Shut down on compressed data packet

Re-inforce #65 at the data path level. Should now cover all
compression scenarios.

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Added
+
+- Shut down if server pushes a compressed data packet.
+
 ## 1.4.1 (2019-02-25)
 
 ### Added

TunnelKit/Sources/AppExtension/TunnelKitProvider.swift

@@ -586,6 +586,9 @@ extension TunnelKitProvider {
                 
             case .dataPathOverflow, .dataPathPeerIdMismatch:
                 return .unexpectedReply
+                
+            case .dataPathCompression:
+                return .serverCompression
             }
         } else if let se = error as? SessionError {
             switch se {

TunnelKit/Sources/Core/CryptoAEAD.m

@@ -346,7 +346,7 @@ static const NSInteger CryptoAEADTagLength = 16;
     return YES;
 }
 
-- (const uint8_t *)parsePayloadWithBlock:(DataPathParseBlock)block length:(NSInteger *)length packetBytes:(uint8_t *)packetBytes packetLength:(NSInteger)packetLength
+- (const uint8_t *)parsePayloadWithBlock:(DataPathParseBlock)block length:(NSInteger *)length packetBytes:(uint8_t *)packetBytes packetLength:(NSInteger)packetLength error:(NSError * _Nullable __autoreleasing * _Nullable)error
 {
     uint8_t *payload = packetBytes;
     *length = packetLength - (int)(payload - packetBytes);
@@ -356,7 +356,9 @@ static const NSInteger CryptoAEADTagLength = 16;
     
     NSInteger payloadOffset;
     NSInteger payloadHeaderLength;
-    block(payload, &payloadOffset, &payloadHeaderLength, packetBytes, packetLength);
+    if (!block(payload, &payloadOffset, &payloadHeaderLength, packetBytes, packetLength, error)) {
+        return NULL;
+    }
     *length -= payloadHeaderLength;
     return payload + payloadOffset;
 }

TunnelKit/Sources/Core/CryptoCBC.m

@@ -368,7 +368,7 @@ const NSInteger CryptoCBCMaxHMACLength = 100;
     return YES;
 }
 
-- (const uint8_t *)parsePayloadWithBlock:(DataPathParseBlock)block length:(NSInteger *)length packetBytes:(uint8_t *)packetBytes packetLength:(NSInteger)packetLength
+- (const uint8_t *)parsePayloadWithBlock:(DataPathParseBlock)block length:(NSInteger *)length packetBytes:(uint8_t *)packetBytes packetLength:(NSInteger)packetLength error:(NSError * _Nullable __autoreleasing * _Nullable)error
 {
     uint8_t *payload = packetBytes;
     payload += sizeof(uint32_t); // packet id
@@ -379,7 +379,9 @@ const NSInteger CryptoCBCMaxHMACLength = 100;
 
     NSInteger payloadOffset;
     NSInteger payloadHeaderLength;
-    block(payload, &payloadOffset, &payloadHeaderLength, packetBytes, packetLength);
+    if (!block(payload, &payloadOffset, &payloadHeaderLength, packetBytes, packetLength, error)) {
+        return NULL;
+    }
     *length -= payloadHeaderLength;
     return payload + payloadOffset;
 }

TunnelKit/Sources/Core/DataPath.m

@@ -162,9 +162,10 @@
                 memcpy(packetDest, payload.bytes, payload.length);
                 *packetLengthOffset = 0;
             };
-            self.parsePayloadBlock = ^(uint8_t * payload, NSInteger *payloadOffset, NSInteger * headerLength, const uint8_t * packet, NSInteger packetLength) {
+            self.parsePayloadBlock = ^BOOL(uint8_t * _Nonnull payload, NSInteger * _Nonnull payloadOffset, NSInteger * _Nonnull headerLength, const uint8_t * _Nonnull packet, NSInteger packetLength, NSError * _Nullable __autoreleasing * _Nullable error) {
                 *payloadOffset = 0;
                 *headerLength = 0;
+                return YES;
             };
             break;
         }
@@ -175,11 +176,16 @@
                 packetDest[0] = DataPacketNoCompressSwap;
                 *packetLengthOffset = 1;
             };
-            self.parsePayloadBlock = ^(uint8_t * payload, NSInteger *payloadOffset, NSInteger * headerLength, const uint8_t * packet, NSInteger packetLength) {
+            self.parsePayloadBlock = ^BOOL(uint8_t * _Nonnull payload, NSInteger * _Nonnull payloadOffset, NSInteger * _Nonnull headerLength, const uint8_t * _Nonnull packet, NSInteger packetLength, NSError * _Nullable __autoreleasing * _Nullable error) {
-                NSCAssert(payload[0] == DataPacketNoCompressSwap, @"Expected NO_COMPRESS_SWAP (found %X != %X)", payload[0], DataPacketNoCompressSwap);
+                if (payload[0] != DataPacketNoCompressSwap) {
+                    // @"Expected NO_COMPRESS_SWAP (found %X != %X)", payload[0], DataPacketNoCompressSwap);
+                    *error = TunnelKitErrorWithCode(TunnelKitErrorCodeDataPathCompression);
+                    return NO;
+                }
                 payload[0] = packet[packetLength - 1];
                 *payloadOffset = 0;
                 *headerLength = 1;
+                return YES;
             };
             break;
         }
@@ -189,10 +195,17 @@
                 packetDest[0] = DataPacketNoCompress;
                 *packetLengthOffset = 1;
             };
-            self.parsePayloadBlock = ^(uint8_t * payload, NSInteger *payloadOffset, NSInteger * headerLength, const uint8_t * packet, NSInteger packetLength) {
+            self.parsePayloadBlock = ^BOOL(uint8_t * _Nonnull payload, NSInteger * _Nonnull payloadOffset, NSInteger * _Nonnull headerLength, const uint8_t * _Nonnull packet, NSInteger packetLength, NSError * _Nullable __autoreleasing * _Nullable error) {
-                NSCAssert(payload[0] == DataPacketNoCompress, @"Expected NO_COMPRESS (found %X != %X)", payload[0], DataPacketNoCompress);
+                if (payload[0] != DataPacketNoCompress) {
+                    // @"Expected NO_COMPRESS (found %X != %X)", payload[0], DataPacketNoCompress);
+                    if (error) {
+                        *error = TunnelKitErrorWithCode(TunnelKitErrorCodeDataPathCompression);
+                    }
+                    return NO;
+                }
                 *payloadOffset = 1;
                 *headerLength = 1;
+                return YES;
             };
             break;
         }
@@ -280,7 +293,11 @@
         const uint8_t *payloadBytes = [self.decrypter parsePayloadWithBlock:self.parsePayloadBlock
                                                                      length:&payloadLength
                                                                 packetBytes:dataPacketBytes
-                                                               packetLength:dataPacketLength];
+                                                               packetLength:dataPacketLength
+                                                                      error:error];
+        if (!payloadBytes) {
+            return nil;
+        }
         
         if ((payloadLength == sizeof(DataPacketPingData)) && !memcmp(payloadBytes, DataPacketPingData, payloadLength)) {
             if (keepAlive) {

TunnelKit/Sources/Core/DataPathCrypto.h

@@ -57,7 +57,12 @@ NS_ASSUME_NONNULL_BEGIN
     }
 
 typedef void (^DataPathAssembleBlock)(uint8_t *packetDest, NSInteger *packetLengthOffset, NSData *payload);
-typedef void (^DataPathParseBlock)(uint8_t *payload, NSInteger *payloadOffset, NSInteger *headerLength, const uint8_t *packet, NSInteger packetLength);
+typedef BOOL (^DataPathParseBlock)(uint8_t *payload,
+                                   NSInteger *payloadOffset,
+                                   NSInteger *headerLength,
+                                   const uint8_t *packet,
+                                   NSInteger packetLength,
+                                   NSError **error);
 
 @protocol DataPathChannel
 
@@ -77,7 +82,7 @@ typedef void (^DataPathParseBlock)(uint8_t *payload, NSInteger *payloadOffset, N
 @protocol DataPathDecrypter <DataPathChannel>
 
 - (BOOL)decryptDataPacket:(NSData *)packet into:(uint8_t *)packetBytes length:(NSInteger *)packetLength packetId:(uint32_t *)packetId error:(NSError **)error;
-- (const uint8_t *)parsePayloadWithBlock:(nullable DataPathParseBlock)block length:(NSInteger *)length packetBytes:(uint8_t *)packetBytes packetLength:(NSInteger)packetLength;
+- (const uint8_t * _Nullable)parsePayloadWithBlock:(nullable DataPathParseBlock)block length:(NSInteger *)length packetBytes:(uint8_t *)packetBytes packetLength:(NSInteger)packetLength error:(NSError **)error;
 
 @end
 

TunnelKit/Sources/Core/Errors.h

@@ -51,7 +51,8 @@ typedef NS_ENUM(NSInteger, TunnelKitErrorCode) {
     TunnelKitErrorCodeTLSBoxServerCertificate   = 206,
     TunnelKitErrorCodeTLSBoxServerEKU           = 207,
     TunnelKitErrorCodeDataPathOverflow          = 301,
-    TunnelKitErrorCodeDataPathPeerIdMismatch    = 302
+    TunnelKitErrorCodeDataPathPeerIdMismatch    = 302,
+    TunnelKitErrorCodeDataPathCompression       = 303
 };
 
 static inline NSError *TunnelKitErrorWithCode(TunnelKitErrorCode code) {