[v3,00/13] LSM: Move away from secids

Message

Casey Schaufler Sept. 10, 2024, 6:41 p.m. UTC

Many of the Linux Security Module (LSM) interfaces use u32
security ID values (secids) to identify module specific security
attributes. This is an artifact of the SELinux security server
architecture and compromises made to allow security attributes
to be associated with networking mechanisms. There are significant
performance implications to using this approach, as access control
decisions must map the secids to the real data to be used. There is
also impact on the audit system, which must provide textual values
for security attributes.

The secid based interfaces are also constrained to supporting a
single security module. There are clever mechanisms for representing
multiple 32 bit values in a single 32 bit value, but they add overhead
and complexity. While the issue of multiple concurrent security modules
is not explicity addressed here, the move away from secids is required
to make that possible.

Most uses of secids can be replaced by a security module specific
value. In SELinux this remains a u32 secid. In Smack the value is
a pointer into the system label list. In AppArmor a pointer to a
security context can be used. Because the active security module can
be specified at boot time using the "security=" or "lsm=" flags,
the system must be able to use any of the possible values.

A struct lsm_prop is introduced to contain the attribute values.
This struct includes a member for each of the security modules that
are built into the kernel. Where possible, uses of secids are
replaced with a lsm_prop. LSM interfaces have been modified to use
lsm_prop pointers instead of secids in most cases. Some new interfaces
have been introduced where it is not practical to replace an existing
secid interface. This occurs in several networking code paths.

https://github.com/cschaufler/lsm-stacking.git#lsmprop-6.11-rc3-v3

Revisons:

v3: Feedback on v2 - Top Shelf (TM) Bikeshedding
    - Change structure name from lsmblob to lsm_prop
    - Fix return value in security_lsmprop_to_secctx()
    - Fix compilation errors when CONFIG_SECURITY is not defined
v2: Feedback on v1
    - Share common code in apparmor_*_to_secctx()
    - Remove stale review tags
    - Fix mistakes in comments

Casey Schaufler (13):
  LSM: Add the lsm_prop data structure.
  LSM: Use lsm_prop in security_audit_rule_match
  LSM: Add lsmprop_to_secctx hook
  Audit: maintain an lsm_prop in audit_context
  LSM: Use lsm_prop in security_ipc_getsecid
  Audit: Update shutdown LSM data
  LSM: Use lsm_prop in security_current_getsecid
  LSM: Use lsm_prop in security_inode_getsecid
  Audit: use an lsm_prop in audit_names
  LSM: Create new security_cred_getlsmprop LSM hook
  Audit: Change context data from secid to lsm_prop
  Use lsm_prop for audit data
  LSM: Remove lsm_prop scaffolding

 include/linux/lsm/apparmor.h          | 17 +++++
 include/linux/lsm/bpf.h               | 16 +++++
 include/linux/lsm/selinux.h           | 16 +++++
 include/linux/lsm/smack.h             | 17 +++++
 include/linux/lsm_hook_defs.h         | 20 ++++--
 include/linux/security.h              | 98 ++++++++++++++++++++++-----
 include/net/netlabel.h                |  2 +-
 kernel/audit.c                        | 21 +++---
 kernel/audit.h                        |  7 +-
 kernel/auditfilter.c                  |  9 +--
 kernel/auditsc.c                      | 61 ++++++++---------
 net/netlabel/netlabel_unlabeled.c     |  2 +-
 net/netlabel/netlabel_user.c          |  7 +-
 net/netlabel/netlabel_user.h          |  2 +-
 security/apparmor/audit.c             |  4 +-
 security/apparmor/include/audit.h     |  2 +-
 security/apparmor/include/secid.h     |  2 +
 security/apparmor/lsm.c               | 17 +++--
 security/apparmor/secid.c             | 21 +++++-
 security/integrity/ima/ima.h          |  8 +--
 security/integrity/ima/ima_api.c      |  6 +-
 security/integrity/ima/ima_appraise.c |  6 +-
 security/integrity/ima/ima_main.c     | 60 ++++++++--------
 security/integrity/ima/ima_policy.c   | 20 +++---
 security/security.c                   | 96 ++++++++++++++++++--------
 security/selinux/hooks.c              | 49 +++++++++-----
 security/selinux/include/audit.h      |  5 +-
 security/selinux/ss/services.c        |  6 +-
 security/smack/smack_lsm.c            | 96 ++++++++++++++++----------
 security/smack/smackfs.c              |  4 +-
 30 files changed, 469 insertions(+), 228 deletions(-)
 create mode 100644 include/linux/lsm/apparmor.h
 create mode 100644 include/linux/lsm/bpf.h
 create mode 100644 include/linux/lsm/selinux.h
 create mode 100644 include/linux/lsm/smack.h