106 lines
3.4 KiB
Text
106 lines
3.4 KiB
Text
=pod
|
|
|
|
=head1 NAME
|
|
|
|
HMAC, HMAC_Init, HMAC_Update, HMAC_Final, HMAC_cleanup - HMAC message
|
|
authentication code
|
|
|
|
=head1 SYNOPSIS
|
|
|
|
#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);
|
|
|
|
void HMAC_CTX_init(HMAC_CTX *ctx);
|
|
|
|
int HMAC_Init(HMAC_CTX *ctx, const void *key, int key_len,
|
|
const EVP_MD *md);
|
|
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_cleanup(HMAC_CTX *ctx);
|
|
void HMAC_cleanup(HMAC_CTX *ctx);
|
|
|
|
=head1 DESCRIPTION
|
|
|
|
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 B<n> bytes at
|
|
B<d> using the hash function B<evp_md> and the key B<key> which is
|
|
B<key_len> bytes long.
|
|
|
|
It places the result in B<md> (which must have space for the output of
|
|
the hash function, which is no more than B<EVP_MAX_MD_SIZE> bytes).
|
|
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>.
|
|
|
|
B<evp_md> can be EVP_sha1(), EVP_ripemd160() etc.
|
|
|
|
HMAC_CTX_init() initialises a B<HMAC_CTX> before first use. It must be
|
|
called.
|
|
|
|
HMAC_CTX_cleanup() erases the key and other data from the B<HMAC_CTX>
|
|
and releases any associated resources. It must be called when an
|
|
B<HMAC_CTX> is no longer required.
|
|
|
|
HMAC_cleanup() is an alias for HMAC_CTX_cleanup() included for back
|
|
compatibility with 0.9.6b, it is deprecated.
|
|
|
|
The following functions may be used if the message is not completely
|
|
stored in memory:
|
|
|
|
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. It is deprecated and only included for backward compatibility
|
|
with OpenSSL 0.9.6b.
|
|
|
|
HMAC_Init_ex() initializes or reuses a B<HMAC_CTX> structure to use
|
|
the function B<evp_md> and key B<key>. Either can be NULL, in which
|
|
case the existing one will be reused. HMAC_CTX_init() must have been
|
|
called before the first use of an B<HMAC_CTX> in this
|
|
function. B<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>.
|
|
|
|
HMAC_Update() can be called repeatedly with chunks of the message to
|
|
be authenticated (B<len> bytes at B<data>).
|
|
|
|
HMAC_Final() places the message authentication code in B<md>, which
|
|
must have space for the hash function output.
|
|
|
|
=head1 RETURN VALUES
|
|
|
|
HMAC() returns a pointer to the message authentication code or NULL if
|
|
an error occurred.
|
|
|
|
HMAC_Init_ex(), HMAC_Update() and HMAC_Final() return 1 for success or 0 if
|
|
an error occurred.
|
|
|
|
HMAC_CTX_init() and HMAC_CTX_cleanup() do not return values.
|
|
|
|
=head1 CONFORMING TO
|
|
|
|
RFC 2104
|
|
|
|
=head1 SEE ALSO
|
|
|
|
L<sha(3)|sha(3)>, L<evp(3)|evp(3)>
|
|
|
|
=head1 HISTORY
|
|
|
|
HMAC(), HMAC_Init(), HMAC_Update(), HMAC_Final() and HMAC_cleanup()
|
|
are available since SSLeay 0.9.0.
|
|
|
|
HMAC_CTX_init(), HMAC_Init_ex() and HMAC_CTX_cleanup() are available
|
|
since OpenSSL 0.9.7.
|
|
|
|
HMAC_Init_ex(), HMAC_Update() and HMAC_Final() did not return values in
|
|
versions of OpenSSL before 0.9.9.
|
|
|
|
=cut
|