[PATCH] vt: detect and ignore OSC codes.

Adam Borowski
2014-02-19T00:38:31Z

These can be used to send commands consisting of an arbitrary string to the
terminal, most often used to set a terminal's window title or to redefine
the colour palette. Our console doesn't use OSC, unlike everything else,
which can lead to junk being displayed if a process sends such a code
unconditionally.

The rules for termination follow established practice rather than Ecma-48.
Ecma-48 requires the string to use only byte values 0x08..0x0D and
0x20..0x7E, terminated with either ESC \ or 0x9C. This would disallow using
8-bit characters, which are reasonable for example in window titles.
A widespread idiom is to terminate with 0x07. The behaviour for other
control characters differs between terminal emulators, I followed libvte and
xterm:
* 0x07 and ESC anything terminate
* nothing else terminates, all 8-bit values including 0x9C are considered a
part of the string

Signed-off-by: Adam Borowski <kilobyte@angband.pl>
---
drivers/tty/vt/vt.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index b7bde54..3ad0b61 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -1592,7 +1592,7 @@ static void restore_cur(struct vc_data *vc)

enum { ESnormal, ESesc, ESsquare, ESgetpars, ESfunckey,
EShash, ESsetG0, ESsetG1, ESpercent, ESignore, ESnonstd,
- ESpalette };
+ ESpalette, ESosc };

/* console_lock is held (except via vc_init()) */
static void reset_terminal(struct vc_data *vc, int do_clear)
@@ -1652,11 +1652,15 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c)
* Control characters can be used in the _middle_
* of an escape sequence.
*/
+ if (vc->vc_state == ESosc && c>=8 && c<=13) /* ... except for OSC */
+ return;
switch (c) {
case 0:
return;
case 7:
- if (vc->vc_bell_duration)
+ if (vc->vc_state == ESosc)
+ vc->vc_state = ESnormal;
+ else if (vc->vc_bell_duration)
kd_mksound(vc->vc_bell_pitch, vc->vc_bell_duration);
return;
case 8:
@@ -1767,7 +1771,9 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c)
} else if (c=='R') { /* reset palette */
reset_palette(vc);
vc->vc_state = ESnormal;
- } else
+ } else if (c>='0' && c<='9')
+ vc->vc_state = ESosc;
+ else
vc->vc_state = ESnormal;
return;
case ESpalette:
@@ -2021,6 +2027,8 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c)
vc->vc_translate = set_translate(vc->vc_G1_charset, vc);
vc->vc_state = ESnormal;
return;
+ case ESosc:
+ return;
default:
vc->vc_state = ESnormal;
}
--
1.9.0