sha1extra.c File Reference

#include <string.h>
#include <ipxe/crypto.h>
#include <ipxe/sha1.h>
#include <ipxe/hmac.h>
#include <stdint.h>
#include <byteswap.h>

Go to the source code of this file.

Functions
	FILE_LICENCE (GPL2_OR_LATER)
void	prf_sha1 (const void *key, size_t key_len, const char *label, const void *data, size_t data_len, void *prf, size_t prf_len)
	SHA1 pseudorandom function for creating derived keys. More...
static void	pbkdf2_sha1_f (const void *passphrase, size_t pass_len, const void *salt, size_t salt_len, int iterations, u32 blocknr, u8 *block)
	PBKDF2 key derivation function inner block operation. More...
void	pbkdf2_sha1 (const void *passphrase, size_t pass_len, const void *salt, size_t salt_len, int iterations, void *key, size_t key_len)
	PBKDF2 key derivation function using SHA1. More...

Function Documentation

FILE_LICENCE()

FILE_LICENCE

(

GPL2_OR_LATER

)

prf_sha1()

void prf_sha1	(	const void *	key,
		size_t	key_len,
		const char *	label,
		const void *	data,
		size_t	data_len,
		void *	prf,
		size_t	prf_len
	)

SHA1 pseudorandom function for creating derived keys.

Parameters

key	Master key with which this call is associated
key_len	Length of key
label	NUL-terminated ASCII string describing purpose of PRF data
data	Further data that should be included in the PRF
data_len	Length of further PRF data
prf_len	Bytes of PRF to generate

Return values

prf	Pseudorandom function bytes

This is the PRF variant used by 802.11, defined in IEEE 802.11-2007 8.5.5.1. EAP-FAST uses a different SHA1-based PRF, and TLS uses an MD5-based PRF.

Definition at line 44 of file sha1extra.c.

{
        u32 blk;
        u8 keym[key_len];       /* modifiable copy of key */
        u8 in[strlen ( label ) + 1 + data_len + 1]; /* message to HMAC */
        u8 *in_blknr;           /* pointer to last byte of in, block number */
        u8 out[SHA1_DIGEST_SIZE]; /* HMAC-SHA1 result */
        u8 ctx[SHA1_CTX_SIZE + SHA1_BLOCK_SIZE]; /* HMAC-SHA1 context */
        const size_t label_len = strlen ( label );

        /* The HMAC-SHA-1 is calculated using the given key on the
           message text `label', followed by a NUL, followed by one
           byte indicating the block number (0 for first). */

        memcpy ( keym, key, key_len );

        memcpy ( in, label, strlen ( label ) + 1 );
        memcpy ( in + label_len + 1, data, data_len );
        in_blknr = in + label_len + 1 + data_len;

        for ( blk = 0 ;; blk++ ) {
                *in_blknr = blk;

                hmac_init ( &sha1_algorithm, ctx, keym, key_len );
                hmac_update ( &sha1_algorithm, ctx, in, sizeof ( in ) );
                hmac_final ( &sha1_algorithm, ctx, out );

                if ( prf_len <= sizeof ( out ) ) {
                        memcpy ( prf, out, prf_len );
                        break;
                }

                memcpy ( prf, out, sizeof ( out ) );
                prf_len -= sizeof ( out );
                prf += sizeof ( out );
        }
}

References ctx, data, data_len, hmac_final(), hmac_init(), hmac_update(), in, key, memcpy(), out, sha1_algorithm, SHA1_BLOCK_SIZE, SHA1_CTX_SIZE, SHA1_DIGEST_SIZE, and strlen().

Referenced by wpa_derive_ptk().

pbkdf2_sha1_f()

static void pbkdf2_sha1_f ( const void *  passphrase, size_t  pass_len, const void *  salt, size_t  salt_len, int  iterations, u32  blocknr, u8 *  block  )

static

PBKDF2 key derivation function inner block operation.

Parameters

passphrase	Passphrase from which to derive key
pass_len	Length of passphrase
salt	Salt to include in key
salt_len	Length of salt
iterations	Number of iterations of SHA1 to perform
blocknr	Index of this block, starting at 1

Return values

block

SHA1_SIZE bytes of PBKDF2 data

The operation of this function is described in RFC 2898.

Definition at line 96 of file sha1extra.c.

{
        u8 pass[pass_len];      /* modifiable passphrase */
        u8 in[salt_len + 4];    /* input buffer to first round */
        u8 last[SHA1_DIGEST_SIZE]; /* output of round N, input of N+1 */
        u8 ctx[SHA1_CTX_SIZE + SHA1_BLOCK_SIZE];
        u8 *next_in = in;       /* changed to `last' after first round */
        int next_size = sizeof ( in );
        int i;
        unsigned int j;

        blocknr = htonl ( blocknr );

        memcpy ( pass, passphrase, pass_len );
        memcpy ( in, salt, salt_len );
        memcpy ( in + salt_len, &blocknr, 4 );
        memset ( block, 0, sizeof ( last ) );

        for ( i = 0; i < iterations; i++ ) {
                hmac_init ( &sha1_algorithm, ctx, pass, pass_len );
                hmac_update ( &sha1_algorithm, ctx, next_in, next_size );
                hmac_final ( &sha1_algorithm, ctx, last );

                for ( j = 0; j < sizeof ( last ); j++ ) {
                        block[j] ^= last[j];
                }

                next_in = last;
                next_size = sizeof ( last );
        }
}

References block, ctx, hmac_final(), hmac_init(), hmac_update(), htonl, in, memcpy(), memset(), sha1_algorithm, SHA1_BLOCK_SIZE, SHA1_CTX_SIZE, and SHA1_DIGEST_SIZE.

Referenced by pbkdf2_sha1().

pbkdf2_sha1()

void pbkdf2_sha1	(	const void *	passphrase,
		size_t	pass_len,
		const void *	salt,
		size_t	salt_len,
		int	iterations,
		void *	key,
		size_t	key_len
	)

PBKDF2 key derivation function using SHA1.

Parameters

passphrase	Passphrase from which to derive key
pass_len	Length of passphrase
salt	Salt to include in key
salt_len	Length of salt
iterations	Number of iterations of SHA1 to perform
key_len	Length of key to generate

Return values

key	Generated key bytes

This is used most notably in 802.11 WPA passphrase hashing, in which case the salt is the SSID, 4096 iterations are used, and a 32-byte key is generated that serves as the Pairwise Master Key for EAPOL authentication.

The operation of this function is further described in RFC 2898.

Definition at line 148 of file sha1extra.c.

{
        u32 blocks = ( key_len + SHA1_DIGEST_SIZE - 1 ) / SHA1_DIGEST_SIZE;
        u32 blk;
        u8 buf[SHA1_DIGEST_SIZE];

        for ( blk = 1; blk <= blocks; blk++ ) {
                pbkdf2_sha1_f ( passphrase, pass_len, salt, salt_len,
                                iterations, blk, buf );
                if ( key_len <= sizeof ( buf ) ) {
                        memcpy ( key, buf, key_len );
                        break;
                }

                memcpy ( key, buf, sizeof ( buf ) );
                key_len -= sizeof ( buf );
                key += sizeof ( buf );
        }
}

References key, memcpy(), pbkdf2_sha1_f(), and SHA1_DIGEST_SIZE.

Referenced by wpa_psk_start().