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 <sys/types.h> 28 #include <sys/wait.h> 29 30 #ifdef HAVE_SYS_STAT_H 31 # include <sys/stat.h> 32 #endif 33 34 #ifdef HAVE_FCNTL_H 35 # include <fcntl.h> 36 #endif 37 #include <stdarg.h> 38 #include <string.h> 39 #include <signal.h> 40 #include <unistd.h> 41 42 #include <openssl/rand.h> 43 #include <openssl/crypto.h> 44 #include <openssl/err.h> 45 46 #include "ssh.h" 47 #include "misc.h" 48 #include "xmalloc.h" 49 #include "atomicio.h" 50 #include "pathnames.h" 51 #include "log.h" 52 #include "buffer.h" 53 54 /* 55 * Portable OpenSSH PRNG seeding: 56 * If OpenSSL has not "internally seeded" itself (e.g. pulled data from 57 * /dev/random), then we execute a "ssh-rand-helper" program which 58 * collects entropy and writes it to stdout. The child program must 59 * write at least RANDOM_SEED_SIZE bytes. The child is run with stderr 60 * attached, so error/debugging output should be visible. 61 * 62 * XXX: we should tell the child how many bytes we need. 63 */ 64 65 #ifndef OPENSSL_PRNG_ONLY 66 #define RANDOM_SEED_SIZE 48 67 static uid_t original_uid, original_euid; 68 #endif 69 70 void 71 seed_rng(void) 72 { 73 #ifndef OPENSSL_PRNG_ONLY 74 int devnull; 75 int p[2]; 76 pid_t pid; 77 int ret; 78 unsigned char buf[RANDOM_SEED_SIZE]; 79 mysig_t old_sigchld; 80 81 if (RAND_status() == 1) { 82 debug3("RNG is ready, skipping seeding"); 83 return; 84 } 85 86 debug3("Seeding PRNG from %s", SSH_RAND_HELPER); 87 88 if ((devnull = open("/dev/null", O_RDWR)) == -1) 89 fatal("Couldn't open /dev/null: %s", strerror(errno)); 90 if (pipe(p) == -1) 91 fatal("pipe: %s", strerror(errno)); 92 93 old_sigchld = signal(SIGCHLD, SIG_DFL); 94 if ((pid = fork()) == -1) 95 fatal("Couldn't fork: %s", strerror(errno)); 96 if (pid == 0) { 97 dup2(devnull, STDIN_FILENO); 98 dup2(p[1], STDOUT_FILENO); 99 /* Keep stderr open for errors */ 100 close(p[0]); 101 close(p[1]); 102 close(devnull); 103 closefrom(STDERR_FILENO + 1); 104 105 if (original_uid != original_euid && 106 ( seteuid(getuid()) == -1 || 107 setuid(original_uid) == -1) ) { 108 fprintf(stderr, "(rand child) setuid(%li): %s\n", 109 (long int)original_uid, strerror(errno)); 110 _exit(1); 111 } 112 113 execl(SSH_RAND_HELPER, "ssh-rand-helper", NULL); 114 fprintf(stderr, "(rand child) Couldn't exec '%s': %s\n", 115 SSH_RAND_HELPER, strerror(errno)); 116 _exit(1); 117 } 118 119 close(devnull); 120 close(p[1]); 121 122 memset(buf, '\0', sizeof(buf)); 123 ret = atomicio(read, p[0], buf, sizeof(buf)); 124 if (ret == -1) 125 fatal("Couldn't read from ssh-rand-helper: %s", 126 strerror(errno)); 127 if (ret != sizeof(buf)) 128 fatal("ssh-rand-helper child produced insufficient data"); 129 130 close(p[0]); 131 132 if (waitpid(pid, &ret, 0) == -1) 133 fatal("Couldn't wait for ssh-rand-helper completion: %s", 134 strerror(errno)); 135 signal(SIGCHLD, old_sigchld); 136 137 /* We don't mind if the child exits upon a SIGPIPE */ 138 if (!WIFEXITED(ret) && 139 (!WIFSIGNALED(ret) || WTERMSIG(ret) != SIGPIPE)) 140 fatal("ssh-rand-helper terminated abnormally"); 141 if (WEXITSTATUS(ret) != 0) 142 fatal("ssh-rand-helper exit with exit status %d", ret); 143 144 RAND_add(buf, sizeof(buf), sizeof(buf)); 145 memset(buf, '\0', sizeof(buf)); 146 147 #endif /* OPENSSL_PRNG_ONLY */ 148 if (RAND_status() != 1) 149 fatal("PRNG is not seeded"); 150 } 151 152 void 153 init_rng(void) 154 { 155 /* 156 * OpenSSL version numbers: MNNFFPPS: major minor fix patch status 157 * We match major, minor, fix and status (not patch) 158 */ 159 if ((SSLeay() ^ OPENSSL_VERSION_NUMBER) & ~0xff0L) 160 fatal("OpenSSL version mismatch. Built against %lx, you " 161 "have %lx", (u_long)OPENSSL_VERSION_NUMBER, SSLeay()); 162 163 #ifndef OPENSSL_PRNG_ONLY 164 original_uid = getuid(); 165 original_euid = geteuid(); 166 #endif 167 } 168 169 #ifndef OPENSSL_PRNG_ONLY 170 void 171 rexec_send_rng_seed(Buffer *m) 172 { 173 u_char buf[RANDOM_SEED_SIZE]; 174 175 if (RAND_bytes(buf, sizeof(buf)) <= 0) { 176 error("Couldn't obtain random bytes (error %ld)", 177 ERR_get_error()); 178 buffer_put_string(m, "", 0); 179 } else 180 buffer_put_string(m, buf, sizeof(buf)); 181 } 182 183 void 184 rexec_recv_rng_seed(Buffer *m) 185 { 186 u_char *buf; 187 u_int len; 188 189 buf = buffer_get_string_ret(m, &len); 190 if (buf != NULL) { 191 debug3("rexec_recv_rng_seed: seeding rng with %u bytes", len); 192 RAND_add(buf, len, len); 193 } 194 } 195 #endif 196