On Thu, Sep 16, 2021 at 9:33 AM Richard Guy Briggs [off-list ref] wrote:

On 2021-09-15 12:49, Paul Moore wrote:

quoted

This patch adds basic auditing to io_uring operations, regardless of
their context.  This is accomplished by allocating audit_context
structures for the io-wq worker and io_uring SQPOLL kernel threads
as well as explicitly auditing the io_uring operations in
io_issue_sqe().  Individual io_uring operations can bypass auditing
through the "audit_skip" field in the struct io_op_def definition for
the operation; although great care must be taken so that security
relevant io_uring operations do not bypass auditing; please contact
the audit mailing list (see the MAINTAINERS file) with any questions.

The io_uring operations are audited using a new AUDIT_URINGOP record,
an example is shown below:

  type=UNKNOWN[1336] msg=audit(1630523381.288:260):
    uring_op=19 success=yes exit=0 items=0 ppid=853 pid=1204
    uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0
    subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
    key=(null)
    AUID="root" UID="root" GID="root" EUID="root" SUID="root"
    FSUID="root" EGID="root" SGID="root" FSGID="root"

Thanks to Richard Guy Briggs for review and feedback.

I share Steve's concerns about the missing auid and ses.  The userspace
log interpreter conjured up AUID="root" from the absent auid=.

Some of the creds are here including ppid, pid, a herd of *id and subj.
*Something* initiated this action and then delegated it to iouring to
carry out.  That should be in there somewhere.  You had a concern about
shared queues and mis-attribution.  All of these creds including auid
and ses should be kept together to get this right.

Look, there are a lot of things about io_uring that frustrate me from
a security perspective - this is one of them - but I've run out of
ways to say it's not possible to reliably capture the audit ID or
session ID here.  With io_uring it is possible to submit an io_uring
operation, and capture the results, by simply reading and writing to a
mmap'd buffer.  Yes, it would be nice to have that information, but I
don't believe there is a practical way to capture it.  If you have any
suggestions on how to do so, please share, but please make it
concrete; hand wavy solutions aren't useful at this stage.

As for the userspace mysteriously creating an AUID out of thin air,
that was my mistake: I simply removed the "auid=" field from the
example and didn't remove the additional fields, e.g. AUID, that
auditd appends to the end of the record.  I've updated the commit
description with a freshly generated record and removed the auditd
bonus bits as those probably shouldn't be shown in an example of a
kernel generated audit record.  I'm not going to repost the patchset
just for this small edit to the description, but I have force-pushed
the update to the selinux/working-io_uring branch.

-- 
paul moore
www.paul-moore.com