Re: Problem mounting pseudo filesystems with SMACK and IMA enabled.

[Mimi Zohar <zohar@linux.vnet.ibm.com>]

On Fri, 2018-03-16 at 14:34 +0000, Martin Townsend wrote:
> Hi Mimi,
> 
> On Fri, Mar 16, 2018 at 1:25 PM, Mimi Zohar <zohar@linux.vnet.ibm.com> wrote:
> > On Fri, 2018-03-16 at 09:32 +0000, Martin Townsend wrote:
> >> [Resending to new integrity mailing list]
> >>
> >> Hi,
> >>
> >> I have a system with a pre-signed UBI root filesystem image with both
> >> IMA/EVM signatures on all files.  The Root CA Cert is compiled into
> >> the kernel and the public keys is in the rootfs.  All SMACK labels
> >> have also been applied although at this early stage there aren't many
> >> (just a few application specific ones) so it's mainly the defaults.
> >> This image is then flashed to the on board NAND.
> >>
> >> The kernel bootargs for IMA are
> >>
> >> "ima_audit=1 ima_template=ima-ng ima_hash=sha1 ima_tcb
> >> ima_appraise_tcb rootflags=i_version"
> >>
> >> and I'm enabling SMACK by using the kernel bootarg
> >>
> >> "security=smack"
> >>
> >> now if I boot without the "security=smack" it boots fine and I can
> >> check the IMA/EVM signatures and can see that measurements are being
> >> taken, but if I enable SMACK using the above kernel bootarg it fails
> >> to boot and it looks like some problem early in systemd where it
> >> mounts the required filesystems in mount-setup.c (log provided below).
> >> Now if I flash an image that hasn't been signed and enable SMACK it
> >> boots fine and I can use SMACK to enforce access control.  So there
> >> seems to some interaction between the two when mounting the early
> >> filesystems.
> >>
> >> Before I delve into this I would appreciate any pointers to where to
> >> start looking, any printk's to put in SMACK/IMA/mount code to help
> >> diagnose this would be really appreciated.
> >>
> >> The Kernel is 4.9 LTSI, systemd is v229
> >>
> >> Apologies if I have the wrong mailing list for SMACK, I couldn't find
> >> one on vger.kernel.org.
> >>
> >>
> >> Boot log.
> >> ...
> >> Security Framework initialized
> >> Smack:  Initializing.
> >> Smack:  IPv6 port labeling enabled.
> >> Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
> >> Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
> >> CPU: Testing write buffer coherency: ok
> >> Setting up static identity map for 0x80100000 - 0x80100058
> >> devtmpfs: initialized
> >> evm: security.SMACK64
> >> evm: security.SMACK64EXEC
> >> evm: security.SMACK64TRANSMUTE
> >> evm: security.SMACK64MMAP
> >> evm: security.ima
> >> evm: security.capability
> >> ...
> >> Loading compiled-in X.509 certificates
> >> Loaded X.509 cert 'IMA-EVM Root CA: cc972d25acf7c1efaa5329a48104efa303f0833a'
> >> ...
> >> UBIFS (ubi0:0): FS size: 201764864 bytes (192 MiB, 1589 LEBs), journal
> >> size 9023488 bytes (8 MiB, 72 LEBs)
> >> UBIFS (ubi0:0): reserved for root: 0 bytes (0 KiB)
> >> UBIFS (ubi0:0): media format: w4/r0 (latest is w4/r0), UUID
> >> F6EA70A5-1931-4049-89CB-93B82F37F6A4, small LPT model
> >> VFS: Mounted root (ubifs filesystem) readonly on device 0:16.
> >> devtmpfs: mounted
> >> integrity: Loaded X.509 cert 'IMA Certificate Authority:
> >> e2c191a6e31fd02d6beba0c7c7847720a35fd9c6': /etc/keys/ima-x509.der
> >> Freeing unused kernel memory: 1024K
> >> systemd[1]: Successfully loaded Smack policies.
> >> systemd[1]: Successfully loaded Smack/CIPSO policies.
> >> systemd[1]: System time before build time, advancing clock.
> >> systemd[1]: Failed to mount tmpfs at /dev/shm: No such file or directory
> >> systemd[1]: Failed to mount tmpfs at /dev/shm: No such file or directory
> >> systemd[1]: Failed to mount cgroup at /sys/fs/cgroup/systemd: No such
> >> file or directory
> >> [!!!!!!] Failed to mount API filesystems, freezing.
> >> systemd[1]: Freezing execution.
> >
> > [Cc'ing Sascha]
> >
> > Are there any additional messages in /var/log/audit/audit.log?
> >
> > Mimi
> >
> 
> Sadly I can't see this file, I don't even think the relevant
> filesystems have been mounted as this point. I tried the emergency
> shell but no joy. Is there a way of patching the kernel to show audit
> messages to the console?  If you point me at the relevant code I'll
> hack something in.  I'm currently putting printk's everywhere I can
> think of to see what's going on.   If you can think of anywhere in the
> IMA that would be good to see a debug print let me know, currently I
> have something in process_measurements and a few other places in
> ima_main.c.

I would think the audit messages would go to the console.  With
dracut, I use a couple of boot command line options for debugging (eg.
rd.debug rd.break=pre-mount, rd.shell).

Mimi