Re: [PATCH ghak90 V5 08/10] audit: add containerid filtering

From: Richard Guy Briggs
Date: Mon Mar 18 2019 - 19:47:34 EST

On 2019-03-18 21:02, Ondrej Mosnacek wrote:
> On Fri, Mar 15, 2019 at 7:35 PM Richard Guy Briggs <rgb@xxxxxxxxxx> wrote:
> >
> > Implement audit container identifier filtering using the AUDIT_CONTID
> > 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.
> >
> > The feature indicator is AUDIT_FEATURE_BITMAP_CONTAINERID.
> >
> > See: https://github.com/linux-audit/audit-kernel/issues/91
> > See: https://github.com/linux-audit/audit-userspace/issues/40
> > See: https://github.com/linux-audit/audit-testsuite/issues/64
> > See: https://github.com/linux-audit/audit-kernel/wiki/RFE-Audit-Container-ID
> > Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
> > Acked-by: Serge Hallyn <serge@xxxxxxxxxx>
> > ---
> > 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 6db5aba7cc01..fa19fa408931 100644
> > --- a/include/linux/audit.h
> > +++ b/include/linux/audit.h
> > @@ -77,6 +77,7 @@ 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 a6383e28b2c8..741ab6f38294 100644
> > --- a/include/uapi/linux/audit.h
> > +++ b/include/uapi/linux/audit.h
> > @@ -265,6 +265,7 @@
> > #define AUDIT_LOGINUID_SET 24
> > #define AUDIT_SESSIONID 25 /* Session ID */
> > #define AUDIT_FSTYPE 26 /* FileSystem Type */
> > +#define AUDIT_CONTID 27 /* Container ID */
> >
> > /* These are ONLY useful when checking
> > * at syscall exit time (AUDIT_AT_EXIT). */
> > @@ -345,6 +346,7 @@ 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 0x00000080
> >
> > #define AUDIT_FEATURE_BITMAP_ALL (AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT | \
> > AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME | \
> > @@ -352,7 +354,8 @@ 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)
> >
> > /* deprecated: AUDIT_VERSION_* */
> > #define AUDIT_VERSION_LATEST AUDIT_FEATURE_BITMAP_ALL
> > diff --git a/kernel/audit.h b/kernel/audit.h
> > index 2a1a8b8a8019..3a40b608bf8d 100644
> > --- a/kernel/audit.h
> > +++ b/kernel/audit.h
> > @@ -230,6 +230,7 @@ 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 add360b46b38..516b8e58959e 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_CONTID:
> > if (f->op != Audit_not_equal && f->op != Audit_equal)
> > return -EINVAL;
> > break;
> > @@ -582,6 +583,14 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
> > }
> > entry->rule.exe = audit_mark;
> > break;
> > + case AUDIT_CONTID:
> > + 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;
> > }
> > }
> >
> > @@ -664,6 +673,11 @@ 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_CONTID:
> > + data->buflen += data->values[i] = sizeof(u64);
> > + for (i = 0; i < sizeof(u64); i++)
> > + ((char *)bufp)[i] = ((char *)&f->val64)[i];
>
> How about just:
>
> memcpy(bufp, &f->val64, sizeof(u64));
>
> instead of the awkward for loop? It is simpler and also more in line
> with the code in audit_pack_string().

I'll grant you that. I'll use that instead.

> Also, doesn't this loop interfere with the outer loop that also uses
> 'i' as the control variable?

Yes, it does. Thank you for catching that. Doing a auditctl -l reveals
this.

> > + break;
> > case AUDIT_LOGINUID_SET:
> > if (krule->pflags & AUDIT_LOGINUID_LEGACY && !f->val) {
> > data->fields[i] = AUDIT_LOGINUID;
> > @@ -750,6 +764,10 @@ 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_CONTID:
> > + if (a->fields[i].val64 != b->fields[i].val64)
> > + return 1;
> > + break;
> > default:
> > if (a->fields[i].val != b->fields[i].val)
> > return 1;
> > @@ -1206,6 +1224,31 @@ 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) {
> > @@ -1344,6 +1387,10 @@ int audit_filter(int msgtype, unsigned int listtype)
> > result = audit_comparator(audit_loginuid_set(current),
> > f->op, f->val);
> > break;
> > + case AUDIT_CONTID:
> > + result = audit_comparator64(audit_get_contid(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 aa5d13b4fbbb..2d74238e9638 100644
> > --- a/kernel/auditsc.c
> > +++ b/kernel/auditsc.c
> > @@ -616,6 +616,9 @@ 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_CONTID:
> > + result = audit_comparator64(audit_get_contid(tsk), f->op, f->val64);
> > + break;
> > case AUDIT_SUBJ_USER:
> > case AUDIT_SUBJ_ROLE:
> > case AUDIT_SUBJ_TYPE:
> > --
> > 1.8.3.1
> >
>
>
> --
> Ondrej Mosnacek <omosnace at redhat dot com>
> Associate Software Engineer, Security Technologies
> Red Hat, Inc.

- 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