src/crypto/md5.c

/*
 * MD5 hash implementation and interface functions
 * Copyright (c) 2003-2005, Jouni Malinen <j@w1.fi>
 *
 * This software may be distributed under the terms of the BSD license.
 * See README for more details.
 */

#include "includes.h"

#include "common.h"
#include "md5.h"
#include "crypto.h"


/**
 * hmac_md5_vector - HMAC-MD5 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 (16 bytes)
 * Returns: 0 on success, -1 on failure
 */
int hmac_md5_vector(const u8 *key, size_t key_len, size_t num_elem,
		    const u8 *addr[], const size_t *len, u8 *mac)
{
	u8 k_pad[64]; /* padding - key XORd with ipad/opad */
	u8 tk[16];
	const u8 *_addr[6];
	size_t i, _len[6];
	int res;

	if (num_elem > 5) {
		/*
		 * Fixed limit on the number of fragments to avoid having to
		 * allocate memory (which could fail).
		 */
		return -1;
	}

        /* if key is longer than 64 bytes reset it to key = MD5(key) */
        if (key_len > 64) {
		if (md5_vector(1, &key, &key_len, tk))
			return -1;
		key = tk;
		key_len = 16;
        }

	/* the HMAC_MD5 transform looks like:
	 *
	 * MD5(K XOR opad, MD5(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 MD5 */
	_addr[0] = k_pad;
	_len[0] = 64;
	for (i = 0; i < num_elem; i++) {
		_addr[i + 1] = addr[i];
		_len[i + 1] = len[i];
	}
	if (md5_vector(1 + num_elem, _addr, _len, mac))
		return -1;

	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 MD5 */
	_addr[0] = k_pad;
	_len[0] = 64;
	_addr[1] = mac;
	_len[1] = MD5_MAC_LEN;
	res = md5_vector(2, _addr, _len, mac);
	os_memset(k_pad, 0, sizeof(k_pad));
	os_memset(tk, 0, sizeof(tk));
	return res;
}


/**
 * hmac_md5 - HMAC-MD5 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 (16 bytes)
 * Returns: 0 on success, -1 on failure
 */
int hmac_md5(const u8 *key, size_t key_len, const u8 *data, size_t data_len,
	      u8 *mac)
{
	return hmac_md5_vector(key, key_len, 1, &data, &data_len, mac);
}