/* * Copyright (c) 2009 Joshua Oreman . * * 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 #include #include #include #include /** * 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; } }