[PATCH v15 20/23] Audit: Add subj_LSM fields when necessary

[Casey Schaufler]

On 3/6/2020 6:24 PM, Paul Moore wrote:
> On Fri, Feb 21, 2020 at 7:06 PM Casey Schaufler <casey at schaufler-ca.com> wrote:
>> Add record entries to identify subject data for all of the
>> security modules when there is more than one.
>>
>> Acked-by: Stephen Smalley <sds at tycho.nsa.gov>
>> Signed-off-by: Casey Schaufler <casey at schaufler-ca.com>
>> Cc: netdev at vger.kernel.org
>> Cc: linux-audit at redhat.com
>> ---
>>  drivers/android/binder.c                |  2 +-
>>  include/linux/audit.h                   |  1 +
>>  include/linux/security.h                |  9 ++++-
>>  include/net/scm.h                       |  3 +-
>>  kernel/audit.c                          | 40 ++++++++++++++++++-
>>  kernel/audit_fsnotify.c                 |  1 +
>>  kernel/auditfilter.c                    |  1 +
>>  kernel/auditsc.c                        | 10 +++--
>>  net/ipv4/ip_sockglue.c                  |  2 +-
>>  net/netfilter/nf_conntrack_netlink.c    |  4 +-
>>  net/netfilter/nf_conntrack_standalone.c |  2 +-
>>  net/netfilter/nfnetlink_queue.c         |  2 +-
>>  net/netlabel/netlabel_unlabeled.c       | 11 ++++--
>>  net/netlabel/netlabel_user.c            |  2 +-
>>  net/xfrm/xfrm_policy.c                  |  2 +
>>  net/xfrm/xfrm_state.c                   |  2 +
>>  security/integrity/ima/ima_api.c        |  1 +
>>  security/integrity/integrity_audit.c    |  1 +
>>  security/security.c                     | 51 +++++++++++++++++++++++--
>>  19 files changed, 124 insertions(+), 23 deletions(-)
> ...
>
>> diff --git a/kernel/audit.c b/kernel/audit.c
>> index a25097cfe623..c3a1d8d2d33c 100644
>> --- a/kernel/audit.c
>> +++ b/kernel/audit.c
>> @@ -2054,6 +2061,33 @@ void audit_log_key(struct audit_buffer *ab, char *key)
>>                 audit_log_format(ab, "(null)");
>>  }
>>
>> +void audit_log_task_lsms(struct audit_buffer *ab)
>> +{
>> +       int i;
>> +       const char *lsm;
>> +       struct lsmblob blob;
>> +       struct lsmcontext context;
>> +
>> +       /*
>> +        * Don't do anything unless there is more than one LSM
>> +        * with a security context to report.
>> +        */
>> +       if (security_lsm_slot_name(1) == NULL)
>> +               return;
>> +
>> +       security_task_getsecid(current, &blob);
>> +
>> +       for (i = 0; i < LSMBLOB_ENTRIES; i++) {
>> +               lsm = security_lsm_slot_name(i);
>> +               if (lsm == NULL)
>> +                       break;
>> +               if (security_secid_to_secctx(&blob, &context, i))
>> +                       continue;
>> +               audit_log_format(ab, " subj_%s=%s", lsm, context.context);
>> +               security_release_secctx(&context);
>> +       }
>> +}
>> +
>>  int audit_log_task_context(struct audit_buffer *ab)
>>  {
>>         int error;
>> @@ -2064,7 +2098,7 @@ int audit_log_task_context(struct audit_buffer *ab)
>>         if (!lsmblob_is_set(&blob))
>>                 return 0;
>>
>> -       error = security_secid_to_secctx(&blob, &context);
>> +       error = security_secid_to_secctx(&blob, &context, LSMBLOB_FIRST);
>>         if (error) {
>>                 if (error != -EINVAL)
>>                         goto error_path;
> Sorry, please disregard my previous ACK.

:(

> We should treat "subj=" similar to how we treat "obj="; if there is
> more than one LSM loaded the "subj=" should be set to "?" with the
> "subj_XXX=" set to the appropriate label for the named LSM.  This
> patch looks like it is always using LSMBLOB_FIRST and not "?" when
> multiple LSMs are present.

I'm fine with that, although I could see someone suggesting that
would constitute breaking backward compatibility.