GUACAMOLE-573: Ensure scrollback buffer bounds cannot be exceeded. Remove incorrect bounds checks.

src/terminal/buffer.c

@@ -83,12 +83,10 @@ guac_terminal_buffer_row* guac_terminal_buffer_get_row(guac_terminal_buffer* buf
     guac_terminal_char* first;
     guac_terminal_buffer_row* buffer_row;
 
-    /* Calculate scrollback row index */
-    int index = buffer->top + row;
+    /* Normalize row index into a scrollback buffer index */
+    int index = (buffer->top + row) % buffer->available;
     if (index < 0)
         index += buffer->available;
-    else if (index >= buffer->available)
-        index -= buffer->available;
 
     /* Get row */
     buffer_row = &(buffer->rows[index]);

src/terminal/select.c

@@ -149,12 +149,6 @@ static int guac_terminal_find_char(guac_terminal* terminal,
 
     int start_column = *column;
 
-    /* If requested row is outside the bounds of the current terminal or
-     * scrollback, assume the character is 1 column wide */
-    if (row >= terminal->term_height
-            || row < terminal->term_height - terminal->buffer->length)
-        return 1;
-
     guac_terminal_buffer_row* buffer_row = guac_terminal_buffer_get_row(terminal->buffer, row, 0);
     if (start_column < buffer_row->length) {
 
@@ -291,12 +285,6 @@ static void guac_terminal_clipboard_append_row(guac_terminal* terminal,
     char buffer[1024];
     int i = start;
 
-    /* If requested row is outside the bounds of the current terminal or
-     * scrollback, do nothing */
-    if (row >= terminal->term_height
-            || row < terminal->term_height - terminal->buffer->length)
-        return;
-
     guac_terminal_buffer_row* buffer_row =
         guac_terminal_buffer_get_row(terminal->buffer, row, 0);
 

src/terminal/terminal/buffer.h

@@ -70,7 +70,10 @@ typedef struct guac_terminal_buffer {
     guac_terminal_buffer_row* rows;
 
     /**
-     * The row to replace when adding a new row to the buffer.
+     * The index of the first row in the buffer (the row which represents row 0
+     * with respect to the terminal display). This is also the index of the row
+     * to replace when insufficient space remains in the buffer to add a new
+     * row.
      */
     int top;