[ghak90,V6,05/10] audit: add contid support for signalling the audit daemon
diff mbox series

Message ID baa5f3c6d4aa7f9fec903ebb51949f3ac743d067.1554732921.git.rgb@redhat.com
State New
Headers show
Series
  • audit: implement container identifier
Related show

Commit Message

Richard Guy Briggs April 9, 2019, 3:39 a.m. UTC
Add audit container identifier support to the action of signalling the
audit daemon.

Since this would need to add an element to the audit_sig_info struct,
a new record type AUDIT_SIGNAL_INFO2 was created with a new
audit_sig_info2 struct.  Corresponding support is required in the
userspace code to reflect the new record request and reply type.
An older userspace won't break since it won't know to request this
record type.

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
---
 include/linux/audit.h       |  7 +++++++
 include/uapi/linux/audit.h  |  1 +
 kernel/audit.c              | 27 +++++++++++++++++++++++++++
 kernel/audit.h              |  1 +
 kernel/auditsc.c            |  1 +
 security/selinux/nlmsgtab.c |  1 +
 6 files changed, 38 insertions(+)

Comments

Ondrej Mosnacek April 9, 2019, 12:57 p.m. UTC | #1
On Tue, Apr 9, 2019 at 5:40 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> Add audit container identifier support to the action of signalling the
> audit daemon.
>
> Since this would need to add an element to the audit_sig_info struct,
> a new record type AUDIT_SIGNAL_INFO2 was created with a new
> audit_sig_info2 struct.  Corresponding support is required in the
> userspace code to reflect the new record request and reply type.
> An older userspace won't break since it won't know to request this
> record type.
>
> Signed-off-by: Richard Guy Briggs <rgb@redhat.com>

This looks good to me.

Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>

Although I'm wondering if we shouldn't try to future-proof the
AUDIT_SIGNAL_INFO2 format somehow, so that we don't need to add
another AUDIT_SIGNAL_INFO3 when the need arises to add yet-another
identifier to it... The simplest solution I can come up with is to add
a "version" field at the beginning (set to 2 initially), then v<N>_len
at the beginning of data for version <N>. But maybe this is too
complicated for too little gain...

> ---
>  include/linux/audit.h       |  7 +++++++
>  include/uapi/linux/audit.h  |  1 +
>  kernel/audit.c              | 27 +++++++++++++++++++++++++++
>  kernel/audit.h              |  1 +
>  kernel/auditsc.c            |  1 +
>  security/selinux/nlmsgtab.c |  1 +
>  6 files changed, 38 insertions(+)
>
> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index 43438192ca2a..c2dec9157463 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -37,6 +37,13 @@ struct audit_sig_info {
>         char            ctx[0];
>  };
>
> +struct audit_sig_info2 {
> +       uid_t           uid;
> +       pid_t           pid;
> +       u64             cid;
> +       char            ctx[0];
> +};
> +
>  struct audit_buffer;
>  struct audit_context;
>  struct inode;
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index 55fde9970762..10cc67926cf1 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -72,6 +72,7 @@
>  #define AUDIT_SET_FEATURE      1018    /* Turn an audit feature on or off */
>  #define AUDIT_GET_FEATURE      1019    /* Get which features are enabled */
>  #define AUDIT_CONTAINER_OP     1020    /* Define the container id and info */
> +#define AUDIT_SIGNAL_INFO2     1021    /* Get info auditd signal sender */
>
>  #define AUDIT_FIRST_USER_MSG   1100    /* Userspace messages mostly uninteresting to kernel */
>  #define AUDIT_USER_AVC         1107    /* We filter this differently */
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 3e0af53f3c4d..87e1d367f98c 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -138,6 +138,7 @@ struct audit_net {
>  kuid_t         audit_sig_uid = INVALID_UID;
>  pid_t          audit_sig_pid = -1;
>  u32            audit_sig_sid = 0;
> +u64            audit_sig_cid = AUDIT_CID_UNSET;
>
>  /* Records can be lost in several ways:
>     0) [suppressed in audit_alloc]
> @@ -1097,6 +1098,7 @@ static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type)
>         case AUDIT_ADD_RULE:
>         case AUDIT_DEL_RULE:
>         case AUDIT_SIGNAL_INFO:
> +       case AUDIT_SIGNAL_INFO2:
>         case AUDIT_TTY_GET:
>         case AUDIT_TTY_SET:
>         case AUDIT_TRIM:
> @@ -1260,6 +1262,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>         struct audit_buffer     *ab;
>         u16                     msg_type = nlh->nlmsg_type;
>         struct audit_sig_info   *sig_data;
> +       struct audit_sig_info2  *sig_data2;
>         char                    *ctx = NULL;
>         u32                     len;
>
> @@ -1519,6 +1522,30 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>                                  sig_data, sizeof(*sig_data) + len);
>                 kfree(sig_data);
>                 break;
> +       case AUDIT_SIGNAL_INFO2:
> +               len = 0;
> +               if (audit_sig_sid) {
> +                       err = security_secid_to_secctx(audit_sig_sid, &ctx, &len);
> +                       if (err)
> +                               return err;
> +               }
> +               sig_data2 = kmalloc(sizeof(*sig_data2) + len, GFP_KERNEL);
> +               if (!sig_data2) {
> +                       if (audit_sig_sid)
> +                               security_release_secctx(ctx, len);
> +                       return -ENOMEM;
> +               }
> +               sig_data2->uid = from_kuid(&init_user_ns, audit_sig_uid);
> +               sig_data2->pid = audit_sig_pid;
> +               if (audit_sig_sid) {
> +                       memcpy(sig_data2->ctx, ctx, len);
> +                       security_release_secctx(ctx, len);
> +               }
> +               sig_data2->cid = audit_sig_cid;
> +               audit_send_reply(skb, seq, AUDIT_SIGNAL_INFO2, 0, 0,
> +                                sig_data2, sizeof(*sig_data2) + len);
> +               kfree(sig_data2);
> +               break;
>         case AUDIT_TTY_GET: {
>                 struct audit_tty_status s;
>                 unsigned int t;
> diff --git a/kernel/audit.h b/kernel/audit.h
> index e2912924af0d..c5ac6436317e 100644
> --- a/kernel/audit.h
> +++ b/kernel/audit.h
> @@ -345,6 +345,7 @@ extern void audit_filter_inodes(struct task_struct *tsk,
>  extern pid_t audit_sig_pid;
>  extern kuid_t audit_sig_uid;
>  extern u32 audit_sig_sid;
> +extern u64 audit_sig_cid;
>
>  extern int audit_filter(int msgtype, unsigned int listtype);
>
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index eea445b7a181..0a29a00feaf1 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -2405,6 +2405,7 @@ int audit_signal_info(int sig, struct task_struct *t)
>                 else
>                         audit_sig_uid = uid;
>                 security_task_getsecid(current, &audit_sig_sid);
> +               audit_sig_cid = audit_get_contid(current);
>         }
>
>         if (!audit_signals || audit_dummy_context())
> diff --git a/security/selinux/nlmsgtab.c b/security/selinux/nlmsgtab.c
> index 9cec81209617..682fe7397762 100644
> --- a/security/selinux/nlmsgtab.c
> +++ b/security/selinux/nlmsgtab.c
> @@ -132,6 +132,7 @@ struct nlmsg_perm {
>         { AUDIT_DEL_RULE,       NETLINK_AUDIT_SOCKET__NLMSG_WRITE    },
>         { AUDIT_USER,           NETLINK_AUDIT_SOCKET__NLMSG_RELAY    },
>         { AUDIT_SIGNAL_INFO,    NETLINK_AUDIT_SOCKET__NLMSG_READ     },
> +       { AUDIT_SIGNAL_INFO2,   NETLINK_AUDIT_SOCKET__NLMSG_READ     },
>         { AUDIT_TRIM,           NETLINK_AUDIT_SOCKET__NLMSG_WRITE    },
>         { AUDIT_MAKE_EQUIV,     NETLINK_AUDIT_SOCKET__NLMSG_WRITE    },
>         { AUDIT_TTY_GET,        NETLINK_AUDIT_SOCKET__NLMSG_READ     },
> --
> 1.8.3.1
>


--
Ondrej Mosnacek <omosnace at redhat dot com>
Software Engineer, Security Technologies
Red Hat, Inc.

--
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Linux-audit@redhat.com
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Paul Moore April 9, 2019, 1:40 p.m. UTC | #2
On Tue, Apr 9, 2019 at 8:58 AM Ondrej Mosnacek <omosnace@redhat.com> wrote:
>
> On Tue, Apr 9, 2019 at 5:40 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> > Add audit container identifier support to the action of signalling the
> > audit daemon.
> >
> > Since this would need to add an element to the audit_sig_info struct,
> > a new record type AUDIT_SIGNAL_INFO2 was created with a new
> > audit_sig_info2 struct.  Corresponding support is required in the
> > userspace code to reflect the new record request and reply type.
> > An older userspace won't break since it won't know to request this
> > record type.
> >
> > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
>
> This looks good to me.
>
> Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
>
> Although I'm wondering if we shouldn't try to future-proof the
> AUDIT_SIGNAL_INFO2 format somehow, so that we don't need to add
> another AUDIT_SIGNAL_INFO3 when the need arises to add yet-another
> identifier to it... The simplest solution I can come up with is to add
> a "version" field at the beginning (set to 2 initially), then v<N>_len
> at the beginning of data for version <N>. But maybe this is too
> complicated for too little gain...

FWIW, I believe the long term solution to this is the fabled netlink
attribute approach that we haven't talked about in some time, but I
keep dreaming about (it has been mostly on the back burner becasue 1)
time and 2) didn't want to impact the audit container ID work).  While
I'm not opposed to trying to make things like this a bit more robust
by adding version fields and similar things, there are still so many
(so very many) problems with the audit kernel/userspace interface that
still need to be addressed.
Neil Horman April 9, 2019, 1:46 p.m. UTC | #3
On Tue, Apr 09, 2019 at 02:57:50PM +0200, Ondrej Mosnacek wrote:
> On Tue, Apr 9, 2019 at 5:40 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> > Add audit container identifier support to the action of signalling the
> > audit daemon.
> >
> > Since this would need to add an element to the audit_sig_info struct,
> > a new record type AUDIT_SIGNAL_INFO2 was created with a new
> > audit_sig_info2 struct.  Corresponding support is required in the
> > userspace code to reflect the new record request and reply type.
> > An older userspace won't break since it won't know to request this
> > record type.
> >
> > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> 
> This looks good to me.
> 
> Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
> 
> Although I'm wondering if we shouldn't try to future-proof the
> AUDIT_SIGNAL_INFO2 format somehow, so that we don't need to add
> another AUDIT_SIGNAL_INFO3 when the need arises to add yet-another
> identifier to it... The simplest solution I can come up with is to add
> a "version" field at the beginning (set to 2 initially), then v<N>_len
> at the beginning of data for version <N>. But maybe this is too
> complicated for too little gain...
> 
So, I'm not sure how often this needs to be revised (if its not often, this may
be just fine), but if future proofing is warranted, it might be worthwhile to
just use the netlink TLV encoding thats available today.  The kernel has a suite
of nla_put_<type> macros (like nla_put_u32()), and the userspace netlink library
can parse those messages fairly easily.  It would let you send arbitrary length
messages with a terminator type at the end of the array.

That said, I don't think we want to do that right now for just this message.  A
better approach would be to do this now, and in a subsequent patch, create an
AUDIT version 2 netlink protocol that converts all the messages we send to that
format for consistency.  Such a change would be large and warrant its own patch
set and review.

I'm good with this patch as it is

Acked-by: Neil Horman <nhorman@tuxdriver.com>

> > ---
> >  include/linux/audit.h       |  7 +++++++
> >  include/uapi/linux/audit.h  |  1 +
> >  kernel/audit.c              | 27 +++++++++++++++++++++++++++
> >  kernel/audit.h              |  1 +
> >  kernel/auditsc.c            |  1 +
> >  security/selinux/nlmsgtab.c |  1 +
> >  6 files changed, 38 insertions(+)
> >
> > diff --git a/include/linux/audit.h b/include/linux/audit.h
> > index 43438192ca2a..c2dec9157463 100644
> > --- a/include/linux/audit.h
> > +++ b/include/linux/audit.h
> > @@ -37,6 +37,13 @@ struct audit_sig_info {
> >         char            ctx[0];
> >  };
> >
> > +struct audit_sig_info2 {
> > +       uid_t           uid;
> > +       pid_t           pid;
> > +       u64             cid;
> > +       char            ctx[0];
> > +};
> > +
> >  struct audit_buffer;
> >  struct audit_context;
> >  struct inode;
> > diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> > index 55fde9970762..10cc67926cf1 100644
> > --- a/include/uapi/linux/audit.h
> > +++ b/include/uapi/linux/audit.h
> > @@ -72,6 +72,7 @@
> >  #define AUDIT_SET_FEATURE      1018    /* Turn an audit feature on or off */
> >  #define AUDIT_GET_FEATURE      1019    /* Get which features are enabled */
> >  #define AUDIT_CONTAINER_OP     1020    /* Define the container id and info */
> > +#define AUDIT_SIGNAL_INFO2     1021    /* Get info auditd signal sender */
> >
> >  #define AUDIT_FIRST_USER_MSG   1100    /* Userspace messages mostly uninteresting to kernel */
> >  #define AUDIT_USER_AVC         1107    /* We filter this differently */
> > diff --git a/kernel/audit.c b/kernel/audit.c
> > index 3e0af53f3c4d..87e1d367f98c 100644
> > --- a/kernel/audit.c
> > +++ b/kernel/audit.c
> > @@ -138,6 +138,7 @@ struct audit_net {
> >  kuid_t         audit_sig_uid = INVALID_UID;
> >  pid_t          audit_sig_pid = -1;
> >  u32            audit_sig_sid = 0;
> > +u64            audit_sig_cid = AUDIT_CID_UNSET;
> >
> >  /* Records can be lost in several ways:
> >     0) [suppressed in audit_alloc]
> > @@ -1097,6 +1098,7 @@ static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type)
> >         case AUDIT_ADD_RULE:
> >         case AUDIT_DEL_RULE:
> >         case AUDIT_SIGNAL_INFO:
> > +       case AUDIT_SIGNAL_INFO2:
> >         case AUDIT_TTY_GET:
> >         case AUDIT_TTY_SET:
> >         case AUDIT_TRIM:
> > @@ -1260,6 +1262,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
> >         struct audit_buffer     *ab;
> >         u16                     msg_type = nlh->nlmsg_type;
> >         struct audit_sig_info   *sig_data;
> > +       struct audit_sig_info2  *sig_data2;
> >         char                    *ctx = NULL;
> >         u32                     len;
> >
> > @@ -1519,6 +1522,30 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
> >                                  sig_data, sizeof(*sig_data) + len);
> >                 kfree(sig_data);
> >                 break;
> > +       case AUDIT_SIGNAL_INFO2:
> > +               len = 0;
> > +               if (audit_sig_sid) {
> > +                       err = security_secid_to_secctx(audit_sig_sid, &ctx, &len);
> > +                       if (err)
> > +                               return err;
> > +               }
> > +               sig_data2 = kmalloc(sizeof(*sig_data2) + len, GFP_KERNEL);
> > +               if (!sig_data2) {
> > +                       if (audit_sig_sid)
> > +                               security_release_secctx(ctx, len);
> > +                       return -ENOMEM;
> > +               }
> > +               sig_data2->uid = from_kuid(&init_user_ns, audit_sig_uid);
> > +               sig_data2->pid = audit_sig_pid;
> > +               if (audit_sig_sid) {
> > +                       memcpy(sig_data2->ctx, ctx, len);
> > +                       security_release_secctx(ctx, len);
> > +               }
> > +               sig_data2->cid = audit_sig_cid;
> > +               audit_send_reply(skb, seq, AUDIT_SIGNAL_INFO2, 0, 0,
> > +                                sig_data2, sizeof(*sig_data2) + len);
> > +               kfree(sig_data2);
> > +               break;
> >         case AUDIT_TTY_GET: {
> >                 struct audit_tty_status s;
> >                 unsigned int t;
> > diff --git a/kernel/audit.h b/kernel/audit.h
> > index e2912924af0d..c5ac6436317e 100644
> > --- a/kernel/audit.h
> > +++ b/kernel/audit.h
> > @@ -345,6 +345,7 @@ extern void audit_filter_inodes(struct task_struct *tsk,
> >  extern pid_t audit_sig_pid;
> >  extern kuid_t audit_sig_uid;
> >  extern u32 audit_sig_sid;
> > +extern u64 audit_sig_cid;
> >
> >  extern int audit_filter(int msgtype, unsigned int listtype);
> >
> > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > index eea445b7a181..0a29a00feaf1 100644
> > --- a/kernel/auditsc.c
> > +++ b/kernel/auditsc.c
> > @@ -2405,6 +2405,7 @@ int audit_signal_info(int sig, struct task_struct *t)
> >                 else
> >                         audit_sig_uid = uid;
> >                 security_task_getsecid(current, &audit_sig_sid);
> > +               audit_sig_cid = audit_get_contid(current);
> >         }
> >
> >         if (!audit_signals || audit_dummy_context())
> > diff --git a/security/selinux/nlmsgtab.c b/security/selinux/nlmsgtab.c
> > index 9cec81209617..682fe7397762 100644
> > --- a/security/selinux/nlmsgtab.c
> > +++ b/security/selinux/nlmsgtab.c
> > @@ -132,6 +132,7 @@ struct nlmsg_perm {
> >         { AUDIT_DEL_RULE,       NETLINK_AUDIT_SOCKET__NLMSG_WRITE    },
> >         { AUDIT_USER,           NETLINK_AUDIT_SOCKET__NLMSG_RELAY    },
> >         { AUDIT_SIGNAL_INFO,    NETLINK_AUDIT_SOCKET__NLMSG_READ     },
> > +       { AUDIT_SIGNAL_INFO2,   NETLINK_AUDIT_SOCKET__NLMSG_READ     },
> >         { AUDIT_TRIM,           NETLINK_AUDIT_SOCKET__NLMSG_WRITE    },
> >         { AUDIT_MAKE_EQUIV,     NETLINK_AUDIT_SOCKET__NLMSG_WRITE    },
> >         { AUDIT_TTY_GET,        NETLINK_AUDIT_SOCKET__NLMSG_READ     },
> > --
> > 1.8.3.1
> >
> 
> 
> --
> Ondrej Mosnacek <omosnace at redhat dot com>
> Software Engineer, Security Technologies
> Red Hat, Inc.
> 

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Neil Horman April 9, 2019, 1:48 p.m. UTC | #4
On Tue, Apr 09, 2019 at 09:40:58AM -0400, Paul Moore wrote:
> On Tue, Apr 9, 2019 at 8:58 AM Ondrej Mosnacek <omosnace@redhat.com> wrote:
> >
> > On Tue, Apr 9, 2019 at 5:40 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > Add audit container identifier support to the action of signalling the
> > > audit daemon.
> > >
> > > Since this would need to add an element to the audit_sig_info struct,
> > > a new record type AUDIT_SIGNAL_INFO2 was created with a new
> > > audit_sig_info2 struct.  Corresponding support is required in the
> > > userspace code to reflect the new record request and reply type.
> > > An older userspace won't break since it won't know to request this
> > > record type.
> > >
> > > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> >
> > This looks good to me.
> >
> > Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
> >
> > Although I'm wondering if we shouldn't try to future-proof the
> > AUDIT_SIGNAL_INFO2 format somehow, so that we don't need to add
> > another AUDIT_SIGNAL_INFO3 when the need arises to add yet-another
> > identifier to it... The simplest solution I can come up with is to add
> > a "version" field at the beginning (set to 2 initially), then v<N>_len
> > at the beginning of data for version <N>. But maybe this is too
> > complicated for too little gain...
> 
> FWIW, I believe the long term solution to this is the fabled netlink
> attribute approach that we haven't talked about in some time, but I
> keep dreaming about (it has been mostly on the back burner becasue 1)
> time and 2) didn't want to impact the audit container ID work).  While
> I'm not opposed to trying to make things like this a bit more robust
> by adding version fields and similar things, there are still so many
> (so very many) problems with the audit kernel/userspace interface that
> still need to be addressed.
> 

Agreed, this change as-is is in keeping with the message structure that audit
has today, and so is ok with me, but the long term goal should be a conversion
to netlink attributes for all audit messages.  Thats a big undertaking and
should be addressed separately though.

Neil

> -- 
> paul moore
> www.paul-moore.com
> 

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Richard Guy Briggs April 9, 2019, 1:53 p.m. UTC | #5
On 2019-04-09 09:40, Paul Moore wrote:
> On Tue, Apr 9, 2019 at 8:58 AM Ondrej Mosnacek <omosnace@redhat.com> wrote:
> > On Tue, Apr 9, 2019 at 5:40 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > Add audit container identifier support to the action of signalling the
> > > audit daemon.
> > >
> > > Since this would need to add an element to the audit_sig_info struct,
> > > a new record type AUDIT_SIGNAL_INFO2 was created with a new
> > > audit_sig_info2 struct.  Corresponding support is required in the
> > > userspace code to reflect the new record request and reply type.
> > > An older userspace won't break since it won't know to request this
> > > record type.
> > >
> > > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> >
> > This looks good to me.
> >
> > Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
> >
> > Although I'm wondering if we shouldn't try to future-proof the
> > AUDIT_SIGNAL_INFO2 format somehow, so that we don't need to add
> > another AUDIT_SIGNAL_INFO3 when the need arises to add yet-another
> > identifier to it... The simplest solution I can come up with is to add
> > a "version" field at the beginning (set to 2 initially), then v<N>_len
> > at the beginning of data for version <N>. But maybe this is too
> > complicated for too little gain...
> 
> FWIW, I believe the long term solution to this is the fabled netlink
> attribute approach that we haven't talked about in some time, but I
> keep dreaming about (it has been mostly on the back burner becasue 1)
> time and 2) didn't want to impact the audit container ID work).  While
> I'm not opposed to trying to make things like this a bit more robust
> by adding version fields and similar things, there are still so many
> (so very many) problems with the audit kernel/userspace interface that
> still need to be addressed.

While this particular message type is used very infrequently, adding a
version field to every message type strikes me as a huge overhead for
the small likelihood of the format needing to change.

I'd prefer to just key it off the AUDIT_FEATURE_BITMAP or some other
easily detectable change in this distinguishing feature, such as the
presence of /proc/self/audit_containerid, which is what I've done in the
accompanying userspace patchset that I'm preparing to post that works
with this change.

Neil, you are right that netlink has useful mechanisms to help with this
sort of thing, but we're not quite there yet.

> paul moore

- RGB

--
Richard Guy Briggs <rgb@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

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Ondrej Mosnacek April 9, 2019, 2 p.m. UTC | #6
On Tue, Apr 9, 2019 at 3:49 PM Neil Horman <nhorman@tuxdriver.com> wrote:
> On Tue, Apr 09, 2019 at 09:40:58AM -0400, Paul Moore wrote:
> > On Tue, Apr 9, 2019 at 8:58 AM Ondrej Mosnacek <omosnace@redhat.com> wrote:
> > >
> > > On Tue, Apr 9, 2019 at 5:40 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > > Add audit container identifier support to the action of signalling the
> > > > audit daemon.
> > > >
> > > > Since this would need to add an element to the audit_sig_info struct,
> > > > a new record type AUDIT_SIGNAL_INFO2 was created with a new
> > > > audit_sig_info2 struct.  Corresponding support is required in the
> > > > userspace code to reflect the new record request and reply type.
> > > > An older userspace won't break since it won't know to request this
> > > > record type.
> > > >
> > > > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> > >
> > > This looks good to me.
> > >
> > > Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
> > >
> > > Although I'm wondering if we shouldn't try to future-proof the
> > > AUDIT_SIGNAL_INFO2 format somehow, so that we don't need to add
> > > another AUDIT_SIGNAL_INFO3 when the need arises to add yet-another
> > > identifier to it... The simplest solution I can come up with is to add
> > > a "version" field at the beginning (set to 2 initially), then v<N>_len
> > > at the beginning of data for version <N>. But maybe this is too
> > > complicated for too little gain...
> >
> > FWIW, I believe the long term solution to this is the fabled netlink
> > attribute approach that we haven't talked about in some time, but I
> > keep dreaming about (it has been mostly on the back burner becasue 1)
> > time and 2) didn't want to impact the audit container ID work).  While
> > I'm not opposed to trying to make things like this a bit more robust
> > by adding version fields and similar things, there are still so many
> > (so very many) problems with the audit kernel/userspace interface that
> > still need to be addressed.
> >
>
> Agreed, this change as-is is in keeping with the message structure that audit
> has today, and so is ok with me, but the long term goal should be a conversion
> to netlink attributes for all audit messages.  Thats a big undertaking and
> should be addressed separately though.

Yeah, you both have a good point that doing it now and only for this
message is not necessarily better than not doing it at all. And doing
a general overhaul is out of scope for this series, obviously. I
didn't really mind the current solution before and I mind it even less
now, so consider me satisfied :) I was really just thinking out
loud...
Paul Moore April 9, 2019, 2:07 p.m. UTC | #7
On Tue, Apr 9, 2019 at 9:49 AM Neil Horman <nhorman@tuxdriver.com> wrote:
> On Tue, Apr 09, 2019 at 09:40:58AM -0400, Paul Moore wrote:
> > On Tue, Apr 9, 2019 at 8:58 AM Ondrej Mosnacek <omosnace@redhat.com> wrote:
> > >
> > > On Tue, Apr 9, 2019 at 5:40 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > > Add audit container identifier support to the action of signalling the
> > > > audit daemon.
> > > >
> > > > Since this would need to add an element to the audit_sig_info struct,
> > > > a new record type AUDIT_SIGNAL_INFO2 was created with a new
> > > > audit_sig_info2 struct.  Corresponding support is required in the
> > > > userspace code to reflect the new record request and reply type.
> > > > An older userspace won't break since it won't know to request this
> > > > record type.
> > > >
> > > > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> > >
> > > This looks good to me.
> > >
> > > Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
> > >
> > > Although I'm wondering if we shouldn't try to future-proof the
> > > AUDIT_SIGNAL_INFO2 format somehow, so that we don't need to add
> > > another AUDIT_SIGNAL_INFO3 when the need arises to add yet-another
> > > identifier to it... The simplest solution I can come up with is to add
> > > a "version" field at the beginning (set to 2 initially), then v<N>_len
> > > at the beginning of data for version <N>. But maybe this is too
> > > complicated for too little gain...
> >
> > FWIW, I believe the long term solution to this is the fabled netlink
> > attribute approach that we haven't talked about in some time, but I
> > keep dreaming about (it has been mostly on the back burner becasue 1)
> > time and 2) didn't want to impact the audit container ID work).  While
> > I'm not opposed to trying to make things like this a bit more robust
> > by adding version fields and similar things, there are still so many
> > (so very many) problems with the audit kernel/userspace interface that
> > still need to be addressed.
>
> Agreed, this change as-is is in keeping with the message structure that audit
> has today, and so is ok with me, but the long term goal should be a conversion
> to netlink attributes for all audit messages.  Thats a big undertaking and
> should be addressed separately though.

You've likely missed all the conversations around this from some time
ago, but this is the direction I want us to go towards eventually, and
yes, this is a huge undertaking (much larger than the audit container
ID work) that will need to be done in stages.

The first step is moving away from audit_log_format() to an in-kernel
audit API that separates the data from the record format; I've got a
lot of ideas on that, but as I said earlier, it's mostly on the back
burner so it doesn't hold up the audit container ID work.
Paul Moore April 9, 2019, 2:08 p.m. UTC | #8
On Tue, Apr 9, 2019 at 9:53 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> On 2019-04-09 09:40, Paul Moore wrote:
> > On Tue, Apr 9, 2019 at 8:58 AM Ondrej Mosnacek <omosnace@redhat.com> wrote:
> > > On Tue, Apr 9, 2019 at 5:40 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > > Add audit container identifier support to the action of signalling the
> > > > audit daemon.
> > > >
> > > > Since this would need to add an element to the audit_sig_info struct,
> > > > a new record type AUDIT_SIGNAL_INFO2 was created with a new
> > > > audit_sig_info2 struct.  Corresponding support is required in the
> > > > userspace code to reflect the new record request and reply type.
> > > > An older userspace won't break since it won't know to request this
> > > > record type.
> > > >
> > > > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> > >
> > > This looks good to me.
> > >
> > > Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
> > >
> > > Although I'm wondering if we shouldn't try to future-proof the
> > > AUDIT_SIGNAL_INFO2 format somehow, so that we don't need to add
> > > another AUDIT_SIGNAL_INFO3 when the need arises to add yet-another
> > > identifier to it... The simplest solution I can come up with is to add
> > > a "version" field at the beginning (set to 2 initially), then v<N>_len
> > > at the beginning of data for version <N>. But maybe this is too
> > > complicated for too little gain...
> >
> > FWIW, I believe the long term solution to this is the fabled netlink
> > attribute approach that we haven't talked about in some time, but I
> > keep dreaming about (it has been mostly on the back burner becasue 1)
> > time and 2) didn't want to impact the audit container ID work).  While
> > I'm not opposed to trying to make things like this a bit more robust
> > by adding version fields and similar things, there are still so many
> > (so very many) problems with the audit kernel/userspace interface that
> > still need to be addressed.
>
> While this particular message type is used very infrequently, adding a
> version field to every message type strikes me as a huge overhead for
> the small likelihood of the format needing to change.
>
> I'd prefer to just key it off the AUDIT_FEATURE_BITMAP or some other
> easily detectable change in this distinguishing feature, such as the
> presence of /proc/self/audit_containerid, which is what I've done in the
> accompanying userspace patchset that I'm preparing to post that works
> with this change.

That's fine.  As I said, I'm not overly worried about this; I view
this as a bit of a necessary hack.

Patch
diff mbox series

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 43438192ca2a..c2dec9157463 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -37,6 +37,13 @@  struct audit_sig_info {
 	char		ctx[0];
 };
 
+struct audit_sig_info2 {
+	uid_t		uid;
+	pid_t		pid;
+	u64		cid;
+	char		ctx[0];
+};
+
 struct audit_buffer;
 struct audit_context;
 struct inode;
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index 55fde9970762..10cc67926cf1 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -72,6 +72,7 @@ 
 #define AUDIT_SET_FEATURE	1018	/* Turn an audit feature on or off */
 #define AUDIT_GET_FEATURE	1019	/* Get which features are enabled */
 #define AUDIT_CONTAINER_OP	1020	/* Define the container id and info */
+#define AUDIT_SIGNAL_INFO2	1021	/* Get info auditd signal sender */
 
 #define AUDIT_FIRST_USER_MSG	1100	/* Userspace messages mostly uninteresting to kernel */
 #define AUDIT_USER_AVC		1107	/* We filter this differently */
diff --git a/kernel/audit.c b/kernel/audit.c
index 3e0af53f3c4d..87e1d367f98c 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -138,6 +138,7 @@  struct audit_net {
 kuid_t		audit_sig_uid = INVALID_UID;
 pid_t		audit_sig_pid = -1;
 u32		audit_sig_sid = 0;
+u64		audit_sig_cid = AUDIT_CID_UNSET;
 
 /* Records can be lost in several ways:
    0) [suppressed in audit_alloc]
@@ -1097,6 +1098,7 @@  static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type)
 	case AUDIT_ADD_RULE:
 	case AUDIT_DEL_RULE:
 	case AUDIT_SIGNAL_INFO:
+	case AUDIT_SIGNAL_INFO2:
 	case AUDIT_TTY_GET:
 	case AUDIT_TTY_SET:
 	case AUDIT_TRIM:
@@ -1260,6 +1262,7 @@  static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 	struct audit_buffer	*ab;
 	u16			msg_type = nlh->nlmsg_type;
 	struct audit_sig_info   *sig_data;
+	struct audit_sig_info2  *sig_data2;
 	char			*ctx = NULL;
 	u32			len;
 
@@ -1519,6 +1522,30 @@  static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 				 sig_data, sizeof(*sig_data) + len);
 		kfree(sig_data);
 		break;
+	case AUDIT_SIGNAL_INFO2:
+		len = 0;
+		if (audit_sig_sid) {
+			err = security_secid_to_secctx(audit_sig_sid, &ctx, &len);
+			if (err)
+				return err;
+		}
+		sig_data2 = kmalloc(sizeof(*sig_data2) + len, GFP_KERNEL);
+		if (!sig_data2) {
+			if (audit_sig_sid)
+				security_release_secctx(ctx, len);
+			return -ENOMEM;
+		}
+		sig_data2->uid = from_kuid(&init_user_ns, audit_sig_uid);
+		sig_data2->pid = audit_sig_pid;
+		if (audit_sig_sid) {
+			memcpy(sig_data2->ctx, ctx, len);
+			security_release_secctx(ctx, len);
+		}
+		sig_data2->cid = audit_sig_cid;
+		audit_send_reply(skb, seq, AUDIT_SIGNAL_INFO2, 0, 0,
+				 sig_data2, sizeof(*sig_data2) + len);
+		kfree(sig_data2);
+		break;
 	case AUDIT_TTY_GET: {
 		struct audit_tty_status s;
 		unsigned int t;
diff --git a/kernel/audit.h b/kernel/audit.h
index e2912924af0d..c5ac6436317e 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -345,6 +345,7 @@  extern void audit_filter_inodes(struct task_struct *tsk,
 extern pid_t audit_sig_pid;
 extern kuid_t audit_sig_uid;
 extern u32 audit_sig_sid;
+extern u64 audit_sig_cid;
 
 extern int audit_filter(int msgtype, unsigned int listtype);
 
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index eea445b7a181..0a29a00feaf1 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -2405,6 +2405,7 @@  int audit_signal_info(int sig, struct task_struct *t)
 		else
 			audit_sig_uid = uid;
 		security_task_getsecid(current, &audit_sig_sid);
+		audit_sig_cid = audit_get_contid(current);
 	}
 
 	if (!audit_signals || audit_dummy_context())
diff --git a/security/selinux/nlmsgtab.c b/security/selinux/nlmsgtab.c
index 9cec81209617..682fe7397762 100644
--- a/security/selinux/nlmsgtab.c
+++ b/security/selinux/nlmsgtab.c
@@ -132,6 +132,7 @@  struct nlmsg_perm {
 	{ AUDIT_DEL_RULE,	NETLINK_AUDIT_SOCKET__NLMSG_WRITE    },
 	{ AUDIT_USER,		NETLINK_AUDIT_SOCKET__NLMSG_RELAY    },
 	{ AUDIT_SIGNAL_INFO,	NETLINK_AUDIT_SOCKET__NLMSG_READ     },
+	{ AUDIT_SIGNAL_INFO2,	NETLINK_AUDIT_SOCKET__NLMSG_READ     },
 	{ AUDIT_TRIM,		NETLINK_AUDIT_SOCKET__NLMSG_WRITE    },
 	{ AUDIT_MAKE_EQUIV,	NETLINK_AUDIT_SOCKET__NLMSG_WRITE    },
 	{ AUDIT_TTY_GET,	NETLINK_AUDIT_SOCKET__NLMSG_READ     },