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106 lines
3.4 KiB
106 lines
3.4 KiB
=pod |
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=head1 NAME |
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HMAC, HMAC_Init, HMAC_Update, HMAC_Final, HMAC_cleanup - HMAC message |
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authentication code |
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=head1 SYNOPSIS |
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#include <openssl/hmac.h> |
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unsigned char *HMAC(const EVP_MD *evp_md, const void *key, |
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int key_len, const unsigned char *d, int n, |
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unsigned char *md, unsigned int *md_len); |
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void HMAC_CTX_init(HMAC_CTX *ctx); |
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int HMAC_Init(HMAC_CTX *ctx, const void *key, int key_len, |
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const EVP_MD *md); |
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int HMAC_Init_ex(HMAC_CTX *ctx, const void *key, int key_len, |
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const EVP_MD *md, ENGINE *impl); |
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int HMAC_Update(HMAC_CTX *ctx, const unsigned char *data, int len); |
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int HMAC_Final(HMAC_CTX *ctx, unsigned char *md, unsigned int *len); |
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void HMAC_CTX_cleanup(HMAC_CTX *ctx); |
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void HMAC_cleanup(HMAC_CTX *ctx); |
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=head1 DESCRIPTION |
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HMAC is a MAC (message authentication code), i.e. a keyed hash |
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function used for message authentication, which is based on a hash |
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function. |
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HMAC() computes the message authentication code of the B<n> bytes at |
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B<d> using the hash function B<evp_md> and the key B<key> which is |
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B<key_len> bytes long. |
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It places the result in B<md> (which must have space for the output of |
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the hash function, which is no more than B<EVP_MAX_MD_SIZE> bytes). |
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If B<md> is NULL, the digest is placed in a static array. The size of |
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the output is placed in B<md_len>, unless it is B<NULL>. |
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B<evp_md> can be EVP_sha1(), EVP_ripemd160() etc. |
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HMAC_CTX_init() initialises a B<HMAC_CTX> before first use. It must be |
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called. |
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HMAC_CTX_cleanup() erases the key and other data from the B<HMAC_CTX> |
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and releases any associated resources. It must be called when an |
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B<HMAC_CTX> is no longer required. |
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HMAC_cleanup() is an alias for HMAC_CTX_cleanup() included for back |
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compatibility with 0.9.6b, it is deprecated. |
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The following functions may be used if the message is not completely |
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stored in memory: |
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HMAC_Init() initializes a B<HMAC_CTX> structure to use the hash |
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function B<evp_md> and the key B<key> which is B<key_len> bytes |
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long. It is deprecated and only included for backward compatibility |
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with OpenSSL 0.9.6b. |
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HMAC_Init_ex() initializes or reuses a B<HMAC_CTX> structure to use |
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the function B<evp_md> and key B<key>. Either can be NULL, in which |
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case the existing one will be reused. HMAC_CTX_init() must have been |
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called before the first use of an B<HMAC_CTX> in this |
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function. B<N.B. HMAC_Init() had this undocumented behaviour in |
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previous versions of OpenSSL - failure to switch to HMAC_Init_ex() in |
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programs that expect it will cause them to stop working>. |
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HMAC_Update() can be called repeatedly with chunks of the message to |
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be authenticated (B<len> bytes at B<data>). |
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HMAC_Final() places the message authentication code in B<md>, which |
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must have space for the hash function output. |
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=head1 RETURN VALUES |
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HMAC() returns a pointer to the message authentication code or NULL if |
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an error occurred. |
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HMAC_Init_ex(), HMAC_Update() and HMAC_Final() return 1 for success or 0 if |
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an error occurred. |
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HMAC_CTX_init() and HMAC_CTX_cleanup() do not return values. |
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=head1 CONFORMING TO |
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RFC 2104 |
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=head1 SEE ALSO |
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L<sha(3)|sha(3)>, L<evp(3)|evp(3)> |
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=head1 HISTORY |
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HMAC(), HMAC_Init(), HMAC_Update(), HMAC_Final() and HMAC_cleanup() |
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are available since SSLeay 0.9.0. |
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HMAC_CTX_init(), HMAC_Init_ex() and HMAC_CTX_cleanup() are available |
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since OpenSSL 0.9.7. |
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HMAC_Init_ex(), HMAC_Update() and HMAC_Final() did not return values in |
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versions of OpenSSL before 1.0.0. |
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=cut
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