Straw Poll -- Weak SSL/SSH keys

David Cantrell david at
Tue Jun 17 11:54:27 BST 2008

On Mon, Jun 16, 2008 at 11:26:48AM +0100, Jonathan Bennett wrote:

> ... Debian weak keys issue ...
> Some of these are SSL servers, like wot is used to do e-commerce, an' 
> that. The issue here is that, in theory, an attacker could decrypt the 
> traffic and recover your credit card details, since brute forcing the 
> server's private key is that much easier. You could also be talking to a 
> fake server for the same reason, but this doesn't make much difference 
> to the information an attacker can collect.
> What I'd like to know is:
> 1) Do you care?
> 2) If not, why not?

No.  I always use a credit card online so if bad shit happens I'll get a
refund from them.  And also ...

> 3) Would you ever bother testing a site's certificate for a weak key 
> before doing business with them?

No.  The dangers of packet sniffing are, IMO, greatly overstated.  To
sniff the packets between me and, say, amazon, requires that someone
compromise one of the routers in between, or add a router, or compromise
Amazon's or my machine, or sniff the wireless bit at my end.

We can ignore a router compromise, because they don't log packet
contents, so to do any useful analysis you'd need to send the packets
elsewhere.  And to do that in bulk would be a noticeable amount of
traffic and one would hope that the ISP in question would notice.  So
it's only going to be done for very carefully targeted IP addresses.
Amazon's ain't one of them cos the volume is too high.  Mine ain't one
of them because the payoff isn't high.  You want to pick on a small
business that does lots of online transactions every day.

We can ignore adding a router, for obvious reasons.

Likewise we can ignore compromising my machines.  If someone gets
naughty code into Amazon's machines, they're hardly likely to sniff
packets from me.  They're going to go for the database of credit card

So the biggest risk is my wireless network.  But really, if someone
wants to sniff lucrative packets, doing it outside my flat ain't a good
use of their time.  There's only three networks visible, of which mine
is by far the busiest, and even that only sees card details go over it
maybe once a week.  A dodgy geezer would do far better to lurk in the
"internet cafe" a few streets away.

I wouldn't bother to check my bank's cert because I believe they're a
Sun shop, and even if they *have* got a dodgy cert, the worst someone
could do would be to look at the web pages I look at in my online
banking.  They wouldn't be able log in as me cos they don't have my card
to go in the card reader.  Yes, in theory they could snoop the entire
session and inject page requests and transfer money around.  But the
worst they can do in that very unlikely case without having my card is
to pay someone with whom I already have a relationship.  That would be
mildly annoying, but it wouldn't exactly be difficult for me to get my
money back.  And then after they'd done that I might bother to turn
IPsec back on across my wireless network instead of just having it

David Cantrell | Nth greatest programmer in the world

  Longum iter est per praecepta, breve et efficax per exempla.

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