lib/crypto: tests: Add KUnit tests for CBC-based MACs

Add a KUnit test suite for the AES-CMAC, AES-XCBC-MAC, and AES-CBC-MAC
library functions.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20260218213501.136844-7-ebiggers@kernel.org
Link: https://lore.kernel.org/r/20260306001917.24105-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

scripts/crypto/gen-hash-testvecs.py

@@ -3,8 +3,12 @@
 #
 # Script that generates test vectors for the given hash function.
 #
+# Requires that python-cryptography be installed.
+#
 # Copyright 2025 Google LLC
 
+import cryptography.hazmat.primitives.ciphers
+import cryptography.hazmat.primitives.cmac
 import hashlib
 import hmac
 import sys
@@ -24,6 +28,20 @@ def rand_bytes(length):
         out.append((seed >> 16) % 256)
     return bytes(out)
 
+AES_256_KEY_SIZE = 32
+
+# AES-CMAC.  Just wraps the implementation from python-cryptography.
+class AesCmac:
+    def __init__(self, key):
+        aes = cryptography.hazmat.primitives.ciphers.algorithms.AES(key)
+        self.cmac = cryptography.hazmat.primitives.cmac.CMAC(aes)
+
+    def update(self, data):
+        self.cmac.update(data)
+
+    def digest(self):
+        return self.cmac.finalize()
+
 POLY1305_KEY_SIZE = 32
 
 # A straightforward, unoptimized implementation of Poly1305.
@@ -80,9 +98,12 @@ class Polyval:
         return self.acc.to_bytes(16, byteorder='little')
 
 def hash_init(alg):
+    # The keyed hash functions are assigned a fixed random key here, to present
+    # them as unkeyed hash functions.  This allows all the test cases for
+    # unkeyed hash functions to work on them.
+    if alg == 'aes-cmac':
+        return AesCmac(rand_bytes(AES_256_KEY_SIZE))
     if alg == 'poly1305':
-        # Use a fixed random key here, to present Poly1305 as an unkeyed hash.
-        # This allows all the test cases for unkeyed hashes to work on Poly1305.
         return Poly1305(rand_bytes(POLY1305_KEY_SIZE))
     if alg == 'polyval':
         return Polyval(rand_bytes(POLYVAL_BLOCK_SIZE))
@@ -116,6 +137,8 @@ def print_c_struct_u8_array_field(name, value):
     print('\t\t},')
 
 def alg_digest_size_const(alg):
+    if alg == 'aes-cmac':
+        return 'AES_BLOCK_SIZE'
     if alg.startswith('blake2'):
         return f'{alg.upper()}_HASH_SIZE'
     return f"{alg.upper().replace('-', '_')}_DIGEST_SIZE"
@@ -252,7 +275,9 @@ if len(sys.argv) != 2:
 alg = sys.argv[1]
 print('/* SPDX-License-Identifier: GPL-2.0-or-later */')
 print(f'/* This file was generated by: {sys.argv[0]} {" ".join(sys.argv[1:])} */')
-if alg.startswith('blake2'):
+if alg == 'aes-cmac':
+    gen_unkeyed_testvecs(alg)
+elif alg.startswith('blake2'):
     gen_unkeyed_testvecs(alg)
     gen_additional_blake2_testvecs(alg)
 elif alg == 'nh':