[OpenSER-Users] sanitizing sip requests

[Jiri Kuthan]

At 18:13 17/10/2007, William Quan wrote:
>Hi all,
>I came across a security alert that basically embeds javascript in the
>display name of the From to initiate cross-site-scripting (XSS) attacks.
>Here is an example:
>
>From: "<script>alert('hack')</script>""user"
><sip:user at domain.com <https://lists.grok.org.uk/mailman/listinfo/full-disclosure>>;tag=002a000c
>
>
>Grammatically , I don't see an issue with this. However, under the right
>circumstances this could get ugly.
>Do you see value in having openser take a proactive role to detect these
>and reject calls?  Or is this outside the scope of what a proxy should
>be doing (leave it to the UA to sanitize) ?

We have been thinking hard of this in the SER community. My 2 cents are that 
sanitizing in the proxy is of limited impact. The trouble is that it is not
just JavaScript, it can be literally any application in any language, which
is tunneled some crafted data through SIP. The SIP proxy can be tought to
detect JavaScript but who knows what is going to come next. Thus I think
that JAva-Script enabled apps should test SER-produced data for Java-script
data, and XYZ-apps should test SER-produced data for XYZ-script data.

As an example, the latest serweb version, which uses JavaScript, is resistant
against such JavaScript attacks.

-jiri


>Looking to get your thoughts-
>-will
>
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--
Jiri Kuthan            http://iptel.org/~jiri/