♻ Move skipping of encryption header out of decryption

src/ssn/decryption/decryptChunk.ts

@@ -24,7 +24,8 @@ export default function getDecryptor(decryptionKeys: [number, number, number]) {
   let position = 0;
 
   return (encryptedChunk: Buffer) => {
-    const decryptedChunk = Buffer.alloc(encryptedChunk.length - Math.max(12 - position, 0));
+    const decryptedChunk = Buffer.alloc(encryptedChunk.length);
+    //const decryptedChunk = Buffer.alloc(encryptedChunk.length - Math.max(12 - position, 0));
 
     for (let i = 0; i < encryptedChunk.length; i += 1) {
       //read byte
@@ -39,13 +40,14 @@ export default function getDecryptor(decryptionKeys: [number, number, number]) {
       [key0, key1, key2] = updateKeys([key0, key1, key2], curChar);
 
       //write byte
-      if (position + i < 12) {
+      /*if (position + i < 12) {
         //do nothing
       } else if (position + i >= 12 && position < 12) {
         decryptedChunk.writeUInt8(curChar, position + i - 12);
       } else {
         decryptedChunk.writeUInt8(curChar, i);
-      }
+      }*/
+      decryptedChunk.writeUInt8(curChar, i);
     }
 
     position += encryptedChunk.length;

src/ssn/decryption/decryptFile.ts

@@ -1,23 +0,0 @@
-import updateKeys from './lib/updateKeys';
-
-export default function decryptFile(dv: DataView, length: number, [key0, key1, key2]: [number, number, number]) {
-  const decryptedBuffer = new ArrayBuffer(length - 12);
-  const dvOut = new DataView(decryptedBuffer);
-
-  for (let i = 0; i < length; i += 1) {
-    //read and decrypt byte
-    let curChar = dv.getUint8(i);
-    const keyPart = (key2 | 2) & 0xFFFF;
-    const decryptedByte = (keyPart * (keyPart ^ 1)) >>> 8;
-    curChar ^= decryptedByte & 0xFF;
-    //Skip the first 12 bytes (random encryption header)
-    if (i >= 12) {
-      dvOut.setUint8(i - 12, curChar);
-    }
-
-    //update keys
-    [key0, key1, key2] = updateKeys([key0, key1, key2], curChar);
-  }
-
-  return dvOut;
-}

src/ssn/extractFile.ts

@@ -1,43 +0,0 @@
-import * as zlib from 'zlib';
-import { ISsnFileEntry } from '../interfaces/ISsnFileEntry';
-import decryptFile from './decryption/decryptFile';
-import ByteReader from './extractFileByteReader';
-
-/** Extracts the given file from the given DataView array and returns it as an ArrayBuffer.
- * Will throw an error when end of final DataView is reached.
- */
-export default async function extractFile(file: ISsnFileEntry, dvArray: DataView[]): Promise<ArrayBuffer> {
-  //Use ByteReader for reading a uint8 and seeking forward across DataView boundaries
-  const byteReader = new ByteReader(dvArray, file.diskNumberStart, file.offset);
-
-  //Local file header signature
-  if (byteReader.readUint32() !== 0x04034B50) {
-    throw new Error('Local file header had wrong magic');
-  }
-  //All fields in the local file header are copies of the central file header, so we can skip them.
-  //FIXME: Maybe we should actually read these fields to verify that they are identical?
-  byteReader.seek(22);
-  const localFilenameSize = byteReader.readUint16();
-  const localExtraSize = byteReader.readUint16();
-  byteReader.seek(localFilenameSize + localExtraSize);
-
-  //Extract actual file contents
-  let dvFinal = byteReader.extractDv(file.compressedSize);
-
-  //Decrypt file if necessary
-  if (file.decryptionKeys !== undefined) {
-    dvFinal = decryptFile(dvFinal, file.compressedSize, file.decryptionKeys);
-  }
-
-  //Decompress file
-  const decompressedBuffer: Buffer = await new Promise((resolve, reject) => {
-    zlib.inflateRaw(dvFinal, (error, result) => {
-      if (error !== null) {
-        return reject(error);
-      }
-      resolve(result);
-    });
-  }) as Buffer;
-
-  return decompressedBuffer.buffer as ArrayBuffer;
-}

src/ssn/extractFileByteReader.ts

@@ -1,46 +0,0 @@
-export default class ByteReader {
-  private dvArray: DataView[];
-  private dvIndex = 0;
-  private pos = 0;
-  constructor(dvArray: DataView[], startDvIndex: number, offset: number) {
-    this.dvArray = dvArray;
-    this.dvIndex = startDvIndex;
-    this.pos = offset;
-  }
-  /** Reads one byte and returns it. */
-  public readUint8() {
-    const curByte = this.dvArray[this.dvIndex].getUint8(this.pos);
-    this.pos += 1;
-    if (this.pos >= this.dvArray[this.dvIndex].byteLength) {
-      this.pos = 0;
-      this.dvIndex += 1;
-      if (this.dvIndex >= this.dvArray.length) { throw new Error('Tried to read beyond DataView boundary in extractFile'); }
-    }
-    return curByte;
-  }
-  /** Reads two bytes as an unsigned 16-bit integer and returns it. */
-  public readUint16() {
-    return this.readUint8() | (this.readUint8() << 8);
-  }
-  /** Reads four bytes as an unsigned 32-bit integer and returns it. */
-  public readUint32() {
-    return (this.readUint8() | (this.readUint8() << 8) | (this.readUint8() << 16) | (this.readUint8() << 24)) >>> 0;
-  }
-  /** Seeks the given number of bytes forward, without reading the bytes. */
-  public seek(numBytes: number) {
-    this.pos += numBytes;
-    if (this.pos >= this.dvArray[this.dvIndex].byteLength) {
-      this.pos -= this.dvArray[this.dvIndex].byteLength;
-      this.dvIndex += 1;
-      if (this.dvIndex >= this.dvArray.length) { throw new Error('Tried to read beyond DataView boundary in extractFile'); }
-    }
-  }
-  /** Reads the given amount of bytes, and returns it as a DataView. */
-  public extractDv(length: number) {
-    const dv = new DataView(new ArrayBuffer(length));
-    for (let i = 0; i < length; i += 1) {
-        dv.setUint8(i, this.readUint8()); //TODO: refactor this so it is more optimized
-    }
-    return dv;
-  }
-}

src/ssn/extractFileStream.ts

@@ -16,6 +16,8 @@ export default function extractFileStream(file: ISsnFileEntry, inputStream: stre
   if (file.decryptionKeys !== undefined) {
     const decryptTransform = decryptStream(file.decryptionKeys);
     curStream = curStream.pipe(decryptTransform);
+    //skip encryption header
+    curStream.read(12);
   }
 
   if (!skipDecompression) {

src/ssn/streams/getFileFromDisks.ts

@@ -16,7 +16,7 @@ function createFileStream(disks: string[], index: number, offset: number, length
 }
 
 /** Takes a list of ReadableStreams (the disks), as well as the offset and length, and returns a stream for just one file. */
-async function getFullStream(disks: string[], { diskStart, offset, length }: IGetFileFromDisksOptions): Promise<stream.Readable> {
+async function getConcatenatedStream(disks: string[], { diskStart, offset, length }: IGetFileFromDisksOptions): Promise<stream.Readable> {
   let curDiskIndex = diskStart;
   let curDisk: fs.ReadStream = createFileStream(disks, diskStart, offset);
   let totalRead = 0;
@@ -72,10 +72,10 @@ async function getFullStream(disks: string[], { diskStart, offset, length }: IGe
 
 export default async function getFileFromDisks(disks: string[], { diskStart, offset, length }: IGetFileFromDisksOptions): Promise<stream.Readable> {
   //read local file header
-  const headerStream = await getFullStream(disks, { diskStart, offset, length: 30 });
+  const headerStream = await getConcatenatedStream(disks, { diskStart, offset, length: 30 });
   const localFileHeaderLength = await readLocalFileHeader(headerStream);
   headerStream.destroy(); //TODO: is this the best way to close/destroy the stream?
 
   //read actual file
-  return getFullStream(disks, { diskStart, offset: offset + localFileHeaderLength, length });
+  return getConcatenatedStream(disks, { diskStart, offset: offset + localFileHeaderLength, length });
 }