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/* $OpenBSD: sshd.c,v 1.605 2024/06/01 07:03:37 djm Exp $ */
/*
* Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved.
* Copyright (c) 2002 Niels Provos. 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/ioctl.h>
#include <sys/socket.h>
#ifdef HAVE_SYS_STAT_H
# include <sys/stat.h>
#endif
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
#endif
#include "openbsd-compat/sys-tree.h"
#include "openbsd-compat/sys-queue.h"
#include <sys/wait.h>
#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#ifdef HAVE_PATHS_H
#include <paths.h>
#endif
#include <grp.h>
#ifdef HAVE_POLL_H
#include <poll.h>
#endif
#include <pwd.h>
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#ifdef WITH_OPENSSL
#include <openssl/evp.h>
#include <openssl/rand.h>
#include "openbsd-compat/openssl-compat.h"
#endif
#ifdef HAVE_SECUREWARE
#include <sys/security.h>
#include <prot.h>
#endif
#include "xmalloc.h"
#include "ssh.h"
#include "sshpty.h"
#include "log.h"
#include "sshbuf.h"
#include "misc.h"
#include "servconf.h"
#include "compat.h"
#include "digest.h"
#include "sshkey.h"
#include "authfile.h"
#include "pathnames.h"
#include "canohost.h"
#include "hostfile.h"
#include "auth.h"
#include "authfd.h"
#include "msg.h"
#include "version.h"
#include "ssherr.h"
#include "sk-api.h"
#include "srclimit.h"
/* Re-exec fds */
#define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1)
#define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2)
#define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3)
#define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4)
extern char *__progname;
/* Server configuration options. */
ServerOptions options;
/*
* Debug mode flag. This can be set on the command line. If debug
* mode is enabled, extra debugging output will be sent to the system
* log, the daemon will not go to background, and will exit after processing
* the first connection.
*/
int debug_flag = 0;
/* Saved arguments to main(). */
static char **saved_argv;
static int saved_argc;
/*
* The sockets that the server is listening; this is used in the SIGHUP
* signal handler.
*/
#define MAX_LISTEN_SOCKS 16
static int listen_socks[MAX_LISTEN_SOCKS];
static int num_listen_socks = 0;
/*
* Any really sensitive data in the application is contained in this
* structure. The idea is that this structure could be locked into memory so
* that the pages do not get written into swap. However, there are some
* problems. The private key contains BIGNUMs, and we do not (in principle)
* have access to the internals of them, and locking just the structure is
* not very useful. Currently, memory locking is not implemented.
*/
struct {
struct sshkey **host_keys; /* all private host keys */
struct sshkey **host_pubkeys; /* all public host keys */
struct sshkey **host_certificates; /* all public host certificates */
int have_ssh2_key;
} sensitive_data;
/* This is set to true when a signal is received. */
static volatile sig_atomic_t received_sighup = 0;
static volatile sig_atomic_t received_sigterm = 0;
/* record remote hostname or ip */
u_int utmp_len = HOST_NAME_MAX+1;
/*
* startup_pipes/flags are used for tracking children of the listening sshd
* process early in their lifespans. This tracking is needed for three things:
*
* 1) Implementing the MaxStartups limit of concurrent unauthenticated
* connections.
* 2) Avoiding a race condition for SIGHUP processing, where child processes
* may have listen_socks open that could collide with main listener process
* after it restarts.
* 3) Ensuring that rexec'd sshd processes have received their initial state
* from the parent listen process before handling SIGHUP.
*
* Child processes signal that they have completed closure of the listen_socks
* and (if applicable) received their rexec state by sending a char over their
* sock. Child processes signal that authentication has completed by closing
* the sock (or by exiting).
*/
static int *startup_pipes = NULL;
static int *startup_flags = NULL; /* Indicates child closed listener */
static int startup_pipe = -1; /* in child */
/* sshd_config buffer */
struct sshbuf *cfg;
/* Included files from the configuration file */
struct include_list includes = TAILQ_HEAD_INITIALIZER(includes);
/* message to be displayed after login */
struct sshbuf *loginmsg;
/* Unprivileged user */
struct passwd *privsep_pw = NULL;
static char *listener_proctitle;
/*
* Close all listening sockets
*/
static void
close_listen_socks(void)
{
int i;
for (i = 0; i < num_listen_socks; i++)
close(listen_socks[i]);
num_listen_socks = 0;
}
static void
close_startup_pipes(void)
{
int i;
if (startup_pipes)
for (i = 0; i < options.max_startups; i++)
if (startup_pipes[i] != -1)
close(startup_pipes[i]);
}
/*
* Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
* the effect is to reread the configuration file (and to regenerate
* the server key).
*/
static void
sighup_handler(int sig)
{
received_sighup = 1;
}
/*
* Called from the main program after receiving SIGHUP.
* Restarts the server.
*/
static void
sighup_restart(void)
{
logit("Received SIGHUP; restarting.");
if (options.pid_file != NULL)
unlink(options.pid_file);
platform_pre_restart();
close_listen_socks();
close_startup_pipes();
ssh_signal(SIGHUP, SIG_IGN); /* will be restored after exec */
execv(saved_argv[0], saved_argv);
logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
strerror(errno));
exit(1);
}
/*
* Generic signal handler for terminating signals in the master daemon.
*/
static void
sigterm_handler(int sig)
{
received_sigterm = sig;
}
/*
* SIGCHLD handler. This is called whenever a child dies. This will then
* reap any zombies left by exited children.
*/
static void
main_sigchld_handler(int sig)
{
int save_errno = errno;
pid_t pid;
int status;
while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
(pid == -1 && errno == EINTR))
;
errno = save_errno;
}
/*
* returns 1 if connection should be dropped, 0 otherwise.
* dropping starts at connection #max_startups_begin with a probability
* of (max_startups_rate/100). the probability increases linearly until
* all connections are dropped for startups > max_startups
*/
static int
should_drop_connection(int startups)
{
int p, r;
if (startups < options.max_startups_begin)
return 0;
if (startups >= options.max_startups)
return 1;
if (options.max_startups_rate == 100)
return 1;
p = 100 - options.max_startups_rate;
p *= startups - options.max_startups_begin;
p /= options.max_startups - options.max_startups_begin;
p += options.max_startups_rate;
r = arc4random_uniform(100);
debug_f("p %d, r %d", p, r);
return (r < p) ? 1 : 0;
}
/*
* Check whether connection should be accepted by MaxStartups.
* Returns 0 if the connection is accepted. If the connection is refused,
* returns 1 and attempts to send notification to client.
* Logs when the MaxStartups condition is entered or exited, and periodically
* while in that state.
*/
static int
drop_connection(int sock, int startups, int notify_pipe)
{
char *laddr, *raddr;
const char msg[] = "Exceeded MaxStartups\r\n";
static time_t last_drop, first_drop;
static u_int ndropped;
LogLevel drop_level = SYSLOG_LEVEL_VERBOSE;
time_t now;
now = monotime();
if (!should_drop_connection(startups) &&
srclimit_check_allow(sock, notify_pipe) == 1) {
if (last_drop != 0 &&
startups < options.max_startups_begin - 1) {
/* XXX maybe need better hysteresis here */
logit("exited MaxStartups throttling after %s, "
"%u connections dropped",
fmt_timeframe(now - first_drop), ndropped);
last_drop = 0;
}
return 0;
}
#define SSHD_MAXSTARTUPS_LOG_INTERVAL (5 * 60)
if (last_drop == 0) {
error("beginning MaxStartups throttling");
drop_level = SYSLOG_LEVEL_INFO;
first_drop = now;
ndropped = 0;
} else if (last_drop + SSHD_MAXSTARTUPS_LOG_INTERVAL < now) {
/* Periodic logs */
error("in MaxStartups throttling for %s, "
"%u connections dropped",
fmt_timeframe(now - first_drop), ndropped + 1);
drop_level = SYSLOG_LEVEL_INFO;
}
last_drop = now;
ndropped++;
laddr = get_local_ipaddr(sock);
raddr = get_peer_ipaddr(sock);
do_log2(drop_level, "drop connection #%d from [%s]:%d on [%s]:%d "
"past MaxStartups", startups, raddr, get_peer_port(sock),
laddr, get_local_port(sock));
free(laddr);
free(raddr);
/* best-effort notification to client */
(void)write(sock, msg, sizeof(msg) - 1);
return 1;
}
static void
usage(void)
{
fprintf(stderr, "%s, %s\n", SSH_RELEASE, SSH_OPENSSL_VERSION);
fprintf(stderr,
"usage: sshd [-46DdeGiqTtV] [-C connection_spec] [-c host_cert_file]\n"
" [-E log_file] [-f config_file] [-g login_grace_time]\n"
" [-h host_key_file] [-o option] [-p port] [-u len]\n"
);
exit(1);
}
static struct sshbuf *
pack_hostkeys(void)
{
struct sshbuf *keybuf = NULL, *hostkeys = NULL;
int r;
u_int i;
if ((keybuf = sshbuf_new()) == NULL ||
(hostkeys = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
/* pack hostkeys into a string. Empty key slots get empty strings */
for (i = 0; i < options.num_host_key_files; i++) {
/* private key */
sshbuf_reset(keybuf);
if (sensitive_data.host_keys[i] != NULL &&
(r = sshkey_private_serialize(sensitive_data.host_keys[i],
keybuf)) != 0)
fatal_fr(r, "serialize hostkey private");
if ((r = sshbuf_put_stringb(hostkeys, keybuf)) != 0)
fatal_fr(r, "compose hostkey private");
/* public key */
if (sensitive_data.host_pubkeys[i] != NULL) {
if ((r = sshkey_puts(sensitive_data.host_pubkeys[i],
hostkeys)) != 0)
fatal_fr(r, "compose hostkey public");
} else {
if ((r = sshbuf_put_string(hostkeys, NULL, 0)) != 0)
fatal_fr(r, "compose hostkey empty public");
}
/* cert */
if (sensitive_data.host_certificates[i] != NULL) {
if ((r = sshkey_puts(
sensitive_data.host_certificates[i],
hostkeys)) != 0)
fatal_fr(r, "compose host cert");
} else {
if ((r = sshbuf_put_string(hostkeys, NULL, 0)) != 0)
fatal_fr(r, "compose host cert empty");
}
}
sshbuf_free(keybuf);
return hostkeys;
}
static void
send_rexec_state(int fd, struct sshbuf *conf)
{
struct sshbuf *m = NULL, *inc = NULL, *hostkeys = NULL;
struct include_item *item = NULL;
int r, sz;
debug3_f("entering fd = %d config len %zu", fd,
sshbuf_len(conf));
if ((m = sshbuf_new()) == NULL ||
(inc = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
/* pack includes into a string */
TAILQ_FOREACH(item, &includes, entry) {
if ((r = sshbuf_put_cstring(inc, item->selector)) != 0 ||
(r = sshbuf_put_cstring(inc, item->filename)) != 0 ||
(r = sshbuf_put_stringb(inc, item->contents)) != 0)
fatal_fr(r, "compose includes");
}
hostkeys = pack_hostkeys();
/*
* Protocol from reexec master to child:
* string configuration
* uint64 timing_secret
* string host_keys[] {
* string private_key
* string public_key
* string certificate
* }
* string included_files[] {
* string selector
* string filename
* string contents
* }
*/
if ((r = sshbuf_put_stringb(m, conf)) != 0 ||
(r = sshbuf_put_u64(m, options.timing_secret)) != 0 ||
(r = sshbuf_put_stringb(m, hostkeys)) != 0 ||
(r = sshbuf_put_stringb(m, inc)) != 0)
fatal_fr(r, "compose config");
/* We need to fit the entire message inside the socket send buffer */
sz = ROUNDUP(sshbuf_len(m) + 5, 16*1024);
if (setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &sz, sizeof sz) == -1)
fatal_f("setsockopt SO_SNDBUF: %s", strerror(errno));
if (ssh_msg_send(fd, 0, m) == -1)
error_f("ssh_msg_send failed");
sshbuf_free(m);
sshbuf_free(inc);
sshbuf_free(hostkeys);
debug3_f("done");
}
/*
* Listen for TCP connections
*/
static void
listen_on_addrs(struct listenaddr *la)
{
int ret, listen_sock;
struct addrinfo *ai;
char ntop[NI_MAXHOST], strport[NI_MAXSERV];
for (ai = la->addrs; ai; ai = ai->ai_next) {
if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
continue;
if (num_listen_socks >= MAX_LISTEN_SOCKS)
fatal("Too many listen sockets. "
"Enlarge MAX_LISTEN_SOCKS");
if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen,
ntop, sizeof(ntop), strport, sizeof(strport),
NI_NUMERICHOST|NI_NUMERICSERV)) != 0) {
error("getnameinfo failed: %.100s",
ssh_gai_strerror(ret));
continue;
}
/* Create socket for listening. */
listen_sock = socket(ai->ai_family, ai->ai_socktype,
ai->ai_protocol);
if (listen_sock == -1) {
/* kernel may not support ipv6 */
verbose("socket: %.100s", strerror(errno));
continue;
}
if (set_nonblock(listen_sock) == -1) {
close(listen_sock);
continue;
}
if (fcntl(listen_sock, F_SETFD, FD_CLOEXEC) == -1) {
verbose("socket: CLOEXEC: %s", strerror(errno));
close(listen_sock);
continue;
}
/* Socket options */
set_reuseaddr(listen_sock);
if (la->rdomain != NULL &&
set_rdomain(listen_sock, la->rdomain) == -1) {
close(listen_sock);
continue;
}
/* Only communicate in IPv6 over AF_INET6 sockets. */
if (ai->ai_family == AF_INET6)
sock_set_v6only(listen_sock);
debug("Bind to port %s on %s.", strport, ntop);
/* Bind the socket to the desired port. */
if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) == -1) {
error("Bind to port %s on %s failed: %.200s.",
strport, ntop, strerror(errno));
close(listen_sock);
continue;
}
listen_socks[num_listen_socks] = listen_sock;
num_listen_socks++;
/* Start listening on the port. */
if (listen(listen_sock, SSH_LISTEN_BACKLOG) == -1)
fatal("listen on [%s]:%s: %.100s",
ntop, strport, strerror(errno));
logit("Server listening on %s port %s%s%s.",
ntop, strport,
la->rdomain == NULL ? "" : " rdomain ",
la->rdomain == NULL ? "" : la->rdomain);
}
}
static void
server_listen(void)
{
u_int i;
/* Initialise per-source limit tracking. */
srclimit_init(options.max_startups, options.per_source_max_startups,
options.per_source_masklen_ipv4, options.per_source_masklen_ipv6);
for (i = 0; i < options.num_listen_addrs; i++) {
listen_on_addrs(&options.listen_addrs[i]);
freeaddrinfo(options.listen_addrs[i].addrs);
free(options.listen_addrs[i].rdomain);
memset(&options.listen_addrs[i], 0,
sizeof(options.listen_addrs[i]));
}
free(options.listen_addrs);
options.listen_addrs = NULL;
options.num_listen_addrs = 0;
if (!num_listen_socks)
fatal("Cannot bind any address.");
}
/*
* The main TCP accept loop. Note that, for the non-debug case, returns
* from this function are in a forked subprocess.
*/
static void
server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s,
int log_stderr)
{
struct pollfd *pfd = NULL;
int i, j, ret, npfd;
int ostartups = -1, startups = 0, listening = 0, lameduck = 0;
int startup_p[2] = { -1 , -1 }, *startup_pollfd;
char c = 0;
struct sockaddr_storage from;
socklen_t fromlen;
pid_t pid;
u_char rnd[256];
sigset_t nsigset, osigset;
/* pipes connected to unauthenticated child sshd processes */
startup_pipes = xcalloc(options.max_startups, sizeof(int));
startup_flags = xcalloc(options.max_startups, sizeof(int));
startup_pollfd = xcalloc(options.max_startups, sizeof(int));
for (i = 0; i < options.max_startups; i++)
startup_pipes[i] = -1;
/*
* Prepare signal mask that we use to block signals that might set
* received_sigterm or received_sighup, so that we are guaranteed
* to immediately wake up the ppoll if a signal is received after
* the flag is checked.
*/
sigemptyset(&nsigset);
sigaddset(&nsigset, SIGHUP);
sigaddset(&nsigset, SIGCHLD);
sigaddset(&nsigset, SIGTERM);
sigaddset(&nsigset, SIGQUIT);
/* sized for worst-case */
pfd = xcalloc(num_listen_socks + options.max_startups,
sizeof(struct pollfd));
/*
* Stay listening for connections until the system crashes or
* the daemon is killed with a signal.
*/
for (;;) {
sigprocmask(SIG_BLOCK, &nsigset, &osigset);
if (received_sigterm) {
logit("Received signal %d; terminating.",
(int) received_sigterm);
close_listen_socks();
if (options.pid_file != NULL)
unlink(options.pid_file);
exit(received_sigterm == SIGTERM ? 0 : 255);
}
if (ostartups != startups) {
setproctitle("%s [listener] %d of %d-%d startups",
listener_proctitle, startups,
options.max_startups_begin, options.max_startups);
ostartups = startups;
}
if (received_sighup) {
if (!lameduck) {
debug("Received SIGHUP; waiting for children");
close_listen_socks();
lameduck = 1;
}
if (listening <= 0) {
sigprocmask(SIG_SETMASK, &osigset, NULL);
sighup_restart();
}
}
for (i = 0; i < num_listen_socks; i++) {
pfd[i].fd = listen_socks[i];
pfd[i].events = POLLIN;
}
npfd = num_listen_socks;
for (i = 0; i < options.max_startups; i++) {
startup_pollfd[i] = -1;
if (startup_pipes[i] != -1) {
pfd[npfd].fd = startup_pipes[i];
pfd[npfd].events = POLLIN;
startup_pollfd[i] = npfd++;
}
}
/* Wait until a connection arrives or a child exits. */
ret = ppoll(pfd, npfd, NULL, &osigset);
if (ret == -1 && errno != EINTR) {
error("ppoll: %.100s", strerror(errno));
if (errno == EINVAL)
cleanup_exit(1); /* can't recover */
}
sigprocmask(SIG_SETMASK, &osigset, NULL);
if (ret == -1)
continue;
for (i = 0; i < options.max_startups; i++) {
if (startup_pipes[i] == -1 ||
startup_pollfd[i] == -1 ||
!(pfd[startup_pollfd[i]].revents & (POLLIN|POLLHUP)))
continue;
switch (read(startup_pipes[i], &c, sizeof(c))) {
case -1:
if (errno == EINTR || errno == EAGAIN)
continue;
if (errno != EPIPE) {
error_f("startup pipe %d (fd=%d): "
"read %s", i, startup_pipes[i],
strerror(errno));
}
/* FALLTHROUGH */
case 0:
/* child exited or completed auth */
close(startup_pipes[i]);
srclimit_done(startup_pipes[i]);
startup_pipes[i] = -1;
startups--;
if (startup_flags[i])
listening--;
break;
case 1:
/* child has finished preliminaries */
if (startup_flags[i]) {
listening--;
startup_flags[i] = 0;
}
break;
}
}
for (i = 0; i < num_listen_socks; i++) {
if (!(pfd[i].revents & POLLIN))
continue;
fromlen = sizeof(from);
*newsock = accept(listen_socks[i],
(struct sockaddr *)&from, &fromlen);
if (*newsock == -1) {
if (errno != EINTR && errno != EWOULDBLOCK &&
errno != ECONNABORTED && errno != EAGAIN)
error("accept: %.100s",
strerror(errno));
if (errno == EMFILE || errno == ENFILE)
usleep(100 * 1000);
continue;
}
if (unset_nonblock(*newsock) == -1) {
close(*newsock);
continue;
}
if (pipe(startup_p) == -1) {
error_f("pipe(startup_p): %s", strerror(errno));
close(*newsock);
continue;
}
if (drop_connection(*newsock, startups, startup_p[0])) {
close(*newsock);
close(startup_p[0]);
close(startup_p[1]);
continue;
}
if (socketpair(AF_UNIX,
SOCK_STREAM, 0, config_s) == -1) {
error("reexec socketpair: %s",
strerror(errno));
close(*newsock);
close(startup_p[0]);
close(startup_p[1]);
continue;
}
for (j = 0; j < options.max_startups; j++)
if (startup_pipes[j] == -1) {
startup_pipes[j] = startup_p[0];
startups++;
startup_flags[j] = 1;
break;
}
/*
* Got connection. Fork a child to handle it, unless
* we are in debugging mode.
*/
if (debug_flag) {
/*
* In debugging mode. Close the listening
* socket, and start processing the
* connection without forking.
*/
debug("Server will not fork when running in debugging mode.");
close_listen_socks();
*sock_in = *newsock;
*sock_out = *newsock;
close(startup_p[0]);
close(startup_p[1]);
startup_pipe = -1;
pid = getpid();
send_rexec_state(config_s[0], cfg);
close(config_s[0]);
free(pfd);
return;
}
/*
* Normal production daemon. Fork, and have
* the child process the connection. The
* parent continues listening.
*/
platform_pre_fork();
listening++;
if ((pid = fork()) == 0) {
/*
* Child. Close the listening and
* max_startup sockets. Start using
* the accepted socket. Reinitialize
* logging (since our pid has changed).
* We return from this function to handle
* the connection.
*/
platform_post_fork_child();
startup_pipe = startup_p[1];
close_startup_pipes();
close_listen_socks();
*sock_in = *newsock;
*sock_out = *newsock;
log_init(__progname,
options.log_level,
options.log_facility,
log_stderr);
close(config_s[0]);
free(pfd);
return;
}
/* Parent. Stay in the loop. */
platform_post_fork_parent(pid);
if (pid == -1)
error("fork: %.100s", strerror(errno));
else
debug("Forked child %ld.", (long)pid);
close(startup_p[1]);
close(config_s[1]);
send_rexec_state(config_s[0], cfg);
close(config_s[0]);
close(*newsock);
/*
* Ensure that our random state differs
* from that of the child
*/
arc4random_stir();
arc4random_buf(rnd, sizeof(rnd));
#ifdef WITH_OPENSSL
RAND_seed(rnd, sizeof(rnd));
if ((RAND_bytes((u_char *)rnd, 1)) != 1)
fatal("%s: RAND_bytes failed", __func__);
#endif
explicit_bzero(rnd, sizeof(rnd));
}
}
}
static void
accumulate_host_timing_secret(struct sshbuf *server_cfg,
struct sshkey *key)
{
static struct ssh_digest_ctx *ctx;
u_char *hash;
size_t len;
struct sshbuf *buf;
int r;
if (ctx == NULL && (ctx = ssh_digest_start(SSH_DIGEST_SHA512)) == NULL)
fatal_f("ssh_digest_start");
if (key == NULL) { /* finalize */
/* add server config in case we are using agent for host keys */
if (ssh_digest_update(ctx, sshbuf_ptr(server_cfg),
sshbuf_len(server_cfg)) != 0)
fatal_f("ssh_digest_update");
len = ssh_digest_bytes(SSH_DIGEST_SHA512);
hash = xmalloc(len);
if (ssh_digest_final(ctx, hash, len) != 0)
fatal_f("ssh_digest_final");
options.timing_secret = PEEK_U64(hash);
freezero(hash, len);
ssh_digest_free(ctx);
ctx = NULL;
return;
}
if ((buf = sshbuf_new()) == NULL)
fatal_f("could not allocate buffer");
if ((r = sshkey_private_serialize(key, buf)) != 0)
fatal_fr(r, "encode %s key", sshkey_ssh_name(key));
if (ssh_digest_update(ctx, sshbuf_ptr(buf), sshbuf_len(buf)) != 0)
fatal_f("ssh_digest_update");
sshbuf_reset(buf);
sshbuf_free(buf);
}
static char *
prepare_proctitle(int ac, char **av)
{
char *ret = NULL;
int i;
for (i = 0; i < ac; i++)
xextendf(&ret, " ", "%s", av[i]);
return ret;
}
static void
print_config(struct connection_info *connection_info)
{
connection_info->test = 1;
parse_server_match_config(&options, &includes, connection_info);
dump_config(&options);
exit(0);
}
/*
* Main program for the daemon.
*/
int
main(int ac, char **av)
{
extern char *optarg;
extern int optind;
int log_stderr = 0, inetd_flag = 0, test_flag = 0, no_daemon_flag = 0;
char *config_file_name = _PATH_SERVER_CONFIG_FILE;
int r, opt, do_dump_cfg = 0, keytype, already_daemon, have_agent = 0;
int sock_in = -1, sock_out = -1, newsock = -1, rexec_argc = 0;
int devnull, config_s[2] = { -1 , -1 }, have_connection_info = 0;
int need_chroot = 1;
char *fp, *line, *logfile = NULL, **rexec_argv = NULL;
struct stat sb;
u_int i, j;
mode_t new_umask;
struct sshkey *key;
struct sshkey *pubkey;
struct connection_info connection_info;
sigset_t sigmask;
memset(&connection_info, 0, sizeof(connection_info));
#ifdef HAVE_SECUREWARE
(void)set_auth_parameters(ac, av);
#endif
__progname = ssh_get_progname(av[0]);
sigemptyset(&sigmask);
sigprocmask(SIG_SETMASK, &sigmask, NULL);
/* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
saved_argc = ac;
rexec_argc = ac;
saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
for (i = 0; (int)i < ac; i++)
saved_argv[i] = xstrdup(av[i]);
saved_argv[i] = NULL;
#ifndef HAVE_SETPROCTITLE
/* Prepare for later setproctitle emulation */
compat_init_setproctitle(ac, av);
av = saved_argv;
#endif
if (geteuid() == 0 && setgroups(0, NULL) == -1)
debug("setgroups(): %.200s", strerror(errno));
/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
sanitise_stdfd();
/* Initialize configuration options to their default values. */
initialize_server_options(&options);
/* Parse command-line arguments. */
while ((opt = getopt(ac, av,
"C:E:b:c:f:g:h:k:o:p:u:46DGQRTdeiqrtV")) != -1) {
switch (opt) {
case '4':
options.address_family = AF_INET;
break;
case '6':
options.address_family = AF_INET6;
break;
case 'f':
config_file_name = optarg;
break;
case 'c':
servconf_add_hostcert("[command-line]", 0,
&options, optarg);
break;
case 'd':
if (debug_flag == 0) {
debug_flag = 1;
options.log_level = SYSLOG_LEVEL_DEBUG1;
} else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
options.log_level++;
break;
case 'D':
no_daemon_flag = 1;
break;
case 'G':
do_dump_cfg = 1;
break;
case 'E':
logfile = optarg;
/* FALLTHROUGH */
case 'e':
log_stderr = 1;
break;
case 'i':
inetd_flag = 1;
break;
case 'r':
logit("-r option is deprecated");
break;
case 'R':
fatal("-R not supported here");
break;
case 'Q':
/* ignored */
break;
case 'q':
options.log_level = SYSLOG_LEVEL_QUIET;
break;
case 'b':
/* protocol 1, ignored */
break;
case 'p':
options.ports_from_cmdline = 1;
if (options.num_ports >= MAX_PORTS) {
fprintf(stderr, "too many ports.\n");
exit(1);
}
options.ports[options.num_ports++] = a2port(optarg);
if (options.ports[options.num_ports-1] <= 0) {
fprintf(stderr, "Bad port number.\n");
exit(1);
}
break;
case 'g':
if ((options.login_grace_time = convtime(optarg)) == -1) {
fprintf(stderr, "Invalid login grace time.\n");
exit(1);
}
break;
case 'k':
/* protocol 1, ignored */
break;
case 'h':
servconf_add_hostkey("[command-line]", 0,
&options, optarg, 1);
break;
case 't':
test_flag = 1;
break;
case 'T':
test_flag = 2;
break;
case 'C':
if (parse_server_match_testspec(&connection_info,
optarg) == -1)
exit(1);
have_connection_info = 1;
break;
case 'u':
utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL);
if (utmp_len > HOST_NAME_MAX+1) {
fprintf(stderr, "Invalid utmp length.\n");
exit(1);
}
break;
case 'o':
line = xstrdup(optarg);
if (process_server_config_line(&options, line,
"command-line", 0, NULL, NULL, &includes) != 0)
exit(1);
free(line);
break;
case 'V':
fprintf(stderr, "%s, %s\n",
SSH_RELEASE, SSH_OPENSSL_VERSION);
exit(0);
default:
usage();
break;
}
}
if (!test_flag && !do_dump_cfg && !path_absolute(av[0]))
fatal("sshd requires execution with an absolute path");
closefrom(STDERR_FILENO + 1);
/* Reserve fds we'll need later for reexec things */
if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1)
fatal("open %s: %s", _PATH_DEVNULL, strerror(errno));
while (devnull < REEXEC_MIN_FREE_FD) {
if ((devnull = dup(devnull)) == -1)
fatal("dup %s: %s", _PATH_DEVNULL, strerror(errno));
}
seed_rng();
/* If requested, redirect the logs to the specified logfile. */
if (logfile != NULL) {
char *cp, pid_s[32];
snprintf(pid_s, sizeof(pid_s), "%ld", (unsigned long)getpid());
cp = percent_expand(logfile,
"p", pid_s,
"P", "sshd",
(char *)NULL);
log_redirect_stderr_to(cp);
free(cp);
}
/*
* Force logging to stderr until we have loaded the private host
* key (unless started from inetd)
*/
log_init(__progname,
options.log_level == SYSLOG_LEVEL_NOT_SET ?
SYSLOG_LEVEL_INFO : options.log_level,
options.log_facility == SYSLOG_FACILITY_NOT_SET ?
SYSLOG_FACILITY_AUTH : options.log_facility,
log_stderr || !inetd_flag || debug_flag);
/*
* Unset KRB5CCNAME, otherwise the user's session may inherit it from
* root's environment
*/
if (getenv("KRB5CCNAME") != NULL)
(void) unsetenv("KRB5CCNAME");
sensitive_data.have_ssh2_key = 0;
/*
* If we're not doing an extended test do not silently ignore connection
* test params.
*/
if (test_flag < 2 && have_connection_info)
fatal("Config test connection parameter (-C) provided without "
"test mode (-T)");
/* Fetch our configuration */
if ((cfg = sshbuf_new()) == NULL)
fatal("sshbuf_new config failed");
if (strcasecmp(config_file_name, "none") != 0)
load_server_config(config_file_name, cfg);
parse_server_config(&options, config_file_name, cfg,
&includes, NULL, 0);
/* Fill in default values for those options not explicitly set. */
fill_default_server_options(&options);
/* Check that options are sensible */
if (options.authorized_keys_command_user == NULL &&
(options.authorized_keys_command != NULL &&
strcasecmp(options.authorized_keys_command, "none") != 0))
fatal("AuthorizedKeysCommand set without "
"AuthorizedKeysCommandUser");
if (options.authorized_principals_command_user == NULL &&
(options.authorized_principals_command != NULL &&
strcasecmp(options.authorized_principals_command, "none") != 0))
fatal("AuthorizedPrincipalsCommand set without "
"AuthorizedPrincipalsCommandUser");
/*
* Check whether there is any path through configured auth methods.
* Unfortunately it is not possible to verify this generally before
* daemonisation in the presence of Match blocks, but this catches
* and warns for trivial misconfigurations that could break login.
*/
if (options.num_auth_methods != 0) {
for (i = 0; i < options.num_auth_methods; i++) {
if (auth2_methods_valid(options.auth_methods[i],
1) == 0)
break;
}
if (i >= options.num_auth_methods)
fatal("AuthenticationMethods cannot be satisfied by "
"enabled authentication methods");
}
/* Check that there are no remaining arguments. */
if (optind < ac) {
fprintf(stderr, "Extra argument %s.\n", av[optind]);
exit(1);
}
debug("sshd version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION);
if (do_dump_cfg)
print_config(&connection_info);
/* load host keys */
sensitive_data.host_keys = xcalloc(options.num_host_key_files,
sizeof(struct sshkey *));
sensitive_data.host_pubkeys = xcalloc(options.num_host_key_files,
sizeof(struct sshkey *));
if (options.host_key_agent) {
if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME))
setenv(SSH_AUTHSOCKET_ENV_NAME,
options.host_key_agent, 1);
if ((r = ssh_get_authentication_socket(NULL)) == 0)
have_agent = 1;
else
error_r(r, "Could not connect to agent \"%s\"",
options.host_key_agent);
}
for (i = 0; i < options.num_host_key_files; i++) {
int ll = options.host_key_file_userprovided[i] ?
SYSLOG_LEVEL_ERROR : SYSLOG_LEVEL_DEBUG1;
if (options.host_key_files[i] == NULL)
continue;
if ((r = sshkey_load_private(options.host_key_files[i], "",
&key, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR)
do_log2_r(r, ll, "Unable to load host key \"%s\"",
options.host_key_files[i]);
if (sshkey_is_sk(key) &&
key->sk_flags & SSH_SK_USER_PRESENCE_REQD) {
debug("host key %s requires user presence, ignoring",
options.host_key_files[i]);
key->sk_flags &= ~SSH_SK_USER_PRESENCE_REQD;
}
if (r == 0 && key != NULL &&
(r = sshkey_shield_private(key)) != 0) {
do_log2_r(r, ll, "Unable to shield host key \"%s\"",
options.host_key_files[i]);
sshkey_free(key);
key = NULL;
}
if ((r = sshkey_load_public(options.host_key_files[i],
&pubkey, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR)
do_log2_r(r, ll, "Unable to load host key \"%s\"",
options.host_key_files[i]);
if (pubkey != NULL && key != NULL) {
if (!sshkey_equal(pubkey, key)) {
error("Public key for %s does not match "
"private key", options.host_key_files[i]);
sshkey_free(pubkey);
pubkey = NULL;
}
}
if (pubkey == NULL && key != NULL) {
if ((r = sshkey_from_private(key, &pubkey)) != 0)
fatal_r(r, "Could not demote key: \"%s\"",
options.host_key_files[i]);
}
if (pubkey != NULL && (r = sshkey_check_rsa_length(pubkey,
options.required_rsa_size)) != 0) {
error_fr(r, "Host key %s", options.host_key_files[i]);
sshkey_free(pubkey);
sshkey_free(key);
continue;
}
sensitive_data.host_keys[i] = key;
sensitive_data.host_pubkeys[i] = pubkey;
if (key == NULL && pubkey != NULL && have_agent) {
debug("will rely on agent for hostkey %s",
options.host_key_files[i]);
keytype = pubkey->type;
} else if (key != NULL) {
keytype = key->type;
accumulate_host_timing_secret(cfg, key);
} else {
do_log2(ll, "Unable to load host key: %s",
options.host_key_files[i]);
sensitive_data.host_keys[i] = NULL;
sensitive_data.host_pubkeys[i] = NULL;
continue;
}
switch (keytype) {
case KEY_RSA:
case KEY_DSA:
case KEY_ECDSA:
case KEY_ED25519:
case KEY_ECDSA_SK:
case KEY_ED25519_SK:
case KEY_XMSS:
if (have_agent || key != NULL)
sensitive_data.have_ssh2_key = 1;
break;
}
if ((fp = sshkey_fingerprint(pubkey, options.fingerprint_hash,
SSH_FP_DEFAULT)) == NULL)
fatal("sshkey_fingerprint failed");
debug("%s host key #%d: %s %s",
key ? "private" : "agent", i, sshkey_ssh_name(pubkey), fp);
free(fp);
}
accumulate_host_timing_secret(cfg, NULL);
if (!sensitive_data.have_ssh2_key) {
logit("sshd: no hostkeys available -- exiting.");
exit(1);
}
/*
* Load certificates. They are stored in an array at identical
* indices to the public keys that they relate to.
*/
sensitive_data.host_certificates = xcalloc(options.num_host_key_files,
sizeof(struct sshkey *));
for (i = 0; i < options.num_host_key_files; i++)
sensitive_data.host_certificates[i] = NULL;
for (i = 0; i < options.num_host_cert_files; i++) {
if (options.host_cert_files[i] == NULL)
continue;
if ((r = sshkey_load_public(options.host_cert_files[i],
&key, NULL)) != 0) {
error_r(r, "Could not load host certificate \"%s\"",
options.host_cert_files[i]);
continue;
}
if (!sshkey_is_cert(key)) {
error("Certificate file is not a certificate: %s",
options.host_cert_files[i]);
sshkey_free(key);
continue;
}
/* Find matching private key */
for (j = 0; j < options.num_host_key_files; j++) {
if (sshkey_equal_public(key,
sensitive_data.host_pubkeys[j])) {
sensitive_data.host_certificates[j] = key;
break;
}
}
if (j >= options.num_host_key_files) {
error("No matching private key for certificate: %s",
options.host_cert_files[i]);
sshkey_free(key);
continue;
}
sensitive_data.host_certificates[j] = key;
debug("host certificate: #%u type %d %s", j, key->type,
sshkey_type(key));
}
/* Ensure privsep directory is correctly configured. */
need_chroot = ((getuid() == 0 || geteuid() == 0) ||
options.kerberos_authentication);
if ((getpwnam(SSH_PRIVSEP_USER)) == NULL && need_chroot) {
fatal("Privilege separation user %s does not exist",
SSH_PRIVSEP_USER);
}
endpwent();
if (need_chroot) {
if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &sb) == -1) ||
(S_ISDIR(sb.st_mode) == 0))
fatal("Missing privilege separation directory: %s",
_PATH_PRIVSEP_CHROOT_DIR);
#ifdef HAVE_CYGWIN
if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
(sb.st_uid != getuid () ||
(sb.st_mode & (S_IWGRP|S_IWOTH)) != 0))
#else
if (sb.st_uid != 0 || (sb.st_mode & (S_IWGRP|S_IWOTH)) != 0)
#endif
fatal("%s must be owned by root and not group or "
"world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
}
if (test_flag > 1)
print_config(&connection_info);
/* Configuration looks good, so exit if in test mode. */
if (test_flag)
exit(0);
/*
* Clear out any supplemental groups we may have inherited. This
* prevents inadvertent creation of files with bad modes (in the
* portable version at least, it's certainly possible for PAM
* to create a file, and we can't control the code in every
* module which might be used).
*/
if (setgroups(0, NULL) < 0)
debug("setgroups() failed: %.200s", strerror(errno));
/* Prepare arguments for sshd-session */
if (rexec_argc < 0)
fatal("rexec_argc %d < 0", rexec_argc);
rexec_argv = xcalloc(rexec_argc + 3, sizeof(char *));
/* Point to the sshd-session binary instead of sshd */
rexec_argv[0] = options.sshd_session_path;
for (i = 1; i < (u_int)rexec_argc; i++) {
debug("rexec_argv[%d]='%s'", i, saved_argv[i]);
rexec_argv[i] = saved_argv[i];
}
rexec_argv[rexec_argc++] = "-R";
rexec_argv[rexec_argc] = NULL;
if (stat(rexec_argv[0], &sb) != 0 || !(sb.st_mode & (S_IXOTH|S_IXUSR)))
fatal("%s does not exist or is not executable", rexec_argv[0]);
debug3("using %s for re-exec", rexec_argv[0]);
listener_proctitle = prepare_proctitle(ac, av);
/* Ensure that umask disallows at least group and world write */
new_umask = umask(0077) | 0022;
(void) umask(new_umask);
/* Initialize the log (it is reinitialized below in case we forked). */
if (debug_flag && !inetd_flag)
log_stderr = 1;
log_init(__progname, options.log_level,
options.log_facility, log_stderr);
for (i = 0; i < options.num_log_verbose; i++)
log_verbose_add(options.log_verbose[i]);
/*
* If not in debugging mode, not started from inetd and not already
* daemonized (eg re-exec via SIGHUP), disconnect from the controlling
* terminal, and fork. The original process exits.
*/
already_daemon = daemonized();
if (!(debug_flag || inetd_flag || no_daemon_flag || already_daemon)) {
if (daemon(0, 0) == -1)
fatal("daemon() failed: %.200s", strerror(errno));
disconnect_controlling_tty();
}
/* Reinitialize the log (because of the fork above). */
log_init(__progname, options.log_level, options.log_facility, log_stderr);
/*
* Chdir to the root directory so that the current disk can be
* unmounted if desired.
*/
if (chdir("/") == -1)
error("chdir(\"/\"): %s", strerror(errno));
/* ignore SIGPIPE */
ssh_signal(SIGPIPE, SIG_IGN);
/* Get a connection, either from inetd or a listening TCP socket */
if (inetd_flag) {
/* Send configuration to ancestor sshd-session process */
if (socketpair(AF_UNIX, SOCK_STREAM, 0, config_s) == -1)
fatal("socketpair: %s", strerror(errno));
send_rexec_state(config_s[0], cfg);
close(config_s[0]);
} else {
platform_pre_listen();
server_listen();
ssh_signal(SIGHUP, sighup_handler);
ssh_signal(SIGCHLD, main_sigchld_handler);
ssh_signal(SIGTERM, sigterm_handler);
ssh_signal(SIGQUIT, sigterm_handler);
platform_post_listen();
/*
* Write out the pid file after the sigterm handler
* is setup and the listen sockets are bound
*/
if (options.pid_file != NULL && !debug_flag) {
FILE *f = fopen(options.pid_file, "w");
if (f == NULL) {
error("Couldn't create pid file \"%s\": %s",
options.pid_file, strerror(errno));
} else {
fprintf(f, "%ld\n", (long) getpid());
fclose(f);
}
}
/* Accept a connection and return in a forked child */
server_accept_loop(&sock_in, &sock_out,
&newsock, config_s, log_stderr);
}
/* This is the child processing a new connection. */
setproctitle("%s", "[accepted]");
/*
* Create a new session and process group since the 4.4BSD
* setlogin() affects the entire process group. We don't
* want the child to be able to affect the parent.
*/
if (!debug_flag && !inetd_flag && setsid() == -1)
error("setsid: %.100s", strerror(errno));
debug("rexec start in %d out %d newsock %d pipe %d sock %d/%d",
sock_in, sock_out, newsock, startup_pipe, config_s[0], config_s[1]);
if (!inetd_flag) {
if (dup2(newsock, STDIN_FILENO) == -1)
fatal("dup2 stdin: %s", strerror(errno));
if (dup2(STDIN_FILENO, STDOUT_FILENO) == -1)
fatal("dup2 stdout: %s", strerror(errno));
if (newsock > STDOUT_FILENO)
close(newsock);
}
if (config_s[1] != REEXEC_CONFIG_PASS_FD) {
if (dup2(config_s[1], REEXEC_CONFIG_PASS_FD) == -1)
fatal("dup2 config_s: %s", strerror(errno));
close(config_s[1]);
}
if (startup_pipe == -1)
close(REEXEC_STARTUP_PIPE_FD);
else if (startup_pipe != REEXEC_STARTUP_PIPE_FD) {
if (dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD) == -1)
fatal("dup2 startup_p: %s", strerror(errno));
close(startup_pipe);
}
closefrom(REEXEC_MIN_FREE_FD);
ssh_signal(SIGHUP, SIG_IGN); /* avoid reset to SIG_DFL */
execv(rexec_argv[0], rexec_argv);
fatal("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
}
/* server specific fatal cleanup */
void
cleanup_exit(int i)
{
_exit(i);
}
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