/* fips_dsa_sign.c */
/*
 * Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL project
 * 2007.
 */
/* ====================================================================
 * Copyright (c) 2007 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    licensing@OpenSSL.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * (eay@cryptsoft.com).  This product includes software written by Tim
 * Hudson (tjh@cryptsoft.com).
 *
 */

#include <string.h>
#include <openssl/evp.h>
#include <openssl/dsa.h>
#include <openssl/err.h>
#include <openssl/sha.h>
#include <openssl/bn.h>

#ifdef OPENSSL_FIPS

/*
 * FIPS versions of DSA_sign() and DSA_verify(). These include a tiny ASN1
 * encoder/decoder to handle the specific case of a DSA signature.
 */

# if 0
int FIPS_dsa_size(DSA *r)
{
    int ilen;
    ilen = BN_num_bytes(r->q);
    if (ilen > 20)
        return -1;
    /* If MSB set need padding byte */
    ilen++;
    /*
     * Also need 2 bytes INTEGER header for r and s plus 2 bytes SEQUENCE
     * header making 6 in total.
     */
    return ilen * 2 + 6;
}
# endif

/*
 * Tiny ASN1 encoder for DSA_SIG structure. We can assume r, s smaller than
 * 0x80 octets as by the DSA standards they will be less than 2^160
 */

int FIPS_dsa_sig_encode(unsigned char *out, DSA_SIG *sig)
{
    int rlen, slen, rpad, spad, seqlen;
    rlen = BN_num_bytes(sig->r);
    if (rlen > 20)
        return -1;
    if (BN_num_bits(sig->r) & 0x7)
        rpad = 0;
    else
        rpad = 1;
    slen = BN_num_bytes(sig->s);
    if (slen > 20)
        return -1;
    if (BN_num_bits(sig->s) & 0x7)
        spad = 0;
    else
        spad = 1;
    /* Length of SEQUENCE, (1 tag + 1 len octet) * 2 + content octets */
    seqlen = rlen + rpad + slen + spad + 4;
    /* Actual encoded length: include SEQUENCE header */
    if (!out)
        return seqlen + 2;

    /* Output SEQUENCE header */
    *out++ = V_ASN1_SEQUENCE | V_ASN1_CONSTRUCTED;
    *out++ = (unsigned char)seqlen;

    /* Output r */
    *out++ = V_ASN1_INTEGER;
    *out++ = (unsigned char)(rlen + rpad);
    if (rpad)
        *out++ = 0;
    BN_bn2bin(sig->r, out);
    out += rlen;

    /* Output s */
    *out++ = V_ASN1_INTEGER;
    *out++ = (unsigned char)(slen + spad);
    if (spad)
        *out++ = 0;
    BN_bn2bin(sig->s, out);
    return seqlen + 2;
}

/* Companion DSA_SIG decoder */

int FIPS_dsa_sig_decode(DSA_SIG *sig, const unsigned char *in, int inlen)
{
    int seqlen, rlen, slen;
    const unsigned char *rbin;
    /* Sanity check */

    /* Need SEQUENCE tag */
    if (*in++ != (V_ASN1_SEQUENCE | V_ASN1_CONSTRUCTED))
        return 0;
    /* Get length octet */
    seqlen = *in++;
    /* Check sensible length value */
    if (seqlen < 4 || seqlen > 0x7F)
        return 0;
    /* Check INTEGER tag */
    if (*in++ != V_ASN1_INTEGER)
        return 0;
    rlen = *in++;
    seqlen -= 2 + rlen;
    /* Check sensible seqlen value */
    if (seqlen < 2)
        return 0;
    rbin = in;
    in += rlen;
    /* Check INTEGER tag */
    if (*in++ != V_ASN1_INTEGER)
        return 0;
    slen = *in++;
    /*
     * Remaining bytes of SEQUENCE should exactly match encoding of s
     */
    if (seqlen != (slen + 2))
        return 0;
    if (!sig->r && !(sig->r = BN_new()))
        return 0;
    if (!sig->s && !(sig->s = BN_new()))
        return 0;
    if (!BN_bin2bn(rbin, rlen, sig->r))
        return 0;
    if (!BN_bin2bn(in, slen, sig->s))
        return 0;
    return 1;
}

static int fips_dsa_sign(int type, const unsigned char *x, int y,
                         unsigned char *sig, unsigned int *siglen,
                         EVP_MD_SVCTX * sv)
{
    DSA *dsa = sv->key;
    unsigned char dig[EVP_MAX_MD_SIZE];
    unsigned int dlen;
    DSA_SIG *s;
    EVP_DigestFinal_ex(sv->mctx, dig, &dlen);
    s = dsa->meth->dsa_do_sign(dig, dlen, dsa);
    OPENSSL_cleanse(dig, dlen);
    if (s == NULL) {
        *siglen = 0;
        return 0;
    }
    *siglen = FIPS_dsa_sig_encode(sig, s);
    DSA_SIG_free(s);
    if (*siglen < 0)
        return 0;
    return 1;
}

static int fips_dsa_verify(int type, const unsigned char *x, int y,
                           const unsigned char *sigbuf, unsigned int siglen,
                           EVP_MD_SVCTX * sv)
{
    DSA *dsa = sv->key;
    DSA_SIG *s;
    int ret = -1;
    unsigned char dig[EVP_MAX_MD_SIZE];
    unsigned int dlen;

    s = DSA_SIG_new();
    if (s == NULL)
        return ret;
    if (!FIPS_dsa_sig_decode(s, sigbuf, siglen))
        goto err;
    EVP_DigestFinal_ex(sv->mctx, dig, &dlen);
    ret = dsa->meth->dsa_do_verify(dig, dlen, s, dsa);
    OPENSSL_cleanse(dig, dlen);
 err:
    DSA_SIG_free(s);
    return ret;
}

static int init(EVP_MD_CTX *ctx)
{
    return SHA1_Init(ctx->md_data);
}

static int update(EVP_MD_CTX *ctx, const void *data, size_t count)
{
    return SHA1_Update(ctx->md_data, data, count);
}

static int final(EVP_MD_CTX *ctx, unsigned char *md)
{
    return SHA1_Final(md, ctx->md_data);
}

static const EVP_MD dss1_md = {
    NID_dsa,
    NID_dsaWithSHA1,
    SHA_DIGEST_LENGTH,
    EVP_MD_FLAG_FIPS | EVP_MD_FLAG_SVCTX,
    init,
    update,
    final,
    NULL,
    NULL,
    (evp_sign_method *) fips_dsa_sign,
    (evp_verify_method *) fips_dsa_verify,
    {EVP_PKEY_DSA, EVP_PKEY_DSA2, EVP_PKEY_DSA3, EVP_PKEY_DSA4, 0},
    SHA_CBLOCK,
    sizeof(EVP_MD *) + sizeof(SHA_CTX),
};

const EVP_MD *EVP_dss1(void)
{
    return (&dss1_md);
}
#endif