1 /* 2 * Copyright (c) 2001 Damien Miller. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 23 */ 24 25 #include "includes.h" 26 27 #include <openssl/rand.h> 28 #include <openssl/crypto.h> 29 #include <openssl/err.h> 30 31 #include "ssh.h" 32 #include "misc.h" 33 #include "xmalloc.h" 34 #include "atomicio.h" 35 #include "pathnames.h" 36 #include "log.h" 37 #include "buffer.h" 38 #include "bufaux.h" 39 40 /* 41 * Portable OpenSSH PRNG seeding: 42 * If OpenSSL has not "internally seeded" itself (e.g. pulled data from 43 * /dev/random), then we execute a "ssh-rand-helper" program which 44 * collects entropy and writes it to stdout. The child program must 45 * write at least RANDOM_SEED_SIZE bytes. The child is run with stderr 46 * attached, so error/debugging output should be visible. 47 * 48 * XXX: we should tell the child how many bytes we need. 49 */ 50 51 RCSID("$Id: entropy.c,v 1.52 2005/09/27 22:26:30 dtucker Exp $"); 52 53 #ifndef OPENSSL_PRNG_ONLY 54 #define RANDOM_SEED_SIZE 48 55 static uid_t original_uid, original_euid; 56 #endif 57 58 void 59 seed_rng(void) 60 { 61 #ifndef OPENSSL_PRNG_ONLY 62 int devnull; 63 int p[2]; 64 pid_t pid; 65 int ret; 66 unsigned char buf[RANDOM_SEED_SIZE]; 67 mysig_t old_sigchld; 68 69 if (RAND_status() == 1) { 70 debug3("RNG is ready, skipping seeding"); 71 return; 72 } 73 74 debug3("Seeding PRNG from %s", SSH_RAND_HELPER); 75 76 if ((devnull = open("/dev/null", O_RDWR)) == -1) 77 fatal("Couldn't open /dev/null: %s", strerror(errno)); 78 if (pipe(p) == -1) 79 fatal("pipe: %s", strerror(errno)); 80 81 old_sigchld = signal(SIGCHLD, SIG_DFL); 82 if ((pid = fork()) == -1) 83 fatal("Couldn't fork: %s", strerror(errno)); 84 if (pid == 0) { 85 dup2(devnull, STDIN_FILENO); 86 dup2(p[1], STDOUT_FILENO); 87 /* Keep stderr open for errors */ 88 close(p[0]); 89 close(p[1]); 90 close(devnull); 91 92 if (original_uid != original_euid && 93 ( seteuid(getuid()) == -1 || 94 setuid(original_uid) == -1) ) { 95 fprintf(stderr, "(rand child) setuid(%li): %s\n", 96 (long int)original_uid, strerror(errno)); 97 _exit(1); 98 } 99 100 execl(SSH_RAND_HELPER, "ssh-rand-helper", NULL); 101 fprintf(stderr, "(rand child) Couldn't exec '%s': %s\n", 102 SSH_RAND_HELPER, strerror(errno)); 103 _exit(1); 104 } 105 106 close(devnull); 107 close(p[1]); 108 109 memset(buf, '\0', sizeof(buf)); 110 ret = atomicio(read, p[0], buf, sizeof(buf)); 111 if (ret == -1) 112 fatal("Couldn't read from ssh-rand-helper: %s", 113 strerror(errno)); 114 if (ret != sizeof(buf)) 115 fatal("ssh-rand-helper child produced insufficient data"); 116 117 close(p[0]); 118 119 if (waitpid(pid, &ret, 0) == -1) 120 fatal("Couldn't wait for ssh-rand-helper completion: %s", 121 strerror(errno)); 122 signal(SIGCHLD, old_sigchld); 123 124 /* We don't mind if the child exits upon a SIGPIPE */ 125 if (!WIFEXITED(ret) && 126 (!WIFSIGNALED(ret) || WTERMSIG(ret) != SIGPIPE)) 127 fatal("ssh-rand-helper terminated abnormally"); 128 if (WEXITSTATUS(ret) != 0) 129 fatal("ssh-rand-helper exit with exit status %d", ret); 130 131 RAND_add(buf, sizeof(buf), sizeof(buf)); 132 memset(buf, '\0', sizeof(buf)); 133 134 #endif /* OPENSSL_PRNG_ONLY */ 135 if (RAND_status() != 1) 136 fatal("PRNG is not seeded"); 137 } 138 139 void 140 init_rng(void) 141 { 142 /* 143 * OpenSSL version numbers: MNNFFPPS: major minor fix patch status 144 * We match major, minor, fix and status (not patch) 145 */ 146 if ((SSLeay() ^ OPENSSL_VERSION_NUMBER) & ~0xff0L) 147 fatal("OpenSSL version mismatch. Built against %lx, you " 148 "have %lx", OPENSSL_VERSION_NUMBER, SSLeay()); 149 150 #ifndef OPENSSL_PRNG_ONLY 151 original_uid = getuid(); 152 original_euid = geteuid(); 153 #endif 154 } 155 156 #ifndef OPENSSL_PRNG_ONLY 157 void 158 rexec_send_rng_seed(Buffer *m) 159 { 160 u_char buf[RANDOM_SEED_SIZE]; 161 162 if (RAND_bytes(buf, sizeof(buf)) <= 0) { 163 error("Couldn't obtain random bytes (error %ld)", 164 ERR_get_error()); 165 buffer_put_string(m, "", 0); 166 } else 167 buffer_put_string(m, buf, sizeof(buf)); 168 } 169 170 void 171 rexec_recv_rng_seed(Buffer *m) 172 { 173 u_char *buf; 174 u_int len; 175 176 buf = buffer_get_string_ret(m, &len); 177 if (buf != NULL) { 178 debug3("rexec_recv_rng_seed: seeding rng with %u bytes", len); 179 RAND_add(buf, len, len); 180 } 181 } 182 #endif 183