crypto/openssh/entropy.c

   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/socket.h>
  29 #ifdef HAVE_SYS_UN_H
  30 # include <sys/un.h>
  31 #endif
  32
  33 #include <netinet/in.h>
  34 #include <arpa/inet.h>
  35
  36 #include <errno.h>
  37 #include <signal.h>
  38 #include <string.h>
  39 #include <unistd.h>
  40 #include <stddef.h> /* for offsetof */
  41
  42 #include <openssl/rand.h>
  43 #include <openssl/crypto.h>
  44 #include <openssl/err.h>
  45
  46 #include "openbsd-compat/openssl-compat.h"
  47
  48 #include "ssh.h"
  49 #include "misc.h"
  50 #include "xmalloc.h"
  51 #include "atomicio.h"
  52 #include "pathnames.h"
  53 #include "log.h"
  54 #include "buffer.h"
  55
  56 /*
  57  * Portable OpenSSH PRNG seeding:
  58  * If OpenSSL has not "internally seeded" itself (e.g. pulled data from
  59  * /dev/random), then collect RANDOM_SEED_SIZE bytes of randomness from
  60  * PRNGd.
  61  */
  62 #ifndef OPENSSL_PRNG_ONLY
  63
  64 #define RANDOM_SEED_SIZE 48
  65
  66 /*
  67  * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
  68  * listening either on 'tcp_port', or via Unix domain socket at *
  69  * 'socket_path'.
  70  * Either a non-zero tcp_port or a non-null socket_path must be
  71  * supplied.
  72  * Returns 0 on success, -1 on error
  73  */
  74 int
  75 get_random_bytes_prngd(unsigned char *buf, int len,
  76     unsigned short tcp_port, char *socket_path)
  77 {
  78         int fd, addr_len, rval, errors;
  79         u_char msg[2];
  80         struct sockaddr_storage addr;
  81         struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
  82         struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
  83         mysig_t old_sigpipe;
  84
  85         /* Sanity checks */
  86         if (socket_path == NULL && tcp_port == 0)
  87                 fatal("You must specify a port or a socket");
  88         if (socket_path != NULL &&
  89             strlen(socket_path) >= sizeof(addr_un->sun_path))
  90                 fatal("Random pool path is too long");
  91         if (len <= 0 || len > 255)
  92                 fatal("Too many bytes (%d) to read from PRNGD", len);
  93
  94         memset(&addr, '\0', sizeof(addr));
  95
  96         if (tcp_port != 0) {
  97                 addr_in->sin_family = AF_INET;
  98                 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
  99                 addr_in->sin_port = htons(tcp_port);
 100                 addr_len = sizeof(*addr_in);
 101         } else {
 102                 addr_un->sun_family = AF_UNIX;
 103                 strlcpy(addr_un->sun_path, socket_path,
 104                     sizeof(addr_un->sun_path));
 105                 addr_len = offsetof(struct sockaddr_un, sun_path) +
 106                     strlen(socket_path) + 1;
 107         }
 108
 109         old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
 110
 111         errors = 0;
 112         rval = -1;
 113 reopen:
 114         fd = socket(addr.ss_family, SOCK_STREAM, 0);
 115         if (fd == -1) {
 116                 error("Couldn't create socket: %s", strerror(errno));
 117                 goto done;
 118         }
 119
 120         if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
 121                 if (tcp_port != 0) {
 122                         error("Couldn't connect to PRNGD port %d: %s",
 123                             tcp_port, strerror(errno));
 124                 } else {
 125                         error("Couldn't connect to PRNGD socket \"%s\": %s",
 126                             addr_un->sun_path, strerror(errno));
 127                 }
 128                 goto done;
 129         }
 130
 131         /* Send blocking read request to PRNGD */
 132         msg[0] = 0x02;
 133         msg[1] = len;
 134
 135         if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
 136                 if (errno == EPIPE && errors < 10) {
 137                         close(fd);
 138                         errors++;
 139                         goto reopen;
 140                 }
 141                 error("Couldn't write to PRNGD socket: %s",
 142                     strerror(errno));
 143                 goto done;
 144         }
 145
 146         if (atomicio(read, fd, buf, len) != (size_t)len) {
 147                 if (errno == EPIPE && errors < 10) {
 148                         close(fd);
 149                         errors++;
 150                         goto reopen;
 151                 }
 152                 error("Couldn't read from PRNGD socket: %s",
 153                     strerror(errno));
 154                 goto done;
 155         }
 156
 157         rval = 0;
 158 done:
 159         mysignal(SIGPIPE, old_sigpipe);
 160         if (fd != -1)
 161                 close(fd);
 162         return rval;
 163 }
 164
 165 static int
 166 seed_from_prngd(unsigned char *buf, size_t bytes)
 167 {
 168 #ifdef PRNGD_PORT
 169         debug("trying egd/prngd port %d", PRNGD_PORT);
 170         if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
 171                 return 0;
 172 #endif
 173 #ifdef PRNGD_SOCKET
 174         debug("trying egd/prngd socket %s", PRNGD_SOCKET);
 175         if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
 176                 return 0;
 177 #endif
 178         return -1;
 179 }
 180
 181 void
 182 rexec_send_rng_seed(Buffer *m)
 183 {
 184         u_char buf[RANDOM_SEED_SIZE];
 185
 186         if (RAND_bytes(buf, sizeof(buf)) <= 0) {
 187                 error("Couldn't obtain random bytes (error %ld)",
 188                     ERR_get_error());
 189                 buffer_put_string(m, "", 0);
 190         } else
 191                 buffer_put_string(m, buf, sizeof(buf));
 192 }
 193
 194 void
 195 rexec_recv_rng_seed(Buffer *m)
 196 {
 197         u_char *buf;
 198         u_int len;
 199
 200         buf = buffer_get_string_ret(m, &len);
 201         if (buf != NULL) {
 202                 debug3("rexec_recv_rng_seed: seeding rng with %u bytes", len);
 203                 RAND_add(buf, len, len);
 204         }
 205 }
 206 #endif /* OPENSSL_PRNG_ONLY */
 207
 208 void
 209 seed_rng(void)
 210 {
 211 #ifndef OPENSSL_PRNG_ONLY
 212         unsigned char buf[RANDOM_SEED_SIZE];
 213 #endif
 214         if (!ssh_compatible_openssl(OPENSSL_VERSION_NUMBER, SSLeay()))
 215                 fatal("OpenSSL version mismatch. Built against %lx, you "
 216                     "have %lx", (u_long)OPENSSL_VERSION_NUMBER, SSLeay());
 217
 218 #ifndef OPENSSL_PRNG_ONLY
 219         if (RAND_status() == 1) {
 220                 debug3("RNG is ready, skipping seeding");
 221                 return;
 222         }
 223
 224         if (seed_from_prngd(buf, sizeof(buf)) == -1)
 225                 fatal("Could not obtain seed from PRNGd");
 226         RAND_add(buf, sizeof(buf), sizeof(buf));
 227         memset(buf, '\0', sizeof(buf));
 228
 229 #endif /* OPENSSL_PRNG_ONLY */
 230         if (RAND_status() != 1)
 231                 fatal("PRNG is not seeded");
 232 }