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upstream: Add a sshd_config UnusedConnectionTimeout option to terminate
client connections that have no open channels for some length of time. This complements the recently-added ChannelTimeout option that terminates inactive channels after a timeout. ok markus@ OpenBSD-Commit-ID: ca983be74c0350364c11f8ba3bd692f6f24f5da9
This commit is contained in:
djm@openbsd.org
Damien Miller
parent
8ec2e31238
commit
0293c19807
25
servconf.c
25
servconf.c
@ -1,5 +1,5 @@
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/* $OpenBSD: servconf.c,v 1.389 2023/01/06 02:47:18 djm Exp $ */
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/* $OpenBSD: servconf.c,v 1.390 2023/01/17 09:44:48 djm Exp $ */
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/*
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* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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* All rights reserved
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@ -198,6 +198,7 @@ initialize_server_options(ServerOptions *options)
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options->required_rsa_size = -1;
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options->channel_timeouts = NULL;
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options->num_channel_timeouts = 0;
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options->unused_connection_timeout = -1;
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}
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/* Returns 1 if a string option is unset or set to "none" or 0 otherwise. */
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@ -446,6 +447,8 @@ fill_default_server_options(ServerOptions *options)
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options->sk_provider = xstrdup("internal");
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if (options->required_rsa_size == -1)
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options->required_rsa_size = SSH_RSA_MINIMUM_MODULUS_SIZE;
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if (options->unused_connection_timeout == -1)
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options->unused_connection_timeout = 0;
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assemble_algorithms(options);
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@ -529,7 +532,7 @@ typedef enum {
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sStreamLocalBindMask, sStreamLocalBindUnlink,
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sAllowStreamLocalForwarding, sFingerprintHash, sDisableForwarding,
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sExposeAuthInfo, sRDomain, sPubkeyAuthOptions, sSecurityKeyProvider,
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sRequiredRSASize, sChannelTimeout,
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sRequiredRSASize, sChannelTimeout, sUnusedConnectionTimeout,
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sDeprecated, sIgnore, sUnsupported
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} ServerOpCodes;
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@ -691,6 +694,7 @@ static struct {
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{ "securitykeyprovider", sSecurityKeyProvider, SSHCFG_GLOBAL },
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{ "requiredrsasize", sRequiredRSASize, SSHCFG_ALL },
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{ "channeltimeout", sChannelTimeout, SSHCFG_ALL },
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{ "unusedconnectiontimeout", sUnusedConnectionTimeout, SSHCFG_ALL },
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{ NULL, sBadOption, 0 }
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};
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@ -2537,6 +2541,17 @@ process_server_config_line_depth(ServerOptions *options, char *line,
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}
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break;
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case sUnusedConnectionTimeout:
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intptr = &options->unused_connection_timeout;
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/* peek at first arg for "none" so we can reuse parse_time */
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if (av[0] != NULL && strcasecmp(av[0], "none") == 0) {
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(void)argv_next(&ac, &av); /* consume arg */
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if (*activep)
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*intptr = 0;
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break;
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}
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goto parse_time;
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case sDeprecated:
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case sIgnore:
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case sUnsupported:
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@ -2709,6 +2724,7 @@ copy_set_server_options(ServerOptions *dst, ServerOptions *src, int preauth)
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M_CP_INTOPT(rekey_interval);
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M_CP_INTOPT(log_level);
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M_CP_INTOPT(required_rsa_size);
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M_CP_INTOPT(unused_connection_timeout);
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/*
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* The bind_mask is a mode_t that may be unsigned, so we can't use
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@ -2861,6 +2877,10 @@ fmt_intarg(ServerOpCodes code, int val)
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static void
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dump_cfg_int(ServerOpCodes code, int val)
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{
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if (code == sUnusedConnectionTimeout && val == 0) {
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printf("%s none\n", lookup_opcode_name(code));
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return;
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}
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printf("%s %d\n", lookup_opcode_name(code), val);
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}
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@ -2977,6 +2997,7 @@ dump_config(ServerOptions *o)
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dump_cfg_int(sClientAliveCountMax, o->client_alive_count_max);
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dump_cfg_int(sRequiredRSASize, o->required_rsa_size);
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dump_cfg_oct(sStreamLocalBindMask, o->fwd_opts.streamlocal_bind_mask);
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dump_cfg_int(sUnusedConnectionTimeout, o->unused_connection_timeout);
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/* formatted integer arguments */
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dump_cfg_fmtint(sPermitRootLogin, o->permit_root_login);
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@ -1,4 +1,4 @@
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/* $OpenBSD: servconf.h,v 1.158 2023/01/06 02:47:19 djm Exp $ */
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/* $OpenBSD: servconf.h,v 1.159 2023/01/17 09:44:48 djm Exp $ */
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/*
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* Author: Tatu Ylonen <ylo@cs.hut.fi>
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@ -233,6 +233,8 @@ typedef struct {
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char **channel_timeouts; /* inactivity timeout by channel type */
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u_int num_channel_timeouts;
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int unused_connection_timeout;
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} ServerOptions;
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/* Information about the incoming connection as used by Match */
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33
serverloop.c
33
serverloop.c
@ -1,4 +1,4 @@
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/* $OpenBSD: serverloop.c,v 1.233 2023/01/06 02:38:23 djm Exp $ */
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/* $OpenBSD: serverloop.c,v 1.234 2023/01/17 09:44:48 djm Exp $ */
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/*
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* Author: Tatu Ylonen <ylo@cs.hut.fi>
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* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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@ -172,17 +172,19 @@ wait_until_can_do_something(struct ssh *ssh,
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int *conn_in_readyp, int *conn_out_readyp)
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{
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struct timespec timeout;
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char remote_id[512];
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int ret;
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int client_alive_scheduled = 0;
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u_int p;
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/* time we last heard from the client OR sent a keepalive */
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static time_t last_client_time;
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time_t now;
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static time_t last_client_time, unused_connection_expiry;
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*conn_in_readyp = *conn_out_readyp = 0;
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/* Prepare channel poll. First two pollfd entries are reserved */
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ptimeout_init(&timeout);
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channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep, 2, &timeout);
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now = monotime();
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if (*npfd_activep < 2)
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fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */
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if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh)) {
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@ -190,6 +192,18 @@ wait_until_can_do_something(struct ssh *ssh,
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ssh_packet_get_rekey_timeout(ssh));
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}
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/*
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* If no channels are open and UnusedConnectionTimeout is set, then
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* start the clock to terminate the connection.
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*/
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if (options.unused_connection_timeout != 0) {
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if (channel_still_open(ssh) || unused_connection_expiry == 0) {
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unused_connection_expiry = now +
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options.unused_connection_timeout;
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}
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ptimeout_deadline_monotime(&timeout, unused_connection_expiry);
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}
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/*
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* if using client_alive, set the max timeout accordingly,
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* and indicate that this particular timeout was for client
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@ -199,8 +213,9 @@ wait_until_can_do_something(struct ssh *ssh,
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* analysis more difficult, but we're not doing it yet.
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*/
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if (options.client_alive_interval) {
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/* Time we last heard from the client OR sent a keepalive */
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if (last_client_time == 0)
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last_client_time = monotime();
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last_client_time = now;
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ptimeout_deadline_sec(&timeout, options.client_alive_interval);
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/* XXX ? deadline_monotime(last_client_time + alive_interval) */
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client_alive_scheduled = 1;
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@ -237,9 +252,9 @@ wait_until_can_do_something(struct ssh *ssh,
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*conn_in_readyp = (*pfdp)[0].revents != 0;
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*conn_out_readyp = (*pfdp)[1].revents != 0;
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now = monotime(); /* need to reset after ppoll() */
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/* ClientAliveInterval probing */
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if (client_alive_scheduled) {
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time_t now = monotime();
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if (ret == 0 &&
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now > last_client_time + options.client_alive_interval) {
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/* ppoll timed out and we're due to probe */
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@ -250,6 +265,14 @@ wait_until_can_do_something(struct ssh *ssh,
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last_client_time = now;
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}
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}
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/* UnusedConnectionTimeout handling */
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if (unused_connection_expiry != 0 &&
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now > unused_connection_expiry && !channel_still_open(ssh)) {
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sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));
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logit("terminating inactive connection from %s", remote_id);
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cleanup_exit(255);
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}
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}
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/*
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@ -33,8 +33,8 @@
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $OpenBSD: sshd_config.5,v 1.345 2023/01/06 08:44:11 jmc Exp $
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.Dd $Mdocdate: January 6 2023 $
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.\" $OpenBSD: sshd_config.5,v 1.346 2023/01/17 09:44:48 djm Exp $
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.Dd $Mdocdate: January 17 2023 $
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.Dt SSHD_CONFIG 5
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.Os
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.Sh NAME
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@ -459,6 +459,9 @@ close the SSH connection, nor does it prevent a client from
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requesting another channel of the same type.
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In particular, expiring an inactive forwarding session does not prevent
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another identical forwarding from being subsequently created.
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See also
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.Cm UnusedConnectionTimeout ,
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which may be used in conjunction with this option.
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.Pp
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The default is not to expire channels of any type for inactivity.
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.It Cm ChrootDirectory
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@ -1256,6 +1259,7 @@ Available keywords are
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.Cm AuthorizedPrincipalsFile ,
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.Cm Banner ,
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.Cm CASignatureAlgorithms ,
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.Cm ChannelTimeout ,
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.Cm ChrootDirectory ,
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.Cm ClientAliveCountMax ,
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.Cm ClientAliveInterval ,
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@ -1295,6 +1299,7 @@ Available keywords are
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.Cm StreamLocalBindMask ,
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.Cm StreamLocalBindUnlink ,
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.Cm TrustedUserCAKeys ,
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.Cm UnusedConnectionTimeout ,
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.Cm X11DisplayOffset ,
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.Cm X11Forwarding
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and
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@ -1811,6 +1816,33 @@ for authentication using
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.Cm TrustedUserCAKeys .
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For more details on certificates, see the CERTIFICATES section in
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.Xr ssh-keygen 1 .
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.It Cm UnusedConnectionTimeout
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Specifies whether and how quickly
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.Xr sshd 8
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should close client connections with no open channels.
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Open channels include active shell, command execution or subsystem
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sessions, connected network, socket, agent of X11 forwardings.
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Forwarding listeners, such as those from the
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.Xr ssh 1
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.Fl R
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flag are not considered as open channels and do not prevent the timeout.
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The timeout value
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is specified in seconds or may use any of the units documented in the
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.Sx TIME FORMATS
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section.
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.Pp
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Note that this timeout starts when the client connection completes
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user authentication but before the client has an opportunity to open any
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channels.
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Caution should be used when using short timeout values, as they may not
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provide sufficient time for the client to request and open its channels
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before terminating the connection.
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.Pp
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The default
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.Cm none
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is to never expire connections for having no open channels.
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This option may be useful in conjunction with
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.Cm ChannelTimeout .
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.It Cm UseDNS
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Specifies whether
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.Xr sshd 8
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