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sshd.c
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/* $OpenBSD: sshd.c,v 1.600 2023/03/08 04:43:12 guenther Exp $ */
/*
* Author: Tatu Ylonen <[email protected]>
* Copyright (c) 1995 Tatu Ylonen <[email protected]>, Espoo, Finland
* All rights reserved
* This program is the ssh daemon. It listens for connections from clients,
* and performs authentication, executes use commands or shell, and forwards
* information to/from the application to the user client over an encrypted
* connection. This can also handle forwarding of X11, TCP/IP, and
* authentication agent connections.
*
* As far as I am concerned, the code I have written for this software
* can be used freely for any purpose. Any derived versions of this
* software must be clearly marked as such, and if the derived work is
* incompatible with the protocol description in the RFC file, it must be
* called by a name other than "ssh" or "Secure Shell".
*
* SSH2 implementation:
* Privilege Separation:
*
* Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved.
* Copyright (c) 2002 Niels Provos. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
#ifdef __APPLE_ENDPOINTSECURITY__
#include "submit-ess-event.h"
#endif
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#ifdef HAVE_SYS_STAT_H
# include <sys/stat.h>
#endif
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
#endif
#include "openbsd-compat/sys-tree.h"
#include "openbsd-compat/sys-queue.h"
#include <sys/wait.h>
#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#ifdef HAVE_PATHS_H
#include <paths.h>
#endif
#include <grp.h>
#ifdef HAVE_POLL_H
#include <poll.h>
#endif
#include <pwd.h>
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#ifdef WITH_OPENSSL
#include <openssl/dh.h>
#include <openssl/bn.h>
#include <openssl/rand.h>
#include "openbsd-compat/openssl-compat.h"
#endif
#ifdef HAVE_SECUREWARE
#include <sys/security.h>
#include <prot.h>
#endif
#ifdef __APPLE_MANAGED_CONFIGURATION__
#include <SoftLinking/WeakLinking.h>
#include <libmanagedconfigurationfiles.h>
WEAK_LINK_FORCE_IMPORT(mcf_service_path_for_service_type);
#endif
#include "xmalloc.h"
#include "ssh.h"
#include "ssh2.h"
#include "sshpty.h"
#include "packet.h"
#include "log.h"
#include "sshbuf.h"
#include "misc.h"
#include "match.h"
#include "servconf.h"
#include "uidswap.h"
#include "compat.h"
#include "cipher.h"
#include "digest.h"
#include "sshkey.h"
#include "kex.h"
#include "authfile.h"
#include "pathnames.h"
#include "atomicio.h"
#include "canohost.h"
#include "hostfile.h"
#include "auth.h"
#include "authfd.h"
#include "msg.h"
#include "dispatch.h"
#include "channels.h"
#include "session.h"
#include "monitor.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
#include "ssh-sandbox.h"
#include "auth-options.h"
#include "version.h"
#include "ssherr.h"
#include "sk-api.h"
#include "srclimit.h"
#include "dh.h"
/* Re-exec fds */
#define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1)
#define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2)
#define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3)
#define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4)
extern char *__progname;
/* Server configuration options. */
ServerOptions options;
/* Name of the server configuration file. */
char *config_file_name = _PATH_SERVER_CONFIG_FILE;
/*
* Debug mode flag. This can be set on the command line. If debug
* mode is enabled, extra debugging output will be sent to the system
* log, the daemon will not go to background, and will exit after processing
* the first connection.
*/
int debug_flag = 0;
/*
* Indicating that the daemon should only test the configuration and keys.
* If test_flag > 1 ("-T" flag), then sshd will also dump the effective
* configuration, optionally using connection information provided by the
* "-C" flag.
*/
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 */
static int log_stderr = 0;
/* Saved arguments to main(). */
static char **saved_argv;
static int saved_argc;
/* re-exec */
static int rexeced_flag = 0;
static int rexec_flag = 1;
static int rexec_argc = 0;
static char **rexec_argv;
/*
* 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;
/* Daemon's agent connection */
int auth_sock = -1;
static int have_agent = 0;
/*
* Any really sensitive data in the application is contained in this
* structure. The idea is that this structure could be locked into memory so
* that the pages do not get written into swap. However, there are some
* problems. The private key contains BIGNUMs, and we do not (in principle)
* have access to the internals of them, and locking just the structure is
* not very useful. Currently, memory locking is not implemented.
*/
struct {
struct sshkey **host_keys; /* all private host keys */
struct sshkey **host_pubkeys; /* all public host keys */
struct sshkey **host_certificates; /* all public host certificates */
int have_ssh2_key;
} sensitive_data;
/* This is set to true when a signal is received. */
static volatile sig_atomic_t received_sighup = 0;
static volatile sig_atomic_t received_sigterm = 0;
/* record remote hostname or ip */
u_int utmp_len = HOST_NAME_MAX+1;
/*
* startup_pipes/flags are used for tracking children of the listening sshd
* process early in their lifespans. This tracking is needed for three things:
*
* 1) Implementing the MaxStartups limit of concurrent unauthenticated
* connections.
* 2) Avoiding a race condition for SIGHUP processing, where child processes
* may have listen_socks open that could collide with main listener process
* after it restarts.
* 3) Ensuring that rexec'd sshd processes have received their initial state
* from the parent listen process before handling SIGHUP.
*
* Child processes signal that they have completed closure of the listen_socks
* and (if applicable) received their rexec state by sending a char over their
* sock. Child processes signal that authentication has completed by closing
* the sock (or by exiting).
*/
static int *startup_pipes = NULL;
static int *startup_flags = NULL; /* Indicates child closed listener */
static int startup_pipe = -1; /* in child */
/* variables used for privilege separation */
int use_privsep = -1;
struct monitor *pmonitor = NULL;
int privsep_is_preauth = 1;
static int privsep_chroot = 1;
/* global connection state and authentication contexts */
Authctxt *the_authctxt = NULL;
struct ssh *the_active_state;
/* global key/cert auth options. XXX move to permanent ssh->authctxt? */
struct sshauthopt *auth_opts = NULL;
/* sshd_config buffer */
struct sshbuf *cfg;
/* Included files from the configuration file */
struct include_list includes = TAILQ_HEAD_INITIALIZER(includes);
/* message to be displayed after login */
struct sshbuf *loginmsg;
/* Unprivileged user */
struct passwd *privsep_pw = NULL;
/* Prototypes for various functions defined later in this file. */
void destroy_sensitive_data(void);
void demote_sensitive_data(void);
static void do_ssh2_kex(struct ssh *);
static char *listener_proctitle;
/*
* Close all listening sockets
*/
static void
close_listen_socks(void)
{
int i;
for (i = 0; i < num_listen_socks; i++)
close(listen_socks[i]);
num_listen_socks = 0;
}
static void
close_startup_pipes(void)
{
int i;
if (startup_pipes)
for (i = 0; i < options.max_startups; i++)
if (startup_pipes[i] != -1)
close(startup_pipes[i]);
}
/*
* Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
* the effect is to reread the configuration file (and to regenerate
* the server key).
*/
static void
sighup_handler(int sig)
{
received_sighup = 1;
}
/*
* Called from the main program after receiving SIGHUP.
* Restarts the server.
*/
static void
sighup_restart(void)
{
logit("Received SIGHUP; restarting.");
if (options.pid_file != NULL)
unlink(options.pid_file);
platform_pre_restart();
close_listen_socks();
close_startup_pipes();
ssh_signal(SIGHUP, SIG_IGN); /* will be restored after exec */
execv(saved_argv[0], saved_argv);
logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
strerror(errno));
exit(1);
}
/*
* Generic signal handler for terminating signals in the master daemon.
*/
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 == -1 && errno == EINTR))
;
errno = save_errno;
}
/*
* Signal handler for the alarm after the login grace period has expired.
*/
static void
grace_alarm_handler(int sig)
{
/*
* Try to kill any processes that we have spawned, E.g. authorized
* keys command helpers or privsep children.
*/
if (getpgid(0) == getpid()) {
ssh_signal(SIGTERM, SIG_IGN);
kill(0, SIGTERM);
}
/* Log error and exit. */
sigdie("Timeout before authentication for %s port %d",
ssh_remote_ipaddr(the_active_state),
ssh_remote_port(the_active_state));
}
/* Destroy the host and server keys. They will no longer be needed. */
void
destroy_sensitive_data(void)
{
u_int i;
for (i = 0; i < options.num_host_key_files; i++) {
if (sensitive_data.host_keys[i]) {
sshkey_free(sensitive_data.host_keys[i]);
sensitive_data.host_keys[i] = NULL;
}
if (sensitive_data.host_certificates[i]) {
sshkey_free(sensitive_data.host_certificates[i]);
sensitive_data.host_certificates[i] = NULL;
}
}
}
/* Demote private to public keys for network child */
void
demote_sensitive_data(void)
{
struct sshkey *tmp;
u_int i;
int r;
for (i = 0; i < options.num_host_key_files; i++) {
if (sensitive_data.host_keys[i]) {
if ((r = sshkey_from_private(
sensitive_data.host_keys[i], &tmp)) != 0)
fatal_r(r, "could not demote host %s key",
sshkey_type(sensitive_data.host_keys[i]));
sshkey_free(sensitive_data.host_keys[i]);
sensitive_data.host_keys[i] = tmp;
}
/* Certs do not need demotion */
}
}
static void
reseed_prngs(void)
{
u_int32_t rnd[256];
#ifdef WITH_OPENSSL
RAND_poll();
#endif
arc4random_stir(); /* noop on recent arc4random() implementations */
arc4random_buf(rnd, sizeof(rnd)); /* let arc4random notice PID change */
#ifdef WITH_OPENSSL
RAND_seed(rnd, sizeof(rnd));
/* give libcrypto a chance to notice the PID change */
if ((RAND_bytes((u_char *)rnd, 1)) != 1)
fatal("%s: RAND_bytes failed", __func__);
#endif
explicit_bzero(rnd, sizeof(rnd));
}
static void
privsep_preauth_child(void)
{
gid_t gidset[1];
/* Enable challenge-response authentication for privilege separation */
privsep_challenge_enable();
#ifdef GSSAPI
/* Cache supported mechanism OIDs for later use */
ssh_gssapi_prepare_supported_oids();
#endif
reseed_prngs();
/* Demote the private keys to public keys. */
demote_sensitive_data();
/* Demote the child */
if (privsep_chroot) {
/* Change our root directory */
if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
strerror(errno));
if (chdir("/") == -1)
fatal("chdir(\"/\"): %s", strerror(errno));
/* Drop our privileges */
debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid,
(u_int)privsep_pw->pw_gid);
gidset[0] = privsep_pw->pw_gid;
if (setgroups(1, gidset) == -1)
fatal("setgroups: %.100s", strerror(errno));
permanently_set_uid(privsep_pw);
}
}
static int
privsep_preauth(struct ssh *ssh)
{
int status, r;
pid_t pid;
struct ssh_sandbox *box = NULL;
/* Set up unprivileged child process to deal with network data */
pmonitor = monitor_init();
/* Store a pointer to the kex for later rekeying */
pmonitor->m_pkex = &ssh->kex;
if (use_privsep == PRIVSEP_ON)
box = ssh_sandbox_init(pmonitor);
pid = fork();
if (pid == -1) {
fatal("fork of unprivileged child failed");
} else if (pid != 0) {
debug2("Network child is on pid %ld", (long)pid);
pmonitor->m_pid = pid;
if (have_agent) {
r = ssh_get_authentication_socket(&auth_sock);
if (r != 0) {
error_r(r, "Could not get agent socket");
have_agent = 0;
}
}
if (box != NULL)
ssh_sandbox_parent_preauth(box, pid);
monitor_child_preauth(ssh, pmonitor);
/* Wait for the child's exit status */
while (waitpid(pid, &status, 0) == -1) {
if (errno == EINTR)
continue;
pmonitor->m_pid = -1;
fatal_f("waitpid: %s", strerror(errno));
}
privsep_is_preauth = 0;
pmonitor->m_pid = -1;
if (WIFEXITED(status)) {
if (WEXITSTATUS(status) != 0)
fatal_f("preauth child exited with status %d",
WEXITSTATUS(status));
} else if (WIFSIGNALED(status))
fatal_f("preauth child terminated by signal %d",
WTERMSIG(status));
if (box != NULL)
ssh_sandbox_parent_finish(box);
return 1;
} else {
/* child */
close(pmonitor->m_sendfd);
close(pmonitor->m_log_recvfd);
/* Arrange for logging to be sent to the monitor */
set_log_handler(mm_log_handler, pmonitor);
privsep_preauth_child();
setproctitle("%s", "[net]");
if (box != NULL)
ssh_sandbox_child(box);
return 0;
}
}
static void
privsep_postauth(struct ssh *ssh, Authctxt *authctxt)
{
#ifdef DISABLE_FD_PASSING
if (1) {
#else
if (authctxt->pw->pw_uid == 0) {
#endif
/* File descriptor passing is broken or root login */
use_privsep = 0;
goto skip;
}
/* New socket pair */
monitor_reinit(pmonitor);
pmonitor->m_pid = fork();
if (pmonitor->m_pid == -1)
fatal("fork of unprivileged child failed");
else if (pmonitor->m_pid != 0) {
verbose("User child is on pid %ld", (long)pmonitor->m_pid);
sshbuf_reset(loginmsg);
monitor_clear_keystate(ssh, pmonitor);
monitor_child_postauth(ssh, pmonitor);
/* NEVERREACHED */
exit(0);
}
/* child */
close(pmonitor->m_sendfd);
pmonitor->m_sendfd = -1;
/* Demote the private keys to public keys. */
demote_sensitive_data();
reseed_prngs();
/* Drop privileges */
do_setusercontext(authctxt->pw);
skip:
/* It is safe now to apply the key state */
monitor_apply_keystate(ssh, pmonitor);
/*
* Tell the packet layer that authentication was successful, since
* this information is not part of the key state.
*/
ssh_packet_set_authenticated(ssh);
}
static void
append_hostkey_type(struct sshbuf *b, const char *s)
{
int r;
if (match_pattern_list(s, options.hostkeyalgorithms, 0) != 1) {
debug3_f("%s key not permitted by HostkeyAlgorithms", s);
return;
}
if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) > 0 ? "," : "", s)) != 0)
fatal_fr(r, "sshbuf_putf");
}
static char *
list_hostkey_types(void)
{
struct sshbuf *b;
struct sshkey *key;
char *ret;
u_int i;
if ((b = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
for (i = 0; i < options.num_host_key_files; i++) {
key = sensitive_data.host_keys[i];
if (key == NULL)
key = sensitive_data.host_pubkeys[i];
if (key == NULL)
continue;
switch (key->type) {
case KEY_RSA:
/* for RSA we also support SHA2 signatures */
append_hostkey_type(b, "rsa-sha2-512");
append_hostkey_type(b, "rsa-sha2-256");
/* FALLTHROUGH */
case KEY_DSA:
case KEY_ECDSA:
case KEY_ED25519:
case KEY_ECDSA_SK:
case KEY_ED25519_SK:
case KEY_XMSS:
append_hostkey_type(b, sshkey_ssh_name(key));
break;
}
/* If the private key has a cert peer, then list that too */
key = sensitive_data.host_certificates[i];
if (key == NULL)
continue;
switch (key->type) {
case KEY_RSA_CERT:
/* for RSA we also support SHA2 signatures */
append_hostkey_type(b,
append_hostkey_type(b,
/* FALLTHROUGH */
case KEY_DSA_CERT:
case KEY_ECDSA_CERT:
case KEY_ED25519_CERT:
case KEY_ECDSA_SK_CERT:
case KEY_ED25519_SK_CERT:
case KEY_XMSS_CERT:
append_hostkey_type(b, sshkey_ssh_name(key));
break;
}
}
if ((ret = sshbuf_dup_string(b)) == NULL)
fatal_f("sshbuf_dup_string failed");
sshbuf_free(b);
debug_f("%s", ret);
return ret;
}
static struct sshkey *
get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh)
{
u_int i;
struct sshkey *key;
for (i = 0; i < options.num_host_key_files; i++) {
switch (type) {
case KEY_RSA_CERT:
case KEY_DSA_CERT:
case KEY_ECDSA_CERT:
case KEY_ED25519_CERT:
case KEY_ECDSA_SK_CERT:
case KEY_ED25519_SK_CERT:
case KEY_XMSS_CERT:
key = sensitive_data.host_certificates[i];
break;
default:
key = sensitive_data.host_keys[i];
if (key == NULL && !need_private)
key = sensitive_data.host_pubkeys[i];
break;
}
if (key == NULL || key->type != type)
continue;
switch (type) {
case KEY_ECDSA:
case KEY_ECDSA_SK:
case KEY_ECDSA_CERT:
case KEY_ECDSA_SK_CERT:
if (key->ecdsa_nid != nid)
continue;
/* FALLTHROUGH */
default:
return need_private ?
sensitive_data.host_keys[i] : key;
}
}
return NULL;
}
struct sshkey *
get_hostkey_public_by_type(int type, int nid, struct ssh *ssh)
{
return get_hostkey_by_type(type, nid, 0, ssh);
}
struct sshkey *
get_hostkey_private_by_type(int type, int nid, struct ssh *ssh)
{
return get_hostkey_by_type(type, nid, 1, ssh);
}
struct sshkey *
get_hostkey_by_index(int ind)
{
if (ind < 0 || (u_int)ind >= options.num_host_key_files)
return (NULL);
return (sensitive_data.host_keys[ind]);
}
struct sshkey *
get_hostkey_public_by_index(int ind, struct ssh *ssh)
{
if (ind < 0 || (u_int)ind >= options.num_host_key_files)
return (NULL);
return (sensitive_data.host_pubkeys[ind]);
}
int
get_hostkey_index(struct sshkey *key, int compare, struct ssh *ssh)
{
u_int i;
for (i = 0; i < options.num_host_key_files; i++) {
if (sshkey_is_cert(key)) {
if (key == sensitive_data.host_certificates[i] ||
(compare && sensitive_data.host_certificates[i] &&
sshkey_equal(key,
sensitive_data.host_certificates[i])))
return (i);
} else {
if (key == sensitive_data.host_keys[i] ||
(compare && sensitive_data.host_keys[i] &&
sshkey_equal(key, sensitive_data.host_keys[i])))
return (i);
if (key == sensitive_data.host_pubkeys[i] ||
(compare && sensitive_data.host_pubkeys[i] &&
sshkey_equal(key, sensitive_data.host_pubkeys[i])))
return (i);
}
}
return (-1);
}
/* Inform the client of all hostkeys */
static void
notify_hostkeys(struct ssh *ssh)
{
struct sshbuf *buf;
struct sshkey *key;
u_int i, nkeys;
int r;
char *fp;
/* Some clients cannot cope with the hostkeys message, skip those. */
if (ssh->compat & SSH_BUG_HOSTKEYS)
return;
if ((buf = sshbuf_new()) == NULL)
fatal_f("sshbuf_new");
for (i = nkeys = 0; i < options.num_host_key_files; i++) {
key = get_hostkey_public_by_index(i, ssh);
if (key == NULL || key->type == KEY_UNSPEC ||
sshkey_is_cert(key))
continue;
fp = sshkey_fingerprint(key, options.fingerprint_hash,
SSH_FP_DEFAULT);
debug3_f("key %d: %s %s", i, sshkey_ssh_name(key), fp);
free(fp);
if (nkeys == 0) {
/*
* Start building the request when we find the
* first usable key.
*/
if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
(r = sshpkt_put_cstring(ssh, "[email protected]")) != 0 ||
(r = sshpkt_put_u8(ssh, 0)) != 0) /* want reply */
sshpkt_fatal(ssh, r, "%s: start request", __func__);
}
/* Append the key to the request */
sshbuf_reset(buf);
if ((r = sshkey_putb(key, buf)) != 0)
fatal_fr(r, "couldn't put hostkey %d", i);
if ((r = sshpkt_put_stringb(ssh, buf)) != 0)
sshpkt_fatal(ssh, r, "%s: append key", __func__);
nkeys++;
}
debug3_f("sent %u hostkeys", nkeys);
if (nkeys == 0)
fatal_f("no hostkeys");
if ((r = sshpkt_send(ssh)) != 0)
sshpkt_fatal(ssh, r, "%s: send", __func__);
sshbuf_free(buf);
}
/*
* returns 1 if connection should be dropped, 0 otherwise.
* dropping starts at connection #max_startups_begin with a probability
* of (max_startups_rate/100). the probability increases linearly until
* all connections are dropped for startups > max_startups
*/
static int
should_drop_connection(int startups)
{
int p, r;
if (startups < options.max_startups_begin)
return 0;
if (startups >= options.max_startups)
return 1;
if (options.max_startups_rate == 100)
return 1;
p = 100 - options.max_startups_rate;
p *= startups - options.max_startups_begin;
p /= options.max_startups - options.max_startups_begin;
p += options.max_startups_rate;
r = arc4random_uniform(100);
debug_f("p %d, r %d", p, r);
return (r < p) ? 1 : 0;
}
/*
* Check whether connection should be accepted by MaxStartups.
* Returns 0 if the connection is accepted. If the connection is refused,
* returns 1 and attempts to send notification to client.
* Logs when the MaxStartups condition is entered or exited, and periodically
* while in that state.
*/
static int
drop_connection(int sock, int startups, int notify_pipe)
{
char *laddr, *raddr;
const char msg[] = "Exceeded MaxStartups\r\n";
static time_t last_drop, first_drop;
static u_int ndropped;
LogLevel drop_level = SYSLOG_LEVEL_VERBOSE;
time_t now;
now = monotime();
if (!should_drop_connection(startups) &&
srclimit_check_allow(sock, notify_pipe) == 1) {
if (last_drop != 0 &&
startups < options.max_startups_begin - 1) {
/* XXX maybe need better hysteresis here */
logit("exited MaxStartups throttling after %s, "
"%u connections dropped",
fmt_timeframe(now - first_drop), ndropped);
last_drop = 0;
}
return 0;
}
#define SSHD_MAXSTARTUPS_LOG_INTERVAL (5 * 60)
if (last_drop == 0) {
error("beginning MaxStartups throttling");
drop_level = SYSLOG_LEVEL_INFO;
first_drop = now;
ndropped = 0;
} else if (last_drop + SSHD_MAXSTARTUPS_LOG_INTERVAL < now) {
/* Periodic logs */
error("in MaxStartups throttling for %s, "
"%u connections dropped",
fmt_timeframe(now - first_drop), ndropped + 1);
drop_level = SYSLOG_LEVEL_INFO;
}
last_drop = now;
ndropped++;
laddr = get_local_ipaddr(sock);
raddr = get_peer_ipaddr(sock);
do_log2(drop_level, "drop connection #%d from [%s]:%d on [%s]:%d "
"past MaxStartups", startups, raddr, get_peer_port(sock),
laddr, get_local_port(sock));
free(laddr);
free(raddr);
/* best-effort notification to client */
(void)write(sock, msg, sizeof(msg) - 1);
return 1;
}
static void
usage(void)
{
fprintf(stderr, "%s, %s\n", SSH_RELEASE, SSH_OPENSSL_VERSION);
fprintf(stderr,
"usage: sshd [-46DdeGiqTtV] [-C connection_spec] [-c host_cert_file]\n"
" [-E log_file] [-f config_file] [-g login_grace_time]\n"
" [-h host_key_file] [-o option] [-p port] [-u len]\n"
);
exit(1);
}
static void
send_rexec_state(int fd, struct sshbuf *conf)
{
struct sshbuf *m = NULL, *inc = NULL;
struct include_item *item = NULL;
int r;
debug3_f("entering fd = %d config len %zu", fd,
sshbuf_len(conf));
if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
/* pack includes into a string */
TAILQ_FOREACH(item, &includes, entry) {
if ((r = sshbuf_put_cstring(inc, item->selector)) != 0 ||
(r = sshbuf_put_cstring(inc, item->filename)) != 0 ||
(r = sshbuf_put_stringb(inc, item->contents)) != 0)
fatal_fr(r, "compose includes");
}
/*
* Protocol from reexec master to child:
* string configuration
* string included_files[] {
* string selector
* string filename
* string contents
* }
*/
if ((r = sshbuf_put_stringb(m, conf)) != 0 ||
(r = sshbuf_put_stringb(m, inc)) != 0)
fatal_fr(r, "compose config");
if (ssh_msg_send(fd, 0, m) == -1)
error_f("ssh_msg_send failed");
sshbuf_free(m);
sshbuf_free(inc);
debug3_f("done");
}
static void
recv_rexec_state(int fd, struct sshbuf *conf)
{
struct sshbuf *m, *inc;
u_char *cp, ver;
size_t len;
int r;
struct include_item *item;
debug3_f("entering fd = %d", fd);
if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
if (ssh_msg_recv(fd, m) == -1)
fatal_f("ssh_msg_recv failed");
if ((r = sshbuf_get_u8(m, &ver)) != 0)
fatal_fr(r, "parse version");
if (ver != 0)
fatal_f("rexec version mismatch");
if ((r = sshbuf_get_string(m, &cp, &len)) != 0 ||
(r = sshbuf_get_stringb(m, inc)) != 0)
fatal_fr(r, "parse config");
if (conf != NULL && (r = sshbuf_put(conf, cp, len)))
fatal_fr(r, "sshbuf_put");
while (sshbuf_len(inc) != 0) {
item = xcalloc(1, sizeof(*item));
if ((item->contents = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
if ((r = sshbuf_get_cstring(inc, &item->selector, NULL)) != 0 ||
(r = sshbuf_get_cstring(inc, &item->filename, NULL)) != 0 ||
(r = sshbuf_get_stringb(inc, item->contents)) != 0)
fatal_fr(r, "parse includes");
TAILQ_INSERT_TAIL(&includes, item, entry);
}
free(cp);
sshbuf_free(m);
debug3_f("done");
}