File openssh-7.6p1-audit_race_condition.patch of Package openssh.10835

Index: openssh-7.6p1/monitor_wrap.c
===================================================================
--- openssh-7.6p1/monitor_wrap.c
+++ openssh-7.6p1/monitor_wrap.c
@@ -1103,4 +1103,48 @@ mm_audit_destroy_sensitive_data(const ch
 	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_AUDIT_SERVER_KEY_FREE, &m);
 	buffer_free(&m);
 }
+
+int mm_forward_audit_messages(int fdin)
+{
+	u_char buf[4];
+	u_int blen, msg_len;
+	Buffer m;
+	int ret = 0;
+
+	debug3("%s: entering", __func__);
+	buffer_init(&m);
+	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);
+		buffer_clear(&m);
+		buffer_append_space(&m, msg_len);
+		if (atomicio(read, fdin, buffer_ptr(&m), msg_len) != msg_len) {
+			error("%s: Failed to read the the buffer conent from the child", __func__);
+			ret = -1;
+			break;
+		}
+		if (atomicio(vwrite, pmonitor->m_recvfd, buf, blen) != blen || 
+		    atomicio(vwrite, pmonitor->m_recvfd, buffer_ptr(&m), msg_len) != msg_len) {
+			error("%s: Failed to write the messag to the monitor", __func__);
+			ret = -1;
+			break;
+		}
+	} while (1);
+	buffer_free(&m);
+	return ret;
+}
+void mm_set_monitor_pipe(int fd)
+{
+	pmonitor->m_recvfd = fd;
+}
 #endif /* SSH_AUDIT_EVENTS */
Index: openssh-7.6p1/monitor_wrap.h
===================================================================
--- openssh-7.6p1/monitor_wrap.h
+++ openssh-7.6p1/monitor_wrap.h
@@ -83,6 +83,8 @@ void mm_audit_unsupported_body(int);
 void mm_audit_kex_body(int, char *, char *, char *, char *, pid_t, uid_t);
 void mm_audit_session_key_free_body(int, pid_t, uid_t);
 void mm_audit_destroy_sensitive_data(const char *, pid_t, uid_t);
+int mm_forward_audit_messages(int);
+void mm_set_monitor_pipe(int);
 #endif
 
 struct Session;
Index: openssh-7.6p1/session.c
===================================================================
--- openssh-7.6p1/session.c
+++ openssh-7.6p1/session.c
@@ -158,6 +158,10 @@ 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;
 
@@ -716,6 +720,8 @@ do_exec(struct ssh *ssh, Session *s, con
 	}
 	if (s->command != NULL && s->ptyfd == -1)
 		s->command_handle = PRIVSEP(audit_run_command(s->command));
+	if (pipe(paudit) < 0)
+		fatal("pipe: %s", strerror(errno));
 #endif
 	if (s->ttyfd != -1)
 		ret = do_exec_pty(ssh, s, command);
@@ -731,6 +737,20 @@ do_exec(struct ssh *ssh, Session *s, con
 	 */
 	buffer_clear(&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;
 }
 
@@ -1494,13 +1514,28 @@ do_child(struct ssh *ssh, Session *s, co
 	struct passwd *pw = s->pw;
 	int r = 0;
 
+#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(1);
-	packet_clear_keys();
-	/* Don't audit this - both us and the parent would be talking to the
-	   monitor over a single socket, with no synchronization. */
+	destroy_sensitive_data(use_privsep);
+	/*
+	 * We can audit this, because wer 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(0, 1);
 
+#ifdef SSH_AUDIT_EVENTS
+	/* Notify parent that we are done */
+	close(pparent);
+#endif
+
 	/* Force a password change */
 	if (s->authctxt->force_pwchange) {
 		do_setusercontext(pw);