text: /* $OpenBSD: rsa_x931.c,v 1.10 2017/01/29 17:49:23 beck Exp $ */
  /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
   * project 2005.
   */
  /* ====================================================================
   * Copyright (c) 2005 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 <stdio.h>
  #include <string.h>
  
  #include <openssl/bn.h>
  #include <openssl/err.h>
  #include <openssl/objects.h>
  #include <openssl/rsa.h>
  
  int
  RSA_padding_add_X931(unsigned char *to, int tlen, const unsigned char *from,
      int flen)
  {
  	int j;
  	unsigned char *p;
  
  	/*
  	 * Absolute minimum amount of padding is 1 header nibble, 1 padding
  	 * nibble and 2 trailer bytes: but 1 hash if is already in 'from'.
  	 */
  	j = tlen - flen - 2;
  
  	if (j < 0) {
  		RSAerror(RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
  		return -1;
  	}
  
  	p = (unsigned char *)to;
  
  	/* If no padding start and end nibbles are in one byte */
  	if (j == 0)
  		*p++ = 0x6A;
  	else {
  		*p++ = 0x6B;
  		if (j > 1) {
  			memset(p, 0xBB, j - 1);
  			p += j - 1;
  		}
  		*p++ = 0xBA;
  	}
  	memcpy(p, from, flen);
  	p += flen;
  	*p = 0xCC;
  	return 1;
  }
  
  int
  RSA_padding_check_X931(unsigned char *to, int tlen, const unsigned char *from,
      int flen, int num)
  {
  	int i = 0, j;
  	const unsigned char *p = from;
  
  	if (num != flen || (*p != 0x6A && *p != 0x6B)) {
  		RSAerror(RSA_R_INVALID_HEADER);
  		return -1;
  	}
  
  	if (*p++ == 0x6B) {
  		j = flen - 3;
  		for (i = 0; i < j; i++) {
  			unsigned char c = *p++;
  			if (c == 0xBA)
  				break;
  			if (c != 0xBB) {
  				RSAerror(RSA_R_INVALID_PADDING);
  				return -1;
  			}
  		}
  
  		if (i == 0) {
  			RSAerror(RSA_R_INVALID_PADDING);
  			return -1;
  		}
  
  		j -= i;
  	} else
  		j = flen - 2;
  
  	if (j < 0 || p[j] != 0xCC) {
  		RSAerror(RSA_R_INVALID_TRAILER);
  		return -1;
  	}
  
  	memcpy(to, p, j);
  
  	return j;
  }
  
  /* Translate between X931 hash ids and NIDs */
  
  int
  RSA_X931_hash_id(int nid)
  {
  	switch (nid) {
  	case NID_sha1:
  		return 0x33;
  	case NID_sha256:
  		return 0x34;
  	case NID_sha384:
  		return 0x36;
  	case NID_sha512:
  		return 0x35;
  	}
  
  	return -1;
  }
  