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openssh-portable/sshd.c

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/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
* This program is the ssh daemon. It listens for connections from clients,
* and performs authentication, executes use commands or shell, and forwards
* information to/from the application to the user client over an encrypted
* connection. This can also handle forwarding of X11, TCP/IP, and
* authentication agent connections.
*
* As far as I am concerned, the code I have written for this software
* can be used freely for any purpose. Any derived versions of this
* software must be clearly marked as such, and if the derived work is
* incompatible with the protocol description in the RFC file, it must be
* called by a name other than "ssh" or "Secure Shell".
*
* SSH2 implementation:
* Privilege Separation:
*
* Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved.
* Copyright (c) 2002 Niels Provos. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
RCSID("$OpenBSD: sshd.c,v 1.302 2004/08/28 01:01:48 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;
/*
* Flag indicating whether IPv4 or IPv6. This can be set on the command line.
* Default value is AF_UNSPEC means both IPv4 and IPv6.
*/
int IPv4or6 = AF_UNSPEC;
/*
* 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)
{
int i, 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 */
monitor_apply_keystate(pmonitor);
use_privsep = 0;
return;
}
/* Authentication complete */
alarm(0);
if (startup_pipe != -1) {
close(startup_pipe);
startup_pipe = -1;
}
/* 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);
/* It is safe now to apply the key state */
monitor_apply_keystate(pmonitor);
}
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)
{
double 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 /= (double) (options.max_startups - options.max_startups_begin);
p += options.max_startups_rate;
p /= 100.0;
r = arc4random() / (double) UINT_MAX;
debug("drop_connection: p %g, r %g", p, r);
return (r < p) ? 1 : 0;
}
static void
usage(void)
{
fprintf(stderr, "%s, %s\n",
SSH_VERSION, 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 "
*/
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);
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);
}
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));
/* 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':
IPv4or6 = AF_INET;
break;
case '6':
IPv4or6 = 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();
channel_set_af(IPv4or6);
/*
* 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);
#ifdef _AIX
/*
* Unset KRB5CCNAME, otherwise the user's session may inherit it from
* root's environment
*/
unsetenv("KRB5CCNAME");
#endif /* _AIX */
#ifdef _UNICOS
/* Cray can define user privs drop all privs now!
* Not needed on PRIV_SU systems!
*/
drop_cray_privs();
#endif
seed_rng();
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);
/* Fill in default values for those options not explicitly set. */
fill_default_server_options(&options);
/* 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_VERSION);
/* 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)
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 (getnameinfo(ai->ai_addr, ai->ai_addrlen,
ntop, sizeof(ntop), strport, sizeof(strport),
NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
error("getnameinfo failed");
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);
/* Set SO_KEEPALIVE if requested. */
if (options.tcp_keep_alive &&
setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on,
sizeof(on)) < 0)
error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
/*
* Register our connection. This turns encryption off because we do
* not have a key.
*/
packet_set_connection(sock_in, sock_out);
remote_port = get_remote_port();
remote_ip = get_remote_ipaddr();
#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();
/* prepare buffers to collect authentication messages */
buffer_init(&loginmsg);
/* allocate authentication context */
authctxt = xmalloc(sizeof(*authctxt));
memset(authctxt, 0, sizeof(*authctxt));
/* XXX global for cleanup, access from other modules */
the_authctxt = authctxt;
if (use_privsep)
if (privsep_preauth(authctxt) == 1)
goto authenticated;
/* prepare buffer to collect messages to display to user after login */
buffer_init(&loginmsg);
/* 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:
/*
* 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 */
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 || 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) {
myproposal[PROPOSAL_COMP_ALGS_CTOS] =
myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
}
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);
_exit(i);
}
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