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/*
* Copyright (c) 2001 Damien Miller. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
#include <sys/types.h>
#include <sys/wait.h>
#ifdef HAVE_SYS_STAT_H
# include <sys/stat.h>
#endif
#ifdef HAVE_FCNTL_H
# include <fcntl.h>
#endif
#include <stdarg.h>
#include <unistd.h>
#include <openssl/rand.h>
#include <openssl/crypto.h>
#include <openssl/err.h>
#include "ssh.h"
#include "misc.h"
#include "xmalloc.h"
#include "atomicio.h"
#include "pathnames.h"
#include "log.h"
#include "buffer.h"
/*
* Portable OpenSSH PRNG seeding:
* If OpenSSL has not "internally seeded" itself (e.g. pulled data from
* /dev/random), then we execute a "ssh-rand-helper" program which
* collects entropy and writes it to stdout. The child program must
* write at least RANDOM_SEED_SIZE bytes. The child is run with stderr
* attached, so error/debugging output should be visible.
*
* XXX: we should tell the child how many bytes we need.
*/
#ifndef OPENSSL_PRNG_ONLY
#define RANDOM_SEED_SIZE 48
static uid_t original_uid, original_euid;
#endif
void
seed_rng(void)
{
#ifndef OPENSSL_PRNG_ONLY
int devnull;
int p[2];
pid_t pid;
int ret;
unsigned char buf[RANDOM_SEED_SIZE];
mysig_t old_sigchld;
if (RAND_status() == 1) {
debug3("RNG is ready, skipping seeding");
return;
}
debug3("Seeding PRNG from %s", SSH_RAND_HELPER);
if ((devnull = open("/dev/null", O_RDWR)) == -1)
fatal("Couldn't open /dev/null: %s", strerror(errno));
if (pipe(p) == -1)
fatal("pipe: %s", strerror(errno));
old_sigchld = signal(SIGCHLD, SIG_DFL);
if ((pid = fork()) == -1)
fatal("Couldn't fork: %s", strerror(errno));
if (pid == 0) {
dup2(devnull, STDIN_FILENO);
dup2(p[1], STDOUT_FILENO);
/* Keep stderr open for errors */
close(p[0]);
close(p[1]);
close(devnull);
if (original_uid != original_euid &&
( seteuid(getuid()) == -1 ||
setuid(original_uid) == -1) ) {
fprintf(stderr, "(rand child) setuid(%li): %s\n",
(long int)original_uid, strerror(errno));
_exit(1);
}
execl(SSH_RAND_HELPER, "ssh-rand-helper", NULL);
fprintf(stderr, "(rand child) Couldn't exec '%s': %s\n",
SSH_RAND_HELPER, strerror(errno));
_exit(1);
}
close(devnull);
close(p[1]);
memset(buf, '\0', sizeof(buf));
ret = atomicio(read, p[0], buf, sizeof(buf));
if (ret == -1)
fatal("Couldn't read from ssh-rand-helper: %s",
strerror(errno));
if (ret != sizeof(buf))
fatal("ssh-rand-helper child produced insufficient data");
close(p[0]);
if (waitpid(pid, &ret, 0) == -1)
fatal("Couldn't wait for ssh-rand-helper completion: %s",
strerror(errno));
signal(SIGCHLD, old_sigchld);
/* We don't mind if the child exits upon a SIGPIPE */
if (!WIFEXITED(ret) &&
(!WIFSIGNALED(ret) || WTERMSIG(ret) != SIGPIPE))
fatal("ssh-rand-helper terminated abnormally");
if (WEXITSTATUS(ret) != 0)
fatal("ssh-rand-helper exit with exit status %d", ret);
RAND_add(buf, sizeof(buf), sizeof(buf));
memset(buf, '\0', sizeof(buf));
#endif /* OPENSSL_PRNG_ONLY */
if (RAND_status() != 1)
fatal("PRNG is not seeded");
}
void
init_rng(void)
{
/*
* OpenSSL version numbers: MNNFFPPS: major minor fix patch status
* We match major, minor, fix and status (not patch)
*/
if ((SSLeay() ^ OPENSSL_VERSION_NUMBER) & ~0xff0L)
fatal("OpenSSL version mismatch. Built against %lx, you "
"have %lx", OPENSSL_VERSION_NUMBER, SSLeay());
#ifndef OPENSSL_PRNG_ONLY
original_uid = getuid();
original_euid = geteuid();
#endif
}
#ifndef OPENSSL_PRNG_ONLY
void
rexec_send_rng_seed(Buffer *m)
{
u_char buf[RANDOM_SEED_SIZE];
if (RAND_bytes(buf, sizeof(buf)) <= 0) {
error("Couldn't obtain random bytes (error %ld)",
ERR_get_error());
buffer_put_string(m, "", 0);
} else
buffer_put_string(m, buf, sizeof(buf));
}
void
rexec_recv_rng_seed(Buffer *m)
{
u_char *buf;
u_int len;
buf = buffer_get_string_ret(m, &len);
if (buf != NULL) {
debug3("rexec_recv_rng_seed: seeding rng with %u bytes", len);
RAND_add(buf, len, len);
}
}
#endif
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