e_null_hmac.c, build.info, c_allc.c, evp.h: add dummy cipher EVP_enc_…

…null_hmac_sha256, for populating NID.

crypto/evp/build.info

@@ -14,7 +14,7 @@ SOURCE[../../libcrypto]=$COMMON\
         c_allc.c c_alld.c bio_ok.c \
         evp_pkey.c evp_pbe.c p5_crpt.c p5_crpt2.c pbe_scrypt.c \
         e_aes_cbc_hmac_sha1.c e_aes_cbc_hmac_sha256.c e_rc4_hmac_md5.c \
-        e_chacha20_poly1305.c \
+        e_chacha20_poly1305.c e_null_hmac.c \
         legacy_sha.c ctrl_params_translate.c \
         cmeth_lib.c
 

crypto/evp/c_allc.c

@@ -265,4 +265,8 @@ void openssl_add_all_ciphers_int(void)
     EVP_add_cipher(EVP_chacha20_poly1305());
 # endif
 #endif
+
+#ifndef OPENSSL_NO_INTEGRITY_ONLY_CIPHER
+    EVP_add_cipher(EVP_enc_null_hmac_sha256());
+#endif
 }

crypto/evp/e_null_hmac.c

@@ -0,0 +1,42 @@
+/*
+ * Copyright 1995-2021 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include <stdio.h>
+
+#ifndef OPENSSL_NO_INTEGRITY_ONLY_CIPHER
+
+# include <openssl/evp.h>
+# include <openssl/objects.h>
+# include "crypto/evp.h"
+# include "evp_local.h"
+
+static EVP_CIPHER n_cipher = {
+    NID_enull_hmac_sha256,
+    0, 0, 0, 0,
+    EVP_ORIG_GLOBAL,
+    NULL,
+    NULL,
+    NULL,
+    0,
+    NULL,
+    NULL,
+    NULL,
+    NULL
+};
+
+/*
+ * dummy cipher just to populate the NID value.
+ * TODO: look for better way of doing it.
+ */
+const EVP_CIPHER *EVP_enc_null_hmac_sha256(void)
+{
+    return (&n_cipher);
+}
+
+#endif

include/openssl/evp.h

@@ -1138,6 +1138,9 @@ const EVP_CIPHER *EVP_chacha20(void);
 const EVP_CIPHER *EVP_chacha20_poly1305(void);
 #  endif
 # endif
+# ifndef OPENSSL_NO_INTEGRITY_ONLY_CIPHER
+const EVP_CIPHER *EVP_enc_null_hmac_sha256(void);
+# endif
 
 # ifndef OPENSSL_NO_SEED
 const EVP_CIPHER *EVP_seed_ecb(void);