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openssh-portable/sshd-session.c

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/* $OpenBSD: sshd-session.c,v 1.3 2024/06/06 17:15:25 djm Exp $ */
/*
* 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"
#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 <pwd.h>
#include <grp.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <unistd.h>
#include <limits.h>
#ifdef WITH_OPENSSL
#include <openssl/bn.h>
#include <openssl/evp.h>
#include <openssl/rand.h>
#include "openbsd-compat/openssl-compat.h"
#endif
#ifdef HAVE_SECUREWARE
#include <sys/security.h>
#include <prot.h>
#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;
/* Flag indicating that the daemon is being started from inetd. */
static int inetd_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;
/* 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 {
u_int num_hostkeys;
struct sshkey **host_keys; /* all private host keys */
struct sshkey **host_pubkeys; /* all public host keys */
struct sshkey **host_certificates; /* all public host certificates */
} sensitive_data;
/* record remote hostname or ip */
u_int utmp_len = HOST_NAME_MAX+1;
static int startup_pipe = -1; /* in child */
/* variables used for privilege separation */
struct monitor *pmonitor = NULL;
int privsep_is_preauth = 1;
static int privsep_chroot = 1;
/* Unprivileged user */
struct passwd *privsep_pw = NULL;
/* 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;
/* 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 *);
/*
* 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);
}
_exit(EXIT_LOGIN_GRACE);
}
/* 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;
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)
{
int skip_privdrop = 0;
/*
* Hack for systems that don't support FD passing: retain privileges
* in the post-auth privsep process so it can allocate PTYs directly.
* This is basically equivalent to what we did <= 9.7, which was to
* disable post-auth privsep entriely.
* Cygwin doesn't need to drop privs here although it doesn't support
* fd passing, as AFAIK PTY allocation on this platform doesn't require
* special privileges to begin with.
*/
#if defined(DISABLE_FD_PASSING) && !defined(HAVE_CYGWIN)
skip_privdrop = 1;
#endif
/* 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 */
if (!skip_privdrop)
do_setusercontext(authctxt->pw);
/* 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,
"rsa-sha2-512-cert-v01@openssh.com");
append_hostkey_type(b,
"rsa-sha2-256-cert-v01@openssh.com");
/* 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, "hostkeys-00@openssh.com")) != 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);
}
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
parse_hostkeys(struct sshbuf *hostkeys)
{
int r;
u_int num_keys = 0;
struct sshkey *k;
struct sshbuf *kbuf;
const u_char *cp;
size_t len;
while (sshbuf_len(hostkeys) != 0) {
if (num_keys > 2048)
fatal_f("too many hostkeys");
sensitive_data.host_keys = xrecallocarray(
sensitive_data.host_keys, num_keys, num_keys + 1,
sizeof(*sensitive_data.host_pubkeys));
sensitive_data.host_pubkeys = xrecallocarray(
sensitive_data.host_pubkeys, num_keys, num_keys + 1,
sizeof(*sensitive_data.host_pubkeys));
sensitive_data.host_certificates = xrecallocarray(
sensitive_data.host_certificates, num_keys, num_keys + 1,
sizeof(*sensitive_data.host_certificates));
/* private key */
k = NULL;
if ((r = sshbuf_froms(hostkeys, &kbuf)) != 0)
fatal_fr(r, "extract privkey");
if (sshbuf_len(kbuf) != 0 &&
(r = sshkey_private_deserialize(kbuf, &k)) != 0)
fatal_fr(r, "parse pubkey");
sensitive_data.host_keys[num_keys] = k;
sshbuf_free(kbuf);
if (k)
debug2_f("privkey %u: %s", num_keys, sshkey_ssh_name(k));
/* public key */
k = NULL;
if ((r = sshbuf_get_string_direct(hostkeys, &cp, &len)) != 0)
fatal_fr(r, "extract pubkey");
if (len != 0 && (r = sshkey_from_blob(cp, len, &k)) != 0)
fatal_fr(r, "parse pubkey");
sensitive_data.host_pubkeys[num_keys] = k;
if (k)
debug2_f("pubkey %u: %s", num_keys, sshkey_ssh_name(k));
/* certificate */
k = NULL;
if ((r = sshbuf_get_string_direct(hostkeys, &cp, &len)) != 0)
fatal_fr(r, "extract pubkey");
if (len != 0 && (r = sshkey_from_blob(cp, len, &k)) != 0)
fatal_fr(r, "parse pubkey");
sensitive_data.host_certificates[num_keys] = k;
if (k)
debug2_f("cert %u: %s", num_keys, sshkey_ssh_name(k));
num_keys++;
}
sensitive_data.num_hostkeys = num_keys;
}
static void
recv_rexec_state(int fd, struct sshbuf *conf, uint64_t *timing_secretp)
{
struct sshbuf *m, *inc, *hostkeys;
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 || /* XXX _direct */
(r = sshbuf_get_u64(m, timing_secretp)) != 0 ||
(r = sshbuf_froms(m, &hostkeys)) != 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);
}
parse_hostkeys(hostkeys);
free(cp);
sshbuf_free(m);
sshbuf_free(hostkeys);
sshbuf_free(inc);
debug3_f("done");
}
/*
* If IP options are supported, make sure there are none (log and
* return an error if any are found). Basically we are worried about
* source routing; it can be used to pretend you are somebody
* (ip-address) you are not. That itself may be "almost acceptable"
* under certain circumstances, but rhosts authentication is useless
* if source routing is accepted. Notice also that if we just dropped
* source routing here, the other side could use IP spoofing to do
* rest of the interaction and could still bypass security. So we
* exit here if we detect any IP options.
*/
static void
check_ip_options(struct ssh *ssh)
{
#ifdef IP_OPTIONS
int sock_in = ssh_packet_get_connection_in(ssh);
struct sockaddr_storage from;
u_char opts[200];
socklen_t i, option_size = sizeof(opts), fromlen = sizeof(from);
char text[sizeof(opts) * 3 + 1];
memset(&from, 0, sizeof(from));
if (getpeername(sock_in, (struct sockaddr *)&from,
&fromlen) == -1)
return;
if (from.ss_family != AF_INET)
return;
/* XXX IPv6 options? */
if (getsockopt(sock_in, IPPROTO_IP, IP_OPTIONS, opts,
&option_size) >= 0 && option_size != 0) {
text[0] = '\0';
for (i = 0; i < option_size; i++)
snprintf(text + i*3, sizeof(text) - i*3,
" %2.2x", opts[i]);
fatal("Connection from %.100s port %d with IP opts: %.800s",
ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), text);
}
return;
#endif /* IP_OPTIONS */
}
/* Set the routing domain for this process */
static void
set_process_rdomain(struct ssh *ssh, const char *name)
{
#if defined(HAVE_SYS_SET_PROCESS_RDOMAIN)
if (name == NULL)
return; /* default */
if (strcmp(name, "%D") == 0) {
/* "expands" to routing domain of connection */
if ((name = ssh_packet_rdomain_in(ssh)) == NULL)
return;
}
/* NB. We don't pass 'ssh' to sys_set_process_rdomain() */
return sys_set_process_rdomain(name);
#elif defined(__OpenBSD__)
int rtable, ortable = getrtable();
const char *errstr;
if (name == NULL)
return; /* default */
if (strcmp(name, "%D") == 0) {
/* "expands" to routing domain of connection */
if ((name = ssh_packet_rdomain_in(ssh)) == NULL)
return;
}
rtable = (int)strtonum(name, 0, 255, &errstr);
if (errstr != NULL) /* Shouldn't happen */
fatal("Invalid routing domain \"%s\": %s", name, errstr);
if (rtable != ortable && setrtable(rtable) != 0)
fatal("Unable to set routing domain %d: %s",
rtable, strerror(errno));
debug_f("set routing domain %d (was %d)", rtable, ortable);
#else /* defined(__OpenBSD__) */
fatal("Unable to set routing domain: not supported in this platform");
#endif
}
/*
* Main program for the daemon.
*/
int
main(int ac, char **av)
{
struct ssh *ssh = NULL;
extern char *optarg;
extern int optind;
int r, opt, on = 1, remote_port;
int sock_in = -1, sock_out = -1, rexeced_flag = 0, have_key = 0;
const char *remote_ip, *rdomain;
char *line, *laddr, *logfile = NULL;
u_int i;
u_int64_t ibytes, obytes;
mode_t new_umask;
Authctxt *authctxt;
struct connection_info *connection_info = NULL;
sigset_t sigmask;
uint64_t timing_secret = 0;
sigemptyset(&sigmask);
sigprocmask(SIG_SETMASK, &sigmask, NULL);
#ifdef HAVE_SECUREWARE
(void)set_auth_parameters(ac, av);
#endif
__progname = ssh_get_progname(av[0]);
/* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
saved_argc = ac;
saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
for (i = 0; (int)i < ac; i++)
saved_argv[i] = xstrdup(av[i]);
saved_argv[i] = NULL;
#ifndef HAVE_SETPROCTITLE
/* Prepare for later setproctitle emulation */
compat_init_setproctitle(ac, av);
av = saved_argv;
#endif
/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
sanitise_stdfd();
/* Initialize configuration options to their default values. */
initialize_server_options(&options);
/* Parse command-line arguments. */
while ((opt = getopt(ac, av,
"C:E:b:c:f:g:h:k:o:p:u:46DGQRTdeiqrtV")) != -1) {
switch (opt) {
case '4':
options.address_family = AF_INET;
break;
case '6':
options.address_family = AF_INET6;
break;
case 'f':
config_file_name = optarg;
break;
case 'c':
servconf_add_hostcert("[command-line]", 0,
&options, optarg);
break;
case 'd':
if (debug_flag == 0) {
debug_flag = 1;
options.log_level = SYSLOG_LEVEL_DEBUG1;
} else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
options.log_level++;
break;
case 'D':
/* ignore */
break;
case 'E':
logfile = optarg;
/* FALLTHROUGH */
case 'e':
log_stderr = 1;
break;
case 'i':
inetd_flag = 1;
break;
case 'r':
/* ignore */
break;
case 'R':
rexeced_flag = 1;
break;
case 'Q':
/* ignored */
break;
case 'q':
options.log_level = SYSLOG_LEVEL_QUIET;
break;
case 'b':
/* protocol 1, ignored */
break;
case 'p':
options.ports_from_cmdline = 1;
if (options.num_ports >= MAX_PORTS) {
fprintf(stderr, "too many ports.\n");
exit(1);
}
options.ports[options.num_ports++] = a2port(optarg);
if (options.ports[options.num_ports-1] <= 0) {
fprintf(stderr, "Bad port number.\n");
exit(1);
}
break;
case 'g':
if ((options.login_grace_time = convtime(optarg)) == -1) {
fprintf(stderr, "Invalid login grace time.\n");
exit(1);
}
break;
case 'k':
/* protocol 1, ignored */
break;
case 'h':
servconf_add_hostkey("[command-line]", 0,
&options, optarg, 1);
break;
case 't':
case 'T':
case 'G':
fatal("test/dump modes not supported");
break;
case 'C':
connection_info = server_get_connection_info(ssh, 0, 0);
if (parse_server_match_testspec(connection_info,
optarg) == -1)
exit(1);
break;
case 'u':
utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL);
if (utmp_len > HOST_NAME_MAX+1) {
fprintf(stderr, "Invalid utmp length.\n");
exit(1);
}
break;
case 'o':
line = xstrdup(optarg);
if (process_server_config_line(&options, line,
"command-line", 0, NULL, NULL, &includes) != 0)
exit(1);
free(line);
break;
case 'V':
fprintf(stderr, "%s, %s\n",
SSH_RELEASE, SSH_OPENSSL_VERSION);
exit(0);
default:
usage();
break;
}
}
/* Check that there are no remaining arguments. */
if (optind < ac) {
fprintf(stderr, "Extra argument %s.\n", av[optind]);
exit(1);
}
debug("sshd version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION);
if (!rexeced_flag)
fatal("sshd-session should not be executed directly");
closefrom(REEXEC_MIN_FREE_FD);
seed_rng();
/* If requested, redirect the logs to the specified logfile. */
if (logfile != NULL) {
char *cp, pid_s[32];
snprintf(pid_s, sizeof(pid_s), "%ld", (unsigned long)getpid());
cp = percent_expand(logfile,
"p", pid_s,
"P", "sshd-session",
(char *)NULL);
log_redirect_stderr_to(cp);
free(cp);
}
/*
* Force logging to stderr until we have loaded the private host
* key (unless started from inetd)
*/
log_init(__progname,
options.log_level == SYSLOG_LEVEL_NOT_SET ?
SYSLOG_LEVEL_INFO : options.log_level,
options.log_facility == SYSLOG_FACILITY_NOT_SET ?
SYSLOG_FACILITY_AUTH : options.log_facility,
log_stderr || !inetd_flag || debug_flag);
debug("sshd version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION);
/* Fetch our configuration */
if ((cfg = sshbuf_new()) == NULL)
fatal("sshbuf_new config buf failed");
setproctitle("%s", "[rexeced]");
recv_rexec_state(REEXEC_CONFIG_PASS_FD, cfg, &timing_secret);
close(REEXEC_CONFIG_PASS_FD);
parse_server_config(&options, "rexec", cfg, &includes, NULL, 1);
/* Fill in default values for those options not explicitly set. */
fill_default_server_options(&options);
options.timing_secret = timing_secret;
/* Store privilege separation user for later use if required. */
privsep_chroot = (getuid() == 0 || geteuid() == 0);
if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) {
if (privsep_chroot || options.kerberos_authentication)
fatal("Privilege separation user %s does not exist",
SSH_PRIVSEP_USER);
} else {
privsep_pw = pwcopy(privsep_pw);
freezero(privsep_pw->pw_passwd, strlen(privsep_pw->pw_passwd));
privsep_pw->pw_passwd = xstrdup("*");
}
endpwent();
if (!debug_flag) {
startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
close(REEXEC_STARTUP_PIPE_FD);
/*
* Signal parent that this child is at a point where
* they can go away if they have a SIGHUP pending.
*/
(void)atomicio(vwrite, startup_pipe, "\0", 1);
}
/* Check that options are sensible */
if (options.authorized_keys_command_user == NULL &&
(options.authorized_keys_command != NULL &&
strcasecmp(options.authorized_keys_command, "none") != 0))
fatal("AuthorizedKeysCommand set without "
"AuthorizedKeysCommandUser");
if (options.authorized_principals_command_user == NULL &&
(options.authorized_principals_command != NULL &&
strcasecmp(options.authorized_principals_command, "none") != 0))
fatal("AuthorizedPrincipalsCommand set without "
"AuthorizedPrincipalsCommandUser");
/*
* Check whether there is any path through configured auth methods.
* Unfortunately it is not possible to verify this generally before
* daemonisation in the presence of Match block, but this catches
* and warns for trivial misconfigurations that could break login.
*/
if (options.num_auth_methods != 0) {
for (i = 0; i < options.num_auth_methods; i++) {
if (auth2_methods_valid(options.auth_methods[i],
1) == 0)
break;
}
if (i >= options.num_auth_methods)
fatal("AuthenticationMethods cannot be satisfied by "
"enabled authentication methods");
}
#ifdef WITH_OPENSSL
if (options.moduli_file != NULL)
dh_set_moduli_file(options.moduli_file);
#endif
if (options.host_key_agent) {
if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME))
setenv(SSH_AUTHSOCKET_ENV_NAME,
options.host_key_agent, 1);
if ((r = ssh_get_authentication_socket(NULL)) == 0)
have_agent = 1;
else
error_r(r, "Could not connect to agent \"%s\"",
options.host_key_agent);
}
if (options.num_host_key_files != sensitive_data.num_hostkeys) {
fatal("internal error: hostkeys confused (config %u recvd %u)",
options.num_host_key_files, sensitive_data.num_hostkeys);
}
for (i = 0; i < options.num_host_key_files; i++) {
if (sensitive_data.host_keys[i] != NULL ||
(have_agent && sensitive_data.host_pubkeys[i] != NULL)) {
have_key = 1;
break;
}
}
if (!have_key)
fatal("internal error: monitor received no hostkeys");
/* Ensure that umask disallows at least group and world write */
new_umask = umask(0077) | 0022;
(void) umask(new_umask);
/* Initialize the log (it is reinitialized below in case we forked). */
if (debug_flag)
log_stderr = 1;
log_init(__progname, options.log_level,
options.log_facility, log_stderr);
for (i = 0; i < options.num_log_verbose; i++)
log_verbose_add(options.log_verbose[i]);
/* Reinitialize the log (because of the fork above). */
log_init(__progname, options.log_level, options.log_facility, log_stderr);
/*
* Chdir to the root directory so that the current disk can be
* unmounted if desired.
*/
if (chdir("/") == -1)
error("chdir(\"/\"): %s", strerror(errno));
/* ignore SIGPIPE */
ssh_signal(SIGPIPE, SIG_IGN);
/* Get a connection, either from inetd or rexec */
if (inetd_flag) {
/*
* NB. must be different fd numbers for the !socket case,
* as packet_connection_is_on_socket() depends on this.
*/
sock_in = dup(STDIN_FILENO);
sock_out = dup(STDOUT_FILENO);
} else {
/* rexec case; accept()ed socket in ancestor listener */
sock_in = sock_out = dup(STDIN_FILENO);
}
/*
* We intentionally do not close the descriptors 0, 1, and 2
* as our code for setting the descriptors won't work if
* ttyfd happens to be one of those.
*/
if (stdfd_devnull(1, 1, !log_stderr) == -1)
error("stdfd_devnull failed");
debug("network sockets: %d, %d", sock_in, sock_out);
/* This is the child processing a new connection. */
setproctitle("%s", "[accepted]");
/* Executed child processes don't need these. */
fcntl(sock_out, F_SETFD, FD_CLOEXEC);
fcntl(sock_in, F_SETFD, FD_CLOEXEC);
/* We will not restart on SIGHUP since it no longer makes sense. */
ssh_signal(SIGALRM, SIG_DFL);
ssh_signal(SIGHUP, SIG_DFL);
ssh_signal(SIGTERM, SIG_DFL);
ssh_signal(SIGQUIT, SIG_DFL);
ssh_signal(SIGCHLD, SIG_DFL);
ssh_signal(SIGINT, SIG_DFL);
/*
* Register our connection. This turns encryption off because we do
* not have a key.
*/
if ((ssh = ssh_packet_set_connection(NULL, sock_in, sock_out)) == NULL)
fatal("Unable to create connection");
the_active_state = ssh;
ssh_packet_set_server(ssh);
check_ip_options(ssh);
/* Prepare the channels layer */
channel_init_channels(ssh);
channel_set_af(ssh, options.address_family);
server_process_channel_timeouts(ssh);
server_process_permitopen(ssh);
/* Set SO_KEEPALIVE if requested. */
if (options.tcp_keep_alive && ssh_packet_connection_is_on_socket(ssh) &&
setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) == -1)
error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
if ((remote_port = ssh_remote_port(ssh)) < 0) {
debug("ssh_remote_port failed");
cleanup_exit(255);
}
/*
* The rest of the code depends on the fact that
* ssh_remote_ipaddr() caches the remote ip, even if
* the socket goes away.
*/
remote_ip = ssh_remote_ipaddr(ssh);
#ifdef SSH_AUDIT_EVENTS
audit_connection_from(remote_ip, remote_port);
#endif
rdomain = ssh_packet_rdomain_in(ssh);
/* Log the connection. */
laddr = get_local_ipaddr(sock_in);
verbose("Connection from %s port %d on %s port %d%s%s%s",
remote_ip, remote_port, laddr, ssh_local_port(ssh),
rdomain == NULL ? "" : " rdomain \"",
rdomain == NULL ? "" : rdomain,
rdomain == NULL ? "" : "\"");
free(laddr);
/*
* 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.
*/
ssh_signal(SIGALRM, grace_alarm_handler);
if (!debug_flag)
alarm(options.login_grace_time);
if ((r = kex_exchange_identification(ssh, -1,
options.version_addendum)) != 0)
sshpkt_fatal(ssh, r, "banner exchange");
ssh_packet_set_nonblocking(ssh);
/* allocate authentication context */
authctxt = xcalloc(1, sizeof(*authctxt));
ssh->authctxt = authctxt;
/* XXX global for cleanup, access from other modules */
the_authctxt = authctxt;
/* Set default key authentication options */
if ((auth_opts = sshauthopt_new_with_keys_defaults()) == NULL)
fatal("allocation failed");
/* prepare buffer to collect messages to display to user after login */
if ((loginmsg = sshbuf_new()) == NULL)
fatal("sshbuf_new loginmsg failed");
auth_debug_reset();
if (privsep_preauth(ssh) == 1)
goto authenticated;
/* perform the key exchange */
/* authenticate user and start session */
do_ssh2_kex(ssh);
do_authentication2(ssh);
/*
* The unprivileged child now transfers the current keystate and exits.
*/
mm_send_keystate(ssh, pmonitor);
ssh_packet_clear_keys(ssh);
exit(0);
authenticated:
/*
* Cancel the alarm we set to limit the time taken for
* authentication.
*/
alarm(0);
ssh_signal(SIGALRM, SIG_DFL);
authctxt->authenticated = 1;
if (startup_pipe != -1) {
/* signal listener that authentication completed successfully */
(void)atomicio(vwrite, startup_pipe, "\001", 1);
close(startup_pipe);
startup_pipe = -1;
}
if (options.routing_domain != NULL)
set_process_rdomain(ssh, options.routing_domain);
#ifdef SSH_AUDIT_EVENTS
audit_event(ssh, SSH_AUTH_SUCCESS);
#endif
#ifdef GSSAPI
if (options.gss_authentication) {
temporarily_use_uid(authctxt->pw);
ssh_gssapi_storecreds();
restore_uid();
}
#endif
#ifdef USE_PAM
if (options.use_pam) {
do_pam_setcred();
do_pam_session(ssh);
}
#endif
/*
* In privilege separation, we fork another child and prepare
* file descriptor passing.
*/
privsep_postauth(ssh, authctxt);
/* the monitor process [priv] will not return */
ssh_packet_set_timeout(ssh, options.client_alive_interval,
options.client_alive_count_max);
/* Try to send all our hostkeys to the client */
notify_hostkeys(ssh);
/* Start session. */
do_authenticated(ssh, authctxt);
/* The connection has been terminated. */
ssh_packet_get_bytes(ssh, &ibytes, &obytes);
verbose("Transferred: sent %llu, received %llu bytes",
(unsigned long long)obytes, (unsigned long long)ibytes);
verbose("Closing connection to %.500s port %d", remote_ip, remote_port);
#ifdef USE_PAM
if (options.use_pam)
finish_pam();
#endif /* USE_PAM */
#ifdef SSH_AUDIT_EVENTS
mm_audit_event(ssh, SSH_CONNECTION_CLOSE);
#endif
ssh_packet_close(ssh);
mm_terminate();
exit(0);
}
int
sshd_hostkey_sign(struct ssh *ssh, struct sshkey *privkey,
struct sshkey *pubkey, u_char **signature, size_t *slenp,
const u_char *data, size_t dlen, const char *alg)
{
if (privkey) {
if (mm_sshkey_sign(ssh, privkey, signature, slenp,
data, dlen, alg, options.sk_provider, NULL,
ssh->compat) < 0)
fatal_f("privkey sign failed");
} else {
if (mm_sshkey_sign(ssh, pubkey, signature, slenp,
data, dlen, alg, options.sk_provider, NULL,
ssh->compat) < 0)
fatal_f("pubkey sign failed");
}
return 0;
}
/* SSH2 key exchange */
static void
do_ssh2_kex(struct ssh *ssh)
{
char *hkalgs = NULL, *myproposal[PROPOSAL_MAX];
const char *compression = NULL;
struct kex *kex;
int r;
if (options.rekey_limit || options.rekey_interval)
ssh_packet_set_rekey_limits(ssh, options.rekey_limit,
options.rekey_interval);
if (options.compression == COMP_NONE)
compression = "none";
hkalgs = list_hostkey_types();
kex_proposal_populate_entries(ssh, myproposal, options.kex_algorithms,
options.ciphers, options.macs, compression, hkalgs);
free(hkalgs);
/* start key exchange */
if ((r = kex_setup(ssh, myproposal)) != 0)
fatal_r(r, "kex_setup");
kex_set_server_sig_algs(ssh, options.pubkey_accepted_algos);
kex = ssh->kex;
#ifdef WITH_OPENSSL
kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;
kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;
kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
#ifdef OPENSSL_HAS_ECC
kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
#endif
#endif
kex->kex[KEX_C25519_SHA256] = kex_gen_server;
kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server;
kex->load_host_public_key=&get_hostkey_public_by_type;
kex->load_host_private_key=&get_hostkey_private_by_type;
kex->host_key_index=&get_hostkey_index;
kex->sign = sshd_hostkey_sign;
ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &kex->done);
kex_proposal_free_entries(myproposal);
#ifdef DEBUG_KEXDH
/* send 1st encrypted/maced/compressed message */
if ((r = sshpkt_start(ssh, SSH2_MSG_IGNORE)) != 0 ||
(r = sshpkt_put_cstring(ssh, "markus")) != 0 ||
(r = sshpkt_send(ssh)) != 0 ||
(r = ssh_packet_write_wait(ssh)) != 0)
fatal_fr(r, "send test");
#endif
debug("KEX done");
}
/* server specific fatal cleanup */
void
cleanup_exit(int i)
{
extern int auth_attempted; /* monitor.c */
if (the_active_state != NULL && the_authctxt != NULL) {
do_cleanup(the_active_state, the_authctxt);
if (privsep_is_preauth &&
pmonitor != NULL && pmonitor->m_pid > 1) {
debug("Killing privsep child %d", pmonitor->m_pid);
if (kill(pmonitor->m_pid, SIGKILL) != 0 &&
errno != ESRCH) {
error_f("kill(%d): %s", pmonitor->m_pid,
strerror(errno));
}
}
}
/* Override default fatal exit value when auth was attempted */
if (i == 255 && auth_attempted)
_exit(EXIT_AUTH_ATTEMPTED);
#ifdef SSH_AUDIT_EVENTS
/* done after do_cleanup so it can cancel the PAM auth 'thread' */
if (the_active_state != NULL && mm_is_monitor())
audit_event(the_active_state, SSH_CONNECTION_ABANDON);
#endif
_exit(i);
}
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