Mercurial > dropbear
annotate random.c @ 694:c85bb68e1db6
add loadavg and entropy_avail as sources
author | Matt Johnston <matt@ucc.asn.au> |
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date | Sat, 23 Feb 2013 10:27:49 +0800 |
parents | c3de235d9506 |
children | 5f2d16d3e598 |
rev | line source |
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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 |
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30 /* this is used to generate unique output from the same hashpool */ |
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31 static uint32_t counter = 0; |
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32 /* the max value for the counter, so it won't integer overflow */ |
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33 #define MAX_COUNTER 1<<30 |
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34 |
687 | 35 static unsigned char hashpool[SHA1_HASH_SIZE] = {0}; |
36 static int donerandinit = 0; | |
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37 |
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38 #define INIT_SEED_SIZE 32 /* 256 bits */ |
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39 |
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40 /* The basic setup is we read some data from /dev/(u)random or prngd and hash it |
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41 * into hashpool. To read data, we hash together current hashpool contents, |
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42 * and a counter. We feed more data in by hashing the current pool and new |
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43 * data into the pool. |
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44 * |
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45 * It is important to ensure that counter doesn't wrap around before we |
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46 * feed in new entropy. |
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47 * |
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48 */ |
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49 |
687 | 50 /* Pass len=0 to hash an entire file */ |
51 static int | |
52 process_file(hash_state *hs, const char *filename, | |
53 unsigned int len, int prngd) | |
54 { | |
185
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55 static int already_blocked = 0; |
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56 int readfd; |
687 | 57 unsigned int readcount; |
58 int ret = DROPBEAR_FAILURE; | |
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59 |
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60 #ifdef DROPBEAR_PRNGD_SOCKET |
687 | 61 if (prngd) |
62 { | |
63 readfd = connect_unix(filename); | |
64 } | |
65 else | |
66 #endif | |
67 { | |
68 readfd = open(filename, O_RDONLY); | |
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69 } |
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70 |
687 | 71 if (readfd < 0) { |
72 goto out; | |
73 } | |
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74 |
687 | 75 readcount = 0; |
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76 while (len == 0 || readcount < len) |
687 | 77 { |
78 int readlen, wantread; | |
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79 unsigned char readbuf[2048]; |
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80 if (!already_blocked) |
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81 { |
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82 int ret; |
687 | 83 struct timeval timeout = { .tv_sec = 2, .tv_usec = 0}; |
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84 fd_set read_fds; |
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85 |
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86 FD_ZERO(&read_fds); |
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87 FD_SET(readfd, &read_fds); |
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88 ret = select(readfd + 1, &read_fds, NULL, NULL, &timeout); |
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89 if (ret == 0) |
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90 { |
687 | 91 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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92 already_blocked = 1; |
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93 } |
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94 } |
687 | 95 |
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96 if (len == 0) |
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97 { |
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98 wantread = sizeof(readbuf); |
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99 } |
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100 else |
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101 { |
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102 wantread = MIN(sizeof(readbuf), len-readcount); |
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103 } |
687 | 104 |
105 #ifdef DROPBEAR_PRNGD_SOCKET | |
106 if (prngd) | |
107 { | |
108 char egdcmd[2]; | |
109 egdcmd[0] = 0x02; /* blocking read */ | |
110 egdcmd[1] = (unsigned char)wantread; | |
111 if (write(readfd, egdcmd, 2) < 0) | |
112 { | |
113 dropbear_exit("Can't send command to egd"); | |
114 } | |
115 } | |
116 #endif | |
117 | |
118 readlen = read(readfd, readbuf, wantread); | |
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119 if (readlen <= 0) { |
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120 if (readlen < 0 && errno == EINTR) { |
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121 continue; |
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122 } |
687 | 123 if (readlen == 0 && len == 0) |
124 { | |
125 /* whole file was read as requested */ | |
126 break; | |
127 } | |
128 goto out; | |
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129 } |
687 | 130 sha1_process(hs, readbuf, readlen); |
131 readcount += readlen; | |
132 } | |
133 ret = DROPBEAR_SUCCESS; | |
134 out: | |
135 close(readfd); | |
136 return ret; | |
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137 } |
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138 |
687 | 139 void addrandom(char * buf, int len) |
140 { | |
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141 hash_state hs; |
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142 |
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143 /* hash in the new seed data */ |
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144 sha1_init(&hs); |
687 | 145 /* existing state (zeroes on startup) */ |
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146 sha1_process(&hs, (void*)hashpool, sizeof(hashpool)); |
687 | 147 |
148 /* new */ | |
149 sha1_process(&hs, buf, len); | |
150 sha1_done(&hs, hashpool); | |
151 } | |
152 | |
153 static void write_urandom() | |
154 { | |
155 #ifndef DROPBEAR_PRNGD_SOCKET | |
156 /* This is opportunistic, don't worry about failure */ | |
157 unsigned char buf[INIT_SEED_SIZE]; | |
158 FILE *f = fopen(DROPBEAR_URANDOM_DEV, "w"); | |
159 genrandom(buf, sizeof(buf)); | |
160 fwrite(buf, sizeof(buf), 1, f); | |
161 fclose(f); | |
162 #endif | |
163 } | |
164 | |
165 /* Initialise the prng from /dev/urandom or prngd. This function can | |
166 * be called multiple times */ | |
167 void seedrandom() { | |
168 | |
169 hash_state hs; | |
170 | |
171 pid_t pid; | |
172 struct timeval tv; | |
173 clock_t clockval; | |
174 | |
175 /* hash in the new seed data */ | |
176 sha1_init(&hs); | |
177 /* existing state */ | |
178 sha1_process(&hs, (void*)hashpool, sizeof(hashpool)); | |
179 | |
180 #ifdef DROPBEAR_PRNGD_SOCKET | |
181 if (process_file(&hs, DROPBEAR_PRNGD_SOCKET, INIT_SEED_SIZE, 1) | |
182 != DROPBEAR_SUCCESS) { | |
183 dropbear_exit("Failure reading random device %s", | |
184 DROPBEAR_PRNGD_SOCKET); | |
185 } | |
186 #else | |
187 /* non-blocking random source (probably /dev/urandom) */ | |
188 if (process_file(&hs, DROPBEAR_URANDOM_DEV, INIT_SEED_SIZE, 0) | |
189 != DROPBEAR_SUCCESS) { | |
190 dropbear_exit("Failure reading random device %s", | |
191 DROPBEAR_URANDOM_DEV); | |
192 } | |
193 #endif | |
194 | |
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195 /* A few other sources to fall back on. |
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196 * Add more here for other platforms */ |
687 | 197 #ifdef __linux__ |
688
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198 /* Seems to be a reasonable source of entropy from timers. Possibly hard |
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199 * for even local attackers to reproduce */ |
687 | 200 process_file(&hs, "/proc/timer_list", 0, 0); |
201 /* Might help on systems with wireless */ | |
202 process_file(&hs, "/proc/interrupts", 0, 0); | |
688
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203 |
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204 process_file(&hs, "/proc/loadavg", 0, 0); |
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205 process_file(&hs, "/proc/sys/kernel/random/entropy_avail", 0, 0); |
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206 |
688
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207 /* Mostly network visible but useful in some situations */ |
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208 process_file(&hs, "/proc/net/netstat", 0, 0); |
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209 process_file(&hs, "/proc/net/dev", 0, 0); |
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210 process_file(&hs, "/proc/net/tcp", 0, 0); |
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211 /* Also includes interface lo */ |
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212 process_file(&hs, "/proc/net/rt_cache", 0, 0); |
687 | 213 #endif |
214 | |
215 pid = getpid(); | |
216 sha1_process(&hs, (void*)&pid, sizeof(pid)); | |
217 | |
218 gettimeofday(&tv, NULL); | |
219 sha1_process(&hs, (void*)&tv, sizeof(tv)); | |
220 | |
221 clockval = clock(); | |
222 sha1_process(&hs, (void*)&clockval, sizeof(clockval)); | |
223 | |
224 /* When a private key is read by the client or server it will | |
225 * be added to the hashpool - see runopts.c */ | |
226 | |
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227 sha1_done(&hs, hashpool); |
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228 |
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229 counter = 0; |
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230 donerandinit = 1; |
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231 |
687 | 232 /* Feed it all back into /dev/urandom - this might help if Dropbear |
233 * is running from inetd and gets new state each time */ | |
234 write_urandom(); | |
272
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235 } |
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236 |
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237 /* return len bytes of pseudo-random data */ |
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238 void genrandom(unsigned char* buf, unsigned int len) { |
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239 |
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240 hash_state hs; |
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241 unsigned char hash[SHA1_HASH_SIZE]; |
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242 unsigned int copylen; |
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243 |
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244 if (!donerandinit) { |
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245 dropbear_exit("seedrandom not done"); |
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246 } |
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247 |
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248 while (len > 0) { |
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249 sha1_init(&hs); |
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250 sha1_process(&hs, (void*)hashpool, sizeof(hashpool)); |
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251 sha1_process(&hs, (void*)&counter, sizeof(counter)); |
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252 sha1_done(&hs, hash); |
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253 |
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254 counter++; |
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255 if (counter > MAX_COUNTER) { |
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256 seedrandom(); |
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257 } |
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258 |
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259 copylen = MIN(len, SHA1_HASH_SIZE); |
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260 memcpy(buf, hash, copylen); |
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261 len -= copylen; |
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262 buf += copylen; |
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263 } |
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264 m_burn(hash, sizeof(hash)); |
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265 } |
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266 |
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267 /* Generates a random mp_int. |
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268 * max is a *mp_int specifying an upper bound. |
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269 * rand must be an initialised *mp_int for the result. |
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270 * the result rand satisfies: 0 < rand < max |
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271 * */ |
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272 void gen_random_mpint(mp_int *max, mp_int *rand) { |
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273 |
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274 unsigned char *randbuf = NULL; |
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275 unsigned int len = 0; |
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276 const unsigned char masks[] = {0xff, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f}; |
188
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277 |
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278 const int size_bits = mp_count_bits(max); |
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279 |
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280 len = size_bits / 8; |
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281 if ((size_bits % 8) != 0) { |
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282 len += 1; |
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283 } |
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284 |
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285 randbuf = (unsigned char*)m_malloc(len); |
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286 do { |
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287 genrandom(randbuf, len); |
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288 /* Mask out the unrequired bits - mp_read_unsigned_bin expects |
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289 * MSB first.*/ |
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290 randbuf[0] &= masks[size_bits % 8]; |
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291 |
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292 bytes_to_mp(rand, randbuf, len); |
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293 |
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294 /* keep regenerating until we get one satisfying |
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295 * 0 < rand < max */ |
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296 } while (mp_cmp(rand, max) != MP_LT); |
188
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297 m_burn(randbuf, len); |
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298 m_free(randbuf); |
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299 } |