OpenSolaris_b135/cmd/ssh/sshd/sshd.c
/*
* 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.
*/
/*
* Copyright 2010 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#include "includes.h"
RCSID("$OpenBSD: sshd.c,v 1.260 2002/09/27 10:42:09 mickey Exp $");
#include <openssl/dh.h>
#include <openssl/bn.h>
#include <openssl/md5.h>
#include <openssl/rand.h>
#include "ssh.h"
#include "ssh1.h"
#include "ssh2.h"
#include "xmalloc.h"
#include "rsa.h"
#include "sshpty.h"
#include "packet.h"
#include "mpaux.h"
#include "log.h"
#include "servconf.h"
#include "uidswap.h"
#include "compat.h"
#include "buffer.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 "dispatch.h"
#include "channels.h"
#include "session.h"
#include "g11n.h"
#include "sshlogin.h"
#include "xlist.h"
#include "engine.h"
#ifdef HAVE_BSM
#include "bsmaudit.h"
#endif /* HAVE_BSM */
#ifdef ALTPRIVSEP
#include "altprivsep.h"
#endif /* ALTPRIVSEP */
#ifdef HAVE_SOLARIS_CONTRACTS
#include <sys/ctfs.h>
#include <sys/contract.h>
#include <sys/contract/process.h>
#include <libcontract.h>
#endif /* HAVE_SOLARIS_CONTRACTS */
#ifdef GSSAPI
#include "ssh-gss.h"
#endif /* GSSAPI */
#ifdef LIBWRAP
#include <tcpd.h>
#include <syslog.h>
#ifndef lint
int allow_severity = LOG_INFO;
int deny_severity = LOG_WARNING;
#endif /* lint */
#endif /* LIBWRAP */
#ifndef O_NOCTTY
#define O_NOCTTY 0
#endif
#ifdef HAVE___PROGNAME
extern char *__progname;
#else
char *__progname;
#endif
/* Server configuration options. */
ServerOptions options;
/* Name of the server configuration file. */
static 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.
*/
#ifdef IPV4_DEFAULT
int IPv4or6 = AF_INET;
#else
int IPv4or6 = AF_UNSPEC;
#endif
/*
* 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. */
static int test_flag = 0;
/* Flag indicating that the daemon is being started from inetd. */
static int inetd_flag = 0;
/* Flag indicating that sshd should not detach and become a daemon. */
static int no_daemon_flag = 0;
/* debug goes to stderr unless inetd_flag is set */
int log_stderr = 0;
/* Saved arguments to main(). */
static char **saved_argv;
static int saved_argc;
/*
* The sockets that the server is listening; this is used in the SIGHUP
* signal handler.
*/
#define MAX_LISTEN_SOCKS 16
static int listen_socks[MAX_LISTEN_SOCKS];
static int num_listen_socks = 0;
/*
* the client's version string, passed by sshd2 in compat mode. if != NULL,
* sshd will skip the version-number exchange
*/
static char *client_version_string = NULL;
static 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.
*/
static 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;
int session_id2_len = 0;
/* record remote hostname or ip */
u_int utmp_len = MAXHOSTNAMELEN;
/* options.max_startup sized array of fd ints */
static int *startup_pipes = NULL;
static int startup_pipe = -1; /* in child */
/* sshd_config buffer */
Buffer cfg;
#ifdef GSSAPI
static gss_OID_set mechs = GSS_C_NULL_OID_SET;
#endif /* GSSAPI */
/* Prototypes for various functions defined later in this file. */
void destroy_sensitive_data(void);
static 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++)
(void) 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)
(void) 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;
(void) signal(SIGHUP, sighup_handler);
errno = save_errno;
}
/*
* Called from the main program after receiving SIGHUP.
* Restarts the server.
*/
static void
sighup_restart(void)
{
log("Received SIGHUP; restarting.");
close_listen_socks();
close_startup_pipes();
(void) execv(saved_argv[0], saved_argv);
log("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))
;
(void) signal(SIGCHLD, main_sigchld_handler);
errno = save_errno;
}
/*
* Signal handler for the alarm after the login grace period has expired. This
* is for the (soon-to-be) unprivileged child only. The monitor gets an event on
* the communication pipe and exits as well.
*/
static void
grace_alarm_handler(int sig)
{
/* Log error and exit. */
fatal("Timeout before authentication for %.200s", get_remote_ipaddr());
}
#ifdef HAVE_SOLARIS_CONTRACTS
static int contracts_fd = -1;
void
contracts_pre_fork()
{
const char *during = "opening process contract template";
/*
* Failure should not be treated as fatal on the theory that
* it's better to start with children in the same contract as
* the master listener than not at all.
*/
if (contracts_fd == -1) {
if ((contracts_fd = open64(CTFS_ROOT "/process/template",
O_RDWR)) == -1)
goto cleanup;
during = "setting sundry contract terms";
if ((errno = ct_pr_tmpl_set_param(contracts_fd, CT_PR_PGRPONLY)))
goto cleanup;
if ((errno = ct_tmpl_set_informative(contracts_fd, CT_PR_EV_HWERR)))
goto cleanup;
if ((errno = ct_pr_tmpl_set_fatal(contracts_fd, CT_PR_EV_HWERR)))
goto cleanup;
if ((errno = ct_tmpl_set_critical(contracts_fd, 0)))
goto cleanup;
}
during = "setting active template";
if ((errno = ct_tmpl_activate(contracts_fd)))
goto cleanup;
debug3("Set active contract");
return;
cleanup:
if (contracts_fd != -1)
(void) close(contracts_fd);
contracts_fd = -1;
if (errno)
debug2("Error while trying to set up active contract"
" template: %s while %s", strerror(errno), during);
}
void
contracts_post_fork_child()
{
/* Clear active template so fork() creates no new contracts. */
if (contracts_fd == -1)
return;
if ((errno = (ct_tmpl_clear(contracts_fd))))
debug2("Error while trying to clear active contract template"
" (child): %s", strerror(errno));
else
debug3("Cleared active contract template (child)");
(void) close(contracts_fd);
contracts_fd = -1;
}
void
contracts_post_fork_parent(int fork_succeeded)
{
char path[PATH_MAX];
int cfd, n;
ct_stathdl_t st;
ctid_t latest;
/* Clear active template, abandon latest contract. */
if (contracts_fd == -1)
return;
if ((errno = ct_tmpl_clear(contracts_fd)))
debug2("Error while clearing active contract template: %s",
strerror(errno));
else
debug3("Cleared active contract template (parent)");
if (!fork_succeeded)
return;
if ((cfd = open64(CTFS_ROOT "/process/latest", O_RDONLY)) == -1) {
debug2("Error while getting latest contract: %s",
strerror(errno));
return;
}
if ((errno = ct_status_read(cfd, CTD_COMMON, &st)) != 0) {
debug2("Error while getting latest contract ID: %s",
strerror(errno));
(void) close(cfd);
return;
}
latest = ct_status_get_id(st);
ct_status_free(st);
(void) close(cfd);
n = snprintf(path, PATH_MAX, CTFS_ROOT "/all/%ld/ctl", latest);
if (n >= PATH_MAX) {
debug2("Error while opening the latest contract ctl file: %s",
strerror(ENAMETOOLONG));
return;
}
if ((cfd = open64(path, O_WRONLY)) == -1) {
debug2("Error while opening the latest contract ctl file: %s",
strerror(errno));
return;
}
if ((errno = ct_ctl_abandon(cfd)))
debug2("Error while abandoning latest contract: %s",
strerror(errno));
else
debug3("Abandoned latest contract");
(void) close(cfd);
}
#endif /* HAVE_SOLARIS_CONTRACTS */
/*
* 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;
(void) 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;
}
(void) snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
server_version_string = xstrdup(buf);
if (client_version_string == NULL) {
/* Send our protocol version identification. */
if (atomicio(write, sock_out, server_version_string,
strlen(server_version_string))
!= strlen(server_version_string)) {
log("Could not write ident string to %s", get_remote_ipaddr());
fatal_cleanup();
}
/* Read other sides version identification. */
(void) memset(buf, 0, sizeof(buf));
for (i = 0; i < sizeof(buf) - 1; i++) {
if (atomicio(read, sock_in, &buf[i], 1) != 1) {
log("Did not receive identification string from %s",
get_remote_ipaddr());
fatal_cleanup();
}
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(write, sock_out, s, strlen(s));
(void) close(sock_in);
(void) close(sock_out);
log("Bad protocol version identification '%.100s' from %s",
client_version_string, get_remote_ipaddr());
fatal_cleanup();
}
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) {
log("probed from %s with %s. Don't panic.",
get_remote_ipaddr(), client_version_string);
fatal_cleanup();
}
if (datafellows & SSH_BUG_SCANNER) {
log("scanned from %s with %s. Don't panic.",
get_remote_ipaddr(), client_version_string);
fatal_cleanup();
}
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(write, sock_out, s, strlen(s));
(void) close(sock_in);
(void) close(sock_out);
log("Protocol major versions differ for %s: %.200s vs. %.200s",
get_remote_ipaddr(),
server_version_string, client_version_string);
fatal_cleanup();
}
}
/* 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;
(void) memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
}
/* Demote private to public keys for network child */
static 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 char *
list_hostkey_types(void)
{
Buffer b;
char *p;
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);
p = xstrdup(buffer_ptr(&b));
buffer_free(&b);
debug("list_hostkey_types: %s", p);
return p;
}
#ifdef lint
static
#endif /* lint */
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;
}
#ifdef lint
static
#endif /* lint */
Key *
get_hostkey_by_index(int ind)
{
if (ind < 0 || ind >= options.num_host_key_files)
return (NULL);
return (sensitive_data.host_keys[ind]);
}
#ifdef lint
static
#endif /* lint */
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)
{
(void) fprintf(stderr, gettext("sshd version %s\n"), SSH_VERSION);
(void) fprintf(stderr,
gettext("Usage: %s [options]\n"
"Options:\n"
" -f file Configuration file (default %s)\n"
" -d Debugging mode (multiple -d means more "
"debugging)\n"
" -i Started from inetd\n"
" -D Do not fork into daemon mode\n"
" -t Only test configuration file and keys\n"
" -q Quiet (no logging)\n"
" -p port Listen on the specified port (default: 22)\n"
" -k seconds Regenerate server key every this many seconds "
"(default: 3600)\n"
" -g seconds Grace period for authentication (default: 600)\n"
" -b bits Size of server RSA key (default: 768 bits)\n"
" -h file File from which to read host key (default: %s)\n"
" -4 Use IPv4 only\n"
" -6 Use IPv6 only\n"
" -o option Process the option as if it was read from "
"a configuration file.\n"),
__progname, _PATH_SERVER_CONFIG_FILE, _PATH_HOST_KEY_FILE);
exit(1);
}
/*
* Main program for the daemon.
*/
int
main(int ac, char **av)
{
extern char *optarg;
extern int optind;
int opt, j, i, fdsetsz, sock_in = 0, sock_out = 0, newsock = -1, on = 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];
int listen_sock, maxfd;
int startup_p[2];
int startups = 0;
Authctxt *authctxt = NULL;
Key *key;
int ret, key_used = 0;
#ifdef HAVE_BSM
au_id_t auid = AU_NOAUDITID;
#endif /* HAVE_BSM */
int mpipe;
__progname = get_progname(av[0]);
(void) g11n_setlocale(LC_ALL, "");
init_rng();
/* Save argv. */
saved_argc = ac;
saved_argv = av;
/* 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:V:u:o:dDeiqtQ46")) != -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 (0 == debug_flag) {
debug_flag = 1;
options.log_level = SYSLOG_LEVEL_DEBUG1;
} else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
options.log_level++;
} else {
(void) fprintf(stderr,
gettext("Debug level too high.\n"));
exit(1);
}
break;
case 'D':
no_daemon_flag = 1;
break;
case 'e':
log_stderr = 1;
break;
case 'i':
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) {
(void) fprintf(stderr, gettext("too many ports.\n"));
exit(1);
}
options.ports[options.num_ports++] = a2port(optarg);
if (options.ports[options.num_ports-1] == 0) {
(void) fprintf(stderr, gettext("Bad port number.\n"));
exit(1);
}
break;
case 'g':
if ((options.login_grace_time = convtime(optarg)) == -1) {
(void) fprintf(stderr,
gettext("Invalid login grace time.\n"));
exit(1);
}
break;
case 'k':
if ((options.key_regeneration_time = convtime(optarg)) == -1) {
(void) fprintf(stderr,
gettext("Invalid key regeneration "
"interval.\n"));
exit(1);
}
break;
case 'h':
if (options.num_host_key_files >= MAX_HOSTKEYS) {
(void) fprintf(stderr,
gettext("too many host keys.\n"));
exit(1);
}
options.host_key_files[options.num_host_key_files++] = optarg;
break;
case 'V':
client_version_string = optarg;
/* only makes sense with inetd_flag, i.e. no listen() */
inetd_flag = 1;
break;
case 't':
test_flag = 1;
break;
case 'o':
if (process_server_config_line(&options, optarg,
"command-line", 0, NULL, NULL, NULL, NULL) != 0)
exit(1);
break;
case '?':
default:
usage();
break;
}
}
/*
* There is no need to use the PKCS#11 engine in the master SSH process.
*/
SSLeay_add_all_algorithms();
seed_rng();
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,
!inetd_flag);
#ifdef _UNICOS
/* Cray can define user privs drop all prives now!
* Not needed on PRIV_SU systems!
*/
drop_cray_privs();
#endif
/* Fetch our configuration */
buffer_init(&cfg);
load_server_config(config_file_name, &cfg);
parse_server_config(&options, config_file_name, &cfg, NULL, NULL, NULL);
/* Fill in default values for those options not explicitly set. */
fill_default_server_options(&options);
utmp_len = options.lookup_client_hostnames ? utmp_len : 0;
/* Check that there are no remaining arguments. */
if (optind < ac) {
(void) fprintf(stderr, gettext("Extra argument %s.\n"), av[optind]);
exit(1);
}
debug("sshd version %.100s", SSH_VERSION);
/* load private host keys */
if (options.num_host_key_files > 0)
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;
sensitive_data.server_key = NULL;
sensitive_data.ssh1_host_key = NULL;
sensitive_data.have_ssh1_key = 0;
sensitive_data.have_ssh2_key = 0;
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) {
log("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) {
#ifdef GSSAPI
if (options.gss_keyex)
ssh_gssapi_server_mechs(&mechs);
if (mechs == GSS_C_NULL_OID_SET) {
log("Disabling protocol version 2. Could not load host"
"key or GSS-API mechanisms");
options.protocol &= ~SSH_PROTO_2;
}
#else
log("Disabling protocol version 2. Could not load host key");
options.protocol &= ~SSH_PROTO_2;
#endif /* GSSAPI */
}
if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
log("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) {
(void) fprintf(stderr, gettext("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);
}
}
/* 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));
/* 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);
/*
* Solaris 9 and systems upgraded from it may have the Ciphers option
* explicitly set to "aes128-cbc,blowfish-cbc,3des-cbc" in the
* sshd_config. Since the default server cipher list completely changed
* since then we rather notify the administator on startup. We do this
* check after log_init() so that the message goes to syslogd and not to
* stderr (unless the server is in the debug mode). Note that since
* Solaris 10 we no longer ship sshd_config with explicit settings for
* Ciphers or MACs. Do not try to augment the cipher list here since
* that might end up in a very confusing situation.
*/
#define OLD_DEFAULT_CIPHERS_LIST "aes128-cbc,blowfish-cbc,3des-cbc"
if (options.ciphers != NULL &&
strcmp(options.ciphers, OLD_DEFAULT_CIPHERS_LIST) == 0) {
notice("Old default value \"%s\" for the \"Ciphers\" "
"option found in use. In general it is prudent to let "
"the server choose the defaults unless your environment "
"specifically needs an explicit setting. See "
"sshd_config(4) for more information.",
OLD_DEFAULT_CIPHERS_LIST);
}
#ifdef HAVE_BSM
(void) setauid(&auid);
#endif /* HAVE_BSM */
/*
* 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);
(void) 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. */
(void) chdir("/");
/* ignore SIGPIPE */
(void) signal(SIGPIPE, SIG_IGN);
/* Start listening for a socket, unless started from inetd. */
if (inetd_flag) {
int s1;
s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
(void) dup(s1);
sock_in = dup(0);
sock_out = dup(1);
startup_pipe = -1;
/* we need this later for setting audit context */
newsock = sock_in;
/*
* 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.
*/
debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
if (options.protocol & SSH_PROTO_1)
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, SOCK_STREAM, 0);
if (listen_sock < 0) {
/* kernel may not support ipv6 */
verbose("socket: %.100s", strerror(errno));
continue;
}
if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
error("listen_sock O_NONBLOCK: %s", strerror(errno));
(void) 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));
(void) close(listen_sock);
continue;
}
listen_socks[num_listen_socks] = listen_sock;
num_listen_socks++;
/* Start listening on the port. */
log("Server listening on %s port %s.", ntop, strport);
if (listen(listen_sock, 5) < 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.
*/
(void) signal(SIGHUP, sighup_handler);
(void) signal(SIGTERM, sigterm_handler);
(void) signal(SIGQUIT, sigterm_handler);
/* Arrange SIGCHLD to be caught. */
(void) 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) {
(void) fprintf(f, "%ld\n", (long) getpid());
(void) 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);
(void) 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) {
log("Received signal %d; terminating.",
(int) received_sigterm);
close_listen_socks();
(void) 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
*/
(void) 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 (fcntl(newsock, F_SETFL, 0) < 0) {
error("newsock del O_NONBLOCK: %s", strerror(errno));
(void) close(newsock);
continue;
}
if (drop_connection(startups) == 1) {
debug("drop connection #%d", startups);
(void) close(newsock);
continue;
}
if (pipe(startup_p) == -1) {
(void) close(newsock);
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;
startup_pipe = -1;
pid = getpid();
break;
} else {
/*
* Normal production daemon. Fork, and have
* the child process the connection. The
* parent continues listening.
*/
#ifdef HAVE_SOLARIS_CONTRACTS
/*
* Setup Solaris contract template so
* the child process is in a different
* process contract than the parent;
* prevents established connections from
* being killed when the sshd master
* listener service is stopped.
*/
contracts_pre_fork();
#endif /* HAVE_SOLARIS_CONTRACTS */
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.
*/
#ifdef HAVE_SOLARIS_CONTRACTS
contracts_post_fork_child();
#endif /* HAVE_SOLARIS_CONTRACTS */
xfree(fdset);
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);
break;
}
/* Parent. Stay in the loop. */
if (pid < 0)
error("fork: %.100s", strerror(errno));
else
debug("Forked child %ld.", (long)pid);
#ifdef HAVE_SOLARIS_CONTRACTS
contracts_post_fork_parent((pid > 0));
#endif /* HAVE_SOLARIS_CONTRACTS */
}
(void) close(startup_p[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. */
(void) signal(SIGALRM, key_regeneration_alarm);
(void) alarm(options.key_regeneration_time);
key_used = 1;
}
arc4random_stir();
/*
* Close the accepted socket since the child
* will now take care of the new connection.
*/
(void) close(newsock);
}
/* child process check (or debug mode) */
if (num_listen_socks < 0)
break;
}
}
/*
* This is the child processing a new connection, the SSH master process
* stays in the ( ; ; ) loop above.
*/
#ifdef HAVE_BSM
audit_sshd_settid(newsock);
#endif
/*
* 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 0
/* XXX: this breaks Solaris */
if (!debug_flag && !inetd_flag && setsid() < 0)
error("setsid: %.100s", strerror(errno));
#endif
/*
* 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.
*/
(void) alarm(0);
(void) signal(SIGALRM, SIG_DFL);
(void) signal(SIGHUP, SIG_DFL);
(void) signal(SIGTERM, SIG_DFL);
(void) signal(SIGQUIT, SIG_DFL);
(void) signal(SIGCHLD, SIG_DFL);
(void) signal(SIGINT, SIG_DFL);
/* Set keepalives if requested. */
if (options.keepalives &&
setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on,
sizeof(on)) < 0)
debug2("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. */
{
struct request_info req;
(void) 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);
sshd_exchange_identification(sock_in, sock_out);
/*
* Check that the connection comes from a privileged port.
* Rhosts-Authentication only makes sense from privileged
* programs. Of course, if the intruder has root access on his local
* machine, he can connect from any port. So do not use these
* authentication methods from machines that you do not trust.
*/
if (options.rhosts_authentication &&
(remote_port >= IPPORT_RESERVED ||
remote_port < IPPORT_RESERVED / 2)) {
debug("Rhosts Authentication disabled, "
"originating port %d not trusted.", remote_port);
options.rhosts_authentication = 0;
}
#if defined(KRB4) && !defined(KRB5)
if (!packet_connection_is_ipv4() &&
options.kerberos_authentication) {
debug("Kerberos Authentication disabled, only available for IPv4.");
options.kerberos_authentication = 0;
}
#endif /* KRB4 && !KRB5 */
#ifdef AFS
/* If machine has AFS, set process authentication group. */
if (k_hasafs()) {
k_setpag();
k_unlog();
}
#endif /* AFS */
packet_set_nonblocking();
/*
* Start the monitor. That way both processes will have their own
* PKCS#11 sessions. See the PKCS#11 standard for more information on
* fork safety and packet.c for information about forking with the
* engine.
*
* Note that the monitor stays in the function while the child is the
* only one that returns.
*/
altprivsep_start_and_do_monitor(options.use_openssl_engine,
inetd_flag, newsock, startup_pipe);
/*
* 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.
*/
(void) signal(SIGALRM, grace_alarm_handler);
if (!debug_flag)
(void) alarm(options.login_grace_time);
/*
* The child is about to start the first key exchange while the monitor
* stays in altprivsep_start_and_do_monitor() function.
*/
(void) pkcs11_engine_load(options.use_openssl_engine);
/* perform the key exchange */
/* authenticate user and start session */
if (compat20) {
do_ssh2_kex();
authctxt = do_authentication2();
} else {
do_ssh1_kex();
authctxt = do_authentication();
}
/* Authentication complete */
(void) alarm(0);
/* we no longer need an alarm handler */
(void) signal(SIGALRM, SIG_DFL);
if (startup_pipe != -1) {
(void) close(startup_pipe);
startup_pipe = -1;
}
/* ALTPRIVSEP Child */
/*
* Drop privileges, access to privileged resources.
*
* Destroy private host keys, if any.
*
* No need to release any GSS credentials -- sshd only acquires
* creds to determine what mechs it can negotiate then releases
* them right away and uses GSS_C_NO_CREDENTIAL to accept
* contexts.
*/
debug2("Unprivileged server process dropping privileges");
permanently_set_uid(authctxt->pw, options.chroot_directory);
destroy_sensitive_data();
/* Just another safety check. */
if (getuid() != authctxt->pw->pw_uid ||
geteuid() != authctxt->pw->pw_uid) {
fatal("Failed to set uids to %u.", (u_int)authctxt->pw->pw_uid);
}
ssh_gssapi_server_mechs(NULL); /* release cached mechs list */
packet_set_server();
/* now send the authentication context to the monitor */
altprivsep_send_auth_context(authctxt);
mpipe = altprivsep_get_pipe_fd();
if (fcntl(mpipe, F_SETFL, O_NONBLOCK) < 0)
error("fcntl O_NONBLOCK: %.100s", strerror(errno));
#ifdef HAVE_BSM
fatal_remove_cleanup(
(void (*)(void *))audit_failed_login_cleanup,
(void *)authctxt);
#endif /* HAVE_BSM */
if (compat20) {
debug3("setting handler to forward re-key packets to the monitor");
dispatch_range(SSH2_MSG_KEXINIT, SSH2_MSG_TRANSPORT_MAX,
&altprivsep_rekey);
}
/* Logged-in session. */
do_authenticated(authctxt);
/* The connection has been terminated. */
verbose("Closing connection to %.100s", remote_ip);
packet_close();
#ifdef USE_PAM
finish_pam(authctxt);
#endif /* USE_PAM */
return (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_authentication)
auth_mask |= 1 << SSH_AUTH_RHOSTS;
if (options.rhosts_rsa_authentication)
auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
if (options.rsa_authentication)
auth_mask |= 1 << SSH_AUTH_RSA;
#if defined(KRB4) || defined(KRB5)
if (options.kerberos_authentication)
auth_mask |= 1 << SSH_AUTH_KERBEROS;
#endif
#if defined(AFS) || defined(KRB5)
if (options.kerberos_tgt_passing)
auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
#endif
#ifdef AFS
if (options.afs_token_passing)
auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
#endif
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 = 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) {
(void) 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 {
(void) memset(session_key, 0, sizeof(session_key));
(void) BN_bn2bin(session_key_int,
session_key + sizeof(session_key) - len);
compute_session_id(session_id, cookie,
sensitive_data.ssh1_host_key->rsa->n,
sensitive_data.server_key->rsa->n);
/*
* 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;
log("do_connection: generating a fake encryption key");
(void) 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);
(void) 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();
/* 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. */
(void) 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();
}
/*
* Prepare for SSH2 key exchange.
*/
Kex *
prepare_for_ssh2_kex(void)
{
Kex *kex;
Kex_hook_func kex_hook = NULL;
char **locales;
static char **myproposal;
myproposal = my_srv_proposal;
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";
}
/*
* Prepare kex algs / hostkey algs (excluding GSS, which is
* handled in the kex hook.
*
* XXX This should probably move to the kex hook as well, where
* all non-constant kex offer material belongs.
*/
myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
/* If we have no host key algs we can't offer KEXDH/KEX_DH_GEX */
if (myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] == NULL ||
*myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] == '\0')
myproposal[PROPOSAL_KEX_ALGS] = "";
if ((locales = g11n_getlocales()) != NULL) {
/* Solaris 9 SSH expects a list of locales */
if (datafellows & SSH_BUG_LOCALES_NOT_LANGTAGS)
myproposal[PROPOSAL_LANG_STOC] = xjoin(locales, ',');
else
myproposal[PROPOSAL_LANG_STOC] =
g11n_locales2langs(locales);
}
if (locales != NULL)
g11n_freelist(locales);
if ((myproposal[PROPOSAL_LANG_STOC] != NULL) &&
(strcmp(myproposal[PROPOSAL_LANG_STOC], "")) != 0)
myproposal[PROPOSAL_LANG_CTOS] =
xstrdup(myproposal[PROPOSAL_LANG_STOC]);
#ifdef GSSAPI
if (options.gss_keyex)
kex_hook = ssh_gssapi_server_kex_hook;
#endif /* GSSAPI */
kex = kex_setup(NULL, myproposal, kex_hook);
/*
* Note that the my_srv_proposal variable (ie., myproposal) is staticly
* initialized with "" for the language fields; we must not xfree such
* strings.
*/
if (myproposal[PROPOSAL_LANG_STOC] != NULL &&
strcmp(myproposal[PROPOSAL_LANG_STOC], "") != 0)
xfree(myproposal[PROPOSAL_LANG_STOC]);
if (myproposal[PROPOSAL_LANG_CTOS] != NULL &&
strcmp(myproposal[PROPOSAL_LANG_STOC], "") != 0)
xfree(myproposal[PROPOSAL_LANG_CTOS]);
kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
#ifdef GSSAPI
kex->kex[KEX_GSS_GRP1_SHA1] = kexgss_server;
#endif /* GSSAPI */
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;
return (kex);
}
/*
* Do SSH2 key exchange.
*/
static void
do_ssh2_kex(void)
{
Kex *kex;
kex = prepare_for_ssh2_kex();
kex_start(kex);
dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
if (kex->name) {
xfree(kex->name);
kex->name = NULL;
}
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");
}