Add Complete XOR Patch Functionality (#255)

Co-authored-by: Davide De Rosa <keeshux@gmail.com>

.github/workflows/test.yml

@@ -6,12 +6,18 @@ on:
       - "master"
     paths-ignore:
       - "*.md"
+  pull_request:
+    types: [ opened, synchronize ]
+
+concurrency:
+  group: ${{ github.ref }}
+  cancel-in-progress: ${{ github.ref != 'refs/heads/master' }}
 
 jobs:
   run_tests:
     name: Run tests
     runs-on: macos-12
-    timeout-minutes: 10
+    timeout-minutes: 5
     steps:
       - uses: actions/checkout@v2
       - uses: maxim-lobanov/setup-xcode@v1

Package.resolved

@@ -24,7 +24,7 @@
         "repositoryURL": "https://github.com/passepartoutvpn/wireguard-apple",
         "state": {
           "branch": null,
-          "revision": "b4f74b7bcba9004a1852e615298f9cbc68fb7f67",
+          "revision": "d3b8f1ac6f3361d69bd3daf8aee3c43012c6ec0b",
           "version": "1.0.16"
         }
       }

Package.swift

@@ -161,6 +161,11 @@ let package = Package(
             name: "TunnelKitCoreTests",
             dependencies: [
                 "TunnelKitCore"
+            ],
+            exclude: [
+                "RandomTests.swift",
+                "RawPerformanceTests.swift",
+                "RoutingTests.swift"
             ]),
         .testTarget(
             name: "TunnelKitOpenVPNTests",
@@ -169,6 +174,10 @@ let package = Package(
                 "TunnelKitOpenVPNAppExtension",
                 "TunnelKitLZO"
             ],
+            exclude: [
+                "DataPathPerformanceTests.swift",
+                "EncryptionPerformanceTests.swift"
+            ],
             resources: [
                 .process("Resources")
             ]),

README.md

@@ -46,10 +46,20 @@ TunnelKit can parse .ovpn configuration files. Below are a few details worth men
 
 #### Non-standard
 
-- Single-byte XOR masking
+- XOR-patch functionality:
-    - Via `--scramble xormask <character>`
+    - Multi-byte XOR Masking
-    - XOR all incoming and outgoing bytes by the ASCII value of the character argument
+        - Via `--scramble xormask <passphrase>`
-    - See [Tunnelblick website][about-tunnelblick-xor] for more details
+        - XOR all incoming and outgoing bytes by the passphrase given
+    - XOR Position Masking
+        - Via `--scramble xorptrpos`
+        - XOR all bytes by their position in the array
+    - Packet Reverse Scramble
+        - Via `--scramble reverse`
+        - Keeps the first byte and reverses the rest of the array
+    - XOR Scramble Obfuscate
+        - Via `--scramble obfuscate <passphrase>`
+        - Performs a combination of the three above (specifically `xormask <passphrase>` -> `xorptrpos` -> `reverse` -> `xorptrpos` for reading, and the opposite for writing) 
+    - See [Tunnelblick website][about-tunnelblick-xor] for more details (Patch was written in accordance with Tunnelblick's patch for compatibility)
 
 #### Unsupported
 
@@ -221,6 +231,7 @@ A custom TunnelKit license, e.g. for use in proprietary software, may be negotia
 - [SURFnet][ppl-surfnet]
 - [SwiftyBeaver][dep-swiftybeaver-repo] - Copyright (c) 2015 Sebastian Kreutzberger
 - [XMB5][ppl-xmb5] for the [XOR patch][ppl-xmb5-xor] - Copyright (c) 2020 Sam Foxman
+- [tmthecoder][ppl-tmthecoder] for the complete [XOR patch][ppl-tmthecoder-xor] - Copyright (c) 2022 Tejas Mehta
 - [eduVPN][ppl-eduvpn] for the convenient WireGuardKitGo script
 
 ### OpenVPN
@@ -264,6 +275,8 @@ Website: [passepartoutvpn.app][about-website]
 [ppl-surfnet]: https://www.surf.nl/en/about-surf/subsidiaries/surfnet
 [ppl-xmb5]: https://github.com/XMB5
 [ppl-xmb5-xor]: https://github.com/passepartoutvpn/tunnelkit/pull/170
+[ppl-tmthecoder]: https://github.com/tmthecoder
+[ppl-tmthecoder-xor]: https://github.com/passepartoutvpn/tunnelkit/pull/255
 [ppl-eduvpn]: https://github.com/eduvpn/apple
 [about-tunnelblick-xor]: https://tunnelblick.net/cOpenvpn_xorpatch.html
 [about-pr-bitcode]: https://github.com/passepartoutvpn/tunnelkit/issues/51

Sources/CTunnelKitOpenVPNCore/include/XORMethodNative.h

@@ -0,0 +1,34 @@
+//
+//  XORMethodNative.h
+//  TunnelKit
+//
+//  Created by Davide De Rosa on 11/4/22.
+//  Copyright (c) 2022 Davide De Rosa. All rights reserved.
+//
+//  https://github.com/passepartoutvpn
+//
+//  This file is part of TunnelKit.
+//
+//  TunnelKit is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation, either version 3 of the License, or
+//  (at your option) any later version.
+//
+//  TunnelKit is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//  GNU General Public License for more details.
+//
+//  You should have received a copy of the GNU General Public License
+//  along with TunnelKit.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+#import <Foundation/Foundation.h>
+
+typedef NS_ENUM(NSInteger, XORMethodNative) {
+    XORMethodNativeNone,
+    XORMethodNativeMask,
+    XORMethodNativePtrPos,
+    XORMethodNativeReverse,
+    XORMethodNativeObfuscate
+};

Sources/CTunnelKitOpenVPNProtocol/PacketStream.m

@@ -24,23 +24,16 @@
 //
 
 #import "PacketStream.h"
+#import "XOR.h"
 
 static const NSInteger PacketStreamHeaderLength = sizeof(uint16_t);
 
 @implementation PacketStream
 
-+ (void)memcpyXor:(uint8_t *)dst src:(NSData *)src xorMask:(uint8_t)xorMask
++ (NSArray<NSData *> *)packetsFromInboundStream:(NSData *)stream
-{
+                                          until:(NSInteger *)until
-    if (xorMask != 0) {
+                                      xorMethod:(XORMethodNative)xorMethod
-        for (int i = 0; i < src.length; ++i) {
+                                        xorMask:(NSData *)xorMask
-            dst[i] = ((uint8_t *)(src.bytes))[i] ^ xorMask;
-        }
-        return;
-    }
-    memcpy(dst, src.bytes, src.length);
-}
-
-+ (NSArray<NSData *> *)packetsFromStream:(NSData *)stream until:(NSInteger *)until xorMask:(uint8_t)xorMask
 {
     NSInteger ni = 0;
     NSMutableArray<NSData *> *parsed = [[NSMutableArray alloc] init];
@@ -54,11 +47,7 @@ static const NSInteger PacketStreamHeaderLength = sizeof(uint16_t);
         }
         NSData *packet = [stream subdataWithRange:NSMakeRange(start, packlen)];
         uint8_t* packetBytes = (uint8_t*) packet.bytes;
-        if (xorMask != 0) {
+        xor_memcpy(packetBytes, packet, xorMethod, xorMask, false);
-            for (int i = 0; i < packet.length; i++) {
-                packetBytes[i] ^= xorMask;
-            }
-        }
         [parsed addObject:packet];
         ni = end;
     }
@@ -68,19 +57,23 @@ static const NSInteger PacketStreamHeaderLength = sizeof(uint16_t);
     return parsed;
 }
 
-+ (NSData *)streamFromPacket:(NSData *)packet xorMask:(uint8_t)xorMask
++ (NSData *)outboundStreamFromPacket:(NSData *)packet
+                           xorMethod:(XORMethodNative)xorMethod
+                             xorMask:(NSData *)xorMask
 {
     NSMutableData *raw = [[NSMutableData alloc] initWithLength:(PacketStreamHeaderLength + packet.length)];
 
     uint8_t *ptr = raw.mutableBytes;
     *(uint16_t *)ptr = CFSwapInt16HostToBig(packet.length);
     ptr += PacketStreamHeaderLength;
-    [PacketStream memcpyXor:ptr src:packet xorMask:xorMask];
+    xor_memcpy(ptr, packet, xorMethod, xorMask, true);
     
     return raw;
 }
 
-+ (NSData *)streamFromPackets:(NSArray<NSData *> *)packets xorMask:(uint8_t)xorMask
++ (NSData *)outboundStreamFromPackets:(NSArray<NSData *> *)packets
+                            xorMethod:(XORMethodNative)xorMethod
+                              xorMask:(NSData *)xorMask
 {
     NSInteger streamLength = 0;
     for (NSData *p in packets) {
@@ -92,7 +85,7 @@ static const NSInteger PacketStreamHeaderLength = sizeof(uint16_t);
     for (NSData *packet in packets) {
         *(uint16_t *)ptr = CFSwapInt16HostToBig(packet.length);
         ptr += PacketStreamHeaderLength;
-        [PacketStream memcpyXor:ptr src:packet xorMask:xorMask];
+        xor_memcpy(ptr, packet, xorMethod, xorMask, true);
         ptr += packet.length;
     }
     return raw;

Sources/CTunnelKitOpenVPNProtocol/include/PacketStream.h

@@ -24,14 +24,24 @@
 //
 
 #import <Foundation/Foundation.h>
+#import "XORMethodNative.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
 @interface PacketStream : NSObject
 
-+ (NSArray<NSData *> *)packetsFromStream:(NSData *)stream until:(NSInteger *)until xorMask:(uint8_t)xorMask;
++ (NSArray<NSData *> *)packetsFromInboundStream:(NSData *)stream
-+ (NSData *)streamFromPacket:(NSData *)packet xorMask:(uint8_t)xorMask;
+                                          until:(NSInteger *)until
-+ (NSData *)streamFromPackets:(NSArray<NSData *> *)packets xorMask:(uint8_t)xorMask;
+                                      xorMethod:(XORMethodNative)xorMethod
+                                        xorMask:(nullable NSData *)xorMask;
+
++ (NSData *)outboundStreamFromPacket:(NSData *)packet
+                           xorMethod:(XORMethodNative)xorMethod
+                             xorMask:(nullable NSData *)xorMask;
+
++ (NSData *)outboundStreamFromPackets:(NSArray<NSData *> *)packets
+                            xorMethod:(XORMethodNative)xorMethod
+                              xorMask:(nullable NSData *)xorMask;
 
 @end
 

Sources/CTunnelKitOpenVPNProtocol/include/XOR.h

@@ -0,0 +1,99 @@
+//
+//  XOR.h
+//  TunnelKit
+//
+//  Created by Tejas Mehta on 5/24/22.
+//  Copyright (c) 2022 Davide De Rosa. All rights reserved.
+//
+//  https://github.com/passepartoutvpn
+//
+//  This file is part of TunnelKit.
+//
+//  TunnelKit is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation, either version 3 of the License, or
+//  (at your option) any later version.
+//
+//  TunnelKit is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//  GNU General Public License for more details.
+//
+//  You should have received a copy of the GNU General Public License
+//  along with TunnelKit.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+#import <Foundation/Foundation.h>
+#import "XORMethodNative.h"
+
+static inline void xor_mask(uint8_t *dst, const uint8_t *src, NSData *xorMask, size_t length)
+{
+    if (xorMask.length > 0) {
+        for (size_t i = 0; i < length; ++i) {
+            dst[i] = src[i] ^ ((uint8_t *)(xorMask.bytes))[i % xorMask.length];
+        }
+        return;
+    }
+    memcpy(dst, src, length);
+}
+
+static inline void xor_ptrpos(uint8_t *dst, const uint8_t *src, size_t length)
+{
+    for (size_t i = 0; i < length; ++i) {
+        dst[i] = src[i] ^ (i + 1);
+    }
+}
+
+static inline void xor_reverse(uint8_t *dst, const uint8_t *src, size_t length)
+{
+    size_t start = 1;
+    size_t end = length - 1;
+    uint8_t temp = 0;
+    dst[0] = src[0];
+    while (start < end) {
+        temp = src[start];
+        dst[start] = src[end];
+        dst[end] = temp;
+        start++;
+        end--;
+    }
+    if (start == end) {
+        dst[start] = src[start];
+    }
+}
+
+static inline void xor_memcpy(uint8_t *dst, NSData *src, XORMethodNative method, NSData *mask, BOOL outbound)
+{
+    const uint8_t *source = (uint8_t *)src.bytes;
+    switch (method) {
+        case XORMethodNativeNone:
+            memcpy(dst, source, src.length);
+            break;
+
+        case XORMethodNativeMask:
+            xor_mask(dst, source, mask, src.length);
+            break;
+
+        case XORMethodNativePtrPos:
+            xor_ptrpos(dst, source, src.length);
+            break;
+
+        case XORMethodNativeReverse:
+            xor_reverse(dst, source, src.length);
+            break;
+
+        case XORMethodNativeObfuscate:
+            if (outbound) {
+                xor_ptrpos(dst, source, src.length);
+                xor_reverse(dst, dst, src.length);
+                xor_ptrpos(dst, dst, src.length);
+                xor_mask(dst, dst, mask, src.length);
+            } else {
+                xor_mask(dst, source, mask, src.length);
+                xor_ptrpos(dst, dst, src.length);
+                xor_reverse(dst, dst, src.length);
+                xor_ptrpos(dst, dst, src.length);
+            }
+            break;
+    }
+}

Sources/TunnelKitAppExtension/LinkProducer.swift

@@ -32,7 +32,8 @@ public protocol LinkProducer {
     /**
      Returns a `LinkInterface`.
  
-     - Parameter xorMask: The XOR mask.
+     - Parameter userObject: Optional user data.
+     - Returns: A  generic `LinkInterface`.
      **/
-    func link(xorMask: UInt8?) -> LinkInterface
+    func link(userObject: Any?) -> LinkInterface
 }

Sources/TunnelKitCore/LinkInterface.swift

@@ -50,7 +50,4 @@ public protocol LinkInterface: IOInterface {
 
     /// The number of packets that this interface is able to bufferize.
     var packetBufferSize: Int { get }
-    
-    /// A byte to xor all packet payloads with.
-    var xorMask: UInt8 { get }
 }

Sources/TunnelKitOpenVPNAppExtension/NETCPLink.swift

@@ -27,6 +27,7 @@ import Foundation
 import NetworkExtension
 import TunnelKitCore
 import TunnelKitAppExtension
+import TunnelKitOpenVPNCore
 import CTunnelKitOpenVPNProtocol
 
 class NETCPLink: LinkInterface {
@@ -34,12 +35,15 @@ class NETCPLink: LinkInterface {
     
     private let maxPacketSize: Int
 
-    let xorMask: UInt8
+    private let xorMethod: OpenVPN.XORMethod?
 
-    init(impl: NWTCPConnection, maxPacketSize: Int? = nil, xorMask: UInt8?) {
+    private let xorMask: Data?
+
+    init(impl: NWTCPConnection, maxPacketSize: Int? = nil, xorMethod: OpenVPN.XORMethod?) {
         self.impl = impl
         self.maxPacketSize = maxPacketSize ?? (512 * 1024)
-        self.xorMask = xorMask ?? 0
+        self.xorMethod = xorMethod
+        xorMask = xorMethod?.mask
     }
     
     // MARK: LinkInterface
@@ -81,7 +85,12 @@ class NETCPLink: LinkInterface {
                 var newBuffer = buffer
                 newBuffer.append(contentsOf: data)
                 var until = 0
-                let packets = PacketStream.packets(fromStream: newBuffer, until: &until, xorMask: self.xorMask)
+                let packets = PacketStream.packets(
+                    fromInboundStream: newBuffer,
+                    until: &until,
+                    xorMethod: self.xorMethod?.native ?? .none,
+                    xorMask: self.xorMask
+                )
                 newBuffer = newBuffer.subdata(in: until..<newBuffer.count)
                 self.loopReadPackets(queue, newBuffer, handler)
                 
@@ -91,14 +100,22 @@ class NETCPLink: LinkInterface {
     }
     
     func writePacket(_ packet: Data, completionHandler: ((Error?) -> Void)?) {
-        let stream = PacketStream.stream(fromPacket: packet, xorMask: xorMask)
+        let stream = PacketStream.outboundStream(
+            fromPacket: packet,
+            xorMethod: xorMethod?.native ?? .none,
+            xorMask: xorMask
+        )
         impl.write(stream) { (error) in
             completionHandler?(error)
         }
     }
     
     func writePackets(_ packets: [Data], completionHandler: ((Error?) -> Void)?) {
-        let stream = PacketStream.stream(fromPackets: packets, xorMask: xorMask)
+        let stream = PacketStream.outboundStream(
+            fromPackets: packets,
+            xorMethod: xorMethod?.native ?? .none,
+            xorMask: xorMask
+        )
         impl.write(stream) { (error) in
             completionHandler?(error)
         }
@@ -106,7 +123,8 @@ class NETCPLink: LinkInterface {
 }
 
 extension NETCPSocket: LinkProducer {
-    public func link(xorMask: UInt8?) -> LinkInterface {
+    public func link(userObject: Any?) -> LinkInterface {
-        return NETCPLink(impl: impl, maxPacketSize: nil, xorMask: xorMask)
+        let xorMethod = userObject as? OpenVPN.XORMethod
+        return NETCPLink(impl: impl, maxPacketSize: nil, xorMethod: xorMethod)
     }
 }

Sources/TunnelKitOpenVPNAppExtension/NEUDPLink.swift

@@ -27,18 +27,20 @@ import Foundation
 import NetworkExtension
 import TunnelKitCore
 import TunnelKitAppExtension
+import TunnelKitOpenVPNCore
+import TunnelKitOpenVPNProtocol
 
 class NEUDPLink: LinkInterface {
     private let impl: NWUDPSession
     
     private let maxDatagrams: Int
     
-    let xorMask: UInt8
+    private let xor: XORProcessor
 
-    init(impl: NWUDPSession, maxDatagrams: Int? = nil, xorMask: UInt8?) {
+    init(impl: NWUDPSession, maxDatagrams: Int? = nil, xorMethod: OpenVPN.XORMethod?) {
         self.impl = impl
         self.maxDatagrams = maxDatagrams ?? 200
-        self.xorMask = xorMask ?? 0
+        xor = XORProcessor(method: xorMethod)
     }
     
     // MARK: LinkInterface
@@ -68,12 +70,8 @@ class NEUDPLink: LinkInterface {
                 return
             }
             var packetsToUse: [Data]?
-            if let packets = packets, self.xorMask != 0 {
+            if let packets = packets {
-                packetsToUse = packets.map { packet in
+                packetsToUse = self.xor.processPackets(packets, outbound: false)
-                    Data(bytes: packet.map { $0 ^ self.xorMask }, count: packet.count)
-                }
-            } else {
-                packetsToUse = packets
             }
             queue.sync {
                 handler(packetsToUse, error)
@@ -82,26 +80,14 @@ class NEUDPLink: LinkInterface {
     }
     
     func writePacket(_ packet: Data, completionHandler: ((Error?) -> Void)?) {
-        var dataToUse: Data
+        let dataToUse = xor.processPacket(packet, outbound: true)
-        if xorMask != 0 {
-            dataToUse = Data(bytes: packet.map { $0 ^ xorMask }, count: packet.count)
-        } else {
-            dataToUse = packet
-        }
         impl.writeDatagram(dataToUse) { error in
             completionHandler?(error)
         }
     }
     
     func writePackets(_ packets: [Data], completionHandler: ((Error?) -> Void)?) {
-        var packetsToUse: [Data]
+        let packetsToUse = xor.processPackets(packets, outbound: true)
-        if xorMask != 0 {
-            packetsToUse = packets.map { packet in
-                Data(bytes: packet.map { $0 ^ xorMask }, count: packet.count)
-            }
-        } else {
-            packetsToUse = packets
-        }
         impl.writeMultipleDatagrams(packetsToUse) { error in
             completionHandler?(error)
         }
@@ -109,7 +95,8 @@ class NEUDPLink: LinkInterface {
 }
 
 extension NEUDPSocket: LinkProducer {
-    public func link(xorMask: UInt8?) -> LinkInterface {
+    public func link(userObject: Any?) -> LinkInterface {
-        return NEUDPLink(impl: impl, maxDatagrams: nil, xorMask: xorMask)
+        let xorMethod = userObject as? OpenVPN.XORMethod
+        return NEUDPLink(impl: impl, maxDatagrams: nil, xorMethod: xorMethod)
     }
 }

Sources/TunnelKitOpenVPNAppExtension/OpenVPNTunnelProvider.swift

@@ -408,10 +408,10 @@ extension OpenVPNTunnelProvider: GenericSocketDelegate {
             return
         }
         if session.canRebindLink() {
-            session.rebindLink(producer.link(xorMask: cfg.configuration.xorMask))
+            session.rebindLink(producer.link(userObject: cfg.configuration.xorMethod))
             reasserting = false
         } else {
-            session.setLink(producer.link(xorMask: cfg.configuration.xorMask))
+            session.setLink(producer.link(userObject: cfg.configuration.xorMethod))
         }
     }
     

Sources/TunnelKitOpenVPNCore/Configuration.swift

@@ -209,9 +209,6 @@ extension OpenVPN {
         /// The number of seconds after which a renegotiation should be initiated. If `nil`, the client will never initiate a renegotiation.
         public var renegotiatesAfter: TimeInterval?
         
-        /// A byte to xor all packet payloads with.
-        public var xorMask: UInt8?
-        
         // MARK: Client
         
         /// The list of server endpoints.
@@ -314,6 +311,11 @@ extension OpenVPN {
         /// Server settings that must not be pulled.
         public var noPullMask: [PullMask]?
 
+        // MARK: Extra
+        
+        /// The method to follow in regards to the XOR patch.
+        public var xorMethod: XORMethod?
+        
         /**
          Creates a `ConfigurationBuilder`.
          
@@ -348,7 +350,6 @@ extension OpenVPN {
                 keepAliveInterval: keepAliveInterval,
                 keepAliveTimeout: keepAliveTimeout,
                 renegotiatesAfter: renegotiatesAfter,
-                xorMask: xorMask,
                 remotes: remotes,
                 checksEKU: checksEKU,
                 checksSANHost: checksSANHost,
@@ -376,7 +377,8 @@ extension OpenVPN {
                 proxyAutoConfigurationURL: proxyAutoConfigurationURL,
                 proxyBypassDomains: proxyBypassDomains,
                 routingPolicies: routingPolicies,
-                noPullMask: noPullMask
+                noPullMask: noPullMask,
+                xorMethod: xorMethod
             )
         }
     }
@@ -434,9 +436,6 @@ extension OpenVPN {
         /// - Seealso: `ConfigurationBuilder.renegotiatesAfter`
         public let renegotiatesAfter: TimeInterval?
 
-        /// - Seealso: `ConfigurationBuilder.xorMask`
-        public let xorMask: UInt8?
-        
         /// - Seealso: `ConfigurationBuilder.remotes`
         public let remotes: [Endpoint]?
 
@@ -521,6 +520,9 @@ extension OpenVPN {
         /// - Seealso: `ConfigurationBuilder.noPullMask`
         public let noPullMask: [PullMask]?
         
+        /// - Seealso: `ConfigurationBuilder.xorMethod`
+        public let xorMethod: XORMethod?
+        
         // MARK: Shortcuts
         
         public var fallbackCipher: Cipher {
@@ -597,7 +599,6 @@ extension OpenVPN.Configuration {
         builder.keepAliveInterval = keepAliveInterval
         builder.keepAliveTimeout = keepAliveTimeout
         builder.renegotiatesAfter = renegotiatesAfter
-        builder.xorMask = xorMask
         builder.remotes = remotes
         builder.checksEKU = checksEKU
         builder.checksSANHost = checksSANHost
@@ -626,6 +627,7 @@ extension OpenVPN.Configuration {
         builder.proxyBypassDomains = proxyBypassDomains
         builder.routingPolicies = routingPolicies
         builder.noPullMask = noPullMask
+        builder.xorMethod = xorMethod
         return builder
     }
 }

Sources/TunnelKitOpenVPNCore/ConfigurationParser.swift

@@ -65,8 +65,6 @@ extension OpenVPN {
             
             static let renegSec = NSRegularExpression("^reneg-sec +\\d+")
             
-            static let xorMask = NSRegularExpression("^scramble +xormask +.$")
-            
             static let blockBegin = NSRegularExpression("^<[\\w\\-]+>")
             
             static let blockEnd = NSRegularExpression("^<\\/[\\w\\-]+>")
@@ -121,6 +119,10 @@ extension OpenVPN {
 
             static let routeNoPull = NSRegularExpression("^route-nopull")
             
+            // MARK: Extra
+
+            static let xorInfo = NSRegularExpression("^scramble +(xormask|xorptrpos|reverse|obfuscate)[\\s]?([^\\s]+)?")
+            
             // MARK: Unsupported
             
 //            static let fragment = NSRegularExpression("^fragment +\\d+")
@@ -266,7 +268,6 @@ extension OpenVPN {
             var optKeepAliveSeconds: TimeInterval?
             var optKeepAliveTimeoutSeconds: TimeInterval?
             var optRenegotiateAfterSeconds: TimeInterval?
-            var optXorMask: UInt8?
             //
             var optDefaultProto: SocketType?
             var optDefaultPort: UInt16?
@@ -294,6 +295,8 @@ extension OpenVPN {
             var optProxyBypass: [String]?
             var optRedirectGateway: Set<RedirectGateway>?
             var optRouteNoPull: Bool?
+            //
+            var optXorMethod: XORMethod?
 
             log.verbose("Configuration file:")
             for line in lines {
@@ -518,13 +521,6 @@ extension OpenVPN {
                     }
                     optRenegotiateAfterSeconds = TimeInterval(arg)
                 }
-                Regex.xorMask.enumerateSpacedArguments(in: line) {
-                    isHandled = true
-                    if $0.count != 2 {
-                        return
-                    }
-                    optXorMask = Character($0[1]).asciiValue
-                }
                 
                 // MARK: Client
                 
@@ -713,6 +709,36 @@ extension OpenVPN {
                     optRouteNoPull = true
                 }
                 
+                // MARK: Extra
+
+                Regex.xorInfo.enumerateSpacedArguments(in: line) {
+                    isHandled = true
+                    guard !$0.isEmpty else {
+                        return
+                    }
+
+                    switch $0[0] {
+                    case "xormask":
+                        if $0.count > 1, let mask = $0[1].data(using: .utf8) {
+                            optXorMethod = .xormask(mask: mask)
+                        }
+
+                    case "xorptrpos":
+                        optXorMethod = .xorptrpos
+
+                    case "reverse":
+                        optXorMethod = .reverse
+
+                    case "obfuscate":
+                        if $0.count > 1, let mask = $0[1].data(using: .utf8) {
+                            optXorMethod = .obfuscate(mask: mask)
+                        }
+
+                    default:
+                        return
+                    }
+                }
+                
                 //
                 
                 if let error = unsupportedError {
@@ -821,7 +847,6 @@ extension OpenVPN {
             sessionBuilder.randomizeEndpoint = optRandomizeEndpoint
             sessionBuilder.randomizeHostnames = optRandomizeHostnames
             sessionBuilder.mtu = optMTU
-            sessionBuilder.xorMask = optXorMask
             
             // MARK: Server
             
@@ -939,6 +964,10 @@ extension OpenVPN {
                 sessionBuilder.routingPolicies = [RoutingPolicy](policies)
             }
             
+            // MARK: Extra
+            
+            sessionBuilder.xorMethod = optXorMethod
+
             //
             
             return Result(

Sources/TunnelKitOpenVPNCore/XORMethod.swift

@@ -0,0 +1,77 @@
+//
+//  XORMethod.swift
+//  TunnelKit
+//
+//  Created by Davide De Rosa on 11/4/22.
+//  Copyright (c) 2022 Davide De Rosa. All rights reserved.
+//
+//  https://github.com/passepartoutvpn
+//
+//  This file is part of TunnelKit.
+//
+//  TunnelKit is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation, either version 3 of the License, or
+//  (at your option) any later version.
+//
+//  TunnelKit is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//  GNU General Public License for more details.
+//
+//  You should have received a copy of the GNU General Public License
+//  along with TunnelKit.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+import Foundation
+import CTunnelKitOpenVPNCore
+
+extension OpenVPN {
+    
+    /// The obfuscation method.
+    public enum XORMethod: Codable, Equatable {
+        
+        /// XORs the bytes in each buffer with the given mask.
+        case xormask(mask: Data)
+        
+        /// XORs each byte with its position in the packet.
+        case xorptrpos
+        
+        /// Reverses the order of bytes in each buffer except for the first (abcde becomes aedcb).
+        case reverse
+        
+        /// Performs several of the above steps (xormask -> xorptrpos -> reverse -> xorptrpos).
+        case obfuscate(mask: Data)
+
+        /// This method mapped to native enumeration.
+        public var native: XORMethodNative {
+            switch self {
+            case .xormask:
+                return .mask
+                
+            case .xorptrpos:
+                return .ptrPos
+                
+            case .reverse:
+                return .reverse
+                
+            case .obfuscate:
+                return .obfuscate
+            }
+        }
+
+        /// The optionally associated mask.
+        public var mask: Data? {
+            switch self {
+            case .xormask(let mask):
+                return mask
+                
+            case .obfuscate(let mask):
+                return mask
+                
+            default:
+                return nil
+            }
+        }
+    }
+}

Sources/TunnelKitOpenVPNProtocol/XORProcessor.swift

@@ -0,0 +1,100 @@
+//
+//  XORProcessor.swift
+//  TunnelKit
+//
+//  Created by Davide De Rosa on 11/4/22.
+//  Copyright (c) 2022 Davide De Rosa. All rights reserved.
+//
+//  https://github.com/passepartoutvpn
+//
+//  This file is part of TunnelKit.
+//
+//  TunnelKit is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation, either version 3 of the License, or
+//  (at your option) any later version.
+//
+//  TunnelKit is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//  GNU General Public License for more details.
+//
+//  You should have received a copy of the GNU General Public License
+//  along with TunnelKit.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+import Foundation
+import TunnelKitOpenVPNCore
+
+/// Processes data packets according to a XOR method.
+public struct XORProcessor {
+    private let method: OpenVPN.XORMethod?
+    
+    public init(method: OpenVPN.XORMethod?) {
+        self.method = method
+    }
+    
+    /**
+     Returns an array of data packets processed according to XOR method.
+     
+     - Parameter packets: The array of packets.
+     - Parameter outbound: Set `true` if packets are outbound, `false` otherwise.
+     - Returns: The array of packets after XOR processing.
+     **/
+    public func processPackets(_ packets: [Data], outbound: Bool) -> [Data] {
+        guard let _ = method else {
+            return packets
+        }
+        return packets.map {
+            processPacket($0, outbound: outbound)
+        }
+    }
+    
+    /**
+     Returns a data packet processed according to XOR method.
+     
+     - Parameter packets: The packet.
+     - Parameter outbound: Set `true` if packet is outbound, `false` otherwise.
+     - Returns: The packet after XOR processing.
+     **/
+    public func processPacket(_ packet: Data, outbound: Bool) -> Data {
+        guard let method = method else {
+            return packet
+        }
+        switch method {
+        case .xormask(let mask):
+            return Self.xormask(packet: packet, mask: mask)
+            
+        case .xorptrpos:
+            return Self.xorptrpos(packet: packet)
+            
+        case .reverse:
+            return Self.reverse(packet: packet)
+            
+        case .obfuscate(let mask):
+            if outbound {
+                return Self.xormask(packet: Self.xorptrpos(packet: Self.reverse(packet: Self.xorptrpos(packet: packet))), mask: mask)
+            } else {
+                return Self.xorptrpos(packet: Self.reverse(packet: Self.xorptrpos(packet: Self.xormask(packet: packet, mask: mask))))
+            }
+        }
+    }
+}
+
+extension XORProcessor {
+    private static func xormask(packet: Data, mask: Data) -> Data {
+        Data(packet.enumerated().map { (index, byte) in
+            byte ^ [UInt8](mask)[index % mask.count]
+        })
+    }
+    
+    private static func xorptrpos(packet: Data) -> Data {
+        Data(packet.enumerated().map { (index, byte) in
+            byte ^ UInt8(truncatingIfNeeded: index &+ 1)
+        })
+    }
+    
+    private static func reverse(packet: Data) -> Data {
+        Data(([UInt8](packet))[0..<1] + ([UInt8](packet)[1...]).reversed())
+    }
+}

Tests/TunnelKitOpenVPNTests/ConfigurationParserTests.swift

@@ -127,11 +127,19 @@ class ConfigurationParserTests: XCTestCase {
     func testXOR() throws {
         let cfg = try OpenVPN.ConfigurationParser.parsed(fromLines: ["scramble xormask F"])
         XCTAssertNil(cfg.warning)
-        XCTAssertEqual(cfg.configuration.xorMask, Character("F").asciiValue)
+        XCTAssertEqual(cfg.configuration.xorMethod, OpenVPN.XORMethod.xormask(mask: Data(repeating: Character("F").asciiValue!, count:1)))
         
-        let cfg2 = try OpenVPN.ConfigurationParser.parsed(fromLines: ["scramble xormask FFFF"])
+        let cfg2 = try OpenVPN.ConfigurationParser.parsed(fromLines: ["scramble reverse"])
         XCTAssertNil(cfg.warning)
-        XCTAssertNil(cfg2.configuration.xorMask)
+        XCTAssertEqual(cfg2.configuration.xorMethod, OpenVPN.XORMethod.reverse)
+        
+        let cfg3 = try OpenVPN.ConfigurationParser.parsed(fromLines: ["scramble xorptrpos"])
+        XCTAssertNil(cfg.warning)
+        XCTAssertEqual(cfg3.configuration.xorMethod, OpenVPN.XORMethod.xorptrpos)
+        
+        let cfg4 = try OpenVPN.ConfigurationParser.parsed(fromLines: ["scramble obfuscate FFFF"])
+        XCTAssertNil(cfg.warning)
+        XCTAssertEqual(cfg4.configuration.xorMethod, OpenVPN.XORMethod.obfuscate(mask: Data(repeating: Character("F").asciiValue!, count:4)))
     }
     
     private func privateTestEncryptedCertificateKey(pkcs: String) throws {

Tests/TunnelKitOpenVPNTests/XORTests.swift

@@ -0,0 +1,87 @@
+//
+//  XORTests.swift
+//  TunnelKitOpenVPNTests
+//
+//  Created by Davide De Rosa on 11/4/22.
+//  Copyright (c) 2022 Davide De Rosa. All rights reserved.
+//
+//  https://github.com/passepartoutvpn
+//
+//  This file is part of TunnelKit.
+//
+//  TunnelKit is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation, either version 3 of the License, or
+//  (at your option) any later version.
+//
+//  TunnelKit is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//  GNU General Public License for more details.
+//
+//  You should have received a copy of the GNU General Public License
+//  along with TunnelKit.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+import XCTest
+import TunnelKitCore
+import TunnelKitOpenVPNProtocol
+import CTunnelKitOpenVPNProtocol
+
+final class XORTests: XCTestCase {
+    private let mask = Data(hex: "f76dab30")
+    
+    override func setUpWithError() throws {
+        // Put setup code here. This method is called before the invocation of each test method in the class.
+    }
+
+    override func tearDownWithError() throws {
+        // Put teardown code here. This method is called after the invocation of each test method in the class.
+    }
+
+    func testMask() throws {
+        let processor = XORProcessor(method: .xormask(mask: mask))
+        processor.assertReversible(try SecureRandom.data(length: 1000))
+    }
+
+    func testPtrPos() throws {
+        let processor = XORProcessor(method: .xorptrpos)
+        processor.assertReversible(try SecureRandom.data(length: 1000))
+    }
+
+    func testReverse() throws {
+        let processor = XORProcessor(method: .reverse)
+        processor.assertReversible(try SecureRandom.data(length: 1000))
+    }
+
+    func testObfuscate() throws {
+        let processor = XORProcessor(method: .obfuscate(mask: mask))
+        processor.assertReversible(try SecureRandom.data(length: 1000))
+    }
+
+    func testPacketStream() throws {
+        let data = try SecureRandom.data(length: 10000)
+        PacketStream.assertReversible(data, method: .none)
+        PacketStream.assertReversible(data, method: .mask, mask: mask)
+        PacketStream.assertReversible(data, method: .ptrPos)
+        PacketStream.assertReversible(data, method: .reverse)
+        PacketStream.assertReversible(data, method: .obfuscate, mask: mask)
+    }
+}
+
+private extension XORProcessor {
+    func assertReversible(_ data: Data) {
+        let xored = processPacket(data, outbound: true)
+        XCTAssertEqual(processPacket(xored, outbound: false), data)
+    }
+}
+
+private extension PacketStream {
+    static func assertReversible(_ data: Data, method: XORMethodNative, mask: Data? = nil) {
+        var until = 0
+        let outStream = PacketStream.outboundStream(fromPacket: data, xorMethod: method, xorMask: mask)
+        let inStream = PacketStream.packets(fromInboundStream: outStream, until: &until, xorMethod: method, xorMask: mask)
+        let originalData = Data(inStream.joined())
+        XCTAssertEqual(data.toHex(), originalData.toHex())
+    }
+}