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Cryptographic splicing makes for a Wordpress vulnerability

Cryptographic splicing makes for a Wordpress vulnerability

Posted May 16, 2008 12:15 UTC (Fri) by robbe (subscriber, #16131)
In reply to: Cryptographic splicing makes for a Wordpress vulnerability by giraffedata
Parent article: Cryptographic splicing makes for a Wordpress vulnerability

> The explanation misses a lot of details.

Here's my understanding (only from the article, YMMV):

0. Assume that there is an "admin" account with special power, and that 
the attacker has created an "admin99" account.
1. The attacker successfully logs in via a form, and the server sends her 
the cookie "admin99|20080601|DEADBEEF". (Assume that md5
("admin9920080601secret") == "DEADBEEF".)
2. On subsequent requests the attacker presents the above cookie. The 
server notices that the cookie is valid (because md5
("admin9920080601secret") == "DEADBEEF"), that this is user "admin99", 
and that the session has not yet expired (it's still May 2008). Fine!
3. But now the attacker sends the following doctored cookie: "admin|
9920080601|DEADBEEF". This still checks out as valid because md5
("admin9920080601secret") == "DEADBEEF"), the session is for some 
reason[1] still not considered expired, so the attacker now has the 
identity of user "admin".

[1] IMO not validating the expiration date format is one of the main 
errors here. Or does WP strive to be Y10K compliant??


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Cryptographic splicing makes for a Wordpress vulnerability

Posted May 16, 2008 13:37 UTC (Fri) by jake (editor, #205) [Link]

> IMO not validating the expiration date format is one of the main 
> errors here. Or does WP strive to be Y10K compliant??

In the article, I was trying to steer clear of providing complete, exploitable details while
still giving more details than the advisory.  I believe the expiration is actually the number
of seconds since the epoch, which may be easier to exploit and still validate as a reasonable
expiration.

jake


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