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openssh/serverloop.c

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/* $OpenBSD: serverloop.c,v 1.230 2022/01/06 21:55:23 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
* Server main loop for handling the interactive session.
*
* 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 support by Markus Friedl.
* Copyright (c) 2000, 2001 Markus Friedl. 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/wait.h>
#include <sys/socket.h>
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
#endif
#include <netinet/in.h>
#include <errno.h>
#include <fcntl.h>
#include <pwd.h>
#include <limits.h>
#include <poll.h>
#include <signal.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#include <stdarg.h>
#include "openbsd-compat/sys-queue.h"
#include "xmalloc.h"
#include "packet.h"
#include "sshbuf.h"
#include "log.h"
#include "misc.h"
#include "servconf.h"
#include "canohost.h"
#include "sshpty.h"
#include "channels.h"
#include "compat.h"
#include "ssh2.h"
#include "sshkey.h"
#include "cipher.h"
#include "kex.h"
#include "hostfile.h"
#include "auth.h"
#include "session.h"
#include "dispatch.h"
#include "auth-options.h"
#include "serverloop.h"
#include "ssherr.h"
extern ServerOptions options;
/* XXX */
extern Authctxt *the_authctxt;
extern struct sshauthopt *auth_opts;
extern int use_privsep;
static int no_more_sessions = 0; /* Disallow further sessions. */
static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */
/* Cleanup on signals (!use_privsep case only) */
static volatile sig_atomic_t received_sigterm = 0;
/* prototypes */
static void server_init_dispatch(struct ssh *);
/* requested tunnel forwarding interface(s), shared with session.c */
char *tun_fwd_ifnames = NULL;
/* returns 1 if bind to specified port by specified user is permitted */
static int
bind_permitted(int port, uid_t uid)
{
if (use_privsep)
return 1; /* allow system to decide */
if (port < IPPORT_RESERVED && uid != 0)
return 0;
return 1;
}
/*ARGSUSED*/
static void
sigchld_handler(int sig)
{
child_terminated = 1;
}
/*ARGSUSED*/
static void
sigterm_handler(int sig)
{
received_sigterm = sig;
}
static void
client_alive_check(struct ssh *ssh)
{
char remote_id[512];
int r, channel_id;
/* timeout, check to see how many we have had */
if (options.client_alive_count_max > 0 &&
ssh_packet_inc_alive_timeouts(ssh) >
options.client_alive_count_max) {
sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));
logit("Timeout, client not responding from %s", remote_id);
cleanup_exit(255);
}
/*
* send a bogus global/channel request with "wantreply",
* we should get back a failure
*/
if ((channel_id = channel_find_open(ssh)) == -1) {
if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
(r = sshpkt_put_cstring(ssh, "keepalive@openssh.com"))
!= 0 ||
(r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */
fatal_fr(r, "compose");
} else {
channel_request_start(ssh, channel_id,
"keepalive@openssh.com", 1);
}
if ((r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send");
}
/*
* Sleep in ppoll() until we can do something.
* Optionally, a maximum time can be specified for the duration of
* the wait (0 = infinite).
*/
static void
wait_until_can_do_something(struct ssh *ssh,
int connection_in, int connection_out, struct pollfd **pfdp,
u_int *npfd_allocp, u_int *npfd_activep, u_int64_t max_time_ms,
sigset_t *sigsetp, int *conn_in_readyp, int *conn_out_readyp)
{
struct timespec ts, *tsp;
int ret;
time_t minwait_secs = 0;
int client_alive_scheduled = 0;
u_int p;
/* time we last heard from the client OR sent a keepalive */
static time_t last_client_time;
*conn_in_readyp = *conn_out_readyp = 0;
/* Prepare channel poll. First two pollfd entries are reserved */
channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep,
2, &minwait_secs);
if (*npfd_activep < 2)
fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */
/* XXX need proper deadline system for rekey/client alive */
if (minwait_secs != 0)
max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000);
/*
* if using client_alive, set the max timeout accordingly,
* and indicate that this particular timeout was for client
* alive by setting the client_alive_scheduled flag.
*
* this could be randomized somewhat to make traffic
* analysis more difficult, but we're not doing it yet.
*/
if (options.client_alive_interval) {
uint64_t keepalive_ms =
(uint64_t)options.client_alive_interval * 1000;
if (max_time_ms == 0 || max_time_ms > keepalive_ms) {
max_time_ms = keepalive_ms;
client_alive_scheduled = 1;
}
if (last_client_time == 0)
last_client_time = monotime();
}
#if 0
/* wrong: bad condition XXX */
if (channel_not_very_much_buffered_data())
#endif
/* Monitor client connection on reserved pollfd entries */
(*pfdp)[0].fd = connection_in;
(*pfdp)[0].events = POLLIN;
(*pfdp)[1].fd = connection_out;
(*pfdp)[1].events = ssh_packet_have_data_to_write(ssh) ? POLLOUT : 0;
/*
* If child has terminated and there is enough buffer space to read
* from it, then read as much as is available and exit.
*/
if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh))
if (max_time_ms == 0 || client_alive_scheduled)
max_time_ms = 100;
if (max_time_ms == 0)
tsp = NULL;
else {
ts.tv_sec = max_time_ms / 1000;
ts.tv_nsec = 1000000 * (max_time_ms % 1000);
tsp = &ts;
}
/* Wait for something to happen, or the timeout to expire. */
ret = ppoll(*pfdp, *npfd_activep, tsp, sigsetp);
if (ret == -1) {
for (p = 0; p < *npfd_activep; p++)
(*pfdp)[p].revents = 0;
if (errno != EINTR)
fatal_f("ppoll: %.100s", strerror(errno));
return;
}
*conn_in_readyp = (*pfdp)[0].revents != 0;
*conn_out_readyp = (*pfdp)[1].revents != 0;
if (client_alive_scheduled) {
time_t now = monotime();
/*
* If the ppoll timed out, or returned for some other reason
* but we haven't heard from the client in time, send keepalive.
*/
if (ret == 0 || (last_client_time != 0 && last_client_time +
options.client_alive_interval <= now)) {
client_alive_check(ssh);
last_client_time = now;
} else if (*conn_in_readyp)
last_client_time = now;
}
}
/*
* Processes input from the client and the program. Input data is stored
* in buffers and processed later.
*/
static int
process_input(struct ssh *ssh, int connection_in)
{
int r, len;
char buf[16384];
/* Read and buffer any input data from the client. */
len = read(connection_in, buf, sizeof(buf));
if (len == 0) {
verbose("Connection closed by %.100s port %d",
ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
return -1;
} else if (len == -1) {
if (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)
return 0;
verbose("Read error from remote host %s port %d: %s",
ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
strerror(errno));
cleanup_exit(255);
}
/* Buffer any received data. */
if ((r = ssh_packet_process_incoming(ssh, buf, len)) != 0)
fatal_fr(r, "ssh_packet_process_incoming");
return 0;
}
/*
* Sends data from internal buffers to client program stdin.
*/
static void
process_output(struct ssh *ssh, int connection_out)
{
int r;
/* Send any buffered packet data to the client. */
if ((r = ssh_packet_write_poll(ssh)) != 0) {
sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll",
__func__);
}
}
static void
process_buffered_input_packets(struct ssh *ssh)
{
ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL);
}
static void
collect_children(struct ssh *ssh)
{
pid_t pid;
int status;
if (child_terminated) {
debug("Received SIGCHLD.");
while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
(pid == -1 && errno == EINTR))
if (pid > 0)
session_close_by_pid(ssh, pid, status);
child_terminated = 0;
}
}
void
server_loop2(struct ssh *ssh, Authctxt *authctxt)
{
struct pollfd *pfd = NULL;
u_int npfd_alloc = 0, npfd_active = 0;
int r, conn_in_ready, conn_out_ready;
u_int connection_in, connection_out;
u_int64_t rekey_timeout_ms = 0;
sigset_t bsigset, osigset;
debug("Entering interactive session for SSH2.");
if (sigemptyset(&bsigset) == -1 || sigaddset(&bsigset, SIGCHLD) == -1)
error_f("bsigset setup: %s", strerror(errno));
ssh_signal(SIGCHLD, sigchld_handler);
child_terminated = 0;
connection_in = ssh_packet_get_connection_in(ssh);
connection_out = ssh_packet_get_connection_out(ssh);
if (!use_privsep) {
ssh_signal(SIGTERM, sigterm_handler);
ssh_signal(SIGINT, sigterm_handler);
ssh_signal(SIGQUIT, sigterm_handler);
}
server_init_dispatch(ssh);
for (;;) {
process_buffered_input_packets(ssh);
if (!ssh_packet_is_rekeying(ssh) &&
ssh_packet_not_very_much_data_to_write(ssh))
channel_output_poll(ssh);
if (options.rekey_interval > 0 &&
!ssh_packet_is_rekeying(ssh)) {
rekey_timeout_ms = ssh_packet_get_rekey_timeout(ssh) *
1000;
} else {
rekey_timeout_ms = 0;
}
/*
* Block SIGCHLD while we check for dead children, then pass
* the old signal mask through to ppoll() so that it'll wake
* up immediately if a child exits after we've called waitpid().
*/
if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1)
error_f("bsigset sigprocmask: %s", strerror(errno));
collect_children(ssh);
wait_until_can_do_something(ssh, connection_in, connection_out,
&pfd, &npfd_alloc, &npfd_active, rekey_timeout_ms, &osigset,
&conn_in_ready, &conn_out_ready);
if (sigprocmask(SIG_UNBLOCK, &bsigset, &osigset) == -1)
error_f("osigset sigprocmask: %s", strerror(errno));
if (received_sigterm) {
logit("Exiting on signal %d", (int)received_sigterm);
/* Clean up sessions, utmp, etc. */
cleanup_exit(255);
}
if (!ssh_packet_is_rekeying(ssh))
channel_after_poll(ssh, pfd, npfd_active);
if (conn_in_ready &&
process_input(ssh, connection_in) < 0)
break;
/* A timeout may have triggered rekeying */
if ((r = ssh_packet_check_rekey(ssh)) != 0)
fatal_fr(r, "cannot start rekeying");
if (conn_out_ready)
process_output(ssh, connection_out);
}
collect_children(ssh);
free(pfd);
/* free all channels, no more reads and writes */
channel_free_all(ssh);
/* free remaining sessions, e.g. remove wtmp entries */
session_destroy_all(ssh, NULL);
}
static int
server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh)
{
debug("Got %d/%u for keepalive", type, seq);
/*
* reset timeout, since we got a sane answer from the client.
* even if this was generated by something other than
* the bogus CHANNEL_REQUEST we send for keepalives.
*/
ssh_packet_set_alive_timeouts(ssh, 0);
return 0;
}
static Channel *
server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg)
{
Channel *c = NULL;
char *target = NULL, *originator = NULL;
u_int target_port = 0, originator_port = 0;
int r;
if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 ||
(r = sshpkt_get_u32(ssh, &target_port)) != 0 ||
(r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 ||
(r = sshpkt_get_u32(ssh, &originator_port)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
if (target_port > 0xFFFF) {
error_f("invalid target port");
*reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
goto out;
}
if (originator_port > 0xFFFF) {
error_f("invalid originator port");
*reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
goto out;
}
debug_f("originator %s port %u, target %s port %u",
originator, originator_port, target, target_port);
/* XXX fine grained permissions */
if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
auth_opts->permit_port_forwarding_flag &&
!options.disable_forwarding) {
c = channel_connect_to_port(ssh, target, target_port,
"direct-tcpip", "direct-tcpip", reason, errmsg);
} else {
logit("refused local port forward: "
"originator %s port %d, target %s port %d",
originator, originator_port, target, target_port);
if (reason != NULL)
*reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
}
out:
free(originator);
free(target);
return c;
}
static Channel *
server_request_direct_streamlocal(struct ssh *ssh)
{
Channel *c = NULL;
char *target = NULL, *originator = NULL;
u_int originator_port = 0;
struct passwd *pw = the_authctxt->pw;
int r;
if (pw == NULL || !the_authctxt->valid)
fatal_f("no/invalid user");
if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 ||
(r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 ||
(r = sshpkt_get_u32(ssh, &originator_port)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
if (originator_port > 0xFFFF) {
error_f("invalid originator port");
goto out;
}
debug_f("originator %s port %d, target %s",
originator, originator_port, target);
/* XXX fine grained permissions */
if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 &&
auth_opts->permit_port_forwarding_flag &&
!options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) {
c = channel_connect_to_path(ssh, target,
"direct-streamlocal@openssh.com", "direct-streamlocal");
} else {
logit("refused streamlocal port forward: "
"originator %s port %d, target %s",
originator, originator_port, target);
}
out:
free(originator);
free(target);
return c;
}
static Channel *
server_request_tun(struct ssh *ssh)
{
Channel *c = NULL;
u_int mode, tun;
int r, sock;
char *tmp, *ifname = NULL;
if ((r = sshpkt_get_u32(ssh, &mode)) != 0)
sshpkt_fatal(ssh, r, "%s: parse mode", __func__);
switch (mode) {
case SSH_TUNMODE_POINTOPOINT:
case SSH_TUNMODE_ETHERNET:
break;
default:
ssh_packet_send_debug(ssh, "Unsupported tunnel device mode.");
return NULL;
}
if ((options.permit_tun & mode) == 0) {
ssh_packet_send_debug(ssh, "Server has rejected tunnel device "
"forwarding");
return NULL;
}
if ((r = sshpkt_get_u32(ssh, &tun)) != 0)
sshpkt_fatal(ssh, r, "%s: parse device", __func__);
if (tun > INT_MAX) {
debug_f("invalid tun");
goto done;
}
if (auth_opts->force_tun_device != -1) {
if (tun != SSH_TUNID_ANY &&
auth_opts->force_tun_device != (int)tun)
goto done;
tun = auth_opts->force_tun_device;
}
sock = tun_open(tun, mode, &ifname);
if (sock < 0)
goto done;
debug("Tunnel forwarding using interface %s", ifname);
c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1,
CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
c->datagram = 1;
#if defined(SSH_TUN_FILTER)
if (mode == SSH_TUNMODE_POINTOPOINT)
channel_register_filter(ssh, c->self, sys_tun_infilter,
sys_tun_outfilter, NULL, NULL);
#endif
/*
* Update the list of names exposed to the session
* XXX remove these if the tunnels are closed (won't matter
* much if they are already in the environment though)
*/
tmp = tun_fwd_ifnames;
xasprintf(&tun_fwd_ifnames, "%s%s%s",
tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames,
tun_fwd_ifnames == NULL ? "" : ",",
ifname);
free(tmp);
free(ifname);
done:
if (c == NULL)
ssh_packet_send_debug(ssh, "Failed to open the tunnel device.");
return c;
}
static Channel *
server_request_session(struct ssh *ssh)
{
Channel *c;
int r;
debug("input_session_request");
if ((r = sshpkt_get_end(ssh)) != 0)
sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
if (no_more_sessions) {
ssh_packet_disconnect(ssh, "Possible attack: attempt to open a "
"session after additional sessions disabled");
}
/*
* A server session has no fd to read or write until a
* CHANNEL_REQUEST for a shell is made, so we set the type to
* SSH_CHANNEL_LARVAL. Additionally, a callback for handling all
* CHANNEL_REQUEST messages is registered.
*/
c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL,
-1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
0, "server-session", 1);
if (session_open(the_authctxt, c->self) != 1) {
debug("session open failed, free channel %d", c->self);
channel_free(ssh, c);
return NULL;
}
channel_register_cleanup(ssh, c->self, session_close_by_channel, 0);
return c;
}
static int
server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh)
{
Channel *c = NULL;
char *ctype = NULL;
const char *errmsg = NULL;
int r, reason = SSH2_OPEN_CONNECT_FAILED;
u_int rchan = 0, rmaxpack = 0, rwindow = 0;
if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 ||
(r = sshpkt_get_u32(ssh, &rchan)) != 0 ||
(r = sshpkt_get_u32(ssh, &rwindow)) != 0 ||
(r = sshpkt_get_u32(ssh, &rmaxpack)) != 0)
sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
debug_f("ctype %s rchan %u win %u max %u",
ctype, rchan, rwindow, rmaxpack);
if (strcmp(ctype, "session") == 0) {
c = server_request_session(ssh);
} else if (strcmp(ctype, "direct-tcpip") == 0) {
c = server_request_direct_tcpip(ssh, &reason, &errmsg);
} else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) {
c = server_request_direct_streamlocal(ssh);
} else if (strcmp(ctype, "tun@openssh.com") == 0) {
c = server_request_tun(ssh);
}
if (c != NULL) {
debug_f("confirm %s", ctype);
c->remote_id = rchan;
c->have_remote_id = 1;
c->remote_window = rwindow;
c->remote_maxpacket = rmaxpack;
if (c->type != SSH_CHANNEL_CONNECTING) {
if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 ||
(r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
(r = sshpkt_put_u32(ssh, c->self)) != 0 ||
(r = sshpkt_put_u32(ssh, c->local_window)) != 0 ||
(r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 ||
(r = sshpkt_send(ssh)) != 0) {
sshpkt_fatal(ssh, r,
"%s: send open confirm", __func__);
}
}
} else {
debug_f("failure %s", ctype);
if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 ||
(r = sshpkt_put_u32(ssh, rchan)) != 0 ||
(r = sshpkt_put_u32(ssh, reason)) != 0 ||
(r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 ||
(r = sshpkt_put_cstring(ssh, "")) != 0 ||
(r = sshpkt_send(ssh)) != 0) {
sshpkt_fatal(ssh, r,
"%s: send open failure", __func__);
}
}
free(ctype);
return 0;
}
static int
server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp)
{
struct sshbuf *resp = NULL;
struct sshbuf *sigbuf = NULL;
struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL;
int r, ndx, success = 0;
const u_char *blob;
const char *sigalg, *kex_rsa_sigalg = NULL;
u_char *sig = 0;
size_t blen, slen;
if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL)
fatal_f("sshbuf_new");
if (sshkey_type_plain(sshkey_type_from_name(
ssh->kex->hostkey_alg)) == KEY_RSA)
kex_rsa_sigalg = ssh->kex->hostkey_alg;
while (ssh_packet_remaining(ssh) > 0) {
sshkey_free(key);
key = NULL;
if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 ||
(r = sshkey_from_blob(blob, blen, &key)) != 0) {
error_fr(r, "parse key");
goto out;
}
/*
* Better check that this is actually one of our hostkeys
* before attempting to sign anything with it.
*/
if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) {
error_f("unknown host %s key", sshkey_type(key));
goto out;
}
/*
* XXX refactor: make kex->sign just use an index rather
* than passing in public and private keys
*/
if ((key_prv = get_hostkey_by_index(ndx)) == NULL &&
(key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) {
error_f("can't retrieve hostkey %d", ndx);
goto out;
}
sshbuf_reset(sigbuf);
free(sig);
sig = NULL;
/*
* For RSA keys, prefer to use the signature type negotiated
* during KEX to the default (SHA1).
*/
sigalg = NULL;
if (sshkey_type_plain(key->type) == KEY_RSA) {
if (kex_rsa_sigalg != NULL)
sigalg = kex_rsa_sigalg;
else if (ssh->kex->flags & KEX_RSA_SHA2_512_SUPPORTED)
sigalg = "rsa-sha2-512";
else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED)
sigalg = "rsa-sha2-256";
}
debug3_f("sign %s key (index %d) using sigalg %s",
sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg);
if ((r = sshbuf_put_cstring(sigbuf,
"hostkeys-prove-00@openssh.com")) != 0 ||
(r = sshbuf_put_stringb(sigbuf,
ssh->kex->session_id)) != 0 ||
(r = sshkey_puts(key, sigbuf)) != 0 ||
(r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen,
sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), sigalg)) != 0 ||
(r = sshbuf_put_string(resp, sig, slen)) != 0) {
error_fr(r, "assemble signature");
goto out;
}
}
/* Success */
*respp = resp;
resp = NULL; /* don't free it */
success = 1;
out:
free(sig);
sshbuf_free(resp);
sshbuf_free(sigbuf);
sshkey_free(key);
return success;
}
static int
server_input_global_request(int type, u_int32_t seq, struct ssh *ssh)
{
char *rtype = NULL;
u_char want_reply = 0;
int r, success = 0, allocated_listen_port = 0;
u_int port = 0;
struct sshbuf *resp = NULL;
struct passwd *pw = the_authctxt->pw;
struct Forward fwd;
memset(&fwd, 0, sizeof(fwd));
if (pw == NULL || !the_authctxt->valid)
fatal_f("no/invalid user");
if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 ||
(r = sshpkt_get_u8(ssh, &want_reply)) != 0)
sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
debug_f("rtype %s want_reply %d", rtype, want_reply);
/* -R style forwarding */
if (strcmp(rtype, "tcpip-forward") == 0) {
if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 ||
(r = sshpkt_get_u32(ssh, &port)) != 0)
sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__);
debug_f("tcpip-forward listen %s port %u",
fwd.listen_host, port);
if (port <= INT_MAX)
fwd.listen_port = (int)port;
/* check permissions */
if (port > INT_MAX ||
(options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 ||
!auth_opts->permit_port_forwarding_flag ||
options.disable_forwarding ||
(!want_reply && fwd.listen_port == 0) ||
(fwd.listen_port != 0 &&
!bind_permitted(fwd.listen_port, pw->pw_uid))) {
success = 0;
ssh_packet_send_debug(ssh, "Server has disabled port forwarding.");
} else {
/* Start listening on the port */
success = channel_setup_remote_fwd_listener(ssh, &fwd,
&allocated_listen_port, &options.fwd_opts);
}
if ((resp = sshbuf_new()) == NULL)
fatal_f("sshbuf_new");
if (allocated_listen_port != 0 &&
(r = sshbuf_put_u32(resp, allocated_listen_port)) != 0)
fatal_fr(r, "sshbuf_put_u32");
} else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 ||
(r = sshpkt_get_u32(ssh, &port)) != 0)
sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__);
debug_f("cancel-tcpip-forward addr %s port %d",
fwd.listen_host, port);
if (port <= INT_MAX) {
fwd.listen_port = (int)port;
success = channel_cancel_rport_listener(ssh, &fwd);
}
} else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) {
if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0)
sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__);
debug_f("streamlocal-forward listen path %s",
fwd.listen_path);
/* check permissions */
if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0
|| !auth_opts->permit_port_forwarding_flag ||
options.disable_forwarding ||
(pw->pw_uid != 0 && !use_privsep)) {
success = 0;
ssh_packet_send_debug(ssh, "Server has disabled "
"streamlocal forwarding.");
} else {
/* Start listening on the socket */
success = channel_setup_remote_fwd_listener(ssh,
&fwd, NULL, &options.fwd_opts);
}
} else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) {
if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0)
sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__);
debug_f("cancel-streamlocal-forward path %s",
fwd.listen_path);
success = channel_cancel_rport_listener(ssh, &fwd);
} else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
no_more_sessions = 1;
success = 1;
} else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) {
success = server_input_hostkeys_prove(ssh, &resp);
}
/* XXX sshpkt_get_end() */
if (want_reply) {
if ((r = sshpkt_start(ssh, success ?
SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 ||
(success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) ||
(r = sshpkt_send(ssh)) != 0 ||
(r = ssh_packet_write_wait(ssh)) != 0)
sshpkt_fatal(ssh, r, "%s: send reply", __func__);
}
free(fwd.listen_host);
free(fwd.listen_path);
free(rtype);
sshbuf_free(resp);
return 0;
}
static int
server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh)
{
Channel *c;
int r, success = 0;
char *rtype = NULL;
u_char want_reply = 0;
u_int id = 0;
if ((r = sshpkt_get_u32(ssh, &id)) != 0 ||
(r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 ||
(r = sshpkt_get_u8(ssh, &want_reply)) != 0)
sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
debug("server_input_channel_req: channel %u request %s reply %d",
id, rtype, want_reply);
if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) {
ssh_packet_disconnect(ssh, "%s: unknown channel %d",
__func__, id);
}
if (!strcmp(rtype, "eow@openssh.com")) {
if ((r = sshpkt_get_end(ssh)) != 0)
sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
chan_rcvd_eow(ssh, c);
} else if ((c->type == SSH_CHANNEL_LARVAL ||
c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
success = session_input_channel_req(ssh, c, rtype);
if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) {
if (!c->have_remote_id)
fatal_f("channel %d: no remote_id", c->self);
if ((r = sshpkt_start(ssh, success ?
SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 ||
(r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
sshpkt_fatal(ssh, r, "%s: send reply", __func__);
}
free(rtype);
return 0;
}
static void
server_init_dispatch(struct ssh *ssh)
{
debug("server_init_dispatch");
ssh_dispatch_init(ssh, &dispatch_protocol_error);
ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data);
ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
/* client_alive */
ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
/* rekeying */
ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
}
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