ptyfwd: ellipsize overly long window titles

Apparently some terminal emulators have problems with overly long
titles, hence truncate them at some safe length (128).

Also, when parsing ANSI sequences ourselves accept longer sequences
(192), after all we should be fine when parsing our own title sequences.

Fixes: #35104

1 files changed, 20 insertions, 4 deletions

diff --git a/src/shared/ptyfwd.c b/src/shared/ptyfwd.c
index c1e3b7180b..72f91b0b62 100644
--- a/src/shared/ptyfwd.c
+++ b/src/shared/ptyfwd.c
@@ -42,6 +42,11 @@ typedef enum AnsiColorState  {
         _ANSI_COLOR_STATE_INVALID = -EINVAL,
 } AnsiColorState;
 
+#define ANSI_SEQUENCE_LENGTH_MAX 192U
+#define ANSI_SEQUENCE_WINDOW_TITLE_MAX 128U
+
+assert_cc(ANSI_SEQUENCE_LENGTH_MAX > ANSI_SEQUENCE_WINDOW_TITLE_MAX);
+
 struct PTYForward {
         sd_event *event;
 
@@ -463,7 +468,7 @@ static int pty_forward_ansi_process(PTYForward *f, size_t offset) {
                                 /* If this is a "parameter" or "intermediary" byte (i.e. ranges 0x20…0x2F and
                                  * 0x30…0x3F) then we are still in the CSI sequence */
 
-                                if (strlen_ptr(f->csi_sequence) >= 64) {
+                                if (strlen_ptr(f->csi_sequence) >= ANSI_SEQUENCE_LENGTH_MAX) {
                                         /* Safety check: lets not accept unbounded CSI sequences */
 
                                         f->csi_sequence = mfree(f->csi_sequence);
@@ -498,7 +503,7 @@ static int pty_forward_ansi_process(PTYForward *f, size_t offset) {
                 case ANSI_COLOR_STATE_OSC_SEQUENCE:
 
                         if ((uint8_t) c >= ' ') {
-                                if (strlen_ptr(f->osc_sequence) >= 64) {
+                                if (strlen_ptr(f->osc_sequence) >= ANSI_SEQUENCE_LENGTH_MAX) {
                                         /* Safety check: lets not accept unbounded OSC sequences */
                                         f->osc_sequence = mfree(f->osc_sequence);
                                         break;
@@ -1115,7 +1120,18 @@ int pty_forward_set_title(PTYForward *f, const char *title) {
         if (f->out_buffer_size > 0)
                 return -EBUSY;
 
-        return free_and_strdup(&f->title, title);
+        if (!title) {
+                f->title = mfree(f->title);
+                return 0;
+        }
+
+        /* Truncate the title to 128 chars, since some terminal emulators really don't like overly long ANSI
+         * sequences */
+        _cleanup_free_ char *ellipsized = ellipsize(title, ANSI_SEQUENCE_WINDOW_TITLE_MAX, 66);
+        if (!ellipsized)
+                return -ENOMEM;
+
+        return free_and_replace(f->title, ellipsized);
 }
 
 int pty_forward_set_titlef(PTYForward *f, const char *format, ...) {
@@ -1135,7 +1151,7 @@ int pty_forward_set_titlef(PTYForward *f, const char *format, ...) {
         if (r < 0)
                 return -ENOMEM;
 
-        return free_and_replace(f->title, title);
+        return pty_forward_set_title(f, title);
 }
 
 int pty_forward_set_title_prefix(PTYForward *f, const char *title_prefix) {