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 #ifdef WITH_OPENSSL
  28
  29 #include <sys/types.h>
  30 #include <sys/socket.h>
  31 #ifdef HAVE_SYS_UN_H
  32 # include <sys/un.h>
  33 #endif
  34
  35 #include <netinet/in.h>
  36 #include <arpa/inet.h>
  37
  38 #include <errno.h>
  39 #include <signal.h>
  40 #include <string.h>
  41 #include <unistd.h>
  42 #include <stddef.h> /* for offsetof */
  43
  44 #include <openssl/rand.h>
  45 #include <openssl/crypto.h>
  46 #include <openssl/err.h>
  47
  48 #include "openbsd-compat/openssl-compat.h"
  49
  50 #include "ssh.h"
  51 #include "misc.h"
  52 #include "xmalloc.h"
  53 #include "atomicio.h"
  54 #include "pathnames.h"
  55 #include "log.h"
  56 #include "buffer.h"
  57
  58 /*
  59  * Portable OpenSSH PRNG seeding:
  60  * If OpenSSL has not "internally seeded" itself (e.g. pulled data from
  61  * /dev/random), then collect RANDOM_SEED_SIZE bytes of randomness from
  62  * PRNGd.
  63  */
  64 #ifndef OPENSSL_PRNG_ONLY
  65
  66 #define RANDOM_SEED_SIZE 48
  67
  68 /*
  69  * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon
  70  * listening either on 'tcp_port', or via Unix domain socket at *
  71  * 'socket_path'.
  72  * Either a non-zero tcp_port or a non-null socket_path must be
  73  * supplied.
  74  * Returns 0 on success, -1 on error
  75  */
  76 int
  77 get_random_bytes_prngd(unsigned char *buf, int len,
  78     unsigned short tcp_port, char *socket_path)
  79 {
  80         int fd, addr_len, rval, errors;
  81         u_char msg[2];
  82         struct sockaddr_storage addr;
  83         struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr;
  84         struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr;
  85         mysig_t old_sigpipe;
  86
  87         /* Sanity checks */
  88         if (socket_path == NULL && tcp_port == 0)
  89                 fatal("You must specify a port or a socket");
  90         if (socket_path != NULL &&
  91             strlen(socket_path) >= sizeof(addr_un->sun_path))
  92                 fatal("Random pool path is too long");
  93         if (len <= 0 || len > 255)
  94                 fatal("Too many bytes (%d) to read from PRNGD", len);
  95
  96         memset(&addr, '\0', sizeof(addr));
  97
  98         if (tcp_port != 0) {
  99                 addr_in->sin_family = AF_INET;
 100                 addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 101                 addr_in->sin_port = htons(tcp_port);
 102                 addr_len = sizeof(*addr_in);
 103         } else {
 104                 addr_un->sun_family = AF_UNIX;
 105                 strlcpy(addr_un->sun_path, socket_path,
 106                     sizeof(addr_un->sun_path));
 107                 addr_len = offsetof(struct sockaddr_un, sun_path) +
 108                     strlen(socket_path) + 1;
 109         }
 110
 111         old_sigpipe = mysignal(SIGPIPE, SIG_IGN);
 112
 113         errors = 0;
 114         rval = -1;
 115 reopen:
 116         fd = socket(addr.ss_family, SOCK_STREAM, 0);
 117         if (fd == -1) {
 118                 error("Couldn't create socket: %s", strerror(errno));
 119                 goto done;
 120         }
 121
 122         if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) {
 123                 if (tcp_port != 0) {
 124                         error("Couldn't connect to PRNGD port %d: %s",
 125                             tcp_port, strerror(errno));
 126                 } else {
 127                         error("Couldn't connect to PRNGD socket \"%s\": %s",
 128                             addr_un->sun_path, strerror(errno));
 129                 }
 130                 goto done;
 131         }
 132
 133         /* Send blocking read request to PRNGD */
 134         msg[0] = 0x02;
 135         msg[1] = len;
 136
 137         if (atomicio(vwrite, fd, msg, sizeof(msg)) != sizeof(msg)) {
 138                 if (errno == EPIPE && errors < 10) {
 139                         close(fd);
 140                         errors++;
 141                         goto reopen;
 142                 }
 143                 error("Couldn't write to PRNGD socket: %s",
 144                     strerror(errno));
 145                 goto done;
 146         }
 147
 148         if (atomicio(read, fd, buf, len) != (size_t)len) {
 149                 if (errno == EPIPE && errors < 10) {
 150                         close(fd);
 151                         errors++;
 152                         goto reopen;
 153                 }
 154                 error("Couldn't read from PRNGD socket: %s",
 155                     strerror(errno));
 156                 goto done;
 157         }
 158
 159         rval = 0;
 160 done:
 161         mysignal(SIGPIPE, old_sigpipe);
 162         if (fd != -1)
 163                 close(fd);
 164         return rval;
 165 }
 166
 167 static int
 168 seed_from_prngd(unsigned char *buf, size_t bytes)
 169 {
 170 #ifdef PRNGD_PORT
 171         debug("trying egd/prngd port %d", PRNGD_PORT);
 172         if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == 0)
 173                 return 0;
 174 #endif
 175 #ifdef PRNGD_SOCKET
 176         debug("trying egd/prngd socket %s", PRNGD_SOCKET);
 177         if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == 0)
 178                 return 0;
 179 #endif
 180         return -1;
 181 }
 182
 183 void
 184 rexec_send_rng_seed(Buffer *m)
 185 {
 186         u_char buf[RANDOM_SEED_SIZE];
 187
 188         if (RAND_bytes(buf, sizeof(buf)) <= 0) {
 189                 error("Couldn't obtain random bytes (error %ld)",
 190                     ERR_get_error());
 191                 buffer_put_string(m, "", 0);
 192         } else
 193                 buffer_put_string(m, buf, sizeof(buf));
 194 }
 195
 196 void
 197 rexec_recv_rng_seed(Buffer *m)
 198 {
 199         u_char *buf;
 200         u_int len;
 201
 202         buf = buffer_get_string_ret(m, &len);
 203         if (buf != NULL) {
 204                 debug3("rexec_recv_rng_seed: seeding rng with %u bytes", len);
 205                 RAND_add(buf, len, len);
 206         }
 207 }
 208 #endif /* OPENSSL_PRNG_ONLY */
 209
 210 void
 211 seed_rng(void)
 212 {
 213 #ifndef OPENSSL_PRNG_ONLY
 214         unsigned char buf[RANDOM_SEED_SIZE];
 215 #endif
 216         if (!ssh_compatible_openssl(OPENSSL_VERSION_NUMBER, SSLeay()))
 217                 fatal("OpenSSL version mismatch. Built against %lx, you "
 218                     "have %lx", (u_long)OPENSSL_VERSION_NUMBER, SSLeay());
 219
 220 #ifndef OPENSSL_PRNG_ONLY
 221         if (RAND_status() == 1) {
 222                 debug3("RNG is ready, skipping seeding");
 223                 return;
 224         }
 225
 226         if (seed_from_prngd(buf, sizeof(buf)) == -1)
 227                 fatal("Could not obtain seed from PRNGd");
 228         RAND_add(buf, sizeof(buf), sizeof(buf));
 229         memset(buf, '\0', sizeof(buf));
 230
 231 #endif /* OPENSSL_PRNG_ONLY */
 232         if (RAND_status() != 1)
 233                 fatal("PRNG is not seeded");
 234 }
 235
 236 #else /* WITH_OPENSSL */
 237
 238 /* Handled in arc4random() */
 239 void
 240 seed_rng(void)
 241 {
 242 }
 243
 244 #endif /* WITH_OPENSSL */