107,23 +108,30 @@ def main():
             f"Claim content type does not start with application/json: {msg.phdr[pycose.headers.ContentType]!r}"
         )
 
-    cwt_cose_key, _pycose_cose_key = verify_statement(msg)
+    verification_key = verify_statement(msg)
     unittest.TestCase().assertTrue(
-        cwt_cose_key,
+        verification_key,
         "Failed to verify signature on statement",
     )
 
-    cwt_protected = cwt.decode(msg.phdr[CWTClaims], cwt_cose_key)
+    cwt_protected = cwt.decode(msg.phdr[CWTClaims], verification_key.cwt)
     issuer = cwt_protected[1]
     subject = cwt_protected[2]
 
+    issuer_key_as_object = verification_key_to_object(verification_key)
+    unittest.TestCase().assertTrue(
+        issuer_key_as_object,
+        "Failed to convert issuer key to JSON schema verifiable object",
+    )
+
     SCHEMA = json.loads(pathlib.Path(os.environ["SCHEMA_PATH"]).read_text())
 
     try:
         validate(
             instance={
                 "$schema": "https://schema.example.com/scitt-policy-engine-jsonschema.schema.json",
                 "issuer": issuer,
+                "issuer_key": issuer_key_as_object,
                 "subject": subject,
                 "claim": json.loads(msg.payload.decode()),
             },

scitt_emulator/key_helper_dataclasses.py

@@ -0,0 +1,17 @@
+from dataclasses import dataclass, field
+from typing import List, Any, Union
+
+import cwt
+import pycose.keys.ec2
+
+
+@dataclass
+class VerificationKey:
+    transforms: List[Any]
+    original: Any
+    original_content_type: str
+    original_bytes: bytes
+    original_bytes_encoding: str
+    usable: bool
+    cwt: Union[cwt.COSEKey, None]
+    cose: Union[pycose.keys.ec2.EC2Key, None]

scitt_emulator/key_helpers.py

@@ -0,0 +1,43 @@
+import itertools
+import importlib.metadata
+from typing import Optional, Callable, List, Tuple
+
+from scitt_emulator.key_helper_dataclasses import VerificationKey
+
+
+ENTRYPOINT_KEY_TRANSFORMS_TO_OBJECT = "scitt_emulator.key_helpers.verification_key_to_object"
+
+
+def verification_key_to_object(
+    verification_key: VerificationKey,
+    *,
+    key_transforms: Optional[List[Callable[[VerificationKey], dict]]] = None,
+) -> bool:
+    """
+    Resolve keys for statement issuer and verify signature on COSESign1
+    statement and embedded CWT
+    """
+    if key_transforms is None:
+        key_transforms = []
+        # There is some difference in the return value of entry_points across
+        # Python versions/envs (conda vs. non-conda). Python 3.8 returns a dict.
+        entrypoints = importlib.metadata.entry_points()
+        if isinstance(entrypoints, dict):
+            for entrypoint in entrypoints.get(ENTRYPOINT_KEY_TRANSFORMS_TO_OBJECT, []):
+                key_transforms.append(entrypoint.load())
+        elif isinstance(entrypoints, getattr(importlib.metadata, "EntryPoints", list)):
+            for entrypoint in entrypoints:
+                if entrypoint.group == ENTRYPOINT_KEY_TRANSFORMS_TO_OBJECT:
+                    key_transforms.append(entrypoint.load())
+        else:
+            raise TypeError(f"importlib.metadata.entry_points returned unknown type: {type(entrypoints)}: {entrypoints!r}")
+
+    # Load keys from issuer and attempt verification. Return key used to verify
+    for verification_key_as_object in itertools.chain(
+        *[key_transform(unverified_issuer) for key_transform in key_transforms]
+    ):
+        # Skip keys that we couldn't derive COSE keys for
+        if verification_key_as_object:
+            return verification_key_as_object
+
+    return None

scitt_emulator/key_loader_format_did_key.py

@@ -4,45 +4,48 @@
 import cwt.algs.ec2
 import pycose
 import pycose.keys.ec2
+import cryptography.hazmat.primitives.asymmetric.ec
 from cryptography.hazmat.primitives import serialization
 
 # TODO Remove this once we have a example flow for proper key verification
 import jwcrypto.jwk
 
 from scitt_emulator.did_helpers import DID_KEY_METHOD, did_key_to_cryptography_key
+from scitt_emulator.key_helper_dataclasses import VerificationKey
+
+
+# TODO What is the correct content type? Should we differ if it's been expanded?
+CONTENT_TYPE = "application/key+did"
 
 
 def key_loader_format_did_key(
     unverified_issuer: str,
-) -> List[Tuple[cwt.COSEKey, pycose.keys.ec2.EC2Key]]:
-    jwk_keys = []
-    cwt_cose_keys = []
-    pycose_cose_keys = []
-    cryptography_keys = []
-
+) -> List[VerificationKey]:
     if not unverified_issuer.startswith(DID_KEY_METHOD):
-        return pycose_cose_keys
-
-    cryptography_keys.append(did_key_to_cryptography_key(unverified_issuer))
-
-    for cryptography_key in cryptography_keys:
-        jwk_keys.append(
-            jwcrypto.jwk.JWK.from_pem(
-                cryptography_key.public_bytes(
-                    encoding=serialization.Encoding.PEM,
-                    format=serialization.PublicFormat.SubjectPublicKeyInfo,
-                )
-            )
+        return []
+    key = did_key_to_cryptography_key(unverified_issuer)
+    return [
+        VerificationKey(
+            transforms=[key],
+            original=key,
+            original_content_type=CONTENT_TYPE,
+            original_bytes=unverified_issuer.encode("utf-8"),
+            original_bytes_encoding="utf-8",
+            usable=False,
+            cwt=None,
+            cose=None,
         )
-
-    for jwk_key in jwk_keys:
-        cwt_cose_key = cwt.COSEKey.from_pem(
-            jwk_key.export_to_pem(),
-            kid=jwk_key.thumbprint(),
+    ]
+
+
+def transform_key_instance_cryptography_ecc_public_to_jwcrypto_jwk(
+    key: cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey,
+) -> jwcrypto.jwk.JWK:
+    if not isinstance(key, cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey):
+        raise TypeError(key)
+    return jwcrypto.jwk.JWK.from_pem(
+        key.public_bytes(
+            encoding=serialization.Encoding.PEM,
+            format=serialization.PublicFormat.SubjectPublicKeyInfo,
         )
-        cwt_cose_keys.append(cwt_cose_key)
-        cwt_ec2_key_as_dict = cwt_cose_key.to_dict()
-        pycose_cose_key = pycose.keys.ec2.EC2Key.from_dict(cwt_ec2_key_as_dict)
-        pycose_cose_keys.append((cwt_cose_key, pycose_cose_key))
-
-    return pycose_cose_keys
+    )

scitt_emulator/key_loader_format_url_referencing_oidc_issuer.py

@@ -13,20 +13,22 @@
 import jwcrypto.jwk
 
 from scitt_emulator.did_helpers import did_web_to_url
+from scitt_emulator.key_helper_dataclasses import VerificationKey
+
+
+CONTENT_TYPE = "application/jwk+json"
 
 
 def key_loader_format_url_referencing_oidc_issuer(
     unverified_issuer: str,
 ) -> List[Tuple[cwt.COSEKey, pycose.keys.ec2.EC2Key]]:
-    jwk_keys = []
-    cwt_cose_keys = []
-    pycose_cose_keys = []
+    keys = []
 
     if unverified_issuer.startswith("did:web:"):
         unverified_issuer = did_web_to_url(unverified_issuer)
 
     if "://" not in unverified_issuer or unverified_issuer.startswith("file://"):
-        return pycose_cose_keys
+        return keys
 
     # TODO Logging for URLErrors
     # Check if OIDC issuer
@@ -44,18 +46,40 @@ def key_loader_format_url_referencing_oidc_issuer(
                         jwks = json.loads(response.read())
                         for jwk_key_as_dict in jwks["keys"]:
                             jwk_key_as_string = json.dumps(jwk_key_as_dict)
-                            jwk_keys.append(
-                                jwcrypto.jwk.JWK.from_json(jwk_key_as_string),
+                            jwk_key = jwcrypto.jwk.JWK.from_json(jwk_key_as_string)
+                            keys.append(
+                                VerificationKey(
+                                    transforms=[jwk_key],
+                                    original=jwk_key,
+                                    original_content_type=CONTENT_TYPE,
+                                    original_bytes=jwk_key_as_string.encode("utf-8"),
+                                    original_bytes_encoding="utf-8",
+                                    usable=False,
+                                    cwt=None,
+                                    cose=None,
+                                )
                             )
 
-    for jwk_key in jwk_keys:
-        cwt_cose_key = cwt.COSEKey.from_pem(
-            jwk_key.export_to_pem(),
-            kid=jwk_key.thumbprint(),
-        )
-        cwt_cose_keys.append(cwt_cose_key)
-        cwt_ec2_key_as_dict = cwt_cose_key.to_dict()
-        pycose_cose_key = pycose.keys.ec2.EC2Key.from_dict(cwt_ec2_key_as_dict)
-        pycose_cose_keys.append((cwt_cose_key, pycose_cose_key))
-
-    return pycose_cose_keys
+    return keys
+
+
+def transform_key_instance_jwcrypto_jwk_to_cwt_cose(
+    key: jwcrypto.jwk.JWK,
+) -> cwt.COSEKey:
+    if not isinstance(key, jwcrypto.jwk.JWK):
+        raise TypeError(key)
+    return cwt.COSEKey.from_pem(
+        key.export_to_pem(),
+        kid=key.thumbprint(),
+    )
+
+
+def to_object_oidc_issuer(verification_key: VerificationKey) -> dict:
+    if verification_key.original_content_type != CONTENT_TYPE:
+        return
+
+    return {
+        **verification_key.original.export_public(as_dict=True),
+        "use": "sig",
+        "kid": verification_key.original.thumbprint(),
+    }

scitt_emulator/key_loader_format_url_referencing_ssh_authorized_keys.py

@@ -19,17 +19,13 @@
 def key_loader_format_url_referencing_ssh_authorized_keys(
     unverified_issuer: str,
 ) -> List[Tuple[cwt.COSEKey, pycose.keys.ec2.EC2Key]]:
-    jwk_keys = []
-    cwt_cose_keys = []
-    pycose_cose_keys = []
-
-    cryptography_ssh_keys = []
+    keys = []
 
     if unverified_issuer.startswith("did:web:"):
         unverified_issuer = did_web_to_url(unverified_issuer)
 
     if "://" not in unverified_issuer or unverified_issuer.startswith("file://"):
-        return pycose_cose_keys
+        return keys
 
     # Try loading ssh keys. Example: https://github.com/username.keys
     with contextlib.suppress(urllib.request.URLError):
@@ -38,28 +34,18 @@ def key_loader_format_url_referencing_ssh_authorized_keys(
                 with contextlib.suppress(
                     (ValueError, cryptography.exceptions.UnsupportedAlgorithm)
                 ):
-                    cryptography_ssh_keys.append(
-                        serialization.load_ssh_public_key(line)
+                    key = serialization.load_ssh_public_key(line)
+                    keys.append(
+                        VerificationKey(
+                            transforms=[key],
+                            original=key,
+                            original_content_type=CONTENT_TYPE,
+                            original_bytes=line.encode("utf-8"),
+                            original_bytes_encoding="utf-8",
+                            usable=False,
+                            cwt=None,
+                            cose=None,
+                        )
                     )
 
-    for cryptography_ssh_key in cryptography_ssh_keys:
-        jwk_keys.append(
-            jwcrypto.jwk.JWK.from_pem(
-                cryptography_ssh_key.public_bytes(
-                    encoding=serialization.Encoding.PEM,
-                    format=serialization.PublicFormat.SubjectPublicKeyInfo,
-                )
-            )
-        )
-
-    for jwk_key in jwk_keys:
-        cwt_cose_key = cwt.COSEKey.from_pem(
-            jwk_key.export_to_pem(),
-            kid=jwk_key.thumbprint(),
-        )
-        cwt_cose_keys.append(cwt_cose_key)
-        cwt_ec2_key_as_dict = cwt_cose_key.to_dict()
-        pycose_cose_key = pycose.keys.ec2.EC2Key.from_dict(cwt_ec2_key_as_dict)
-        pycose_cose_keys.append((cwt_cose_key, pycose_cose_key))
-
-    return pycose_cose_keys
+    return keys