openssl/crypto/hmac/hm_meth.c

/*
 * Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

#include <string.h>
#include <openssl/err.h>
#include <openssl/ossl_typ.h>
#include <openssl/asn1.h>
#include <openssl/hmac.h>
#include "internal/evp_int.h"

/* local HMAC context structure */

/* typedef EVP_MAC_IMPL */
struct evp_mac_impl_st {
    /* tmpmd and tmpengine are set to NULL after a CMAC_Init call */
    const EVP_MD *tmpmd;         /* HMAC digest */
    const ENGINE *tmpengine;     /* HMAC digest engine */
    HMAC_CTX *ctx;               /* HMAC context */
};

static EVP_MAC_IMPL *hmac_new(void)
{
    EVP_MAC_IMPL *hctx;

    if ((hctx = OPENSSL_zalloc(sizeof(*hctx))) == NULL
        || (hctx->ctx = HMAC_CTX_new()) == NULL) {
        OPENSSL_free(hctx);
        return NULL;
    }

    return hctx;
}

static void hmac_free(EVP_MAC_IMPL *hctx)
{
    if (hctx != NULL) {
        HMAC_CTX_free(hctx->ctx);
        OPENSSL_free(hctx);
    }
}

static EVP_MAC_IMPL *hmac_dup(const EVP_MAC_IMPL *hsrc)
{
    EVP_MAC_IMPL *hdst;

    hdst = hmac_new();
    if (hdst == NULL)
        return NULL;

    if (!HMAC_CTX_copy(hdst->ctx, hsrc->ctx)) {
        hmac_free(hdst);
        return NULL;
    }

    hdst->tmpengine = hsrc->tmpengine;
    hdst->tmpmd = hsrc->tmpmd;

    return hdst;
}

static size_t hmac_size(EVP_MAC_IMPL *hctx)
{
    return HMAC_size(hctx->ctx);
}

static int hmac_init(EVP_MAC_IMPL *hctx)
{
    int rv = 1;

    /* HMAC_Init_ex doesn't tolerate all zero params, so we must be careful */
    if (hctx->tmpmd != NULL)
        rv = HMAC_Init_ex(hctx->ctx, NULL, 0, hctx->tmpmd,
                          (ENGINE * )hctx->tmpengine);
    hctx->tmpengine = NULL;
    hctx->tmpmd = NULL;
    return rv;
}

static int hmac_update(EVP_MAC_IMPL *hctx, const unsigned char *data,
                       size_t datalen)
{
    return HMAC_Update(hctx->ctx, data, datalen);
}

static int hmac_final(EVP_MAC_IMPL *hctx, unsigned char *out)
{
    unsigned int hlen;

    return HMAC_Final(hctx->ctx, out, &hlen);
}

static int hmac_ctrl(EVP_MAC_IMPL *hctx, int cmd, va_list args)
{
    switch (cmd) {
    case EVP_MAC_CTRL_SET_FLAGS:
        {
            unsigned long flags = va_arg(args, unsigned long);

            HMAC_CTX_set_flags(hctx->ctx, flags);
        }
        break;
    case EVP_MAC_CTRL_SET_KEY:
        {
            const unsigned char *key = va_arg(args, const unsigned char *);
            size_t keylen = va_arg(args, size_t);
            int rv = HMAC_Init_ex(hctx->ctx, key, keylen, hctx->tmpmd,
                                  (ENGINE *)hctx->tmpengine);

            hctx->tmpengine = NULL;
            hctx->tmpmd = NULL;
            return rv;
        }
        break;
    case EVP_MAC_CTRL_SET_MD:
        hctx->tmpmd = va_arg(args, const EVP_MD *);
        break;
    case EVP_MAC_CTRL_SET_ENGINE:
        hctx->tmpengine = va_arg(args, const ENGINE *);
        break;
    default:
        return -2;

    }
    return 1;
}

static int hmac_ctrl_int(EVP_MAC_IMPL *hctx, int cmd, ...)
{
    int rv;
    va_list args;

    va_start(args, cmd);
    rv = hmac_ctrl(hctx, cmd, args);
    va_end(args);

    return rv;
}

static int hmac_ctrl_str_cb(void *hctx, int cmd, void *buf, size_t buflen)
{
    return hmac_ctrl_int(hctx, cmd, buf, buflen);
}

static int hmac_ctrl_str(EVP_MAC_IMPL *hctx, const char *type,
                         const char *value)
{
    if (!value)
        return 0;
#ifndef FIPS_MODE
    /*
     * We don't have EVP_get_digestbyname() in FIPS_MODE. That function returns
     * an EVP_MD without an associated provider implementation (i.e. it is
     * using "implicit fetch"). We could replace it with an "explicit" fetch
     * using EVP_MD_fetch(), but we'd then be required to free the returned
     * EVP_MD somewhere. Probably the complexity isn't worth it as we are
     * unlikely to need this ctrl in FIPS_MODE anyway.
     */
    if (strcmp(type, "digest") == 0) {
        const EVP_MD *d = EVP_get_digestbyname(value);

        if (d == NULL)
            return 0;
        return hmac_ctrl_int(hctx, EVP_MAC_CTRL_SET_MD, d);
    }
#endif
    if (strcmp(type, "key") == 0)
        return EVP_str2ctrl(hmac_ctrl_str_cb, hctx, EVP_MAC_CTRL_SET_KEY,
                            value);
    if (strcmp(type, "hexkey") == 0)
        return EVP_hex2ctrl(hmac_ctrl_str_cb, hctx, EVP_MAC_CTRL_SET_KEY,
                            value);
    return -2;
}

const EVP_MAC hmac_meth = {
    EVP_MAC_HMAC,
    hmac_new,
    hmac_dup,
    hmac_free,
    hmac_size,
    hmac_init,
    hmac_update,
    hmac_final,
    hmac_ctrl,
    hmac_ctrl_str
};