canvas: fix an integer overflow in caca_resize().

Fixes: #52 (CVE-2021-3410)

caca/canvas.c

@@ -45,6 +45,7 @@ static int caca_resize(caca_canvas_t *, int, int);
  *
  *  If an error occurs, NULL is returned and \b errno is set accordingly:
  *  - \c EINVAL Specified width or height is invalid.
+ *  - \c EOVERFLOW Specified width and height overflowed.
  *  - \c ENOMEM Not enough memory for the requested canvas size.
  *
  *  \param width The desired canvas width
@@ -200,6 +201,7 @@ int caca_unmanage_canvas(caca_canvas_t *cv, int (*callback)(void *), void *p)
  *
  *  If an error occurs, -1 is returned and \b errno is set accordingly:
  *  - \c EINVAL Specified width or height is invalid.
+ *  - \c EOVERFLOW Specified width and height overflowed.
  *  - \c EBUSY The canvas is in use by a display driver and cannot be resized.
  *  - \c ENOMEM Not enough memory for the requested canvas size. If this
  *    happens, the canvas handle becomes invalid and should not be used.
@@ -363,7 +365,7 @@ int caca_rand(int min, int max)
 
 int caca_resize(caca_canvas_t *cv, int width, int height)
 {
-    int x, y, f, old_width, old_height, new_size, old_size;
+    int x, y, f, old_width, old_height, old_size;
 
     old_width = cv->width;
     old_height = cv->height;
@@ -375,7 +377,14 @@ int caca_resize(caca_canvas_t *cv, int width, int height)
      * dirty rectangle handling */
     cv->width = width;
     cv->height = height;
-    new_size = width * height;
+    int new_size = width * height;
+
+    /* Check for overflow */
+    if (new_size / width != height)
+    {
+        seterrno(EOVERFLOW);
+        return -1;
+    }
 
     /* If width or height is smaller (or both), we have the opportunity to
      * reduce or even remove dirty rectangles */

caca/codec/import.c

@@ -61,6 +61,7 @@ static ssize_t import_caca(caca_canvas_t *, void const *, size_t);
  *
  *  If an error occurs, -1 is returned and \b errno is set accordingly:
  *  - \c ENOMEM Not enough memory to allocate canvas.
+ *  - \c EOVERFLOW Importing data caused a value overflow.
  *  - \c EINVAL Invalid format requested.
  *
  *  \param cv A libcaca canvas in which to import the file.

caca/codec/text.c

@@ -46,7 +46,7 @@ ssize_t _import_text(caca_canvas_t *cv, void const *data, size_t size)
     char const *text = (char const *)data;
     unsigned int width = 0, height = 0, x = 0, y = 0, i;
 
-    caca_set_canvas_size(cv, width, height);
+    caca_set_canvas_size(cv, 0, 0);
 
     for(i = 0; i < size; i++)
     {
@@ -70,15 +70,19 @@ ssize_t _import_text(caca_canvas_t *cv, void const *data, size_t size)
             if(y >= height)
                 height = y + 1;
 
-            caca_set_canvas_size(cv, width, height);
+            if (caca_set_canvas_size(cv, width, height) < 0)
+                return -1;
         }
 
         caca_put_char(cv, x, y, ch);
         x++;
     }
 
-    if(y > height)
-        caca_set_canvas_size(cv, width, height = y);
+    if (y > height)
+    {
+        if (caca_set_canvas_size(cv, width, height = y) < 0)
+            return -1;
+    }
 
     return (ssize_t)size;
 }
@@ -431,7 +435,8 @@ ssize_t _import_ansi(caca_canvas_t *cv, void const *data, size_t size, int utf8)
             {
                 savedattr = caca_get_attr(cv, -1, -1);
                 caca_set_attr(cv, im.clearattr);
-                caca_set_canvas_size(cv, width = x + wch, height);
+                if (caca_set_canvas_size(cv, width = x + wch, height) < 0)
+                    return -1;
                 caca_set_attr(cv, savedattr);
             }
             else
@@ -448,7 +453,8 @@ ssize_t _import_ansi(caca_canvas_t *cv, void const *data, size_t size, int utf8)
             caca_set_attr(cv, im.clearattr);
             if(growy)
             {
-                caca_set_canvas_size(cv, width, height = y + 1);
+                if (caca_set_canvas_size(cv, width, height = y + 1) < 0)
+                    return -1;
             }
             else
             {
@@ -480,7 +486,8 @@ ssize_t _import_ansi(caca_canvas_t *cv, void const *data, size_t size, int utf8)
     {
         savedattr = caca_get_attr(cv, -1, -1);
         caca_set_attr(cv, im.clearattr);
-        caca_set_canvas_size(cv, width, height = y);
+        if (caca_set_canvas_size(cv, width, height = y))
+            return -1;
         caca_set_attr(cv, savedattr);
     }