Rename some functions in uacrypto and add comments

opcua/security_policies.py

@@ -249,7 +249,7 @@ class SignerAesCbc(Signer):
         return uacrypto.sha1_size()
 
     def signature(self, data):
-        return uacrypto.hash_hmac(self.key, data)
+        return uacrypto.hmac_sha1(self.key, data)
 
 
 class VerifierAesCbc(Verifier):
@@ -261,7 +261,7 @@ class VerifierAesCbc(Verifier):
         return uacrypto.sha1_size()
 
     def verify(self, data, signature):
-        expected = uacrypto.hash_hmac(self.key, data)
+        expected = uacrypto.hmac_sha1(self.key, data)
         if signature != expected:
             raise uacrypto.InvalidSignature
 
@@ -403,6 +403,7 @@ class SecurityPolicyBasic256(SecurityPolicy):
         self.client_certificate = uacrypto.der_from_x509(client_cert)
 
     def make_symmetric_key(self, nonce1, nonce2):
+        # specs part 6, 6.7.5
         key_sizes = (self.signature_key_size, self.symmetric_key_size, 16)
 
         (sigkey, key, init_vec) = uacrypto.p_sha1(nonce2, nonce1, key_sizes)

opcua/uacrypto.py

@@ -129,7 +129,7 @@ def cipher_decrypt(cipher, data):
     return decryptor.update(data) + decryptor.finalize()
 
 
-def hash_hmac(key, message):
+def hmac_sha1(key, message):
     hasher = hmac.HMAC(key, hashes.SHA1(), backend=default_backend())
     hasher.update(message)
     return hasher.finalize()
@@ -139,9 +139,10 @@ def sha1_size():
     return hashes.SHA1.digest_size
 
 
-def p_sha1(key, body, sizes=()):
+def p_sha1(secret, seed, sizes=()):
     """
-    Derive one or more keys from key and body.
+    Derive one or more keys from secret and seed.
+    (See specs part 6, 6.7.5 and RFC 2246 - TLS v1.0)
     Lengths of keys will match sizes argument
     """
     full_size = 0
@@ -149,10 +150,10 @@ def p_sha1(key, body, sizes=()):
         full_size += size
 
     result = b''
-    accum = body
+    accum = seed
     while len(result) < full_size:
-        accum = hash_hmac(key, accum)
-        result += hash_hmac(key, accum + body)
+        accum = hmac_sha1(secret, accum)
+        result += hmac_sha1(secret, accum + seed)
 
     parts = []
     for size in sizes: