1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
|
=pod
=head1 NAME
HMAC, HMAC_CTX_new, HMAC_CTX_reset, HMAC_CTX_free, HMAC_Init, HMAC_Init_ex, HMAC_Update, HMAC_Final - 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);
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);
Deprecated:
#if OPENSSL_API_COMPAT < 0x10100000L
int HMAC_Init(HMAC_CTX *ctx, const void *key, int key_len,
const EVP_MD *md);
#endif
=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_new() creates a new HMAC_CTX in heap memory.
HMAC_CTX_reset() zeroes an existing B<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 B<HMAC_CTX>,
releases any associated resources and finally frees the B<HMAC_CTX>
itself.
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. B<ctx> must have been created
with HMAC_CTX_new() 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_CTX_new() returns a pointer to a new B<HMAC_CTX> on success or
B<NULL> if an error occurred.
HMAC_CTX_reset(), HMAC_Init_ex(), HMAC_Update() and HMAC_Final() return 1
for success or 0 if an error occurred.
HMAC_CTX_free() do not return values.
=head1 CONFORMING TO
RFC 2104
=head1 SEE ALSO
L<sha(3)>, L<evp(3)>
=head1 HISTORY
HMAC_CTX_init() was replaced with HMAC_CTX_reset() in OpenSSL versions 1.1.
HMAC_CTX_cleanup() existed in OpenSSL versions before 1.1.
HMAC_CTX_new() and HMAC_CTX_free() are new in OpenSSL version 1.1.
HMAC_Init_ex(), HMAC_Update() and HMAC_Final() did not return values in
versions of OpenSSL before 1.0.0.
=cut
|
