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openssh/sshd.c
djm@openbsd.org 70d38c3cfd upstream: expose the number of currently-authenticating connections 
along with the MaxStartups limit in the proctitle; suggestion from Philipp
Marek, w/ feedback from Craig Miskell ok dtucker@

OpenBSD-Commit-ID: a4a6db2dc1641a5df8eddf7d6652176e359dffb3
2020-01-22 09:41:47 +11:00

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/* $OpenBSD: sshd.c,v 1.543 2020/01/21 22:39:57 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
* This program is the ssh daemon. It listens for connections from clients,
* and performs authentication, executes use commands or shell, and forwards
* information to/from the application to the user client over an encrypted
* connection. This can also handle forwarding of X11, TCP/IP, and
* authentication agent connections.
*
* As far as I am concerned, the code I have written for this software
* can be used freely for any purpose. Any derived versions of this
* software must be clearly marked as such, and if the derived work is
* incompatible with the protocol description in the RFC file, it must be
* called by a name other than "ssh" or "Secure Shell".
*
* SSH2 implementation:
* Privilege Separation:
*
* 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>
#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/dh.h>
#include <openssl/bn.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 "ssh2.h"
#include "sshpty.h"
#include "packet.h"
#include "log.h"
#include "sshbuf.h"
#include "misc.h"
#include "match.h"
#include "servconf.h"
#include "uidswap.h"
#include "compat.h"
#include "cipher.h"
#include "digest.h"
#include "sshkey.h"
#include "kex.h"
#include "myproposal.h"
#include "authfile.h"
#include "pathnames.h"
#include "atomicio.h"
#include "canohost.h"
#include "hostfile.h"
#include "auth.h"
#include "authfd.h"
#include "msg.h"
#include "dispatch.h"
#include "channels.h"
#include "session.h"
#include "monitor.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
#include "ssh-sandbox.h"
#include "auth-options.h"
#include "version.h"
#include "ssherr.h"
#include "sk-api.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;
/* Name of the server configuration file. */
char *config_file_name = _PATH_SERVER_CONFIG_FILE;
/*
* 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;
/*
* Indicating that the daemon should only test the configuration and keys.
* If test_flag > 1 ("-T" flag), then sshd will also dump the effective
* configuration, optionally using connection information provided by the
* "-C" flag.
*/
static int test_flag = 0;
/* Flag indicating that the daemon is being started from inetd. */
static int inetd_flag = 0;
/* Flag indicating that sshd should not detach and become a daemon. */
static int no_daemon_flag = 0;
/* debug goes to stderr unless inetd_flag is set */
static int log_stderr = 0;
/* Saved arguments to main(). */
static char **saved_argv;
static int saved_argc;
/* re-exec */
static int rexeced_flag = 0;
static int rexec_flag = 1;
static int rexec_argc = 0;
static char **rexec_argv;
/*
* 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;
/* Daemon's agent connection */
int auth_sock = -1;
static int have_agent = 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;
/* session identifier, used by RSA-auth */
u_char session_id[16];
/* same for ssh2 */
u_char *session_id2 = NULL;
u_int session_id2_len = 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 */
/* variables used for privilege separation */
int use_privsep = -1;
struct monitor *pmonitor = NULL;
int privsep_is_preauth = 1;
static int privsep_chroot = 1;
/* global connection state and authentication contexts */
Authctxt *the_authctxt = NULL;
struct ssh *the_active_state;
/* global key/cert auth options. XXX move to permanent ssh->authctxt? */
struct sshauthopt *auth_opts = NULL;
/* sshd_config buffer */
struct sshbuf *cfg;
/* message to be displayed after login */
struct sshbuf *loginmsg;
/* Unprivileged user */
struct passwd *privsep_pw = NULL;
/* Prototypes for various functions defined later in this file. */
void destroy_sensitive_data(void);
void demote_sensitive_data(void);
static void do_ssh2_kex(struct ssh *);
/*
* 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 = -1;
}
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).
*/
/*ARGSUSED*/
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();
alarm(0); /* alarm timer persists across exec */
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.
*/
/*ARGSUSED*/
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.
*/
/*ARGSUSED*/
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;
}
/*
* Signal handler for the alarm after the login grace period has expired.
*/
/*ARGSUSED*/
static void
grace_alarm_handler(int sig)
{
if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0)
kill(pmonitor->m_pid, SIGALRM);
/*
* Try to kill any processes that we have spawned, E.g. authorized
* keys command helpers.
*/
if (getpgid(0) == getpid()) {
signal(SIGTERM, SIG_IGN);
kill(0, SIGTERM);
}
/* XXX pre-format ipaddr/port so we don't need to access active_state */
/* Log error and exit. */
sigdie("Timeout before authentication for %s port %d",
ssh_remote_ipaddr(the_active_state),
ssh_remote_port(the_active_state));
}
/* Destroy the host and server keys. They will no longer be needed. */
void
destroy_sensitive_data(void)
{
u_int i;
for (i = 0; i < options.num_host_key_files; i++) {
if (sensitive_data.host_keys[i]) {
sshkey_free(sensitive_data.host_keys[i]);
sensitive_data.host_keys[i] = NULL;
}
if (sensitive_data.host_certificates[i]) {
sshkey_free(sensitive_data.host_certificates[i]);
sensitive_data.host_certificates[i] = NULL;
}
}
}
/* Demote private to public keys for network child */
void
demote_sensitive_data(void)
{
struct sshkey *tmp;
u_int i;
int r;
for (i = 0; i < options.num_host_key_files; i++) {
if (sensitive_data.host_keys[i]) {
if ((r = sshkey_from_private(
sensitive_data.host_keys[i], &tmp)) != 0)
fatal("could not demote host %s key: %s",
sshkey_type(sensitive_data.host_keys[i]),
ssh_err(r));
sshkey_free(sensitive_data.host_keys[i]);
sensitive_data.host_keys[i] = tmp;
}
/* Certs do not need demotion */
}
}
static void
reseed_prngs(void)
{
u_int32_t rnd[256];
#ifdef WITH_OPENSSL
RAND_poll();
#endif
arc4random_stir(); /* noop on recent arc4random() implementations */
arc4random_buf(rnd, sizeof(rnd)); /* let arc4random notice PID change */
#ifdef WITH_OPENSSL
RAND_seed(rnd, sizeof(rnd));
/* give libcrypto a chance to notice the PID change */
if ((RAND_bytes((u_char *)rnd, 1)) != 1)
fatal("%s: RAND_bytes failed", __func__);
#endif
explicit_bzero(rnd, sizeof(rnd));
}
static void
privsep_preauth_child(void)
{
gid_t gidset[1];
/* Enable challenge-response authentication for privilege separation */
privsep_challenge_enable();
#ifdef GSSAPI
/* Cache supported mechanism OIDs for later use */
ssh_gssapi_prepare_supported_oids();
#endif
reseed_prngs();
/* Demote the private keys to public keys. */
demote_sensitive_data();
/* Demote the child */
if (privsep_chroot) {
/* Change our root directory */
if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
strerror(errno));
if (chdir("/") == -1)
fatal("chdir(\"/\"): %s", strerror(errno));
/* Drop our privileges */
debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid,
(u_int)privsep_pw->pw_gid);
gidset[0] = privsep_pw->pw_gid;
if (setgroups(1, gidset) == -1)
fatal("setgroups: %.100s", strerror(errno));
permanently_set_uid(privsep_pw);
}
}
static int
privsep_preauth(struct ssh *ssh)
{
int status, r;
pid_t pid;
struct ssh_sandbox *box = NULL;
/* Set up unprivileged child process to deal with network data */
pmonitor = monitor_init();
/* Store a pointer to the kex for later rekeying */
pmonitor->m_pkex = &ssh->kex;
if (use_privsep == PRIVSEP_ON)
box = ssh_sandbox_init(pmonitor);
pid = fork();
if (pid == -1) {
fatal("fork of unprivileged child failed");
} else if (pid != 0) {
debug2("Network child is on pid %ld", (long)pid);
pmonitor->m_pid = pid;
if (have_agent) {
r = ssh_get_authentication_socket(&auth_sock);
if (r != 0) {
error("Could not get agent socket: %s",
ssh_err(r));
have_agent = 0;
}
}
if (box != NULL)
ssh_sandbox_parent_preauth(box, pid);
monitor_child_preauth(ssh, pmonitor);
/* Wait for the child's exit status */
while (waitpid(pid, &status, 0) == -1) {
if (errno == EINTR)
continue;
pmonitor->m_pid = -1;
fatal("%s: waitpid: %s", __func__, strerror(errno));
}
privsep_is_preauth = 0;
pmonitor->m_pid = -1;
if (WIFEXITED(status)) {
if (WEXITSTATUS(status) != 0)
fatal("%s: preauth child exited with status %d",
__func__, WEXITSTATUS(status));
} else if (WIFSIGNALED(status))
fatal("%s: preauth child terminated by signal %d",
__func__, WTERMSIG(status));
if (box != NULL)
ssh_sandbox_parent_finish(box);
return 1;
} else {
/* child */
close(pmonitor->m_sendfd);
close(pmonitor->m_log_recvfd);
/* Arrange for logging to be sent to the monitor */
set_log_handler(mm_log_handler, pmonitor);
privsep_preauth_child();
setproctitle("%s", "[net]");
if (box != NULL)
ssh_sandbox_child(box);
return 0;
}
}
static void
privsep_postauth(struct ssh *ssh, Authctxt *authctxt)
{
#ifdef DISABLE_FD_PASSING
if (1) {
#else
if (authctxt->pw->pw_uid == 0) {
#endif
/* File descriptor passing is broken or root login */
use_privsep = 0;
goto skip;
}
/* New socket pair */
monitor_reinit(pmonitor);
pmonitor->m_pid = fork();
if (pmonitor->m_pid == -1)
fatal("fork of unprivileged child failed");
else if (pmonitor->m_pid != 0) {
verbose("User child is on pid %ld", (long)pmonitor->m_pid);
sshbuf_reset(loginmsg);
monitor_clear_keystate(ssh, pmonitor);
monitor_child_postauth(ssh, pmonitor);
/* NEVERREACHED */
exit(0);
}
/* child */
close(pmonitor->m_sendfd);
pmonitor->m_sendfd = -1;
/* Demote the private keys to public keys. */
demote_sensitive_data();
reseed_prngs();
/* Drop privileges */
do_setusercontext(authctxt->pw);
skip:
/* It is safe now to apply the key state */
monitor_apply_keystate(ssh, pmonitor);
/*
* Tell the packet layer that authentication was successful, since
* this information is not part of the key state.
*/
ssh_packet_set_authenticated(ssh);
}
static void
append_hostkey_type(struct sshbuf *b, const char *s)
{
int r;
if (match_pattern_list(s, options.hostkeyalgorithms, 0) != 1) {
debug3("%s: %s key not permitted by HostkeyAlgorithms",
__func__, s);
return;
}
if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) > 0 ? "," : "", s)) != 0)
fatal("%s: sshbuf_putf: %s", __func__, ssh_err(r));
}
static char *
list_hostkey_types(void)
{
struct sshbuf *b;
struct sshkey *key;
char *ret;
u_int i;
if ((b = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __func__);
for (i = 0; i < options.num_host_key_files; i++) {
key = sensitive_data.host_keys[i];
if (key == NULL)
key = sensitive_data.host_pubkeys[i];
if (key == NULL)
continue;
switch (key->type) {
case KEY_RSA:
/* for RSA we also support SHA2 signatures */
append_hostkey_type(b, "rsa-sha2-512");
append_hostkey_type(b, "rsa-sha2-256");
/* FALLTHROUGH */
case KEY_DSA:
case KEY_ECDSA:
case KEY_ED25519:
case KEY_ECDSA_SK:
case KEY_ED25519_SK:
case KEY_XMSS:
append_hostkey_type(b, sshkey_ssh_name(key));
break;
}
/* If the private key has a cert peer, then list that too */
key = sensitive_data.host_certificates[i];
if (key == NULL)
continue;
switch (key->type) {
case KEY_RSA_CERT:
/* for RSA we also support SHA2 signatures */
append_hostkey_type(b,
"rsa-sha2-512-cert-v01@openssh.com");
append_hostkey_type(b,
"rsa-sha2-256-cert-v01@openssh.com");
/* FALLTHROUGH */
case KEY_DSA_CERT:
case KEY_ECDSA_CERT:
case KEY_ED25519_CERT:
case KEY_ECDSA_SK_CERT:
case KEY_ED25519_SK_CERT:
case KEY_XMSS_CERT:
append_hostkey_type(b, sshkey_ssh_name(key));
break;
}
}
if ((ret = sshbuf_dup_string(b)) == NULL)
fatal("%s: sshbuf_dup_string failed", __func__);
sshbuf_free(b);
debug("%s: %s", __func__, ret);
return ret;
}
static struct sshkey *
get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh)
{
u_int i;
struct sshkey *key;
for (i = 0; i < options.num_host_key_files; i++) {
switch (type) {
case KEY_RSA_CERT:
case KEY_DSA_CERT:
case KEY_ECDSA_CERT:
case KEY_ED25519_CERT:
case KEY_ECDSA_SK_CERT:
case KEY_ED25519_SK_CERT:
case KEY_XMSS_CERT:
key = sensitive_data.host_certificates[i];
break;
default:
key = sensitive_data.host_keys[i];
if (key == NULL && !need_private)
key = sensitive_data.host_pubkeys[i];
break;
}
if (key == NULL || key->type != type)
continue;
switch (type) {
case KEY_ECDSA:
case KEY_ECDSA_SK:
case KEY_ECDSA_CERT:
case KEY_ECDSA_SK_CERT:
if (key->ecdsa_nid != nid)
continue;
/* FALLTHROUGH */
default:
return need_private ?
sensitive_data.host_keys[i] : key;
}
}
return NULL;
}
struct sshkey *
get_hostkey_public_by_type(int type, int nid, struct ssh *ssh)
{
return get_hostkey_by_type(type, nid, 0, ssh);
}
struct sshkey *
get_hostkey_private_by_type(int type, int nid, struct ssh *ssh)
{
return get_hostkey_by_type(type, nid, 1, ssh);
}
struct sshkey *
get_hostkey_by_index(int ind)
{
if (ind < 0 || (u_int)ind >= options.num_host_key_files)
return (NULL);
return (sensitive_data.host_keys[ind]);
}
struct sshkey *
get_hostkey_public_by_index(int ind, struct ssh *ssh)
{
if (ind < 0 || (u_int)ind >= options.num_host_key_files)
return (NULL);
return (sensitive_data.host_pubkeys[ind]);
}
int
get_hostkey_index(struct sshkey *key, int compare, struct ssh *ssh)
{
u_int i;
for (i = 0; i < options.num_host_key_files; i++) {
if (sshkey_is_cert(key)) {
if (key == sensitive_data.host_certificates[i] ||
(compare && sensitive_data.host_certificates[i] &&
sshkey_equal(key,
sensitive_data.host_certificates[i])))
return (i);
} else {
if (key == sensitive_data.host_keys[i] ||
(compare && sensitive_data.host_keys[i] &&
sshkey_equal(key, sensitive_data.host_keys[i])))
return (i);
if (key == sensitive_data.host_pubkeys[i] ||
(compare && sensitive_data.host_pubkeys[i] &&
sshkey_equal(key, sensitive_data.host_pubkeys[i])))
return (i);
}
}
return (-1);
}
/* Inform the client of all hostkeys */
static void
notify_hostkeys(struct ssh *ssh)
{
struct sshbuf *buf;
struct sshkey *key;
u_int i, nkeys;
int r;
char *fp;
/* Some clients cannot cope with the hostkeys message, skip those. */
if (ssh->compat & SSH_BUG_HOSTKEYS)
return;
if ((buf = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new", __func__);
for (i = nkeys = 0; i < options.num_host_key_files; i++) {
key = get_hostkey_public_by_index(i, ssh);
if (key == NULL || key->type == KEY_UNSPEC ||
sshkey_is_cert(key))
continue;
fp = sshkey_fingerprint(key, options.fingerprint_hash,
SSH_FP_DEFAULT);
debug3("%s: key %d: %s %s", __func__, i,
sshkey_ssh_name(key), fp);
free(fp);
if (nkeys == 0) {
/*
* Start building the request when we find the
* first usable key.
*/
if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
(r = sshpkt_put_cstring(ssh, "hostkeys-00@openssh.com")) != 0 ||
(r = sshpkt_put_u8(ssh, 0)) != 0) /* want reply */
sshpkt_fatal(ssh, r, "%s: start request", __func__);
}
/* Append the key to the request */
sshbuf_reset(buf);
if ((r = sshkey_putb(key, buf)) != 0)
fatal("%s: couldn't put hostkey %d: %s",
__func__, i, ssh_err(r));
if ((r = sshpkt_put_stringb(ssh, buf)) != 0)
sshpkt_fatal(ssh, r, "%s: append key", __func__);
nkeys++;
}
debug3("%s: sent %u hostkeys", __func__, nkeys);
if (nkeys == 0)
fatal("%s: no hostkeys", __func__);
if ((r = sshpkt_send(ssh)) != 0)
sshpkt_fatal(ssh, r, "%s: send", __func__);
sshbuf_free(buf);
}
/*
* 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
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("drop_connection: p %d, r %d", p, r);
return (r < p) ? 1 : 0;
}
static void
usage(void)
{
fprintf(stderr, "%s, %s\n",
SSH_RELEASE,
#ifdef WITH_OPENSSL
OpenSSL_version(OPENSSL_VERSION)
#else
"without OpenSSL"
#endif
);
fprintf(stderr,
"usage: sshd [-46DdeiqTt] [-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 void
send_rexec_state(int fd, struct sshbuf *conf)
{
struct sshbuf *m;
int r;
debug3("%s: entering fd = %d config len %zu", __func__, fd,
sshbuf_len(conf));
/*
* Protocol from reexec master to child:
* string configuration
* string rngseed (only if OpenSSL is not self-seeded)
*/
if ((m = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __func__);
if ((r = sshbuf_put_stringb(m, conf)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
#if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY)
rexec_send_rng_seed(m);
#endif
if (ssh_msg_send(fd, 0, m) == -1)
fatal("%s: ssh_msg_send failed", __func__);
sshbuf_free(m);
debug3("%s: done", __func__);
}
static void
recv_rexec_state(int fd, struct sshbuf *conf)
{
struct sshbuf *m;
u_char *cp, ver;
size_t len;
int r;
debug3("%s: entering fd = %d", __func__, fd);
if ((m = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __func__);
if (ssh_msg_recv(fd, m) == -1)
fatal("%s: ssh_msg_recv failed", __func__);
if ((r = sshbuf_get_u8(m, &ver)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
if (ver != 0)
fatal("%s: rexec version mismatch", __func__);
if ((r = sshbuf_get_string(m, &cp, &len)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
if (conf != NULL && (r = sshbuf_put(conf, cp, len)))
fatal("%s: buffer error: %s", __func__, ssh_err(r));
#if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY)
rexec_recv_rng_seed(m);
#endif
free(cp);
sshbuf_free(m);
debug3("%s: done", __func__);
}
/* Accept a connection from inetd */
static void
server_accept_inetd(int *sock_in, int *sock_out)
{
int fd;
if (rexeced_flag) {
close(REEXEC_CONFIG_PASS_FD);
*sock_in = *sock_out = dup(STDIN_FILENO);
} else {
*sock_in = dup(STDIN_FILENO);
*sock_out = dup(STDOUT_FILENO);
}
/*
* We intentionally do not close the descriptors 0, 1, and 2
* as our code for setting the descriptors won't work if
* ttyfd happens to be one of those.
*/
if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
dup2(fd, STDIN_FILENO);
dup2(fd, STDOUT_FILENO);
if (!log_stderr)
dup2(fd, STDERR_FILENO);
if (fd > (log_stderr ? STDERR_FILENO : STDOUT_FILENO))
close(fd);
}
debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out);
}
/*
* 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;
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)
{
fd_set *fdset;
int i, j, ret, maxfd;
int ostartups = -1, startups = 0, listening = 0, lameduck = 0;
int startup_p[2] = { -1 , -1 };
char c = 0;
struct sockaddr_storage from;
socklen_t fromlen;
pid_t pid;
u_char rnd[256];
/* setup fd set for accept */
fdset = NULL;
maxfd = 0;
for (i = 0; i < num_listen_socks; i++)
if (listen_socks[i] > maxfd)
maxfd = listen_socks[i];
/* pipes connected to unauthenticated childs */
startup_pipes = xcalloc(options.max_startups, sizeof(int));
startup_flags = xcalloc(options.max_startups, sizeof(int));
for (i = 0; i < options.max_startups; i++)
startup_pipes[i] = -1;
/*
* Stay listening for connections until the system crashes or
* the daemon is killed with a signal.
*/
for (;;) {
if (ostartups != startups) {
setproctitle("[listener] %d of %d-%d startups",
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)
sighup_restart();
}
free(fdset);
fdset = xcalloc(howmany(maxfd + 1, NFDBITS),
sizeof(fd_mask));
for (i = 0; i < num_listen_socks; i++)
FD_SET(listen_socks[i], fdset);
for (i = 0; i < options.max_startups; i++)
if (startup_pipes[i] != -1)
FD_SET(startup_pipes[i], fdset);
/* Wait in select until there is a connection. */
ret = select(maxfd+1, fdset, NULL, NULL, NULL);
if (ret == -1 && errno != EINTR)
error("select: %.100s", strerror(errno));
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 (ret == -1)
continue;
for (i = 0; i < options.max_startups; i++) {
if (startup_pipes[i] == -1 ||
!FD_ISSET(startup_pipes[i], fdset))
continue;
switch (read(startup_pipes[i], &c, sizeof(c))) {
case -1:
if (errno == EINTR || errno == EAGAIN)
continue;
if (errno != EPIPE) {
error("%s: startup pipe %d (fd=%d): "
"read %s", __func__, i,
startup_pipes[i], strerror(errno));
}
/* FALLTHROUGH */
case 0:
/* child exited or completed auth */
close(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 (!FD_ISSET(listen_socks[i], fdset))
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 (drop_connection(startups) == 1) {
char *laddr = get_local_ipaddr(*newsock);
char *raddr = get_peer_ipaddr(*newsock);
char msg[] = "Exceeded MaxStartups\r\n";
verbose("drop connection #%d from [%s]:%d "
"on [%s]:%d past MaxStartups", startups,
raddr, get_peer_port(*newsock),
laddr, get_local_port(*newsock));
free(laddr);
free(raddr);
/* best-effort notification to client */
(void)write(*newsock, msg, strlen(msg));
close(*newsock);
continue;
}
if (pipe(startup_p) == -1) {
close(*newsock);
continue;
}
if (rexec_flag && 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];
if (maxfd < startup_p[0])
maxfd = 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();
if (rexec_flag) {
send_rexec_state(config_s[0], cfg);
close(config_s[0]);
}
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);
if (rexec_flag)
close(config_s[0]);
else {
/*
* Signal parent that the preliminaries
* for this child are complete. For the
* re-exec case, this happens after the
* child has received the rexec state
* from the server.
*/
(void)atomicio(vwrite, startup_pipe,
"\0", 1);
}
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]);
if (rexec_flag) {
send_rexec_state(config_s[0], cfg);
close(config_s[0]);
close(config_s[1]);
}
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));
}
}
}
/*
* If IP options are supported, make sure there are none (log and
* return an error if any are found). Basically we are worried about
* source routing; it can be used to pretend you are somebody
* (ip-address) you are not. That itself may be "almost acceptable"
* under certain circumstances, but rhosts authentication is useless
* if source routing is accepted. Notice also that if we just dropped
* source routing here, the other side could use IP spoofing to do
* rest of the interaction and could still bypass security. So we
* exit here if we detect any IP options.
*/
static void
check_ip_options(struct ssh *ssh)
{
#ifdef IP_OPTIONS
int sock_in = ssh_packet_get_connection_in(ssh);
struct sockaddr_storage from;
u_char opts[200];
socklen_t i, option_size = sizeof(opts), fromlen = sizeof(from);
char text[sizeof(opts) * 3 + 1];
memset(&from, 0, sizeof(from));
if (getpeername(sock_in, (struct sockaddr *)&from,
&fromlen) == -1)
return;
if (from.ss_family != AF_INET)
return;
/* XXX IPv6 options? */
if (getsockopt(sock_in, IPPROTO_IP, IP_OPTIONS, opts,
&option_size) >= 0 && option_size != 0) {
text[0] = '\0';
for (i = 0; i < option_size; i++)
snprintf(text + i*3, sizeof(text) - i*3,
" %2.2x", opts[i]);
fatal("Connection from %.100s port %d with IP opts: %.800s",
ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), text);
}
return;
#endif /* IP_OPTIONS */
}
/* Set the routing domain for this process */
static void
set_process_rdomain(struct ssh *ssh, const char *name)
{
#if defined(HAVE_SYS_SET_PROCESS_RDOMAIN)
if (name == NULL)
return; /* default */
if (strcmp(name, "%D") == 0) {
/* "expands" to routing domain of connection */
if ((name = ssh_packet_rdomain_in(ssh)) == NULL)
return;
}
/* NB. We don't pass 'ssh' to sys_set_process_rdomain() */
return sys_set_process_rdomain(name);
#elif defined(__OpenBSD__)
int rtable, ortable = getrtable();
const char *errstr;
if (name == NULL)
return; /* default */
if (strcmp(name, "%D") == 0) {
/* "expands" to routing domain of connection */
if ((name = ssh_packet_rdomain_in(ssh)) == NULL)
return;
}
rtable = (int)strtonum(name, 0, 255, &errstr);
if (errstr != NULL) /* Shouldn't happen */
fatal("Invalid routing domain \"%s\": %s", name, errstr);
if (rtable != ortable && setrtable(rtable) != 0)
fatal("Unable to set routing domain %d: %s",
rtable, strerror(errno));
debug("%s: set routing domain %d (was %d)", __func__, rtable, ortable);
#else /* defined(__OpenBSD__) */
fatal("Unable to set routing domain: not supported in this platform");
#endif
}
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("%s: ssh_digest_start", __func__);
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("%s: ssh_digest_update", __func__);
len = ssh_digest_bytes(SSH_DIGEST_SHA512);
hash = xmalloc(len);
if (ssh_digest_final(ctx, hash, len) != 0)
fatal("%s: ssh_digest_final", __func__);
options.timing_secret = PEEK_U64(hash);
freezero(hash, len);
ssh_digest_free(ctx);
ctx = NULL;
return;
}
if ((buf = sshbuf_new()) == NULL)
fatal("%s could not allocate buffer", __func__);
if ((r = sshkey_private_serialize(key, buf)) != 0)
fatal("sshkey_private_serialize: %s", ssh_err(r));
if (ssh_digest_update(ctx, sshbuf_ptr(buf), sshbuf_len(buf)) != 0)
fatal("%s: ssh_digest_update", __func__);
sshbuf_reset(buf);
sshbuf_free(buf);
}
/*
* Main program for the daemon.
*/
int
main(int ac, char **av)
{
struct ssh *ssh = NULL;
extern char *optarg;
extern int optind;
int r, opt, on = 1, already_daemon, remote_port;
int sock_in = -1, sock_out = -1, newsock = -1;
const char *remote_ip, *rdomain;
char *fp, *line, *laddr, *logfile = NULL;
int config_s[2] = { -1 , -1 };
u_int i, j;
u_int64_t ibytes, obytes;
mode_t new_umask;
struct sshkey *key;
struct sshkey *pubkey;
int keytype;
Authctxt *authctxt;
struct connection_info *connection_info = NULL;
#ifdef HAVE_SECUREWARE
(void)set_auth_parameters(ac, av);
#endif
__progname = ssh_get_progname(av[0]);
/* 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();
seed_rng();
/* 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:46DQRTdeiqrt")) != -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 'E':
logfile = optarg;
/* FALLTHROUGH */
case 'e':
log_stderr = 1;
break;
case 'i':
inetd_flag = 1;
break;
case 'r':
rexec_flag = 0;
break;
case 'R':
rexeced_flag = 1;
inetd_flag = 1;
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':
connection_info = get_connection_info(ssh, 0, 0);
if (parse_server_match_testspec(connection_info,
optarg) == -1)
exit(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) != 0)
exit(1);
free(line);
break;
case '?':
default:
usage();
break;
}
}
if (rexeced_flag || inetd_flag)
rexec_flag = 0;
if (!test_flag && rexec_flag && !path_absolute(av[0]))
fatal("sshd re-exec requires execution with an absolute path");
if (rexeced_flag)
closefrom(REEXEC_MIN_FREE_FD);
else
closefrom(REEXEC_DEVCRYPTO_RESERVED_FD);
/* If requested, redirect the logs to the specified logfile. */
if (logfile != NULL)
log_redirect_stderr_to(logfile);
/*
* 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);
/*
* 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 && connection_info != NULL)
fatal("Config test connection parameter (-C) provided without "
"test mode (-T)");
/* Fetch our configuration */
if ((cfg = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __func__);
if (rexeced_flag) {
recv_rexec_state(REEXEC_CONFIG_PASS_FD, cfg);
if (!debug_flag) {
startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
close(REEXEC_STARTUP_PIPE_FD);
/*
* Signal parent that this child is at a point where
* they can go away if they have a SIGHUP pending.
*/
(void)atomicio(vwrite, startup_pipe, "\0", 1);
}
}
else if (strcasecmp(config_file_name, "none") != 0)
load_server_config(config_file_name, cfg);
parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name,
cfg, NULL);
/* Fill in default values for those options not explicitly set. */
fill_default_server_options(&options);
/* challenge-response is implemented via keyboard interactive */
if (options.challenge_response_authentication)
options.kbd_interactive_authentication = 1;
/* 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 block, 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,
#ifdef WITH_OPENSSL
OpenSSL_version(OPENSSL_VERSION)
#else
"without OpenSSL"
#endif
);
/* Store privilege separation user for later use if required. */
privsep_chroot = use_privsep && (getuid() == 0 || geteuid() == 0);
if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) {
if (privsep_chroot || options.kerberos_authentication)
fatal("Privilege separation user %s does not exist",
SSH_PRIVSEP_USER);
} else {
privsep_pw = pwcopy(privsep_pw);
freezero(privsep_pw->pw_passwd, strlen(privsep_pw->pw_passwd));
privsep_pw->pw_passwd = xstrdup("*");
}
endpwent();
/* 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("Could not connect to agent \"%s\": %s",
options.host_key_agent, ssh_err(r));
}
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(ll, "Unable to load host key \"%s\": %s",
options.host_key_files[i], ssh_err(r));
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(ll, "Unable to shield host key \"%s\": %s",
options.host_key_files[i], ssh_err(r));
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(ll, "Unable to load host key \"%s\": %s",
options.host_key_files[i], ssh_err(r));
if (pubkey == NULL && key != NULL)
if ((r = sshkey_from_private(key, &pubkey)) != 0)
fatal("Could not demote key: \"%s\": %s",
options.host_key_files[i], ssh_err(r));
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("Could not load host certificate \"%s\": %s",
options.host_cert_files[i], ssh_err(r));
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_keys[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));
}
if (privsep_chroot) {
struct stat st;
if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
(S_ISDIR(st.st_mode) == 0))
fatal("Missing privilege separation directory: %s",
_PATH_PRIVSEP_CHROOT_DIR);
#ifdef HAVE_CYGWIN
if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
(st.st_uid != getuid () ||
(st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
#else
if (st.st_uid != 0 || (st.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) {
/*
* If no connection info was provided by -C then use
* use a blank one that will cause no predicate to match.
*/
if (connection_info == NULL)
connection_info = get_connection_info(ssh, 0, 0);
connection_info->test = 1;
parse_server_match_config(&options, connection_info);
dump_config(&options);
}
/* 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));
if (rexec_flag) {
if (rexec_argc < 0)
fatal("rexec_argc %d < 0", rexec_argc);
rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *));
for (i = 0; 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 + 1] = NULL;
}
/* 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 || rexeced_flag))
log_stderr = 1;
log_init(__progname, options.log_level, options.log_facility, log_stderr);
/*
* 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 */
signal(SIGPIPE, SIG_IGN);
/* Get a connection, either from inetd or a listening TCP socket */
if (inetd_flag) {
server_accept_inetd(&sock_in, &sock_out);
} else {
platform_pre_listen();
server_listen();
signal(SIGHUP, sighup_handler);
signal(SIGCHLD, main_sigchld_handler);
signal(SIGTERM, sigterm_handler);
signal(SIGQUIT, sigterm_handler);
/*
* 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);
}
/* 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 !defined(SSHD_ACQUIRES_CTTY)
/*
* If setsid is called, on some platforms sshd will later acquire a
* controlling terminal which will result in "could not set
* controlling tty" errors.
*/
if (!debug_flag && !inetd_flag && setsid() == -1)
error("setsid: %.100s", strerror(errno));
#endif
if (rexec_flag) {
int fd;
debug("rexec start in %d out %d newsock %d pipe %d sock %d",
sock_in, sock_out, newsock, startup_pipe, config_s[0]);
dup2(newsock, STDIN_FILENO);
dup2(STDIN_FILENO, STDOUT_FILENO);
if (startup_pipe == -1)
close(REEXEC_STARTUP_PIPE_FD);
else if (startup_pipe != REEXEC_STARTUP_PIPE_FD) {
dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD);
close(startup_pipe);
startup_pipe = REEXEC_STARTUP_PIPE_FD;
}
dup2(config_s[1], REEXEC_CONFIG_PASS_FD);
close(config_s[1]);
execv(rexec_argv[0], rexec_argv);
/* Reexec has failed, fall back and continue */
error("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL);
log_init(__progname, options.log_level,
options.log_facility, log_stderr);
/* Clean up fds */
close(REEXEC_CONFIG_PASS_FD);
newsock = sock_out = sock_in = dup(STDIN_FILENO);
if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
dup2(fd, STDIN_FILENO);
dup2(fd, STDOUT_FILENO);
if (fd > STDERR_FILENO)
close(fd);
}
debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d",
sock_in, sock_out, newsock, startup_pipe, config_s[0]);
}
/* Executed child processes don't need these. */
fcntl(sock_out, F_SETFD, FD_CLOEXEC);
fcntl(sock_in, F_SETFD, FD_CLOEXEC);
/*
* Disable the key regeneration alarm. We will not regenerate the
* key since we are no longer in a position to give it to anyone. We
* will not restart on SIGHUP since it no longer makes sense.
*/
alarm(0);
signal(SIGALRM, SIG_DFL);
signal(SIGHUP, SIG_DFL);
signal(SIGTERM, SIG_DFL);
signal(SIGQUIT, SIG_DFL);
signal(SIGCHLD, SIG_DFL);
signal(SIGINT, SIG_DFL);
/*
* Register our connection. This turns encryption off because we do
* not have a key.
*/
if ((ssh = ssh_packet_set_connection(NULL, sock_in, sock_out)) == NULL)
fatal("Unable to create connection");
the_active_state = ssh;
ssh_packet_set_server(ssh);
check_ip_options(ssh);
/* Prepare the channels layer */
channel_init_channels(ssh);
channel_set_af(ssh, options.address_family);
process_permitopen(ssh, &options);
/* Set SO_KEEPALIVE if requested. */
if (options.tcp_keep_alive && ssh_packet_connection_is_on_socket(ssh) &&
setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) == -1)
error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
if ((remote_port = ssh_remote_port(ssh)) < 0) {
debug("ssh_remote_port failed");
cleanup_exit(255);
}
if (options.routing_domain != NULL)
set_process_rdomain(ssh, options.routing_domain);
/*
* The rest of the code depends on the fact that
* ssh_remote_ipaddr() caches the remote ip, even if
* the socket goes away.
*/
remote_ip = ssh_remote_ipaddr(ssh);
#ifdef SSH_AUDIT_EVENTS
audit_connection_from(remote_ip, remote_port);
#endif
rdomain = ssh_packet_rdomain_in(ssh);
/* Log the connection. */
laddr = get_local_ipaddr(sock_in);
verbose("Connection from %s port %d on %s port %d%s%s%s",
remote_ip, remote_port, laddr, ssh_local_port(ssh),
rdomain == NULL ? "" : " rdomain \"",
rdomain == NULL ? "" : rdomain,
rdomain == NULL ? "" : "\"");
free(laddr);
/*
* We don't want to listen forever unless the other side
* successfully authenticates itself. So we set up an alarm which is
* cleared after successful authentication. A limit of zero
* indicates no limit. Note that we don't set the alarm in debugging
* mode; it is just annoying to have the server exit just when you
* are about to discover the bug.
*/
signal(SIGALRM, grace_alarm_handler);
if (!debug_flag)
alarm(options.login_grace_time);
if (kex_exchange_identification(ssh, -1, options.version_addendum) != 0)
cleanup_exit(255); /* error already logged */
ssh_packet_set_nonblocking(ssh);
/* allocate authentication context */
authctxt = xcalloc(1, sizeof(*authctxt));
ssh->authctxt = authctxt;
authctxt->loginmsg = loginmsg;
/* XXX global for cleanup, access from other modules */
the_authctxt = authctxt;
/* Set default key authentication options */
if ((auth_opts = sshauthopt_new_with_keys_defaults()) == NULL)
fatal("allocation failed");
/* prepare buffer to collect messages to display to user after login */
if ((loginmsg = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __func__);
auth_debug_reset();
if (use_privsep) {
if (privsep_preauth(ssh) == 1)
goto authenticated;
} else if (have_agent) {
if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
error("Unable to get agent socket: %s", ssh_err(r));
have_agent = 0;
}
}
/* perform the key exchange */
/* authenticate user and start session */
do_ssh2_kex(ssh);
do_authentication2(ssh);
/*
* If we use privilege separation, the unprivileged child transfers
* the current keystate and exits
*/
if (use_privsep) {
mm_send_keystate(ssh, pmonitor);
ssh_packet_clear_keys(ssh);
exit(0);
}
authenticated:
/*
* Cancel the alarm we set to limit the time taken for
* authentication.
*/
alarm(0);
signal(SIGALRM, SIG_DFL);
authctxt->authenticated = 1;
if (startup_pipe != -1) {
close(startup_pipe);
startup_pipe = -1;
}
#ifdef SSH_AUDIT_EVENTS
audit_event(ssh, SSH_AUTH_SUCCESS);
#endif
#ifdef GSSAPI
if (options.gss_authentication) {
temporarily_use_uid(authctxt->pw);
ssh_gssapi_storecreds();
restore_uid();
}
#endif
#ifdef USE_PAM
if (options.use_pam) {
do_pam_setcred(1);
do_pam_session(ssh);
}
#endif
/*
* In privilege separation, we fork another child and prepare
* file descriptor passing.
*/
if (use_privsep) {
privsep_postauth(ssh, authctxt);
/* the monitor process [priv] will not return */
}
ssh_packet_set_timeout(ssh, options.client_alive_interval,
options.client_alive_count_max);
/* Try to send all our hostkeys to the client */
notify_hostkeys(ssh);
/* Start session. */
do_authenticated(ssh, authctxt);
/* The connection has been terminated. */
ssh_packet_get_bytes(ssh, &ibytes, &obytes);
verbose("Transferred: sent %llu, received %llu bytes",
(unsigned long long)obytes, (unsigned long long)ibytes);
verbose("Closing connection to %.500s port %d", remote_ip, remote_port);
#ifdef USE_PAM
if (options.use_pam)
finish_pam();
#endif /* USE_PAM */
#ifdef SSH_AUDIT_EVENTS
PRIVSEP(audit_event(ssh, SSH_CONNECTION_CLOSE));
#endif
ssh_packet_close(ssh);
if (use_privsep)
mm_terminate();
exit(0);
}
int
sshd_hostkey_sign(struct ssh *ssh, struct sshkey *privkey,
struct sshkey *pubkey, u_char **signature, size_t *slenp,
const u_char *data, size_t dlen, const char *alg)
{
int r;
if (use_privsep) {
if (privkey) {
if (mm_sshkey_sign(ssh, privkey, signature, slenp,
data, dlen, alg, options.sk_provider,
ssh->compat) < 0)
fatal("%s: privkey sign failed", __func__);
} else {
if (mm_sshkey_sign(ssh, pubkey, signature, slenp,
data, dlen, alg, options.sk_provider,
ssh->compat) < 0)
fatal("%s: pubkey sign failed", __func__);
}
} else {
if (privkey) {
if (sshkey_sign(privkey, signature, slenp, data, dlen,
alg, options.sk_provider, ssh->compat) < 0)
fatal("%s: privkey sign failed", __func__);
} else {
if ((r = ssh_agent_sign(auth_sock, pubkey,
signature, slenp, data, dlen, alg,
ssh->compat)) != 0) {
fatal("%s: agent sign failed: %s",
__func__, ssh_err(r));
}
}
}
return 0;
}
/* SSH2 key exchange */
static void
do_ssh2_kex(struct ssh *ssh)
{
char *myproposal[PROPOSAL_MAX] = { KEX_SERVER };
struct kex *kex;
int r;
myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal(
options.kex_algorithms);
myproposal[PROPOSAL_ENC_ALGS_CTOS] = compat_cipher_proposal(
options.ciphers);
myproposal[PROPOSAL_ENC_ALGS_STOC] = compat_cipher_proposal(
options.ciphers);
myproposal[PROPOSAL_MAC_ALGS_CTOS] =
myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
if (options.compression == COMP_NONE) {
myproposal[PROPOSAL_COMP_ALGS_CTOS] =
myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
}
if (options.rekey_limit || options.rekey_interval)
ssh_packet_set_rekey_limits(ssh, options.rekey_limit,
options.rekey_interval);
myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = compat_pkalg_proposal(
list_hostkey_types());
/* start key exchange */
if ((r = kex_setup(ssh, myproposal)) != 0)
fatal("kex_setup: %s", ssh_err(r));
kex = ssh->kex;
#ifdef WITH_OPENSSL
kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;
kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;
kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
# ifdef OPENSSL_HAS_ECC
kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
# endif
#endif
kex->kex[KEX_C25519_SHA256] = kex_gen_server;
kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_server;
kex->load_host_public_key=&get_hostkey_public_by_type;
kex->load_host_private_key=&get_hostkey_private_by_type;
kex->host_key_index=&get_hostkey_index;
kex->sign = sshd_hostkey_sign;
ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &kex->done);
session_id2 = kex->session_id;
session_id2_len = kex->session_id_len;
#ifdef DEBUG_KEXDH
/* send 1st encrypted/maced/compressed message */
packet_start(SSH2_MSG_IGNORE);
packet_put_cstring("markus");
packet_send();
packet_write_wait();
#endif
debug("KEX done");
}
/* server specific fatal cleanup */
void
cleanup_exit(int i)
{
if (the_active_state != NULL && the_authctxt != NULL) {
do_cleanup(the_active_state, the_authctxt);
if (use_privsep && privsep_is_preauth &&
pmonitor != NULL && pmonitor->m_pid > 1) {
debug("Killing privsep child %d", pmonitor->m_pid);
if (kill(pmonitor->m_pid, SIGKILL) != 0 &&
errno != ESRCH)
error("%s: kill(%d): %s", __func__,
pmonitor->m_pid, strerror(errno));
}
}
#ifdef SSH_AUDIT_EVENTS
/* done after do_cleanup so it can cancel the PAM auth 'thread' */
if (the_active_state != NULL && (!use_privsep || mm_is_monitor()))
audit_event(the_active_state, SSH_CONNECTION_ABANDON);
#endif
_exit(i);
}
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