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/*
* TLS PRF (SHA1 + MD5)
* Copyright (c) 2003-2005, Jouni Malinen <j@w1.fi>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Alternatively, this software may be distributed under the terms of BSD
* license.
*
* See README and COPYING for more details.
*/
#include "includes.h"
#include "common.h"
#include "sha1.h"
#include "md5.h"
#include "crypto.h"
/**
* tls_prf - Pseudo-Random Function for TLS (TLS-PRF, RFC 2246)
* @secret: Key for PRF
* @secret_len: Length of the key in bytes
* @label: A unique label for each purpose of the PRF
* @seed: Seed value to bind into the key
* @seed_len: Length of the seed
* @out: Buffer for the generated pseudo-random key
* @outlen: Number of bytes of key to generate
* Returns: 0 on success, -1 on failure.
*
* This function is used to derive new, cryptographically separate keys from a
* given key in TLS. This PRF is defined in RFC 2246, Chapter 5.
*/
int tls_prf(const u8 *secret, size_t secret_len, const char *label,
const u8 *seed, size_t seed_len, u8 *out, size_t outlen)
{
size_t L_S1, L_S2, i;
const u8 *S1, *S2;
u8 A_MD5[MD5_MAC_LEN], A_SHA1[SHA1_MAC_LEN];
u8 P_MD5[MD5_MAC_LEN], P_SHA1[SHA1_MAC_LEN];
int MD5_pos, SHA1_pos;
const u8 *MD5_addr[3];
size_t MD5_len[3];
const unsigned char *SHA1_addr[3];
size_t SHA1_len[3];
if (secret_len & 1)
return -1;
MD5_addr[0] = A_MD5;
MD5_len[0] = MD5_MAC_LEN;
MD5_addr[1] = (unsigned char *) label;
MD5_len[1] = os_strlen(label);
MD5_addr[2] = seed;
MD5_len[2] = seed_len;
SHA1_addr[0] = A_SHA1;
SHA1_len[0] = SHA1_MAC_LEN;
SHA1_addr[1] = (unsigned char *) label;
SHA1_len[1] = os_strlen(label);
SHA1_addr[2] = seed;
SHA1_len[2] = seed_len;
/* RFC 2246, Chapter 5
* A(0) = seed, A(i) = HMAC(secret, A(i-1))
* P_hash = HMAC(secret, A(1) + seed) + HMAC(secret, A(2) + seed) + ..
* PRF = P_MD5(S1, label + seed) XOR P_SHA-1(S2, label + seed)
*/
L_S1 = L_S2 = (secret_len + 1) / 2;
S1 = secret;
S2 = secret + L_S1;
if (secret_len & 1) {
/* The last byte of S1 will be shared with S2 */
S2--;
}
hmac_md5_vector_non_fips_allow(S1, L_S1, 2, &MD5_addr[1], &MD5_len[1],
A_MD5);
hmac_sha1_vector(S2, L_S2, 2, &SHA1_addr[1], &SHA1_len[1], A_SHA1);
MD5_pos = MD5_MAC_LEN;
SHA1_pos = SHA1_MAC_LEN;
for (i = 0; i < outlen; i++) {
if (MD5_pos == MD5_MAC_LEN) {
hmac_md5_vector_non_fips_allow(S1, L_S1, 3, MD5_addr,
MD5_len, P_MD5);
MD5_pos = 0;
hmac_md5_non_fips_allow(S1, L_S1, A_MD5, MD5_MAC_LEN,
A_MD5);
}
if (SHA1_pos == SHA1_MAC_LEN) {
hmac_sha1_vector(S2, L_S2, 3, SHA1_addr, SHA1_len,
P_SHA1);
SHA1_pos = 0;
hmac_sha1(S2, L_S2, A_SHA1, SHA1_MAC_LEN, A_SHA1);
}
out[i] = P_MD5[MD5_pos] ^ P_SHA1[SHA1_pos];
MD5_pos++;
SHA1_pos++;
}
return 0;
}
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