hmac.c

/*
 * Copyright (C) 2012 Martin Storsjo
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <string.h>

#include "hmac.h"
#include "md5.h"
#include "sha.h"
#include "mem.h"

#define MAX_HASHLEN 20
#define MAX_BLOCKLEN 64

struct AVHMAC {
    void *hash;
    int blocklen, hashlen;
    void (*final)(void*, uint8_t*);
    void (*update)(void*, const uint8_t*, int len);
    void (*init)(void*);
    uint8_t key[MAX_BLOCKLEN];
    int keylen;
};

static void sha1_init(void *ctx)
{
    av_sha_init(ctx, 160);
}

AVHMAC *av_hmac_alloc(enum AVHMACType type)
{
    AVHMAC *c = av_mallocz(sizeof(*c));
    if (!c)
        return NULL;
    switch (type) {
    case AV_HMAC_MD5:
        c->blocklen = 64;
        c->hashlen  = 16;
        c->init     = av_md5_init;
        c->update   = av_md5_update;
        c->final    = av_md5_final;
        c->hash     = av_md5_alloc();
        break;
    case AV_HMAC_SHA1:
        c->blocklen = 64;
        c->hashlen  = 20;
        c->init     = sha1_init;
        c->update   = av_sha_update;
        c->final    = av_sha_final;
        c->hash     = av_sha_alloc();
        break;
    default:
        av_free(c);
        return NULL;
    }
    if (!c->hash) {
        av_free(c);
        return NULL;
    }
    return c;
}

void av_hmac_free(AVHMAC *c)
{
    if (!c)
        return;
    av_free(c->hash);
    av_free(c);
}

void av_hmac_init(AVHMAC *c, const uint8_t *key, unsigned int keylen)
{
    int i;
    uint8_t block[MAX_BLOCKLEN];
    if (keylen > c->blocklen) {
        c->init(c->hash);
        c->update(c->hash, key, keylen);
        c->final(c->hash, c->key);
        c->keylen = c->hashlen;
    } else {
        memcpy(c->key, key, keylen);
        c->keylen = keylen;
    }
    c->init(c->hash);
    for (i = 0; i < c->keylen; i++)
        block[i] = c->key[i] ^ 0x36;
    for (i = c->keylen; i < c->blocklen; i++)
        block[i] = 0x36;
    c->update(c->hash, block, c->blocklen);
}

void av_hmac_update(AVHMAC *c, const uint8_t *data, unsigned int len)
{
    c->update(c->hash, data, len);
}

int av_hmac_final(AVHMAC *c, uint8_t *out, unsigned int outlen)
{
    uint8_t block[MAX_BLOCKLEN];
    int i;
    if (outlen < c->hashlen)
        return AVERROR(EINVAL);
    c->final(c->hash, out);
    c->init(c->hash);
    for (i = 0; i < c->keylen; i++)
        block[i] = c->key[i] ^ 0x5C;
    for (i = c->keylen; i < c->blocklen; i++)
        block[i] = 0x5C;
    c->update(c->hash, block, c->blocklen);
    c->update(c->hash, out, c->hashlen);
    c->final(c->hash, out);
    return c->hashlen;
}

int av_hmac_calc(AVHMAC *c, const uint8_t *data, unsigned int len,
                 const uint8_t *key, unsigned int keylen,
                 uint8_t *out, unsigned int outlen)
{
    av_hmac_init(c, key, keylen);
    av_hmac_update(c, data, len);
    return av_hmac_final(c, out, outlen);
}

#ifdef TEST
#include <stdio.h>

static void test(AVHMAC *hmac, const uint8_t *key, int keylen,
                 const uint8_t *data, int datalen)
{
    uint8_t buf[MAX_HASHLEN];
    int out, i;
    // Some of the test vectors are strings, where sizeof() includes the
    // trailing null byte - remove that.
    if (!key[keylen - 1])
        keylen--;
    if (!data[datalen - 1])
        datalen--;
    out = av_hmac_calc(hmac, data, datalen, key, keylen, buf, sizeof(buf));
    for (i = 0; i < out; i++)
        printf("%02x", buf[i]);
    printf("\n");
}

int main(void)
{
    uint8_t key1[16], key3[16], data3[50], key4[63], key5[64], key6[65];
    const uint8_t key2[]  = "Jefe";
    const uint8_t data1[] = "Hi There";
    const uint8_t data2[] = "what do ya want for nothing?";
    AVHMAC *hmac = av_hmac_alloc(AV_HMAC_MD5);
    if (!hmac)
        return 1;
    memset(key1, 0x0b, sizeof(key1));
    memset(key3, 0xaa, sizeof(key3));
    memset(key4, 0x44, sizeof(key4));
    memset(key5, 0x55, sizeof(key5));
    memset(key6, 0x66, sizeof(key6));
    memset(data3, 0xdd, sizeof(data3));
    // RFC 2104 test vectors
    test(hmac, key1, sizeof(key1), data1, sizeof(data1));
    test(hmac, key2, sizeof(key2), data2, sizeof(data2));
    test(hmac, key3, sizeof(key3), data3, sizeof(data3));
    // Additional tests, to test cases where the key is too long
    test(hmac, key4, sizeof(key4), data1, sizeof(data1));
    test(hmac, key5, sizeof(key5), data2, sizeof(data2));
    test(hmac, key6, sizeof(key6), data3, sizeof(data3));
    av_hmac_free(hmac);
    return 0;
}
#endif /* TEST */