Support for ECDSA deterministic signing (RFC 6979) (#10369)

* Add support for deterministic ECDSA (RFC 6979)

2 files changed, 118 insertions, 0 deletions

diff --git a/tests/hazmat/primitives/test_ec.py b/tests/hazmat/primitives/test_ec.py
index a558af3..33b4c6d 100644
--- a/tests/hazmat/primitives/test_ec.py
+++ b/tests/hazmat/primitives/test_ec.py
@@ -16,6 +16,10 @@ from cryptography import exceptions, utils, x509
 from cryptography.hazmat.bindings._rust import openssl as rust_openssl
 from cryptography.hazmat.primitives import hashes, serialization
 from cryptography.hazmat.primitives.asymmetric import ec
+from cryptography.hazmat.primitives.asymmetric.ec import (
+    EllipticCurvePrivateKey,
+    EllipticCurvePublicKey,
+)
 from cryptography.hazmat.primitives.asymmetric.utils import (
     Prehashed,
     encode_dss_signature,
@@ -27,6 +31,7 @@ from ...utils import (
     load_fips_ecdsa_signing_vectors,
     load_kasvs_ecdh_vectors,
     load_nist_vectors,
+    load_rfc6979_vectors,
     load_vectors_from_file,
     raises_unsupported_algorithm,
 )
@@ -508,6 +513,68 @@ class TestECDSAVectors:
                         signature, vector["message"], ec.ECDSA(hash_type())
                     )
 
+    def test_unsupported_deterministic_nonce(self, backend):
+        if backend.ecdsa_deterministic_supported():
+            pytest.skip(
+                f"ECDSA deterministic signing is supported by this"
+                f" backend {backend}"
+            )
+        with pytest.raises(exceptions.UnsupportedAlgorithm):
+            ec.ECDSA(hashes.SHA256(), deterministic_signing=True)
+
+    def test_deterministic_nonce(self, backend, subtests):
+        if not backend.ecdsa_deterministic_supported():
+            pytest.skip(
+                f"ECDSA deterministic signing is not supported by this"
+                f" backend {backend}"
+            )
+
+        supported_hash_algorithms = {
+            "SHA1": hashes.SHA1(),
+            "SHA224": hashes.SHA224(),
+            "SHA256": hashes.SHA256(),
+            "SHA384": hashes.SHA384(),
+            "SHA512": hashes.SHA512(),
+        }
+        vectors = load_vectors_from_file(
+            os.path.join(
+                "asymmetric", "ECDSA", "RFC6979", "evppkey_ecdsa_rfc6979.txt"
+            ),
+            load_rfc6979_vectors,
+        )
+
+        for vector in vectors:
+            with subtests.test():
+                input = bytes(vector["input"], "utf-8")
+                output = bytes.fromhex(vector["output"])
+                key = bytes("\n".join(vector["key"]), "utf-8")
+                if "digest_sign" in vector:
+                    algorithm = vector["digest_sign"]
+                    hash_algorithm = supported_hash_algorithms[algorithm]
+                    algorithm = ec.ECDSA(
+                        hash_algorithm,
+                        deterministic_signing=vector["deterministic_nonce"],
+                    )
+                    private_key = serialization.load_pem_private_key(
+                        key, password=None
+                    )
+                    assert isinstance(private_key, EllipticCurvePrivateKey)
+                    signature = private_key.sign(input, algorithm)
+                    assert signature == output
+                else:
+                    assert "digest_verify" in vector
+                    algorithm = vector["digest_verify"]
+                    assert algorithm in supported_hash_algorithms
+                    hash_algorithm = supported_hash_algorithms[algorithm]
+                    algorithm = ec.ECDSA(hash_algorithm)
+                    public_key = serialization.load_pem_public_key(key)
+                    assert isinstance(public_key, EllipticCurvePublicKey)
+                    if vector["verify_error"]:
+                        with pytest.raises(exceptions.InvalidSignature):
+                            public_key.verify(output, input, algorithm)
+                    else:
+                        public_key.verify(output, input, algorithm)
+
     def test_sign(self, backend):
         _skip_curve_unsupported(backend, ec.SECP256R1())
         message = b"one little message"
diff --git a/tests/utils.py b/tests/utils.py
index 595e8dc..c1aa34e 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -701,6 +701,57 @@ def load_kasvs_ecdh_vectors(vector_data):
     return vectors
 
 
+def load_rfc6979_vectors(vector_data):
+    """
+    Loads data out of the ECDSA and DSA RFC6979 vector files.
+    """
+    vectors = []
+    keys: typing.Dict[str, typing.List[str]] = dict()
+    reading_key = False
+    current_key_name = None
+
+    data: typing.Dict[str, object] = dict()
+    for line in vector_data:
+        line = line.strip()
+
+        if reading_key and current_key_name:
+            keys[current_key_name].append(line)
+            if line.startswith("-----END"):
+                reading_key = False
+                current_key_name = None
+
+        if line.startswith("PrivateKey=") or line.startswith("PublicKey="):
+            reading_key = True
+            current_key_name = line.split("=")[1].strip()
+            keys[current_key_name] = []
+        elif line.startswith("DigestSign = "):
+            data["digest_sign"] = line.split("=")[1].strip()
+            data["deterministic_nonce"] = False
+        elif line.startswith("DigestVerify = "):
+            data["digest_verify"] = line.split("=")[1].strip()
+            data["verify_error"] = False
+        elif line.startswith("Key = "):
+            key_name = line.split("=")[1].strip()
+            assert key_name in keys
+            data["key"] = keys[key_name]
+        elif line.startswith("NonceType = "):
+            nonce_type = line.split("=")[1].strip()
+            data["deterministic_nonce"] = nonce_type == "deterministic"
+        elif line.startswith("Input = "):
+            data["input"] = line.split("=")[1].strip(' "')
+        elif line.startswith("Output = "):
+            data["output"] = line.split("=")[1].strip()
+        elif line.startswith("Result = "):
+            data["verify_error"] = line.split("=")[1].strip() == "VERIFY_ERROR"
+
+        elif not line:
+            if data:
+                vectors.append(data)
+                data = {}
+
+    return vectors
+
+
 def load_x963_vectors(vector_data):
     """
     Loads data out of the X9.63 vector data