I have added a '-n' flag to the watch(8) command. This option

disables the ability to interactively select a new tty.  I have also
removed a check for uid == 0 because it gets in the way of using suid
mode based access control.  Watch (8)is only runnable by root, so this
does not really change things much.

Closes PR#2131

Submitted-By: adrian@virginia.edu

2 files changed, 20 insertions, 9 deletions

diff --git a/usr.sbin/watch/watch.8 b/usr.sbin/watch/watch.8
index 50bd5b8..f2f9ed8 100644
--- a/usr.sbin/watch/watch.8
+++ b/usr.sbin/watch/watch.8
@@ -11,7 +11,7 @@
 .Nm watch
 .Op Fl ciotW
 .Ar tty
-.\"  watch [-ciotW] [<tty name>]
+.\"  watch [-ciotnW] [<tty name>]
 .Sh DESCRIPTION
 .Nm Watch
 allows the superuser to examine all data coming through a specified tty.
@@ -45,6 +45,12 @@ For more info see
 .Xr snp 4 .
 .It Fl t
 Print the date and time when observation of a given tty is started.
+.It Fl n
+Disable the ability to switch the watched tty interactively.  This disables
+both change requests made with <control-X> as well as automatic prompting
+when the current tty is closed or overflows.  In all cases where a prompt
+would be displayed, watch will exit.  The reconnect flags are unaffected by
+this option.
 .It Fl W
 Allow write access to observed tty.
 .It Ar tty
diff --git a/usr.sbin/watch/watch.c b/usr.sbin/watch/watch.c
index a145916..8add801 100644
--- a/usr.sbin/watch/watch.c
+++ b/usr.sbin/watch/watch.c
@@ -48,6 +48,7 @@ int             opt_reconn_oflow = 0;
 int             opt_interactive = 1;
 int             opt_timestamp = 0;
 int		opt_write = 0;
+int		opt_no_switch = 0;
 
 char            dev_name[DEV_NAME_LEN];
 int             snp_io;
@@ -158,7 +159,7 @@ cleanup()
 void
 show_usage()
 {
-	printf("watch -[ciotW] [tty name]\n");
+	printf("watch -[ciotnW] [tty name]\n");
 	exit(1);
 }
 
@@ -274,16 +275,13 @@ main(ac, av)
 
 	(void) setlocale(LC_TIME, "");
 
-	if (getuid() != 0)
-		fatal(NULL);
-
 	if (isatty(std_out))
 		opt_interactive = 1;
 	else
 		opt_interactive = 0;
 
 
-	while ((ch = getopt(ac, av, "Wciot")) != EOF)
+	while ((ch = getopt(ac, av, "Wciotn")) != EOF)
 		switch (ch) {
 		case 'W':
 			opt_write = 1;
@@ -300,6 +298,9 @@ main(ac, av)
 		case 't':
 			opt_timestamp = 1;
 			break;
+		case 'n':
+			opt_no_switch = 1;
+			break;
 		case '?':
 		default:
 			show_usage();
@@ -312,7 +313,7 @@ main(ac, av)
 	snp_io = open_snp();
 
 	if (*(av += optind) == NULL) {
-		if (opt_interactive)
+		if (opt_interactive && !opt_no_switch)
 			ask_dev(dev_name, MSG_INIT);
 		else
 			fatal("No device name given.");
@@ -345,6 +346,8 @@ main(ac, av)
 				clear();
 				break;
 			case CHR_SWITCH:
+				if (opt_no_switch)
+					break;
 				detach_snp();
 				ask_dev(dev_name, MSG_CHANGE);
 				set_dev(dev_name);
@@ -353,6 +356,8 @@ main(ac, av)
 				if (opt_write) {
 					if (write(snp_io,chb,nread) != nread) {
 						detach_snp();
+						if (opt_no_switch)
+							fatal("Write failed.");
 						ask_dev(dev_name, MSG_NOWRITE);
 						set_dev(dev_name);
 					}
@@ -370,7 +375,7 @@ main(ac, av)
 		case SNP_OFLOW:
 			if (opt_reconn_oflow)
 				attach_snp();
-			else if (opt_interactive) {
+			else if (opt_interactive && !opt_no_switch) {
 				ask_dev(dev_name, MSG_OFLOW);
 				set_dev(dev_name);
 			} else
@@ -379,7 +384,7 @@ main(ac, av)
 		case SNP_TTYCLOSE:
 			if (opt_reconn_close)
 				attach_snp();
-			else if (opt_interactive) {
+			else if (opt_interactive && !opt_no_switch) {
 				ask_dev(dev_name, MSG_CLOSED);
 				set_dev(dev_name);
 			} else