Add channel_force_close()

This will forcibly close an open channel by simulating read/write errors,
draining the IO buffers and calling the detach function.

Previously the detach function was only ever called during channel garbage
collection, but there was no way to signal the user of a channel (e.g.
session.c) that its channel was being closed deliberately (vs. by the
usual state-machine logic). So this adds an extra "force" argument to the
channel cleanup callback to indicate this condition.

ok markus dtucker

diff --git a/usr.bin/ssh/channels.c b/usr.bin/ssh/channels.c
index a1a7f51..1ba8790 100644 (file)
--- a/usr.bin/ssh/channels.c
+++ b/usr.bin/ssh/channels.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.c,v 1.422 2023/01/06 02:38:23 djm Exp $ */
+/* $OpenBSD: channels.c,v 1.423 2023/01/06 02:39:59 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1210,6 +1210,29 @@ x11_open_helper(struct ssh *ssh, struct sshbuf *b)
        return 1;
 }
 
+void
+channel_force_close(struct ssh *ssh, Channel *c, int abandon)
+{
+       debug3_f("channel %d: forcibly closing", c->self);
+       if (c->istate == CHAN_INPUT_OPEN)
+               chan_read_failed(ssh, c);
+       if (c->istate == CHAN_INPUT_WAIT_DRAIN) {
+               sshbuf_reset(c->input);
+               chan_ibuf_empty(ssh, c);
+       }
+       if (c->ostate == CHAN_OUTPUT_OPEN ||
+           c->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
+               sshbuf_reset(c->output);
+               chan_write_failed(ssh, c);
+       }
+       if (c->detach_user)
+               c->detach_user(ssh, c->self, 1, NULL);
+       if (c->efd != -1)
+               channel_close_fd(ssh, c, &c->efd);
+       if (abandon)
+               c->type = SSH_CHANNEL_ABANDONED;
+}
+
 static void
 channel_pre_x11_open(struct ssh *ssh, Channel *c)
 {
@@ -1221,15 +1244,11 @@ channel_pre_x11_open(struct ssh *ssh, Channel *c)
                c->type = SSH_CHANNEL_OPEN;
                channel_pre_open(ssh, c);
        } else if (ret == -1) {
-               logit("X11 connection rejected because of wrong authentication.");
+               logit("X11 connection rejected because of wrong "
+                   "authentication.");
                debug2("X11 rejected %d i%d/o%d",
                    c->self, c->istate, c->ostate);
-               chan_read_failed(ssh, c);
-               sshbuf_reset(c->input);
-               chan_ibuf_empty(ssh, c);
-               sshbuf_reset(c->output);
-               chan_write_failed(ssh, c);
-               debug2("X11 closed %d i%d/o%d", c->self, c->istate, c->ostate);
+               channel_force_close(ssh, c, 0);
        }
 }
 
@@ -1579,11 +1598,7 @@ static void
 rdynamic_close(struct ssh *ssh, Channel *c)
 {
        c->type = SSH_CHANNEL_OPEN;
-       chan_read_failed(ssh, c);
-       sshbuf_reset(c->input);
-       chan_ibuf_empty(ssh, c);
-       sshbuf_reset(c->output);
-       chan_write_failed(ssh, c);
+       channel_force_close(ssh, c, 0);
 }
 
 /* reverse dynamic port forwarding */
@@ -2353,7 +2368,7 @@ channel_garbage_collect(struct ssh *ssh, Channel *c)
                        return;
 
                debug2("channel %d: gc: notify user", c->self);
-               c->detach_user(ssh, c->self, NULL);
+               c->detach_user(ssh, c->self, 0, NULL);
                /* if we still have a callback */
                if (c->detach_user != NULL)
                        return;

diff --git a/usr.bin/ssh/channels.h b/usr.bin/ssh/channels.h
index c04f5a7..c9de0ae 100644 (file)
--- a/usr.bin/ssh/channels.h
+++ b/usr.bin/ssh/channels.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.h,v 1.144 2023/01/06 02:38:23 djm Exp $ */
+/* $OpenBSD: channels.h,v 1.145 2023/01/06 02:39:59 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -88,7 +88,7 @@ typedef struct Channel Channel;
 struct fwd_perm_list;
 
 typedef void channel_open_fn(struct ssh *, int, int, void *);
-typedef void channel_callback_fn(struct ssh *, int, void *);
+typedef void channel_callback_fn(struct ssh *, int, int, void *);
 typedef int channel_infilter_fn(struct ssh *, struct Channel *, char *, int);
 typedef void channel_filter_cleanup_fn(struct ssh *, int, void *);
 typedef u_char *channel_outfilter_fn(struct ssh *, struct Channel *,
@@ -278,6 +278,7 @@ void         channel_set_fds(struct ssh *, int, int, int, int, int,
 void    channel_free(struct ssh *, Channel *);
 void    channel_free_all(struct ssh *);
 void    channel_stop_listening(struct ssh *);
+void    channel_force_close(struct ssh *, Channel *, int);
 
 void    channel_send_open(struct ssh *, int);
 void    channel_request_start(struct ssh *, int, char *, int);

diff --git a/usr.bin/ssh/clientloop.c b/usr.bin/ssh/clientloop.c
index 19a5d4b..a51d431 100644 (file)
--- a/usr.bin/ssh/clientloop.c
+++ b/usr.bin/ssh/clientloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.c,v 1.386 2023/01/06 02:38:23 djm Exp $ */
+/* $OpenBSD: clientloop.c,v 1.387 2023/01/06 02:39:59 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1024,15 +1024,7 @@ process_escapes(struct ssh *ssh, Channel *c,
                                    efc->escape_char)) != 0)
                                        fatal_fr(r, "sshbuf_putf");
                                if (c && c->ctl_chan != -1) {
-                                       chan_read_failed(ssh, c);
-                                       chan_write_failed(ssh, c);
-                                       if (c->detach_user) {
-                                               c->detach_user(ssh,
-                                                   c->self, NULL);
-                                       }
-                                       c->type = SSH_CHANNEL_ABANDONED;
-                                       sshbuf_reset(c->input);
-                                       chan_ibuf_empty(ssh, c);
+                                       channel_force_close(ssh, c, 1);
                                        return 0;
                                } else
                                        quit_pending = 1;
@@ -1258,7 +1250,7 @@ client_simple_escape_filter(struct ssh *ssh, Channel *c, char *buf, int len)
 }
 
 static void
-client_channel_closed(struct ssh *ssh, int id, void *arg)
+client_channel_closed(struct ssh *ssh, int id, int force, void *arg)
 {
        channel_cancel_cleanup(ssh, id);
        session_closed = 1;

diff --git a/usr.bin/ssh/mux.c b/usr.bin/ssh/mux.c
index 6c36377..b59279a 100644 (file)
--- a/usr.bin/ssh/mux.c
+++ b/usr.bin/ssh/mux.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: mux.c,v 1.94 2022/06/03 04:30:47 djm Exp $ */
+/* $OpenBSD: mux.c,v 1.95 2023/01/06 02:39:59 djm Exp $ */
 /*
  * Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org>
  *
@@ -175,7 +175,7 @@ static const struct {
 /* Cleanup callback fired on closure of mux client _session_ channel */
 /* ARGSUSED */
 static void
-mux_master_session_cleanup_cb(struct ssh *ssh, int cid, void *unused)
+mux_master_session_cleanup_cb(struct ssh *ssh, int cid, int force, void *unused)
 {
        Channel *cc, *c = channel_by_id(ssh, cid);
 
@@ -197,7 +197,7 @@ mux_master_session_cleanup_cb(struct ssh *ssh, int cid, void *unused)
 /* Cleanup callback fired on closure of mux client _control_ channel */
 /* ARGSUSED */
 static void
-mux_master_control_cleanup_cb(struct ssh *ssh, int cid, void *unused)
+mux_master_control_cleanup_cb(struct ssh *ssh, int cid, int force, void *unused)
 {
        Channel *sc, *c = channel_by_id(ssh, cid);
 

diff --git a/usr.bin/ssh/session.c b/usr.bin/ssh/session.c
index 91416ea..f2bc407 100644 (file)
--- a/usr.bin/ssh/session.c
+++ b/usr.bin/ssh/session.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: session.c,v 1.330 2022/02/08 08:59:12 dtucker Exp $ */
+/* $OpenBSD: session.c,v 1.331 2023/01/06 02:39:59 djm Exp $ */
 /*
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  *                    All rights reserved
@@ -2015,7 +2015,7 @@ session_close_x11(struct ssh *ssh, int id)
 }
 
 static void
-session_close_single_x11(struct ssh *ssh, int id, void *arg)
+session_close_single_x11(struct ssh *ssh, int id, int force, void *arg)
 {
        Session *s;
        u_int i;
@@ -2146,7 +2146,7 @@ session_close_by_pid(struct ssh *ssh, pid_t pid, int status)
  * the session 'child' itself dies
  */
 void
-session_close_by_channel(struct ssh *ssh, int id, void *arg)
+session_close_by_channel(struct ssh *ssh, int id, int force, void *arg)
 {
        Session *s = session_by_channel(id);
        u_int i;
@@ -2159,12 +2159,14 @@ session_close_by_channel(struct ssh *ssh, int id, void *arg)
        if (s->pid != 0) {
                debug_f("channel %d: has child, ttyfd %d", id, s->ttyfd);
                /*
-                * delay detach of session, but release pty, since
-                * the fd's to the child are already closed
+                * delay detach of session (unless this is a forced close),
+                * but release pty, since the fd's to the child are already
+                * closed
                 */
                if (s->ttyfd != -1)
                        session_pty_cleanup(s);
-               return;
+               if (!force)
+                       return;
        }
        /* detach by removing callback */
        channel_cancel_cleanup(ssh, s->chanid);

diff --git a/usr.bin/ssh/session.h b/usr.bin/ssh/session.h
index ce59dab..344a1dd 100644 (file)
--- a/usr.bin/ssh/session.h
+++ b/usr.bin/ssh/session.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: session.h,v 1.36 2018/10/02 12:40:07 djm Exp $ */
+/* $OpenBSD: session.h,v 1.37 2023/01/06 02:39:59 djm Exp $ */
 
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
@@ -70,7 +70,7 @@ int    session_open(Authctxt *, int);
 void    session_unused(int);
 int     session_input_channel_req(struct ssh *, Channel *, const char *);
 void    session_close_by_pid(struct ssh *ssh, pid_t, int);
-void    session_close_by_channel(struct ssh *, int, void *);
+void    session_close_by_channel(struct ssh *, int, int, void *);
 void    session_destroy_all(struct ssh *, void (*)(Session *));
 void    session_pty_cleanup2(Session *);
 

diff --git a/usr.bin/ssh/ssh.c b/usr.bin/ssh/ssh.c
index b8a21cd..9530902 100644 (file)
--- a/usr.bin/ssh/ssh.c
+++ b/usr.bin/ssh/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.581 2022/12/09 00:22:29 dtucker Exp $ */
+/* $OpenBSD: ssh.c,v 1.582 2023/01/06 02:39:59 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1834,7 +1834,7 @@ ssh_confirm_remote_forward(struct ssh *ssh, int type, u_int32_t seq, void *ctxt)
 }
 
 static void
-client_cleanup_stdio_fwd(struct ssh *ssh, int id, void *arg)
+client_cleanup_stdio_fwd(struct ssh *ssh, int id, int force, void *arg)
 {
        debug("stdio forwarding: done");
        cleanup_exit(0);