Improve SYMKey init (allow setting k and/or key)

Author: jschlyter

pyproject.toml

@@ -74,7 +74,7 @@ select = [
     # isort
     "I",
 ]
-ignore = ["E501", "I001", "SIM102", "UP006", "UP035", "UP045", "UP007"]
+ignore = ["E501", "I001", "SIM102", "UP006", "UP035", "UP045", "UP007", "UP038"]
 exclude = ["examples/*"]
 
 [tool.ruff.lint.isort]

src/cryptojwt/jwk/hmac.py

@@ -59,6 +59,11 @@ def __init__(
             if isinstance(self.k, str):
                 self.k = self.k.encode("utf-8")
             self.key = b64d(bytes(self.k))
+        elif self.key and not self.k:
+            self.k = b64e(self.key)
+
+        if self.k and self.key and self.k != b64e(self.key):
+            raise JWKException("k and key don't match")
 
         if len(self.key) < 16:
             raise UnsupportedAlgorithm("client_secret too short, it should be at least 16 digits")

tests/test_02_jwk.py

@@ -11,6 +11,7 @@
 
 from cryptojwt.exception import (
     DeSerializationNotPossible,
+    JWKException,
     UnsupportedAlgorithm,
     WrongUsage,
 )
@@ -660,6 +661,24 @@ def test_dump_load():
     assert key.use == "sig"
 
 
+def test_key_init():
+    # init with only key
+    secret1 = os.urandom(16)
+    k1 = SYMKey(key=secret1, alg="HS256")
+    assert k1.k == b64e(secret1)
+
+    # init with only k (base64 encoded key)
+    secret2 = os.urandom(16)
+    k2 = SYMKey(k=b64e(secret2), alg="HS256")
+    assert k2.key == secret2
+
+    # init with different key and k should fail
+    secret3a = os.urandom(16)
+    secret3b = os.urandom(16)
+    with pytest.raises(JWKException):
+        _ = SYMKey(k=b64e(secret3a), key=secret3b, alg="HS256")
+
+
 def test_key_ops():
     sk = SYMKey(
         key="df34db91c16613deba460752522d28f6ebc8a73d0d9185836270c26b",