fragattacks/src/crypto/sha1.c

/*
 * SHA1 hash implementation and interface functions
 * 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"


/**
 * hmac_sha1_vector - HMAC-SHA1 over data vector (RFC 2104)
 * @key: Key for HMAC operations
 * @key_len: Length of the key in bytes
 * @num_elem: Number of elements in the data vector
 * @addr: Pointers to the data areas
 * @len: Lengths of the data blocks
 * @mac: Buffer for the hash (20 bytes)
 */
void hmac_sha1_vector(const u8 *key, size_t key_len, size_t num_elem,
		      const u8 *addr[], const size_t *len, u8 *mac)
{
	unsigned char k_pad[64]; /* padding - key XORd with ipad/opad */
	unsigned char tk[20];
	const u8 *_addr[6];
	size_t _len[6], i;

	if (num_elem > 5) {
		/*
		 * Fixed limit on the number of fragments to avoid having to
		 * allocate memory (which could fail).
		 */
		return;
	}

        /* if key is longer than 64 bytes reset it to key = SHA1(key) */
        if (key_len > 64) {
		sha1_vector(1, &key, &key_len, tk);
		key = tk;
		key_len = 20;
        }

	/* the HMAC_SHA1 transform looks like:
	 *
	 * SHA1(K XOR opad, SHA1(K XOR ipad, text))
	 *
	 * where K is an n byte key
	 * ipad is the byte 0x36 repeated 64 times
	 * opad is the byte 0x5c repeated 64 times
	 * and text is the data being protected */

	/* start out by storing key in ipad */
	os_memset(k_pad, 0, sizeof(k_pad));
	os_memcpy(k_pad, key, key_len);
	/* XOR key with ipad values */
	for (i = 0; i < 64; i++)
		k_pad[i] ^= 0x36;

	/* perform inner SHA1 */
	_addr[0] = k_pad;
	_len[0] = 64;
	for (i = 0; i < num_elem; i++) {
		_addr[i + 1] = addr[i];
		_len[i + 1] = len[i];
	}
	sha1_vector(1 + num_elem, _addr, _len, mac);

	os_memset(k_pad, 0, sizeof(k_pad));
	os_memcpy(k_pad, key, key_len);
	/* XOR key with opad values */
	for (i = 0; i < 64; i++)
		k_pad[i] ^= 0x5c;

	/* perform outer SHA1 */
	_addr[0] = k_pad;
	_len[0] = 64;
	_addr[1] = mac;
	_len[1] = SHA1_MAC_LEN;
	sha1_vector(2, _addr, _len, mac);
}


/**
 * hmac_sha1 - HMAC-SHA1 over data buffer (RFC 2104)
 * @key: Key for HMAC operations
 * @key_len: Length of the key in bytes
 * @data: Pointers to the data area
 * @data_len: Length of the data area
 * @mac: Buffer for the hash (20 bytes)
 */
void hmac_sha1(const u8 *key, size_t key_len, const u8 *data, size_t data_len,
	       u8 *mac)
{
	hmac_sha1_vector(key, key_len, 1, &data, &data_len, mac);
}


/**
 * sha1_prf - SHA1-based Pseudo-Random Function (PRF) (IEEE 802.11i, 8.5.1.1)
 * @key: Key for PRF
 * @key_len: Length of the key in bytes
 * @label: A unique label for each purpose of the PRF
 * @data: Extra data to bind into the key
 * @data_len: Length of the data
 * @buf: Buffer for the generated pseudo-random key
 * @buf_len: Number of bytes of key to generate
 *
 * This function is used to derive new, cryptographically separate keys from a
 * given key (e.g., PMK in IEEE 802.11i).
 */
void sha1_prf(const u8 *key, size_t key_len, const char *label,
	      const u8 *data, size_t data_len, u8 *buf, size_t buf_len)
{
	u8 counter = 0;
	size_t pos, plen;
	u8 hash[SHA1_MAC_LEN];
	size_t label_len = os_strlen(label) + 1;
	const unsigned char *addr[3];
	size_t len[3];

	addr[0] = (u8 *) label;
	len[0] = label_len;
	addr[1] = data;
	len[1] = data_len;
	addr[2] = &counter;
	len[2] = 1;

	pos = 0;
	while (pos < buf_len) {
		plen = buf_len - pos;
		if (plen >= SHA1_MAC_LEN) {
			hmac_sha1_vector(key, key_len, 3, addr, len,
					 &buf[pos]);
			pos += SHA1_MAC_LEN;
		} else {
			hmac_sha1_vector(key, key_len, 3, addr, len,
					 hash);
			os_memcpy(&buf[pos], hash, plen);
			break;
		}
		counter++;
	}
}


#ifndef CONFIG_NO_TLS_PRF
/**
 * 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(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(S1, L_S1, 3, MD5_addr, MD5_len, P_MD5);
			MD5_pos = 0;
			hmac_md5(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;
}
#endif /* CONFIG_NO_TLS_PRF */


#ifndef CONFIG_NO_PBKDF2

static void pbkdf2_sha1_f(const char *passphrase, const char *ssid,
			  size_t ssid_len, int iterations, unsigned int count,
			  u8 *digest)
{
	unsigned char tmp[SHA1_MAC_LEN], tmp2[SHA1_MAC_LEN];
	int i, j;
	unsigned char count_buf[4];
	const u8 *addr[2];
	size_t len[2];
	size_t passphrase_len = os_strlen(passphrase);

	addr[0] = (u8 *) ssid;
	len[0] = ssid_len;
	addr[1] = count_buf;
	len[1] = 4;

	/* F(P, S, c, i) = U1 xor U2 xor ... Uc
	 * U1 = PRF(P, S || i)
	 * U2 = PRF(P, U1)
	 * Uc = PRF(P, Uc-1)
	 */

	count_buf[0] = (count >> 24) & 0xff;
	count_buf[1] = (count >> 16) & 0xff;
	count_buf[2] = (count >> 8) & 0xff;
	count_buf[3] = count & 0xff;
	hmac_sha1_vector((u8 *) passphrase, passphrase_len, 2, addr, len, tmp);
	os_memcpy(digest, tmp, SHA1_MAC_LEN);

	for (i = 1; i < iterations; i++) {
		hmac_sha1((u8 *) passphrase, passphrase_len, tmp, SHA1_MAC_LEN,
			  tmp2);
		os_memcpy(tmp, tmp2, SHA1_MAC_LEN);
		for (j = 0; j < SHA1_MAC_LEN; j++)
			digest[j] ^= tmp2[j];
	}
}


/**
 * pbkdf2_sha1 - SHA1-based key derivation function (PBKDF2) for IEEE 802.11i
 * @passphrase: ASCII passphrase
 * @ssid: SSID
 * @ssid_len: SSID length in bytes
 * @iterations: Number of iterations to run
 * @buf: Buffer for the generated key
 * @buflen: Length of the buffer in bytes
 *
 * This function is used to derive PSK for WPA-PSK. For this protocol,
 * iterations is set to 4096 and buflen to 32. This function is described in
 * IEEE Std 802.11-2004, Clause H.4. The main construction is from PKCS#5 v2.0.
 */
void pbkdf2_sha1(const char *passphrase, const char *ssid, size_t ssid_len,
		 int iterations, u8 *buf, size_t buflen)
{
	unsigned int count = 0;
	unsigned char *pos = buf;
	size_t left = buflen, plen;
	unsigned char digest[SHA1_MAC_LEN];

	while (left > 0) {
		count++;
		pbkdf2_sha1_f(passphrase, ssid, ssid_len, iterations, count,
			      digest);
		plen = left > SHA1_MAC_LEN ? SHA1_MAC_LEN : left;
		os_memcpy(pos, digest, plen);
		pos += plen;
		left -= plen;
	}
}

#endif /* CONFIG_NO_PBKDF2 */