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

Casey Schaufler
2020-03-10T01:26:04Z

On 3/6/2020 6:24 PM, Paul Moore wrote:
> On Fri, Feb 21, 2020 at 7:06 PM Casey Schaufler <casey@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@tycho.nsa.gov>
>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>> Cc: netdev@vger.kernel.org
>> Cc: linux-audit@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.