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comparison random.c @ 272:3be7ae2e8dfa

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Only read /dev/random once when the program starts rather than for every connection, to "conserve entropy".
author Matt Johnston <matt@ucc.asn.au>
date Sat, 11 Feb 2006 15:15:37 +0000
parents 65585699d980
children 79bf1023cf11 7dad470ad4aa
comparison
equal deleted inserted replaced
271:be18c7dd486e 272:3be7ae2e8dfa
28 #include "bignum.h" 28 #include "bignum.h"
29 29
30 static int donerandinit = 0; 30 static int donerandinit = 0;
31 31
32 /* this is used to generate unique output from the same hashpool */ 32 /* this is used to generate unique output from the same hashpool */
33 static unsigned int counter = 0; 33 static uint32_t counter = 0;
34 #define MAX_COUNTER 1000000/* the max value for the counter, so it won't loop */ 34 #define MAX_COUNTER 1<<31 /* the max value for the counter, so it won't loop */
35 35
36 static unsigned char hashpool[SHA1_HASH_SIZE]; 36 static unsigned char hashpool[SHA1_HASH_SIZE];
37 37
38 #define INIT_SEED_SIZE 32 /* 256 bits */ 38 #define INIT_SEED_SIZE 32 /* 256 bits */
39 39
130 130
131 unsigned char readbuf[INIT_SEED_SIZE]; 131 unsigned char readbuf[INIT_SEED_SIZE];
132 132
133 hash_state hs; 133 hash_state hs;
134 134
135 /* initialise so compilers will be happy about hashing it */ 135 /* initialise so that things won't warn about
136 * hashing an undefined buffer */
136 if (!donerandinit) { 137 if (!donerandinit) {
137 m_burn(hashpool, sizeof(hashpool)); 138 m_burn(hashpool, sizeof(hashpool));
138 } 139 }
139 140
140 /* get the seed data */ 141 /* get the seed data */
146 sha1_process(&hs, (void*)readbuf, sizeof(readbuf)); 147 sha1_process(&hs, (void*)readbuf, sizeof(readbuf));
147 sha1_done(&hs, hashpool); 148 sha1_done(&hs, hashpool);
148 149
149 counter = 0; 150 counter = 0;
150 donerandinit = 1; 151 donerandinit = 1;
152 }
153
154 /* hash the current random pool with some unique identifiers
155 * for this process and point-in-time. this is used to separate
156 * the random pools for fork()ed processes. */
157 void reseedrandom() {
158
159 pid_t pid;
160 struct timeval tv;
161
162 if (!donerandinit) {
163 dropbear_exit("seedrandom not done");
164 }
165
166 pid = getpid();
167 gettimeofday(&tv, NULL);
168
169 hash_state hs;
170 unsigned char hash[SHA1_HASH_SIZE];
171 sha1_init(&hs);
172 sha1_process(&hs, (void*)hashpool, sizeof(hashpool));
173 sha1_process(&hs, (void*)&pid, sizeof(pid));
174 sha1_process(&hs, (void*)&tv, sizeof(tv));
175 sha1_done(&hs, hashpool);
151 } 176 }
152 177
153 /* return len bytes of pseudo-random data */ 178 /* return len bytes of pseudo-random data */
154 void genrandom(unsigned char* buf, unsigned int len) { 179 void genrandom(unsigned char* buf, unsigned int len) {
155 180