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 30 #include "ssh.h" 31 #include "misc.h" 32 #include "xmalloc.h" 33 #include "atomicio.h" 34 #include "pathnames.h" 35 #include "log.h" 36 37 /* 38 * Portable OpenSSH PRNG seeding: 39 * If OpenSSL has not "internally seeded" itself (e.g. pulled data from 40 * /dev/random), then we execute a "ssh-rand-helper" program which 41 * collects entropy and writes it to stdout. The child program must 42 * write at least RANDOM_SEED_SIZE bytes. The child is run with stderr 43 * attached, so error/debugging output should be visible. 44 * 45 * XXX: we should tell the child how many bytes we need. 46 */ 47 48 RCSID("$Id: entropy.c,v 1.44 2002/06/09 19:41:48 mouring Exp $"); 49 50 #ifndef OPENSSL_PRNG_ONLY 51 #define RANDOM_SEED_SIZE 48 52 static uid_t original_uid, original_euid; 53 #endif 54 55 void 56 seed_rng(void) 57 { 58 #ifndef OPENSSL_PRNG_ONLY 59 int devnull; 60 int p[2]; 61 pid_t pid; 62 int ret; 63 unsigned char buf[RANDOM_SEED_SIZE]; 64 mysig_t old_sigchld; 65 66 if (RAND_status() == 1) { 67 debug3("RNG is ready, skipping seeding"); 68 return; 69 } 70 71 debug3("Seeding PRNG from %s", SSH_RAND_HELPER); 72 73 if ((devnull = open("/dev/null", O_RDWR)) == -1) 74 fatal("Couldn't open /dev/null: %s", strerror(errno)); 75 if (pipe(p) == -1) 76 fatal("pipe: %s", strerror(errno)); 77 78 old_sigchld = mysignal(SIGCHLD, SIG_DFL); 79 if ((pid = fork()) == -1) 80 fatal("Couldn't fork: %s", strerror(errno)); 81 if (pid == 0) { 82 dup2(devnull, STDIN_FILENO); 83 dup2(p[1], STDOUT_FILENO); 84 /* Keep stderr open for errors */ 85 close(p[0]); 86 close(p[1]); 87 close(devnull); 88 89 if (original_uid != original_euid && 90 ( seteuid(getuid()) == -1 || 91 setuid(original_uid) == -1) ) { 92 fprintf(stderr, "(rand child) setuid(%d): %s\n", 93 original_uid, strerror(errno)); 94 _exit(1); 95 } 96 97 execl(SSH_RAND_HELPER, "ssh-rand-helper", NULL); 98 fprintf(stderr, "(rand child) Couldn't exec '%s': %s\n", 99 SSH_RAND_HELPER, strerror(errno)); 100 _exit(1); 101 } 102 103 close(devnull); 104 close(p[1]); 105 106 memset(buf, '\0', sizeof(buf)); 107 ret = atomicio(read, p[0], buf, sizeof(buf)); 108 if (ret == -1) 109 fatal("Couldn't read from ssh-rand-helper: %s", 110 strerror(errno)); 111 if (ret != sizeof(buf)) 112 fatal("ssh-rand-helper child produced insufficient data"); 113 114 close(p[0]); 115 116 if (waitpid(pid, &ret, 0) == -1) 117 fatal("Couldn't wait for ssh-rand-helper completion: %s", 118 strerror(errno)); 119 mysignal(SIGCHLD, old_sigchld); 120 121 /* We don't mind if the child exits upon a SIGPIPE */ 122 if (!WIFEXITED(ret) && 123 (!WIFSIGNALED(ret) || WTERMSIG(ret) != SIGPIPE)) 124 fatal("ssh-rand-helper terminated abnormally"); 125 if (WEXITSTATUS(ret) != 0) 126 fatal("ssh-rand-helper exit with exit status %d", ret); 127 128 RAND_add(buf, sizeof(buf), sizeof(buf)); 129 memset(buf, '\0', sizeof(buf)); 130 131 #endif /* OPENSSL_PRNG_ONLY */ 132 if (RAND_status() != 1) 133 fatal("PRNG is not seeded"); 134 } 135 136 void 137 init_rng(void) 138 { 139 /* 140 * OpenSSL version numbers: MNNFFPPS: major minor fix patch status 141 * We match major, minor, fix and status (not patch) 142 */ 143 if ((SSLeay() ^ OPENSSL_VERSION_NUMBER) & ~0xff0L) 144 fatal("OpenSSL version mismatch. Built against %lx, you " 145 "have %lx", OPENSSL_VERSION_NUMBER, SSLeay()); 146 147 #ifndef OPENSSL_PRNG_ONLY 148 if ((original_uid = getuid()) == -1) 149 fatal("getuid: %s", strerror(errno)); 150 if ((original_euid = geteuid()) == -1) 151 fatal("geteuid: %s", strerror(errno)); 152 #endif 153 } 154 155