File openssh-7.6p1-audit_race_condition.patch of Package openssh.31918
diff --git a/monitor_wrap.c b/monitor_wrap.c
index aaf13de..8e14d15 100644
--- a/monitor_wrap.c
+++ b/monitor_wrap.c
@@ -1173,4 +1173,51 @@ mm_audit_destroy_sensitive_data(const char *fp, pid_t pid, uid_t uid)
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 ret = 0;
+
+ debug3("%s: entering", __func__);
+ m = sshbuf_new();
+ do {
+ int r;
+
+ 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 conent 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 messag 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 --git a/monitor_wrap.h b/monitor_wrap.h
index 218b9d5..289ecbb 100644
--- a/monitor_wrap.h
+++ b/monitor_wrap.h
@@ -86,6 +86,8 @@ 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;
diff --git a/session.c b/session.c
index 9b72259..29bd28d 100644
--- a/session.c
+++ b/session.c
@@ -161,6 +161,10 @@ 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;
@@ -762,6 +766,8 @@ do_exec(struct ssh *ssh, Session *s, const char *command)
}
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);
@@ -777,6 +783,20 @@ do_exec(struct ssh *ssh, 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;
}
@@ -1564,13 +1584,28 @@ do_child(struct ssh *ssh, Session *s, const char *command)
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);