diff -up openssh-7.4p1/monitor_wrap.c.audit-race openssh-7.4p1/monitor_wrap.c

--- openssh-7.4p1/monitor_wrap.c.audit-race	2016-12-23 16:35:52.694685771 +0100

+++ openssh-7.4p1/monitor_wrap.c	2016-12-23 16:35:52.697685772 +0100

@@ -1107,4 +1107,50 @@ mm_audit_destroy_sensitive_data(const ch

 	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_AUDIT_SERVER_KEY_FREE, m);

 	sshbuf_free(m);

 }

+

+int mm_forward_audit_messages(int fdin)

+{

+	u_char buf[4];

+	u_int blen, msg_len;

+	struct sshbuf *m;

+	int r, ret = 0;

+

+	debug3("%s: entering", __func__);

+	if ((m = sshbuf_new()) == NULL)

+ 		fatal("%s: sshbuf_new failed", __func__);

+	do {

+		blen = atomicio(read, fdin, buf, sizeof(buf));

+		if (blen == 0) /* closed pipe */

+			break;

+		if (blen != sizeof(buf)) {

+			error("%s: Failed to read the buffer from child", __func__);

+			ret = -1;

+			break;

+		}

+

+		msg_len = get_u32(buf);

+		if (msg_len > 256 * 1024)

+			fatal("%s: read: bad msg_len %d", __func__, msg_len);

+		sshbuf_reset(m);

+		if ((r = sshbuf_reserve(m, msg_len, NULL)) != 0)

+			fatal("%s: buffer error: %s", __func__, ssh_err(r));

+		if (atomicio(read, fdin, sshbuf_mutable_ptr(m), msg_len) != msg_len) {

+			error("%s: Failed to read the the buffer content from the child", __func__);

+			ret = -1;

+			break;

+		}

+		if (atomicio(vwrite, pmonitor->m_recvfd, buf, blen) != blen || 

+		    atomicio(vwrite, pmonitor->m_recvfd, sshbuf_mutable_ptr(m), msg_len) != msg_len) {

+			error("%s: Failed to write the message to the monitor", __func__);

+			ret = -1;

+			break;

+		}

+	} while (1);

+	sshbuf_free(m);

+	return ret;

+}

+void mm_set_monitor_pipe(int fd)

+{

+	pmonitor->m_recvfd = fd;

+}

 #endif /* SSH_AUDIT_EVENTS */

diff -up openssh-7.4p1/monitor_wrap.h.audit-race openssh-7.4p1/monitor_wrap.h

--- openssh-7.4p1/monitor_wrap.h.audit-race	2016-12-23 16:35:52.694685771 +0100

+++ openssh-7.4p1/monitor_wrap.h	2016-12-23 16:35:52.698685772 +0100

@@ -83,6 +83,8 @@ void mm_audit_unsupported_body(int);

 void mm_audit_kex_body(struct ssh *, int, char *, char *, char *, char *, pid_t, uid_t);

 void mm_audit_session_key_free_body(struct ssh *, int, pid_t, uid_t);

 void mm_audit_destroy_sensitive_data(struct ssh *, const char *, pid_t, uid_t);

+int mm_forward_audit_messages(int);

+void mm_set_monitor_pipe(int);

 #endif

 struct Session;

diff -up openssh-7.4p1/session.c.audit-race openssh-7.4p1/session.c

--- openssh-7.4p1/session.c.audit-race	2016-12-23 16:35:52.695685771 +0100

+++ openssh-7.4p1/session.c	2016-12-23 16:37:26.339730596 +0100

@@ -162,6 +162,10 @@ static Session *sessions = NULL;

 login_cap_t *lc;

 #endif

+#ifdef SSH_AUDIT_EVENTS

+int paudit[2];

+#endif

+

 static int is_child = 0;

 static int in_chroot = 0;

 static int have_dev_log = 1;

@@ -289,6 +293,8 @@ xauth_valid_string(const char *s)

 	return 1;

 }

+void child_destory_sensitive_data(struct ssh *ssh);

+

 #define USE_PIPES 1

 /*

  * This is called to fork and execute a command when we have no tty.  This

@@ -424,6 +430,8 @@ do_exec_no_pty(Session *s, const char *c

 		close(err[0]);

 #endif

+		child_destory_sensitive_data(ssh);

+

 		/* Do processing for the child (exec command etc). */

 		do_child(ssh, s, command);

 		/* NOTREACHED */

@@ -547,6 +555,9 @@ do_exec_pty(Session *s, const char *comm

 		/* Close the extra descriptor for the pseudo tty. */

 		close(ttyfd);

+		/* Do this early, so we will not block large MOTDs */

+		child_destory_sensitive_data(ssh);

+

 		/* record login, etc. similar to login(1) */

 #ifndef HAVE_OSF_SIA

 		do_login(ssh, s, command);

@@ -717,6 +728,8 @@ do_exec(Session *s, const char *command)

 	}

 	if (s->command != NULL && s->ptyfd == -1)

 		s->command_handle = PRIVSEP(audit_run_command(ssh, s->command));

+	if (pipe(paudit) < 0)

+		fatal("pipe: %s", strerror(errno));

 #endif

 	if (s->ttyfd != -1)

 		ret = do_exec_pty(ssh, s, command);

@@ -732,6 +745,20 @@ do_exec(Session *s, const char *command)

 	 */

 	sshbuf_reset(loginmsg);

+#ifdef SSH_AUDIT_EVENTS

+	close(paudit[1]);

+	if (use_privsep && ret == 0) {

+		/*

+		 * Read the audit messages from forked child and send them

+		 * back to monitor. We don't want to communicate directly,

+		 * because the messages might get mixed up.

+		 * Continue after the pipe gets closed (all messages sent).

+		 */

+		ret = mm_forward_audit_messages(paudit[0]);

+	}

+	close(paudit[0]);

+#endif /* SSH_AUDIT_EVENTS */

+

 	return ret;

 }

@@ -1538,6 +1565,34 @@ child_close_fds(void)

 	endpwent();

 }

+void

+child_destory_sensitive_data(struct ssh *ssh)

+{

+#ifdef SSH_AUDIT_EVENTS

+	int pparent = paudit[1];

+	close(paudit[0]);

+	/* Hack the monitor pipe to avoid race condition with parent */

+	if (use_privsep)

+		mm_set_monitor_pipe(pparent);

+#endif

+

+	/* remove hostkey from the child's memory */

+	destroy_sensitive_data(ssh, use_privsep);

+	/*

+	 * We can audit this, because we hacked the pipe to direct the

+	 * messages over postauth child. But this message requires answer

+	 * which we can't do using one-way pipe.

+	 */

+	packet_destroy_all(ssh, 0, 1);

+	/* XXX this will clean the rest but should not audit anymore */

+	/* packet_clear_keys(ssh); */

+

+#ifdef SSH_AUDIT_EVENTS

+	/* Notify parent that we are done */

+	close(pparent);

+#endif

+}

+

 /*

  * Performs common processing for the child, such as setting up the

  * environment, closing extra file descriptors, setting the user and group

@@ -1554,13 +1608,6 @@ do_child(Session *s, const char *command

 	sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));

-	/* remove hostkey from the child's memory */

-	destroy_sensitive_data(ssh, 1);

-	ssh_packet_clear_keys(ssh);

-	/* Don't audit this - both us and the parent would be talking to the

-	   monitor over a single socket, with no synchronization. */

-	packet_destroy_all(ssh, 0, 1);

-

 	/* Force a password change */

 	if (s->authctxt->force_pwchange) {

 		do_setusercontext(pw);