[cryptography] How are expired code-signing certs revoked?

Steven Bellovin smb at cs.columbia.edu
Fri Dec 9 17:08:43 EST 2011


On Dec 9, 2011, at 3:46 18PM, Jon Callas wrote:

> 
> On 8 Dec, 2011, at 8:27 PM, Peter Gutmann wrote:
> 
>> In any case getting signing certs really isn't hard at all.  I once managed it 
>> in under a minute (knowing which Google search term to enter to find caches of 
>> Zeus stolen keys helps :-).  That's as an outsider, if you're working inside 
>> the malware ecosystem you'd probably get them in bulk from whoever's dealing 
>> in them (single botnets have been reported with thousands of stolen keys and 
>> certs in their data stores, so it's not like the bad guys are going to run out 
>> of them in a hurry).
>> 
>> Unlike credit cards and bank accounts and whatnot we don't have price figures 
>> for stolen certs, but I suspect it's not that much.
> 
> If it were hard to get signing certs, then we as a community of developers would demonize the practice as having to get a license to code.
> 
Peter is talking about stolen certs, which for most parts of the development
community aren't a prerequisite...  But there's an interesting dilemma here
if we insist on all code being signed.

Assume that a code-signing cert costs {$,€,£,zorkmid}10000/year.  Everyone but
large companies would scream.  Now assume the cost is {$,€,£,zorkmid}.01/year
or even free.  At that price, it's a nuisance factor, and would be issued via
a simple web interface.  Simple web interfaces are scriptable (and we all know
the limits of captchas), which means that malware could include a "get a cert"
routine for the next, mutated generation of itself.  In fact, they're largely
price-insensitive, since they'd be programmed with a stash of stolen credit
cards....


		--Steve Bellovin, https://www.cs.columbia.edu/~smb








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