From daab0a9fa8ff4f40e8a34707db0ac156d49fbfcb Mon Sep 17 00:00:00 2001
From: David Sommerseth <davids@openvpn.net>
Date: Tue, 28 Mar 2017 22:53:46 +0200
Subject: [PATCH] auth-token: Ensure tokens are always wiped on de-auth

If tls_deauthenticate() was called, it could in some scenarios leave the
authentication token for a session in memory.  This change just ensures
auth-tokens are always wiped as soon as a TLS session is considered
broken.

Signed-off-by: David Sommerseth <davids@openvpn.net>

Acked-by: Steffan Karger <steffan@karger.me>
Message-Id: <20170328205346.18844-1-davids@openvpn.net>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg14344.html
Signed-off-by: David Sommerseth <davids@openvpn.net>
---
 src/openvpn/ssl_verify.c | 47 +++++++++++++++++++++++++++--------------------
 1 file changed, 27 insertions(+), 20 deletions(-)

Index: openvpn-2.4.0/src/openvpn/ssl_verify.c
===================================================================
--- openvpn-2.4.0.orig/src/openvpn/ssl_verify.c
+++ openvpn-2.4.0/src/openvpn/ssl_verify.c
@@ -80,6 +80,28 @@ setenv_untrusted(struct tls_session *ses
     setenv_link_socket_actual(session->opt->es, "untrusted", &session->untrusted_addr, SA_IP_PORT);
 }
 
+
+/**
+ *  Wipes the authentication token out of the memory, frees and cleans up related buffers and flags
+ *
+ *  @param multi  Pointer to a multi object holding the auth_token variables
+ */
+static void
+wipe_auth_token(struct tls_multi *multi)
+{
+    if(multi)
+    {
+        if (multi->auth_token)
+        {
+            secure_memzero(multi->auth_token, AUTH_TOKEN_SIZE);
+            free(multi->auth_token);
+        }
+        multi->auth_token = NULL;
+        multi->auth_token_sent = false;
+    }
+}
+
+
 /*
  * Remove authenticated state from all sessions in the given tunnel
  */
@@ -88,10 +110,14 @@ tls_deauthenticate(struct tls_multi *mul
 {
     if (multi)
     {
-        int i, j;
-        for (i = 0; i < TM_SIZE; ++i)
-            for (j = 0; j < KS_SIZE; ++j)
+        wipe_auth_token(multi);
+        for (int i = 0; i < TM_SIZE; ++i)
+        {
+            for (int j = 0; j < KS_SIZE; ++j)
+            {
                 multi->session[i].key[j].authenticated = false;
+            }
+        }
     }
 }
 
@@ -1213,21 +1239,6 @@ verify_user_pass_management(struct tls_s
 }
 #endif /* ifdef MANAGEMENT_DEF_AUTH */
 
-/**
- *  Wipes the authentication token out of the memory, frees and cleans up related buffers and flags
- *
- *  @param multi  Pointer to a multi object holding the auth_token variables
- */
-static void
-wipe_auth_token(struct tls_multi *multi)
-{
-    secure_memzero(multi->auth_token, AUTH_TOKEN_SIZE);
-    free(multi->auth_token);
-    multi->auth_token = NULL;
-    multi->auth_token_sent = false;
-}
-
-
 /*
  * Main username/password verification entry point
  */
@@ -1279,7 +1290,7 @@ verify_user_pass(struct user_pass *up, s
         /* Ensure that the username has not changed */
         if (!tls_lock_username(multi, up->username))
         {
-            wipe_auth_token(multi);
+            /* auth-token cleared in tls_lock_username() on failure */
             ks->authenticated = false;
             goto done;
         }
@@ -1300,7 +1311,6 @@ verify_user_pass(struct user_pass *up, s
         if (memcmp_constant_time(multi->auth_token, up->password,
                                  strlen(multi->auth_token)) != 0)
         {
-            wipe_auth_token(multi);
             ks->authenticated = false;
             tls_deauthenticate(multi);
 
@@ -1472,6 +1482,7 @@ verify_final_auth_checks(struct tls_mult
         if (!cn || !strcmp(cn, CCD_DEFAULT) || !test_file(path))
         {
             ks->authenticated = false;
+            wipe_auth_token(multi);
             msg(D_TLS_ERRORS, "TLS Auth Error: --client-config-dir authentication failed for common name '%s' file='%s'",
                 session->common_name,
                 path ? path : "UNDEF");