Add mitigation against DoS from thousands of parts.

A demonstration attack using a million tiny parts will freeze Mutt for
several minutes.  This is actually better than some other mail
software, but can still be a problem at large levels.

For now, set it to a very conservative 5000, but this can be adjusted
up (or down) if necessary.

Declare the previous stack-limit max depth as a constant too, and
decrease it down to 50.  Change the handler to return non-fatal "1" on
reaching the limit.

1 files changed, 2 insertions, 2 deletions

diff --git a/handler.c b/handler.c
index 36f4b997..f5a71628 100644
--- a/handler.c
+++ b/handler.c
@@ -1782,10 +1782,10 @@ int mutt_body_handler (BODY *b, STATE *s)
 
   int oflags = s->flags;
 
-  if (recurse_level >= 100)
+  if (recurse_level >= MUTT_MIME_MAX_DEPTH)
   {
     dprint (1, (debugfile, "mutt_body_handler: recurse level too deep. giving up!\n"));
-    return -1;
+    return 1;
   }
   recurse_level++;