155 lines
4.5 KiB
C
155 lines
4.5 KiB
C
/*
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* Copyright (c) 2001 Damien Miller. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "includes.h"
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#include <openssl/rand.h>
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#include <openssl/crypto.h>
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#include "ssh.h"
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#include "misc.h"
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#include "xmalloc.h"
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#include "atomicio.h"
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#include "pathnames.h"
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#include "log.h"
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/*
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* Portable OpenSSH PRNG seeding:
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* If OpenSSL has not "internally seeded" itself (e.g. pulled data from
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* /dev/random), then we execute a "ssh-rand-helper" program which
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* collects entropy and writes it to stdout. The child program must
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* write at least RANDOM_SEED_SIZE bytes. The child is run with stderr
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* attached, so error/debugging output should be visible.
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*
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* XXX: we should tell the child how many bytes we need.
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*/
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RCSID("$Id: entropy.c,v 1.49 2005/07/17 07:26:44 djm Exp $");
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#ifndef OPENSSL_PRNG_ONLY
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#define RANDOM_SEED_SIZE 48
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static uid_t original_uid, original_euid;
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#endif
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void
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seed_rng(void)
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{
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#ifndef OPENSSL_PRNG_ONLY
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int devnull;
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int p[2];
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pid_t pid;
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int ret;
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unsigned char buf[RANDOM_SEED_SIZE];
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mysig_t old_sigchld;
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if (RAND_status() == 1) {
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debug3("RNG is ready, skipping seeding");
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return;
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}
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debug3("Seeding PRNG from %s", SSH_RAND_HELPER);
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if ((devnull = open("/dev/null", O_RDWR)) == -1)
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fatal("Couldn't open /dev/null: %s", strerror(errno));
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if (pipe(p) == -1)
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fatal("pipe: %s", strerror(errno));
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old_sigchld = signal(SIGCHLD, SIG_DFL);
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if ((pid = fork()) == -1)
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fatal("Couldn't fork: %s", strerror(errno));
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if (pid == 0) {
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dup2(devnull, STDIN_FILENO);
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dup2(p[1], STDOUT_FILENO);
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/* Keep stderr open for errors */
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close(p[0]);
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close(p[1]);
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close(devnull);
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if (original_uid != original_euid &&
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( seteuid(getuid()) == -1 ||
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setuid(original_uid) == -1) ) {
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fprintf(stderr, "(rand child) setuid(%li): %s\n",
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(long int)original_uid, strerror(errno));
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_exit(1);
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}
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execl(SSH_RAND_HELPER, "ssh-rand-helper", NULL);
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fprintf(stderr, "(rand child) Couldn't exec '%s': %s\n",
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SSH_RAND_HELPER, strerror(errno));
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_exit(1);
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}
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close(devnull);
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close(p[1]);
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memset(buf, '\0', sizeof(buf));
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ret = atomicio(read, p[0], buf, sizeof(buf));
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if (ret == -1)
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fatal("Couldn't read from ssh-rand-helper: %s",
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strerror(errno));
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if (ret != sizeof(buf))
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fatal("ssh-rand-helper child produced insufficient data");
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close(p[0]);
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if (waitpid(pid, &ret, 0) == -1)
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fatal("Couldn't wait for ssh-rand-helper completion: %s",
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strerror(errno));
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signal(SIGCHLD, old_sigchld);
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/* We don't mind if the child exits upon a SIGPIPE */
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if (!WIFEXITED(ret) &&
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(!WIFSIGNALED(ret) || WTERMSIG(ret) != SIGPIPE))
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fatal("ssh-rand-helper terminated abnormally");
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if (WEXITSTATUS(ret) != 0)
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fatal("ssh-rand-helper exit with exit status %d", ret);
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RAND_add(buf, sizeof(buf), sizeof(buf));
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memset(buf, '\0', sizeof(buf));
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#endif /* OPENSSL_PRNG_ONLY */
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if (RAND_status() != 1)
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fatal("PRNG is not seeded");
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}
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void
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init_rng(void)
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{
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/*
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* OpenSSL version numbers: MNNFFPPS: major minor fix patch status
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* We match major, minor, fix and status (not patch)
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*/
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if ((SSLeay() ^ OPENSSL_VERSION_NUMBER) & ~0xff0L)
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fatal("OpenSSL version mismatch. Built against %lx, you "
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"have %lx", OPENSSL_VERSION_NUMBER, SSLeay());
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#ifndef OPENSSL_PRNG_ONLY
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if ((original_uid = getuid()) == -1)
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fatal("getuid: %s", strerror(errno));
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if ((original_euid = geteuid()) == -1)
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fatal("geteuid: %s", strerror(errno));
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#endif
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}
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