The git protocol and DoS

["H. Peter Anvin" <hpa@zytor.com>]

I've been concerned for a while that the git protocol may be inherently 
vulnerable to a "SYNful DoS" attack (spraying raw TCP SYN packets with 
enough data to start substantial server activity.)  Although SYN cookies 
protect against this to some degree, it makes me wonder if something 
should be added to the protocol itself.

One way to do this would be to start the transaction by having the 
server transmit a cookie to the client, and to require the client to 
send a SHA1 of the (cookie + request) together with the request.  This 
would be done with a fairly short timeout.

It would, however, require a protocol change; I would like to hear what 
people think about this at this stac=ge.

	-hpa