Hi Toke, On 1/13/22, Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote: > However, if we make this change, systems setting a stable_secret and > using addr_gen_mode 2 or 3 will come up with a completely different > address after a kernel upgrade. Which would be bad for any operator > expecting to be able to find their machine again after a reboot, > especially if it is accessed remotely. > > I haven't ever used this feature myself, though, or seen it in use. So I > don't know if this is purely a theoretical concern, or if the > stable_address feature is actually used in this way in practice. If it > is, I guess the switch would have to be opt-in, which kinda defeats the > purpose, no (i.e., we'd have to keep the SHA1 code around I'm not even so sure that's true. That was my worry at first, but actually, looking at this more closely, DAD means that the address can be changed anyway - a byte counter is hashed in - so there's no gurantee there. There's also the other aspect that open coding sha1_transform like this and prepending it with the secret (rather than a better construction) isn't so great... Take a look at the latest version of this in my branch to see a really nice simplification and security improvement: https://git.zx2c4.com/linux-dev/log/?h=remove-sha1 Jason
