Re: [PATCH v8 23/24] ima: Make it independent from 'integrity' LSM

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On 12/27/2023 8:21 PM, Mimi Zohar wrote:
On Wed, 2023-12-27 at 17:39 +0100, Roberto Sassu wrote:
On 12/27/2023 2:22 PM, Mimi Zohar wrote:
On Thu, 2023-12-14 at 18:08 +0100, Roberto Sassu wrote:
From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>

Make the 'ima' LSM independent from the 'integrity' LSM by introducing IMA
own integrity metadata (ima_iint_cache structure, with IMA-specific fields
from the integrity_iint_cache structure), and by managing it directly from
the 'ima' LSM.

Move the remaining IMA-specific flags to security/integrity/ima/ima.h,
since they are now unnecessary in the common integrity layer.

Replace integrity_iint_cache with ima_iint_cache in various places
of the IMA code.

Then, reserve space in the security blob for the entire ima_iint_cache
structure, so that it is available for all inodes having the security blob
allocated (those for which security_inode_alloc() was called).  Adjust the
IMA code accordingly, call ima_iint_inode() to retrieve the ima_iint_cache
structure. Keep the non-NULL checks since there can be inodes without
security blob.

Previously the 'iint' memory was only allocated for regular files in
policy and were tagged S_IMA.  This patch totally changes when and how
memory is being allocated.  Does it make sense to allocate memory at
security_inode_alloc()?  Is this change really necessary for making IMA
a full fledged LSM?

Good question. I think it wouldn't be necessary, we can reuse the same
approach as in the patch 'integrity: Switch from rbtree to LSM-managed
blob for integrity_iint_cache'.

Going forward with the v8 proposed solution would require some real
memory usage analysis for different types of policies.

To me the "integrity: Switch from rbtree to LSM-managed blob for
integrity_iint_cache" makes a lot more sense.   Looking back at the
original thread, your reasons back then for not directly allocating the
integrity_iint_cache are still valid for the ima_iint_cache structure.

Uhm, ok. It should not be too difficult to restore the old mechanism for ima_iint_cache. Will do it in v9.

Thanks

Roberto

Mimi



Don't include the inode pointer as field in the ima_iint_cache structure,
since the association with the inode is clear. Since the inode field is
missing in ima_iint_cache, pass the extra inode parameter to
ima_get_verity_digest().

Finally, register ima_inode_alloc_security/ima_inode_free_security() to
initialize/deinitialize the new ima_iint_cache structure (before this task
was done by iint_init_always() and iint_free()). Also, duplicate
iint_lockdep_annotate() for the ima_iint_cache structure, and name it
ima_iint_lockdep_annotate().

Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>







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