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