Re: [RFC PATCH ghak32 V2 11/13] audit: add support for containerid to network namespaces

[Paul Moore <paul@paul-moore.com>]

On Fri, Mar 16, 2018 at 5:00 AM, Richard Guy Briggs <rgb@redhat.com> wrote:
> Audit events could happen in a network namespace outside of a task
> context due to packets received from the net that trigger an auditing
> rule prior to being associated with a running task.  The network
> namespace could in use by multiple containers by association to the
> tasks in that network namespace.  We still want a way to attribute
> these events to any potential containers.  Keep a list per network
> namespace to track these container identifiiers.
>
> Add/increment the container identifier on:
> - initial setting of the container id via /proc
> - clone/fork call that inherits a container identifier
> - unshare call that inherits a container identifier
> - setns call that inherits a container identifier
> Delete/decrement the container identifier on:
> - an inherited container id dropped when child set
> - process exit
> - unshare call that drops a net namespace
> - setns call that drops a net namespace
>
> See: https://github.com/linux-audit/audit-kernel/issues/32
> See: https://github.com/linux-audit/audit-testsuite/issues/64
> Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> ---
>  include/linux/audit.h       |  7 +++++++
>  include/net/net_namespace.h | 12 ++++++++++++
>  kernel/auditsc.c            |  9 ++++++---
>  kernel/nsproxy.c            |  6 ++++++
>  net/core/net_namespace.c    | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 76 insertions(+), 3 deletions(-)

...

> diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
> index 0490084..343a428 100644
> --- a/include/net/net_namespace.h
> +++ b/include/net/net_namespace.h
> @@ -33,6 +33,7 @@
>  #include <linux/ns_common.h>
>  #include <linux/idr.h>
>  #include <linux/skbuff.h>
> +#include <linux/audit.h>
>
>  struct user_namespace;
>  struct proc_dir_entry;
> @@ -150,6 +151,7 @@ struct net {
>  #endif
>         struct sock             *diag_nlsk;
>         atomic_t                fnhe_genid;
> +       struct list_head        audit_containerid;
>  } __randomize_layout;

We talked about this briefly off-list, you should be using audit_net
and the net_generic mechanism instead of this.

>  #include <linux/seq_file_net.h>
> @@ -301,6 +303,16 @@ static inline struct net *read_pnet(const possible_net_t *pnet)
>  #define __net_initconst        __initconst
>  #endif
>
> +#ifdef CONFIG_NET_NS
> +void net_add_audit_containerid(struct net *net, u64 containerid);
> +void net_del_audit_containerid(struct net *net, u64 containerid);
> +#else
> +static inline void net_add_audit_containerid(struct net *, u64)
> +{ }
> +static inline void net_del_audit_containerid(struct net *, u64)
> +{ }
> +#endif
> +
>  int peernet2id_alloc(struct net *net, struct net *peer);
>  int peernet2id(struct net *net, struct net *peer);
>  bool peernet_has_id(struct net *net, struct net *peer);
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 2f02ed9..208da962 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -75,6 +75,7 @@
>  #include <linux/uaccess.h>
>  #include <linux/fsnotify_backend.h>
>  #include <uapi/linux/limits.h>
> +#include <net/net_namespace.h>
>
>  #include "audit.h"
>
> @@ -2175,16 +2176,18 @@ static void audit_log_set_containerid(struct task_struct *task, u64 oldcontainer
>   */
>  int audit_set_containerid(struct task_struct *task, u64 containerid)
>  {
> -       u64 oldcontainerid;
> +       u64 oldcontainerid = audit_get_containerid(task);
>         int rc;
> -
> -       oldcontainerid = audit_get_containerid(task);
> +       struct net *net = task->nsproxy->net_ns;
>
>         rc = audit_set_containerid_perm(task, containerid);
>         if (!rc) {
> +               if (cid_valid(oldcontainerid))
> +                       net_del_audit_containerid(net, oldcontainerid);

Using audit_net we can handle this internal to audit, which is a Good Thing.

>                 task_lock(task);
>                 task->containerid = containerid;
>                 task_unlock(task);
> +               net_add_audit_containerid(net, containerid);

Same.

>         }
>
>         audit_log_set_containerid(task, oldcontainerid, containerid, rc);
> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> index f6c5d33..d9f1090 100644
> --- a/kernel/nsproxy.c
> +++ b/kernel/nsproxy.c
> @@ -140,6 +140,7 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
>         struct nsproxy *old_ns = tsk->nsproxy;
>         struct user_namespace *user_ns = task_cred_xxx(tsk, user_ns);
>         struct nsproxy *new_ns;
> +       u64 containerid = audit_get_containerid(tsk);
>
>         if (likely(!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
>                               CLONE_NEWPID | CLONE_NEWNET |
> @@ -167,6 +168,7 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
>                 return  PTR_ERR(new_ns);
>
>         tsk->nsproxy = new_ns;
> +       net_add_audit_containerid(new_ns->net_ns, containerid);
>         return 0;
>  }

Hopefully we can handle this in audit_net_init(), we just need to
figure out where we can get the correct task_struct for the audit
container ID (some backpointer in the net struct?).

> @@ -217,6 +219,7 @@ int unshare_nsproxy_namespaces(unsigned long unshare_flags,
>  void switch_task_namespaces(struct task_struct *p, struct nsproxy *new)
>  {
>         struct nsproxy *ns;
> +       u64 containerid = audit_get_containerid(p);
>
>         might_sleep();
>
> @@ -224,6 +227,9 @@ void switch_task_namespaces(struct task_struct *p, struct nsproxy *new)
>         ns = p->nsproxy;
>         p->nsproxy = new;
>         task_unlock(p);
> +       net_del_audit_containerid(ns->net_ns, containerid);
> +       if (new)
> +               net_add_audit_containerid(new->net_ns, containerid);

Okay, we might need a hook here for switching namespaces, but I would
much rather it be a generic audit hook that calls directly into audit.

-- 
paul moore
www.paul-moore.com