Re: [PATCH] audit: create explicit AUDIT_SECCOMP event type

Kees Cook
2012-11-26T17:45:56Z

On Mon, Nov 26, 2012 at 6:14 AM, Steve Grubb <sgrubb@redhat.com> wrote:
> On Monday, November 19, 2012 01:56:53 PM Kees Cook wrote:
>> The seccomp path was using AUDIT_ANOM_ABEND from when seccomp mode 1
>> could only kill a process. While we still want to make sure an audit
>> record is forced on a kill, this should use a separate record type since
>> seccomp mode 2 introduces other behaviors. In the case of "handled"
>> behaviors (process wasn't killed), only emit a record if the process is
>> under inspection.
>
> Under the old record type, we know that the process is being terminated.
> Therefore the meaning of the action is known as its implicit in the record
> type. With this new type, we need to record what behavior is being enforced on
> the process. I don't see where that is being recorded.

The action is encoded in the "code=". If one is doing seccomp
auditing, this code will be meaningful already.

> Could we add that?

I'd rather not expand the code into the separate meanings if we don't
have to. It's part of the BPF already, so it's useful to leave it
as-is, IMO.

-Kees

>
> Thanks,
> -Steve
>
>
>> Cc: Julien Tinnes <jln@google.com>
>> Cc: Will Drewry <wad@google.com>
>> Signed-off-by: Kees Cook <keescook@chromium.org>
>> ---
>> include/linux/audit.h | 3 ++-
>> include/uapi/linux/audit.h | 1 +
>> kernel/auditsc.c | 14 +++++++++++---
>> 3 files changed, 14 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/linux/audit.h b/include/linux/audit.h
>> index bce729a..9d5104d 100644
>> --- a/include/linux/audit.h
>> +++ b/include/linux/audit.h
>> @@ -157,7 +157,8 @@ void audit_core_dumps(long signr);
>>
>> static inline void audit_seccomp(unsigned long syscall, long signr, int
>> code) {
>> - if (unlikely(!audit_dummy_context()))
>> + /* Force a record to be reported if a signal was delivered. */
>> + if (signr || unlikely(!audit_dummy_context()))
>> __audit_seccomp(syscall, signr, code);
>> }
>>
>> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
>> index 76352ac..09a2d94 100644
>> --- a/include/uapi/linux/audit.h
>> +++ b/include/uapi/linux/audit.h
>> @@ -106,6 +106,7 @@
>> #define AUDIT_MMAP 1323 /* Record showing descriptor and flags in
> mmap */
>> #define AUDIT_NETFILTER_PKT 1324 /* Packets traversing netfilter chains
> */
>> #define AUDIT_NETFILTER_CFG 1325 /* Netfilter chain modifications */
>> +#define AUDIT_SECCOMP 1326 /* Secure Computing event */
>>
>> #define AUDIT_AVC 1400 /* SE Linux avc denial or grant */
>> #define AUDIT_SELINUX_ERR 1401 /* Internal SE Linux Errors */
>> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
>> index 2f186ed..157e989 100644
>> --- a/kernel/auditsc.c
>> +++ b/kernel/auditsc.c
>> @@ -2735,7 +2735,7 @@ void __audit_mmap_fd(int fd, int flags)
>> context->type = AUDIT_MMAP;
>> }
>>
>> -static void audit_log_abend(struct audit_buffer *ab, char *reason, long
>> signr) +static void audit_log_task(struct audit_buffer *ab)
>> {
>> kuid_t auid, uid;
>> kgid_t gid;
>> @@ -2753,6 +2753,11 @@ static void audit_log_abend(struct audit_buffer *ab,
>> char *reason, long signr) audit_log_task_context(ab);
>> audit_log_format(ab, " pid=%d comm=", current->pid);
>> audit_log_untrustedstring(ab, current->comm);
>> +}
>> +
>> +static void audit_log_abend(struct audit_buffer *ab, char *reason, long
>> signr) +{
>> + audit_log_task(ab);
>> audit_log_format(ab, " reason=");
>> audit_log_string(ab, reason);
>> audit_log_format(ab, " sig=%ld", signr);
>> @@ -2783,8 +2788,11 @@ void __audit_seccomp(unsigned long syscall, long
>> signr, int code) {
>> struct audit_buffer *ab;
>>
>> - ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_ANOM_ABEND);
>> - audit_log_abend(ab, "seccomp", signr);
>> + ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_SECCOMP);
>> + if (unlikely(!ab))
>> + return;
>> + audit_log_task(ab);
>> + audit_log_format(ab, " sig=%ld", signr);
>> audit_log_format(ab, " syscall=%ld", syscall);
>> audit_log_format(ab, " compat=%d", is_compat_task());
>> audit_log_format(ab, " ip=0x%lx", KSTK_EIP(current));

--
Kees Cook
Chrome OS Security