Using realloc to remove MAX_LISTEN_SOCKS limit on sshd.c

[Dan Armstrong]

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OpenSSH developers,

I have removed the fixed, arbitrary limit on the number of ListenAddress
allowed by using realloc to dynamically expand listen_socks as needed.
This completely removes MAX_LISTEN_SOCKS from the source. I made this
change on the version of OpenSSH shipped with CentOS 5.2, version
4.3p2. Please see the attached .c file and .diff file. Please add
these changes to OpenSSH to save people from having to predetermine
their workload before compilation. It can also save some people some
grief - I've been unable to login to a server because of this one.

sshd.c.orig is the original file bundled in the CentOS source RPM

sshd.c is the new version

sshd.c.diff is the difference between then: diff sshd.c.orig sshd.c


Thank you,
--
Dan Armstrong
AO Industries, Inc.
***@aoindustries.com
Work: [phone]
Cell: [phone]


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filename="sshd.c"

/*
* Author: Tatu Ylonen <***@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <***@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"
RCSID("$OpenBSD: sshd.c,v 1.318 2005/12/24 02:27:41 djm Exp $");

#include <openssl/dh.h>
#include <openssl/bn.h>
#include <openssl/md5.h>
#include <openssl/rand.h>
#ifdef HAVE_SECUREWARE
#include <sys/security.h>
#include <prot.h>
#endif

#include "ssh.h"
#include "ssh1.h"
#include "ssh2.h"
#include "xmalloc.h"
#include "rsa.h"
#include "sshpty.h"
#include "packet.h"
#include "log.h"
#include "servconf.h"
#include "uidswap.h"
#include "compat.h"
#include "buffer.h"
#include "bufaux.h"
#include "cipher.h"
#include "kex.h"
#include "key.h"
#include "dh.h"
#include "myproposal.h"
#include "authfile.h"
#include "pathnames.h"
#include "atomicio.h"
#include "canohost.h"
#include "auth.h"
#include "misc.h"
#include "msg.h"
#include "dispatch.h"
#include "channels.h"
#include "session.h"
#include "monitor_mm.h"
#include "monitor.h"
#include "monitor_wrap.h"
#include "monitor_fdpass.h"

#ifdef LIBWRAP
#include <tcpd.h>
#include <syslog.h>
int allow_severity = LOG_INFO;
int deny_severity = LOG_WARNING;
#endif /* LIBWRAP */

#ifndef O_NOCTTY
#define O_NOCTTY 0
#endif

/* 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;

/* Flag indicating that the daemon should only test the configuration and keys. */
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.
*/
int *listen_socks = NULL;
int listen_socks_len = 0;
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;

/* for rekeying XXX fixme */
Kex *xxx_kex;

/*
* 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 {
Key *server_key; /* ephemeral server key */
Key *ssh1_host_key; /* ssh1 host key */
Key **host_keys; /* all private host keys */
int have_ssh1_key;
int have_ssh2_key;
u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
} sensitive_data;

/*
* Flag indicating whether the RSA server key needs to be regenerated.
* Is set in the SIGALRM handler and cleared when the key is regenerated.
*/
static volatile sig_atomic_t key_do_regen = 0;

/* 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 = MAXHOSTNAMELEN;

/* 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;
struct monitor *pmonitor = NULL;

/* global authentication context */
Authctxt *the_authctxt = NULL;

/* message to be displayed after login */
Buffer loginmsg;

/* Prototypes for various functions defined later in this file. */
void destroy_sensitive_data(void);
void demote_sensitive_data(void);

static void do_ssh1_kex(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).
*/
static void
sighup_handler(int sig)
{
int save_errno = errno;

received_sighup = 1;
signal(SIGHUP, sighup_handler);
errno = save_errno;
}

/*
* Called from the main program after receiving SIGHUP.
* Restarts the server.
*/
static void
sighup_restart(void)
{
logit("Received SIGHUP; restarting.");
close_listen_socks();
close_startup_pipes();
execv(saved_argv[0], saved_argv);
logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
strerror(errno));
exit(1);
}

/*
* Generic signal handler for terminating signals in the master daemon.
*/
static void
sigterm_handler(int sig)
{
received_sigterm = sig;
}

/*
* SIGCHLD handler. This is called whenever a child dies. This will then
* reap any zombies left by exited children.
*/
static void
main_sigchld_handler(int sig)
{
int save_errno = errno;
pid_t pid;
int status;

while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
(pid < 0 && errno == EINTR))
;

signal(SIGCHLD, main_sigchld_handler);
errno = save_errno;
}

/*
* Signal handler for the alarm after the login grace period has expired.
*/
static void
grace_alarm_handler(int sig)
{
/* XXX no idea how fix this signal handler */

if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0)
kill(pmonitor->m_pid, SIGALRM);

/* Log error and exit. */
fatal("Timeout before authentication for %s", get_remote_ipaddr());
}

/*
* Signal handler for the key regeneration alarm. Note that this
* alarm only occurs in the daemon waiting for connections, and it does not
* do anything with the private key or random state before forking.
* Thus there should be no concurrency control/asynchronous execution
* problems.
*/
static void
generate_ephemeral_server_key(void)
{
u_int32_t rnd = 0;
int i;

verbose("Generating %s%d bit RSA key.",
sensitive_data.server_key ? "new " : "", options.server_key_bits);
if (sensitive_data.server_key != NULL)
key_free(sensitive_data.server_key);
sensitive_data.server_key = key_generate(KEY_RSA1,
options.server_key_bits);
verbose("RSA key generation complete.");

for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
if (i % 4 == 0)
rnd = arc4random();
sensitive_data.ssh1_cookie[i] = rnd & 0xff;
rnd >>= 8;
}
arc4random_stir();
}

static void
key_regeneration_alarm(int sig)
{
int save_errno = errno;

signal(SIGALRM, SIG_DFL);
errno = save_errno;
key_do_regen = 1;
}

static void
sshd_exchange_identification(int sock_in, int sock_out)
{
u_int i;
int mismatch;
int remote_major, remote_minor;
int major, 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. */

if ((options.protocol & SSH_PROTO_1) &&
(options.protocol & SSH_PROTO_2)) {
major = PROTOCOL_MAJOR_1;
minor = 99;
} else if (options.protocol & SSH_PROTO_2) {
major = PROTOCOL_MAJOR_2;
minor = PROTOCOL_MINOR_2;
} else {
major = PROTOCOL_MAJOR_1;
minor = PROTOCOL_MINOR_1;
}
snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
server_version_string = xstrdup(buf);

/* 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", get_remote_ipaddr());
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",
get_remote_ipaddr());
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));
close(sock_in);
close(sock_out);
logit("Bad protocol version identification '%.100s' from %s",
client_version_string, get_remote_ipaddr());
cleanup_exit(255);
}
debug("Client protocol version %d.%d; client software version %.100s",
remote_major, remote_minor, remote_version);

compat_datafellows(remote_version);

if (datafellows & SSH_BUG_PROBE) {
logit("probed from %s with %s. Don't panic.",
get_remote_ipaddr(), client_version_string);
cleanup_exit(255);
}

if (datafellows & SSH_BUG_SCANNER) {
logit("scanned from %s with %s. Don't panic.",
get_remote_ipaddr(), client_version_string);
cleanup_exit(255);
}

mismatch = 0;
switch (remote_major) {
case 1:
if (remote_minor == 99) {
if (options.protocol & SSH_PROTO_2)
enable_compat20();
else
mismatch = 1;
break;
}
if (!(options.protocol & SSH_PROTO_1)) {
mismatch = 1;
break;
}
if (remote_minor < 3) {
packet_disconnect("Your ssh version is too old and "
"is no longer supported. Please install a newer version.");
} else if (remote_minor == 3) {
/* note that this disables agent-forwarding */
enable_compat13();
}
break;
case 2:
if (options.protocol & SSH_PROTO_2) {
enable_compat20();
break;
}
/* FALLTHROUGH */
default:
mismatch = 1;
break;
}
chop(server_version_string);
debug("Local version string %.200s", server_version_string);

if (mismatch) {
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: %.200s vs. %.200s",
get_remote_ipaddr(),
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)
{
int i;

if (sensitive_data.server_key) {
key_free(sensitive_data.server_key);
sensitive_data.server_key = NULL;
}
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;
}
}
sensitive_data.ssh1_host_key = NULL;
memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
}

/* Demote private to public keys for network child */
void
demote_sensitive_data(void)
{
Key *tmp;
int i;

if (sensitive_data.server_key) {
tmp = key_demote(sensitive_data.server_key);
key_free(sensitive_data.server_key);
sensitive_data.server_key = tmp;
}

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;
if (tmp->type == KEY_RSA1)
sensitive_data.ssh1_host_key = tmp;
}
}

/* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
}

static void
privsep_preauth_child(void)
{
u_int32_t rnd[256];
gid_t gidset[1];
struct passwd *pw;
int i;

/* Enable challenge-response authentication for privilege separation */
privsep_challenge_enable();

for (i = 0; i < 256; i++)
rnd[i] = arc4random();
RAND_seed(rnd, sizeof(rnd));

/* Demote the private keys to public keys. */
demote_sensitive_data();

if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
fatal("Privilege separation user %s does not exist",
SSH_PRIVSEP_USER);
memset(pw->pw_passwd, 0, strlen(pw->pw_passwd));
endpwent();

/* 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)pw->pw_uid,
(u_int)pw->pw_gid);
#if 0
/* XXX not ready, too heavy after chroot */
do_setusercontext(pw);
#else
gidset[0] = pw->pw_gid;
if (setgroups(1, gidset) < 0)
fatal("setgroups: %.100s", strerror(errno));
permanently_set_uid(pw);
#endif
}

static int
privsep_preauth(Authctxt *authctxt)
{
int status;
pid_t pid;

/* 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 = &xxx_kex;

pid = fork();
if (pid == -1) {
fatal("fork of unprivileged child failed");
} else if (pid != 0) {
debug2("Network child is on pid %ld", (long)pid);

close(pmonitor->m_recvfd);
pmonitor->m_pid = pid;
monitor_child_preauth(authctxt, pmonitor);
close(pmonitor->m_sendfd);

/* Sync memory */
monitor_sync(pmonitor);

/* Wait for the child's exit status */
while (waitpid(pid, &status, 0) < 0)
if (errno != EINTR)
break;
return (1);
} else {
/* child */

close(pmonitor->m_sendfd);

/* Demote the child */
if (getuid() == 0 || geteuid() == 0)
privsep_preauth_child();
setproctitle("%s", "[net]");
}
return (0);
}

static void
privsep_postauth(Authctxt *authctxt)
{
#ifdef DISABLE_FD_PASSING
if (1) {
#else
if (authctxt->pw->pw_uid == 0 || options.use_login) {
#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) {
debug2("User child is on pid %ld", (long)pmonitor->m_pid);
close(pmonitor->m_recvfd);
buffer_clear(&loginmsg);
monitor_child_postauth(pmonitor);

/* NEVERREACHED */
exit(0);
}

close(pmonitor->m_sendfd);

/* Demote the private keys to public keys. */
demote_sensitive_data();

/* 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;
int i;

buffer_init(&b);
for (i = 0; i < options.num_host_key_files; i++) {
Key *key = sensitive_data.host_keys[i];
if (key == NULL)
continue;
switch (key->type) {
case KEY_RSA:
case KEY_DSA:
if (buffer_len(&b) > 0)
buffer_append(&b, ",", 1);
p = key_ssh_name(key);
buffer_append(&b, p, strlen(p));
break;
}
}
buffer_append(&b, "\0", 1);
ret = xstrdup(buffer_ptr(&b));
buffer_free(&b);
debug("list_hostkey_types: %s", ret);
return ret;
}

Key *
get_hostkey_by_type(int type)
{
int i;

for (i = 0; i < options.num_host_key_files; i++) {
Key *key = sensitive_data.host_keys[i];
if (key != NULL && key->type == type)
return key;
}
return NULL;
}

Key *
get_hostkey_by_index(int ind)
{
if (ind < 0 || ind >= options.num_host_key_files)
return (NULL);
return (sensitive_data.host_keys[ind]);
}

int
get_hostkey_index(Key *key)
{
int i;

for (i = 0; i < options.num_host_key_files; i++) {
if (key == sensitive_data.host_keys[i])
return (i);
}
return (-1);
}

/*
* 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() % 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, SSLeay_version(SSLEAY_VERSION));
fprintf(stderr,
"usage: sshd [-46Ddeiqt] [-b bits] [-f config_file] [-g login_grace_time]\n"
" [-h host_key_file] [-k key_gen_time] [-o option] [-p port] [-u len]\n"
);
exit(1);
}

static void
send_rexec_state(int fd, Buffer *conf)
{
Buffer m;

debug3("%s: entering fd = %d config len %d", __func__, fd,
buffer_len(conf));

/*
* Protocol from reexec master to child:
* string configuration
* u_int ephemeral_key_follows
* bignum e (only if ephemeral_key_follows == 1)
* bignum n "
* bignum d "
* bignum iqmp "
* bignum p "
* bignum q "
* string rngseed (only if OpenSSL is not self-seeded)
*/
buffer_init(&m);
buffer_put_cstring(&m, buffer_ptr(conf));

if (sensitive_data.server_key != NULL &&
sensitive_data.server_key->type == KEY_RSA1) {
buffer_put_int(&m, 1);
buffer_put_bignum(&m, sensitive_data.server_key->rsa->e);
buffer_put_bignum(&m, sensitive_data.server_key->rsa->n);
buffer_put_bignum(&m, sensitive_data.server_key->rsa->d);
buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp);
buffer_put_bignum(&m, sensitive_data.server_key->rsa->p);
buffer_put_bignum(&m, sensitive_data.server_key->rsa->q);
} else
buffer_put_int(&m, 0);

#ifndef OPENSSL_PRNG_ONLY
rexec_send_rng_seed(&m);
#endif

if (ssh_msg_send(fd, 0, &m) == -1)
fatal("%s: ssh_msg_send failed", __func__);

buffer_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 + 1);
xfree(cp);

if (buffer_get_int(&m)) {
if (sensitive_data.server_key != NULL)
key_free(sensitive_data.server_key);
sensitive_data.server_key = key_new_private(KEY_RSA1);
buffer_get_bignum(&m, sensitive_data.server_key->rsa->e);
buffer_get_bignum(&m, sensitive_data.server_key->rsa->n);
buffer_get_bignum(&m, sensitive_data.server_key->rsa->d);
buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp);
buffer_get_bignum(&m, sensitive_data.server_key->rsa->p);
buffer_get_bignum(&m, sensitive_data.server_key->rsa->q);
rsa_generate_additional_parameters(
sensitive_data.server_key->rsa);
}

#ifndef OPENSSL_PRNG_ONLY
rexec_recv_rng_seed(&m);
#endif

buffer_free(&m);

debug3("%s: done", __func__);
}

/*
* Main program for the daemon.
*/
int
main(int ac, char **av)
{
extern char *optarg;
extern int optind;
int opt, j, i, fdsetsz, on = 1;
int sock_in = -1, sock_out = -1, newsock = -1;
pid_t pid;
socklen_t fromlen;
fd_set *fdset;
struct sockaddr_storage from;
const char *remote_ip;
int remote_port;
FILE *f;
struct addrinfo *ai;
char ntop[NI_MAXHOST], strport[NI_MAXSERV];
char *line;
int listen_sock, maxfd;
int startup_p[2] = { -1 , -1 }, config_s[2] = { -1 , -1 };
int startups = 0;
Key *key;
Authctxt *authctxt;
int ret, key_used = 0;
Buffer cfg;

#ifdef HAVE_SECUREWARE
(void)set_auth_parameters(ac, av);
#endif
__progname = ssh_get_progname(av[0]);
init_rng();

/* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
saved_argc = ac;
rexec_argc = ac;
saved_argv = xmalloc(sizeof(*saved_argv) * (ac + 1));
for (i = 0; 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, "f:p:b:k:h:g:u:o:dDeiqrtQR46")) != -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 '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':
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':
options.server_key_bits = atoi(optarg);
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':
if ((options.key_regeneration_time = convtime(optarg)) == -1) {
fprintf(stderr, "Invalid key regeneration interval.\n");
exit(1);
}
break;
case 'h':
if (options.num_host_key_files >= MAX_HOSTKEYS) {
fprintf(stderr, "too many host keys.\n");
exit(1);
}
options.host_key_files[options.num_host_key_files++] = optarg;
break;
case 't':
test_flag = 1;
break;
case 'u':
utmp_len = atoi(optarg);
if (utmp_len > MAXHOSTNAMELEN) {
fprintf(stderr, "Invalid utmp length.\n");
exit(1);
}
break;
case 'o':
line = xstrdup(optarg);
if (process_server_config_line(&options, line,
"command-line", 0) != 0)
exit(1);
xfree(line);
break;
case '?':
default:
usage();
break;
}
}
if (rexeced_flag || inetd_flag)
rexec_flag = 0;
if (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);

SSLeay_add_all_algorithms();

/*
* 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)
unsetenv("KRB5CCNAME");

#ifdef _UNICOS
/* Cray can define user privs drop all privs now!
* Not needed on PRIV_SU systems!
*/
drop_cray_privs();
#endif

sensitive_data.server_key = NULL;
sensitive_data.ssh1_host_key = NULL;
sensitive_data.have_ssh1_key = 0;
sensitive_data.have_ssh2_key = 0;

/* Fetch our configuration */
buffer_init(&cfg);
if (rexeced_flag)
recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg);
else
load_server_config(config_file_name, &cfg);

parse_server_config(&options,
rexeced_flag ? "rexec" : config_file_name, &cfg);

if (!rexec_flag)
buffer_free(&cfg);

seed_rng();

/* Fill in default values for those options not explicitly set. */
fill_default_server_options(&options);

/* set default channel AF */
channel_set_af(options.address_family);

/* Check that there are no remaining arguments. */
if (optind < ac) {
fprintf(stderr, "Extra argument %s.\n", av[optind]);
exit(1);
}

debug("sshd version %.100s", SSH_RELEASE);

/* load private host keys */
sensitive_data.host_keys = xmalloc(options.num_host_key_files *
sizeof(Key *));
for (i = 0; i < options.num_host_key_files; i++)
sensitive_data.host_keys[i] = NULL;

for (i = 0; i < options.num_host_key_files; i++) {
key = key_load_private(options.host_key_files[i], "", NULL);
sensitive_data.host_keys[i] = key;
if (key == NULL) {
error("Could not load host key: %s",
options.host_key_files[i]);
sensitive_data.host_keys[i] = NULL;
continue;
}
switch (key->type) {
case KEY_RSA1:
sensitive_data.ssh1_host_key = key;
sensitive_data.have_ssh1_key = 1;
break;
case KEY_RSA:
case KEY_DSA:
sensitive_data.have_ssh2_key = 1;
break;
}
debug("private host key: #%d type %d %s", i, key->type,
key_type(key));
}
if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
logit("Disabling protocol version 1. Could not load host key");
options.protocol &= ~SSH_PROTO_1;
}
if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
logit("Disabling protocol version 2. Could not load host key");
options.protocol &= ~SSH_PROTO_2;
}
if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
logit("sshd: no hostkeys available -- exiting.");
exit(1);
}

/* Check certain values for sanity. */
if (options.protocol & SSH_PROTO_1) {
if (options.server_key_bits < 512 ||
options.server_key_bits > 32768) {
fprintf(stderr, "Bad server key size.\n");
exit(1);
}
/*
* Check that server and host key lengths differ sufficiently. This
* is necessary to make double encryption work with rsaref. Oh, I
* hate software patents. I dont know if this can go? Niels
*/
if (options.server_key_bits >
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
SSH_KEY_BITS_RESERVED && options.server_key_bits <
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
SSH_KEY_BITS_RESERVED) {
options.server_key_bits =
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
SSH_KEY_BITS_RESERVED;
debug("Forcing server key to %d bits to make it differ from host key.",
options.server_key_bits);
}
}

if (use_privsep) {
struct passwd *pw;
struct stat st;

if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
fatal("Privilege separation user %s does not exist",
SSH_PRIVSEP_USER);
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);
}

/* 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) {
rexec_argv = xmalloc(sizeof(char *) * (rexec_argc + 2));
for (i = 0; i < 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;
}

/* 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, and not started from inetd, disconnect
* from the controlling terminal, and fork. The original process
* exits.
*/
if (!(debug_flag || inetd_flag || no_daemon_flag)) {
#ifdef TIOCNOTTY
int fd;
#endif /* TIOCNOTTY */
if (daemon(0, 0) < 0)
fatal("daemon() failed: %.200s", strerror(errno));

/* Disconnect from the controlling tty. */
#ifdef TIOCNOTTY
fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
if (fd >= 0) {
(void) ioctl(fd, TIOCNOTTY, NULL);
close(fd);
}
#endif /* TIOCNOTTY */
}
/* Reinitialize the log (because of the fork above). */
log_init(__progname, options.log_level, options.log_facility, log_stderr);

/* Initialize the random number generator. */
arc4random_stir();

/* Chdir to the root directory so that the current disk can be
unmounted if desired. */
chdir("/");

/* ignore SIGPIPE */
signal(SIGPIPE, SIG_IGN);

/* Start listening for a socket, unless started from inetd. */
if (inetd_flag) {
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 (fd > STDOUT_FILENO)
close(fd);
}
debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
if ((options.protocol & SSH_PROTO_1) &&
sensitive_data.server_key == NULL)
generate_ephemeral_server_key();
} else {
for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
continue;
if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen,
ntop, sizeof(ntop), strport, sizeof(strport),
NI_NUMERICHOST|NI_NUMERICSERV)) != 0) {
error("getnameinfo failed: %.100s",
(ret != EAI_SYSTEM) ? gai_strerror(ret) :
strerror(errno));
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;
}
/*
* Set socket options.
* Allow local port reuse in TIME_WAIT.
*/
if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
&on, sizeof(on)) == -1)
error("setsockopt SO_REUSEADDR: %s", strerror(errno));

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) {
if (!ai->ai_next)
error("Bind to port %s on %s failed: %.200s.",
strport, ntop, strerror(errno));
close(listen_sock);
continue;
}
/* Create/expand listen_socks as needed */
if(num_listen_socks >= listen_socks_len) {
int *old_listen_socks = listen_socks;
/* Start at 16 and then double as needed */
int new_listen_socks_len = listen_socks_len == 0 ? 16 : (listen_socks_len << 1);
listen_socks = realloc(listen_socks, new_listen_socks_len * sizeof(int));
if(listen_socks == NULL) {
free(old_listen_socks);
old_listen_socks = NULL;
listen_socks_len = 0;
fatal("realloc listen_socks: %s", strerror(errno));
} else {
listen_socks_len = new_listen_socks_len;
}
}

listen_socks[num_listen_socks] = listen_sock;
num_listen_socks++;

/* Start listening on the port. */
logit("Server listening on %s port %s.", ntop, strport);
if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0)
fatal("listen: %.100s", strerror(errno));

}
freeaddrinfo(options.listen_addrs);

if (!num_listen_socks)
fatal("Cannot bind any address.");

if (options.protocol & SSH_PROTO_1)
generate_ephemeral_server_key();

/*
* Arrange to restart on SIGHUP. The handler needs
* listen_sock.
*/
signal(SIGHUP, sighup_handler);

signal(SIGTERM, sigterm_handler);
signal(SIGQUIT, sigterm_handler);

/* Arrange SIGCHLD to be caught. */
signal(SIGCHLD, main_sigchld_handler);

/* Write out the pid file after the sigterm handler is setup */
if (!debug_flag) {
/*
* Record our pid in /var/run/sshd.pid to make it
* easier to kill the correct sshd. We don't want to
* do this before the bind above because the bind will
* fail if there already is a daemon, and this will
* overwrite any old pid in the file.
*/
f = fopen(options.pid_file, "wb");
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);
}
}

/* setup fd set for listen */
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 = xmalloc(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();
if (fdset != NULL)
xfree(fdset);
fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
fdset = (fd_set *)xmalloc(fdsetsz);
memset(fdset, 0, fdsetsz);

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();
unlink(options.pid_file);
exit(255);
}
if (key_used && key_do_regen) {
generate_ephemeral_server_key();
key_used = 0;
key_do_regen = 0;
}
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)
error("accept: %.100s", strerror(errno));
continue;
}
if (unset_nonblock(newsock) == -1) {
close(newsock);
continue;
}
if (drop_connection(startups) == 1) {
debug("drop connection #%d", startups);
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;
} else {
/*
* Normal production daemon. Fork, and have
* the child process the connection. The
* parent continues 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 break out of the loop to handle
* the connection.
*/
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. */
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]);
}

/* Mark that the key has been used (it was "given" to the child). */
if ((options.protocol & SSH_PROTO_1) &&
key_used == 0) {
/* Schedule server key regeneration alarm. */
signal(SIGALRM, key_regeneration_alarm);
alarm(options.key_regeneration_time);
key_used = 1;
}

arc4random_stir();

/* Close the new socket (the child is now taking care of it). */
close(newsock);
}
/* child process check (or debug mode) */
if (num_listen_socks < 0)
break;
}
}

/* 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
dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD);

dup2(config_s[1], REEXEC_CONFIG_PASS_FD);
close(config_s[1]);
if (startup_pipe != -1)
close(startup_pipe);

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 */
startup_pipe = REEXEC_STARTUP_PIPE_FD;
close(config_s[1]);
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]);
}

/*
* 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();

/* 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 = get_remote_port()) < 0) {
debug("get_remote_port failed");
cleanup_exit(255);
}

/*
* We use get_canonical_hostname with usedns = 0 instead of
* get_remote_ipaddr here so IP options will be checked.
*/
remote_ip = get_canonical_hostname(0);

#ifdef SSH_AUDIT_EVENTS
audit_connection_from(remote_ip, remote_port);
#endif
#ifdef LIBWRAP
/* Check whether logins are denied from this host. */
if (packet_connection_is_on_socket()) {
struct request_info req;

request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
fromhost(&req);

if (!hosts_access(&req)) {
debug("Connection refused by tcp wrapper");
refuse(&req);
/* NOTREACHED */
fatal("libwrap refuse returns");
}
}
#endif /* LIBWRAP */

/* Log the connection. */
verbose("Connection from %.500s port %d", remote_ip, remote_port);

/*
* 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(sock_in, sock_out);

packet_set_nonblocking();

/* allocate authentication context */
authctxt = xmalloc(sizeof(*authctxt));
memset(authctxt, 0, 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);

if (use_privsep)
if (privsep_preauth(authctxt) == 1)
goto authenticated;

/* perform the key exchange */
/* authenticate user and start session */
if (compat20) {
do_ssh2_kex();
do_authentication2(authctxt);
} else {
do_ssh1_kex();
do_authentication(authctxt);
}
/*
* If we use privilege separation, the unprivileged child transfers
* the current keystate and exits
*/
if (use_privsep) {
mm_send_keystate(pmonitor);
exit(0);
}

authenticated:
/*
* Cancel the alarm we set to limit the time taken for
* authentication.
*/
alarm(0);
signal(SIGALRM, SIG_DFL);
if (startup_pipe != -1) {
close(startup_pipe);
startup_pipe = -1;
}

#ifdef SSH_AUDIT_EVENTS
audit_event(SSH_AUTH_SUCCESS);
#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 */
if (!compat20)
destroy_sensitive_data();
}

/* Start session. */
do_authenticated(authctxt);

/* The connection has been terminated. */
verbose("Closing connection to %.100s", remote_ip);

#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);
}

/*
* Decrypt session_key_int using our private server key and private host key
* (key with larger modulus first).
*/
int
ssh1_session_key(BIGNUM *session_key_int)
{
int rsafail = 0;

if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
/* Server key has bigger modulus. */
if (BN_num_bits(sensitive_data.server_key->rsa->n) <
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
get_remote_ipaddr(),
BN_num_bits(sensitive_data.server_key->rsa->n),
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
SSH_KEY_BITS_RESERVED);
}
if (rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.server_key->rsa) <= 0)
rsafail++;
if (rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.ssh1_host_key->rsa) <= 0)
rsafail++;
} else {
/* Host key has bigger modulus (or they are equal). */
if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
get_remote_ipaddr(),
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
BN_num_bits(sensitive_data.server_key->rsa->n),
SSH_KEY_BITS_RESERVED);
}
if (rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.ssh1_host_key->rsa) < 0)
rsafail++;
if (rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.server_key->rsa) < 0)
rsafail++;
}
return (rsafail);
}
/*
* SSH1 key exchange
*/
static void
do_ssh1_kex(void)
{
int i, len;
int rsafail = 0;
BIGNUM *session_key_int;
u_char session_key[SSH_SESSION_KEY_LENGTH];
u_char cookie[8];
u_int cipher_type, auth_mask, protocol_flags;
u_int32_t rnd = 0;

/*
* Generate check bytes that the client must send back in the user
* packet in order for it to be accepted; this is used to defy ip
* spoofing attacks. Note that this only works against somebody
* doing IP spoofing from a remote machine; any machine on the local
* network can still see outgoing packets and catch the random
* cookie. This only affects rhosts authentication, and this is one
* of the reasons why it is inherently insecure.
*/
for (i = 0; i < 8; i++) {
if (i % 4 == 0)
rnd = arc4random();
cookie[i] = rnd & 0xff;
rnd >>= 8;
}

/*
* Send our public key. We include in the packet 64 bits of random
* data that must be matched in the reply in order to prevent IP
* spoofing.
*/
packet_start(SSH_SMSG_PUBLIC_KEY);
for (i = 0; i < 8; i++)
packet_put_char(cookie[i]);

/* Store our public server RSA key. */
packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
packet_put_bignum(sensitive_data.server_key->rsa->e);
packet_put_bignum(sensitive_data.server_key->rsa->n);

/* Store our public host RSA key. */
packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);

/* Put protocol flags. */
packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);

/* Declare which ciphers we support. */
packet_put_int(cipher_mask_ssh1(0));

/* Declare supported authentication types. */
auth_mask = 0;
if (options.rhosts_rsa_authentication)
auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
if (options.rsa_authentication)
auth_mask |= 1 << SSH_AUTH_RSA;
if (options.challenge_response_authentication == 1)
auth_mask |= 1 << SSH_AUTH_TIS;
if (options.password_authentication)
auth_mask |= 1 << SSH_AUTH_PASSWORD;
packet_put_int(auth_mask);

/* Send the packet and wait for it to be sent. */
packet_send();
packet_write_wait();

debug("Sent %d bit server key and %d bit host key.",
BN_num_bits(sensitive_data.server_key->rsa->n),
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));

/* Read clients reply (cipher type and session key). */
packet_read_expect(SSH_CMSG_SESSION_KEY);

/* Get cipher type and check whether we accept this. */
cipher_type = packet_get_char();

if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
packet_disconnect("Warning: client selects unsupported cipher.");

/* Get check bytes from the packet. These must match those we
sent earlier with the public key packet. */
for (i = 0; i < 8; i++)
if (cookie[i] != packet_get_char())
packet_disconnect("IP Spoofing check bytes do not match.");

debug("Encryption type: %.200s", cipher_name(cipher_type));

/* Get the encrypted integer. */
if ((session_key_int = BN_new()) == NULL)
fatal("do_ssh1_kex: BN_new failed");
packet_get_bignum(session_key_int);

protocol_flags = packet_get_int();
packet_set_protocol_flags(protocol_flags);
packet_check_eom();

/* Decrypt session_key_int using host/server keys */
rsafail = PRIVSEP(ssh1_session_key(session_key_int));

/*
* Extract session key from the decrypted integer. The key is in the
* least significant 256 bits of the integer; the first byte of the
* key is in the highest bits.
*/
if (!rsafail) {
BN_mask_bits(session_key_int, sizeof(session_key) * 8);
len = BN_num_bytes(session_key_int);
if (len < 0 || (u_int)len > sizeof(session_key)) {
error("do_connection: bad session key len from %s: "
"session_key_int %d > sizeof(session_key) %lu",
get_remote_ipaddr(), len, (u_long)sizeof(session_key));
rsafail++;
} else {
memset(session_key, 0, sizeof(session_key));
BN_bn2bin(session_key_int,
session_key + sizeof(session_key) - len);

derive_ssh1_session_id(
sensitive_data.ssh1_host_key->rsa->n,
sensitive_data.server_key->rsa->n,
cookie, session_id);
/*
* Xor the first 16 bytes of the session key with the
* session id.
*/
for (i = 0; i < 16; i++)
session_key[i] ^= session_id[i];
}
}
if (rsafail) {
int bytes = BN_num_bytes(session_key_int);
u_char *buf = xmalloc(bytes);
MD5_CTX md;

logit("do_connection: generating a fake encryption key");
BN_bn2bin(session_key_int, buf);
MD5_Init(&md);
MD5_Update(&md, buf, bytes);
MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
MD5_Final(session_key, &md);
MD5_Init(&md);
MD5_Update(&md, session_key, 16);
MD5_Update(&md, buf, bytes);
MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
MD5_Final(session_key + 16, &md);
memset(buf, 0, bytes);
xfree(buf);
for (i = 0; i < 16; i++)
session_id[i] = session_key[i] ^ session_key[i + 16];
}
/* Destroy the private and public keys. No longer. */
destroy_sensitive_data();

if (use_privsep)
mm_ssh1_session_id(session_id);

/* Destroy the decrypted integer. It is no longer needed. */
BN_clear_free(session_key_int);

/* Set the session key. From this on all communications will be encrypted. */
packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);

/* Destroy our copy of the session key. It is no longer needed. */
memset(session_key, 0, sizeof(session_key));

debug("Received session key; encryption turned on.");

/* Send an acknowledgment packet. Note that this packet is sent encrypted. */
packet_start(SSH_SMSG_SUCCESS);
packet_send();
packet_write_wait();
}

/*
* SSH2 key exchange: diffie-hellman-group1-sha1
*/
static void
do_ssh2_kex(void)
{
Kex *kex;

if (options.ciphers != NULL) {
myproposal[PROPOSAL_ENC_ALGS_CTOS] =
myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
}
myproposal[PROPOSAL_ENC_ALGS_CTOS] =
compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
myproposal[PROPOSAL_ENC_ALGS_STOC] =
compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);

if (options.macs != NULL) {
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";
} else if (options.compression == COMP_DELAYED) {
myproposal[PROPOSAL_COMP_ALGS_CTOS] =
myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,***@openssh.com";
}

myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();

/* start key exchange */
kex = kex_setup(myproposal);
kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
kex->server = 1;
kex->client_version_string=client_version_string;
kex->server_version_string=server_version_string;
kex->load_host_key=&get_hostkey_by_type;
kex->host_key_index=&get_hostkey_index;

xxx_kex = kex;

dispatch_run(DISPATCH_BLOCK, &kex->done, kex);

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_authctxt)
do_cleanup(the_authctxt);
#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);
}

--------------030803010504000608020900
Content-Type: text/x-patch;
name="sshd.c.diff"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
filename="sshd.c.diff"

148,149c148,149
< #define MAX_LISTEN_SOCKS 16
< int listen_socks[MAX_LISTEN_SOCKS];
---

int *listen_socks = NULL;
int listen_socks_len = 0;

1281,1283d1280
< if (num_listen_socks >= MAX_LISTEN_SOCKS)
< fatal("Too many listen sockets. "
< "Enlarge MAX_LISTEN_SOCKS");
1321a1319,1334

/* Create/expand listen_socks as needed */
if(num_listen_socks >= listen_socks_len) {
int *old_listen_socks = listen_socks;
/* Start at 16 and then double as needed */
int new_listen_socks_len = listen_socks_len == 0 ? 16 : (listen_socks_len << 1);
listen_socks = realloc(listen_socks, new_listen_socks_len * sizeof(int));
if(listen_socks == NULL) {
free(old_listen_socks);
old_listen_socks = NULL;
listen_socks_len = 0;
fatal("realloc listen_socks: %s", strerror(errno));
} else {
listen_socks_len = new_listen_socks_len;
}
}

--------------030803010504000608020900
Content-Type: text/plain;
name="sshd.c.orig"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
filename="sshd.c.orig"

/*
* Author: Tatu Ylonen <***@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <***@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"
RCSID("$OpenBSD: sshd.c,v 1.318 2005/12/24 02:27:41 djm Exp $");

#include <openssl/dh.h>
#include <openssl/bn.h>
#include <openssl/md5.h>
#include <openssl/rand.h>
#ifdef HAVE_SECUREWARE
#include <sys/security.h>
#include <prot.h>
#endif

#include "ssh.h"
#include "ssh1.h"
#include "ssh2.h"
#include "xmalloc.h"
#include "rsa.h"
#include "sshpty.h"
#include "packet.h"
#include "log.h"
#include "servconf.h"
#include "uidswap.h"
#include "compat.h"
#include "buffer.h"
#include "bufaux.h"
#include "cipher.h"
#include "kex.h"
#include "key.h"
#include "dh.h"
#include "myproposal.h"
#include "authfile.h"
#include "pathnames.h"
#include "atomicio.h"
#include "canohost.h"
#include "auth.h"
#include "misc.h"
#include "msg.h"
#include "dispatch.h"
#include "channels.h"
#include "session.h"
#include "monitor_mm.h"
#include "monitor.h"
#include "monitor_wrap.h"
#include "monitor_fdpass.h"

#ifdef LIBWRAP
#include <tcpd.h>
#include <syslog.h>
int allow_severity = LOG_INFO;
int deny_severity = LOG_WARNING;
#endif /* LIBWRAP */

#ifndef O_NOCTTY
#define O_NOCTTY 0
#endif

/* 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;

/* Flag indicating that the daemon should only test the configuration and keys. */
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;

/* for rekeying XXX fixme */
Kex *xxx_kex;

/*
* 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 {
Key *server_key; /* ephemeral server key */
Key *ssh1_host_key; /* ssh1 host key */
Key **host_keys; /* all private host keys */
int have_ssh1_key;
int have_ssh2_key;
u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
} sensitive_data;

/*
* Flag indicating whether the RSA server key needs to be regenerated.
* Is set in the SIGALRM handler and cleared when the key is regenerated.
*/
static volatile sig_atomic_t key_do_regen = 0;

/* 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 = MAXHOSTNAMELEN;

/* 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;
struct monitor *pmonitor = NULL;

/* global authentication context */
Authctxt *the_authctxt = NULL;

/* message to be displayed after login */
Buffer loginmsg;

/* Prototypes for various functions defined later in this file. */
void destroy_sensitive_data(void);
void demote_sensitive_data(void);

static void do_ssh1_kex(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).
*/
static void
sighup_handler(int sig)
{
int save_errno = errno;

received_sighup = 1;
signal(SIGHUP, sighup_handler);
errno = save_errno;
}

/*
* Called from the main program after receiving SIGHUP.
* Restarts the server.
*/
static void
sighup_restart(void)
{
logit("Received SIGHUP; restarting.");
close_listen_socks();
close_startup_pipes();
execv(saved_argv[0], saved_argv);
logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
strerror(errno));
exit(1);
}

/*
* Generic signal handler for terminating signals in the master daemon.
*/
static void
sigterm_handler(int sig)
{
received_sigterm = sig;
}

/*
* SIGCHLD handler. This is called whenever a child dies. This will then
* reap any zombies left by exited children.
*/
static void
main_sigchld_handler(int sig)
{
int save_errno = errno;
pid_t pid;
int status;

while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
(pid < 0 && errno == EINTR))
;

signal(SIGCHLD, main_sigchld_handler);
errno = save_errno;
}

/*
* Signal handler for the alarm after the login grace period has expired.
*/
static void
grace_alarm_handler(int sig)
{
/* XXX no idea how fix this signal handler */

if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0)
kill(pmonitor->m_pid, SIGALRM);

/* Log error and exit. */
fatal("Timeout before authentication for %s", get_remote_ipaddr());
}

/*
* Signal handler for the key regeneration alarm. Note that this
* alarm only occurs in the daemon waiting for connections, and it does not
* do anything with the private key or random state before forking.
* Thus there should be no concurrency control/asynchronous execution
* problems.
*/
static void
generate_ephemeral_server_key(void)
{
u_int32_t rnd = 0;
int i;

verbose("Generating %s%d bit RSA key.",
sensitive_data.server_key ? "new " : "", options.server_key_bits);
if (sensitive_data.server_key != NULL)
key_free(sensitive_data.server_key);
sensitive_data.server_key = key_generate(KEY_RSA1,
options.server_key_bits);
verbose("RSA key generation complete.");

for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
if (i % 4 == 0)
rnd = arc4random();
sensitive_data.ssh1_cookie[i] = rnd & 0xff;
rnd >>= 8;
}
arc4random_stir();
}

static void
key_regeneration_alarm(int sig)
{
int save_errno = errno;

signal(SIGALRM, SIG_DFL);
errno = save_errno;
key_do_regen = 1;
}

static void
sshd_exchange_identification(int sock_in, int sock_out)
{
u_int i;
int mismatch;
int remote_major, remote_minor;
int major, 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. */

if ((options.protocol & SSH_PROTO_1) &&
(options.protocol & SSH_PROTO_2)) {
major = PROTOCOL_MAJOR_1;
minor = 99;
} else if (options.protocol & SSH_PROTO_2) {
major = PROTOCOL_MAJOR_2;
minor = PROTOCOL_MINOR_2;
} else {
major = PROTOCOL_MAJOR_1;
minor = PROTOCOL_MINOR_1;
}
snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
server_version_string = xstrdup(buf);

/* 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", get_remote_ipaddr());
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",
get_remote_ipaddr());
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));
close(sock_in);
close(sock_out);
logit("Bad protocol version identification '%.100s' from %s",
client_version_string, get_remote_ipaddr());
cleanup_exit(255);
}
debug("Client protocol version %d.%d; client software version %.100s",
remote_major, remote_minor, remote_version);

compat_datafellows(remote_version);

if (datafellows & SSH_BUG_PROBE) {
logit("probed from %s with %s. Don't panic.",
get_remote_ipaddr(), client_version_string);
cleanup_exit(255);
}

if (datafellows & SSH_BUG_SCANNER) {
logit("scanned from %s with %s. Don't panic.",
get_remote_ipaddr(), client_version_string);
cleanup_exit(255);
}

mismatch = 0;
switch (remote_major) {
case 1:
if (remote_minor == 99) {
if (options.protocol & SSH_PROTO_2)
enable_compat20();
else
mismatch = 1;
break;
}
if (!(options.protocol & SSH_PROTO_1)) {
mismatch = 1;
break;
}
if (remote_minor < 3) {
packet_disconnect("Your ssh version is too old and "
"is no longer supported. Please install a newer version.");
} else if (remote_minor == 3) {
/* note that this disables agent-forwarding */
enable_compat13();
}
break;
case 2:
if (options.protocol & SSH_PROTO_2) {
enable_compat20();
break;
}
/* FALLTHROUGH */
default:
mismatch = 1;
break;
}
chop(server_version_string);
debug("Local version string %.200s", server_version_string);

if (mismatch) {
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: %.200s vs. %.200s",
get_remote_ipaddr(),
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)
{
int i;

if (sensitive_data.server_key) {
key_free(sensitive_data.server_key);
sensitive_data.server_key = NULL;
}
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;
}
}
sensitive_data.ssh1_host_key = NULL;
memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
}

/* Demote private to public keys for network child */
void
demote_sensitive_data(void)
{
Key *tmp;
int i;

if (sensitive_data.server_key) {
tmp = key_demote(sensitive_data.server_key);
key_free(sensitive_data.server_key);
sensitive_data.server_key = tmp;
}

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;
if (tmp->type == KEY_RSA1)
sensitive_data.ssh1_host_key = tmp;
}
}

/* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
}

static void
privsep_preauth_child(void)
{
u_int32_t rnd[256];
gid_t gidset[1];
struct passwd *pw;
int i;

/* Enable challenge-response authentication for privilege separation */
privsep_challenge_enable();

for (i = 0; i < 256; i++)
rnd[i] = arc4random();
RAND_seed(rnd, sizeof(rnd));

/* Demote the private keys to public keys. */
demote_sensitive_data();

if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
fatal("Privilege separation user %s does not exist",
SSH_PRIVSEP_USER);
memset(pw->pw_passwd, 0, strlen(pw->pw_passwd));
endpwent();

/* 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)pw->pw_uid,
(u_int)pw->pw_gid);
#if 0
/* XXX not ready, too heavy after chroot */
do_setusercontext(pw);
#else
gidset[0] = pw->pw_gid;
if (setgroups(1, gidset) < 0)
fatal("setgroups: %.100s", strerror(errno));
permanently_set_uid(pw);
#endif
}

static int
privsep_preauth(Authctxt *authctxt)
{
int status;
pid_t pid;

/* 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 = &xxx_kex;

pid = fork();
if (pid == -1) {
fatal("fork of unprivileged child failed");
} else if (pid != 0) {
debug2("Network child is on pid %ld", (long)pid);

close(pmonitor->m_recvfd);
pmonitor->m_pid = pid;
monitor_child_preauth(authctxt, pmonitor);
close(pmonitor->m_sendfd);

/* Sync memory */
monitor_sync(pmonitor);

/* Wait for the child's exit status */
while (waitpid(pid, &status, 0) < 0)
if (errno != EINTR)
break;
return (1);
} else {
/* child */

close(pmonitor->m_sendfd);

/* Demote the child */
if (getuid() == 0 || geteuid() == 0)
privsep_preauth_child();
setproctitle("%s", "[net]");
}
return (0);
}

static void
privsep_postauth(Authctxt *authctxt)
{
#ifdef DISABLE_FD_PASSING
if (1) {
#else
if (authctxt->pw->pw_uid == 0 || options.use_login) {
#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) {
debug2("User child is on pid %ld", (long)pmonitor->m_pid);
close(pmonitor->m_recvfd);
buffer_clear(&loginmsg);
monitor_child_postauth(pmonitor);

/* NEVERREACHED */
exit(0);
}

close(pmonitor->m_sendfd);

/* Demote the private keys to public keys. */
demote_sensitive_data();

/* 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;
int i;

buffer_init(&b);
for (i = 0; i < options.num_host_key_files; i++) {
Key *key = sensitive_data.host_keys[i];
if (key == NULL)
continue;
switch (key->type) {
case KEY_RSA:
case KEY_DSA:
if (buffer_len(&b) > 0)
buffer_append(&b, ",", 1);
p = key_ssh_name(key);
buffer_append(&b, p, strlen(p));
break;
}
}
buffer_append(&b, "\0", 1);
ret = xstrdup(buffer_ptr(&b));
buffer_free(&b);
debug("list_hostkey_types: %s", ret);
return ret;
}

Key *
get_hostkey_by_type(int type)
{
int i;

for (i = 0; i < options.num_host_key_files; i++) {
Key *key = sensitive_data.host_keys[i];
if (key != NULL && key->type == type)
return key;
}
return NULL;
}

Key *
get_hostkey_by_index(int ind)
{
if (ind < 0 || ind >= options.num_host_key_files)
return (NULL);
return (sensitive_data.host_keys[ind]);
}

int
get_hostkey_index(Key *key)
{
int i;

for (i = 0; i < options.num_host_key_files; i++) {
if (key == sensitive_data.host_keys[i])
return (i);
}
return (-1);
}

/*
* 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() % 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, SSLeay_version(SSLEAY_VERSION));
fprintf(stderr,
"usage: sshd [-46Ddeiqt] [-b bits] [-f config_file] [-g login_grace_time]\n"
" [-h host_key_file] [-k key_gen_time] [-o option] [-p port] [-u len]\n"
);
exit(1);
}

static void
send_rexec_state(int fd, Buffer *conf)
{
Buffer m;

debug3("%s: entering fd = %d config len %d", __func__, fd,
buffer_len(conf));

/*
* Protocol from reexec master to child:
* string configuration
* u_int ephemeral_key_follows
* bignum e (only if ephemeral_key_follows == 1)
* bignum n "
* bignum d "
* bignum iqmp "
* bignum p "
* bignum q "
* string rngseed (only if OpenSSL is not self-seeded)
*/
buffer_init(&m);
buffer_put_cstring(&m, buffer_ptr(conf));

if (sensitive_data.server_key != NULL &&
sensitive_data.server_key->type == KEY_RSA1) {
buffer_put_int(&m, 1);
buffer_put_bignum(&m, sensitive_data.server_key->rsa->e);
buffer_put_bignum(&m, sensitive_data.server_key->rsa->n);
buffer_put_bignum(&m, sensitive_data.server_key->rsa->d);
buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp);
buffer_put_bignum(&m, sensitive_data.server_key->rsa->p);
buffer_put_bignum(&m, sensitive_data.server_key->rsa->q);
} else
buffer_put_int(&m, 0);

#ifndef OPENSSL_PRNG_ONLY
rexec_send_rng_seed(&m);
#endif

if (ssh_msg_send(fd, 0, &m) == -1)
fatal("%s: ssh_msg_send failed", __func__);

buffer_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 + 1);
xfree(cp);

if (buffer_get_int(&m)) {
if (sensitive_data.server_key != NULL)
key_free(sensitive_data.server_key);
sensitive_data.server_key = key_new_private(KEY_RSA1);
buffer_get_bignum(&m, sensitive_data.server_key->rsa->e);
buffer_get_bignum(&m, sensitive_data.server_key->rsa->n);
buffer_get_bignum(&m, sensitive_data.server_key->rsa->d);
buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp);
buffer_get_bignum(&m, sensitive_data.server_key->rsa->p);
buffer_get_bignum(&m, sensitive_data.server_key->rsa->q);
rsa_generate_additional_parameters(
sensitive_data.server_key->rsa);
}

#ifndef OPENSSL_PRNG_ONLY
rexec_recv_rng_seed(&m);
#endif

buffer_free(&m);

debug3("%s: done", __func__);
}

/*
* Main program for the daemon.
*/
int
main(int ac, char **av)
{
extern char *optarg;
extern int optind;
int opt, j, i, fdsetsz, on = 1;
int sock_in = -1, sock_out = -1, newsock = -1;
pid_t pid;
socklen_t fromlen;
fd_set *fdset;
struct sockaddr_storage from;
const char *remote_ip;
int remote_port;
FILE *f;
struct addrinfo *ai;
char ntop[NI_MAXHOST], strport[NI_MAXSERV];
char *line;
int listen_sock, maxfd;
int startup_p[2] = { -1 , -1 }, config_s[2] = { -1 , -1 };
int startups = 0;
Key *key;
Authctxt *authctxt;
int ret, key_used = 0;
Buffer cfg;

#ifdef HAVE_SECUREWARE
(void)set_auth_parameters(ac, av);
#endif
__progname = ssh_get_progname(av[0]);
init_rng();

/* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
saved_argc = ac;
rexec_argc = ac;
saved_argv = xmalloc(sizeof(*saved_argv) * (ac + 1));
for (i = 0; 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, "f:p:b:k:h:g:u:o:dDeiqrtQR46")) != -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 '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':
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':
options.server_key_bits = atoi(optarg);
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':
if ((options.key_regeneration_time = convtime(optarg)) == -1) {
fprintf(stderr, "Invalid key regeneration interval.\n");
exit(1);
}
break;
case 'h':
if (options.num_host_key_files >= MAX_HOSTKEYS) {
fprintf(stderr, "too many host keys.\n");
exit(1);
}
options.host_key_files[options.num_host_key_files++] = optarg;
break;
case 't':
test_flag = 1;
break;
case 'u':
utmp_len = atoi(optarg);
if (utmp_len > MAXHOSTNAMELEN) {
fprintf(stderr, "Invalid utmp length.\n");
exit(1);
}
break;
case 'o':
line = xstrdup(optarg);
if (process_server_config_line(&options, line,
"command-line", 0) != 0)
exit(1);
xfree(line);
break;
case '?':
default:
usage();
break;
}
}
if (rexeced_flag || inetd_flag)
rexec_flag = 0;
if (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);

SSLeay_add_all_algorithms();

/*
* 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)
unsetenv("KRB5CCNAME");

#ifdef _UNICOS
/* Cray can define user privs drop all privs now!
* Not needed on PRIV_SU systems!
*/
drop_cray_privs();
#endif

sensitive_data.server_key = NULL;
sensitive_data.ssh1_host_key = NULL;
sensitive_data.have_ssh1_key = 0;
sensitive_data.have_ssh2_key = 0;

/* Fetch our configuration */
buffer_init(&cfg);
if (rexeced_flag)
recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg);
else
load_server_config(config_file_name, &cfg);

parse_server_config(&options,
rexeced_flag ? "rexec" : config_file_name, &cfg);

if (!rexec_flag)
buffer_free(&cfg);

seed_rng();

/* Fill in default values for those options not explicitly set. */
fill_default_server_options(&options);

/* set default channel AF */
channel_set_af(options.address_family);

/* Check that there are no remaining arguments. */
if (optind < ac) {
fprintf(stderr, "Extra argument %s.\n", av[optind]);
exit(1);
}

debug("sshd version %.100s", SSH_RELEASE);

/* load private host keys */
sensitive_data.host_keys = xmalloc(options.num_host_key_files *
sizeof(Key *));
for (i = 0; i < options.num_host_key_files; i++)
sensitive_data.host_keys[i] = NULL;

for (i = 0; i < options.num_host_key_files; i++) {
key = key_load_private(options.host_key_files[i], "", NULL);
sensitive_data.host_keys[i] = key;
if (key == NULL) {
error("Could not load host key: %s",
options.host_key_files[i]);
sensitive_data.host_keys[i] = NULL;
continue;
}
switch (key->type) {
case KEY_RSA1:
sensitive_data.ssh1_host_key = key;
sensitive_data.have_ssh1_key = 1;
break;
case KEY_RSA:
case KEY_DSA:
sensitive_data.have_ssh2_key = 1;
break;
}
debug("private host key: #%d type %d %s", i, key->type,
key_type(key));
}
if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
logit("Disabling protocol version 1. Could not load host key");
options.protocol &= ~SSH_PROTO_1;
}
if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
logit("Disabling protocol version 2. Could not load host key");
options.protocol &= ~SSH_PROTO_2;
}
if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
logit("sshd: no hostkeys available -- exiting.");
exit(1);
}

/* Check certain values for sanity. */
if (options.protocol & SSH_PROTO_1) {
if (options.server_key_bits < 512 ||
options.server_key_bits > 32768) {
fprintf(stderr, "Bad server key size.\n");
exit(1);
}
/*
* Check that server and host key lengths differ sufficiently. This
* is necessary to make double encryption work with rsaref. Oh, I
* hate software patents. I dont know if this can go? Niels
*/
if (options.server_key_bits >
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
SSH_KEY_BITS_RESERVED && options.server_key_bits <
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
SSH_KEY_BITS_RESERVED) {
options.server_key_bits =
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
SSH_KEY_BITS_RESERVED;
debug("Forcing server key to %d bits to make it differ from host key.",
options.server_key_bits);
}
}

if (use_privsep) {
struct passwd *pw;
struct stat st;

if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
fatal("Privilege separation user %s does not exist",
SSH_PRIVSEP_USER);
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);
}

/* 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) {
rexec_argv = xmalloc(sizeof(char *) * (rexec_argc + 2));
for (i = 0; i < 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;
}

/* 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, and not started from inetd, disconnect
* from the controlling terminal, and fork. The original process
* exits.
*/
if (!(debug_flag || inetd_flag || no_daemon_flag)) {
#ifdef TIOCNOTTY
int fd;
#endif /* TIOCNOTTY */
if (daemon(0, 0) < 0)
fatal("daemon() failed: %.200s", strerror(errno));

/* Disconnect from the controlling tty. */
#ifdef TIOCNOTTY
fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
if (fd >= 0) {
(void) ioctl(fd, TIOCNOTTY, NULL);
close(fd);
}
#endif /* TIOCNOTTY */
}
/* Reinitialize the log (because of the fork above). */
log_init(__progname, options.log_level, options.log_facility, log_stderr);

/* Initialize the random number generator. */
arc4random_stir();

/* Chdir to the root directory so that the current disk can be
unmounted if desired. */
chdir("/");

/* ignore SIGPIPE */
signal(SIGPIPE, SIG_IGN);

/* Start listening for a socket, unless started from inetd. */
if (inetd_flag) {
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 (fd > STDOUT_FILENO)
close(fd);
}
debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
if ((options.protocol & SSH_PROTO_1) &&
sensitive_data.server_key == NULL)
generate_ephemeral_server_key();
} else {
for (ai = options.listen_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",
(ret != EAI_SYSTEM) ? gai_strerror(ret) :
strerror(errno));
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;
}
/*
* Set socket options.
* Allow local port reuse in TIME_WAIT.
*/
if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
&on, sizeof(on)) == -1)
error("setsockopt SO_REUSEADDR: %s", strerror(errno));

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) {
if (!ai->ai_next)
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. */
logit("Server listening on %s port %s.", ntop, strport);
if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0)
fatal("listen: %.100s", strerror(errno));

}
freeaddrinfo(options.listen_addrs);

if (!num_listen_socks)
fatal("Cannot bind any address.");

if (options.protocol & SSH_PROTO_1)
generate_ephemeral_server_key();

/*
* Arrange to restart on SIGHUP. The handler needs
* listen_sock.
*/
signal(SIGHUP, sighup_handler);

signal(SIGTERM, sigterm_handler);
signal(SIGQUIT, sigterm_handler);

/* Arrange SIGCHLD to be caught. */
signal(SIGCHLD, main_sigchld_handler);

/* Write out the pid file after the sigterm handler is setup */
if (!debug_flag) {
/*
* Record our pid in /var/run/sshd.pid to make it
* easier to kill the correct sshd. We don't want to
* do this before the bind above because the bind will
* fail if there already is a daemon, and this will
* overwrite any old pid in the file.
*/
f = fopen(options.pid_file, "wb");
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);
}
}

/* setup fd set for listen */
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 = xmalloc(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();
if (fdset != NULL)
xfree(fdset);
fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
fdset = (fd_set *)xmalloc(fdsetsz);
memset(fdset, 0, fdsetsz);

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();
unlink(options.pid_file);
exit(255);
}
if (key_used && key_do_regen) {
generate_ephemeral_server_key();
key_used = 0;
key_do_regen = 0;
}
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)
error("accept: %.100s", strerror(errno));
continue;
}
if (unset_nonblock(newsock) == -1) {
close(newsock);
continue;
}
if (drop_connection(startups) == 1) {
debug("drop connection #%d", startups);
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;
} else {
/*
* Normal production daemon. Fork, and have
* the child process the connection. The
* parent continues 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 break out of the loop to handle
* the connection.
*/
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. */
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]);
}

/* Mark that the key has been used (it was "given" to the child). */
if ((options.protocol & SSH_PROTO_1) &&
key_used == 0) {
/* Schedule server key regeneration alarm. */
signal(SIGALRM, key_regeneration_alarm);
alarm(options.key_regeneration_time);
key_used = 1;
}

arc4random_stir();

/* Close the new socket (the child is now taking care of it). */
close(newsock);
}
/* child process check (or debug mode) */
if (num_listen_socks < 0)
break;
}
}

/* 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
dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD);

dup2(config_s[1], REEXEC_CONFIG_PASS_FD);
close(config_s[1]);
if (startup_pipe != -1)
close(startup_pipe);

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 */
startup_pipe = REEXEC_STARTUP_PIPE_FD;
close(config_s[1]);
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]);
}

/*
* 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();

/* 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 = get_remote_port()) < 0) {
debug("get_remote_port failed");
cleanup_exit(255);
}

/*
* We use get_canonical_hostname with usedns = 0 instead of
* get_remote_ipaddr here so IP options will be checked.
*/
remote_ip = get_canonical_hostname(0);

#ifdef SSH_AUDIT_EVENTS
audit_connection_from(remote_ip, remote_port);
#endif
#ifdef LIBWRAP
/* Check whether logins are denied from this host. */
if (packet_connection_is_on_socket()) {
struct request_info req;

request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
fromhost(&req);

if (!hosts_access(&req)) {
debug("Connection refused by tcp wrapper");
refuse(&req);
/* NOTREACHED */
fatal("libwrap refuse returns");
}
}
#endif /* LIBWRAP */

/* Log the connection. */
verbose("Connection from %.500s port %d", remote_ip, remote_port);

/*
* 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(sock_in, sock_out);

packet_set_nonblocking();

/* allocate authentication context */
authctxt = xmalloc(sizeof(*authctxt));
memset(authctxt, 0, 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);

if (use_privsep)
if (privsep_preauth(authctxt) == 1)
goto authenticated;

/* perform the key exchange */
/* authenticate user and start session */
if (compat20) {
do_ssh2_kex();
do_authentication2(authctxt);
} else {
do_ssh1_kex();
do_authentication(authctxt);
}
/*
* If we use privilege separation, the unprivileged child transfers
* the current keystate and exits
*/
if (use_privsep) {
mm_send_keystate(pmonitor);
exit(0);
}

authenticated:
/*
* Cancel the alarm we set to limit the time taken for
* authentication.
*/
alarm(0);
signal(SIGALRM, SIG_DFL);
if (startup_pipe != -1) {
close(startup_pipe);
startup_pipe = -1;
}

#ifdef SSH_AUDIT_EVENTS
audit_event(SSH_AUTH_SUCCESS);
#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 */
if (!compat20)
destroy_sensitive_data();
}

/* Start session. */
do_authenticated(authctxt);

/* The connection has been terminated. */
verbose("Closing connection to %.100s", remote_ip);

#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);
}

/*
* Decrypt session_key_int using our private server key and private host key
* (key with larger modulus first).
*/
int
ssh1_session_key(BIGNUM *session_key_int)
{
int rsafail = 0;

if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
/* Server key has bigger modulus. */
if (BN_num_bits(sensitive_data.server_key->rsa->n) <
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
get_remote_ipaddr(),
BN_num_bits(sensitive_data.server_key->rsa->n),
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
SSH_KEY_BITS_RESERVED);
}
if (rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.server_key->rsa) <= 0)
rsafail++;
if (rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.ssh1_host_key->rsa) <= 0)
rsafail++;
} else {
/* Host key has bigger modulus (or they are equal). */
if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
get_remote_ipaddr(),
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
BN_num_bits(sensitive_data.server_key->rsa->n),
SSH_KEY_BITS_RESERVED);
}
if (rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.ssh1_host_key->rsa) < 0)
rsafail++;
if (rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.server_key->rsa) < 0)
rsafail++;
}
return (rsafail);
}
/*
* SSH1 key exchange
*/
static void
do_ssh1_kex(void)
{
int i, len;
int rsafail = 0;
BIGNUM *session_key_int;
u_char session_key[SSH_SESSION_KEY_LENGTH];
u_char cookie[8];
u_int cipher_type, auth_mask, protocol_flags;
u_int32_t rnd = 0;

/*
* Generate check bytes that the client must send back in the user
* packet in order for it to be accepted; this is used to defy ip
* spoofing attacks. Note that this only works against somebody
* doing IP spoofing from a remote machine; any machine on the local
* network can still see outgoing packets and catch the random
* cookie. This only affects rhosts authentication, and this is one
* of the reasons why it is inherently insecure.
*/
for (i = 0; i < 8; i++) {
if (i % 4 == 0)
rnd = arc4random();
cookie[i] = rnd & 0xff;
rnd >>= 8;
}

/*
* Send our public key. We include in the packet 64 bits of random
* data that must be matched in the reply in order to prevent IP
* spoofing.
*/
packet_start(SSH_SMSG_PUBLIC_KEY);
for (i = 0; i < 8; i++)
packet_put_char(cookie[i]);

/* Store our public server RSA key. */
packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
packet_put_bignum(sensitive_data.server_key->rsa->e);
packet_put_bignum(sensitive_data.server_key->rsa->n);

/* Store our public host RSA key. */
packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);

/* Put protocol flags. */
packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);

/* Declare which ciphers we support. */
packet_put_int(cipher_mask_ssh1(0));

/* Declare supported authentication types. */
auth_mask = 0;
if (options.rhosts_rsa_authentication)
auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
if (options.rsa_authentication)
auth_mask |= 1 << SSH_AUTH_RSA;
if (options.challenge_response_authentication == 1)
auth_mask |= 1 << SSH_AUTH_TIS;
if (options.password_authentication)
auth_mask |= 1 << SSH_AUTH_PASSWORD;
packet_put_int(auth_mask);

/* Send the packet and wait for it to be sent. */
packet_send();
packet_write_wait();

debug("Sent %d bit server key and %d bit host key.",
BN_num_bits(sensitive_data.server_key->rsa->n),
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));

/* Read clients reply (cipher type and session key). */
packet_read_expect(SSH_CMSG_SESSION_KEY);

/* Get cipher type and check whether we accept this. */
cipher_type = packet_get_char();

if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
packet_disconnect("Warning: client selects unsupported cipher.");

/* Get check bytes from the packet. These must match those we
sent earlier with the public key packet. */
for (i = 0; i < 8; i++)
if (cookie[i] != packet_get_char())
packet_disconnect("IP Spoofing check bytes do not match.");

debug("Encryption type: %.200s", cipher_name(cipher_type));

/* Get the encrypted integer. */
if ((session_key_int = BN_new()) == NULL)
fatal("do_ssh1_kex: BN_new failed");
packet_get_bignum(session_key_int);

protocol_flags = packet_get_int();
packet_set_protocol_flags(protocol_flags);
packet_check_eom();

/* Decrypt session_key_int using host/server keys */
rsafail = PRIVSEP(ssh1_session_key(session_key_int));

/*
* Extract session key from the decrypted integer. The key is in the
* least significant 256 bits of the integer; the first byte of the
* key is in the highest bits.
*/
if (!rsafail) {
BN_mask_bits(session_key_int, sizeof(session_key) * 8);
len = BN_num_bytes(session_key_int);
if (len < 0 || (u_int)len > sizeof(session_key)) {
error("do_connection: bad session key len from %s: "
"session_key_int %d > sizeof(session_key) %lu",
get_remote_ipaddr(), len, (u_long)sizeof(session_key));
rsafail++;
} else {
memset(session_key, 0, sizeof(session_key));
BN_bn2bin(session_key_int,
session_key + sizeof(session_key) - len);

derive_ssh1_session_id(
sensitive_data.ssh1_host_key->rsa->n,
sensitive_data.server_key->rsa->n,
cookie, session_id);
/*
* Xor the first 16 bytes of the session key with the
* session id.
*/
for (i = 0; i < 16; i++)
session_key[i] ^= session_id[i];
}
}
if (rsafail) {
int bytes = BN_num_bytes(session_key_int);
u_char *buf = xmalloc(bytes);
MD5_CTX md;

logit("do_connection: generating a fake encryption key");
BN_bn2bin(session_key_int, buf);
MD5_Init(&md);
MD5_Update(&md, buf, bytes);
MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
MD5_Final(session_key, &md);
MD5_Init(&md);
MD5_Update(&md, session_key, 16);
MD5_Update(&md, buf, bytes);
MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
MD5_Final(session_key + 16, &md);
memset(buf, 0, bytes);
xfree(buf);
for (i = 0; i < 16; i++)
session_id[i] = session_key[i] ^ session_key[i + 16];
}
/* Destroy the private and public keys. No longer. */
destroy_sensitive_data();

if (use_privsep)
mm_ssh1_session_id(session_id);

/* Destroy the decrypted integer. It is no longer needed. */
BN_clear_free(session_key_int);

/* Set the session key. From this on all communications will be encrypted. */
packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);

/* Destroy our copy of the session key. It is no longer needed. */
memset(session_key, 0, sizeof(session_key));

debug("Received session key; encryption turned on.");

/* Send an acknowledgment packet. Note that this packet is sent encrypted. */
packet_start(SSH_SMSG_SUCCESS);
packet_send();
packet_write_wait();
}

/*
* SSH2 key exchange: diffie-hellman-group1-sha1
*/
static void
do_ssh2_kex(void)
{
Kex *kex;

if (options.ciphers != NULL) {
myproposal[PROPOSAL_ENC_ALGS_CTOS] =
myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
}
myproposal[PROPOSAL_ENC_ALGS_CTOS] =
compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
myproposal[PROPOSAL_ENC_ALGS_STOC] =
compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);

if (options.macs != NULL) {
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";
} else if (options.compression == COMP_DELAYED) {
myproposal[PROPOSAL_COMP_ALGS_CTOS] =
myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,***@openssh.com";
}

myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();

/* start key exchange */
kex = kex_setup(myproposal);
kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
kex->server = 1;
kex->client_version_string=client_version_string;
kex->server_version_string=server_version_string;
kex->load_host_key=&get_hostkey_by_type;
kex->host_key_index=&get_hostkey_index;

xxx_kex = kex;

dispatch_run(DISPATCH_BLOCK, &kex->done, kex);

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_authctxt)
do_cleanup(the_authctxt);
#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);
}

--------------030803010504000608020900
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

_______________________________________________
openssh-unix-dev mailing list
openssh-unix-***@mindrot.org
https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev

--------------030803010504000608020900--

[Peter Teoh]

Post by Dan Armstrong
OpenSSH developers,
I have removed the fixed, arbitrary limit on the number of
ListenAddress allowed by using realloc to dynamically expand
listen_socks as needed. This completely removes MAX_LISTEN_SOCKS from
the source. I made this change on the version of OpenSSH shipped with
CentOS 5.2, version 4.3p2. Please see the attached .c file and .diff
file. Please add these changes to OpenSSH to save people from having
to predetermine their workload before compilation. It can also save
some people some grief - I've been unable to login to a server because
of this one.

Sorry if I may ask the risks of this option - will it not lead to any
potential scenario of Denial of Service, if some how the number of
ListenAddress can be arbitrarily increase without limit, and thus
leading to realloc() allocating large amount of memory?

Thanks.

[Peter Stuge]

Hi,

I made this change on the version of OpenSSH shipped with CentOS
5.2, version 4.3p2.

In the future please make changes against the latest version of the
source code which is available via anonymous CVS. Your change is not
too big, so hopefully it doesn't require very much work to forward
port onto the the latest version.

Please see the attached .c file and .diff file.

When sending patches in the future please send only the diff output,
and most groups prefer the unified diff format (diff -U) because it
is a lot easier to read.

148,149c148,149
< #define MAX_LISTEN_SOCKS 16
< int listen_socks[MAX_LISTEN_SOCKS];
---

Post by Dan Armstrong
int *listen_socks = NULL;
int listen_socks_len = 0;

1281,1283d1280
< if (num_listen_socks >= MAX_LISTEN_SOCKS)
< fatal("Too many listen sockets. "
< "Enlarge MAX_LISTEN_SOCKS");
1321a1319,1334

Post by Dan Armstrong
/* Create/expand listen_socks as needed */
if(num_listen_socks >= listen_socks_len) {
int *old_listen_socks = listen_socks;
/* Start at 16 and then double as needed */
int new_listen_socks_len = listen_socks_len == 0 ? 16 : (listen_socks_len << 1);
listen_socks = realloc(listen_socks, new_listen_socks_len * sizeof(int));
if(listen_socks == NULL) {
free(old_listen_socks);
old_listen_socks = NULL;
listen_socks_len = 0;
fatal("realloc listen_socks: %s", strerror(errno));
} else {
listen_socks_len = new_listen_socks_len;
}
}

I'm not sure.. I would probably just increase MAX_LISTEN_SOCKS.

Alternatively perhaps the server you couldn't log in to could set
something up with a wildcard listen and a few firewall rules?

Sorry if I may ask the risks of this option - will it not lead to
any potential scenario of Denial of Service, if some how the number
of ListenAddress can be arbitrarily increase without limit, and
thus leading to realloc() allocating large amount of memory?

It's not a problem. This code runs once at server startup. Whoever is
running sshd could use it to allocate large amounts of memory, but
they could just as easily build another program which does the same
thing. The protection against this situation is to configure limits,
maybe using ulimit.


//Peter

[Ben Lindstrom]

Post by Peter Teoh

Post by Dan Armstrong
OpenSSH developers,
I have removed the fixed, arbitrary limit on the number of
ListenAddress allowed by using realloc to dynamically expand
listen_socks as needed. This completely removes MAX_LISTEN_SOCKS
from
the source. I made this change on the version of OpenSSH shipped
with
CentOS 5.2, version 4.3p2. Please see the attached .c file and .diff
file. Please add these changes to OpenSSH to save people from having
to predetermine their workload before compilation. It can also save
some people some grief - I've been unable to login to a server
because
of this one.

Sorry if I may ask the risks of this option - will it not lead to any
potential scenario of Denial of Service, if some how the number of
ListenAddress can be arbitrarily increase without limit, and thus
leading to realloc() allocating large amount of memory?

I can't see how this would be a "DoS", since ListenAddress must be set
by the server on launch. One can flood a single port just as easy as
they can flood multiple ports.

I'm still trying to figure out why one would want OpenSSH listening on
more than 15 ports/address combination. Is it really worth the added
complexity?

- Ben

[Dan Armstrong]

Ben,

I fully agree that there is no DoS aspect to this.

As for the patch, it is very simple. It doesn't change the
functionality of sshd in any way. It just takes a fixed-size array and
replaces it with a dynamically-growable version. The use of
predetermined-size arrays, as done in C code everywhere, is sometimes in
appropriate and gets in the way of using the software. I have been
submitting patches similar to this to various open source projects as
they affect me.

We have the need for more than 15 binds. In our virtual hosting
environment, users can select exactly which services they want enabled
on a per-IP basis. Also, we don't bind to 0.0.0.0 because one of our
fail-over techniques is to run multiple servers in different chroot
environments. Thus, we have different sshd instances running, one per
chroot environment, each binding to the specific set of IP addresses
associated with the chroot environment.

I guess my #1 concern is that once you hit the limit, your sshd is
dead. You can't login. You can't get in there to fix the config file
to get your sshd back online. If you guys don't like the use of realloc
to handle any number of ListenAddress, please at least bind to the first
MAX_LISTEN_SOCKS and syslog/stderr warnings about the extras, instead of
leaving a dead sshd. I can submit a patch for this behavior, if you like.

Please add the patch. It simply allows the software to do what it is
told without the risk of a surprise dead sshd.


Thank you,

Dan Armstrong
AO Industries, Inc.
***@aoindustries.com
Work: [phone]
Cell: [phone]

Post by Ben Lindstrom

Post by Peter Teoh

Post by Dan Armstrong
OpenSSH developers,
I have removed the fixed, arbitrary limit on the number of
ListenAddress allowed by using realloc to dynamically expand
listen_socks as needed. This completely removes MAX_LISTEN_SOCKS from
the source. I made this change on the version of OpenSSH shipped with
CentOS 5.2, version 4.3p2. Please see the attached .c file and .diff
file. Please add these changes to OpenSSH to save people from having
to predetermine their workload before compilation. It can also save
some people some grief - I've been unable to login to a server because
of this one.

Sorry if I may ask the risks of this option - will it not lead to any
potential scenario of Denial of Service, if some how the number of
ListenAddress can be arbitrarily increase without limit, and thus
leading to realloc() allocating large amount of memory?

I can't see how this would be a "DoS", since ListenAddress must be set
by the server on launch. One can flood a single port just as easy as
they can flood multiple ports.
I'm still trying to figure out why one would want OpenSSH listening on
more than 15 ports/address combination. Is it really worth the added
complexity?
- Ben