hmac.c File Reference

Keyed-Hashing for Message Authentication. More...

#include <string.h>
#include <assert.h>
#include <gpxe/crypto.h>
#include <gpxe/hmac.h>

Go to the source code of this file.

Functions
	FILE_LICENCE (GPL2_OR_LATER)
static void	hmac_reduce_key (struct digest_algorithm *digest, void *key, size_t *key_len)
	Reduce HMAC key length.
void	hmac_init (struct digest_algorithm *digest, void *digest_ctx, void *key, size_t *key_len)
	Initialise HMAC.
void	hmac_final (struct digest_algorithm *digest, void *digest_ctx, void *key, size_t *key_len, void *hmac)
	Finalise HMAC.

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Detailed Description

Keyed-Hashing for Message Authentication.

Definition in file hmac.c.

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Function Documentation

FILE_LICENCE

(

GPL2_OR_LATER

)

static void hmac_reduce_key	(	struct digest_algorithm *	digest,
		void *	key,
		size_t *	key_len
	)			[static]

Reduce HMAC key length.

Parameters:

	digest	Digest algorithm to use
	digest_ctx	Digest context
	key	Key
	key_len	Length of key

Definition at line 40 of file hmac.c.

References digest_algorithm::ctxsize, digest_final(), digest_init(), digest_update(), and digest_algorithm::digestsize.

Referenced by hmac_final(), and hmac_init().

                                                           {
        uint8_t digest_ctx[digest->ctxsize];

        digest_init ( digest, digest_ctx );
        digest_update ( digest, digest_ctx, key, *key_len );
        digest_final ( digest, digest_ctx, key );
        *key_len = digest->digestsize;
}

void hmac_init	(	struct digest_algorithm *	digest,
		void *	digest_ctx,
		void *	key,
		size_t *	key_len
	)

Initialise HMAC.

Parameters:

	digest	Digest algorithm to use
	digest_ctx	Digest context
	key	Key
	key_len	Length of key

The length of the key should be less than the block size of the digest algorithm being used. (If the key length is greater, it will be replaced with its own digest, and key_len will be updated accordingly).

Definition at line 63 of file hmac.c.

References digest_algorithm::blocksize, digest_init(), digest_update(), hmac_reduce_key(), memcpy, and memset().

Referenced by ccmp_kie_mic(), pbkdf2_sha1_f(), prf_sha1(), tkip_kie_mic(), tls_hmac(), tls_p_hash_va(), and wpa_check_pmkid().

                                              {
        unsigned char k_ipad[digest->blocksize];
        unsigned int i;

        /* Reduce key if necessary */
        if ( *key_len > sizeof ( k_ipad ) )
                hmac_reduce_key ( digest, key, key_len );

        /* Construct input pad */
        memset ( k_ipad, 0, sizeof ( k_ipad ) );
        memcpy ( k_ipad, key, *key_len );
        for ( i = 0 ; i < sizeof ( k_ipad ) ; i++ ) {
                k_ipad[i] ^= 0x36;
        }
        
        /* Start inner hash */
        digest_init ( digest, digest_ctx );
        digest_update ( digest, digest_ctx, k_ipad, sizeof ( k_ipad ) );
}

void hmac_final	(	struct digest_algorithm *	digest,
		void *	digest_ctx,
		void *	key,
		size_t *	key_len,
		void *	hmac
	)

Finalise HMAC.

Parameters:

	digest	Digest algorithm to use
	digest_ctx	Digest context
	key	Key
	key_len	Length of key
	hmac	HMAC digest to fill in

The length of the key should be less than the block size of the digest algorithm being used. (If the key length is greater, it will be replaced with its own digest, and key_len will be updated accordingly).

Definition at line 98 of file hmac.c.

References digest_algorithm::blocksize, digest_final(), digest_init(), digest_update(), digest_algorithm::digestsize, hmac_reduce_key(), memcpy, and memset().

Referenced by ccmp_kie_mic(), pbkdf2_sha1_f(), prf_sha1(), tkip_kie_mic(), tls_hmac(), tls_p_hash_va(), and wpa_check_pmkid().

                                                           {
        unsigned char k_opad[digest->blocksize];
        unsigned int i;

        /* Reduce key if necessary */
        if ( *key_len > sizeof ( k_opad ) )
                hmac_reduce_key ( digest, key, key_len );

        /* Construct output pad */
        memset ( k_opad, 0, sizeof ( k_opad ) );
        memcpy ( k_opad, key, *key_len );
        for ( i = 0 ; i < sizeof ( k_opad ) ; i++ ) {
                k_opad[i] ^= 0x5c;
        }
        
        /* Finish inner hash */
        digest_final ( digest, digest_ctx, hmac );

        /* Perform outer hash */
        digest_init ( digest, digest_ctx );
        digest_update ( digest, digest_ctx, k_opad, sizeof ( k_opad ) );
        digest_update ( digest, digest_ctx, hmac, digest->digestsize );
        digest_final ( digest, digest_ctx, hmac );
}