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