terminal: Escape sequence handling fixes

Upgrade and refactor terminal_data to properly handle non-csi escape
codes, control characters in escape codes, and invalid escape sequences.
Also fix a buffer overflow in the escape sequence buffer.

Signed-off-by: Callum Lowcay <callum@callumscode.com>

diff --git a/clients/terminal.c b/clients/terminal.c
index 3c7be25..26f8c9d 100644 (file)
--- a/clients/terminal.c
+++ b/clients/terminal.c
@@ -52,6 +52,10 @@ static int option_fullscreen;
 #define ATTRMASK_BLINK         0x04
 #define ATTRMASK_INVERSE       0x08
 
+/* Buffer sizes */
+#define MAX_RESPONSE           11
+#define MAX_ESCAPE             64
+
 union utf8_char {
        unsigned char byte[4];
        uint32_t ch;
@@ -189,9 +193,10 @@ struct terminal {
        int fd, master;
        GIOChannel *channel;
        uint32_t modifiers;
-       char escape[64];
+       char escape[MAX_ESCAPE];
        int escape_length;
        int state;
+       int qmark_flag;
        struct utf8_state_machine state_machine;
        int margin;
        int fullscreen;
@@ -513,11 +518,16 @@ redraw_handler(struct window *window, void *data)
 
 #define STATE_NORMAL 0
 #define STATE_ESCAPE 1
+#define STATE_ESCAPE_SPECIAL 2
+#define STATE_ESCAPE_CSI  3
 
 static void
 terminal_data(struct terminal *terminal, const char *data, size_t length);
 
 static void
+handle_char(struct terminal *terminal, union utf8_char utf8);
+
+static void
 handle_sgr(struct terminal *terminal, int code);
 
 static void
@@ -629,14 +639,22 @@ handle_escape(struct terminal *terminal)
                }
                break;
        default:
-               terminal_data(terminal,
-                             terminal->escape + 1,
-                             terminal->escape_length - 2);
+               fprintf(stderr, "Unknown CSI escape: %c\n", *p);
                break;
        }       
 }
 
 static void
+handle_non_csi_escape(struct terminal *terminal, char code)
+{
+}
+
+static void
+handle_special_escape(struct terminal *terminal, char special, char code)
+{
+}
+
+static void
 handle_sgr(struct terminal *terminal, int code)
 {
        switch(code) {
@@ -698,14 +716,99 @@ handle_sgr(struct terminal *terminal, int code)
        }
 }
 
+/* Returns 1 if c was special, otherwise 0 */
+static int
+handle_special_char(struct terminal *terminal, char c)
+{
+       union utf8_char *row;
+       struct attr *attr_row;
+       
+       row = terminal_get_row(terminal, terminal->row);
+       attr_row = terminal_get_attr_row(terminal, terminal->row);
+       
+       switch(c) {
+       case '\r':
+               terminal->column = 0;
+               break;
+       case '\n':
+               terminal->column = 0;
+               /* fallthrough */
+       case '\v':
+       case '\f':
+               if (terminal->row + 1 < terminal->height) {
+                       terminal->row++;
+               } else {
+                       terminal->start++;
+                       if (terminal->start == terminal->height)
+                               terminal->start = 0;
+                       memset(terminal_get_row(terminal, terminal->row),
+                              0, terminal->width * sizeof(union utf8_char));
+                       attr_init(terminal_get_attr_row(terminal, terminal->row),
+                                 terminal->curr_attr, terminal->width);
+               }
+
+               break;
+       case '\t':
+               memset(&row[terminal->column], ' ', (-terminal->column & 7) * sizeof(union utf8_char));
+               attr_init(&attr_row[terminal->column], terminal->curr_attr, -terminal->column & 7);
+               terminal->column = (terminal->column + 7) & ~7;
+               break;
+       case '\b':
+               if (terminal->column > 0)
+                       terminal->column--;
+               break;
+       case '\a':
+               /* Bell */
+               break;
+       default:
+               return 0;
+       }
+       
+       return 1;
+}
+
+static void
+handle_char(struct terminal *terminal, union utf8_char utf8)
+{
+       union utf8_char *row;
+       struct attr *attr_row;
+       
+       if (handle_special_char(terminal, utf8.byte[0])) return;
+       
+       /* There are a whole lot of non-characters, control codes,
+        * and formatting codes that should probably be ignored,
+        * for example: */
+       if (strncmp((char*) utf8.byte, "\xEF\xBB\xBF", 3) == 0) {
+               /* BOM, ignore */
+               return;
+       } 
+       
+       /* Some of these non-characters should be translated, e.g.: */
+       if (utf8.byte[0] < 32) {
+               utf8.byte[0] = utf8.byte[0] + 64;
+       }
+       
+       /* handle right margin effects */
+       if (terminal->column >= terminal->width) {
+               terminal->column--;
+       }
+       
+       row = terminal_get_row(terminal, terminal->row);
+       attr_row = terminal_get_attr_row(terminal, terminal->row);
+       
+       row[terminal->column] = utf8;
+       attr_row[terminal->column++] = terminal->curr_attr;
+
+       if (utf8.ch != terminal->last_char.ch)
+               terminal->last_char = utf8;
+}
+
 static void
 terminal_data(struct terminal *terminal, const char *data, size_t length)
 {
        int i;
        union utf8_char utf8;
        enum utf8_state parser_state;
-       union utf8_char *row;
-       struct attr *attr_row;
 
        for (i = 0; i < length; i++) {
                parser_state =
@@ -725,69 +828,65 @@ terminal_data(struct terminal *terminal, const char *data, size_t length)
                        continue;
                }
 
-               row = terminal_get_row(terminal, terminal->row);
-               attr_row = terminal_get_attr_row(terminal, terminal->row);
-
+               /* assume escape codes never use non-ASCII characters */
                if (terminal->state == STATE_ESCAPE) {
                        terminal->escape[terminal->escape_length++] = utf8.byte[0];
-                       if (terminal->escape_length == 2 && utf8.byte[0] != '[') {
-                               /* Bad escape sequence. */
+                       if (utf8.byte[0] == '[') {
+                               terminal->state = STATE_ESCAPE_CSI;
+                               continue;
+                       } else if (utf8.byte[0] == '#' || utf8.byte[0] == '(' ||
+                               utf8.byte[0] == ')')
+                       {
+                               terminal->state = STATE_ESCAPE_SPECIAL;
+                               continue;
+                       } else {
                                terminal->state = STATE_NORMAL;
-                               goto cancel_escape;
+                               handle_non_csi_escape(terminal, utf8.byte[0]);
+                               continue;
                        }
-
-                       if (isalpha(utf8.byte[0])) {
+               } else if (terminal->state == STATE_ESCAPE_SPECIAL) {
+                       terminal->escape[terminal->escape_length++] = utf8.byte[0];
+                       terminal->state = STATE_NORMAL;
+                       if (isdigit(utf8.byte[0]) || isalpha(utf8.byte[0])) {
+                               handle_special_escape(terminal, terminal->escape[1],
+                                                     utf8.byte[0]);
+                               continue;
+                       }
+               } else if (terminal->state == STATE_ESCAPE_CSI) {
+                       if (handle_special_char(terminal, utf8.byte[0]) != 0) {
+                               /* do nothing */
+                       } else if (utf8.byte[0] == '?') {
+                               terminal->qmark_flag = 1;
+                       } else {
+                               /* Don't overflow the buffer */
+                               if (terminal->escape_length < MAX_ESCAPE)
+                                       terminal->escape[terminal->escape_length++] = utf8.byte[0];
+                               if (terminal->escape_length >= MAX_ESCAPE)
+                                       terminal->state = STATE_NORMAL;
+                       }
+                       
+                       if (isalpha(utf8.byte[0]) || utf8.byte[0] == '@' ||
+                               utf8.byte[0] == '`')
+                       {
                                terminal->state = STATE_NORMAL;
                                handle_escape(terminal);
-                       } 
-                       continue;
-               }
-
-       cancel_escape:
-               switch (utf8.byte[0]) {
-               case '\r':
-                       terminal->column = 0;
-                       break;
-               case '\n':
-                       terminal->column = 0;
-                       if (terminal->row + 1 < terminal->height) {
-                               terminal->row++;
+                               continue;
                        } else {
-                               terminal->start++;
-                               if (terminal->start == terminal->height)
-                                       terminal->start = 0;
-                               memset(terminal_get_row(terminal, terminal->row),
-                                      0, terminal->width * sizeof(union utf8_char));
-                               attr_init(terminal_get_attr_row(terminal, terminal->row),
-                                         terminal->curr_attr, terminal->width);
+                               continue;
                        }
+               }
 
-                       break;
-               case '\t':
-                       memset(&row[terminal->column], ' ', (-terminal->column & 7) * sizeof(union utf8_char));
-                       attr_init(&attr_row[terminal->column], terminal->curr_attr, -terminal->column & 7);
-                       terminal->column = (terminal->column + 7) & ~7;
-                       break;
-               case '\e':
+               /* this is valid, because ASCII characters are never used to
+                * introduce a multibyte sequence in UTF-8 */
+               if (utf8.byte[0] == '\e') {
                        terminal->state = STATE_ESCAPE;
                        terminal->escape[0] = '\e';
                        terminal->escape_length = 1;
-                       break;
-               case '\b':
-                       if (terminal->column > 0)
-                               terminal->column--;
-                       break;
-               case '\a':
-                       /* Bell */
-                       break;
-               default:
-                       if (terminal->column < terminal->width)
-                               if (utf8.byte[0] < 32) utf8.byte[0] += 64;
-                       row[terminal->column] = utf8;
-                       attr_row[terminal->column++] = terminal->curr_attr;
-                       break;
-               }
-       }
+                       terminal->qmark_flag = 0;
+               } else {
+                       handle_char(terminal, utf8);
+               } /* if */
+       } /* for */
 
        window_schedule_redraw(terminal->window);
 }