Or you aren't understanding the key statement of his comment
> You'd have to find collisions that are of an identical length and still be useful
Creating a collision is possible, making it work in a way that conforms to the manner of which Git uses SHA1 and also provides the malicious code is the part that the Shattered research did not prove possible.
Git doesn't simply SHA-1 a file or the repo, it's more than that.
Linus:
> I haven't seen the attack yet, but git doesn't actually just hash the data, it does prepend a type/length field to it. That usually tends to make collision attacks much harder, because you either have to make the resulting size the same too, or you have to be able to also edit the size field in the header.
> You'd have to find collisions that are of an identical length and still be useful
Creating a collision is possible, making it work in a way that conforms to the manner of which Git uses SHA1 and also provides the malicious code is the part that the Shattered research did not prove possible.
Git doesn't simply SHA-1 a file or the repo, it's more than that.
Linus:
> I haven't seen the attack yet, but git doesn't actually just hash the data, it does prepend a type/length field to it. That usually tends to make collision attacks much harder, because you either have to make the resulting size the same too, or you have to be able to also edit the size field in the header.
[https://stackoverflow.com/questions/42433126/how-does-the-ne...]