On Sat, 2021-01-30 at 19:53 +0200, Jarkko Sakkinen wrote:

On Thu, 2021-01-28 at 18:31 +0100, Ahmad Fatoum wrote:

quoted

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.

We upstreamed "trusted" & "encrypted" keys together in order to address
this sort of problem.   Instead of directly using a "trusted" key for
persistent file signatures being stored as xattrs, the "encrypted" key
provides one level of indirection.   The "encrypted" key may be
encrypted/decrypted with either a TPM based "trusted" key or with a
"user" type symmetric key[1].

Instead of modifying "trusted" keys, use a "user" type "encrypted" key.

Mimi

[1] The ima-evm-utils README contains EVM examples of "trusted" and
"user" based "encrypted" keys.