annotate random.c @ 808:d7784616409a

improve auth failure delays to avoid indicating which users exist
author Matt Johnston <matt@ucc.asn.au>
date Sun, 26 May 2013 18:39:24 +0800
parents 7deb6fda1319
children 7dcb46da72d9 5de524aec047
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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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29 #include "random.h"
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30
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31 /* this is used to generate unique output from the same hashpool */
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32 static uint32_t counter = 0;
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33 /* the max value for the counter, so it won't integer overflow */
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34 #define MAX_COUNTER 1<<30
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35
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36 static unsigned char hashpool[SHA1_HASH_SIZE] = {0};
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37 static int donerandinit = 0;
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38
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39 #define INIT_SEED_SIZE 32 /* 256 bits */
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40
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41 /* The basic setup is we read some data from /dev/(u)random or prngd and hash it
4
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42 * into hashpool. To read data, we hash together current hashpool contents,
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43 * and a counter. We feed more data in by hashing the current pool and new
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44 * data into the pool.
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45 *
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46 * It is important to ensure that counter doesn't wrap around before we
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47 * feed in new entropy.
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48 *
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49 */
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50
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51 /* Pass len=0 to hash an entire file */
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52 static int
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53 process_file(hash_state *hs, const char *filename,
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54 unsigned int len, int prngd)
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55 {
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56 static int already_blocked = 0;
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57 int readfd;
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58 unsigned int readcount;
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59 int ret = DROPBEAR_FAILURE;
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60
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61 #ifdef DROPBEAR_PRNGD_SOCKET
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62 if (prngd)
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63 {
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64 readfd = connect_unix(filename);
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65 }
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66 else
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67 #endif
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68 {
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69 readfd = open(filename, O_RDONLY);
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70 }
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71
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72 if (readfd < 0) {
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73 goto out;
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74 }
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75
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76 readcount = 0;
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77 while (len == 0 || readcount < len)
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78 {
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79 int readlen, wantread;
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80 unsigned char readbuf[2048];
185
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81 if (!already_blocked)
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82 {
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83 int ret;
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84 struct timeval timeout = { .tv_sec = 2, .tv_usec = 0};
185
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85 fd_set read_fds;
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86
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87 FD_ZERO(&read_fds);
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88 FD_SET(readfd, &read_fds);
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89 ret = select(readfd + 1, &read_fds, NULL, NULL, &timeout);
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90 if (ret == 0)
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91 {
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92 dropbear_log(LOG_WARNING, "Warning: Reading the randomness source '%s' seems to have blocked.\nYou may need to find a better entropy source.", filename);
185
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93 already_blocked = 1;
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94 }
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95 }
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96
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97 if (len == 0)
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98 {
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99 wantread = sizeof(readbuf);
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100 }
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101 else
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102 {
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103 wantread = MIN(sizeof(readbuf), len-readcount);
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104 }
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105
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106 #ifdef DROPBEAR_PRNGD_SOCKET
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107 if (prngd)
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108 {
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109 char egdcmd[2];
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110 egdcmd[0] = 0x02; /* blocking read */
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111 egdcmd[1] = (unsigned char)wantread;
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112 if (write(readfd, egdcmd, 2) < 0)
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113 {
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114 dropbear_exit("Can't send command to egd");
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115 }
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116 }
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117 #endif
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118
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119 readlen = read(readfd, readbuf, wantread);
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120 if (readlen <= 0) {
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121 if (readlen < 0 && errno == EINTR) {
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122 continue;
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123 }
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124 if (readlen == 0 && len == 0)
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125 {
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126 /* whole file was read as requested */
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127 break;
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128 }
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129 goto out;
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130 }
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131 sha1_process(hs, readbuf, readlen);
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132 readcount += readlen;
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133 }
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134 ret = DROPBEAR_SUCCESS;
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135 out:
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136 close(readfd);
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137 return ret;
4
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138 }
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139
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140 void addrandom(char * buf, unsigned int len)
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141 {
4
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142 hash_state hs;
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143
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144 /* hash in the new seed data */
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145 sha1_init(&hs);
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146 /* existing state (zeroes on startup) */
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147 sha1_process(&hs, (void*)hashpool, sizeof(hashpool));
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148
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149 /* new */
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150 sha1_process(&hs, buf, len);
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151 sha1_done(&hs, hashpool);
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152 }
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153
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154 static void write_urandom()
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155 {
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156 #ifndef DROPBEAR_PRNGD_SOCKET
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157 /* This is opportunistic, don't worry about failure */
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158 unsigned char buf[INIT_SEED_SIZE];
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159 FILE *f = fopen(DROPBEAR_URANDOM_DEV, "w");
737
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160 if (!f) {
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161 return;
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162 }
687
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163 genrandom(buf, sizeof(buf));
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164 fwrite(buf, sizeof(buf), 1, f);
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165 fclose(f);
167fdc091c05 Improve RNG seeding.
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166 #endif
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167 }
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168
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169 /* Initialise the prng from /dev/urandom or prngd. This function can
167fdc091c05 Improve RNG seeding.
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170 * be called multiple times */
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171 void seedrandom() {
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172
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173 hash_state hs;
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174
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175 pid_t pid;
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176 struct timeval tv;
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177 clock_t clockval;
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178
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179 /* hash in the new seed data */
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180 sha1_init(&hs);
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181 /* existing state */
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182 sha1_process(&hs, (void*)hashpool, sizeof(hashpool));
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183
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184 #ifdef DROPBEAR_PRNGD_SOCKET
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185 if (process_file(&hs, DROPBEAR_PRNGD_SOCKET, INIT_SEED_SIZE, 1)
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186 != DROPBEAR_SUCCESS) {
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187 dropbear_exit("Failure reading random device %s",
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188 DROPBEAR_PRNGD_SOCKET);
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189 }
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190 #else
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191 /* non-blocking random source (probably /dev/urandom) */
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192 if (process_file(&hs, DROPBEAR_URANDOM_DEV, INIT_SEED_SIZE, 0)
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193 != DROPBEAR_SUCCESS) {
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194 dropbear_exit("Failure reading random device %s",
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195 DROPBEAR_URANDOM_DEV);
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196 }
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197 #endif
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198
694
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199 /* A few other sources to fall back on.
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200 * Add more here for other platforms */
687
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201 #ifdef __linux__
688
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202 /* Seems to be a reasonable source of entropy from timers. Possibly hard
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203 * for even local attackers to reproduce */
687
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204 process_file(&hs, "/proc/timer_list", 0, 0);
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205 /* Might help on systems with wireless */
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206 process_file(&hs, "/proc/interrupts", 0, 0);
688
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207
694
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208 process_file(&hs, "/proc/loadavg", 0, 0);
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209 process_file(&hs, "/proc/sys/kernel/random/entropy_avail", 0, 0);
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210
688
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211 /* Mostly network visible but useful in some situations */
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212 process_file(&hs, "/proc/net/netstat", 0, 0);
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213 process_file(&hs, "/proc/net/dev", 0, 0);
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214 process_file(&hs, "/proc/net/tcp", 0, 0);
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215 /* Also includes interface lo */
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216 process_file(&hs, "/proc/net/rt_cache", 0, 0);
702
48e173a0c52b Include /proc/vmstat as another random source
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217 process_file(&hs, "/proc/vmstat", 0, 0);
687
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218 #endif
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219
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220 pid = getpid();
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221 sha1_process(&hs, (void*)&pid, sizeof(pid));
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222
714
84157e435c52 Make sure "struct timeval" is initialised on OS X to avoid valgrind warnings
Matt Johnston <matt@ucc.asn.au>
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diff changeset
223 // gettimeofday() doesn't completely fill out struct timeval on
84157e435c52 Make sure "struct timeval" is initialised on OS X to avoid valgrind warnings
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224 // OS X (10.8.3), avoid valgrind warnings by clearing it first
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225 memset(&tv, 0x0, sizeof(tv));
687
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226 gettimeofday(&tv, NULL);
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227 sha1_process(&hs, (void*)&tv, sizeof(tv));
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228
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229 clockval = clock();
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diff changeset
230 sha1_process(&hs, (void*)&clockval, sizeof(clockval));
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231
167fdc091c05 Improve RNG seeding.
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232 /* When a private key is read by the client or server it will
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233 * be added to the hashpool - see runopts.c */
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234
4
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235 sha1_done(&hs, hashpool);
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236
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diff changeset
237 counter = 0;
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238 donerandinit = 1;
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239
687
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diff changeset
240 /* Feed it all back into /dev/urandom - this might help if Dropbear
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parents: 602
diff changeset
241 * is running from inetd and gets new state each time */
167fdc091c05 Improve RNG seeding.
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diff changeset
242 write_urandom();
272
3be7ae2e8dfa Only read /dev/random once when the program starts
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parents: 198
diff changeset
243 }
3be7ae2e8dfa Only read /dev/random once when the program starts
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diff changeset
244
4
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diff changeset
245 /* return len bytes of pseudo-random data */
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parents:
diff changeset
246 void genrandom(unsigned char* buf, unsigned int len) {
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diff changeset
247
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diff changeset
248 hash_state hs;
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parents:
diff changeset
249 unsigned char hash[SHA1_HASH_SIZE];
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diff changeset
250 unsigned int copylen;
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parents:
diff changeset
251
fe6bca95afa7 Makefile.in contains updated files required
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parents:
diff changeset
252 if (!donerandinit) {
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diff changeset
253 dropbear_exit("seedrandom not done");
fe6bca95afa7 Makefile.in contains updated files required
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parents:
diff changeset
254 }
fe6bca95afa7 Makefile.in contains updated files required
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parents:
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255
fe6bca95afa7 Makefile.in contains updated files required
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
256 while (len > 0) {
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parents:
diff changeset
257 sha1_init(&hs);
fe6bca95afa7 Makefile.in contains updated files required
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parents:
diff changeset
258 sha1_process(&hs, (void*)hashpool, sizeof(hashpool));
fe6bca95afa7 Makefile.in contains updated files required
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parents:
diff changeset
259 sha1_process(&hs, (void*)&counter, sizeof(counter));
fe6bca95afa7 Makefile.in contains updated files required
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parents:
diff changeset
260 sha1_done(&hs, hash);
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parents:
diff changeset
261
fe6bca95afa7 Makefile.in contains updated files required
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parents:
diff changeset
262 counter++;
fe6bca95afa7 Makefile.in contains updated files required
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
263 if (counter > MAX_COUNTER) {
fe6bca95afa7 Makefile.in contains updated files required
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parents:
diff changeset
264 seedrandom();
fe6bca95afa7 Makefile.in contains updated files required
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
265 }
fe6bca95afa7 Makefile.in contains updated files required
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parents:
diff changeset
266
fe6bca95afa7 Makefile.in contains updated files required
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parents:
diff changeset
267 copylen = MIN(len, SHA1_HASH_SIZE);
fe6bca95afa7 Makefile.in contains updated files required
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parents:
diff changeset
268 memcpy(buf, hash, copylen);
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parents:
diff changeset
269 len -= copylen;
fe6bca95afa7 Makefile.in contains updated files required
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parents:
diff changeset
270 buf += copylen;
fe6bca95afa7 Makefile.in contains updated files required
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parents:
diff changeset
271 }
fe6bca95afa7 Makefile.in contains updated files required
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parents:
diff changeset
272 m_burn(hash, sizeof(hash));
fe6bca95afa7 Makefile.in contains updated files required
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parents:
diff changeset
273 }
188
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
274
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
275 /* Generates a random mp_int.
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parents: 159
diff changeset
276 * max is a *mp_int specifying an upper bound.
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parents: 159
diff changeset
277 * rand must be an initialised *mp_int for the result.
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
278 * the result rand satisfies: 0 < rand < max
c9483550701b - refactored random mp_int generation and byte->mp_int code
Matt Johnston <matt@ucc.asn.au>
parents: 159
diff changeset
279 * */
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
280 void gen_random_mpint(mp_int *max, mp_int *rand) {
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
281
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
282 unsigned char *randbuf = NULL;
c9483550701b - refactored random mp_int generation and byte->mp_int code
Matt Johnston <matt@ucc.asn.au>
parents: 159
diff changeset
283 unsigned int len = 0;
433
c216212001fc Fix for -pedantic -ansi compilation, change // to /**/, plus some signedness
Matt Johnston <matt@ucc.asn.au>
parents: 405
diff changeset
284 const unsigned char masks[] = {0xff, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f};
188
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
285
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
286 const int size_bits = mp_count_bits(max);
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
287
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
288 len = size_bits / 8;
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
289 if ((size_bits % 8) != 0) {
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
290 len += 1;
c9483550701b - refactored random mp_int generation and byte->mp_int code
Matt Johnston <matt@ucc.asn.au>
parents: 159
diff changeset
291 }
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
292
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
293 randbuf = (unsigned char*)m_malloc(len);
c9483550701b - refactored random mp_int generation and byte->mp_int code
Matt Johnston <matt@ucc.asn.au>
parents: 159
diff changeset
294 do {
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
295 genrandom(randbuf, len);
c9483550701b - refactored random mp_int generation and byte->mp_int code
Matt Johnston <matt@ucc.asn.au>
parents: 159
diff changeset
296 /* Mask out the unrequired bits - mp_read_unsigned_bin expects
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
297 * MSB first.*/
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
298 randbuf[0] &= masks[size_bits % 8];
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
299
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
300 bytes_to_mp(rand, randbuf, len);
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
301
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
302 /* keep regenerating until we get one satisfying
c9483550701b - refactored random mp_int generation and byte->mp_int code
Matt Johnston <matt@ucc.asn.au>
parents: 159
diff changeset
303 * 0 < rand < max */
405
00703f1df67a Remove extraneous tests in random mpint generation,
Matt Johnston <matt@ucc.asn.au>
parents: 311
diff changeset
304 } while (mp_cmp(rand, max) != MP_LT);
188
c9483550701b - refactored random mp_int generation and byte->mp_int code
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parents: 159
diff changeset
305 m_burn(randbuf, len);
c9483550701b - refactored random mp_int generation and byte->mp_int code
Matt Johnston <matt@ucc.asn.au>
parents: 159
diff changeset
306 m_free(randbuf);
c9483550701b - refactored random mp_int generation and byte->mp_int code
Matt Johnston <matt@ucc.asn.au>
parents: 159
diff changeset
307 }