On Wed, 3 Aug 2016, Santiago Torres wrote:
So if you want to treat Git as a cryptographic end-to-end distribution
mechanism, then no, it fails horribly at that. But the state of the art
in source code distribution, no matter which system you use, is much
less advanced than that. People download tarballs, even ones with GPG
signatures, all the time without verifying their contents. Most packages
distribute a sha1sum or similar (sometimes even gpg-signed), but quite
often the source of authority is questionable.
Yes, this happens an awful lot of times. We did some work with python's
pypi last year, and we found out that less than 1% of people actually
downloaded the gpg signature for the package they are retrieving[1].
For example, consider somebody downloading a new package for the first
time. They don't know the author in any out-of-band way, so any
signatures are likely meaningless. They _might_ be depending on the
source domain for some security (and using some hierarchical PKI like
TLS+x.509 to be sure they're talking to that domain), but in your threat
model, even well-known hosts like FSF could be compromised internally.
So yes, I think the current state of affairs (especially open-source) is
that people download and run possibly-compromised code all the time. But
I'm not sure that lack of tool support is really the limiting factor. Or
that it has turned out to be all that big a problem in practice.
I couldn't agree more. I feel that OSS is slowly moving towards a more
cryptographically robust, trust-based way of doing things, which I find
pleasing.
It's too easy to look at this from purely a technical, cryptographic point of
view and miss a very important point.
It may be very easy to see that this was signed by "cool-internet-name" but how
can I tell if this is really Joe Blow the developer? and if it is, I still have
no way of knowing if he's working for the NSA or not.
The lack of meaningful termination of the signatures to the real world is why so
few people bother to check package signatures, etc.
David Lang
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