Replace the session-keyring option with a configure option

Join the new session keyring when the server starts rather than once the
configuration file has been loaded, and control it at build time with
--enable-keyring, on by default if linux/keyctl.h is found.

Rename keyring_join and keyring_revoke to new_session_keyring and
revoke_session_keyring.

cfg.c

@@ -62,10 +62,6 @@ cfg_done(__unused struct cmdq_item *item, __unused void *data)
 	}
 
 	prompt_load_history();
-#ifdef HAVE_KEYCTL
-	if (options_get_number(global_options, "session-keyring"))
-		keyring_join();
-#endif
 
 	return (CMD_RETURN_NORMAL);
 }

compat.h

@@ -443,8 +443,8 @@ void		*recallocarray(void *, size_t, size_t, size_t);
 
 #ifdef HAVE_KEYCTL
 /* keyring-linux.c */
-void		 keyring_join(void);
-void		 keyring_revoke(void);
+void		 new_session_keyring(void);
+void		 revoke_session_keyring(void);
 #endif
 
 #ifdef HAVE_SYSTEMD

compat/keyring-linux.c

@@ -17,7 +17,7 @@ static long	keyring_serial;
  * the login session's keyring when it ends).
  */
 void
-keyring_join(void)
+new_session_keyring(void)
 {
 	long	serial;
 
@@ -33,7 +33,7 @@ keyring_join(void)
 }
 
 void
-keyring_revoke(void)
+revoke_session_keyring(void)
 {
 	if (keyring_serial == 0)
 		return;

configure.ac

@@ -795,10 +795,18 @@ else
 	AC_LIBOBJ(daemon)
 fi
 
-# Look for linux/keyctl.h, compat/keyring-linux.c used if found.
-AC_CHECK_HEADER(linux/keyctl.h, found_keyctl=yes, found_keyctl=no)
-if test "x$found_keyctl" = xyes; then
+# Look for linux/keyctl.h, compat/keyring-linux.c used if found and enabled.
+AC_ARG_ENABLE(
+	keyring,
+	AS_HELP_STRING(--disable-keyring, disable giving the server its own Linux session keyring)
+)
+if test "x$enable_keyring" != xno; then
+	AC_CHECK_HEADER(linux/keyctl.h, found_keyctl=yes, found_keyctl=no)
+	if test "x$found_keyctl" = xyes; then
 		AC_DEFINE(HAVE_KEYCTL)
+	elif test "x$enable_keyring" = xyes; then
+		AC_MSG_ERROR("linux/keyctl.h not found")
+	fi
 fi
 AM_CONDITIONAL(HAVE_KEYCTL, [test "x$found_keyctl" = xyes])
 

options-table.c

@@ -532,14 +532,6 @@ const struct options_table_entry options_table[] = {
 	  .text = "Maximum number of commands to keep in history."
 	},
 
-	{ .name = "session-keyring",
-	  .type = OPTIONS_TABLE_FLAG,
-	  .scope = OPTIONS_TABLE_SERVER,
-	  .default_num = 1,
-	  .text = "Whether the server should join a new session keyring "
-		  "(Linux only)."
-	},
-
 	{ .name = "set-clipboard",
 	  .type = OPTIONS_TABLE_CHOICE,
 	  .scope = OPTIONS_TABLE_SERVER,

regress/session-keyring.sh

@@ -1,8 +1,8 @@
 #!/bin/sh
 
-# On Linux the server should join a session keyring of its own unless the
-# session-keyring option is off, so it keeps working after the login session's
-# keyring is revoked, and revoke it when it exits.
+# On Linux the server should join a session keyring of its own, so it keeps
+# working after the login session's keyring is revoked, and revoke it when it
+# exits.
 
 PATH=/bin:/usr/bin
 TERM=screen
@@ -12,10 +12,8 @@ keyctl session - true >/dev/null 2>&1 || exit 0
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
 OUT=$(mktemp -d)
-TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
-TMUX2="$TEST_TMUX -LtestB$$ -f$OUT/conf"
+TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
-$TMUX2 kill-server 2>/dev/null
 
 fail()
 {
@@ -26,35 +24,11 @@ fail()
 cleanup()
 {
 	$TMUX kill-server 2>/dev/null
-	$TMUX2 kill-server 2>/dev/null
 	[ -s $OUT/holder ] && kill $(cat $OUT/holder) 2>/dev/null
 	rm -rf "$OUT"
 }
 trap cleanup 0 1 15
 
-# Set KEYRING to the session keyring of a new pane on server $1.
-pane_keyring()
-{
-	$1 new-window -d "keyctl id @s >$OUT/pane 2>&1; $1 wait-for -S pane" ||
-		fail "could not create pane"
-	$1 wait-for pane
-	KEYRING=$(cat $OUT/pane)
-	case "$KEYRING" in
-	''|*[!0-9]*)
-		fail "pane keyring not usable: $KEYRING"
-		;;
-	esac
-}
-
-# With the option off, the server should keep the keyring it was started with.
-echo 'set -g session-keyring off' >$OUT/conf
-OFF=$(keyctl session - sh -c "
-	$TMUX2 new -d 'sleep 1000' && keyctl id @s
-" 2>/dev/null) || fail "could not start server"
-pane_keyring "$TMUX2"
-[ "$KEYRING" = "$OFF" ] || fail "pane has a new keyring with option off"
-$TMUX2 kill-server
-
 # Start the server from a login session with its own keyring, then revoke that
 # keyring as pam_keyinit(8) does when the login session ends.
 LOGIN=$(keyctl session - sh -c "
@@ -62,7 +36,15 @@ LOGIN=$(keyctl session - sh -c "
 " 2>/dev/null) || fail "could not start server"
 
 # A new pane should still have a usable keyring, with the user keyring linked.
-pane_keyring "$TMUX"
+$TMUX new-window -d "keyctl id @s >$OUT/pane 2>&1; $TMUX wait-for -S pane" ||
+	fail "could not create pane"
+$TMUX wait-for pane
+KEYRING=$(cat $OUT/pane)
+case "$KEYRING" in
+''|*[!0-9]*)
+	fail "pane keyring not usable: $KEYRING"
+	;;
+esac
 [ "$KEYRING" != "$LOGIN" ] || fail "pane has the login keyring"
 keyctl rlist $KEYRING | grep -qw "$(keyctl id @u)" ||
 	fail "user keyring not linked"

server.c

@@ -220,6 +220,10 @@ server_start(struct tmuxproc *client, uint64_t flags, struct event_base *base,
 	TAILQ_INIT(&message_log);
 	gettimeofday(&start_time, NULL);
 
+#ifdef HAVE_KEYCTL
+	new_session_keyring();
+#endif
+
 #ifdef HAVE_SYSTEMD
 	server_fd = systemd_create_socket(flags, &cause);
 #else
@@ -260,7 +264,7 @@ server_start(struct tmuxproc *client, uint64_t flags, struct event_base *base,
 	job_kill_all();
 	prompt_save_history();
 #ifdef HAVE_KEYCTL
-	keyring_revoke();
+	revoke_session_keyring();
 #endif
 
 	exit(0);

tmux.1

@@ -5096,14 +5096,6 @@ each client.
 .It Ic prompt\-history\-limit Ar number
 Set the number of history items to save in the history file for each type of
 command prompt.
-.It Xo Ic session\-keyring
-.Op Cm on | off
-.Xc
-On Linux, if enabled (the default), the server joins a new session keyring with
-the user keyring linked into it, rather than keeping the session keyring of the
-login session it was started from, which may be revoked when that session ends.
-The new keyring is revoked when the server exits.
-This option is checked once the configuration file has been loaded.
 .It Xo Ic set\-clipboard
 .Op Cm on | external | off
 .Xc