Re: [PATCH ghak25 v3 3/3] audit: add subj creds to NETFILTER_CFG record to cover async unregister

[Richard Guy Briggs]

On 2020-03-17 17:30, Richard Guy Briggs wrote:
> Some table unregister actions seem to be initiated by the kernel to
> garbage collect unused tables that are not initiated by any userspace
> actions.  It was found to be necessary to add the subject credentials to
> cover this case to reveal the source of these actions.  A sample record:
> 
>   type=NETFILTER_CFG msg=audit(2020-03-11 21:25:21.491:269) : table=nat family=bridge entries=0 op=unregister pid=153 uid=root auid=unset tty=(none) ses=unset subj=system_u:system_r:kernel_t:s0 comm=kworker/u4:2 exe=(null)

Given the precedent set by bpf unload, I'd really rather drop this patch
that adds subject credentials.

Similarly with ghak25's subject credentials, but they were already
present and that would change an existing record format, so it isn't
quite as justifiable in that case.

> Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
> ---
>  kernel/auditsc.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index dbb056feccb9..6c233076dfb7 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -2557,12 +2557,30 @@ void __audit_log_nfcfg(const char *name, u8 af, unsigned int nentries,
>  		       enum audit_nfcfgop op)
>  {
>  	struct audit_buffer *ab;
> +	const struct cred *cred;
> +	struct tty_struct *tty;
> +	char comm[sizeof(current->comm)];
>  
>  	ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_NETFILTER_CFG);
>  	if (!ab)
>  		return;
>  	audit_log_format(ab, "table=%s family=%u entries=%u op=%s",
>  			 name, af, nentries, audit_nfcfgs[op].s);
> +
> +	cred = current_cred();
> +	tty = audit_get_tty();
> +	audit_log_format(ab, " pid=%u uid=%u auid=%u tty=%s ses=%u",
> +			 task_pid_nr(current),
> +			 from_kuid(&init_user_ns, cred->uid),
> +			 from_kuid(&init_user_ns, audit_get_loginuid(current)),
> +			 tty ? tty_name(tty) : "(none)",
> +			 audit_get_sessionid(current));
> +	audit_put_tty(tty);
> +	audit_log_task_context(ab); /* subj= */
> +	audit_log_format(ab, " comm=");
> +	audit_log_untrustedstring(ab, get_task_comm(comm, current));
> +	audit_log_d_path_exe(ab, current->mm); /* exe= */
> +
>  	audit_log_end(ab);
>  }
>  EXPORT_SYMBOL_GPL(__audit_log_nfcfg);
> -- 
> 1.8.3.1
> 
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- RGB

--
Richard Guy Briggs <rgb@xxxxxxxxxx>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635