[Seaside] Bug in WAAbstractFileLibrary

[Philippe Marschall]

On Mon, Apr 14, 2014 at 6:01 AM, Joachim Tuchel <jtuchel at objektfabrik.de> wrote:
> Hi there,
>
> over the last few nights, our Seaside Application was bombarded with
> requests that were formed like this:
>
> /files/JQUiDeploymentLibrary/%29.find%28
>
> 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.
>
> String(Object)>>#primitiveFailed
>   receiver = ''
> String>>#at:
>   receiver = ''
>   arg1 = 1
> String(SequenceableCollection)>>#first
>   receiver = ''
> JQUiDeploymentLibrary class(WAAbstractFileLibrary class)>>#asSelector:
>   receiver = JQUiDeploymentLibrary
>   arg1 = ').find('
>   temp1 = ''
>   temp2 = nil
> JQUiDeploymentLibrary(WAAbstractFileLibrary)>>#asSelector:
>   receiver = a JQUiDeploymentLibrary
>   arg1 = ').find('
> JQUiDeploymentLibrary(WAFileLibrary)>>#handle:
>   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

https://code.google.com/p/seaside/issues/detail?id=786

Cheers
Philippe