text: /* $OpenBSD: rsa_ssl.c,v 1.12 2014/07/10 13:58:23 jsing 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/rand.h>
  #include <openssl/rsa.h>
  
  int
  RSA_padding_add_SSLv23(unsigned char *to, int tlen, const unsigned char *from,
      int flen)
  {
  	int i, j;
  	unsigned char *p;
  
  	if (flen > tlen - 11) {
  		RSAerr(RSA_F_RSA_PADDING_ADD_SSLV23,
  		    RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
  		return 0;
  	}
  
  	p = (unsigned char *)to;
  
  	*(p++) = 0;
  	*(p++) = 2; /* Public Key BT (Block Type) */
  
  	/* pad out with non-zero random data */
  	j = tlen - 3 - 8 - flen;
  
  	if (RAND_bytes(p, j) <= 0)
  		return 0;
  	for (i = 0; i < j; i++) {
  		while (*p == '\0') {
  			if (RAND_bytes(p, 1) <= 0)
  				return 0;
  		}
  		p++;
  	}
  
  	memset(p, 3, 8);
  	p += 8;
  	*(p++) = '\0';
  
  	memcpy(p, from, flen);
  	return 1;
  }
  
  int
  RSA_padding_check_SSLv23(unsigned char *to, int tlen, const unsigned char *from,
      int flen, int num)
  {
  	int i, j, k;
  	const unsigned char *p;
  
  	p = from;
  	if (flen < 10) {
  		RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23, RSA_R_DATA_TOO_SMALL);
  		return -1;
  	}
  	if (num != flen + 1 || *(p++) != 02) {
  		RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23,
  		    RSA_R_BLOCK_TYPE_IS_NOT_02);
  		return -1;
  	}
  
  	/* scan over padding data */
  	j = flen - 1; /* one for type */
  	for (i = 0; i < j; i++)
  		if (*(p++) == 0)
  			break;
  
  	if (i == j || i < 8) {
  		RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23,
  		    RSA_R_NULL_BEFORE_BLOCK_MISSING);
  		return -1;
  	}
  	for (k = -9; k < -1; k++) {
  		if (p[k] !=  0x03)
  			break;
  	}
  	if (k == -1) {
  		RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23,
  		    RSA_R_SSLV3_ROLLBACK_ATTACK);
  		return -1;
  	}
  
  	i++; /* Skip over the '\0' */
  	j -= i;
  	if (j > tlen) {
  		RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23, RSA_R_DATA_TOO_LARGE);
  		return -1;
  	}
  	memcpy(to, p, j);
  
  	return j;
  }
  