File: [local] / src / usr.bin / ssh / sshd.c (download)
Revision 1.67, Mon Dec 6 12:10:12 1999 UTC (24 years, 6 months ago) by deraadt
Branch: MAIN
Changes since 1.66: +3 -2 lines
use openpty() if it exists (it does on BSD4_4)
|
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
* Created: Fri Mar 17 17:09:28 1995 ylo
* 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.
*/
#include "includes.h"
RCSID("$Id: sshd.c,v 1.67 1999/12/06 12:10:12 deraadt Exp $");
#include "xmalloc.h"
#include "rsa.h"
#include "ssh.h"
#include "pty.h"
#include "packet.h"
#include "buffer.h"
#include "cipher.h"
#include "mpaux.h"
#include "servconf.h"
#include "uidswap.h"
#include "compat.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
/* Local Xauthority file. */
static char *xauthfile = NULL;
/* Server configuration options. */
ServerOptions options;
/* Name of the server configuration file. */
char *config_file_name = SERVER_CONFIG_FILE;
/*
* Debug mode flag. This can be set on the command line. If debug
* mode is enabled, extra debugging output will be sent to the system
* log, the daemon will not go to background, and will exit after processing
* the first connection.
*/
int debug_flag = 0;
/* Flag indicating that the daemon is being started from inetd. */
int inetd_flag = 0;
/* debug goes to stderr unless inetd_flag is set */
int log_stderr = 0;
/* argv[0] without path. */
char *av0;
/* Saved arguments to main(). */
char **saved_argv;
/*
* This is set to the socket that the server is listening; this is used in
* the SIGHUP signal handler.
*/
int listen_sock;
/*
* 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;
/* Flags set in auth-rsa from authorized_keys flags. These are set in auth-rsa.c. */
int no_port_forwarding_flag = 0;
int no_agent_forwarding_flag = 0;
int no_x11_forwarding_flag = 0;
int no_pty_flag = 0;
/* RSA authentication "command=" option. */
char *forced_command = NULL;
/* RSA authentication "environment=" options. */
struct envstring *custom_environment = NULL;
/* Session id for the current session. */
unsigned char session_id[16];
/*
* 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 {
RSA *private_key; /* Private part of server key. */
RSA *host_key; /* Private part of host key. */
} sensitive_data;
/*
* Flag indicating whether the current session key has been used. This flag
* is set whenever the key is used, and cleared when the key is regenerated.
*/
int key_used = 0;
/* This is set to true when SIGHUP is received. */
int received_sighup = 0;
/* Public side of the server key. This value is regenerated regularly with
the private key. */
RSA *public_key;
/* Prototypes for various functions defined later in this file. */
void do_connection();
void do_authentication(char *user);
void do_authloop(struct passwd * pw);
void do_fake_authloop(char *user);
void do_authenticated(struct passwd * pw);
void do_exec_pty(const char *command, int ptyfd, int ttyfd,
const char *ttyname, struct passwd * pw, const char *term,
const char *display, const char *auth_proto,
const char *auth_data);
void do_exec_no_pty(const char *command, struct passwd * pw,
const char *display, const char *auth_proto,
const char *auth_data);
void do_child(const char *command, struct passwd * pw, const char *term,
const char *display, const char *auth_proto,
const char *auth_data, const char *ttyname);
/*
* 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).
*/
void
sighup_handler(int sig)
{
received_sighup = 1;
signal(SIGHUP, sighup_handler);
}
/*
* Called from the main program after receiving SIGHUP.
* Restarts the server.
*/
void
sighup_restart()
{
log("Received SIGHUP; restarting.");
close(listen_sock);
execv(saved_argv[0], saved_argv);
log("RESTART FAILED: av0='%s', error: %s.", av0, strerror(errno));
exit(1);
}
/*
* Generic signal handler for terminating signals in the master daemon.
* These close the listen socket; not closing it seems to cause "Address
* already in use" problems on some machines, which is inconvenient.
*/
void
sigterm_handler(int sig)
{
log("Received signal %d; terminating.", sig);
close(listen_sock);
exit(255);
}
/*
* SIGCHLD handler. This is called whenever a child dies. This will then
* reap any zombies left by exited c.
*/
void
main_sigchld_handler(int sig)
{
int save_errno = errno;
int status;
while (waitpid(-1, &status, WNOHANG) > 0)
;
signal(SIGCHLD, main_sigchld_handler);
errno = save_errno;
}
/*
* Signal handler for the alarm after the login grace period has expired.
*/
void
grace_alarm_handler(int sig)
{
/* Close the connection. */
packet_close();
/* Log error and exit. */
fatal("Timeout before authentication for %s.", get_remote_ipaddr());
}
/*
* convert ssh auth msg type into description
*/
char *
get_authname(int type)
{
switch (type) {
case SSH_CMSG_AUTH_PASSWORD:
return "password";
case SSH_CMSG_AUTH_RSA:
return "rsa";
case SSH_CMSG_AUTH_RHOSTS_RSA:
return "rhosts-rsa";
case SSH_CMSG_AUTH_RHOSTS:
return "rhosts";
#ifdef KRB4
case SSH_CMSG_AUTH_KERBEROS:
return "kerberos";
#endif
#ifdef SKEY
case SSH_CMSG_AUTH_TIS_RESPONSE:
return "s/key";
#endif
}
fatal("get_authname: unknown auth %d: internal error", type);
return NULL;
}
/*
* 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.
*/
void
key_regeneration_alarm(int sig)
{
int save_errno = errno;
/* Check if we should generate a new key. */
if (key_used) {
/* This should really be done in the background. */
log("Generating new %d bit RSA key.", options.server_key_bits);
if (sensitive_data.private_key != NULL)
RSA_free(sensitive_data.private_key);
sensitive_data.private_key = RSA_new();
if (public_key != NULL)
RSA_free(public_key);
public_key = RSA_new();
rsa_generate_key(sensitive_data.private_key, public_key,
options.server_key_bits);
arc4random_stir();
key_used = 0;
log("RSA key generation complete.");
}
/* Reschedule the alarm. */
signal(SIGALRM, key_regeneration_alarm);
alarm(options.key_regeneration_time);
errno = save_errno;
}
/*
* Main program for the daemon.
*/
int
main(int ac, char **av)
{
extern char *optarg;
extern int optind;
int opt, aux, sock_in, sock_out, newsock, i, pid, on = 1;
int remote_major, remote_minor;
int silentrsa = 0;
struct sockaddr_in sin;
char buf[100]; /* Must not be larger than remote_version. */
char remote_version[100]; /* Must be at least as big as buf. */
const char *remote_ip;
int remote_port;
char *comment;
FILE *f;
struct linger linger;
/* Save argv[0]. */
saved_argv = av;
if (strchr(av[0], '/'))
av0 = strrchr(av[0], '/') + 1;
else
av0 = av[0];
/* 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:diqQ")) != EOF) {
switch (opt) {
case 'f':
config_file_name = optarg;
break;
case 'd':
debug_flag = 1;
options.log_level = SYSLOG_LEVEL_DEBUG;
break;
case 'i':
inetd_flag = 1;
break;
case 'Q':
silentrsa = 1;
break;
case 'q':
options.log_level = SYSLOG_LEVEL_QUIET;
break;
case 'b':
options.server_key_bits = atoi(optarg);
break;
case 'p':
options.port = atoi(optarg);
break;
case 'g':
options.login_grace_time = atoi(optarg);
break;
case 'k':
options.key_regeneration_time = atoi(optarg);
break;
case 'h':
options.host_key_file = optarg;
break;
case 'V':
client_version_string = optarg;
/* only makes sense with inetd_flag, i.e. no listen() */
inetd_flag = 1;
break;
case '?':
default:
fprintf(stderr, "sshd version %s\n", SSH_VERSION);
fprintf(stderr, "Usage: %s [options]\n", av0);
fprintf(stderr, "Options:\n");
fprintf(stderr, " -f file Configuration file (default %s)\n", SERVER_CONFIG_FILE);
fprintf(stderr, " -d Debugging mode\n");
fprintf(stderr, " -i Started from inetd\n");
fprintf(stderr, " -q Quiet (no logging)\n");
fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n");
fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
HOST_KEY_FILE);
exit(1);
}
}
/* check if RSA support exists */
if (rsa_alive() == 0) {
if (silentrsa == 0)
printf("sshd: no RSA support in libssl and libcrypto -- exiting. See ssl(8)\n");
log("no RSA support in libssl and libcrypto -- exiting. See ssl(8)");
exit(1);
}
/* Read server configuration options from the configuration file. */
read_server_config(&options, config_file_name);
/* Fill in default values for those options not explicitly set. */
fill_default_server_options(&options);
/* Check certain values for sanity. */
if (options.server_key_bits < 512 ||
options.server_key_bits > 32768) {
fprintf(stderr, "Bad server key size.\n");
exit(1);
}
if (options.port < 1 || options.port > 65535) {
fprintf(stderr, "Bad port number.\n");
exit(1);
}
/* Check that there are no remaining arguments. */
if (optind < ac) {
fprintf(stderr, "Extra argument %s.\n", av[optind]);
exit(1);
}
/* Force logging to stderr while loading the private host key
unless started from inetd */
log_init(av0, options.log_level, options.log_facility, !inetd_flag);
debug("sshd version %.100s", SSH_VERSION);
sensitive_data.host_key = RSA_new();
errno = 0;
/* Load the host key. It must have empty passphrase. */
if (!load_private_key(options.host_key_file, "",
sensitive_data.host_key, &comment)) {
error("Could not load host key: %.200s: %.100s",
options.host_key_file, strerror(errno));
exit(1);
}
xfree(comment);
/* Initialize the log (it is reinitialized below in case we
forked). */
if (debug_flag && !inetd_flag)
log_stderr = 1;
log_init(av0, 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) {
#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("/dev/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(av0, options.log_level, options.log_facility, log_stderr);
/* 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.host_key->n) - SSH_KEY_BITS_RESERVED &&
options.server_key_bits <
BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
options.server_key_bits =
BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED;
debug("Forcing server key to %d bits to make it differ from host key.",
options.server_key_bits);
}
/* Do not display messages to stdout in RSA code. */
rsa_set_verbose(0);
/* Initialize the random number generator. */
arc4random_stir();
/* Chdir to the root directory so that the current disk can be
unmounted if desired. */
chdir("/");
/* Close connection cleanly after attack. */
cipher_attack_detected = packet_disconnect;
/* Start listening for a socket, unless started from inetd. */
if (inetd_flag) {
int s1, s2;
s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
s2 = dup(s1);
sock_in = dup(0);
sock_out = dup(1);
/* 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);
public_key = RSA_new();
sensitive_data.private_key = RSA_new();
log("Generating %d bit RSA key.", options.server_key_bits);
rsa_generate_key(sensitive_data.private_key, public_key,
options.server_key_bits);
arc4random_stir();
log("RSA key generation complete.");
} else {
/* Create socket for listening. */
listen_sock = socket(AF_INET, SOCK_STREAM, 0);
if (listen_sock < 0)
fatal("socket: %.100s", strerror(errno));
/* Set socket options. We try to make the port reusable
and have it close as fast as possible without waiting
in unnecessary wait states on close. */
setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, (void *) &on,
sizeof(on));
linger.l_onoff = 1;
linger.l_linger = 5;
setsockopt(listen_sock, SOL_SOCKET, SO_LINGER, (void *) &linger,
sizeof(linger));
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_addr = options.listen_addr;
sin.sin_port = htons(options.port);
if (bind(listen_sock, (struct sockaddr *) & sin, sizeof(sin)) < 0) {
error("bind: %.100s", strerror(errno));
shutdown(listen_sock, SHUT_RDWR);
close(listen_sock);
fatal("Bind to port %d failed.", options.port);
}
if (!debug_flag) {
/*
* Record our pid in /etc/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(SSH_DAEMON_PID_FILE, "w");
if (f) {
fprintf(f, "%u\n", (unsigned int) getpid());
fclose(f);
}
}
log("Server listening on port %d.", options.port);
if (listen(listen_sock, 5) < 0)
fatal("listen: %.100s", strerror(errno));
public_key = RSA_new();
sensitive_data.private_key = RSA_new();
log("Generating %d bit RSA key.", options.server_key_bits);
rsa_generate_key(sensitive_data.private_key, public_key,
options.server_key_bits);
arc4random_stir();
log("RSA key generation complete.");
/* Schedule server key regeneration alarm. */
signal(SIGALRM, key_regeneration_alarm);
alarm(options.key_regeneration_time);
/* 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);
/*
* Stay listening for connections until the system crashes or
* the daemon is killed with a signal.
*/
for (;;) {
if (received_sighup)
sighup_restart();
/* Wait in accept until there is a connection. */
aux = sizeof(sin);
newsock = accept(listen_sock, (struct sockaddr *) & sin, &aux);
if (received_sighup)
sighup_restart();
if (newsock < 0) {
if (errno == EINTR)
continue;
error("accept: %.100s", strerror(errno));
continue;
}
/*
* 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_sock);
sock_in = newsock;
sock_out = newsock;
pid = getpid();
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 socket, and start using the
* accepted socket. Reinitialize logging (since our pid has
* changed). We break out of the loop to handle the connection.
*/
close(listen_sock);
sock_in = newsock;
sock_out = newsock;
log_init(av0, 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 %d.", pid);
/* Mark that the key has been used (it was "given" to the child). */
key_used = 1;
arc4random_stir();
/* Close the new socket (the child is now taking care of it). */
close(newsock);
}
}
/* This is the child processing a new connection. */
/*
* 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);
/*
* Set socket options for the connection. We want the socket to
* close as fast as possible without waiting for anything. If the
* connection is not a socket, these will do nothing.
*/
/* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
linger.l_onoff = 1;
linger.l_linger = 5;
setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
/*
* 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();
/* Check whether logins are denied from this host. */
#ifdef LIBWRAP
{
struct request_info req;
request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL);
fromhost(&req);
if (!hosts_access(&req)) {
close(sock_in);
close(sock_out);
refuse(&req);
}
verbose("Connection from %.500s port %d", eval_client(&req), remote_port);
}
#else
/* Log the connection. */
verbose("Connection from %.500s port %d", remote_ip, remote_port);
#endif /* LIBWRAP */
/*
* We don\'t want to listen forever unless the other side
* successfully authenticates itself. So we set up an alarm which is
* cleared after successful authentication. A limit of zero
* indicates no limit. Note that we don\'t set the alarm in debugging
* mode; it is just annoying to have the server exit just when you
* are about to discover the bug.
*/
signal(SIGALRM, grace_alarm_handler);
if (!debug_flag)
alarm(options.login_grace_time);
if (client_version_string != NULL) {
/* we are exec'ed by sshd2, so skip exchange of protocol version */
strlcpy(buf, client_version_string, sizeof(buf));
} else {
/* Send our protocol version identification. */
snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
PROTOCOL_MAJOR, PROTOCOL_MINOR, SSH_VERSION);
if (write(sock_out, buf, strlen(buf)) != strlen(buf))
fatal("Could not write ident string to %s.", get_remote_ipaddr());
/* Read other side\'s version identification. */
for (i = 0; i < sizeof(buf) - 1; i++) {
if (read(sock_in, &buf[i], 1) != 1)
fatal("Did not receive ident string from %s.", get_remote_ipaddr());
if (buf[i] == '\r') {
buf[i] = '\n';
buf[i + 1] = 0;
break;
}
if (buf[i] == '\n') {
/* buf[i] == '\n' */
buf[i + 1] = 0;
break;
}
}
buf[sizeof(buf) - 1] = 0;
}
/*
* Check that the versions match. In future this might accept
* several versions and set appropriate flags to handle them.
*/
if (sscanf(buf, "SSH-%d.%d-%[^\n]\n", &remote_major, &remote_minor,
remote_version) != 3) {
const char *s = "Protocol mismatch.\n";
(void) write(sock_out, s, strlen(s));
close(sock_in);
close(sock_out);
fatal("Bad protocol version identification '%.100s' from %s",
buf, get_remote_ipaddr());
}
debug("Client protocol version %d.%d; client software version %.100s",
remote_major, remote_minor, remote_version);
if (remote_major != PROTOCOL_MAJOR) {
const char *s = "Protocol major versions differ.\n";
(void) write(sock_out, s, strlen(s));
close(sock_in);
close(sock_out);
fatal("Protocol major versions differ for %s: %d vs. %d",
get_remote_ipaddr(),
PROTOCOL_MAJOR, remote_major);
}
/* Check that the client has sufficiently high software version. */
if (remote_major == 1 && remote_minor < 3)
packet_disconnect("Your ssh version is too old and is no longer supported. Please install a newer version.");
if (remote_major == 1 && remote_minor == 3) {
enable_compat13();
if (strcmp(remote_version, "OpenSSH-1.1") != 0) {
debug("Agent forwarding disabled, remote version is not compatible.");
no_agent_forwarding_flag = 1;
}
}
/*
* Check that the connection comes from a privileged port. Rhosts-
* and Rhosts-RSA-Authentication only make sense from priviledged
* 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 (remote_port >= IPPORT_RESERVED ||
remote_port < IPPORT_RESERVED / 2) {
options.rhosts_authentication = 0;
options.rhosts_rsa_authentication = 0;
}
packet_set_nonblocking();
/* Handle the connection. */
do_connection();
#ifdef KRB4
/* Cleanup user's ticket cache file. */
if (options.kerberos_ticket_cleanup)
(void) dest_tkt();
#endif /* KRB4 */
/* Cleanup user's local Xauthority file. */
if (xauthfile)
unlink(xauthfile);
/* The connection has been terminated. */
verbose("Closing connection to %.100s", remote_ip);
packet_close();
exit(0);
}
/*
* Process an incoming connection. Protocol version identifiers have already
* been exchanged. This sends server key and performs the key exchange.
* Server and host keys will no longer be needed after this functions.
*/
void
do_connection()
{
int i, len;
BIGNUM *session_key_int;
unsigned char session_key[SSH_SESSION_KEY_LENGTH];
unsigned char check_bytes[8];
char *user;
unsigned int cipher_type, auth_mask, protocol_flags;
int plen, slen;
u_int32_t rand = 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)
rand = arc4random();
check_bytes[i] = rand & 0xff;
rand >>= 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(check_bytes[i]);
/* Store our public server RSA key. */
packet_put_int(BN_num_bits(public_key->n));
packet_put_bignum(public_key->e);
packet_put_bignum(public_key->n);
/* Store our public host RSA key. */
packet_put_int(BN_num_bits(sensitive_data.host_key->n));
packet_put_bignum(sensitive_data.host_key->e);
packet_put_bignum(sensitive_data.host_key->n);
/* Put protocol flags. */
packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
/* Declare which ciphers we support. */
packet_put_int(cipher_mask());
/* 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;
#ifdef KRB4
if (options.kerberos_authentication)
auth_mask |= 1 << SSH_AUTH_KERBEROS;
#endif
#ifdef AFS
if (options.kerberos_tgt_passing)
auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
if (options.afs_token_passing)
auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
#endif
#ifdef SKEY
if (options.skey_authentication == 1)
auth_mask |= 1 << SSH_AUTH_TIS;
#endif
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 public key and %d bit host key.",
BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n));
/* Read clients reply (cipher type and session key). */
packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
/* Get cipher type. */
cipher_type = packet_get_char();
/* 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 (check_bytes[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. */
session_key_int = BN_new();
packet_get_bignum(session_key_int, &slen);
protocol_flags = packet_get_int();
packet_set_protocol_flags(protocol_flags);
packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
/*
* Decrypt it using our private server key and private host key (key
* with larger modulus first).
*/
if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0) {
/* Private key has bigger modulus. */
if (BN_num_bits(sensitive_data.private_key->n) <
BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
fatal("do_connection: %s: private_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
get_remote_ipaddr(),
BN_num_bits(sensitive_data.private_key->n),
BN_num_bits(sensitive_data.host_key->n),
SSH_KEY_BITS_RESERVED);
}
rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.private_key);
rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.host_key);
} else {
/* Host key has bigger modulus (or they are equal). */
if (BN_num_bits(sensitive_data.host_key->n) <
BN_num_bits(sensitive_data.private_key->n) + SSH_KEY_BITS_RESERVED) {
fatal("do_connection: %s: host_key %d < private_key %d + SSH_KEY_BITS_RESERVED %d",
get_remote_ipaddr(),
BN_num_bits(sensitive_data.host_key->n),
BN_num_bits(sensitive_data.private_key->n),
SSH_KEY_BITS_RESERVED);
}
rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.host_key);
rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.private_key);
}
compute_session_id(session_id, check_bytes,
sensitive_data.host_key->n,
sensitive_data.private_key->n);
/*
* 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.
*/
BN_mask_bits(session_key_int, sizeof(session_key) * 8);
len = BN_num_bytes(session_key_int);
if (len < 0 || len > sizeof(session_key))
fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
get_remote_ipaddr(),
len, sizeof(session_key));
memset(session_key, 0, sizeof(session_key));
BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
/* 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];
/* 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 acknowledgement packet. Note that this packet is sent encrypted. */
packet_start(SSH_SMSG_SUCCESS);
packet_send();
packet_write_wait();
/* Get the name of the user that we wish to log in as. */
packet_read_expect(&plen, SSH_CMSG_USER);
/* Get the user name. */
{
int ulen;
user = packet_get_string(&ulen);
packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER);
}
/* Destroy the private and public keys. They will no longer be needed. */
RSA_free(public_key);
RSA_free(sensitive_data.private_key);
RSA_free(sensitive_data.host_key);
setproctitle("%s", user);
/* Do the authentication. */
do_authentication(user);
}
/*
* Check if the user is allowed to log in via ssh. If user is listed in
* DenyUsers or user's primary group is listed in DenyGroups, false will
* be returned. If AllowUsers isn't empty and user isn't listed there, or
* if AllowGroups isn't empty and user isn't listed there, false will be
* returned. Otherwise true is returned.
* XXX This function should also check if user has a valid shell
*/
static int
allowed_user(struct passwd * pw)
{
struct group *grp;
int i;
/* Shouldn't be called if pw is NULL, but better safe than sorry... */
if (!pw)
return 0;
/* XXX Should check for valid login shell */
/* Return false if user is listed in DenyUsers */
if (options.num_deny_users > 0) {
if (!pw->pw_name)
return 0;
for (i = 0; i < options.num_deny_users; i++)
if (match_pattern(pw->pw_name, options.deny_users[i]))
return 0;
}
/* Return false if AllowUsers isn't empty and user isn't listed there */
if (options.num_allow_users > 0) {
if (!pw->pw_name)
return 0;
for (i = 0; i < options.num_allow_users; i++)
if (match_pattern(pw->pw_name, options.allow_users[i]))
break;
/* i < options.num_allow_users iff we break for loop */
if (i >= options.num_allow_users)
return 0;
}
/* Get the primary group name if we need it. Return false if it fails */
if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
grp = getgrgid(pw->pw_gid);
if (!grp)
return 0;
/* Return false if user's group is listed in DenyGroups */
if (options.num_deny_groups > 0) {
if (!grp->gr_name)
return 0;
for (i = 0; i < options.num_deny_groups; i++)
if (match_pattern(grp->gr_name, options.deny_groups[i]))
return 0;
}
/*
* Return false if AllowGroups isn't empty and user's group
* isn't listed there
*/
if (options.num_allow_groups > 0) {
if (!grp->gr_name)
return 0;
for (i = 0; i < options.num_allow_groups; i++)
if (match_pattern(grp->gr_name, options.allow_groups[i]))
break;
/* i < options.num_allow_groups iff we break for
loop */
if (i >= options.num_allow_groups)
return 0;
}
}
/* We found no reason not to let this user try to log on... */
return 1;
}
/*
* Performs authentication of an incoming connection. Session key has already
* been exchanged and encryption is enabled. User is the user name to log
* in as (received from the client).
*/
void
do_authentication(char *user)
{
struct passwd *pw, pwcopy;
#ifdef AFS
/* If machine has AFS, set process authentication group. */
if (k_hasafs()) {
k_setpag();
k_unlog();
}
#endif /* AFS */
/* Verify that the user is a valid user. */
pw = getpwnam(user);
if (!pw || !allowed_user(pw))
do_fake_authloop(user);
/* Take a copy of the returned structure. */
memset(&pwcopy, 0, sizeof(pwcopy));
pwcopy.pw_name = xstrdup(pw->pw_name);
pwcopy.pw_passwd = xstrdup(pw->pw_passwd);
pwcopy.pw_uid = pw->pw_uid;
pwcopy.pw_gid = pw->pw_gid;
pwcopy.pw_dir = xstrdup(pw->pw_dir);
pwcopy.pw_shell = xstrdup(pw->pw_shell);
pw = &pwcopy;
/*
* If we are not running as root, the user must have the same uid as
* the server.
*/
if (getuid() != 0 && pw->pw_uid != getuid())
packet_disconnect("Cannot change user when server not running as root.");
debug("Attempting authentication for %.100s.", user);
/* If the user has no password, accept authentication immediately. */
if (options.password_authentication &&
#ifdef KRB4
(!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
#endif /* KRB4 */
auth_password(pw, "")) {
/* Authentication with empty password succeeded. */
log("Login for user %s from %.100s, accepted without authentication.",
pw->pw_name, get_remote_ipaddr());
} else {
/* Loop until the user has been authenticated or the
connection is closed, do_authloop() returns only if
authentication is successfull */
do_authloop(pw);
}
/* Check if the user is logging in as root and root logins are disallowed. */
if (pw->pw_uid == 0 && !options.permit_root_login) {
if (forced_command)
log("Root login accepted for forced command.");
else
packet_disconnect("ROOT LOGIN REFUSED FROM %.200s",
get_canonical_hostname());
}
/* The user has been authenticated and accepted. */
packet_start(SSH_SMSG_SUCCESS);
packet_send();
packet_write_wait();
/* Perform session preparation. */
do_authenticated(pw);
}
#define AUTH_FAIL_MAX 6
#define AUTH_FAIL_LOG (AUTH_FAIL_MAX/2)
#define AUTH_FAIL_MSG "Too many authentication failures for %.100s"
/*
* read packets and try to authenticate local user *pw.
* return if authentication is successfull
*/
void
do_authloop(struct passwd * pw)
{
int attempt = 0;
unsigned int bits;
BIGNUM *client_host_key_e, *client_host_key_n;
BIGNUM *n;
char *client_user, *password;
char user[1024];
int plen, dlen, nlen, ulen, elen;
int type = 0;
void (*authlog) (const char *fmt,...) = verbose;
/* Indicate that authentication is needed. */
packet_start(SSH_SMSG_FAILURE);
packet_send();
packet_write_wait();
for (attempt = 1;; attempt++) {
int authenticated = 0;
strlcpy(user, "", sizeof user);
/* Get a packet from the client. */
type = packet_read(&plen);
/* Process the packet. */
switch (type) {
#ifdef AFS
case SSH_CMSG_HAVE_KERBEROS_TGT:
if (!options.kerberos_tgt_passing) {
/* packet_get_all(); */
verbose("Kerberos tgt passing disabled.");
break;
} else {
/* Accept Kerberos tgt. */
char *tgt = packet_get_string(&dlen);
packet_integrity_check(plen, 4 + dlen, type);
if (!auth_kerberos_tgt(pw, tgt))
verbose("Kerberos tgt REFUSED for %s", pw->pw_name);
xfree(tgt);
}
continue;
case SSH_CMSG_HAVE_AFS_TOKEN:
if (!options.afs_token_passing || !k_hasafs()) {
/* packet_get_all(); */
verbose("AFS token passing disabled.");
break;
} else {
/* Accept AFS token. */
char *token_string = packet_get_string(&dlen);
packet_integrity_check(plen, 4 + dlen, type);
if (!auth_afs_token(pw, token_string))
verbose("AFS token REFUSED for %s", pw->pw_name);
xfree(token_string);
}
continue;
#endif /* AFS */
#ifdef KRB4
case SSH_CMSG_AUTH_KERBEROS:
if (!options.kerberos_authentication) {
/* packet_get_all(); */
verbose("Kerberos authentication disabled.");
break;
} else {
/* Try Kerberos v4 authentication. */
KTEXT_ST auth;
char *tkt_user = NULL;
char *kdata = packet_get_string((unsigned int *) &auth.length);
packet_integrity_check(plen, 4 + auth.length, type);
if (auth.length < MAX_KTXT_LEN)
memcpy(auth.dat, kdata, auth.length);
xfree(kdata);
authenticated = auth_krb4(pw->pw_name, &auth, &tkt_user);
if (authenticated) {
snprintf(user, sizeof user, " tktuser %s", tkt_user);
xfree(tkt_user);
}
}
break;
#endif /* KRB4 */
case SSH_CMSG_AUTH_RHOSTS:
if (!options.rhosts_authentication) {
verbose("Rhosts authentication disabled.");
break;
}
/*
* Get client user name. Note that we just have to
* trust the client; this is one reason why rhosts
* authentication is insecure. (Another is
* IP-spoofing on a local network.)
*/
client_user = packet_get_string(&ulen);
packet_integrity_check(plen, 4 + ulen, type);
/* Try to authenticate using /etc/hosts.equiv and
.rhosts. */
authenticated = auth_rhosts(pw, client_user);
snprintf(user, sizeof user, " ruser %s", client_user);
xfree(client_user);
break;
case SSH_CMSG_AUTH_RHOSTS_RSA:
if (!options.rhosts_rsa_authentication) {
verbose("Rhosts with RSA authentication disabled.");
break;
}
/*
* Get client user name. Note that we just have to
* trust the client; root on the client machine can
* claim to be any user.
*/
client_user = packet_get_string(&ulen);
/* Get the client host key. */
client_host_key_e = BN_new();
client_host_key_n = BN_new();
bits = packet_get_int();
packet_get_bignum(client_host_key_e, &elen);
packet_get_bignum(client_host_key_n, &nlen);
if (bits != BN_num_bits(client_host_key_n))
error("Warning: keysize mismatch for client_host_key: "
"actual %d, announced %d", BN_num_bits(client_host_key_n), bits);
packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type);
authenticated = auth_rhosts_rsa(pw, client_user,
client_host_key_e, client_host_key_n);
BN_clear_free(client_host_key_e);
BN_clear_free(client_host_key_n);
snprintf(user, sizeof user, " ruser %s", client_user);
xfree(client_user);
break;
case SSH_CMSG_AUTH_RSA:
if (!options.rsa_authentication) {
verbose("RSA authentication disabled.");
break;
}
/* RSA authentication requested. */
n = BN_new();
packet_get_bignum(n, &nlen);
packet_integrity_check(plen, nlen, type);
authenticated = auth_rsa(pw, n);
BN_clear_free(n);
break;
case SSH_CMSG_AUTH_PASSWORD:
if (!options.password_authentication) {
verbose("Password authentication disabled.");
break;
}
/*
* Read user password. It is in plain text, but was
* transmitted over the encrypted channel so it is
* not visible to an outside observer.
*/
password = packet_get_string(&dlen);
packet_integrity_check(plen, 4 + dlen, type);
/* Try authentication with the password. */
authenticated = auth_password(pw, password);
memset(password, 0, strlen(password));
xfree(password);
break;
#ifdef SKEY
case SSH_CMSG_AUTH_TIS:
debug("rcvd SSH_CMSG_AUTH_TIS");
if (options.skey_authentication == 1) {
char *skeyinfo = skey_keyinfo(pw->pw_name);
if (skeyinfo == NULL) {
debug("generating fake skeyinfo for %.100s.", pw->pw_name);
skeyinfo = skey_fake_keyinfo(pw->pw_name);
}
if (skeyinfo != NULL) {
/* we send our s/key- in tis-challenge messages */
debug("sending challenge '%s'", skeyinfo);
packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
packet_put_string(skeyinfo, strlen(skeyinfo));
packet_send();
packet_write_wait();
continue;
}
}
break;
case SSH_CMSG_AUTH_TIS_RESPONSE:
debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
if (options.skey_authentication == 1) {
char *response = packet_get_string(&dlen);
debug("skey response == '%s'", response);
packet_integrity_check(plen, 4 + dlen, type);
authenticated = (skey_haskey(pw->pw_name) == 0 &&
skey_passcheck(pw->pw_name, response) != -1);
xfree(response);
}
break;
#else
case SSH_CMSG_AUTH_TIS:
/* TIS Authentication is unsupported */
log("TIS authentication unsupported.");
break;
#endif
default:
/*
* Any unknown messages will be ignored (and failure
* returned) during authentication.
*/
log("Unknown message during authentication: type %d", type);
break;
}
/* Raise logging level */
if (authenticated ||
attempt == AUTH_FAIL_LOG ||
type == SSH_CMSG_AUTH_PASSWORD)
authlog = log;
authlog("%s %s for %.200s from %.200s port %d%s",
authenticated ? "Accepted" : "Failed",
get_authname(type),
pw->pw_uid == 0 ? "ROOT" : pw->pw_name,
get_remote_ipaddr(),
get_remote_port(),
user);
if (authenticated)
return;
if (attempt > AUTH_FAIL_MAX)
packet_disconnect(AUTH_FAIL_MSG, pw->pw_name);
/* Send a message indicating that the authentication attempt failed. */
packet_start(SSH_SMSG_FAILURE);
packet_send();
packet_write_wait();
}
}
/*
* The user does not exist or access is denied,
* but fake indication that authentication is needed.
*/
void
do_fake_authloop(char *user)
{
int attempt = 0;
log("Faking authloop for illegal user %.200s from %.200s port %d",
user,
get_remote_ipaddr(),
get_remote_port());
/* Indicate that authentication is needed. */
packet_start(SSH_SMSG_FAILURE);
packet_send();
packet_write_wait();
/*
* Keep reading packets, and always respond with a failure. This is
* to avoid disclosing whether such a user really exists.
*/
for (attempt = 1;; attempt++) {
/* Read a packet. This will not return if the client disconnects. */
int plen;
int type = packet_read(&plen);
#ifdef SKEY
int dlen;
char *password, *skeyinfo;
if (options.password_authentication &&
options.skey_authentication == 1 &&
type == SSH_CMSG_AUTH_PASSWORD &&
(password = packet_get_string(&dlen)) != NULL &&
dlen == 5 &&
strncasecmp(password, "s/key", 5) == 0 &&
(skeyinfo = skey_fake_keyinfo(user)) != NULL) {
/* Send a fake s/key challenge. */
packet_send_debug(skeyinfo);
}
#endif
if (attempt > AUTH_FAIL_MAX)
packet_disconnect(AUTH_FAIL_MSG, user);
/*
* Send failure. This should be indistinguishable from a
* failed authentication.
*/
packet_start(SSH_SMSG_FAILURE);
packet_send();
packet_write_wait();
}
/* NOTREACHED */
abort();
}
/*
* Remove local Xauthority file.
*/
static void
xauthfile_cleanup_proc(void *ignore)
{
debug("xauthfile_cleanup_proc called");
if (xauthfile != NULL) {
unlink(xauthfile);
xfree(xauthfile);
xauthfile = NULL;
}
}
/*
* Prepares for an interactive session. This is called after the user has
* been successfully authenticated. During this message exchange, pseudo
* terminals are allocated, X11, TCP/IP, and authentication agent forwardings
* are requested, etc.
*/
void
do_authenticated(struct passwd * pw)
{
int type;
int compression_level = 0, enable_compression_after_reply = 0;
int have_pty = 0, ptyfd = -1, ttyfd = -1, xauthfd = -1;
int row, col, xpixel, ypixel, screen;
char ttyname[64];
char *command, *term = NULL, *display = NULL, *proto = NULL,
*data = NULL;
struct group *grp;
gid_t tty_gid;
mode_t tty_mode;
int n_bytes;
/*
* Cancel the alarm we set to limit the time taken for
* authentication.
*/
alarm(0);
/*
* Inform the channel mechanism that we are the server side and that
* the client may request to connect to any port at all. (The user
* could do it anyway, and we wouldn\'t know what is permitted except
* by the client telling us, so we can equally well trust the client
* not to request anything bogus.)
*/
channel_permit_all_opens();
/*
* We stay in this loop until the client requests to execute a shell
* or a command.
*/
while (1) {
int plen, dlen;
/* Get a packet from the client. */
type = packet_read(&plen);
/* Process the packet. */
switch (type) {
case SSH_CMSG_REQUEST_COMPRESSION:
packet_integrity_check(plen, 4, type);
compression_level = packet_get_int();
if (compression_level < 1 || compression_level > 9) {
packet_send_debug("Received illegal compression level %d.",
compression_level);
goto fail;
}
/* Enable compression after we have responded with SUCCESS. */
enable_compression_after_reply = 1;
break;
case SSH_CMSG_REQUEST_PTY:
if (no_pty_flag) {
debug("Allocating a pty not permitted for this authentication.");
goto fail;
}
if (have_pty)
packet_disconnect("Protocol error: you already have a pty.");
debug("Allocating pty.");
/* Allocate a pty and open it. */
if (!pty_allocate(&ptyfd, &ttyfd, ttyname,
sizeof(ttyname))) {
error("Failed to allocate pty.");
goto fail;
}
/* Determine the group to make the owner of the tty. */
grp = getgrnam("tty");
if (grp) {
tty_gid = grp->gr_gid;
tty_mode = S_IRUSR | S_IWUSR | S_IWGRP;
} else {
tty_gid = pw->pw_gid;
tty_mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH;
}
/* Change ownership of the tty. */
if (chown(ttyname, pw->pw_uid, tty_gid) < 0)
fatal("chown(%.100s, %d, %d) failed: %.100s",
ttyname, pw->pw_uid, tty_gid, strerror(errno));
if (chmod(ttyname, tty_mode) < 0)
fatal("chmod(%.100s, 0%o) failed: %.100s",
ttyname, tty_mode, strerror(errno));
/* Get TERM from the packet. Note that the value may be of arbitrary length. */
term = packet_get_string(&dlen);
packet_integrity_check(dlen, strlen(term), type);
/* packet_integrity_check(plen, 4 + dlen + 4*4 + n_bytes, type); */
/* Remaining bytes */
n_bytes = plen - (4 + dlen + 4 * 4);
if (strcmp(term, "") == 0)
term = NULL;
/* Get window size from the packet. */
row = packet_get_int();
col = packet_get_int();
xpixel = packet_get_int();
ypixel = packet_get_int();
pty_change_window_size(ptyfd, row, col, xpixel, ypixel);
/* Get tty modes from the packet. */
tty_parse_modes(ttyfd, &n_bytes);
packet_integrity_check(plen, 4 + dlen + 4 * 4 + n_bytes, type);
/* Indicate that we now have a pty. */
have_pty = 1;
break;
case SSH_CMSG_X11_REQUEST_FORWARDING:
if (!options.x11_forwarding) {
packet_send_debug("X11 forwarding disabled in server configuration file.");
goto fail;
}
#ifdef XAUTH_PATH
if (no_x11_forwarding_flag) {
packet_send_debug("X11 forwarding not permitted for this authentication.");
goto fail;
}
debug("Received request for X11 forwarding with auth spoofing.");
if (display)
packet_disconnect("Protocol error: X11 display already set.");
{
int proto_len, data_len;
proto = packet_get_string(&proto_len);
data = packet_get_string(&data_len);
packet_integrity_check(plen, 4 + proto_len + 4 + data_len + 4, type);
}
if (packet_get_protocol_flags() & SSH_PROTOFLAG_SCREEN_NUMBER)
screen = packet_get_int();
else
screen = 0;
display = x11_create_display_inet(screen);
if (!display)
goto fail;
/* Setup to always have a local .Xauthority. */
xauthfile = xmalloc(MAXPATHLEN);
snprintf(xauthfile, MAXPATHLEN, "/tmp/XauthXXXXXX");
if ((xauthfd = mkstemp(xauthfile)) != -1) {
fchown(xauthfd, pw->pw_uid, pw->pw_gid);
close(xauthfd);
fatal_add_cleanup(xauthfile_cleanup_proc, NULL);
} else {
xfree(xauthfile);
xauthfile = NULL;
}
break;
#else /* XAUTH_PATH */
packet_send_debug("No xauth program; cannot forward with spoofing.");
goto fail;
#endif /* XAUTH_PATH */
case SSH_CMSG_AGENT_REQUEST_FORWARDING:
if (no_agent_forwarding_flag) {
debug("Authentication agent forwarding not permitted for this authentication.");
goto fail;
}
debug("Received authentication agent forwarding request.");
auth_input_request_forwarding(pw);
break;
case SSH_CMSG_PORT_FORWARD_REQUEST:
if (no_port_forwarding_flag) {
debug("Port forwarding not permitted for this authentication.");
goto fail;
}
debug("Received TCP/IP port forwarding request.");
channel_input_port_forward_request(pw->pw_uid == 0);
break;
case SSH_CMSG_MAX_PACKET_SIZE:
if (packet_set_maxsize(packet_get_int()) < 0)
goto fail;
break;
case SSH_CMSG_EXEC_SHELL:
/* Set interactive/non-interactive mode. */
packet_set_interactive(have_pty || display != NULL,
options.keepalives);
if (forced_command != NULL)
goto do_forced_command;
debug("Forking shell.");
packet_integrity_check(plen, 0, type);
if (have_pty)
do_exec_pty(NULL, ptyfd, ttyfd, ttyname, pw, term, display, proto, data);
else
do_exec_no_pty(NULL, pw, display, proto, data);
return;
case SSH_CMSG_EXEC_CMD:
/* Set interactive/non-interactive mode. */
packet_set_interactive(have_pty || display != NULL,
options.keepalives);
if (forced_command != NULL)
goto do_forced_command;
/* Get command from the packet. */
{
int dlen;
command = packet_get_string(&dlen);
debug("Executing command '%.500s'", command);
packet_integrity_check(plen, 4 + dlen, type);
}
if (have_pty)
do_exec_pty(command, ptyfd, ttyfd, ttyname, pw, term, display, proto, data);
else
do_exec_no_pty(command, pw, display, proto, data);
xfree(command);
return;
default:
/*
* Any unknown messages in this phase are ignored,
* and a failure message is returned.
*/
log("Unknown packet type received after authentication: %d", type);
goto fail;
}
/* The request was successfully processed. */
packet_start(SSH_SMSG_SUCCESS);
packet_send();
packet_write_wait();
/* Enable compression now that we have replied if appropriate. */
if (enable_compression_after_reply) {
enable_compression_after_reply = 0;
packet_start_compression(compression_level);
}
continue;
fail:
/* The request failed. */
packet_start(SSH_SMSG_FAILURE);
packet_send();
packet_write_wait();
continue;
do_forced_command:
/*
* There is a forced command specified for this login.
* Execute it.
*/
debug("Executing forced command: %.900s", forced_command);
if (have_pty)
do_exec_pty(forced_command, ptyfd, ttyfd, ttyname, pw, term, display, proto, data);
else
do_exec_no_pty(forced_command, pw, display, proto, data);
return;
}
}
/*
* This is called to fork and execute a command when we have no tty. This
* will call do_child from the child, and server_loop from the parent after
* setting up file descriptors and such.
*/
void
do_exec_no_pty(const char *command, struct passwd * pw,
const char *display, const char *auth_proto,
const char *auth_data)
{
int pid;
#ifdef USE_PIPES
int pin[2], pout[2], perr[2];
/* Allocate pipes for communicating with the program. */
if (pipe(pin) < 0 || pipe(pout) < 0 || pipe(perr) < 0)
packet_disconnect("Could not create pipes: %.100s",
strerror(errno));
#else /* USE_PIPES */
int inout[2], err[2];
/* Uses socket pairs to communicate with the program. */
if (socketpair(AF_UNIX, SOCK_STREAM, 0, inout) < 0 ||
socketpair(AF_UNIX, SOCK_STREAM, 0, err) < 0)
packet_disconnect("Could not create socket pairs: %.100s",
strerror(errno));
#endif /* USE_PIPES */
setproctitle("%s@notty", pw->pw_name);
/* Fork the child. */
if ((pid = fork()) == 0) {
/* Child. Reinitialize the log since the pid has changed. */
log_init(av0, options.log_level, options.log_facility, log_stderr);
/*
* Create a new session and process group since the 4.4BSD
* setlogin() affects the entire process group.
*/
if (setsid() < 0)
error("setsid failed: %.100s", strerror(errno));
#ifdef USE_PIPES
/*
* Redirect stdin. We close the parent side of the socket
* pair, and make the child side the standard input.
*/
close(pin[1]);
if (dup2(pin[0], 0) < 0)
perror("dup2 stdin");
close(pin[0]);
/* Redirect stdout. */
close(pout[0]);
if (dup2(pout[1], 1) < 0)
perror("dup2 stdout");
close(pout[1]);
/* Redirect stderr. */
close(perr[0]);
if (dup2(perr[1], 2) < 0)
perror("dup2 stderr");
close(perr[1]);
#else /* USE_PIPES */
/*
* Redirect stdin, stdout, and stderr. Stdin and stdout will
* use the same socket, as some programs (particularly rdist)
* seem to depend on it.
*/
close(inout[1]);
close(err[1]);
if (dup2(inout[0], 0) < 0) /* stdin */
perror("dup2 stdin");
if (dup2(inout[0], 1) < 0) /* stdout. Note: same socket as stdin. */
perror("dup2 stdout");
if (dup2(err[0], 2) < 0) /* stderr */
perror("dup2 stderr");
#endif /* USE_PIPES */
/* Do processing for the child (exec command etc). */
do_child(command, pw, NULL, display, auth_proto, auth_data, NULL);
/* NOTREACHED */
}
if (pid < 0)
packet_disconnect("fork failed: %.100s", strerror(errno));
#ifdef USE_PIPES
/* We are the parent. Close the child sides of the pipes. */
close(pin[0]);
close(pout[1]);
close(perr[1]);
/* Enter the interactive session. */
server_loop(pid, pin[1], pout[0], perr[0]);
/* server_loop has closed pin[1], pout[1], and perr[1]. */
#else /* USE_PIPES */
/* We are the parent. Close the child sides of the socket pairs. */
close(inout[0]);
close(err[0]);
/*
* Enter the interactive session. Note: server_loop must be able to
* handle the case that fdin and fdout are the same.
*/
server_loop(pid, inout[1], inout[1], err[1]);
/* server_loop has closed inout[1] and err[1]. */
#endif /* USE_PIPES */
}
struct pty_cleanup_context {
const char *ttyname;
int pid;
};
/*
* Function to perform cleanup if we get aborted abnormally (e.g., due to a
* dropped connection).
*/
void
pty_cleanup_proc(void *context)
{
struct pty_cleanup_context *cu = context;
debug("pty_cleanup_proc called");
/* Record that the user has logged out. */
record_logout(cu->pid, cu->ttyname);
/* Release the pseudo-tty. */
pty_release(cu->ttyname);
}
/*
* This is called to fork and execute a command when we have a tty. This
* will call do_child from the child, and server_loop from the parent after
* setting up file descriptors, controlling tty, updating wtmp, utmp,
* lastlog, and other such operations.
*/
void
do_exec_pty(const char *command, int ptyfd, int ttyfd,
const char *ttyname, struct passwd * pw, const char *term,
const char *display, const char *auth_proto,
const char *auth_data)
{
int pid, fdout;
const char *hostname;
time_t last_login_time;
char buf[100], *time_string;
FILE *f;
char line[256];
struct stat st;
int quiet_login;
struct sockaddr_in from;
int fromlen;
struct pty_cleanup_context cleanup_context;
/* Get remote host name. */
hostname = get_canonical_hostname();
/*
* Get the time when the user last logged in. Buf will be set to
* contain the hostname the last login was from.
*/
if (!options.use_login) {
last_login_time = get_last_login_time(pw->pw_uid, pw->pw_name,
buf, sizeof(buf));
}
setproctitle("%s@%s", pw->pw_name, strrchr(ttyname, '/') + 1);
/* Fork the child. */
if ((pid = fork()) == 0) {
pid = getpid();
/* Child. Reinitialize the log because the pid has
changed. */
log_init(av0, options.log_level, options.log_facility, log_stderr);
/* Close the master side of the pseudo tty. */
close(ptyfd);
/* Make the pseudo tty our controlling tty. */
pty_make_controlling_tty(&ttyfd, ttyname);
/* Redirect stdin from the pseudo tty. */
if (dup2(ttyfd, fileno(stdin)) < 0)
error("dup2 stdin failed: %.100s", strerror(errno));
/* Redirect stdout to the pseudo tty. */
if (dup2(ttyfd, fileno(stdout)) < 0)
error("dup2 stdin failed: %.100s", strerror(errno));
/* Redirect stderr to the pseudo tty. */
if (dup2(ttyfd, fileno(stderr)) < 0)
error("dup2 stdin failed: %.100s", strerror(errno));
/* Close the extra descriptor for the pseudo tty. */
close(ttyfd);
/*
* Get IP address of client. This is needed because we want
* to record where the user logged in from. If the
* connection is not a socket, let the ip address be 0.0.0.0.
*/
memset(&from, 0, sizeof(from));
if (packet_get_connection_in() == packet_get_connection_out()) {
fromlen = sizeof(from);
if (getpeername(packet_get_connection_in(),
(struct sockaddr *) & from, &fromlen) < 0) {
debug("getpeername: %.100s", strerror(errno));
fatal_cleanup();
}
}
/* Record that there was a login on that terminal. */
record_login(pid, ttyname, pw->pw_name, pw->pw_uid, hostname,
&from);
/* Check if .hushlogin exists. */
snprintf(line, sizeof line, "%.200s/.hushlogin", pw->pw_dir);
quiet_login = stat(line, &st) >= 0;
/*
* If the user has logged in before, display the time of last
* login. However, don't display anything extra if a command
* has been specified (so that ssh can be used to execute
* commands on a remote machine without users knowing they
* are going to another machine). Login(1) will do this for
* us as well, so check if login(1) is used
*/
if (command == NULL && last_login_time != 0 && !quiet_login &&
!options.use_login) {
/* Convert the date to a string. */
time_string = ctime(&last_login_time);
/* Remove the trailing newline. */
if (strchr(time_string, '\n'))
*strchr(time_string, '\n') = 0;
/* Display the last login time. Host if displayed
if known. */
if (strcmp(buf, "") == 0)
printf("Last login: %s\r\n", time_string);
else
printf("Last login: %s from %s\r\n", time_string, buf);
}
/*
* Print /etc/motd unless a command was specified or printing
* it was disabled in server options or login(1) will be
* used. Note that some machines appear to print it in
* /etc/profile or similar.
*/
if (command == NULL && options.print_motd && !quiet_login &&
!options.use_login) {
/* Print /etc/motd if it exists. */
f = fopen("/etc/motd", "r");
if (f) {
while (fgets(line, sizeof(line), f))
fputs(line, stdout);
fclose(f);
}
}
/* Do common processing for the child, such as execing the command. */
do_child(command, pw, term, display, auth_proto, auth_data, ttyname);
/* NOTREACHED */
}
if (pid < 0)
packet_disconnect("fork failed: %.100s", strerror(errno));
/* Parent. Close the slave side of the pseudo tty. */
close(ttyfd);
/*
* Create another descriptor of the pty master side for use as the
* standard input. We could use the original descriptor, but this
* simplifies code in server_loop. The descriptor is bidirectional.
*/
fdout = dup(ptyfd);
if (fdout < 0)
packet_disconnect("dup failed: %.100s", strerror(errno));
/*
* Add a cleanup function to clear the utmp entry and record logout
* time in case we call fatal() (e.g., the connection gets closed).
*/
cleanup_context.pid = pid;
cleanup_context.ttyname = ttyname;
fatal_add_cleanup(pty_cleanup_proc, (void *) &cleanup_context);
/* Enter interactive session. */
server_loop(pid, ptyfd, fdout, -1);
/* server_loop has not closed ptyfd and fdout. */
/* Cancel the cleanup function. */
fatal_remove_cleanup(pty_cleanup_proc, (void *) &cleanup_context);
/* Record that the user has logged out. */
record_logout(pid, ttyname);
/* Release the pseudo-tty. */
pty_release(ttyname);
/*
* Close the server side of the socket pairs. We must do this after
* the pty cleanup, so that another process doesn't get this pty
* while we're still cleaning up.
*/
close(ptyfd);
close(fdout);
}
/*
* Sets the value of the given variable in the environment. If the variable
* already exists, its value is overriden.
*/
void
child_set_env(char ***envp, unsigned int *envsizep, const char *name,
const char *value)
{
unsigned int i, namelen;
char **env;
/*
* Find the slot where the value should be stored. If the variable
* already exists, we reuse the slot; otherwise we append a new slot
* at the end of the array, expanding if necessary.
*/
env = *envp;
namelen = strlen(name);
for (i = 0; env[i]; i++)
if (strncmp(env[i], name, namelen) == 0 && env[i][namelen] == '=')
break;
if (env[i]) {
/* Reuse the slot. */
xfree(env[i]);
} else {
/* New variable. Expand if necessary. */
if (i >= (*envsizep) - 1) {
(*envsizep) += 50;
env = (*envp) = xrealloc(env, (*envsizep) * sizeof(char *));
}
/* Need to set the NULL pointer at end of array beyond the new slot. */
env[i + 1] = NULL;
}
/* Allocate space and format the variable in the appropriate slot. */
env[i] = xmalloc(strlen(name) + 1 + strlen(value) + 1);
snprintf(env[i], strlen(name) + 1 + strlen(value) + 1, "%s=%s", name, value);
}
/*
* Reads environment variables from the given file and adds/overrides them
* into the environment. If the file does not exist, this does nothing.
* Otherwise, it must consist of empty lines, comments (line starts with '#')
* and assignments of the form name=value. No other forms are allowed.
*/
void
read_environment_file(char ***env, unsigned int *envsize,
const char *filename)
{
FILE *f;
char buf[4096];
char *cp, *value;
f = fopen(filename, "r");
if (!f)
return;
while (fgets(buf, sizeof(buf), f)) {
for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
;
if (!*cp || *cp == '#' || *cp == '\n')
continue;
if (strchr(cp, '\n'))
*strchr(cp, '\n') = '\0';
value = strchr(cp, '=');
if (value == NULL) {
fprintf(stderr, "Bad line in %.100s: %.200s\n", filename, buf);
continue;
}
/* Replace the equals sign by nul, and advance value to the value string. */
*value = '\0';
value++;
child_set_env(env, envsize, cp, value);
}
fclose(f);
}
/*
* Performs common processing for the child, such as setting up the
* environment, closing extra file descriptors, setting the user and group
* ids, and executing the command or shell.
*/
void
do_child(const char *command, struct passwd * pw, const char *term,
const char *display, const char *auth_proto,
const char *auth_data, const char *ttyname)
{
const char *shell, *cp = NULL;
char buf[256];
FILE *f;
unsigned int envsize, i;
char **env;
extern char **environ;
struct stat st;
char *argv[10];
f = fopen("/etc/nologin", "r");
if (f) {
/* /etc/nologin exists. Print its contents and exit. */
while (fgets(buf, sizeof(buf), f))
fputs(buf, stderr);
fclose(f);
if (pw->pw_uid != 0)
exit(254);
}
/* Set login name in the kernel. */
if (setlogin(pw->pw_name) < 0)
error("setlogin failed: %s", strerror(errno));
/* Set uid, gid, and groups. */
/* Login(1) does this as well, and it needs uid 0 for the "-h"
switch, so we let login(1) to this for us. */
if (!options.use_login) {
if (getuid() == 0 || geteuid() == 0) {
if (setgid(pw->pw_gid) < 0) {
perror("setgid");
exit(1);
}
/* Initialize the group list. */
if (initgroups(pw->pw_name, pw->pw_gid) < 0) {
perror("initgroups");
exit(1);
}
endgrent();
/* Permanently switch to the desired uid. */
permanently_set_uid(pw->pw_uid);
}
if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid)
fatal("Failed to set uids to %d.", (int) pw->pw_uid);
}
/*
* Get the shell from the password data. An empty shell field is
* legal, and means /bin/sh.
*/
shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
#ifdef AFS
/* Try to get AFS tokens for the local cell. */
if (k_hasafs()) {
char cell[64];
if (k_afs_cell_of_file(pw->pw_dir, cell, sizeof(cell)) == 0)
krb_afslog(cell, 0);
krb_afslog(0, 0);
}
#endif /* AFS */
/* Initialize the environment. */
envsize = 100;
env = xmalloc(envsize * sizeof(char *));
env[0] = NULL;
if (!options.use_login) {
/* Set basic environment. */
child_set_env(&env, &envsize, "USER", pw->pw_name);
child_set_env(&env, &envsize, "LOGNAME", pw->pw_name);
child_set_env(&env, &envsize, "HOME", pw->pw_dir);
child_set_env(&env, &envsize, "PATH", _PATH_STDPATH);
snprintf(buf, sizeof buf, "%.200s/%.50s",
_PATH_MAILDIR, pw->pw_name);
child_set_env(&env, &envsize, "MAIL", buf);
/* Normal systems set SHELL by default. */
child_set_env(&env, &envsize, "SHELL", shell);
}
if (getenv("TZ"))
child_set_env(&env, &envsize, "TZ", getenv("TZ"));
/* Set custom environment options from RSA authentication. */
while (custom_environment) {
struct envstring *ce = custom_environment;
char *s = ce->s;
int i;
for (i = 0; s[i] != '=' && s[i]; i++);
if (s[i] == '=') {
s[i] = 0;
child_set_env(&env, &envsize, s, s + i + 1);
}
custom_environment = ce->next;
xfree(ce->s);
xfree(ce);
}
snprintf(buf, sizeof buf, "%.50s %d %d",
get_remote_ipaddr(), get_remote_port(), options.port);
child_set_env(&env, &envsize, "SSH_CLIENT", buf);
if (ttyname)
child_set_env(&env, &envsize, "SSH_TTY", ttyname);
if (term)
child_set_env(&env, &envsize, "TERM", term);
if (display)
child_set_env(&env, &envsize, "DISPLAY", display);
#ifdef KRB4
{
extern char *ticket;
if (ticket)
child_set_env(&env, &envsize, "KRBTKFILE", ticket);
}
#endif /* KRB4 */
if (xauthfile)
child_set_env(&env, &envsize, "XAUTHORITY", xauthfile);
if (auth_get_socket_name() != NULL)
child_set_env(&env, &envsize, SSH_AUTHSOCKET_ENV_NAME,
auth_get_socket_name());
/* read $HOME/.ssh/environment. */
if (!options.use_login) {
snprintf(buf, sizeof buf, "%.200s/.ssh/environment", pw->pw_dir);
read_environment_file(&env, &envsize, buf);
}
if (debug_flag) {
/* dump the environment */
fprintf(stderr, "Environment:\n");
for (i = 0; env[i]; i++)
fprintf(stderr, " %.200s\n", env[i]);
}
/*
* Close the connection descriptors; note that this is the child, and
* the server will still have the socket open, and it is important
* that we do not shutdown it. Note that the descriptors cannot be
* closed before building the environment, as we call
* get_remote_ipaddr there.
*/
if (packet_get_connection_in() == packet_get_connection_out())
close(packet_get_connection_in());
else {
close(packet_get_connection_in());
close(packet_get_connection_out());
}
/*
* Close all descriptors related to channels. They will still remain
* open in the parent.
*/
/* XXX better use close-on-exec? -markus */
channel_close_all();
/*
* Close any extra file descriptors. Note that there may still be
* descriptors left by system functions. They will be closed later.
*/
endpwent();
endhostent();
/*
* Close any extra open file descriptors so that we don\'t have them
* hanging around in clients. Note that we want to do this after
* initgroups, because at least on Solaris 2.3 it leaves file
* descriptors open.
*/
for (i = 3; i < 64; i++)
close(i);
/* Change current directory to the user\'s home directory. */
if (chdir(pw->pw_dir) < 0)
fprintf(stderr, "Could not chdir to home directory %s: %s\n",
pw->pw_dir, strerror(errno));
/*
* Must take new environment into use so that .ssh/rc, /etc/sshrc and
* xauth are run in the proper environment.
*/
environ = env;
/*
* Run $HOME/.ssh/rc, /etc/sshrc, or xauth (whichever is found first
* in this order).
*/
if (!options.use_login) {
if (stat(SSH_USER_RC, &st) >= 0) {
if (debug_flag)
fprintf(stderr, "Running /bin/sh %s\n", SSH_USER_RC);
f = popen("/bin/sh " SSH_USER_RC, "w");
if (f) {
if (auth_proto != NULL && auth_data != NULL)
fprintf(f, "%s %s\n", auth_proto, auth_data);
pclose(f);
} else
fprintf(stderr, "Could not run %s\n", SSH_USER_RC);
} else if (stat(SSH_SYSTEM_RC, &st) >= 0) {
if (debug_flag)
fprintf(stderr, "Running /bin/sh %s\n", SSH_SYSTEM_RC);
f = popen("/bin/sh " SSH_SYSTEM_RC, "w");
if (f) {
if (auth_proto != NULL && auth_data != NULL)
fprintf(f, "%s %s\n", auth_proto, auth_data);
pclose(f);
} else
fprintf(stderr, "Could not run %s\n", SSH_SYSTEM_RC);
}
#ifdef XAUTH_PATH
else {
/* Add authority data to .Xauthority if appropriate. */
if (auth_proto != NULL && auth_data != NULL) {
if (debug_flag)
fprintf(stderr, "Running %.100s add %.100s %.100s %.100s\n",
XAUTH_PATH, display, auth_proto, auth_data);
f = popen(XAUTH_PATH " -q -", "w");
if (f) {
fprintf(f, "add %s %s %s\n", display, auth_proto, auth_data);
fclose(f);
} else
fprintf(stderr, "Could not run %s -q -\n", XAUTH_PATH);
}
}
#endif /* XAUTH_PATH */
/* Get the last component of the shell name. */
cp = strrchr(shell, '/');
if (cp)
cp++;
else
cp = shell;
}
/*
* If we have no command, execute the shell. In this case, the shell
* name to be passed in argv[0] is preceded by '-' to indicate that
* this is a login shell.
*/
if (!command) {
if (!options.use_login) {
char buf[256];
/*
* Check for mail if we have a tty and it was enabled
* in server options.
*/
if (ttyname && options.check_mail) {
char *mailbox;
struct stat mailstat;
mailbox = getenv("MAIL");
if (mailbox != NULL) {
if (stat(mailbox, &mailstat) != 0 || mailstat.st_size == 0)
printf("No mail.\n");
else if (mailstat.st_mtime < mailstat.st_atime)
printf("You have mail.\n");
else
printf("You have new mail.\n");
}
}
/* Start the shell. Set initial character to '-'. */
buf[0] = '-';
strncpy(buf + 1, cp, sizeof(buf) - 1);
buf[sizeof(buf) - 1] = 0;
/* Execute the shell. */
argv[0] = buf;
argv[1] = NULL;
execve(shell, argv, env);
/* Executing the shell failed. */
perror(shell);
exit(1);
} else {
/* Launch login(1). */
execl("/usr/bin/login", "login", "-h", get_remote_ipaddr(),
"-p", "-f", "--", pw->pw_name, NULL);
/* Login couldn't be executed, die. */
perror("login");
exit(1);
}
}
/*
* Execute the command using the user's shell. This uses the -c
* option to execute the command.
*/
argv[0] = (char *) cp;
argv[1] = "-c";
argv[2] = (char *) command;
argv[3] = NULL;
execve(shell, argv, env);
perror(shell);
exit(1);
}
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