bufbn.c

   1 /* $OpenBSD: bufbn.c,v 1.1 2006/04/18 10:44:28 dtucker Exp $*/
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Auxiliary functions for storing and retrieving various data types to/from
   7  * Buffers.
   8  *
   9  * As far as I am concerned, the code I have written for this software
  10  * can be used freely for any purpose.  Any derived versions of this
  11  * software must be clearly marked as such, and if the derived work is
  12  * incompatible with the protocol description in the RFC file, it must be
  13  * called by a name other than "ssh" or "Secure Shell".
  14  *
  15  *
  16  * SSH2 packet format added by Markus Friedl
  17  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  18  *
  19  * Redistribution and use in source and binary forms, with or without
  20  * modification, are permitted provided that the following conditions
  21  * are met:
  22  * 1. Redistributions of source code must retain the above copyright
  23  *    notice, this list of conditions and the following disclaimer.
  24  * 2. Redistributions in binary form must reproduce the above copyright
  25  *    notice, this list of conditions and the following disclaimer in the
  26  *    documentation and/or other materials provided with the distribution.
  27  *
  28  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  29  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  30  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  31  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  32  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  33  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  34  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  35  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  36  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  37  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  38  */
  39
  40 #include "includes.h"
  41
  42 #include <openssl/bn.h>
  43 #include "bufaux.h"
  44 #include "xmalloc.h"
  45 #include "log.h"
  46 #include "misc.h"
  47
  48 /*
  49  * Stores an BIGNUM in the buffer with a 2-byte msb first bit count, followed
  50  * by (bits+7)/8 bytes of binary data, msb first.
  51  */
  52 int
  53 buffer_put_bignum_ret(Buffer *buffer, const BIGNUM *value)
  54 {
  55         int bits = BN_num_bits(value);
  56         int bin_size = (bits + 7) / 8;
  57         u_char *buf = xmalloc(bin_size);
  58         int oi;
  59         char msg[2];
  60
  61         /* Get the value of in binary */
  62         oi = BN_bn2bin(value, buf);
  63         if (oi != bin_size) {
  64                 error("buffer_put_bignum_ret: BN_bn2bin() failed: oi %d != bin_size %d",
  65                     oi, bin_size);
  66                 xfree(buf);
  67                 return (-1);
  68         }
  69
  70         /* Store the number of bits in the buffer in two bytes, msb first. */
  71         put_u16(msg, bits);
  72         buffer_append(buffer, msg, 2);
  73         /* Store the binary data. */
  74         buffer_append(buffer, buf, oi);
  75
  76         memset(buf, 0, bin_size);
  77         xfree(buf);
  78
  79         return (0);
  80 }
  81
  82 void
  83 buffer_put_bignum(Buffer *buffer, const BIGNUM *value)
  84 {
  85         if (buffer_put_bignum_ret(buffer, value) == -1)
  86                 fatal("buffer_put_bignum: buffer error");
  87 }
  88
  89 /*
  90  * Retrieves an BIGNUM from the buffer.
  91  */
  92 int
  93 buffer_get_bignum_ret(Buffer *buffer, BIGNUM *value)
  94 {
  95         u_int bits, bytes;
  96         u_char buf[2], *bin;
  97
  98         /* Get the number for bits. */
  99         if (buffer_get_ret(buffer, (char *) buf, 2) == -1) {
 100                 error("buffer_get_bignum_ret: invalid length");
 101                 return (-1);
 102         }
 103         bits = get_u16(buf);
 104         /* Compute the number of binary bytes that follow. */
 105         bytes = (bits + 7) / 8;
 106         if (bytes > 8 * 1024) {
 107                 error("buffer_get_bignum_ret: cannot handle BN of size %d", bytes);
 108                 return (-1);
 109         }
 110         if (buffer_len(buffer) < bytes) {
 111                 error("buffer_get_bignum_ret: input buffer too small");
 112                 return (-1);
 113         }
 114         bin = buffer_ptr(buffer);
 115         BN_bin2bn(bin, bytes, value);
 116         if (buffer_consume_ret(buffer, bytes) == -1) {
 117                 error("buffer_get_bignum_ret: buffer_consume failed");
 118                 return (-1);
 119         }
 120         return (0);
 121 }
 122
 123 void
 124 buffer_get_bignum(Buffer *buffer, BIGNUM *value)
 125 {
 126         if (buffer_get_bignum_ret(buffer, value) == -1)
 127                 fatal("buffer_get_bignum: buffer error");
 128 }
 129
 130 /*
 131  * Stores an BIGNUM in the buffer in SSH2 format.
 132  */
 133 int
 134 buffer_put_bignum2_ret(Buffer *buffer, const BIGNUM *value)
 135 {
 136         u_int bytes;
 137         u_char *buf;
 138         int oi;
 139         u_int hasnohigh = 0;
 140
 141         if (BN_is_zero(value)) {
 142                 buffer_put_int(buffer, 0);
 143                 return 0;
 144         }
 145         if (value->neg) {
 146                 error("buffer_put_bignum2_ret: negative numbers not supported");
 147                 return (-1);
 148         }
 149         bytes = BN_num_bytes(value) + 1; /* extra padding byte */
 150         if (bytes < 2) {
 151                 error("buffer_put_bignum2_ret: BN too small");
 152                 return (-1);
 153         }
 154         buf = xmalloc(bytes);
 155         buf[0] = 0x00;
 156         /* Get the value of in binary */
 157         oi = BN_bn2bin(value, buf+1);
 158         if (oi < 0 || (u_int)oi != bytes - 1) {
 159                 error("buffer_put_bignum2_ret: BN_bn2bin() failed: "
 160                     "oi %d != bin_size %d", oi, bytes);
 161                 xfree(buf);
 162                 return (-1);
 163         }
 164         hasnohigh = (buf[1] & 0x80) ? 0 : 1;
 165         buffer_put_string(buffer, buf+hasnohigh, bytes-hasnohigh);
 166         memset(buf, 0, bytes);
 167         xfree(buf);
 168         return (0);
 169 }
 170
 171 void
 172 buffer_put_bignum2(Buffer *buffer, const BIGNUM *value)
 173 {
 174         if (buffer_put_bignum2_ret(buffer, value) == -1)
 175                 fatal("buffer_put_bignum2: buffer error");
 176 }
 177
 178 int
 179 buffer_get_bignum2_ret(Buffer *buffer, BIGNUM *value)
 180 {
 181         u_int len;
 182         u_char *bin;
 183
 184         if ((bin = buffer_get_string_ret(buffer, &len)) == NULL) {
 185                 error("buffer_get_bignum2_ret: invalid bignum");
 186                 return (-1);
 187         }
 188
 189         if (len > 0 && (bin[0] & 0x80)) {
 190                 error("buffer_get_bignum2_ret: negative numbers not supported");
 191                 xfree(bin);
 192                 return (-1);
 193         }
 194         if (len > 8 * 1024) {
 195                 error("buffer_get_bignum2_ret: cannot handle BN of size %d", len);
 196                 xfree(bin);
 197                 return (-1);
 198         }
 199         BN_bin2bn(bin, len, value);
 200         xfree(bin);
 201         return (0);
 202 }
 203
 204 void
 205 buffer_get_bignum2(Buffer *buffer, BIGNUM *value)
 206 {
 207         if (buffer_get_bignum2_ret(buffer, value) == -1)
 208                 fatal("buffer_get_bignum2: buffer error");
 209 }