/*
* Copyright (c) 2009 Joshua Oreman <oremanj@rwcr.net>.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
FILE_LICENCE ( GPL2_OR_LATER );
#include <gpxe/crypto.h>
#include <gpxe/sha1.h>
#include <gpxe/hmac.h>
#include <stdint.h>
#include <byteswap.h>
/**
* SHA1 pseudorandom function for creating derived keys
*
* @v key Master key with which this call is associated
* @v key_len Length of key
* @v label NUL-terminated ASCII string describing purpose of PRF data
* @v data Further data that should be included in the PRF
* @v data_len Length of further PRF data
* @v prf_len Bytes of PRF to generate
* @ret 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.
*/
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 )
{
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_SIZE]; /* HMAC-SHA1 result */
u8 sha1_ctx[SHA1_CTX_SIZE]; /* 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, sha1_ctx, keym, &key_len );
hmac_update ( &sha1_algorithm, sha1_ctx, in, sizeof ( in ) );
hmac_final ( &sha1_algorithm, sha1_ctx, keym, &key_len, out );
if ( prf_len <= SHA1_SIZE ) {
memcpy ( prf, out, prf_len );
break;
}
memcpy ( prf, out, SHA1_SIZE );
prf_len -= SHA1_SIZE;
prf += SHA1_SIZE;
}
}
/**
* PBKDF2 key derivation function inner block operation
*
* @v passphrase Passphrase from which to derive key
* @v pass_len Length of passphrase
* @v salt Salt to include in key
* @v salt_len Length of salt
* @v iterations Number of iterations of SHA1 to perform
* @v blocknr Index of this block, starting at 1
* @ret block SHA1_SIZE bytes of PBKDF2 data
*
* The operation of this function is described in RFC 2898.
*/
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 )
{
u8 pass[pass_len]; /* modifiable passphrase */
u8 in[salt_len + 4]; /* input buffer to first round */
u8 last[SHA1_SIZE]; /* output of round N, input of N+1 */
u8 sha1_ctx[SHA1_CTX_SIZE];
u8 *next_in = in; /* changed to `last' after first round */
int next_size = sizeof ( in );
int i, j;
blocknr = htonl ( blocknr );
memcpy ( pass, passphrase, pass_len );
memcpy ( in, salt, salt_len );
memcpy ( in + salt_len, &blocknr, 4 );
memset ( block, 0, SHA1_SIZE );
for ( i = 0; i < iterations; i++ ) {
hmac_init ( &sha1_algorithm, sha1_ctx, pass, &pass_len );
hmac_update ( &sha1_algorithm, sha1_ctx, next_in, next_size );
hmac_final ( &sha1_algorithm, sha1_ctx, pass, &pass_len, last );
for ( j = 0; j < SHA1_SIZE; j++ ) {
block[j] ^= last[j];
}
next_in = last;
next_size = SHA1_SIZE;
}
}
/**
* PBKDF2 key derivation function using SHA1
*
* @v passphrase Passphrase from which to derive key
* @v pass_len Length of passphrase
* @v salt Salt to include in key
* @v salt_len Length of salt
* @v iterations Number of iterations of SHA1 to perform
* @v key_len Length of key to generate
* @ret 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.
*/
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 )
{
u32 blocks = ( key_len + SHA1_SIZE - 1 ) / SHA1_SIZE;
u32 blk;
u8 buf[SHA1_SIZE];
for ( blk = 1; blk <= blocks; blk++ ) {
pbkdf2_sha1_f ( passphrase, pass_len, salt, salt_len,
iterations, blk, buf );
if ( key_len <= SHA1_SIZE ) {
memcpy ( key, buf, key_len );
break;
}
memcpy ( key, buf, SHA1_SIZE );
key_len -= SHA1_SIZE;
key += SHA1_SIZE;
}
}
