annotate random.c @ 355:c61bd8f9e32d debug-unrandom

make sure that random number generator is correct endian
author Matt Johnston <matt@ucc.asn.au>
date Wed, 09 Aug 2006 16:45:05 +0000
parents e66eec4dcba7
children
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1 /*
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2 * Dropbear - a SSH2 server
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3 *
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4 * Copyright (c) 2002,2003 Matt Johnston
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5 * All rights reserved.
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6 *
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7 * Permission is hereby granted, free of charge, to any person obtaining a copy
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8 * of this software and associated documentation files (the "Software"), to deal
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9 * in the Software without restriction, including without limitation the rights
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10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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11 * copies of the Software, and to permit persons to whom the Software is
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12 * furnished to do so, subject to the following conditions:
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13 *
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14 * The above copyright notice and this permission notice shall be included in
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15 * all copies or substantial portions of the Software.
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16 *
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17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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20 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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23 * SOFTWARE. */
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24
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25 #include "includes.h"
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26 #include "buffer.h"
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27 #include "dbutil.h"
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28 #include "bignum.h"
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30 static int donerandinit = 0;
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32 /* this is used to generate unique output from the same hashpool */
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33 static uint32_t counter = 0;
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34 /* the max value for the counter, so it won't integer overflow */
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35 #define MAX_COUNTER 1<<30
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37 static unsigned char hashpool[SHA1_HASH_SIZE];
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38
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39 #define INIT_SEED_SIZE 32 /* 256 bits */
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41 /* initialise the prng from /dev/(u)random or prngd */
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42 void seedrandom() {
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43
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44 /* initialise so that things won't warn about
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45 * hashing an undefined buffer */
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46 m_burn(hashpool, sizeof(hashpool));
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48 counter = 0;
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49 donerandinit = 1;
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50 }
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51
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52 /* hash the current random pool with some unique identifiers
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53 * for this process and point-in-time. this is used to separate
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54 * the random pools for fork()ed processes. */
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55 void reseedrandom() {
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56
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57 hash_state hs;
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58
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59 if (!donerandinit) {
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60 dropbear_exit("seedrandom not done");
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61 }
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62
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63 sha1_init(&hs);
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64 sha1_process(&hs, (void*)hashpool, sizeof(hashpool));
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65 sha1_done(&hs, hashpool);
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66 }
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67
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68 /* return len bytes of pseudo-random data */
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69 void genrandom(unsigned char* buf, unsigned int len) {
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71 hash_state hs;
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72 unsigned char hash[SHA1_HASH_SIZE];
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73 unsigned int copylen;
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74 const unsigned int total_len = len;
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75 unsigned char* start_buf = buf;
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76 unsigned char counter_buf[4];
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78 if (!donerandinit) {
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79 dropbear_exit("seedrandom not done");
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80 }
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81
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82 while (len > 0) {
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83 sha1_init(&hs);
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84 sha1_process(&hs, (void*)hashpool, sizeof(hashpool));
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85 STORE32H(counter, counter_buf);
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86 sha1_process(&hs, (void*)counter_buf, sizeof(counter));
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87 sha1_done(&hs, hash);
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89 counter++;
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90 if (counter > MAX_COUNTER) {
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91 seedrandom();
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92 }
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93
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94 copylen = MIN(len, SHA1_HASH_SIZE);
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95 memcpy(buf, hash, copylen);
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96 len -= copylen;
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97 buf += copylen;
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98 }
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99 m_burn(hash, sizeof(hash));
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100 printhex("genrandom", start_buf, total_len);
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101 }
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102
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103 /* Generates a random mp_int.
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104 * max is a *mp_int specifying an upper bound.
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105 * rand must be an initialised *mp_int for the result.
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106 * the result rand satisfies: 0 < rand < max
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107 * */
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108 void gen_random_mpint(mp_int *max, mp_int *rand) {
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109
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110 unsigned char *randbuf = NULL;
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111 unsigned int len = 0;
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112 const char masks[] = {0xff, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f};
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113
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114 const int size_bits = mp_count_bits(max);
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115
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116 len = size_bits / 8;
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117 if ((size_bits % 8) != 0) {
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118 len += 1;
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119 }
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120
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121 randbuf = (unsigned char*)m_malloc(len);
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122 do {
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123 genrandom(randbuf, len);
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124 /* Mask out the unrequired bits - mp_read_unsigned_bin expects
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125 * MSB first.*/
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126 randbuf[0] &= masks[size_bits % 8];
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127
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128 bytes_to_mp(rand, randbuf, len);
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129
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130 /* keep regenerating until we get one satisfying
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131 * 0 < rand < max */
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132 } while ( ( (max != NULL) && (mp_cmp(rand, max) != MP_LT) )
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133 || (mp_cmp_d(rand, 0) != MP_GT) );
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134 m_burn(randbuf, len);
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135 m_free(randbuf);
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136 }