6:10 a.m.
2018-04-06 12:37 GMT+02:00 Richard Guy Briggs <rgb(a)redhat.com>:
On 2018-04-06 10:43, Ondrej Mosnacek wrote:
> Current implementation of auditing by executable name only implements
> the 'equal' operator. This patch extends it to also support the 'not
> equal' operator.
>
> See: https://github.com/linux-audit/audit-kernel/issues/53
>
> Signed-off-by: Ondrej Mosnacek <omosnace(a)redhat.com>
> ---
>
> Hi Paul,
>
> this turned out to be easier than I anticipated so I'm sending the patch
> already :) I hope I got everything right. Note that the userspace tools
> also need to be updated to check the feature bit and allow/disallow the
> operator based on that.
Do we really need to eat up a feature bit for this? The kernel will
simply return -EINVAL if it isn't supported. That will make userspace
implementation easier.
The problem then would be that if someone tried to use the not equal
operator on an older kernel, he would get some generic error message
instead of the current "exe only takes = operator".
This is how it would be handled with the feature bit:
https://github.com/WOnder93/audit-userspace/commit/c2260940e0216042efa11f...
If the consensus is that it's not worth it, I will resend it without that part.
> Ondrej
>
> include/uapi/linux/audit.h | 18 ++++++++++--------
> kernel/auditfilter.c | 2 +-
> kernel/auditsc.c | 2 ++
> 3 files changed, 13 insertions(+), 9 deletions(-)
>
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index 4e61a9e05132..03393f7e8932 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -333,13 +333,14 @@ enum {
> #define AUDIT_STATUS_BACKLOG_WAIT_TIME 0x0020
> #define AUDIT_STATUS_LOST 0x0040
>
> -#define AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT 0x00000001
> -#define AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME 0x00000002
> -#define AUDIT_FEATURE_BITMAP_EXECUTABLE_PATH 0x00000004
> -#define AUDIT_FEATURE_BITMAP_EXCLUDE_EXTEND 0x00000008
> -#define AUDIT_FEATURE_BITMAP_SESSIONID_FILTER 0x00000010
> -#define AUDIT_FEATURE_BITMAP_LOST_RESET 0x00000020
> -#define AUDIT_FEATURE_BITMAP_FILTER_FS 0x00000040
> +#define AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT 0x00000001
> +#define AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME 0x00000002
> +#define AUDIT_FEATURE_BITMAP_EXECUTABLE_PATH 0x00000004
> +#define AUDIT_FEATURE_BITMAP_EXCLUDE_EXTEND 0x00000008
> +#define AUDIT_FEATURE_BITMAP_SESSIONID_FILTER 0x00000010
> +#define AUDIT_FEATURE_BITMAP_LOST_RESET 0x00000020
> +#define AUDIT_FEATURE_BITMAP_FILTER_FS 0x00000040
> +#define AUDIT_FEATURE_BITMAP_EXECUTABLE_PATH_NEQ 0x00000080
>
> #define AUDIT_FEATURE_BITMAP_ALL (AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT | \
> AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME | \
> @@ -347,7 +348,8 @@ enum {
> AUDIT_FEATURE_BITMAP_EXCLUDE_EXTEND | \
> AUDIT_FEATURE_BITMAP_SESSIONID_FILTER | \
> AUDIT_FEATURE_BITMAP_LOST_RESET | \
> - AUDIT_FEATURE_BITMAP_FILTER_FS)
> + AUDIT_FEATURE_BITMAP_FILTER_FS | \
> + AUDIT_FEATURE_BITMAP_EXECUTABLE_PATH_NEQ)
>
> /* deprecated: AUDIT_VERSION_* */
> #define AUDIT_VERSION_LATEST AUDIT_FEATURE_BITMAP_ALL
> diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> index d7a807e81451..a0c5a3ec6e60 100644
> --- a/kernel/auditfilter.c
> +++ b/kernel/auditfilter.c
> @@ -426,7 +426,7 @@ static int audit_field_valid(struct audit_entry *entry, struct
audit_field *f)
> return -EINVAL;
> break;
> case AUDIT_EXE:
> - if (f->op != Audit_equal)
> + if (f->op != Audit_not_equal && f->op != Audit_equal)
> return -EINVAL;
> if (entry->rule.listnr != AUDIT_FILTER_EXIT)
> return -EINVAL;
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 4e0a4ac803db..479c031ec54c 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -471,6 +471,8 @@ static int audit_filter_rules(struct task_struct *tsk,
> break;
> case AUDIT_EXE:
> result = audit_exe_compare(tsk, rule->exe);
> + if (f->op == Audit_not_equal)
> + result = !result;
> break;
> case AUDIT_UID:
> result = audit_uid_comparator(cred->uid, f->op,
f->uid);
> --
> 2.14.3
>
- RGB
--
Richard Guy Briggs <rgb(a)redhat.com>
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
--
Ondrej Mosnacek <omosnace at redhat dot com>
Associate Software Engineer, Security Technologies
Red Hat, Inc.