linux.git/security/integrity/evm, branch v6.12.80

evm: Use ordered xattrs list to calculate HMAC in evm_init_hmac()

2026-03-04T12:19:56+00:00

[ Upstream commit 0496fc9cdc384f67be4413b1c6156eb64fccd5c4 ]

Commit 8e5d9f916a96 ("smack: deduplicate xattr setting in
smack_inode_init_security()") introduced xattr_dupval() to simplify setting
the xattrs to be provided by the SMACK LSM on inode creation, in the
smack_inode_init_security().

Unfortunately, moving lsm_get_xattr_slot() caused the SMACK64TRANSMUTE
xattr be added in the array of new xattrs before SMACK64. This causes the
HMAC of xattrs calculated by evm_init_hmac() for new files to diverge from
the one calculated by both evm_calc_hmac_or_hash() and evmctl.

evm_init_hmac() calculates the HMAC of the xattrs of new files based on the
order LSMs provide them, while evm_calc_hmac_or_hash() and evmctl calculate
the HMAC based on an ordered xattrs list.

Fix the issue by making evm_init_hmac() calculate the HMAC of new files
based on the ordered xattrs list too.

Fixes: 8e5d9f916a96 ("smack: deduplicate xattr setting in smack_inode_init_security()")
Signed-off-by: Roberto Sassu 
Signed-off-by: Mimi Zohar 
Signed-off-by: Sasha Levin

evm: stop avoidably reading i_writecount in evm_file_release

2024-10-10T02:49:40+00:00

The EVM_NEW_FILE flag is unset if the file already existed at the time
of open and this can be checked without looking at i_writecount.

Not accessing it reduces traffic on the cacheline during parallel open
of the same file and drop the evm_file_release routine from second place
to bottom of the profile.

Fixes: 75a323e604fc ("evm: Make it independent from 'integrity' LSM")
Signed-off-by: Mateusz Guzik 
Reviewed-by: Roberto Sassu 
Cc: stable@vger.kernel.org # 6.9+
Signed-off-by: Mimi Zohar

lsm: Refactor return value of LSM hook inode_copy_up_xattr

2024-07-31T18:47:09+00:00

To be consistent with most LSM hooks, convert the return value of
hook inode_copy_up_xattr to 0 or a negative error code.

Before:
- Hook inode_copy_up_xattr returns 0 when accepting xattr, 1 when
  discarding xattr, -EOPNOTSUPP if it does not know xattr, or any
  other negative error code otherwise.

After:
- Hook inode_copy_up_xattr returns 0 when accepting xattr, *-ECANCELED*
  when discarding xattr, -EOPNOTSUPP if it does not know xattr, or
  any other negative error code otherwise.

Signed-off-by: Xu Kuohai 
Reviewed-by: Casey Schaufler 
Signed-off-by: Paul Moore

evm: Rename is_unsupported_fs to is_unsupported_hmac_fs

2024-04-09T21:14:58+00:00

Rename is_unsupported_fs to is_unsupported_hmac_fs since now only HMAC is
unsupported.

Co-developed-by: Mimi Zohar 
Signed-off-by: Stefan Berger 
Signed-off-by: Mimi Zohar

fs: Rename SB_I_EVM_UNSUPPORTED to SB_I_EVM_HMAC_UNSUPPORTED

2024-04-09T21:14:58+00:00

Now that EVM supports RSA signatures for previously completely
unsupported filesystems rename the flag SB_I_EVM_UNSUPPORTED to
SB_I_EVM_HMAC_UNSUPPORTED to reflect that only HMAC is not supported.

Suggested-by: Amir Goldstein 
Suggested-by: Mimi Zohar 
Signed-off-by: Stefan Berger 
Acked-by: Amir Goldstein 
Signed-off-by: Mimi Zohar

evm: Enforce signatures on unsupported filesystem for EVM_INIT_X509

2024-04-09T21:14:57+00:00

Unsupported filesystems currently do not enforce any signatures. Add
support for signature enforcement of the "original" and "portable &
immutable" signatures when EVM_INIT_X509 is enabled.

The "original" signature type contains filesystem specific metadata.
Thus it cannot be copied up and verified. However with EVM_INIT_X509
and EVM_ALLOW_METADATA_WRITES enabled, the "original" file signature
may be written.

When EVM_ALLOW_METADATA_WRITES is not set or once it is removed from
/sys/kernel/security/evm by setting EVM_INIT_HMAC for example, it is not
possible to write or remove xattrs on the overlay filesystem.

This change still prevents EVM from writing HMAC signatures on
unsupported filesystem when EVM_INIT_HMAC is enabled.

Co-developed-by: Mimi Zohar 
Signed-off-by: Stefan Berger 
Signed-off-by: Mimi Zohar

evm: Store and detect metadata inode attributes changes

2024-04-09T21:14:57+00:00

On stacked filesystem the metadata inode may be different than the one
file data inode and therefore changes to it need to be detected
independently. Therefore, store the i_version, device number, and inode
number associated with the file metadata inode.

Implement a function to detect changes to the inode and if a change is
detected reset the evm_status. This function will be called by IMA when
IMA detects that the metadata inode is different from the file's inode.

Co-developed-by: Mimi Zohar 
Signed-off-by: Stefan Berger 
Signed-off-by: Mimi Zohar

evm: Use the metadata inode to calculate metadata hash

2024-04-09T21:14:57+00:00

Changes to file attributes (mode bits, uid, gid) on the lower layer are
not taken into account when d_backing_inode() is used when a file is
accessed on the overlay layer and this file has not yet been copied up.
This is because d_backing_inode() does not return the real inode of the
lower layer but instead returns the backing inode which in this case
holds wrong file attributes. Further, when CONFIG_OVERLAY_FS_METACOPY is
enabled and a copy-up is triggered due to file metadata changes, then
the metadata are held by the backing inode while the data are still held
by the real inode. Therefore, use d_inode(d_real(dentry, D_REAL_METADATA))
to get to the file's metadata inode and use it to calculate the metadata
hash with.

Co-developed-by: Mimi Zohar 
Signed-off-by: Stefan Berger 
Acked-by: Amir Goldstein 
Signed-off-by: Mimi Zohar

evm: Implement per signature type decision in security_inode_copy_up_xattr

2024-04-09T21:14:57+00:00

To support "portable and immutable signatures" on otherwise unsupported
filesystems, determine the EVM signature type by the content of a file's
xattr. If the file has the appropriate signature type then allow it to be
copied up. All other signature types are discarded as before.

"Portable and immutable" EVM signatures can be copied up by stacked file-
system since the metadata their signature covers does not include file-
system-specific data such as a file's inode number, generation, and UUID.

Co-developed-by: Mimi Zohar 
Signed-off-by: Stefan Berger 
Signed-off-by: Mimi Zohar

security: allow finer granularity in permitting copy-up of security xattrs

2024-04-09T21:14:57+00:00

Copying up xattrs is solely based on the security xattr name. For finer
granularity add a dentry parameter to the security_inode_copy_up_xattr
hook definition, allowing decisions to be based on the xattr content as
well.

Co-developed-by: Mimi Zohar 
Signed-off-by: Stefan Berger 
Acked-by: Amir Goldstein 
Acked-by: Paul Moore  (LSM,SELinux)
Signed-off-by: Mimi Zohar