CAcert System Admins discussion list

[Ian G <iang AT iang.org>]

OK, so it now seems that this is a stupid "null in string" issue that 
fools (?) both CAs and browsers.  This is not an attack on the protocol 
but "many implementations."

So big question for CAcert:  can a NULL be accepted in any string in the 
request for a certificate?  And result in a NULL into the cert itself?

So far the CAs that are embarrassed are unnamed...

iang


http://www.wired.com/threatlevel/2009/07/kaminsky/
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... When an attacker who owns his own domain — badguy.com — requests a 
certificate from the CA, the CA, using contact information from Whois 
records, sends him an email asking to confirm his ownership of the site. 
But an attacker can also request a certificate for a subdomain of his 
site, such as Paypal.com\0.badguy.com, using the null character \0 in 
the URL.

The CA will issue the certificate for a domain like 
PayPal.com\0.badguy.com because the hacker legitimately owns the root 
domain badguy.com.

Then, due to a flaw found in the way SSL is implemented in many 
browsers, Firefox and others theoretically can be fooled into reading 
his certificate as if it were one that came from the authentic PayPal 
site. Basically when these vulnerable browsers check the domain name 
contained in the attacker’s certificate, they stop reading any 
characters that follow the “\0″ in the name.

More significantly, an attacker can also register a wildcard domain, 
such as *\0.badguy.com, which would then give him a certificate that 
would allow him to masquerade as any site on the internet and intercept 
communication.
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