On Mon, Aug 06, 2018 at 05:48:04PM +0800, joeyli wrote: > On Mon, Aug 06, 2018 at 03:57:54PM +0800, Yu Chen wrote: > > Hi Oliver, > > On Thu, Jul 26, 2018 at 09:30:46AM +0200, Oliver Neukum wrote: > > > On Di, 2018-07-24 at 00:23 +0800, Yu Chen wrote: > > > > > > > > Good point, we once tried to generate key in kernel, but people > > > > suggest to generate key in userspace and provide it to the > > > > kernel, which is what ecryptfs do currently, so it seems this > > > > should also be safe for encryption in kernel. > > > > https://www.spinics.net/lists/linux-crypto/msg33145.html > > > > Thus Chun-Yi's signature can use EFI key and both the key from > > > > user space. > > As Ard and James's comments, the EFI key can not be accepted: > https://lkml.org/lkml/2018/8/5/135 > > The lower entropy problem can be covered by RDRAND or EFI random > protocol. But the key point is that we can not fully trust manufacturer. > And, the secure boot relies on Microsoft's business interests. It's > not designed for confidentiality. > > So I will move to TPM trusted key + encrypted key. > OK. > > > > > > Hi, > > > > > > ecryptfs can trust user space. It is supposed to keep data > > > safe while the system is inoperative. > > Humm, I did not quite get the point here, let's take fscrypt > > for example, the kernel gets user generated key from user space, > > and uses per-inode nonce(random bytes) as the master key to > > do a KDF(key derivation function) on user provided key, and uses > > that key for encryption. We can also added similar mechanism > > to generate the key in kernel space but the key should be > > original from user's provided key(password derived), because > > the security boot/signature mechanism could not cover the case > > that, two different users could resume to each other's context > > because there isn't any certification during resume if it is > > on the same physical hardware. > > > > Sounds there have two different purposes. One is to prevent that > the secret in snapshop image be detected/changed outside the machine. > Another one try to prevent that B user resumes to A user's context > on the same machine. > Yes, it aims to prevent B from resuming to A's context no matter whether it is on the same hardware or not, and prevents others from getting the plain content on the disk. > In the case of B resumes A's context, I still think that the attacker > must physical accesses the machine. Which means that it's out of EFI > secure boot's design. Could you please explan the detail for the attack? > May I know what attack does it refer to? please refer to another mail I sent to Pavel, a simple use case has been described. > So I think that the password from user space is for user authentication, > and the TPM trusted key is for snapshot image encryption/verification. > password generated key could also be used as encryption. Best, Yu > Thanks > Joey Lee
