'Padding Oracle' Crypto Attack Affects Millions of ASP.NET Apps

[Kevin W. Wall]

Peter Gutmann wrote:
> Tom Ritter <tom at ritter.vg> writes:
> 
>> What's weird is I find confusing literature about what *is* the default for
>> protecting the viewstate.
> 
> I still haven't seen the paper/slides from the talk so it's a bit hard to
> comment on the specifics, but if you're using .NET's FormsAuthenticationTicket
> (for cookie-based auth, not viewstate protection) then you get MAC protection
> built-in, along with other nice features like sliding cookie expiration (the
> cookie expires relative to the last active use of the site rather than an
> absolute time after it was set).  I've used it in the past as an example of
> how to do cookie-based auth right

FYI...I just received confirmation from my company's on-site consultant from
Microsoft that .NET's FormsAuthenticationTicket is also vulnerable to
this padding oracle attack. So apparently Microsoft didn't apply the MAC
protection quite right in their implementation.

-kevin
-- 
Kevin W. Wall
"The most likely way for the world to be destroyed, most experts agree,
is by accident. That's where we come in; we're computer professionals.
We cause accidents."        -- Nathaniel Borenstein, co-creator of MIME

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