bufbn.c

   1 /* $OpenBSD: bufbn.c,v 1.6 2007/06/02 09:04:58 djm 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 <sys/types.h>
  43
  44 #include <openssl/bn.h>
  45
  46 #include <string.h>
  47 #include <stdarg.h>
  48
  49 #include "xmalloc.h"
  50 #include "buffer.h"
  51 #include "log.h"
  52 #include "misc.h"
  53
  54 /*
  55  * Stores an BIGNUM in the buffer with a 2-byte msb first bit count, followed
  56  * by (bits+7)/8 bytes of binary data, msb first.
  57  */
  58 int
  59 buffer_put_bignum_ret(Buffer *buffer, const BIGNUM *value)
  60 {
  61         int bits = BN_num_bits(value);
  62         int bin_size = (bits + 7) / 8;
  63         u_char *buf = xmalloc(bin_size);
  64         int oi;
  65         char msg[2];
  66
  67         /* Get the value of in binary */
  68         oi = BN_bn2bin(value, buf);
  69         if (oi != bin_size) {
  70                 error("buffer_put_bignum_ret: BN_bn2bin() failed: oi %d != bin_size %d",
  71                     oi, bin_size);
  72                 xfree(buf);
  73                 return (-1);
  74         }
  75
  76         /* Store the number of bits in the buffer in two bytes, msb first. */
  77         put_u16(msg, bits);
  78         buffer_append(buffer, msg, 2);
  79         /* Store the binary data. */
  80         buffer_append(buffer, buf, oi);
  81
  82         memset(buf, 0, bin_size);
  83         xfree(buf);
  84
  85         return (0);
  86 }
  87
  88 void
  89 buffer_put_bignum(Buffer *buffer, const BIGNUM *value)
  90 {
  91         if (buffer_put_bignum_ret(buffer, value) == -1)
  92                 fatal("buffer_put_bignum: buffer error");
  93 }
  94
  95 /*
  96  * Retrieves a BIGNUM from the buffer.
  97  */
  98 int
  99 buffer_get_bignum_ret(Buffer *buffer, BIGNUM *value)
 100 {
 101         u_int bits, bytes;
 102         u_char buf[2], *bin;
 103
 104         /* Get the number of bits. */
 105         if (buffer_get_ret(buffer, (char *) buf, 2) == -1) {
 106                 error("buffer_get_bignum_ret: invalid length");
 107                 return (-1);
 108         }
 109         bits = get_u16(buf);
 110         /* Compute the number of binary bytes that follow. */
 111         bytes = (bits + 7) / 8;
 112         if (bytes > 8 * 1024) {
 113                 error("buffer_get_bignum_ret: cannot handle BN of size %d", bytes);
 114                 return (-1);
 115         }
 116         if (buffer_len(buffer) < bytes) {
 117                 error("buffer_get_bignum_ret: input buffer too small");
 118                 return (-1);
 119         }
 120         bin = buffer_ptr(buffer);
 121         if (BN_bin2bn(bin, bytes, value) == NULL) {
 122                 error("buffer_get_bignum_ret: BN_bin2bn failed");
 123                 return (-1);
 124         }
 125         if (buffer_consume_ret(buffer, bytes) == -1) {
 126                 error("buffer_get_bignum_ret: buffer_consume failed");
 127                 return (-1);
 128         }
 129         return (0);
 130 }
 131
 132 void
 133 buffer_get_bignum(Buffer *buffer, BIGNUM *value)
 134 {
 135         if (buffer_get_bignum_ret(buffer, value) == -1)
 136                 fatal("buffer_get_bignum: buffer error");
 137 }
 138
 139 /*
 140  * Stores a BIGNUM in the buffer in SSH2 format.
 141  */
 142 int
 143 buffer_put_bignum2_ret(Buffer *buffer, const BIGNUM *value)
 144 {
 145         u_int bytes;
 146         u_char *buf;
 147         int oi;
 148         u_int hasnohigh = 0;
 149
 150         if (BN_is_zero(value)) {
 151                 buffer_put_int(buffer, 0);
 152                 return 0;
 153         }
 154         if (value->neg) {
 155                 error("buffer_put_bignum2_ret: negative numbers not supported");
 156                 return (-1);
 157         }
 158         bytes = BN_num_bytes(value) + 1; /* extra padding byte */
 159         if (bytes < 2) {
 160                 error("buffer_put_bignum2_ret: BN too small");
 161                 return (-1);
 162         }
 163         buf = xmalloc(bytes);
 164         buf[0] = 0x00;
 165         /* Get the value of in binary */
 166         oi = BN_bn2bin(value, buf+1);
 167         if (oi < 0 || (u_int)oi != bytes - 1) {
 168                 error("buffer_put_bignum2_ret: BN_bn2bin() failed: "
 169                     "oi %d != bin_size %d", oi, bytes);
 170                 xfree(buf);
 171                 return (-1);
 172         }
 173         hasnohigh = (buf[1] & 0x80) ? 0 : 1;
 174         buffer_put_string(buffer, buf+hasnohigh, bytes-hasnohigh);
 175         memset(buf, 0, bytes);
 176         xfree(buf);
 177         return (0);
 178 }
 179
 180 void
 181 buffer_put_bignum2(Buffer *buffer, const BIGNUM *value)
 182 {
 183         if (buffer_put_bignum2_ret(buffer, value) == -1)
 184                 fatal("buffer_put_bignum2: buffer error");
 185 }
 186
 187 int
 188 buffer_get_bignum2_ret(Buffer *buffer, BIGNUM *value)
 189 {
 190         u_int len;
 191         u_char *bin;
 192
 193         if ((bin = buffer_get_string_ret(buffer, &len)) == NULL) {
 194                 error("buffer_get_bignum2_ret: invalid bignum");
 195                 return (-1);
 196         }
 197
 198         if (len > 0 && (bin[0] & 0x80)) {
 199                 error("buffer_get_bignum2_ret: negative numbers not supported");
 200                 xfree(bin);
 201                 return (-1);
 202         }
 203         if (len > 8 * 1024) {
 204                 error("buffer_get_bignum2_ret: cannot handle BN of size %d",
 205                     len);
 206                 xfree(bin);
 207                 return (-1);
 208         }
 209         if (BN_bin2bn(bin, len, value) == NULL) {
 210                 error("buffer_get_bignum2_ret: BN_bin2bn failed");
 211                 xfree(bin);
 212                 return (-1);
 213         }
 214         xfree(bin);
 215         return (0);
 216 }
 217
 218 void
 219 buffer_get_bignum2(Buffer *buffer, BIGNUM *value)
 220 {
 221         if (buffer_get_bignum2_ret(buffer, value) == -1)
 222                 fatal("buffer_get_bignum2: buffer error");
 223 }