ZVISION: Add xor encryption handling to ZfsArchive class

2 files changed, 45 insertions, 12 deletions

diff --git a/engines/zvision/zfsArchive.cpp b/engines/zvision/zfsArchive.cpp
index a3111d7705..59e65f1713 100644
--- a/engines/zvision/zfsArchive.cpp
+++ b/engines/zvision/zfsArchive.cpp
@@ -55,16 +55,17 @@ ZfsArchive::~ZfsArchive() {
 }
 
 void ZfsArchive::readHeaders(Common::SeekableReadStream *stream) {
-	ZfsHeader header;
-
 	// Don't do a straight struct cast since we can't guarantee endianness
-	header.magic = stream->readUint32LE();
-	header.unknown1 = stream->readUint32LE();
-	header.unknown2 = stream->readUint32LE();
-	header.filesPerBlock = stream->readUint32LE();
-	header.fileCount = stream->readUint32LE();
-	header.xorKey = stream->readUint32LE();
-	header.fileSectionOffset = stream->readUint32LE();
+	_header.magic = stream->readUint32LE();
+	_header.unknown1 = stream->readUint32LE();
+	_header.maxNameLength = stream->readUint32LE();
+	_header.filesPerBlock = stream->readUint32LE();
+	_header.fileCount = stream->readUint32LE();
+	_header.xorKey[0] = stream->readByte();
+	_header.xorKey[1] = stream->readByte();
+	_header.xorKey[2] = stream->readByte();
+	_header.xorKey[3] = stream->readByte();
+	_header.fileSectionOffset = stream->readUint32LE();
 
 	uint32 nextOffset;
 
@@ -73,7 +74,7 @@ void ZfsArchive::readHeaders(Common::SeekableReadStream *stream) {
 		nextOffset = stream->readUint32LE();
 
 		// Read in each entry header
-		for (int i = 0; i < header.filesPerBlock; i++) {
+		for (int i = 0; i < _header.filesPerBlock; i++) {
 			ZfsEntryHeader entryHeader;
 			
 			entryHeader.name = readEntryName(stream);
@@ -135,10 +136,18 @@ Common::SeekableReadStream *ZfsArchive::createReadStreamForMember(const Common::
 
 	byte* buffer = new byte[entryHeader->size];
 	zfsArchive.read(buffer, entryHeader->size);
+	// Decrypt the data in place
+	if (_header.xorKey != 0)
+		unXor(buffer, entryHeader->size, _header.xorKey);
 
 	return new Common::MemoryReadStream(buffer, entryHeader->size, DisposeAfterUse::YES);
 }
 
+void ZfsArchive::unXor(byte *buffer, int length, const byte *xorKey) const {
+	for (uint32 i = 0; i < length; i++)
+		buffer[i] ^= xorKey[i % 4];
+}
+
 } // End namespace ZVision
 
 
diff --git a/engines/zvision/zfsArchive.h b/engines/zvision/zfsArchive.h
index 96c002f815..718b26c836 100644
--- a/engines/zvision/zfsArchive.h
+++ b/engines/zvision/zfsArchive.h
@@ -32,10 +32,10 @@ namespace ZVision {
 struct ZfsHeader {
 	uint32 magic;
 	uint32 unknown1;
-	uint32 unknown2;
+	uint32 maxNameLength;
 	uint32 filesPerBlock;
 	uint32 fileCount;
-	uint32 xorKey;
+	byte xorKey[4];
 	uint32 fileSectionOffset;
 };
 
@@ -85,10 +85,34 @@ public:
 
 private:
 	const Common::String _fileName;
+	ZfsHeader _header;
 	ZfsEntryHeaderMap _entryHeaders;
 
+	/**
+	 * Parses the zfs file into file entry headers that can be used later
+	 * to get the entry data.
+	 *
+	 * @param stream	The contents of the zfs file
+	 */
 	void readHeaders(Common::SeekableReadStream *stream);
+
+	/**
+	 * Entry names are contained within a 16 byte block. This reads the block
+	 * and converts it the name to a Common::String
+	 *
+	 * @param stream	The zfs file stream
+	 * @return			The entry file name
+	 */
 	Common::String readEntryName(Common::SeekableReadStream *stream) const;
+
+	/**
+	 * ZFS file entries can be encrypted using XOR encoding. This method
+	 * decodes the buffer in place using the supplied xorKey.
+	 *
+	 * @param buffer	The data to decode
+	 * @param length	Length of buffer
+	 */
+	void unXor(byte *buffer, int length, const byte *xorKey) const;
 };
 
 } // End of namespace Common