Introduce and use secure_memzero() to erase secrets

index 95caf76..dac6f01 100644
@@ -30,7 +30,7 @@
 /* size of an array */
 #define SIZE(x) (sizeof(x)/sizeof(x[0]))
 
-/* clear an object */
+/* clear an object (may be optimized away, use secure_memzero() to erase secrets) */
 #define CLEAR(x) memset(&(x), 0, sizeof(x))
 
 #define IPV4_NETMASK_HOST 0xffffffffU

index 4d217d1..1c17b61 100644
@@ -155,7 +155,9 @@ void
 buf_clear (struct buffer *buf)
 {
   if (buf->capacity > 0)
-    memset (buf->data, 0, buf->capacity);
+    {
+      secure_memzero (buf->data, buf->capacity);
+    }
   buf->len = 0;
   buf->offset = 0;
 }

@@ -579,9 +581,7 @@ string_clear (char *str)
 {
   if (str)
     {
-      const int len = strlen (str);
-      if (len > 0)
-	memset (str, 0, len);
+      secure_memzero (str, strlen (str));
     }
 }
 

49 lines not on this page · raw message

index f153367..6fc97dd 100644
@@ -98,15 +98,13 @@ openvpn_encrypt (struct buffer *buf, struct buffer work,
       /* Do Encrypt from buf -> work */
       if (ctx->cipher)
 	{
-	  uint8_t iv_buf[OPENVPN_MAX_IV_LENGTH];
+	  uint8_t iv_buf[OPENVPN_MAX_IV_LENGTH] = {0};
 	  const int iv_size = cipher_ctx_iv_length (ctx->cipher);
 	  const cipher_kt_t *cipher_kt = cipher_ctx_get_cipher_kt (ctx->cipher);
 	  int outlen;
 
 	  if (cipher_kt_mode_cbc(cipher_kt))
 	    {
-	      CLEAR (iv_buf);
-
 	      /* generate pseudo-random IV */
 	      if (opt->flags & CO_USE_IV)
 		prng_bytes (iv_buf, iv_size);

@@ -124,7 +122,6 @@ openvpn_encrypt (struct buffer *buf, struct buffer work,
 	      ASSERT (opt->flags & CO_USE_IV);    /* IV and packet-ID required */
 	      ASSERT (opt->packet_id); /*  for this mode. */
 
-	      memset (iv_buf, 0, iv_size);
 	      buf_set_write (&b, iv_buf, iv_size);
 	      ASSERT (packet_id_write (&opt->packet_id->send, &b, true, false));
 	    }

@@ -271,14 +268,13 @@ openvpn_decrypt (struct buffer *buf, struct buffer work,
 	{
 	  const int iv_size = cipher_ctx_iv_length (ctx->cipher);
 	  const cipher_kt_t *cipher_kt = cipher_ctx_get_cipher_kt (ctx->cipher);
-	  uint8_t iv_buf[OPENVPN_MAX_IV_LENGTH];
+	  uint8_t iv_buf[OPENVPN_MAX_IV_LENGTH] = { 0 };
 	  int outlen;
 
 	  /* initialize work buffer with FRAME_HEADROOM bytes of prepend capacity */
 	  ASSERT (buf_init (&work, FRAME_HEADROOM_ADJ (frame, FRAME_HEADROOM_MARKER_DECRYPT)));
 
 	  /* use IV if user requested it */
-	  CLEAR (iv_buf);
 	  if (opt->flags & CO_USE_IV)
 	    {
 	      if (buf->len < iv_size)

@@ -828,7 +824,7 @@ get_tls_handshake_key (const struct key_type *key_type,
       init_key_ctx (&ctx->decrypt, &key2.keys[kds.in_key], &kt, OPENVPN_OP_DECRYPT,
 		    "Incoming Control Channel Authentication");
 
-      CLEAR (key2);
+      secure_memzero (&key2, sizeof (key2));
     }
   else
     {

@@ -1138,8 +1134,8 @@ write_key_file (const int nkeys, const char *filename)
       buf_printf (&out, "%s\n", fmt);
 
       /* zero memory which held key component (will be freed by GC) */
-      memset (fmt, 0, strlen(fmt));
-      CLEAR (key);
+      secure_memzero (fmt, strlen (fmt));
+      secure_memzero (&key, sizeof (key));
     }
 
   buf_printf (&out, "%s\n", static_key_foot);

index 227d2c6..42380b7 100644
@@ -2115,7 +2115,7 @@ do_init_crypto_static (struct context *c, const unsigned int flags)
 		    &c->c1.ks.key_type, OPENVPN_OP_DECRYPT, "Static Decrypt");
 
       /* Erase the temporary copy of key */
-      CLEAR (key2);
+      secure_memzero (&key2, sizeof(key2));
     }
   else
     {

index cf6fec1..d9471d1 100644
@@ -2975,7 +2975,7 @@ management_query_user_pass (struct management *man,
 	  man->connection.up_query.nocache = up->nocache; /* preserve caller's nocache setting */
 	  *up = man->connection.up_query;
 	}
-      CLEAR (man->connection.up_query);
+      secure_memzero (&man->connection.up_query, sizeof (man->connection.up_query));
     }
 
   gc_free (&gc);

index 39aa936..dc650c6 100644
@@ -1340,7 +1340,7 @@ purge_user_pass (struct user_pass *up, const bool force)
   static bool warn_shown = false;
   if (nocache || force)
     {
-      CLEAR (*up);
+      secure_memzero (up, sizeof(*up));
       up->nocache = nocache;
     }
   else if (!warn_shown)

index 3a6b4f2..79f861b 100644
@@ -3819,7 +3819,7 @@ read_inline_file (struct in_src *is, const char *close_tag, struct gc_arena *gc)
   ret = string_alloc (BSTR (&buf), gc);
   buf_clear (&buf);
   free_buf (&buf);
-  CLEAR (line);
+  secure_memzero (line, sizeof (line));
   return ret;
 }
 

@@ -3934,7 +3934,7 @@ read_config_file (struct options *options,
     {
       msg (msglevel, "In %s:%d: Maximum recursive include levels exceeded in include attempt of file %s -- probably you have a configuration file that tries to include itself.", top_file, top_line, file);
     }
-  CLEAR (line);
+  secure_memzero (line, sizeof (line));
   CLEAR (p);
 }
 

@@ -3966,7 +3966,7 @@ read_config_string (const char *prefix,
 	}
       CLEAR (p);
     }
-  CLEAR (line);
+  secure_memzero (line, sizeof (line));
 }
 
 void

index 32d0b6b..c52a0e4 100644
@@ -1427,7 +1427,7 @@ tls1_P_hash(const md_kt_t *md_kt,
     }
   hmac_ctx_cleanup(&ctx);
   hmac_ctx_cleanup(&ctx_tmp);
-  CLEAR (A1);
+  secure_memzero (A1, sizeof (A1));
 
   dmsg (D_SHOW_KEY_SOURCE, "tls1_P_hash out: %s", format_hex (out_orig, olen_orig, 0, &gc));
   gc_free (&gc);

@@ -1537,14 +1537,11 @@ generate_key_expansion (struct key_ctx_bi *key,
 			const struct session_id *server_sid,
 			bool server)
 {
-  uint8_t master[48];
-  struct key2 key2;
+  uint8_t master[48] = { 0 };
+  struct key2 key2 = { 0 };
   bool ret = false;
   int i;
 
-  CLEAR (master);
-  CLEAR (key2);
-
   /* debugging print of source key material */
   key_source2_print (key_src);
 

@@ -1608,8 +1605,8 @@ generate_key_expansion (struct key_ctx_bi *key,
   ret = true;
 
  exit:
-  CLEAR (master);
-  CLEAR (key2);
+  secure_memzero (&master, sizeof (master));
+  secure_memzero (&key2, sizeof (key2));
 
   return ret;
 }

@@ -1806,7 +1803,7 @@ key_method_1_write (struct buffer *buf, struct tls_session *session)
 
   init_key_ctx (&ks->key.encrypt, &key, &session->opt->key_type,
 		OPENVPN_OP_ENCRYPT, "Data Channel Encrypt");
-  CLEAR (key);
+  secure_memzero (&key, sizeof (key));
 
   /* send local options string */
   {

@@ -1976,7 +1973,7 @@ key_method_2_write (struct buffer *buf, struct tls_session *session)
 	    }
 	}
 		      
-      CLEAR (*ks->key_src);
+      secure_memzero (ks->key_src, sizeof (*ks->key_src));
       tls_limit_reneg_bytes (session->opt->key_type.cipher,
 			     &session->opt->renegotiate_bytes);
     }

@@ -1985,7 +1982,7 @@ key_method_2_write (struct buffer *buf, struct tls_session *session)
 
  error:
   msg (D_TLS_ERRORS, "TLS Error: Key Method #2 write failed");
-  CLEAR (*ks->key_src);
+  secure_memzero (ks->key_src, sizeof (*ks->key_src));
   return false;
 }
 

@@ -2040,13 +2037,13 @@ key_method_1_read (struct buffer *buf, struct tls_session *session)
 
   init_key_ctx (&ks->key.decrypt, &key, &session->opt->key_type,
 		OPENVPN_OP_DECRYPT, "Data Channel Decrypt");
-  CLEAR (key);
+  secure_memzero (&key, sizeof (key));
   ks->authenticated = true;
   return true;
 
  error:
   buf_clear (buf);
-  CLEAR (key);
+  secure_memzero (&key, sizeof (key));
   return false;
 }
 

@@ -2111,7 +2108,7 @@ key_method_2_read (struct buffer *buf, struct tls_multi *multi, struct tls_sessi
 
       if (!username_status || !password_status)
 	{
-	  CLEAR (*up);
+	  secure_memzero (up, sizeof(*up));
 	  if (!(session->opt->ssl_flags & SSLF_AUTH_USER_PASS_OPTIONAL))
 	    {
 	      msg (D_TLS_ERRORS, "TLS Error: Auth Username/Password was not provided by peer");

@@ -2126,7 +2123,7 @@ key_method_2_read (struct buffer *buf, struct tls_multi *multi, struct tls_sessi
 #endif
 
       verify_user_pass(up, multi, session);
-      CLEAR (*up);
+      secure_memzero (up, sizeof (*up));
     }
   else
     {

@@ -2188,14 +2185,14 @@ key_method_2_read (struct buffer *buf, struct tls_multi *multi, struct tls_sessi
 	  goto error;
 	}
 		      
-      CLEAR (*ks->key_src);
+      secure_memzero (ks->key_src, sizeof (*ks->key_src));
     }
 
   gc_free (&gc);
   return true;
 
  error:
-  CLEAR (*ks->key_src);
+  secure_memzero (ks->key_src, sizeof (*ks->key_src));
   buf_clear (buf);
   gc_free (&gc);
   return false;