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. Cheers, Ahmad > > Tim > -- 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 |
