bufbn.c

   1 /* $OpenBSD: bufbn.c,v 1.2 2006/07/22 20:48:22 stevesk 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
  44 #include <string.h>
  45
  46 #include "bufaux.h"
  47 #include "xmalloc.h"
  48 #include "log.h"
  49 #include "misc.h"
  50
  51 /*
  52  * Stores an BIGNUM in the buffer with a 2-byte msb first bit count, followed
  53  * by (bits+7)/8 bytes of binary data, msb first.
  54  */
  55 int
  56 buffer_put_bignum_ret(Buffer *buffer, const BIGNUM *value)
  57 {
  58         int bits = BN_num_bits(value);
  59         int bin_size = (bits + 7) / 8;
  60         u_char *buf = xmalloc(bin_size);
  61         int oi;
  62         char msg[2];
  63
  64         /* Get the value of in binary */
  65         oi = BN_bn2bin(value, buf);
  66         if (oi != bin_size) {
  67                 error("buffer_put_bignum_ret: BN_bn2bin() failed: oi %d != bin_size %d",
  68                     oi, bin_size);
  69                 xfree(buf);
  70                 return (-1);
  71         }
  72
  73         /* Store the number of bits in the buffer in two bytes, msb first. */
  74         put_u16(msg, bits);
  75         buffer_append(buffer, msg, 2);
  76         /* Store the binary data. */
  77         buffer_append(buffer, buf, oi);
  78
  79         memset(buf, 0, bin_size);
  80         xfree(buf);
  81
  82         return (0);
  83 }
  84
  85 void
  86 buffer_put_bignum(Buffer *buffer, const BIGNUM *value)
  87 {
  88         if (buffer_put_bignum_ret(buffer, value) == -1)
  89                 fatal("buffer_put_bignum: buffer error");
  90 }
  91
  92 /*
  93  * Retrieves an BIGNUM from the buffer.
  94  */
  95 int
  96 buffer_get_bignum_ret(Buffer *buffer, BIGNUM *value)
  97 {
  98         u_int bits, bytes;
  99         u_char buf[2], *bin;
 100
 101         /* Get the number for bits. */
 102         if (buffer_get_ret(buffer, (char *) buf, 2) == -1) {
 103                 error("buffer_get_bignum_ret: invalid length");
 104                 return (-1);
 105         }
 106         bits = get_u16(buf);
 107         /* Compute the number of binary bytes that follow. */
 108         bytes = (bits + 7) / 8;
 109         if (bytes > 8 * 1024) {
 110                 error("buffer_get_bignum_ret: cannot handle BN of size %d", bytes);
 111                 return (-1);
 112         }
 113         if (buffer_len(buffer) < bytes) {
 114                 error("buffer_get_bignum_ret: input buffer too small");
 115                 return (-1);
 116         }
 117         bin = buffer_ptr(buffer);
 118         BN_bin2bn(bin, bytes, value);
 119         if (buffer_consume_ret(buffer, bytes) == -1) {
 120                 error("buffer_get_bignum_ret: buffer_consume failed");
 121                 return (-1);
 122         }
 123         return (0);
 124 }
 125
 126 void
 127 buffer_get_bignum(Buffer *buffer, BIGNUM *value)
 128 {
 129         if (buffer_get_bignum_ret(buffer, value) == -1)
 130                 fatal("buffer_get_bignum: buffer error");
 131 }
 132
 133 /*
 134  * Stores an BIGNUM in the buffer in SSH2 format.
 135  */
 136 int
 137 buffer_put_bignum2_ret(Buffer *buffer, const BIGNUM *value)
 138 {
 139         u_int bytes;
 140         u_char *buf;
 141         int oi;
 142         u_int hasnohigh = 0;
 143
 144         if (BN_is_zero(value)) {
 145                 buffer_put_int(buffer, 0);
 146                 return 0;
 147         }
 148         if (value->neg) {
 149                 error("buffer_put_bignum2_ret: negative numbers not supported");
 150                 return (-1);
 151         }
 152         bytes = BN_num_bytes(value) + 1; /* extra padding byte */
 153         if (bytes < 2) {
 154                 error("buffer_put_bignum2_ret: BN too small");
 155                 return (-1);
 156         }
 157         buf = xmalloc(bytes);
 158         buf[0] = 0x00;
 159         /* Get the value of in binary */
 160         oi = BN_bn2bin(value, buf+1);
 161         if (oi < 0 || (u_int)oi != bytes - 1) {
 162                 error("buffer_put_bignum2_ret: BN_bn2bin() failed: "
 163                     "oi %d != bin_size %d", oi, bytes);
 164                 xfree(buf);
 165                 return (-1);
 166         }
 167         hasnohigh = (buf[1] & 0x80) ? 0 : 1;
 168         buffer_put_string(buffer, buf+hasnohigh, bytes-hasnohigh);
 169         memset(buf, 0, bytes);
 170         xfree(buf);
 171         return (0);
 172 }
 173
 174 void
 175 buffer_put_bignum2(Buffer *buffer, const BIGNUM *value)
 176 {
 177         if (buffer_put_bignum2_ret(buffer, value) == -1)
 178                 fatal("buffer_put_bignum2: buffer error");
 179 }
 180
 181 int
 182 buffer_get_bignum2_ret(Buffer *buffer, BIGNUM *value)
 183 {
 184         u_int len;
 185         u_char *bin;
 186
 187         if ((bin = buffer_get_string_ret(buffer, &len)) == NULL) {
 188                 error("buffer_get_bignum2_ret: invalid bignum");
 189                 return (-1);
 190         }
 191
 192         if (len > 0 && (bin[0] & 0x80)) {
 193                 error("buffer_get_bignum2_ret: negative numbers not supported");
 194                 xfree(bin);
 195                 return (-1);
 196         }
 197         if (len > 8 * 1024) {
 198                 error("buffer_get_bignum2_ret: cannot handle BN of size %d", len);
 199                 xfree(bin);
 200                 return (-1);
 201         }
 202         BN_bin2bn(bin, len, value);
 203         xfree(bin);
 204         return (0);
 205 }
 206
 207 void
 208 buffer_get_bignum2(Buffer *buffer, BIGNUM *value)
 209 {
 210         if (buffer_get_bignum2_ret(buffer, value) == -1)
 211                 fatal("buffer_get_bignum2: buffer error");
 212 }