Re: [RFC PATCH ghak32 V2 04/13] audit: add containerid filtering

Paul Moore
2018-04-19T00:24:27Z

On Fri, Mar 16, 2018 at 5:00 AM, Richard Guy Briggs <rgb@redhat.com> wrote:
> Implement container ID filtering using the AUDIT_CONTAINERID field name
> to send an 8-character string representing a u64 since the value field
> is only u32.
>
> Sending it as two u32 was considered, but gathering and comparing two
> fields was more complex.

My only worry here is that you aren't really sending a string in the
ASCII sense, you are sending an 8 byte buffer (that better be NUL
terminated) that happens to be an unsigned 64-bit integer. To be
clear, I'm okay with that (it's protected by AUDIT_CONTAINERID), and
the code is okay with that, I just want us to pause for a minute and
make sure that is an okay thing to do long term.

> The feature indicator is AUDIT_FEATURE_BITMAP_CONTAINERID_FILTER.
>
> This requires support from userspace to be useful.
> See: https://github.com/linux-audit/audit-userspace/issues/40
> Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> ---
> include/linux/audit.h | 1 +
> include/uapi/linux/audit.h | 5 ++++-
> kernel/audit.h | 1 +
> kernel/auditfilter.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++
> kernel/auditsc.c | 3 +++
> 5 files changed, 56 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index 3acbe9d..f10ca1b 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -76,6 +76,7 @@ struct audit_field {
> u32 type;
> union {
> u32 val;
> + u64 val64;
> kuid_t uid;
> kgid_t gid;
> struct {
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index e83ccbd..8443a8f 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -262,6 +262,7 @@
> #define AUDIT_LOGINUID_SET 24
> #define AUDIT_SESSIONID 25 /* Session ID */
> #define AUDIT_FSTYPE 26 /* FileSystem Type */
> +#define AUDIT_CONTAINERID 27 /* Container ID */
>
> /* These are ONLY useful when checking
> * at syscall exit time (AUDIT_AT_EXIT). */
> @@ -342,6 +343,7 @@ enum {
> #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_CONTAINERID_FILTER 0x00000080
>
> #define AUDIT_FEATURE_BITMAP_ALL (AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT | \
> AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME | \
> @@ -349,7 +351,8 @@ 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_CONTAINERID_FILTER)
>
> /* deprecated: AUDIT_VERSION_* */
> #define AUDIT_VERSION_LATEST AUDIT_FEATURE_BITMAP_ALL
> diff --git a/kernel/audit.h b/kernel/audit.h
> index 214e149..aaa651a 100644
> --- a/kernel/audit.h
> +++ b/kernel/audit.h
> @@ -234,6 +234,7 @@ static inline int audit_hash_ino(u32 ino)
>
> extern int audit_match_class(int class, unsigned syscall);
> extern int audit_comparator(const u32 left, const u32 op, const u32 right);
> +extern int audit_comparator64(const u64 left, const u32 op, const u64 right);
> extern int audit_uid_comparator(kuid_t left, u32 op, kuid_t right);
> extern int audit_gid_comparator(kgid_t left, u32 op, kgid_t right);
> extern int parent_len(const char *path);
> diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> index d7a807e..c4c8746 100644
> --- a/kernel/auditfilter.c
> +++ b/kernel/auditfilter.c
> @@ -410,6 +410,7 @@ static int audit_field_valid(struct audit_entry *entry, struct audit_field *f)
> /* FALL THROUGH */
> case AUDIT_ARCH:
> case AUDIT_FSTYPE:
> + case AUDIT_CONTAINERID:
> if (f->op != Audit_not_equal && f->op != Audit_equal)
> return -EINVAL;
> break;
> @@ -584,6 +585,14 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
> }
> entry->rule.exe = audit_mark;
> break;
> + case AUDIT_CONTAINERID:
> + if (f->val != sizeof(u64))
> + goto exit_free;
> + str = audit_unpack_string(&bufp, &remain, f->val);
> + if (IS_ERR(str))
> + goto exit_free;
> + f->val64 = ((u64 *)str)[0];
> + break;
> }
> }
>
> @@ -666,6 +675,11 @@ static struct audit_rule_data *audit_krule_to_data(struct audit_krule *krule)
> data->buflen += data->values[i] =
> audit_pack_string(&bufp, audit_mark_path(krule->exe));
> break;
> + case AUDIT_CONTAINERID:
> + data->buflen += data->values[i] = sizeof(u64);
> + for (i = 0; i < sizeof(u64); i++)
> + ((char *)bufp)[i] = ((char *)&f->val64)[i];
> + break;
> case AUDIT_LOGINUID_SET:
> if (krule->pflags & AUDIT_LOGINUID_LEGACY && !f->val) {
> data->fields[i] = AUDIT_LOGINUID;
> @@ -752,6 +766,10 @@ static int audit_compare_rule(struct audit_krule *a, struct audit_krule *b)
> if (!gid_eq(a->fields[i].gid, b->fields[i].gid))
> return 1;
> break;
> + case AUDIT_CONTAINERID:
> + if (a->fields[i].val64 != b->fields[i].val64)
> + return 1;
> + break;
> default:
> if (a->fields[i].val != b->fields[i].val)
> return 1;
> @@ -1210,6 +1228,31 @@ int audit_comparator(u32 left, u32 op, u32 right)
> }
> }
>
> +int audit_comparator64(u64 left, u32 op, u64 right)
> +{
> + switch (op) {
> + case Audit_equal:
> + return (left == right);
> + case Audit_not_equal:
> + return (left != right);
> + case Audit_lt:
> + return (left < right);
> + case Audit_le:
> + return (left <= right);
> + case Audit_gt:
> + return (left > right);
> + case Audit_ge:
> + return (left >= right);
> + case Audit_bitmask:
> + return (left & right);
> + case Audit_bittest:
> + return ((left & right) == right);
> + default:
> + BUG();
> + return 0;
> + }
> +}
> +
> int audit_uid_comparator(kuid_t left, u32 op, kuid_t right)
> {
> switch (op) {
> @@ -1348,6 +1391,10 @@ int audit_filter(int msgtype, unsigned int listtype)
> result = audit_comparator(audit_loginuid_set(current),
> f->op, f->val);
> break;
> + case AUDIT_CONTAINERID:
> + result = audit_comparator64(audit_get_containerid(current),
> + f->op, f->val64);
> + break;
> case AUDIT_MSGTYPE:
> result = audit_comparator(msgtype, f->op, f->val);
> break;
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 65be110..2bba324 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -614,6 +614,9 @@ static int audit_filter_rules(struct task_struct *tsk,
> case AUDIT_LOGINUID_SET:
> result = audit_comparator(audit_loginuid_set(tsk), f->op, f->val);
> break;
> + case AUDIT_CONTAINERID:
> + result = audit_comparator64(audit_get_containerid(tsk), f->op, f->val64);
> + break;
> case AUDIT_SUBJ_USER:
> case AUDIT_SUBJ_ROLE:
> case AUDIT_SUBJ_TYPE:
> --
> 1.8.3.1
>
> --
> Linux-audit mailing list
> Linux-audit@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-audit

--
paul moore