The attached patch addresses the problem with getting the audit daemon

shutdown credential information. It creates a new message type 
AUDIT_TERM_INFO, which is used by the audit daemon to query who issued the 
shutdown. 

It requires the placement of a hook function that gathers the information. The 
hook is after the DAC & MAC checks and before the function returns. Racing 
threads could overwrite the uid & pid - but they would have to be root and 
have policy that allows signalling the audit daemon. That should be a 
manageable risk.

The userspace component will be released later in audit 0.7.2. When it 
receives the TERM signal, it queries the kernel for shutdown information. 
When it receives it, it writes the message and exits. The message looks 
like this:

type=DAEMON msg=auditd(1114551182.000) auditd normal halt, sending pid=2650 
uid=525, auditd pid=1685

Signed-off-by: Steve Grubb <sgrubb@redhat.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

3 files changed, 38 insertions, 2 deletions

diff --git a/kernel/audit.c b/kernel/audit.c
index 9c4f1af0c794..6f344b44d3d3 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -68,7 +68,7 @@ static int	audit_failure = AUDIT_FAIL_PRINTK;
 
 /* If audit records are to be written to the netlink socket, audit_pid
  * contains the (non-zero) pid. */
-static int      audit_pid;
+int             audit_pid;
 
 /* If audit_limit is non-zero, limit the rate of sending audit records
  * to that number per second.  This prevents DoS attacks, but results in
@@ -79,6 +79,10 @@ static int	audit_rate_limit;
 static int      audit_backlog_limit = 64;
 static atomic_t audit_backlog       = ATOMIC_INIT(0);
 
+/* The identity of the user shutting down the audit system. */
+uid_t           audit_sig_uid = -1;
+pid_t           audit_sig_pid = -1;
+
 /* Records can be lost in several ways:
    0) [suppressed in audit_alloc]
    1) out of memory in audit_log_start [kmalloc of struct audit_buffer]
@@ -321,6 +325,7 @@ static int audit_netlink_ok(kernel_cap_t eff_cap, u16 msg_type)
         case AUDIT_SET:
         case AUDIT_ADD:
         case AUDIT_DEL:
+        case AUDIT_SIGNAL_INFO:
                 if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL))
                         err = -EPERM;
                 break;
@@ -344,6 +349,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
         struct audit_buffer     *ab;
         u16                     msg_type = nlh->nlmsg_type;
         uid_t                   loginuid; /* loginuid of sender */
+        struct audit_sig_info   sig_data;
 
         err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
         if (err)
@@ -419,6 +425,12 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
                 err = -EOPNOTSUPP;
 #endif
                 break;
+        case AUDIT_SIGNAL_INFO:
+                sig_data.uid = audit_sig_uid;
+                sig_data.pid = audit_sig_pid;
+                audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_SIGNAL_INFO, 
+                                0, 0, &sig_data, sizeof(sig_data));
+                break;
         default:
                 err = -EINVAL;
                 break;
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 37b3ac94bc47..f1bf66510cd3 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1056,3 +1056,22 @@ int audit_ipc_perms(unsigned long qbytes, uid_t uid, gid_t gid, mode_t mode)
         context->aux = (void *)ax;
         return 0;
 }
+
+void audit_signal_info(int sig, struct task_struct *t)
+{
+        extern pid_t audit_sig_pid;
+        extern uid_t audit_sig_uid;
+        extern int audit_pid;
+
+        if (unlikely(audit_pid && t->pid == audit_pid)) {
+                if (sig == SIGTERM || sig == SIGHUP) {
+                        struct audit_context *ctx = current->audit_context;
+                        audit_sig_pid = current->pid;
+                        if (ctx)
+                                audit_sig_uid = ctx->loginuid;
+                        else
+                                audit_sig_uid = current->uid;
+                }
+        }
+}
+
diff --git a/kernel/signal.c b/kernel/signal.c
index 8f3debc77c5b..293e189d8bc3 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -24,6 +24,7 @@
 #include <linux/ptrace.h>
 #include <linux/posix-timers.h>
 #include <linux/signal.h>
+#include <linux/audit.h>
 #include <asm/param.h>
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -658,7 +659,11 @@ static int check_kill_permission(int sig, struct siginfo *info,
             && (current->uid ^ t->suid) && (current->uid ^ t->uid)
             && !capable(CAP_KILL))
                 return error;
-        return security_task_kill(t, info, sig);
+
+        error = security_task_kill(t, info, sig);
+        if (!error)
+                audit_signal_info(sig, t); /* Let audit system see the signal */
+        return error;
 }
 
 /* forward decl */