Fix broken async push with NCP is used

With NCP and deferred auth, we perform cipher negotiation and generate
data channel keys on incoming push request, assuming that auth succeeded.

With async push, when auth succeeds in between push requests, we send
push reply immediately.

The code which generates data channel keys is only called on handling
incoming push requests (incoming_push_message). It might not be called
with NCP, deferred auth and async push, because on incoming push request,
auth might not be complete yet. When auth is complete in between push
requests, push reply is sent and it is assumed that connection is
established. However, since data channel keys are not generated on the
server side, connection doesn't work.

Fix by adding a call to generate data channel keys when async push is
triggered.

Also, all the "session->key[KS_PRIMARY].crypto_options.key_ctx_bi.initialized"
checks have been moved into tls_session_update_crypto_params(), which
is just reducing duplicate code, no actual code change (*all* callers
had this pre-check).

Trac: #1259

Reported-by: smaxfield@duosecurity.com
Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20200313165913.12682-1-lstipakov@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg19553.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

5 files changed, 36 insertions, 11 deletions

diff --git a/src/openvpn/init.c b/src/openvpn/init.c
index 824b666..b3096dc 100644
--- a/src/openvpn/init.c
+++ b/src/openvpn/init.c
@@ -2343,10 +2343,8 @@ do_deferred_options(struct context *c, const unsigned int found)
         }
 #endif
 
-        /* Do not regenerate keys if server sends an extra push reply */
-        if (!session->key[KS_PRIMARY].crypto_options.key_ctx_bi.initialized
-            && !tls_session_update_crypto_params(session, &c->options, &c->c2.frame,
-                                                 frame_fragment))
+        if (!tls_session_update_crypto_params(session, &c->options, &c->c2.frame,
+                                              frame_fragment))
         {
             msg(D_TLS_ERRORS, "OPTIONS ERROR: failed to import crypto options");
             return false;
diff --git a/src/openvpn/multi.c b/src/openvpn/multi.c
index da0aeeb..b42bcec 100644
--- a/src/openvpn/multi.c
+++ b/src/openvpn/multi.c
@@ -2137,8 +2137,30 @@ multi_process_file_closed(struct multi_context *m, const unsigned int mpp_flags)
         {
             if (mi)
             {
-                /* continue authentication and send push_reply */
+                /* continue authentication, perform NCP negotiation and send push_reply */
                 multi_process_post(m, mi, mpp_flags);
+
+                /* With NCP and deferred authentication, we perform cipher negotiation and
+                 * data channel keys generation on incoming push request, assuming that auth
+                 * succeeded. When auth succeeds in between push requests and async push is used,
+                 * we send push reply immediately. Above multi_process_post() call performs
+                 * NCP negotiation and here we do keys generation. */
+
+                struct context *c = &mi->context;
+                struct frame *frame_fragment = NULL;
+#ifdef ENABLE_FRAGMENT
+                if (c->options.ce.fragment)
+                {
+                    frame_fragment = &c->c2.frame_fragment;
+                }
+#endif
+                struct tls_session *session = &c->c2.tls_multi->session[TM_ACTIVE];
+                if (!tls_session_update_crypto_params(session, &c->options,
+                                                      &c->c2.frame, frame_fragment))
+                {
+                    msg(D_TLS_ERRORS, "TLS Error: initializing data channel failed");
+                    register_signal(c, SIGUSR1, "init-data-channel-failed");
+                }
             }
             else
             {
diff --git a/src/openvpn/push.c b/src/openvpn/push.c
index 71f22e9..aef00d3 100644
--- a/src/openvpn/push.c
+++ b/src/openvpn/push.c
@@ -298,10 +298,8 @@ incoming_push_message(struct context *c, const struct buffer *buffer)
             }
 #endif
             struct tls_session *session = &c->c2.tls_multi->session[TM_ACTIVE];
-            /* Do not regenerate keys if client send a second push request */
-            if (!session->key[KS_PRIMARY].crypto_options.key_ctx_bi.initialized
-                && !tls_session_update_crypto_params(session, &c->options,
-                                                     &c->c2.frame, frame_fragment))
+            if (!tls_session_update_crypto_params(session, &c->options,
+                                                  &c->c2.frame, frame_fragment))
             {
                 msg(D_TLS_ERRORS, "TLS Error: initializing data channel failed");
                 goto error;
diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c
index e21279f..56d0576 100644
--- a/src/openvpn/ssl.c
+++ b/src/openvpn/ssl.c
@@ -1956,6 +1956,12 @@ tls_session_update_crypto_params(struct tls_session *session,
                                  struct options *options, struct frame *frame,
                                  struct frame *frame_fragment)
 {
+    if (session->key[KS_PRIMARY].crypto_options.key_ctx_bi.initialized)
+    {
+        /* keys already generated, nothing to do */
+        return true;
+    }
+
     if (!session->opt->server
         && 0 != strcmp(options->ciphername, session->opt->config_ciphername)
         && !tls_item_in_cipher_list(options->ciphername, options->ncp_ciphers))
diff --git a/src/openvpn/ssl.h b/src/openvpn/ssl.h
index 3449d91..f0a8ef5 100644
--- a/src/openvpn/ssl.h
+++ b/src/openvpn/ssl.h
@@ -474,7 +474,8 @@ void tls_update_remote_addr(struct tls_multi *multi,
 
 /**
  * Update TLS session crypto parameters (cipher and auth) and derive data
- * channel keys based on the supplied options.
+ * channel keys based on the supplied options. Does nothing if keys are already
+ * generated.
  *
  * @param session         The TLS session to update.
  * @param options         The options to use when updating session.
@@ -482,7 +483,7 @@ void tls_update_remote_addr(struct tls_multi *multi,
  *                        adjusted based on the selected cipher/auth).
  * @param frame_fragment  The fragment frame options.
  *
- * @return true if updating succeeded, false otherwise.
+ * @return true if updating succeeded or keys are already generated, false otherwise.
  */
 bool tls_session_update_crypto_params(struct tls_session *session,
                                       struct options *options,