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openssh/sshd.c
Darren Tucker ddc0f38148 Remove UNICOS support. 
The code required to support it is quite invasive to the mainline
code that is synced with upstream and is an ongoing maintenance burden.
Both the hardware and software are literal museum pieces these days and
we could not find anyone still running OpenSSH on one.
2018-02-15 20:04:02 +11:00

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/* $OpenBSD: sshd.c,v 1.504 2018/02/11 21:16:56 dtucker 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 "buffer.h"
#include "misc.h"
#include "match.h"
#include "servconf.h"
#include "uidswap.h"
#include "compat.h"
#include "cipher.h"
#include "digest.h"
#include "key.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 "version.h"
#include "ssherr.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.
*/
int test_flag = 0;
/* Flag indicating that the daemon is being started from inetd. */
int inetd_flag = 0;
/* Flag indicating that sshd should not detach and become a daemon. */
int no_daemon_flag = 0;
/* debug goes to stderr unless inetd_flag is set */
int log_stderr = 0;
/* Saved arguments to main(). */
char **saved_argv;
int saved_argc;
/* re-exec */
int rexeced_flag = 0;
int rexec_flag = 1;
int rexec_argc = 0;
char **rexec_argv;
/*
* The sockets that the server is listening; this is used in the SIGHUP
* signal handler.
*/
#define MAX_LISTEN_SOCKS 16
int listen_socks[MAX_LISTEN_SOCKS];
int num_listen_socks = 0;
/*
* the client's version string, passed by sshd2 in compat mode. if != NULL,
* sshd will skip the version-number exchange
*/
char *client_version_string = NULL;
char *server_version_string = NULL;
/* Daemon's agent connection */
int auth_sock = -1;
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;
/* options.max_startup sized array of fd ints */
int *startup_pipes = NULL;
int startup_pipe; /* 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 authentication context */
Authctxt *the_authctxt = NULL;
/* sshd_config buffer */
Buffer cfg;
/* message to be displayed after login */
Buffer 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(void);
/*
* 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)
{
int save_errno = errno;
received_sighup = 1;
errno = save_errno;
}
/*
* 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 < 0 && 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);
}
/* Log error and exit. */
sigdie("Timeout before authentication for %s port %d",
ssh_remote_ipaddr(active_state), ssh_remote_port(active_state));
}
static void
sshd_exchange_identification(struct ssh *ssh, int sock_in, int sock_out)
{
u_int i;
int remote_major, remote_minor;
char *s;
char buf[256]; /* Must not be larger than remote_version. */
char remote_version[256]; /* Must be at least as big as buf. */
xasprintf(&server_version_string, "SSH-%d.%d-%.100s%s%s\r\n",
PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION,
*options.version_addendum == '\0' ? "" : " ",
options.version_addendum);
/* Send our protocol version identification. */
if (atomicio(vwrite, sock_out, server_version_string,
strlen(server_version_string))
!= strlen(server_version_string)) {
logit("Could not write ident string to %s port %d",
ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
cleanup_exit(255);
}
/* Read other sides version identification. */
memset(buf, 0, sizeof(buf));
for (i = 0; i < sizeof(buf) - 1; i++) {
if (atomicio(read, sock_in, &buf[i], 1) != 1) {
logit("Did not receive identification string "
"from %s port %d",
ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
cleanup_exit(255);
}
if (buf[i] == '\r') {
buf[i] = 0;
/* Kludge for F-Secure Macintosh < 1.0.2 */
if (i == 12 &&
strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
break;
continue;
}
if (buf[i] == '\n') {
buf[i] = 0;
break;
}
}
buf[sizeof(buf) - 1] = 0;
client_version_string = xstrdup(buf);
/*
* Check that the versions match. In future this might accept
* several versions and set appropriate flags to handle them.
*/
if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
&remote_major, &remote_minor, remote_version) != 3) {
s = "Protocol mismatch.\n";
(void) atomicio(vwrite, sock_out, s, strlen(s));
logit("Bad protocol version identification '%.100s' "
"from %s port %d", client_version_string,
ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
close(sock_in);
close(sock_out);
cleanup_exit(255);
}
debug("Client protocol version %d.%d; client software version %.100s",
remote_major, remote_minor, remote_version);
ssh->compat = compat_datafellows(remote_version);
if ((ssh->compat & SSH_BUG_PROBE) != 0) {
logit("probed from %s port %d with %s. Don't panic.",
ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
client_version_string);
cleanup_exit(255);
}
if ((ssh->compat & SSH_BUG_SCANNER) != 0) {
logit("scanned from %s port %d with %s. Don't panic.",
ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
client_version_string);
cleanup_exit(255);
}
if ((ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
logit("Client version \"%.100s\" uses unsafe RSA signature "
"scheme; disabling use of RSA keys", remote_version);
}
chop(server_version_string);
debug("Local version string %.200s", server_version_string);
if (remote_major != 2 &&
!(remote_major == 1 && remote_minor == 99)) {
s = "Protocol major versions differ.\n";
(void) atomicio(vwrite, sock_out, s, strlen(s));
close(sock_in);
close(sock_out);
logit("Protocol major versions differ for %s port %d: "
"%.200s vs. %.200s",
ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
server_version_string, client_version_string);
cleanup_exit(255);
}
}
/* 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]) {
key_free(sensitive_data.host_keys[i]);
sensitive_data.host_keys[i] = NULL;
}
if (sensitive_data.host_certificates[i]) {
key_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;
for (i = 0; i < options.num_host_key_files; i++) {
if (sensitive_data.host_keys[i]) {
tmp = key_demote(sensitive_data.host_keys[i]);
key_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 */
if (options.gss_authentication)
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) < 0)
fatal("setgroups: %.100s", strerror(errno));
permanently_set_uid(privsep_pw);
}
}
static int
privsep_preauth(Authctxt *authctxt)
{
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 = &active_state->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(authctxt, pmonitor);
/* Wait for the child's exit status */
while (waitpid(pid, &status, 0) < 0) {
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(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);
buffer_clear(&loginmsg);
monitor_clear_keystate(pmonitor);
monitor_child_postauth(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(pmonitor);
/*
* Tell the packet layer that authentication was successful, since
* this information is not part of the key state.
*/
packet_set_authenticated();
}
static char *
list_hostkey_types(void)
{
Buffer b;
const char *p;
char *ret;
u_int i;
struct sshkey *key;
buffer_init(&b);
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;
/* Check that the key is accepted in HostkeyAlgorithms */
if (match_pattern_list(sshkey_ssh_name(key),
options.hostkeyalgorithms, 0) != 1) {
debug3("%s: %s key not permitted by HostkeyAlgorithms",
__func__, sshkey_ssh_name(key));
continue;
}
switch (key->type) {
case KEY_RSA:
case KEY_DSA:
case KEY_ECDSA:
case KEY_ED25519:
if (buffer_len(&b) > 0)
buffer_append(&b, ",", 1);
p = key_ssh_name(key);
buffer_append(&b, p, strlen(p));
/* for RSA we also support SHA2 signatures */
if (key->type == KEY_RSA) {
p = ",rsa-sha2-512,rsa-sha2-256";
buffer_append(&b, p, strlen(p));
}
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:
case KEY_DSA_CERT:
case KEY_ECDSA_CERT:
case KEY_ED25519_CERT:
if (buffer_len(&b) > 0)
buffer_append(&b, ",", 1);
p = key_ssh_name(key);
buffer_append(&b, p, strlen(p));
break;
}
}
if ((ret = sshbuf_dup_string(&b)) == NULL)
fatal("%s: sshbuf_dup_string failed", __func__);
buffer_free(&b);
debug("list_hostkey_types: %s", 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:
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 &&
(key->type != KEY_ECDSA || key->ecdsa_nid == nid))
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 (key_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 (datafellows & 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) {
packet_start(SSH2_MSG_GLOBAL_REQUEST);
packet_put_cstring("hostkeys-00@openssh.com");
packet_put_char(0); /* want-reply */
}
sshbuf_reset(buf);
if ((r = sshkey_putb(key, buf)) != 0)
fatal("%s: couldn't put hostkey %d: %s",
__func__, i, ssh_err(r));
packet_put_string(sshbuf_ptr(buf), sshbuf_len(buf));
nkeys++;
}
debug3("%s: sent %u hostkeys", __func__, nkeys);
if (nkeys == 0)
fatal("%s: no hostkeys", __func__);
packet_send();
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
SSLeay_version(SSLEAY_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, Buffer *conf)
{
Buffer m;
char *cp;
u_int len;
debug3("%s: entering fd = %d", __func__, fd);
buffer_init(&m);
if (ssh_msg_recv(fd, &m) == -1)
fatal("%s: ssh_msg_recv failed", __func__);
if (buffer_get_char(&m) != 0)
fatal("%s: rexec version mismatch", __func__);
cp = buffer_get_string(&m, &len);
if (conf != NULL)
buffer_append(conf, cp, len);
free(cp);
#if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY)
rexec_recv_rng_seed(&m);
#endif
buffer_free(&m);
debug3("%s: done", __func__);
}
/* Accept a connection from inetd */
static void
server_accept_inetd(int *sock_in, int *sock_out)
{
int fd;
startup_pipe = -1;
if (rexeced_flag) {
close(REEXEC_CONFIG_PASS_FD);
*sock_in = *sock_out = dup(STDIN_FILENO);
if (!debug_flag) {
startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
close(REEXEC_STARTUP_PIPE_FD);
}
} 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 < 0) {
/* 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) < 0) {
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) < 0)
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 startups = 0;
int startup_p[2] = { -1 , -1 };
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));
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 (received_sighup)
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 < 0 && 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 < 0)
continue;
for (i = 0; i < options.max_startups; i++)
if (startup_pipes[i] != -1 &&
FD_ISSET(startup_pipes[i], fdset)) {
/*
* the read end of the pipe is ready
* if the child has closed the pipe
* after successful authentication
* or if the child has died
*/
close(startup_pipes[i]);
startup_pipes[i] = -1;
startups--;
}
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 < 0) {
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);
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);
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++;
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]);
}
break;
}
/*
* Normal production daemon. Fork, and have
* the child process the connection. The
* parent continues listening.
*/
platform_pre_fork();
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 break out of the loop 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]);
break;
}
/* Parent. Stay in the loop. */
platform_post_fork_parent(pid);
if (pid < 0)
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));
}
/* child process check (or debug mode) */
if (num_listen_socks < 0)
break;
}
}
/*
* 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 autentication 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) < 0)
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
}
/*
* 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;
ssh_malloc_init(); /* must be called before any mallocs */
#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();
/* 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);
break;
case 't':
test_flag = 1;
break;
case 'T':
test_flag = 2;
break;
case 'C':
connection_info = get_connection_info(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 && (av[0] == NULL || *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);
#ifdef WITH_OPENSSL
OpenSSL_add_all_algorithms();
#endif
/* 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 */
buffer_init(&cfg);
if (rexeced_flag)
recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg);
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);
seed_rng();
/* 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
SSLeay_version(SSLEAY_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++) {
if (options.host_key_files[i] == NULL)
continue;
key = key_load_private(options.host_key_files[i], "", NULL);
pubkey = key_load_public(options.host_key_files[i], NULL);
if (pubkey == NULL && key != NULL)
pubkey = key_demote(key);
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;
} else {
error("Could not 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:
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);
}
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;
key = key_load_public(options.host_cert_files[i], NULL);
if (key == NULL) {
error("Could not load host certificate: %s",
options.host_cert_files[i]);
continue;
}
if (!key_is_cert(key)) {
error("Certificate file is not a certificate: %s",
options.host_cert_files[i]);
key_free(key);
continue;
}
/* Find matching private key */
for (j = 0; j < options.num_host_key_files; j++) {
if (key_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]);
key_free(key);
continue;
}
sensitive_data.host_certificates[j] = key;
debug("host certificate: #%u type %d %s", j, key->type,
key_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(0, 0);
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) < 0)
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() < 0)
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.
*/
packet_set_connection(sock_in, sock_out);
packet_set_server();
ssh = active_state; /* XXX */
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 && packet_connection_is_on_socket() &&
setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0)
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);
sshd_exchange_identification(ssh, sock_in, sock_out);
packet_set_nonblocking();
/* allocate authentication context */
authctxt = xcalloc(1, sizeof(*authctxt));
authctxt->loginmsg = &loginmsg;
/* XXX global for cleanup, access from other modules */
the_authctxt = authctxt;
/* prepare buffer to collect messages to display to user after login */
buffer_init(&loginmsg);
auth_debug_reset();
if (use_privsep) {
if (privsep_preauth(authctxt) == 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();
do_authentication2(authctxt);
/*
* If we use privilege separation, the unprivileged child transfers
* the current keystate and exits
*/
if (use_privsep) {
mm_send_keystate(pmonitor);
packet_clear_keys();
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_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();
}
#endif
/*
* In privilege separation, we fork another child and prepare
* file descriptor passing.
*/
if (use_privsep) {
privsep_postauth(authctxt);
/* the monitor process [priv] will not return */
}
packet_set_timeout(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. */
packet_get_bytes(&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_CONNECTION_CLOSE));
#endif
packet_close();
if (use_privsep)
mm_terminate();
exit(0);
}
int
sshd_hostkey_sign(struct sshkey *privkey, struct sshkey *pubkey,
u_char **signature, size_t *slen, const u_char *data, size_t dlen,
const char *alg, u_int flag)
{
int r;
u_int xxx_slen, xxx_dlen = dlen;
if (privkey) {
if (PRIVSEP(key_sign(privkey, signature, &xxx_slen, data, xxx_dlen,
alg) < 0))
fatal("%s: key_sign failed", __func__);
if (slen)
*slen = xxx_slen;
} else if (use_privsep) {
if (mm_key_sign(pubkey, signature, &xxx_slen, data, xxx_dlen,
alg) < 0)
fatal("%s: pubkey_sign failed", __func__);
if (slen)
*slen = xxx_slen;
} else {
if ((r = ssh_agent_sign(auth_sock, pubkey, signature, slen,
data, dlen, alg, datafellows)) != 0)
fatal("%s: ssh_agent_sign failed: %s",
__func__, ssh_err(r));
}
return 0;
}
/* SSH2 key exchange */
static void
do_ssh2_kex(void)
{
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)
packet_set_rekey_limits(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(active_state, myproposal)) != 0)
fatal("kex_setup: %s", ssh_err(r));
kex = active_state->kex;
#ifdef WITH_OPENSSL
kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
kex->kex[KEX_DH_GRP14_SHA256] = kexdh_server;
kex->kex[KEX_DH_GRP16_SHA512] = kexdh_server;
kex->kex[KEX_DH_GRP18_SHA512] = kexdh_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] = kexecdh_server;
# endif
#endif
kex->kex[KEX_C25519_SHA256] = kexc25519_server;
kex->server = 1;
kex->client_version_string=client_version_string;
kex->server_version_string=server_version_string;
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(active_state, 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)
{
struct ssh *ssh = active_state; /* XXX */
if (the_authctxt) {
do_cleanup(ssh, 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 (!use_privsep || mm_is_monitor())
audit_event(SSH_CONNECTION_ABANDON);
#endif
_exit(i);
}
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