src/lib/hmac.c

	hmac.c revision d8361cc8576d9ede93a037f9b96f2a3f9b7e9054
/*
 * HMAC (RFC-2104) implementation.
 *
 * Copyright (c) 2004 Andrey Panin <pazke@donpac.ru>
 * Copyright (c) 2011-2012 Florian Zeitz <florob@babelmonkeys.de>
 *
 * This software is released under the MIT license.
 */

#include "lib.h"
#include "hmac.h"
#include "safe-memset.h"

void hmac_init(struct hmac_context *_ctx, const unsigned char *key,
        size_t key_len, const struct hash_method *meth)
{
    struct hmac_context_priv *ctx = &_ctx->u.priv;
    int i;
    unsigned char k_ipad[64];
    unsigned char k_opad[64];
    unsigned char hashedkey[meth->digest_size];

    i_assert(meth->context_size <= HMAC_MAX_CONTEXT_SIZE);

    ctx->hash = meth;

    if (key_len > 64) {
        meth->init(ctx->ctx);
        meth->loop(ctx->ctx, key, key_len);
        meth->result(ctx->ctx, hashedkey);
        key = hashedkey;
        key_len = meth->digest_size;
    }

    memcpy(k_ipad, key, key_len);
    memset(k_ipad + key_len, 0, 64 - key_len);
    memcpy(k_opad, k_ipad, 64);

    for (i = 0; i < 64; i++) {
        k_ipad[i] ^= 0x36;
        k_opad[i] ^= 0x5c;
    }

    meth->init(ctx->ctx);
    meth->loop(ctx->ctx, k_ipad, 64);
    meth->init(ctx->ctxo);
    meth->loop(ctx->ctxo, k_opad, 64);

    safe_memset(k_ipad, 0, 64);
    safe_memset(k_opad, 0, 64);
}

void hmac_final(struct hmac_context *_ctx, unsigned char *digest)
{
    struct hmac_context_priv *ctx = &_ctx->u.priv;

    ctx->hash->result(ctx->ctx, digest);

    ctx->hash->loop(ctx->ctxo, digest, ctx->hash->digest_size);
    ctx->hash->result(ctx->ctxo, digest);
}