bufbn.c

   1 /* $OpenBSD: bufbn.c,v 1.3 2006/08/03 03:34:41 deraadt 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 an 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 for 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         BN_bin2bn(bin, bytes, value);
 122         if (buffer_consume_ret(buffer, bytes) == -1) {
 123                 error("buffer_get_bignum_ret: buffer_consume failed");
 124                 return (-1);
 125         }
 126         return (0);
 127 }
 128
 129 void
 130 buffer_get_bignum(Buffer *buffer, BIGNUM *value)
 131 {
 132         if (buffer_get_bignum_ret(buffer, value) == -1)
 133                 fatal("buffer_get_bignum: buffer error");
 134 }
 135
 136 /*
 137  * Stores an BIGNUM in the buffer in SSH2 format.
 138  */
 139 int
 140 buffer_put_bignum2_ret(Buffer *buffer, const BIGNUM *value)
 141 {
 142         u_int bytes;
 143         u_char *buf;
 144         int oi;
 145         u_int hasnohigh = 0;
 146
 147         if (BN_is_zero(value)) {
 148                 buffer_put_int(buffer, 0);
 149                 return 0;
 150         }
 151         if (value->neg) {
 152                 error("buffer_put_bignum2_ret: negative numbers not supported");
 153                 return (-1);
 154         }
 155         bytes = BN_num_bytes(value) + 1; /* extra padding byte */
 156         if (bytes < 2) {
 157                 error("buffer_put_bignum2_ret: BN too small");
 158                 return (-1);
 159         }
 160         buf = xmalloc(bytes);
 161         buf[0] = 0x00;
 162         /* Get the value of in binary */
 163         oi = BN_bn2bin(value, buf+1);
 164         if (oi < 0 || (u_int)oi != bytes - 1) {
 165                 error("buffer_put_bignum2_ret: BN_bn2bin() failed: "
 166                     "oi %d != bin_size %d", oi, bytes);
 167                 xfree(buf);
 168                 return (-1);
 169         }
 170         hasnohigh = (buf[1] & 0x80) ? 0 : 1;
 171         buffer_put_string(buffer, buf+hasnohigh, bytes-hasnohigh);
 172         memset(buf, 0, bytes);
 173         xfree(buf);
 174         return (0);
 175 }
 176
 177 void
 178 buffer_put_bignum2(Buffer *buffer, const BIGNUM *value)
 179 {
 180         if (buffer_put_bignum2_ret(buffer, value) == -1)
 181                 fatal("buffer_put_bignum2: buffer error");
 182 }
 183
 184 int
 185 buffer_get_bignum2_ret(Buffer *buffer, BIGNUM *value)
 186 {
 187         u_int len;
 188         u_char *bin;
 189
 190         if ((bin = buffer_get_string_ret(buffer, &len)) == NULL) {
 191                 error("buffer_get_bignum2_ret: invalid bignum");
 192                 return (-1);
 193         }
 194
 195         if (len > 0 && (bin[0] & 0x80)) {
 196                 error("buffer_get_bignum2_ret: negative numbers not supported");
 197                 xfree(bin);
 198                 return (-1);
 199         }
 200         if (len > 8 * 1024) {
 201                 error("buffer_get_bignum2_ret: cannot handle BN of size %d", len);
 202                 xfree(bin);
 203                 return (-1);
 204         }
 205         BN_bin2bn(bin, len, value);
 206         xfree(bin);
 207         return (0);
 208 }
 209
 210 void
 211 buffer_get_bignum2(Buffer *buffer, BIGNUM *value)
 212 {
 213         if (buffer_get_bignum2_ret(buffer, value) == -1)
 214                 fatal("buffer_get_bignum2: buffer error");
 215 }