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

From: Paul Moore <paul@paul-moore.com>
To: Richard Guy Briggs <rgb@redhat.com>
Cc: cgroups@vger.kernel.org, containers@lists.linux-foundation.org,
	linux-api@vger.kernel.org,
	Linux-Audit Mailing List <linux-audit@redhat.com>,
	linux-fsdevel@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	netdev@vger.kernel.org, ebiederm@xmission.com, luto@kernel.org,
	jlayton@redhat.com, carlos@redhat.com, dhowells@redhat.com,
	viro@zeniv.linux.org.uk, simo@redhat.com,
	Eric Paris <eparis@parisplace.org>,
	serge@hallyn.com
Subject: Re: [RFC PATCH ghak32 V2 04/13] audit: add containerid filtering
Date: Wed, 18 Apr 2018 20:24:27 -0400	[thread overview]
Message-ID: <CAHC9VhRVGTCVJxG3Etcs-aOpr71A7xGsn5VPhskUG35rmQ7WUw@mail.gmail.com> (raw)
In-Reply-To: <b933f93762435990e9b1e6d5aebf15f186ac8951.1521179281.git.rgb@redhat.com>

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
www.paul-moore.com