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List:       bugtraq
Subject:    Re: ASP.NET __VIEWSTATE crypto validation prone to replay attacks
From:       Michal Zalewski <lcamtuf () gmail ! com>
Date:       2005-05-05 20:06:21
Message-ID: 1e89feb30505051306458c1e4 () mail ! gmail ! com
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> Microsoft has addressed your issues 1-a, 1-b and 1-c by adding a
> property "ViewStateUserKey" to the System.Web.UI.Page class in
> .NET Framework 1.1.  The documentation for this property is here:

No, I think this statement is simply not true. The key is intended to
solve a wholly different class of problems, and has nothing to do with
replay attacks I reported.

Reported issue 1-a: same user moves __VIEWSTATE from one page to
another. Adding unique user identifier to __VIEWSTATE does not help,
because in both cases, it's precisely the same user within the same
system.

Reported issue 1-b: same user retains __VIEWSTATE and reuses it at a
later date. Again, it's precisely the same person and the same unique
ID.

Reported issue 1-c: this is the least relevant of all reported
problems, and indeed can be in some situations mitigated by binding
__VIEWSTATE data to a specific user.

/mz

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