zapret/docs/wireguard/010-wg-mod.patch

Index: WireGuard-0.0.20190123/src/cookie.c
===================================================================
--- WireGuard-0.0.20190123.orig/src/cookie.c
+++ WireGuard-0.0.20190123/src/cookie.c
@@ -193,6 +193,8 @@ void wg_cookie_message_create(struct mes
 	xchacha20poly1305_encrypt(dst->encrypted_cookie, cookie, COOKIE_LEN,
 				  macs->mac1, COOKIE_LEN, dst->nonce,
 				  checker->cookie_encryption_key);
+        // MOD : randomize trash
+	dst->header.trash = gen_trash();
 }
 
 void wg_cookie_message_consume(struct message_handshake_cookie *src,
Index: WireGuard-0.0.20190123/src/messages.h
===================================================================
--- WireGuard-0.0.20190123.orig/src/messages.h
+++ WireGuard-0.0.20190123/src/messages.h
@@ -53,23 +53,41 @@ enum limits {
 	MAX_QUEUED_PACKETS = 1024 /* TODO: replace this with DQL */
 };
 
+/*
 enum message_type {
-	MESSAGE_INVALID = 0,
-	MESSAGE_HANDSHAKE_INITIATION = 1,
-	MESSAGE_HANDSHAKE_RESPONSE = 2,
-	MESSAGE_HANDSHAKE_COOKIE = 3,
-	MESSAGE_DATA = 4
+    MESSAGE_INVALID = 0,
+    MESSAGE_HANDSHAKE_INITIATION = 1,
+    MESSAGE_HANDSHAKE_RESPONSE = 2,
+    MESSAGE_HANDSHAKE_COOKIE = 3,
+    MESSAGE_DATA = 4
 };
+*/
+
+// MOD : message type
+enum message_type {
+    MESSAGE_INVALID = 0xE319CCD0,
+    MESSAGE_HANDSHAKE_INITIATION = 0x48ADE198,
+    MESSAGE_HANDSHAKE_RESPONSE = 0xFCA6A8F3,
+    MESSAGE_HANDSHAKE_COOKIE = 0x64A3BB18,
+    MESSAGE_DATA = 0x391820AA
+};
+
+// MOD : generate fast trash without true RNG
+__le32 gen_trash(void);
 
 struct message_header {
-	/* The actual layout of this that we want is:
-	 * u8 type
-	 * u8 reserved_zero[3]
-	 *
-	 * But it turns out that by encoding this as little endian,
-	 * we achieve the same thing, and it makes checking faster.
-	 */
-	__le32 type;
+    /* The actual layout of this that we want is:
+     * u8 type
+     * u8 reserved_zero[3]
+     *
+     * But it turns out that by encoding this as little endian,
+     * we achieve the same thing, and it makes checking faster.
+     */
+
+    // MOD : trash field to change message size and add 4 byte offset to all fields
+    __le32 trash;
+
+    __le32 type;
 };
 
 struct message_macs {
Index: WireGuard-0.0.20190123/src/noise.c
===================================================================
--- WireGuard-0.0.20190123.orig/src/noise.c
+++ WireGuard-0.0.20190123/src/noise.c
@@ -17,6 +17,24 @@
 #include <linux/highmem.h>
 #include <crypto/algapi.h>
 
+
+// MOD : trash generator
+__le32 gtrash = 0;
+__le32 gen_trash(void)
+{
+    if (gtrash)
+	gtrash = gtrash*1103515243 + 12345;
+    else
+	// first value is true random
+	get_random_bytes_wait(&gtrash, sizeof(gtrash));
+    return gtrash;
+}
+
 /* This implements Noise_IKpsk2:
  *
  * <- s
@@ -515,6 +533,10 @@ wg_noise_handshake_create_initiation(str
 		&handshake->entry);
 
 	handshake->state = HANDSHAKE_CREATED_INITIATION;
+
+	// MOD : randomize trash
+        dst->header.trash = gen_trash();
+
 	ret = true;
 
 out:
@@ -655,6 +677,10 @@ bool wg_noise_handshake_create_response(
 		&handshake->entry);
 
 	handshake->state = HANDSHAKE_CREATED_RESPONSE;
+
+        // MOD : randomize trash
+        dst->header.trash = gen_trash();
+
 	ret = true;
 
 out:
Index: WireGuard-0.0.20190123/src/send.c
===================================================================
--- WireGuard-0.0.20190123.orig/src/send.c
+++ WireGuard-0.0.20190123/src/send.c
@@ -200,6 +200,10 @@ static bool encrypt_packet(struct sk_buf
 	header->header.type = cpu_to_le32(MESSAGE_DATA);
 	header->key_idx = keypair->remote_index;
 	header->counter = cpu_to_le64(PACKET_CB(skb)->nonce);
+
+        // MOD : randomize trash
+	header->header.trash = gen_trash();
+
 	pskb_put(skb, trailer, trailer_len);
 
 	/* Now we can encrypt the scattergather segments */