[PATCH v3 00/25] security: Move IMA and EVM to the LSM infrastructure

Roberto Sassu
2023-09-04T13:35:11Z

From: Roberto Sassu <roberto.sassu@huawei.com>

IMA and EVM are not effectively LSMs, especially due the fact that in the
past they could not provide a security blob while there is another LSM
active.

That changed in the recent years, the LSM stacking feature now makes it
possible to stack together multiple LSMs, and allows them to provide a
security blob for most kernel objects. While the LSM stacking feature has
some limitations being worked out, it is already suitable to make IMA and
EVM as LSMs.

In short, while this patch set is big, it does not make any functional
change to IMA and EVM. IMA and EVM functions are called by the LSM
infrastructure in the same places as before (except ima_post_path_mknod()),
rather being hardcoded calls, and the inode metadata pointer is directly
stored in the inode security blob rather than in a separate rbtree.

More specifically, patches 1-11 make IMA and EVM functions suitable to
be registered to the LSM infrastructure, by aligning function parameters.

Patches 12-20 add new LSM hooks in the same places where IMA and EVM
functions are called, if there is no LSM hook already.

Patches 21-24 do the bulk of the work, remove hardcoded calls to IMA, EVM
and integrity functions, register those functions in the LSM
infrastructure, and let the latter call them. In addition, they also
reserve one slot for EVM to supply an xattr with the inode_init_security
hook.

Finally, patch 25 removes the rbtree used to bind metadata to the inodes,
and instead reserves a space in the inode security blob to store the
pointer to metadata. This also brings performance improvements due to
retrieving metadata in constant time, as opposed to logarithmic.

The patch set applies on top of lsm/next, commit 8e4672d6f902 ("lsm:
constify the 'file' parameter in security_binder_transfer_file()")

Changelog:

v2:
- Add description for newly introduced LSM hooks (suggested by Casey)
- Clarify in the description of security_file_pre_free() that actions can
be performed while the file is still open

v1:
- Drop 'evm: Complete description of evm_inode_setattr()', 'fs: Fix
description of vfs_tmpfile()' and 'security: Introduce LSM_ORDER_LAST',
they were sent separately (suggested by Christian Brauner)
- Replace dentry with file descriptor parameter for
security_inode_post_create_tmpfile()
- Introduce mode_stripped and pass it as mode argument to
security_path_mknod() and security_path_post_mknod()
- Use goto in do_mknodat() and __vfs_removexattr_locked() (suggested by
Mimi)
- Replace __lsm_ro_after_init with __ro_after_init
- Modify short description of security_inode_post_create_tmpfile() and
security_inode_post_set_acl() (suggested by Stefan)
- Move security_inode_post_setattr() just after security_inode_setattr()
(suggested by Mimi)
- Modify short description of security_key_post_create_or_update()
(suggested by Mimi)
- Add back exported functions ima_file_check() and
evm_inode_init_security() respectively to ima.h and evm.h (reported by
kernel robot)
- Remove extern from prototype declarations and fix style issues
- Remove unnecessary include of linux/lsm_hooks.h in ima_main.c and
ima_appraise.c

Roberto Sassu (25):
ima: Align ima_inode_post_setattr() definition with LSM infrastructure
ima: Align ima_post_path_mknod() definition with LSM infrastructure
ima: Align ima_post_create_tmpfile() definition with LSM
infrastructure
ima: Align ima_file_mprotect() definition with LSM infrastructure
ima: Align ima_inode_setxattr() definition with LSM infrastructure
ima: Align ima_inode_removexattr() definition with LSM infrastructure
ima: Align ima_post_read_file() definition with LSM infrastructure
evm: Align evm_inode_post_setattr() definition with LSM infrastructure
evm: Align evm_inode_setxattr() definition with LSM infrastructure
evm: Align evm_inode_post_setxattr() definition with LSM
infrastructure
security: Align inode_setattr hook definition with EVM
security: Introduce inode_post_setattr hook
security: Introduce inode_post_removexattr hook
security: Introduce file_post_open hook
security: Introduce file_pre_free_security hook
security: Introduce path_post_mknod hook
security: Introduce inode_post_create_tmpfile hook
security: Introduce inode_post_set_acl hook
security: Introduce inode_post_remove_acl hook
security: Introduce key_post_create_or_update hook
ima: Move to LSM infrastructure
ima: Move IMA-Appraisal to LSM infrastructure
evm: Move to LSM infrastructure
integrity: Move integrity functions to the LSM infrastructure
integrity: Switch from rbtree to LSM-managed blob for
integrity_iint_cache

fs/attr.c | 5 +-
fs/file_table.c | 3 +-
fs/namei.c | 18 +-
fs/nfsd/vfs.c | 3 +-
fs/open.c | 1 -
fs/posix_acl.c | 5 +-
fs/xattr.c | 9 +-
include/linux/evm.h | 103 ----------
include/linux/ima.h | 136 -------------
include/linux/integrity.h | 26 ---
include/linux/lsm_hook_defs.h | 21 +-
include/linux/security.h | 65 +++++++
security/integrity/evm/evm_main.c | 104 ++++++++--
security/integrity/iint.c | 92 +++------
security/integrity/ima/ima.h | 11 ++
security/integrity/ima/ima_appraise.c | 37 +++-
security/integrity/ima/ima_main.c | 76 ++++++--
security/integrity/integrity.h | 44 ++++-
security/keys/key.c | 10 +-
security/security.c | 265 ++++++++++++++++----------
security/selinux/hooks.c | 3 +-
security/smack/smack_lsm.c | 4 +-
22 files changed, 540 insertions(+), 501 deletions(-)

--
2.34.1