Re: Re: Merge with git-pasky II.

> Almost all attacks on sha1 will depend on _replacing_ a file with a bogus
> new one. So guys, instead of using sha256 or going overboard, just make
> sure that when you synchronize, you NEVER import a file you already have.
>
> It's really that simple. Add "--ignore-existing" to your rsync scripts,
> and you're pretty much done. That guarantees that a new evil blob by the
> next mad scientist out to take over the world will never touch your
> repository, and if we make this part of the _standard_ scripts, then
> dammit, security is in good _practices_ rather than just relying blindly
> on the hash being secure.
>
> In other words, I think we could have used md5's as the hash, if we just
> make sure we have good practices. And it wouldn't have been "insecure".
>
> The fact is, you don't merge with people you don't trust. If you don't
> trust them, they have a much easier time corrupting your repository by
> just creating bugs in the code and checking that thing in. Who cares about
> hash collisions, when you can generate a kernel root vulnerability by just
> adding a single line of code and use the _correct_ hash for it.
>
> So the sha1 hash does not replace _trust_. That comes from something else
> altogether.