linux-toradex.git/include/linux/evm.h, branch v6.13-rc6

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: Make it independent from 'integrity' LSM

2024-02-16T04:43:47+00:00

Define a new structure for EVM-specific metadata, called evm_iint_cache,
and embed it in the inode security blob. Introduce evm_iint_inode() to
retrieve metadata, and register evm_inode_alloc_security() for the
inode_alloc_security LSM hook, to initialize the structure (before
splitting metadata, this task was done by iint_init_always()).

Keep the non-NULL checks after calling evm_iint_inode() except in
evm_inode_alloc_security(), to take into account inodes for which
security_inode_alloc() was not called. When using shared metadata,
obtaining a NULL pointer from integrity_iint_find() meant that the file
wasn't in the IMA policy. Now, because IMA and EVM use disjoint metadata,
the EVM status has to be stored for every inode regardless of the IMA
policy.

Given that from now on EVM relies on its own metadata, remove the iint
parameter from evm_verifyxattr(). Also, directly retrieve the iint in
evm_verify_hmac(), called by both evm_verifyxattr() and
evm_verify_current_integrity(), since now there is no performance penalty
in retrieving EVM metadata (constant time).

Replicate the management of the IMA_NEW_FILE flag, by introducing
evm_post_path_mknod() and evm_file_release() to respectively set and clear
the newly introduced flag EVM_NEW_FILE, at the same time IMA does. Like for
IMA, select CONFIG_SECURITY_PATH when EVM is enabled, to ensure that files
are marked as new.

Unlike ima_post_path_mknod(), evm_post_path_mknod() cannot check if a file
must be appraised. Thus, it marks all affected files. Also, it does not
clear EVM_NEW_FILE depending on i_version, but that is not a problem
because IMA_NEW_FILE is always cleared when set in ima_check_last_writer().

Move the EVM-specific flag EVM_IMMUTABLE_DIGSIG to
security/integrity/evm/evm.h, since that definition is now unnecessary in
the common integrity layer.

Finally, switch to the LSM reservation mechanism for the EVM xattr, and
consequently decrement by one the number of xattrs to allocate in
security_inode_init_security().

Signed-off-by: Roberto Sassu 
Reviewed-by: Casey Schaufler 
Reviewed-by: Stefan Berger 
Reviewed-by: Mimi Zohar 
Acked-by: Mimi Zohar 
Signed-off-by: Paul Moore

evm: Move to LSM infrastructure

2024-02-16T04:43:47+00:00

As for IMA, move hardcoded EVM function calls from various places in the
kernel to the LSM infrastructure, by introducing a new LSM named 'evm'
(last and always enabled like 'ima'). The order in the Makefile ensures
that 'evm' hooks are executed after 'ima' ones.

Make EVM functions as static (except for evm_inode_init_security(), which
is exported), and register them as hook implementations in init_evm_lsm().
Also move the inline functions evm_inode_remove_acl(),
evm_inode_post_remove_acl(), and evm_inode_post_set_acl() from the public
evm.h header to evm_main.c.

Unlike before (see commit to move IMA to the LSM infrastructure),
evm_inode_post_setattr(), evm_inode_post_set_acl(),
evm_inode_post_remove_acl(), and evm_inode_post_removexattr() are not
executed for private inodes.

Finally, add the LSM_ID_EVM case in lsm_list_modules_test.c

Signed-off-by: Roberto Sassu 
Reviewed-by: Casey Schaufler 
Acked-by: Christian Brauner 
Reviewed-by: Stefan Berger 
Reviewed-by: Mimi Zohar 
Acked-by: Mimi Zohar 
Signed-off-by: Paul Moore

evm: Align evm_inode_post_setxattr() definition with LSM infrastructure

2024-02-16T04:43:41+00:00

Change evm_inode_post_setxattr() definition, so that it can be registered
as implementation of the inode_post_setxattr hook.

Signed-off-by: Roberto Sassu 
Reviewed-by: Stefan Berger 
Reviewed-by: Mimi Zohar 
Reviewed-by: Casey Schaufler 
Acked-by: Mimi Zohar 
Signed-off-by: Paul Moore

evm: Align evm_inode_setxattr() definition with LSM infrastructure

2024-02-16T04:43:40+00:00

Change evm_inode_setxattr() definition, so that it can be registered as
implementation of the inode_setxattr hook.

Signed-off-by: Roberto Sassu 
Reviewed-by: Stefan Berger 
Reviewed-by: Mimi Zohar 
Reviewed-by: Casey Schaufler 
Acked-by: Mimi Zohar 
Signed-off-by: Paul Moore

evm: Align evm_inode_post_setattr() definition with LSM infrastructure

2024-02-16T04:43:40+00:00

Change evm_inode_post_setattr() definition, so that it can be registered as
implementation of the inode_post_setattr hook (to be introduced).

Signed-off-by: Roberto Sassu 
Reviewed-by: Stefan Berger 
Reviewed-by: Casey Schaufler 
Reviewed-by: Mimi Zohar 
Acked-by: Mimi Zohar 
Signed-off-by: Paul Moore

evm: don't copy up 'security.evm' xattr

2023-12-20T12:39:52+00:00

The security.evm HMAC and the original file signatures contain
filesystem specific data.  As a result, the HMAC and signature
are not the same on the stacked and backing filesystems.

Don't copy up 'security.evm'.

Reviewed-by: Amir Goldstein 
Reviewed-by: Christian Brauner 
Signed-off-by: Mimi Zohar

evm: Align evm_inode_init_security() definition with LSM infrastructure

2023-07-10T17:59:38+00:00

Change the evm_inode_init_security() definition to align with the LSM
infrastructure. Keep the existing behavior of including in the HMAC
calculation only the first xattr provided by LSMs.

Changing the evm_inode_init_security() definition requires passing the
xattr array allocated by security_inode_init_security(), and the number of
xattrs filled by previously invoked LSMs.

Use the newly introduced lsm_get_xattr_slot() to position EVM correctly in
the xattrs array, like a regular LSM, and to increment the number of filled
slots. For now, the LSM infrastructure allocates enough xattrs slots to
store the EVM xattr, without using the reservation mechanism.

Signed-off-by: Roberto Sassu 
Reviewed-by: Mimi Zohar 
Acked-by: Mimi Zohar 
Signed-off-by: Paul Moore

fs: port acl to mnt_idmap

2023-01-19T08:24:28+00:00

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Christian Brauner (Microsoft)

fs: port xattr to mnt_idmap

2023-01-19T08:24:28+00:00

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Christian Brauner (Microsoft)