core: Assume box isn't metadata if > threshold [GH-3107]

CHANGELOG.md

@@ -6,6 +6,7 @@ BUG FIXES:
   - core: Rare EINVAL errors on box adding are gone. [GH-3094]
   - core: Upgrading the home directory for Vagrant 1.5 uses the Vagrant
     temp dir. [GH-3095]
+  - core: Assume a box isn't metadata if it exceeds 20 MB. [GH-3107]
 
 ## 1.5.0 (March 10, 2014)
 

lib/vagrant/action/builtin/box_add.rb

@@ -14,6 +14,10 @@ module Vagrant
       # This middleware will download a remote box and add it to the
       # given box collection.
       class BoxAdd
+        # This is the size in bytes that if a file exceeds, is considered
+        # to NOT be metadata.
+        METADATA_SIZE_LIMIT = 20971520
+
         def initialize(app, env)
           @app    = app
           @logger = Log4r::Logger.new("vagrant::action::builtin::box_add")
@@ -445,6 +449,12 @@ module Vagrant
 
             begin
               File.open(url, "r") do |f|
+                if f.size > METADATA_SIZE_LIMIT
+                  # Quit early, don't try to parse the JSON of gigabytes
+                  # of box files...
+                  return false
+                end
+
                 BoxMetadata.new(f)
               end
               return true