lib/crypto: tests: Add KUnit test suite for AES-CCM

Add a KUnit test suite for the AES-CCM library API.

It consists of:

- All the shared test cases from aead-test-template.h.  These include
  extensive consistency tests, a "Monte-Carlo test", and a benchmark.

- Tests against hardcoded AES-CCM test vectors from external sources.

- Tests for CCM-specific message length validation.

To generate the expected aes_ccm_monte_carlo_checksum[] value, add a
script gen-aead-testvecs.py which computes it using python-cryptography.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://patch.msgid.link/20260802233005.161467-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

scripts/crypto/gen-aead-testvecs.py

@@ -0,0 +1,60 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Script that generates known-good data used in the AEAD tests.
+#
+# Requires that python-cryptography be installed.
+#
+# Copyright 2026 Google LLC
+
+import hashlib
+import sys
+import cryptography.hazmat.primitives.ciphers.aead
+
+
+# Deterministically generate 'length' random bytes.
+def rand_bytes(length):
+    seed = length
+    out = []
+    for _ in range(length):
+        seed = (seed * 25214903917 + 11) % 2**48
+        out.append((seed >> 16) % 256)
+    return bytes(out)
+
+
+# Deterministically generate many different AEAD inputs using exactly the same
+# method that the test uses; encrypt them using an independent implementation of
+# the algorithm; compute the checksum of all the resulting (ciphertext, authtag)
+# pairs concatenated to each other; and print the checksum as a C struct.
+def gen_monte_carlo_checksum(alg):
+    blake2s = hashlib.blake2s()
+    for data_len in range(1025):
+        ad_len = data_len % 293
+        pt = rand_bytes(data_len)
+        ad = rand_bytes(ad_len)
+        if alg == "aes-ccm":
+            key_len = [16, 24, 32][data_len % 3]
+            key = rand_bytes(key_len)
+            nonce = rand_bytes([7, 8, 9, 10, 11, 12, 13][data_len % 7])
+            tag_len = [4, 6, 8, 10, 12, 14, 16][data_len % 7]
+            ccm = cryptography.hazmat.primitives.ciphers.aead.AESCCM(
+                key, tag_length=tag_len
+            )
+            ct_and_tag = ccm.encrypt(nonce, pt, ad)
+
+        blake2s.update(ct_and_tag)
+
+    name = f"{alg.replace('-', '_')}_monte_carlo_checksum"
+    value = blake2s.digest()
+    print(f"static const u8 {name}[BLAKE2S_HASH_SIZE] = {{")
+    for i in range(0, len(value), 11):
+        line = "\t" + "".join(f"0x{b:02x}, " for b in value[i : i + 11])
+        print(f"{line.rstrip()}")
+    print("};")
+
+
+if len(sys.argv) != 2 or sys.argv[1] not in ("aes-ccm"):
+    sys.stderr.write("Usage: gen-aead-testvecs.py [aes-ccm]\n")
+    sys.exit(1)
+
+gen_monte_carlo_checksum(sys.argv[1])