/*
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* SHA1-based key derivation function (PBKDF2) for IEEE 802.11i
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* Copyright (c) 2003-2005, Jouni Malinen <j@w1.fi>
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*
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* This software may be distributed under the terms of the BSD license.
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* See README for more details.
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*/
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#include "sha1.h"
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static int pbkdf2_sha1_f(const char *passphrase, const u8 *ssid,
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size_t ssid_len, int iterations, unsigned int count,
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u8 *digest)
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{
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unsigned char tmp[SHA1_MAC_LEN], tmp2[SHA1_MAC_LEN];
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int i, j;
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unsigned char count_buf[4];
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const u8 *addr[2];
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size_t len[2];
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size_t passphrase_len = os_strlen(passphrase);
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addr[0] = ssid;
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len[0] = ssid_len;
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addr[1] = count_buf;
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len[1] = 4;
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/* F(P, S, c, i) = U1 xor U2 xor ... Uc
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* U1 = PRF(P, S || i)
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* U2 = PRF(P, U1)
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* Uc = PRF(P, Uc-1)
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*/
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count_buf[0] = (count >> 24) & 0xff;
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count_buf[1] = (count >> 16) & 0xff;
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count_buf[2] = (count >> 8) & 0xff;
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count_buf[3] = count & 0xff;
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if (hmac_sha1_vector((u8 *) passphrase, passphrase_len, 2, addr, len,
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tmp))
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return -1;
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os_memcpy(digest, tmp, SHA1_MAC_LEN);
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for (i = 1; i < iterations; i++) {
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if (hmac_sha1((u8 *) passphrase, passphrase_len, tmp,
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SHA1_MAC_LEN, tmp2))
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return -1;
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os_memcpy(tmp, tmp2, SHA1_MAC_LEN);
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for (j = 0; j < SHA1_MAC_LEN; j++)
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digest[j] ^= tmp2[j];
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}
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return 0;
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}
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/**
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* pbkdf2_sha1 - SHA1-based key derivation function (PBKDF2) for IEEE 802.11i
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* @passphrase: ASCII passphrase
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* @ssid: SSID
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* @ssid_len: SSID length in bytes
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* @iterations: Number of iterations to run
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* @buf: Buffer for the generated key
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* @buflen: Length of the buffer in bytes
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* Returns: 0 on success, -1 of failure
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*
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* This function is used to derive PSK for WPA-PSK. For this protocol,
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* iterations is set to 4096 and buflen to 32. This function is described in
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* IEEE Std 802.11-2004, Clause H.4. The main construction is from PKCS#5 v2.0.
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*/
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int pbkdf2_sha1(const char *passphrase, const u8 *ssid, size_t ssid_len,
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int iterations, u8 *buf, size_t buflen)
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{
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unsigned int count = 0;
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unsigned char *pos = buf;
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size_t left = buflen, plen;
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unsigned char digest[SHA1_MAC_LEN];
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while (left > 0) {
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count++;
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if (pbkdf2_sha1_f(passphrase, ssid, ssid_len, iterations,
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count, digest))
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return -1;
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plen = left > SHA1_MAC_LEN ? SHA1_MAC_LEN : left;
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os_memcpy(pos, digest, plen);
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pos += plen;
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left -= plen;
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}
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return 0;
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}
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