[Seaside] Bug in WAAbstractFileLibrary

Joachim Tuchel jtuchel at objektfabrik.de
Mon Apr 14 04:01:46 UTC 2014

Hi there,

over the last few nights, our Seaside Application was bombarded with 
requests that were formed like this:


The attacks did also try other javascript expressions.

Unfortunately, WAAbstractFileLibrary reacts to this by throwing a 
primitive failed on VA Smalltalk in WAAbstractFileLibrary 
class>>#asSelector:, because the javascript expression cannot be 
interpreted as a filename.

Here's an excerpt of our walkback that shows what's going on.

   receiver = ''
   receiver = ''
   arg1 = 1
   receiver = ''
JQUiDeploymentLibrary class(WAAbstractFileLibrary class)>>#asSelector:
   receiver = JQUiDeploymentLibrary
   arg1 = ').find('
   temp1 = ''
   temp2 = nil
   receiver = a JQUiDeploymentLibrary
   arg1 = ').find('
   receiver = a JQUiDeploymentLibrary
   arg1 = a WARequestContext url: '/files/JQUiDeploymentLibrary/%29.find%28'
   temp1 = ').find('
   temp2 = nil
   temp3 = nil
JQUiDeploymentLibrary class(WAAbstractFileLibrary class)>>#handle:
   receiver = JQUiDeploymentLibrary
   arg1 = a WARequestContext url: '/files/JQUiDeploymentLibrary/%29.find%28'

I am on the road and have no pharo/seaside image with me, but if I 
remember correctly, pharo does not throw an exception when you ask an 
empty string for its #first character, I seem to remember it just 
returns nil. VA Smalltalk does throw an exception. It does not stop 
working, so this is not a critical problem.

However, I think an additional check in #asSelector: wouldn't hurt 
because then the result is an http error code 404, which can either be 
returned to the client or removed by filters like mod_security.

So here is a fix for WAAbstractFileLibrary class>>asSelector: that I 
suggest for inclusion in Seaside, even if it is unnecessary for Pharo:

asSelector: aFilename
     | mainPart extension |
     mainPart := (aFilename copyUpToLast: $.)
         select: [ :each | each isAlphaNumeric ].

     mainPart isEmptyOrNil ifTrue: [^nil].

     [ mainPart first isDigit ]
         whileTrue: [ mainPart := mainPart allButFirst ].
     extension := (aFilename copyAfterLast: $.) asLowercase capitalized.
     ^ (mainPart, extension) asSymbol


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