Deprecate the low level HMAC functions

[openssl.git] / doc / man3 / HMAC.pod

diff --git a/doc/man3/HMAC.pod b/doc/man3/HMAC.pod
index 5aed367a4756527827b3ad90f92ce2d7217ab1f0..54db3ad66dbba078ea1943fe8624c738cbaeee03 100644 (file)
--- a/doc/man3/HMAC.pod
+++ b/doc/man3/HMAC.pod
@@ -20,6 +20,10 @@ HMAC_size
 
  #include <openssl/hmac.h>
 
+Deprecated since OpenSSL 3.0, can be hidden entirely by defining
+B<OPENSSL_API_COMPAT> with a suitable version value, see
+L<openssl_user_macros(7)>:
+
  unsigned char *HMAC(const EVP_MD *evp_md, const void *key,
                      int key_len, const unsigned char *d, int n,
                      unsigned char *md, unsigned int *md_len);
@@ -49,6 +53,10 @@ L<openssl_user_macros(7)>:
 
 =head1 DESCRIPTION
 
+All of the functions described on this page are deprecated. Applications should
+instead use L<EVP_MAC_CTX_new(3)>, L<EVP_MAC_CTX_free(3)>, L<EVP_MAC_init(3)>,
+L<EVP_MAC_update(3)> and L<EVP_MAC_final(3)>.
+
 HMAC is a MAC (message authentication code), i.e. a keyed hash
 function used for message authentication, which is based on a hash
 function.
@@ -63,11 +71,13 @@ If B<md> is NULL, the digest is placed in a static array.  The size of
 the output is placed in B<md_len>, unless it is B<NULL>. Note: passing a NULL
 value for B<md>  to use the static array is not thread safe.
 
-B<evp_md> can be EVP_sha1(), EVP_ripemd160() etc.
+B<evp_md> is a message digest such as EVP_sha1(), EVP_ripemd160() etc. HMAC does
+not support variable output length digests such as EVP_shake128() and
+EVP_shake256().
 
 HMAC_CTX_new() creates a new HMAC_CTX in heap memory.
 
-HMAC_CTX_reset() zeroes an existing B<HMAC_CTX> and associated
+HMAC_CTX_reset() clears an existing B<HMAC_CTX> and associated
 resources, making it suitable for new computations as if it was newly
 created with HMAC_CTX_new().
 
@@ -91,7 +101,7 @@ because reuse of an existing key with a different digest is not supported.
 
 HMAC_Init() initializes a B<HMAC_CTX> structure to use the hash
 function B<evp_md> and the key B<key> which is B<key_len> bytes
-long. 
+long.
 
 HMAC_Update() can be called repeatedly with chunks of the message to
 be authenticated (B<len> bytes at B<data>).
@@ -136,6 +146,8 @@ L<SHA1(3)>, L<evp(7)>
 
 =head1 HISTORY
 
+All of these functions were deprecated in OpenSSL 3.0.
+
 HMAC_CTX_init() was replaced with HMAC_CTX_reset() in OpenSSL 1.1.0.
 
 HMAC_CTX_cleanup() existed in OpenSSL before version 1.1.0.
@@ -149,7 +161,7 @@ OpenSSL before version 1.0.0.
 
 Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
 
-Licensed under the OpenSSL license (the "License").  You may not use
+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
 L<https://www.openssl.org/source/license.html>.