The attacker could just send a very lot of data, with no \n and it would
all be buffered in memory until the kernel killed git-annex or perhaps OOM
killed some other more valuable process.
This is a low impact security hole, only affecting communication between
local git-annex and git-annex-shell on the remote system. (With either
able to be the attacker). Only those with the right ssh key can do it. And,
there are probably lots of ways to construct git repositories that make git
use a lot of memory in various ways, which would have similar impact as
this attack.
The fix in P2P/IO.hs would have been higher impact, if it had made it to a
released version, since it would have allowed DOSing the tor hidden
service without needing to authenticate.
(The LockContent and NotifyChanges instances may not be really
exploitable; since the line is read and ignored, it probably gets read
lazily and does not end up staying buffered in memory.)
A bit tricky since Proto doesn't support threads. Rather than adding
threading support to it, ended up using a callback that waits for both
data on a Handle, and incoming messages at the same time.
This commit was sponsored by Denis Dzyubenko on Patreon.
For use with tor hidden services, and perhaps other transports later.
Based on Utility.SimpleProtocol, it's a line-based protocol,
interspersed with transfers of bytestrings of a specified size.
Implementation of the local and remote sides of the protocol is done
using a free monad. This lets monadic code be included here, without
tying it to any particular way to get bytes peer-to-peer.
This adds a dependency on the haskell package "free", although that
was probably pulled in transitively from other dependencies already.
This commit was sponsored by Jeff Goeke-Smith on Patreon.
