- djm@cvs.openbsd.org 2010/07/19 09:15:12

     [clientloop.c readconf.c readconf.h ssh.c ssh_config.5]
     add a "ControlPersist" option that automatically starts a background
     ssh(1) multiplex master when connecting. This connection can stay alive
     indefinitely, or can be set to automatically close after a user-specified
     duration of inactivity. bz#1330 - patch by dwmw2 AT infradead.org, but
     further hacked on by wmertens AT cisco.com, apb AT cequrux.com,
     martin-mindrot-bugzilla AT earth.li and myself; "looks ok" markus@

1 files changed, 95 insertions, 22 deletions

diff --git a/ssh.c b/ssh.c
index 61fe10df0..249be2db8 100644
--- a/ssh.c
+++ b/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.343 2010/07/12 22:41:13 djm Exp $ */
+/* $OpenBSD: ssh.c,v 1.344 2010/07/19 09:15:12 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -128,6 +128,15 @@ int no_shell_flag = 0;
 int stdin_null_flag = 0;
 
 /*
+ * Flag indicating that the current process should be backgrounded and
+ * a new slave launched in the foreground for ControlPersist.
+ */
+int need_controlpersist_detach = 0;
+
+/* Copies of flags for ControlPersist foreground slave */
+int ostdin_null_flag, ono_shell_flag, ono_tty_flag, otty_flag;
+
+/*
  * Flag indicating that ssh should fork after authentication.  This is useful
  * so that the passphrase can be entered manually, and then ssh goes to the
  * background.
@@ -877,6 +886,50 @@ main(int ac, char **av)
         return exit_status;
 }
 
+static void
+control_persist_detach(void)
+{
+        pid_t pid;
+
+        debug("%s: backgrounding master process", __func__);
+
+        /*
+         * master (current process) into the background, and make the
+         * foreground process a client of the backgrounded master.
+         */
+        switch ((pid = fork())) {
+        case -1:
+                fatal("%s: fork: %s", __func__, strerror(errno));
+        case 0:
+                /* Child: master process continues mainloop */
+                break;
+        default:
+                /* Parent: set up mux slave to connect to backgrounded master */
+                debug2("%s: background process is %ld", __func__, (long)pid);
+                stdin_null_flag = ostdin_null_flag;
+                no_shell_flag = ono_shell_flag;
+                no_tty_flag = ono_tty_flag;
+                tty_flag = otty_flag;
+                close(muxserver_sock);
+                muxserver_sock = -1;
+                muxclient(options.control_path);
+                /* muxclient() doesn't return on success. */
+                fatal("Failed to connect to new control master");
+        }
+}
+
+/* Do fork() after authentication. Used by "ssh -f" */
+static void
+fork_postauth(void)
+{
+        if (need_controlpersist_detach)
+                control_persist_detach();
+        debug("forking to background");
+        fork_after_authentication_flag = 0;
+        if (daemon(1, 1) < 0)
+                fatal("daemon() failed: %.200s", strerror(errno));
+}
+
 /* Callback for remote forward global requests */
 static void
 ssh_confirm_remote_forward(int type, u_int32_t seq, void *ctxt)
@@ -904,12 +957,8 @@ ssh_confirm_remote_forward(int type, u_int32_t seq, void *ctxt)
         }
         if (++remote_forward_confirms_received == options.num_remote_forwards) {
                 debug("All remote forwarding requests processed");
-                if (fork_after_authentication_flag) {
-                        fork_after_authentication_flag = 0;
-                        if (daemon(1, 1) < 0)
-                                fatal("daemon() failed: %.200s",
-                                    strerror(errno));
-                }
+                if (fork_after_authentication_flag)
+                        fork_postauth();
         }
 }
 
@@ -1153,12 +1202,13 @@ ssh_session(void)
          * If requested and we are not interested in replies to remote
          * forwarding requests, then let ssh continue in the background.
          */
-        if (fork_after_authentication_flag &&
-            (!options.exit_on_forward_failure ||
-            options.num_remote_forwards == 0)) {
-                fork_after_authentication_flag = 0;
-                if (daemon(1, 1) < 0)
-                        fatal("daemon() failed: %.200s", strerror(errno));
+        if (fork_after_authentication_flag) {
+                if (options.exit_on_forward_failure &&
+                    options.num_remote_forwards > 0) {
+                        debug("deferring postauth fork until remote forward "
+                            "confirmation received");
+                } else
+                        fork_postauth();
         }
 
         /*
@@ -1281,6 +1331,31 @@ ssh_session2(void)
         /* XXX should be pre-session */
         ssh_init_forwarding();
 
+        /* Start listening for multiplex clients */
+        muxserver_listen();
+
+        /*
+         * If we are in control persist mode, then prepare to background
+         * ourselves and have a foreground client attach as a control
+         * slave. NB. we must save copies of the flags that we override for
+         * the backgrounding, since we defer attachment of the slave until
+         * after the connection is fully established (in particular,
+         * async rfwd replies have been received for ExitOnForwardFailure).
+         */
+        if (options.control_persist && muxserver_sock != -1) {
+                ostdin_null_flag = stdin_null_flag;
+                ono_shell_flag = no_shell_flag;
+                ono_tty_flag = no_tty_flag;
+                otty_flag = tty_flag;
+                stdin_null_flag = 1;
+                no_shell_flag = 1;
+                no_tty_flag = 1;
+                tty_flag = 0;
+                if (!fork_after_authentication_flag)
+                        need_controlpersist_detach = 1;
+                fork_after_authentication_flag = 1;
+        }
+
         if (!no_shell_flag || (datafellows & SSH_BUG_DUMMYCHAN))
                 id = ssh_session2_open();
 
@@ -1299,19 +1374,17 @@ ssh_session2(void)
             options.permit_local_command)
                 ssh_local_cmd(options.local_command);
 
-        /* Start listening for multiplex clients */
-        muxserver_listen();
-
         /*
          * If requested and we are not interested in replies to remote
          * forwarding requests, then let ssh continue in the background.
          */
-        if (fork_after_authentication_flag &&
-            (!options.exit_on_forward_failure ||
-            options.num_remote_forwards == 0)) {
-                fork_after_authentication_flag = 0;
-                if (daemon(1, 1) < 0)
-                        fatal("daemon() failed: %.200s", strerror(errno));
+        if (fork_after_authentication_flag) {
+                if (options.exit_on_forward_failure &&
+                    options.num_remote_forwards > 0) {
+                        debug("deferring postauth fork until remote forward "
+                            "confirmation received");
+                } else
+                        fork_postauth();
         }
 
         if (options.use_roaming)