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

Paul Moore
2018-04-19T01:46:49Z

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