HMAC, HMAC_CTX_new, HMAC_CTX_reset, HMAC_CTX_free, HMAC_Init, HMAC_Init_ex, HMAC_Update, HMAC_Final, HMAC_CTX_copy, HMAC_CTX_set_flags, HMAC_CTX_get_md - HMAC message authentication code
#include <openssl/hmac.h>
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);
HMAC_CTX *HMAC_CTX_new(void); int HMAC_CTX_reset(HMAC_CTX *ctx);
int HMAC_Init_ex(HMAC_CTX *ctx, const void *key, int key_len, const EVP_MD *md, ENGINE *impl); int HMAC_Update(HMAC_CTX *ctx, const unsigned char *data, int len); int HMAC_Final(HMAC_CTX *ctx, unsigned char *md, unsigned int *len);
void HMAC_CTX_free(HMAC_CTX *ctx);
int HMAC_CTX_copy(HMAC_CTX *dctx, HMAC_CTX *sctx); void HMAC_CTX_set_flags(HMAC_CTX *ctx, unsigned long flags); const EVP_MD *HMAC_CTX_get_md(const HMAC_CTX *ctx);
Deprecated:
#if OPENSSL_API_COMPAT < 0x10100000L int HMAC_Init(HMAC_CTX *ctx, const void *key, int key_len, const EVP_MD *md); #endif
HMAC is a MAC (message authentication code), i.e. a keyed hash function used for message authentication, which is based on a hash function.
HMAC()
computes the message authentication code of the n bytes at
d using the hash function evp_md and the key key which is
key_len bytes long.
It places the result in md (which must have space for the output of the hash function, which is no more than EVP_MAX_MD_SIZE bytes). If md is NULL, the digest is placed in a static array. The size of the output is placed in md_len, unless it is NULL. Note: passing a NULL value for md to use the static array is not thread safe.
evp_md can be EVP_sha1(), EVP_ripemd160() etc.
HMAC_CTX_new()
creates a new HMAC_CTX in heap memory.
HMAC_CTX_reset()
zeroes an existing HMAC_CTX and associated
resources, making it suitable for new computations as if it was newly
created with HMAC_CTX_new()
.
HMAC_CTX_free()
erases the key and other data from the HMAC_CTX,
releases any associated resources and finally frees the HMAC_CTX
itself.
The following functions may be used if the message is not completely stored in memory:
HMAC_Init()
initializes a HMAC_CTX structure to use the hash
function evp_md and the key key which is key_len bytes
long. It is deprecated and only included for backward compatibility
with OpenSSL 0.9.6b.
HMAC_Init_ex()
initializes or reuses a HMAC_CTX structure to use the hash
function evp_md and key key. If both are NULL (or evp_md is the same
as the previous digest used by ctx and key is NULL) the existing key is
reused. ctx must have been created with HMAC_CTX_new()
before the first use
of an HMAC_CTX in this function. N.B. HMAC_Init() had this undocumented
behaviour in previous versions of OpenSSL - failure to switch to HMAC_Init_ex()
in programs that expect it will cause them to stop working.
NOTE: If HMAC_Init_ex()
is called with key NULL and evp_md is not the
same as the previous digest used by ctx then an error is returned
because reuse of an existing key with a different digest is not supported.
HMAC_Update()
can be called repeatedly with chunks of the message to
be authenticated (len bytes at data).
HMAC_Final()
places the message authentication code in md, which
must have space for the hash function output.
HMAC_CTX_copy()
copies all of the internal state from sctx into dctx.
HMAC_CTX_set_flags()
applies the specified flags to the internal EVP_MD_CTXs.
These flags have the same meaning as for EVP_MD_CTX_set_flags(3).
HMAC_CTX_get_md()
returns the EVP_MD that has previously been set for the
supplied HMAC_CTX.
HMAC()
returns a pointer to the message authentication code or NULL if
an error occurred.
HMAC_CTX_new()
returns a pointer to a new HMAC_CTX on success or
NULL if an error occurred.
HMAC_CTX_reset()
, HMAC_Init_ex()
, HMAC_Update()
, HMAC_Final()
and
HMAC_CTX_copy()
return 1 for success or 0 if an error occurred.
HMAC_CTX_get_md()
return the EVP_MD previously set for the supplied HMAC_CTX or
NULL if no EVP_MD has been set.
RFC 2104
sha(3), evp(3)
HMAC_CTX_init()
was replaced with HMAC_CTX_reset()
in OpenSSL versions 1.1.0.
HMAC_CTX_cleanup()
existed in OpenSSL versions before 1.1.0.
HMAC_CTX_new()
, HMAC_CTX_free()
and HMAC_CTX_get_md()
are new in OpenSSL version
1.1.0.
HMAC_Init_ex()
, HMAC_Update()
and HMAC_Final()
did not return values in
versions of OpenSSL before 1.0.0.
Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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.