Subject: Re: [RFC PATCH ghak32 V2 01/13] audit: add container id

From: Steve Grubb <[email-masked]>
Date: Thu, 17 May 2018 17:00:53 -0400

On Fri, 16 Mar 2018 05:00:28 -0400
Richard Guy Briggs <[email-masked]> wrote:

> Implement the proc fs write to set the audit container ID of a
> process, emitting an AUDIT_CONTAINER record to document the event.
> 
> This is a write from the container orchestrator task to a proc entry
> of the form /proc/PID/containerid where PID is the process ID of the
> newly created task that is to become the first task in a container,
> or an additional task added to a container.
> 
> The write expects up to a u64 value (unset: 18446744073709551615).
> 
> This will produce a record such as this:
> type=CONTAINER msg=audit(1519903238.968:261): op=set pid=596 uid=0
> subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 auid=0
> tty=pts0 ses=1 opid=596 old-contid=18446744073709551615 contid=123455
> res=0

The was one thing I was wondering about. Currently when we set the
loginuid, the record is AUDIT_LOGINUID. The corollary is that when we
set the container id, the event should be AUDIT_CONTAINERID or
AUDIT_CONTAINER_ID.

During syscall events, the path info is returned in a a record simply
called AUDIT_PATH, cwd info is returned in AUDIT_CWD. So, rather than
calling the record that gets attached to everything
AUDIT_CONTAINER_INFO, how about simply AUDIT_CONTAINER.

> The "op" field indicates an initial set.  The "pid" to "ses" fields
> are the orchestrator while the "opid" field is the object's PID, the
> process being "contained".  Old and new container ID values are given
> in the "contid" fields, while res indicates its success.
> 
> It is not permitted to self-set, unset or re-set the container ID.  A
> child inherits its parent's container ID, but then can be set only
> once after.
> 
> See: https://github.com/linux-audit/audit-kernel/issues/32
> 
> Signed-off-by: Richard Guy Briggs <[email-masked]>
> ---
>  fs/proc/base.c             | 37 ++++++++++++++++++++
>  include/linux/audit.h      | 16 +++++++++
>  include/linux/init_task.h  |  4 ++-
>  include/linux/sched.h      |  1 +
>  include/uapi/linux/audit.h |  2 ++
>  kernel/auditsc.c           | 84
> ++++++++++++++++++++++++++++++++++++++++++++++ 6 files changed, 143
> insertions(+), 1 deletion(-)
> 
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 60316b5..6ce4fbe 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -1299,6 +1299,41 @@ static ssize_t proc_sessionid_read(struct file
> * file, char __user * buf, .read		= proc_sessionid_read,
>  	.llseek		= generic_file_llseek,
>  };
> +
> +static ssize_t proc_containerid_write(struct file *file, const char
> __user *buf,
> +				   size_t count, loff_t *ppos)
> +{
> +	struct inode *inode = file_inode(file);
> +	u64 containerid;
> +	int rv;
> +	struct task_struct *task = get_proc_task(inode);
> +
> +	if (!task)
> +		return -ESRCH;
> +	if (*ppos != 0) {
> +		/* No partial writes. */
> +		put_task_struct(task);
> +		return -EINVAL;
> +	}
> +
> +	rv = kstrtou64_from_user(buf, count, 10, &containerid);
> +	if (rv < 0) {
> +		put_task_struct(task);
> +		return rv;
> +	}
> +
> +	rv = audit_set_containerid(task, containerid);
> +	put_task_struct(task);
> +	if (rv < 0)
> +		return rv;
> +	return count;
> +}
> +
> +static const struct file_operations proc_containerid_operations = {
> +	.write		= proc_containerid_write,
> +	.llseek		= generic_file_llseek,
> +};
> +
>  #endif
>  
>  #ifdef CONFIG_FAULT_INJECTION
> @@ -2961,6 +2996,7 @@ static int proc_pid_patch_state(struct seq_file
> *m, struct pid_namespace *ns, #ifdef CONFIG_AUDITSYSCALL
>  	REG("loginuid",   S_IWUSR|S_IRUGO, proc_loginuid_operations),
>  	REG("sessionid",  S_IRUGO, proc_sessionid_operations),
> +	REG("containerid", S_IWUSR, proc_containerid_operations),
>  #endif
>  #ifdef CONFIG_FAULT_INJECTION
>  	REG("make-it-fail", S_IRUGO|S_IWUSR,
> proc_fault_inject_operations), @@ -3355,6 +3391,7 @@ static int
> proc_tid_comm_permission(struct inode *inode, int mask) #ifdef
> CONFIG_AUDITSYSCALL REG("loginuid",  S_IWUSR|S_IRUGO,
> proc_loginuid_operations), REG("sessionid",  S_IRUGO,
> proc_sessionid_operations),
> +	REG("containerid", S_IWUSR, proc_containerid_operations),
>  #endif
>  #ifdef CONFIG_FAULT_INJECTION
>  	REG("make-it-fail", S_IRUGO|S_IWUSR,
> proc_fault_inject_operations), diff --git a/include/linux/audit.h
> b/include/linux/audit.h index af410d9..fe4ba3f 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -29,6 +29,7 @@
>  
>  #define AUDIT_INO_UNSET ((unsigned long)-1)
>  #define AUDIT_DEV_UNSET ((dev_t)-1)
> +#define INVALID_CID AUDIT_CID_UNSET
>  
>  struct audit_sig_info {
>  	uid_t		uid;
> @@ -321,6 +322,7 @@ static inline void audit_ptrace(struct
> task_struct *t) extern int auditsc_get_stamp(struct audit_context
> *ctx, struct timespec64 *t, unsigned int *serial);
>  extern int audit_set_loginuid(kuid_t loginuid);
> +extern int audit_set_containerid(struct task_struct *tsk, u64
> containerid); 
>  static inline kuid_t audit_get_loginuid(struct task_struct *tsk)
>  {
> @@ -332,6 +334,11 @@ static inline unsigned int
> audit_get_sessionid(struct task_struct *tsk) return tsk->sessionid;
>  }
>  
> +static inline u64 audit_get_containerid(struct task_struct *tsk)
> +{
> +	return tsk->containerid;
> +}
> +
>  extern void __audit_ipc_obj(struct kern_ipc_perm *ipcp);
>  extern void __audit_ipc_set_perm(unsigned long qbytes, uid_t uid,
> gid_t gid, umode_t mode); extern void __audit_bprm(struct
> linux_binprm *bprm); @@ -517,6 +524,10 @@ static inline unsigned int
> audit_get_sessionid(struct task_struct *tsk) {
>  	return -1;
>  }
> +static inline kuid_t audit_get_containerid(struct task_struct *tsk)
> +{
> +	return INVALID_CID;
> +}
>  static inline void audit_ipc_obj(struct kern_ipc_perm *ipcp)
>  { }
>  static inline void audit_ipc_set_perm(unsigned long qbytes, uid_t
> uid, @@ -581,6 +592,11 @@ static inline bool
> audit_loginuid_set(struct task_struct *tsk) return
> uid_valid(audit_get_loginuid(tsk)); }
>  
> +static inline bool audit_containerid_set(struct task_struct *tsk)
> +{
> +	return audit_get_containerid(tsk) != INVALID_CID;
> +}
> +
>  static inline void audit_log_string(struct audit_buffer *ab, const
> char *buf) {
>  	audit_log_n_string(ab, buf, strlen(buf));
> diff --git a/include/linux/init_task.h b/include/linux/init_task.h
> index 6a53262..046bd0a 100644
> --- a/include/linux/init_task.h
> +++ b/include/linux/init_task.h
> @@ -18,6 +18,7 @@
>  #include <linux/sched/rt.h>
>  #include <linux/livepatch.h>
>  #include <linux/mm_types.h>
> +#include <linux/audit.h>
>  
>  #include <asm/thread_info.h>
>  
> @@ -120,7 +121,8 @@
>  #ifdef CONFIG_AUDITSYSCALL
>  #define INIT_IDS \
>  	.loginuid = INVALID_UID, \
> -	.sessionid = (unsigned int)-1,
> +	.sessionid = (unsigned int)-1, \
> +	.containerid = INVALID_CID,
>  #else
>  #define INIT_IDS
>  #endif
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index d258826..1b82191 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -796,6 +796,7 @@ struct task_struct {
>  #ifdef CONFIG_AUDITSYSCALL
>  	kuid_t				loginuid;
>  	unsigned int			sessionid;
> +	u64				containerid;
>  #endif
>  	struct seccomp			seccomp;
>  
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index 4e61a9e..921a71f 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -71,6 +71,7 @@
>  #define AUDIT_TTY_SET		1017	/* Set TTY auditing
> status */ #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		1020	/* Define the container id
> and information */ #define AUDIT_FIRST_USER_MSG	1100	/*
> Userspace messages mostly uninteresting to kernel */ #define
> AUDIT_USER_AVC		1107	/* We filter this
> differently */ @@ -465,6 +466,7 @@ struct audit_tty_status { };
>  
>  #define AUDIT_UID_UNSET (unsigned int)-1
> +#define AUDIT_CID_UNSET ((u64)-1)
>  
>  /* audit_rule_data supports filter rules with both integer and string
>   * fields.  It corresponds with AUDIT_ADD_RULE, AUDIT_DEL_RULE and
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 4e0a4ac..29c8482 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -2073,6 +2073,90 @@ int audit_set_loginuid(kuid_t loginuid)
>  	return rc;
>  }
>  
> +static int audit_set_containerid_perm(struct task_struct *task, u64
> containerid) +{
> +	struct task_struct *parent;
> +	u64 pcontainerid, ccontainerid;
> +
> +	/* Don't allow to set our own containerid */
> +	if (current == task)
> +		return -EPERM;
> +	/* Don't allow the containerid to be unset */
> +	if (!cid_valid(containerid))
> +		return -EINVAL;
> +	/* if we don't have caps, reject */
> +	if (!capable(CAP_AUDIT_CONTROL))
> +		return -EPERM;
> +	/* if containerid is unset, allow */
> +	if (!audit_containerid_set(task))
> +		return 0;
> +	/* it is already set, and not inherited from the parent,
> reject */
> +	ccontainerid = audit_get_containerid(task);
> +	rcu_read_lock();
> +	parent = rcu_dereference(task->real_parent);
> +	rcu_read_unlock();
> +	task_lock(parent);
> +	pcontainerid = audit_get_containerid(parent);
> +	task_unlock(parent);
> +	if (ccontainerid != pcontainerid)
> +		return -EPERM;
> +	return 0;
> +}
> +
> +static void audit_log_set_containerid(struct task_struct *task, u64
> oldcontainerid,
> +				      u64 containerid, int rc)
> +{
> +	struct audit_buffer *ab;
> +	uid_t uid;
> +	struct tty_struct *tty;
> +
> +	if (!audit_enabled)
> +		return;
> +
> +	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_CONTAINER);
> +	if (!ab)
> +		return;
> +
> +	uid = from_kuid(&init_user_ns, task_uid(current));
> +	tty = audit_get_tty(current);
> +
> +	audit_log_format(ab, "op=set pid=%d uid=%u",
> task_tgid_nr(current), uid);
> +	audit_log_task_context(ab);
> +	audit_log_format(ab, " auid=%u tty=%s ses=%u opid=%d
> old-contid=%llu contid=%llu res=%d",

The preferred ordering would be: op, opid, old-contid, contid, pid, uid,
tty, ses, subj, comm, exe, res. This groups the searchable fields
together using the most common ordering so that parsing is simple.

Thanks,
-Steve

> +			 from_kuid(&init_user_ns,
> audit_get_loginuid(current)),
> +			 tty ? tty_name(tty) : "(none)",
> audit_get_sessionid(current),
> +			 task_tgid_nr(task), oldcontainerid,
> containerid, !rc); +
> +	audit_put_tty(tty);
> +	audit_log_end(ab);
> +}
> +
> +/**
> + * audit_set_containerid - set current task's audit_context
> containerid
> + * @containerid: containerid value
> + *
> + * Returns 0 on success, -EPERM on permission failure.
> + *
> + * Called (set) from fs/proc/base.c::proc_containerid_write().
> + */
> +int audit_set_containerid(struct task_struct *task, u64 containerid)
> +{
> +	u64 oldcontainerid;
> +	int rc;
> +
> +	oldcontainerid = audit_get_containerid(task);
> +
> +	rc = audit_set_containerid_perm(task, containerid);
> +	if (!rc) {
> +		task_lock(task);
> +		task->containerid = containerid;
> +		task_unlock(task);
> +	}
> +
> +	audit_log_set_containerid(task, oldcontainerid, containerid,
> rc);
> +	return rc;
> +}
> +
>  /**
>   * __audit_mq_open - record audit data for a POSIX MQ open
>   * @oflag: open flag