md5.c

Go to the documentation of this file.

#include "includes.h"

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


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];

        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;
        return md5_vector(2, _addr, _len, mac);
}


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);
}