/* $OpenBSD: rsa_sign.c,v 1.34 2022/01/07 11:13:55 tb Exp $ */

/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)

 * All rights reserved.

 *

 * This package is an SSL implementation written

 * by Eric Young (eay@cryptsoft.com).

 * The implementation was written so as to conform with Netscapes SSL.

 *

 * This library is free for commercial and non-commercial use as long as

 * the following conditions are aheared to.  The following conditions

 * apply to all code found in this distribution, be it the RC4, RSA,

 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation

 * included with this distribution is covered by the same copyright terms

 * except that the holder is Tim Hudson (tjh@cryptsoft.com).

 *

 * Copyright remains Eric Young's, and as such any Copyright notices in

 * the code are not to be removed.

 * If this package is used in a product, Eric Young should be given attribution

 * as the author of the parts of the library used.

 * This can be in the form of a textual message at program startup or

 * in documentation (online or textual) provided with the package.

 *

 * 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 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 acknowledgement:

 *    "This product includes cryptographic software written by

 *     Eric Young (eay@cryptsoft.com)"

 *    The word 'cryptographic' can be left out if the rouines from the library

 *    being used are not cryptographic related :-).

 * 4. If you include any Windows specific code (or a derivative thereof) from

 *    the apps directory (application code) you must include an acknowledgement:

 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"

 *

 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND

 * ANY EXPRESS 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 AUTHOR OR 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.

 *

 * The licence and distribution terms for any publically available version or

 * derivative of this code cannot be changed.  i.e. this code cannot simply be

 * copied and put under another distribution licence

 * [including the GNU Public Licence.]

 */

#include <stdio.h>

#include <string.h>

#include <openssl/bn.h>

#include <openssl/err.h>

#include <openssl/objects.h>

#include <openssl/rsa.h>

#include <openssl/x509.h>

#include "asn1_locl.h"

#include "rsa_locl.h"

#include "x509_lcl.h"

/* Size of an SSL signature: MD5+SHA1 */

#define SSL_SIG_LENGTH  36

static int encode_pkcs1(unsigned char **, int *, int , const unsigned char *,

    unsigned int);

/*

 * encode_pkcs1 encodes a DigestInfo prefix of hash `type' and digest `m', as

 * described in EMSA-PKCS-v1_5-ENCODE, RFC 8017 section 9. step 2. This

 * encodes the DigestInfo (T and tLen) but does not add the padding.

 *

 * On success, it returns one and sets `*out' to a newly allocated buffer

 * containing the result and `*out_len' to its length.  Freeing `*out' is

 * the caller's responsibility. Failure is indicated by zero.

 */

static int

encode_pkcs1(unsigned char **out, int *out_len, int type,

    const unsigned char *m, unsigned int m_len)

{

  X509_SIG sig;

  X509_ALGOR algor;

  ASN1_TYPE parameter;

  ASN1_OCTET_STRING digest;

  uint8_t *der = NULL;

  int len;

  sig.algor = &algor;

  if ((sig.algor->algorithm = OBJ_nid2obj(type)) == NULL) {

    RSAerror(RSA_R_UNKNOWN_ALGORITHM_TYPE);

    return 0;

  }

  if (sig.algor->algorithm->length == 0) {

    RSAerror(

        RSA_R_THE_ASN1_OBJECT_IDENTIFIER_IS_NOT_KNOWN_FOR_THIS_MD);

    return 0;

  }

  parameter.type = V_ASN1_NULL;

  parameter.value.ptr = NULL;

  sig.algor->parameter = &parameter;

  sig.digest = &digest;

  sig.digest->data = (unsigned char *)m; /* TMP UGLY CAST */

  sig.digest->length = m_len;

  if ((len = i2d_X509_SIG(&sig, &der)) < 0)

    return 0;

  *out = der;

  *out_len = len;

  return 1;

}

int

RSA_sign(int type, const unsigned char *m, unsigned int m_len,

    unsigned char *sigret, unsigned int *siglen, RSA *rsa)

{

  const unsigned char *encoded = NULL;

  unsigned char *tmps = NULL;

  int encrypt_len, encoded_len = 0, ret = 0;

  if ((rsa->flags & RSA_FLAG_SIGN_VER) && rsa->meth->rsa_sign != NULL)

    return rsa->meth->rsa_sign(type, m, m_len, sigret, siglen, rsa);

  /* Compute the encoded digest. */

  if (type == NID_md5_sha1) {

    /*

     * NID_md5_sha1 corresponds to the MD5/SHA1 combination in

     * TLS 1.1 and earlier. It has no DigestInfo wrapper but

     * otherwise is RSASSA-PKCS-v1.5.

     */

    if (m_len != SSL_SIG_LENGTH) {

      RSAerror(RSA_R_INVALID_DIGEST_LENGTH);

      return 0;

    }

    encoded_len = SSL_SIG_LENGTH;

    encoded = m;

  } else {

    if (!encode_pkcs1(&tmps, &encoded_len, type, m, m_len))

      goto err;

    encoded = tmps;

  }

  if (encoded_len > RSA_size(rsa) - RSA_PKCS1_PADDING_SIZE) {

    RSAerror(RSA_R_DIGEST_TOO_BIG_FOR_RSA_KEY);

    goto err;

  }

  if ((encrypt_len = RSA_private_encrypt(encoded_len, encoded, sigret,

      rsa, RSA_PKCS1_PADDING)) <= 0)

    goto err;

  *siglen = encrypt_len;

  ret = 1;

 err:

  freezero(tmps, (size_t)encoded_len);

  return (ret);

}

/*

 * int_rsa_verify verifies an RSA signature in `sigbuf' using `rsa'. It may be

 * called in two modes. If `rm' is NULL, it verifies the signature for the

 * digest `m'. Otherwise, it recovers the digest from the signature, writing the

 * digest to `rm' and the length to `*prm_len'. `type' is the NID of the digest

 * algorithm to use. It returns one on successful verification and zero

 * otherwise.

 */

int

int_rsa_verify(int type, const unsigned char *m, unsigned int m_len,

    unsigned char *rm, size_t *prm_len, const unsigned char *sigbuf,

    size_t siglen, RSA *rsa)

{

  unsigned char *decrypt_buf, *encoded = NULL;

  int decrypt_len, encoded_len = 0, ret = 0;

  if (siglen != (size_t)RSA_size(rsa)) {

    RSAerror(RSA_R_WRONG_SIGNATURE_LENGTH);

    return 0;

  }

  /* Recover the encoded digest. */

  if ((decrypt_buf = malloc(siglen)) == NULL) {

    RSAerror(ERR_R_MALLOC_FAILURE);

    goto err;

  }

  if ((decrypt_len = RSA_public_decrypt((int)siglen, sigbuf, decrypt_buf,

      rsa, RSA_PKCS1_PADDING)) <= 0)

    goto err;

  if (type == NID_md5_sha1) {

    /*

     * NID_md5_sha1 corresponds to the MD5/SHA1 combination in

     * TLS 1.1 and earlier. It has no DigestInfo wrapper but

     * otherwise is RSASSA-PKCS1-v1_5.

     */

    if (decrypt_len != SSL_SIG_LENGTH) {

      RSAerror(RSA_R_INVALID_DIGEST_LENGTH);

      goto err;

    }

    if (rm != NULL) {

      memcpy(rm, decrypt_buf, SSL_SIG_LENGTH);

      *prm_len = SSL_SIG_LENGTH;

    } else {

      if (m_len != SSL_SIG_LENGTH) {

        RSAerror(RSA_R_INVALID_MESSAGE_LENGTH);

        goto err;

      }

      if (timingsafe_bcmp(decrypt_buf,

          m, SSL_SIG_LENGTH) != 0) {

        RSAerror(RSA_R_BAD_SIGNATURE);

        goto err;

      }

    }

  } else {

    /*

     * If recovering the digest, extract a digest-sized output from

     * the end of `decrypt_buf' for `encode_pkcs1', then compare the

     * decryption output as in a standard verification.

     */

    if (rm != NULL) {

      const EVP_MD *md;

      if ((md = EVP_get_digestbynid(type)) == NULL) {

        RSAerror(RSA_R_UNKNOWN_ALGORITHM_TYPE);

        goto err;

      }

      if ((m_len = EVP_MD_size(md)) > (size_t)decrypt_len) {

        RSAerror(RSA_R_INVALID_DIGEST_LENGTH);

        goto err;

      }

      m = decrypt_buf + decrypt_len - m_len;

    }

    /* Construct the encoded digest and ensure it matches */

    if (!encode_pkcs1(&encoded, &encoded_len, type, m, m_len))

      goto err;

    if (encoded_len != decrypt_len ||

        timingsafe_bcmp(encoded, decrypt_buf, encoded_len) != 0) {

      RSAerror(RSA_R_BAD_SIGNATURE);

      goto err;

    }

    /* Output the recovered digest. */

    if (rm != NULL) {

      memcpy(rm, m, m_len);

      *prm_len = m_len;

    }

  }

  ret = 1;

 err:

  freezero(encoded, (size_t)encoded_len);

  freezero(decrypt_buf, siglen);

  return ret;

}

int

RSA_verify(int dtype, const unsigned char *m, unsigned int m_len,

    const unsigned char *sigbuf, unsigned int siglen, RSA *rsa)

{

  if ((rsa->flags & RSA_FLAG_SIGN_VER) && rsa->meth->rsa_verify)

    return rsa->meth->rsa_verify(dtype, m, m_len, sigbuf, siglen,

        rsa);

  return int_rsa_verify(dtype, m, m_len, NULL, NULL, sigbuf, siglen, rsa);

}