On Tue, 2021-02-02 at 17:45 +0530, Sumit Garg wrote: > Hi Jan, > > On Sun, 31 Jan 2021 at 23:40, James Bottomley <jejb@xxxxxxxxxxxxx> wrote: > > > > On Sun, 2021-01-31 at 15:14 +0100, Jan Lübbe wrote: > > > On Sun, 2021-01-31 at 07:09 -0500, Mimi Zohar wrote: > > > > On Sat, 2021-01-30 at 19:53 +0200, Jarkko Sakkinen wrote: > > > > > On Thu, 2021-01-28 at 18:31 +0100, Ahmad Fatoum wrote: > > > > > > Hello, > > > > > > > > > > > > I've been looking into how a migration to using > > > > > > trusted/encrypted keys would look like (particularly with dm- > > > > > > crypt). > > > > > > > > > > > > Currently, it seems the the only way is to re-encrypt the > > > > > > partitions because trusted/encrypted keys always generate their > > > > > > payloads from RNG. > > > > > > > > > > > > If instead there was a key command to initialize a new > > > > > > trusted/encrypted key with a user provided value, users could > > > > > > use whatever mechanism they used beforehand to get a plaintext > > > > > > key and use that to initialize a new trusted/encrypted key. > > > > > > From there on, the key will be like any other trusted/encrypted > > > > > > key and not be disclosed again to userspace. > > > > > > > > > > > > What are your thoughts on this? Would an API like > > > > > > > > > > > > keyctl add trusted dmcrypt-key 'set <content>' # user- > > > > > > supplied content > > > > > > > > > > > > be acceptable? > > > > > > > > > > Maybe it's the lack of knowledge with dm-crypt, but why this > > > > > would be useful? Just want to understand the bottleneck, that's > > > > > all. > > > > > > Our goal in this case is to move away from having the dm-crypt key > > > material accessible to user-space on embedded devices. For an > > > existing dm-crypt volume, this key is fixed. A key can be loaded into > > > user key type and used by dm-crypt (cryptsetup can already do it this > > > way). But at this point, you can still do 'keyctl read' on that key, > > > exposing the key material to user space. > > > > > > Currently, with both encrypted and trusted keys, you can only > > > generate new random keys, not import existing key material. > > > > > > James Bottomley mentioned in the other reply that the key format will > > > become compatible with the openssl_tpm2_engine, which would provide a > > > workaround. This wouldn't work with OP-TEE-based trusted keys (see > > > Sumit Garg's series), though. > > > > Assuming OP-TEE has the same use model as the TPM, someone will > > eventually realise the need for interoperable key formats between key > > consumers and then it will work in the same way once the kernel gets > > updated to speak whatever format they come up with. > > IIUC, James re-work for TPM trusted keys is to allow loading of sealed > trusted keys directly via user-space (with proper authorization) into > the kernel keyring. > > I think similar should be achievable with OP-TEE (via extending pseudo > TA [1]) as well to allow restricted user-space access (with proper > authorization) to generate sealed trusted key blob that should be > interoperable with the kernel. Currently OP-TEE exposes trusted key > interfaces for kernel users only. What is the security benefit of having the key blob creation in user-space instead of in the kernel? Key import is a standard operation in HSMs or PKCS#11 tokens. I mainly see the downside of having to add another API to access the underlying functionality (be it trusted key TA or the NXP CAAM HW *) and requiring platform-specific userspace code. This CAAM specific API (in out-of-tree patches) was exactly the part I was trying to get rid of. ;) Regards, Jan -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
