fanotify: Allow user space to pass back additional audit info
The Fanotify API can be used for access control by requesting permission
event notification. The user space tooling that uses it may have a
complicated policy that inherently contains additional context for the
decision. If this information were available in the audit trail, policy
writers can close the loop on debugging policy. Also, if this additional
information were available, it would enable the creation of tools that
can suggest changes to the policy similar to how audit2allow can help
refine labeled security.
This patchset defines a new flag (FAN_INFO) and new extensions that
define additional information which are appended after the response
structure returned from user space on a permission event. The appended
information is organized with headers containing a type and size that
can be delegated to interested subsystems. One new information type is
defined to audit the triggering rule number.
A newer kernel will work with an older userspace and an older kernel
will behave as expected and reject a newer userspace, leaving it up to
the newer userspace to test appropriately and adapt as necessary. This
is done by providing a a fully-formed FAN_INFO extension but setting the
fd to FAN_NOFD. On a capable kernel, it will succeed but issue no audit
record, whereas on an older kernel it will fail.
The audit function was updated to log the additional information in the
AUDIT_FANOTIFY record. The following are examples of the new record
format:
type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1 fan_info=3137 subj_trust=3 obj_trust=5
type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=0 subj_trust=2 obj_trust=2
Upstream Status: 'fsnotify_for_v6.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2008229
Link: https://lore.kernel.org/all/cover.1675373475.git.rgb@redhat.com
Signed-off-by: Richard Guy Briggs rgb@redhat.com
aa96f591 (Richard Guy Briggs)
fanotify,audit: Allow audit to use the full permission event response
94fae45a (Richard Guy Briggs)
fanotify: define struct members to hold response decision context
3611930a (Richard Guy Briggs)
fanotify: Ensure consistent variable type for response
fs/notify/fanotify/fanotify.c | 8 +++-
fs/notify/fanotify/fanotify.h | 6 ++-
fs/notify/fanotify/fanotify_user.c | 88 ++++++++++++++++++++++++++++----------
include/linux/audit.h | 9 ++--
include/linux/fanotify.h | 5 +++
include/uapi/linux/fanotify.h | 30 ++++++++++++-
kernel/auditsc.c | 18 ++++++--
7 files changed, 131 insertions(+), 33 deletions(-)