1 files changed, 8 insertions, 1 deletions

diff --git a/src/lib/libcrypto/cmac/cmac.c b/src/lib/libcrypto/cmac/cmac.c
index f653219b8f..0df40277bc 100644
--- a/src/lib/libcrypto/cmac/cmac.c
+++ b/src/lib/libcrypto/cmac/cmac.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: cmac.c,v 1.16 2023/11/29 21:35:57 tb Exp $ */
+/* $OpenBSD: cmac.c,v 1.17 2023/12/15 13:45:05 tb Exp $ */
 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project.
  */
@@ -191,6 +191,13 @@ CMAC_Init(CMAC_CTX *ctx, const void *key, size_t keylen,
 
         /* Initialise context. */
         if (cipher != NULL) {
+                /*
+                 * Disallow ciphers for which EVP_Cipher() behaves differently.
+                 * These are AEAD ciphers (or AES keywrap) for which the CMAC
+                 * construction makes little sense.
+                 */
+                if ((cipher->flags & EVP_CIPH_FLAG_CUSTOM_CIPHER) != 0)
+                        return 0;
                 if (!EVP_EncryptInit_ex(&ctx->cctx, cipher, NULL, NULL, NULL))
                         return 0;
         }