On Mon, Aug 23, 2021 at 6:29 AM Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> wrote: > > Hello Tim, > > On 20.08.21 23:19, Tim Harvey wrote: > > On Fri, Aug 20, 2021 at 1:36 PM Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> wrote: > >> > >> On 20.08.21 22:20, Tim Harvey wrote: > >>> On Fri, Aug 20, 2021 at 9:20 AM Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> wrote: > >>>> On 20.08.21 17:39, Tim Harvey wrote: > >>>>> Thanks for your work! > >>>>> > >>>>> I've been asked to integrate the capability of using CAAM to > >>>>> blob/deblob data to an older 5.4 kernel such as NXP's downstream > >>>>> vendor kernel does [1] and I'm trying to understand how your series > >>>>> works. I'm not at all familiar with the Linux Key Management API's or > >>>>> trusted keys. Can you provide an example of how this can be used for > >>>>> such a thing? > >>>> > >>>> Here's an example with dm-crypt: > >>>> > >>>> https://lore.kernel.org/linux-integrity/5d44e50e-4309-830b-79f6-f5d888b1ef69@xxxxxxxxxxxxxx/ > >>>> > >>>> dm-crypt is a bit special at the moment, because it has direct support for > >>>> trusted keys. For interfacing with other parts of the kernel like ecryptfs > >>>> or EVM, you have to create encrypted keys rooted to the trusted keys and use > >>>> those. The kernel documentation has an example: > >>>> > >>>> https://www.kernel.org/doc/html/v5.13/security/keys/trusted-encrypted.html > >>>> > >>>> If you backport this series, you can include the typo fix spotted by David. > >>>> > >>>> I'll send out a revised series, but given that a regression fix I want to > >>>> rebase on hasn't been picked up for 3 weeks now, I am not in a hurry. > >>>> > >>> Thanks for the reference. > >>> > >>> I'm still trying to understand the keyctl integration with caam. For > >>> the 'data' param to keyctl you are using tings like 'new <len>' and > >>> 'load <data>'. Where are these 'commands' identified? > >> > >> Search for match_table_t in security/keys/trusted-keys/trusted_core.c > >> > >>> I may still be missing something. I'm using 4.14-rc6 with your series > >>> and seeing the following: > >> > >> That's an odd version to backport stuff to.. > >> > >>> # cat /proc/cmdline > >>> trusted.source=caam > >>> # keyctl add trusted mykey 'new 32' @s)# create new trusted key named > >>> 'mykey' of 32 bytes in the session keyring > >>> 480104283 > >>> # keyctl print 480104283 # dump the key > >>> keyctl_read_alloc: Unknown error 126 > >>> ^^^ not clear what this is > >> > >> Not sure what returns -ENOKEY for you. I haven't been using trusted > >> keys on v4.14, but you can try tracing the keyctl syscall. > > > > yikes... that would be painful. I typo'd and meant 5.14-rc6 :) > > ^^ > > > I'm working with mainline first to make sure I understand everything. If I > > backport this it would be to 5.4 but that looks to be extremely > > painful. It looks like there was a lot of activity around trusted keys > > in 5.13. > > Ye. It used to be limited to TPM before that. > > > It works for a user keyring but not a session keyring... does that > > explain anything? > > # keyctl add trusted mykey 'new 32' @u > > 941210782 > > # keyctl print 941210782 > > 83b7845cb45216496aead9ee2c6a406f587d64aad47bddc539d8947a247e618798d9306b36398b5dc2722a4c3f220a3a763ee175f6bd64758fdd49ca4db597e8ce328121b60edbba9b8d8d55056be896 > > # keyctl add trusted mykey 'new 32' @s > > 310571960 > > # keyctl print 310571960 > > keyctl_read_alloc: Unknown error 126 > > Both sequences work for me. > > My getty is started by systemd. I think systemd allocates a new session > keyring for the getty that's inherited by the shell and the commands I run > it in. If you don't do that, each command will get its own session key. > > > Sorry, I'm still trying to wrap my head around the differences in > > keyrings and trusted vs user keys. > > No problem. HTH. Ahmad, Ok that explains it - my testing is using a very basic buildroot ramdisk rootfs. If I do a 'keyctl new_session' first I can use the system keyring fine as well. Thanks - hoping to see this merged soon! Tim
