Moved the IV creation into another function, the hash function don't really need the contentIndex.

src/de/mas/wiiu/jnus/implementations/FSTDataProviderNUSTitle.java

@@ -20,6 +20,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.security.NoSuchAlgorithmException;
+import java.util.Arrays;
 import java.util.Optional;
 import java.util.stream.Collectors;
 
@@ -30,6 +31,7 @@ import de.mas.wiiu.jnus.interfaces.FSTDataProvider;
 import de.mas.wiiu.jnus.interfaces.HasNUSTitle;
 import de.mas.wiiu.jnus.interfaces.NUSDataProvider;
 import de.mas.wiiu.jnus.utils.CheckSumWrongException;
+import de.mas.wiiu.jnus.utils.StreamUtils;
 import de.mas.wiiu.jnus.utils.Utils;
 import de.mas.wiiu.jnus.utils.cryptography.NUSDecryption;
 import lombok.Getter;
@@ -91,10 +93,11 @@ public class FSTDataProviderNUSTitle implements FSTDataProvider, HasNUSTitle {
         Content c = title.getTMD().getContentByIndex(entry.getContentIndex());
 
         long payloadOffset = entry.getFileOffset() + offset;
-
         long streamOffset = payloadOffset;
-
         long streamFilesize = c.getEncryptedFileSize();
+
+        Optional<byte[]> IV = Optional.empty();
+
         if (c.isHashed()) {
             streamOffset = (payloadOffset / 0xFC00) * 0x10000;
             long offsetInBlock = payloadOffset - ((streamOffset / 0x10000) * 0xFC00);
@@ -113,16 +116,22 @@ public class FSTDataProviderNUSTitle implements FSTDataProvider, HasNUSTitle {
                 streamFilesize = curVal;
             }
         } else {
-            if (size != entry.getFileSize()) {             
+            byte[] newIV = new byte[0x10];
+            newIV[0] = (byte) ((c.getIndex() >> 8) & 0xFF);
+            newIV[1] = (byte) (c.getIndex() & 0xFF);
+            IV = Optional.of(newIV);
+
+            // if we have an offset we can't calculate the hash anymore
+            // we need a new IV
+            if (streamOffset > 0) {
                 streamFilesize = size;
 
-                // We need the previous IV if we don't start at the first block.
-                if (payloadOffset >= 16) {
                 streamOffset -= 16;
                 streamFilesize += 16;
-                }
-            }
 
+                // We need to get the current IV as soon as we get the InputStream.
+                IV = Optional.empty();
+            }
         }
 
         NUSDataProvider dataProvider = title.getDataProvider();
@@ -134,8 +143,27 @@ public class FSTDataProviderNUSTitle implements FSTDataProvider, HasNUSTitle {
             Optional<byte[]> h3HashedOpt = Optional.empty();
             if (c.isHashed()) {
                 h3HashedOpt = dataProvider.getContentH3Hash(c);
+            } else {
+                if (!IV.isPresent()) {
+                    // If we read with an offset > 16 we need the previous 16 bytes because they are the IV.
+                    // The input stream has been prepared to start 16 bytes earlier on this case.
+                    int toRead = 16;
+                    byte[] data = new byte[toRead];
+                    int readTotal = 0;
+                    while (readTotal < toRead) {
+                        int res = in.read(data, readTotal, toRead - readTotal);
+                        StreamUtils.checkForException(in);
+                        if (res < 0) {
+                            // This should NEVER happen.
+                            throw new IOException();
                         }
-            return nusdecryption.decryptStreams(in, outputStream, payloadOffset, size, c, h3HashedOpt, size != entry.getFileSize());
+                        readTotal += res;
+                    }
+                    IV = Optional.of(Arrays.copyOfRange(data, 0, toRead));
+                }
+            }
+
+            return nusdecryption.decryptStreams(in, outputStream, payloadOffset, size, c, IV, h3HashedOpt, size != entry.getFileSize());
         } catch (CheckSumWrongException e) {
             if (c.isUNKNWNFlag1Set()) {
                 log.info("Hash doesn't match. But file is optional. Don't worry.");

src/de/mas/wiiu/jnus/utils/cryptography/NUSDecryption.java

@@ -57,7 +57,7 @@ public class NUSDecryption extends AESDecryption {
         return decrypt(blockBuffer, offset, BLOCKSIZE);
     }
 
-    public void decryptFileStream(InputStream inputStream, OutputStream outputStream, long fileOffset, long filesize, short contentIndex, byte[] h3hash,
+    public void decryptFileStream(InputStream inputStream, OutputStream outputStream, long fileOffset, long filesize, byte[] IV, byte[] h3hash,
             long expectedSizeForHash) throws IOException, CheckSumWrongException {
         MessageDigest sha1 = null;
 
@@ -70,15 +70,6 @@ public class NUSDecryption extends AESDecryption {
         }
 
         int BLOCKSIZE = 0x8000;
-        // long dlFileLength = filesize;
-        // if(dlFileLength > (dlFileLength/BLOCKSIZE)*BLOCKSIZE){
-        // dlFileLength = ((dlFileLength/BLOCKSIZE)*BLOCKSIZE) +BLOCKSIZE;
-        // }
-
-        byte[] IV = new byte[0x10];
-
-        IV[0] = (byte) ((contentIndex >> 8) & 0xFF);
-        IV[1] = (byte) (contentIndex);
 
         byte[] blockBuffer = new byte[BLOCKSIZE];
 
@@ -87,23 +78,6 @@ public class NUSDecryption extends AESDecryption {
         long writtenHash = 0;
 
         try {
-            // The input stream has been prepared to start 16 bytes earlier on this case.
-            if (fileOffset >= 16) {
-                int toRead = 16;
-                byte[] data = new byte[toRead];
-                int readTotal = 0;
-                while (readTotal < toRead) {
-                    int res = inputStream.read(data, readTotal, toRead - readTotal);
-                    StreamUtils.checkForException(inputStream);
-                    if (res < 0) {
-                        // This should NEVER happen.
-                        throw new IOException();
-                    }
-                    readTotal += res;
-                }
-                IV = Arrays.copyOfRange(data, 0, toRead);
-            }
-
             ByteArrayBuffer overflow = new ByteArrayBuffer(BLOCKSIZE);
 
             // We can only decrypt multiples of 16. So we need to align it.
@@ -171,7 +145,7 @@ public class NUSDecryption extends AESDecryption {
         }
     }
 
-    public void decryptFileStreamHashed(InputStream inputStream, OutputStream outputStream, long fileoffset, long filesize, short contentIndex, byte[] h3Hash)
+    public void decryptFileStreamHashed(InputStream inputStream, OutputStream outputStream, long fileoffset, long filesize, byte[] h3Hash)
             throws IOException, CheckSumWrongException, NoSuchAlgorithmException {
         int BLOCKSIZE = 0x10000;
         int HASHBLOCKSIZE = 0xFC00;
@@ -202,7 +176,7 @@ public class NUSDecryption extends AESDecryption {
 
                 byte[] output;
                 try {
-                    output = decryptFileChunkHash(encryptedBlockBuffer, (int) block, contentIndex, h3Hash);
+                    output = decryptFileChunkHash(encryptedBlockBuffer, (int) block, h3Hash);
                 } catch (CheckSumWrongException | NoSuchAlgorithmException e) {
                     throw e;
                 }
@@ -235,20 +209,15 @@ public class NUSDecryption extends AESDecryption {
         }
     }
 
-    private byte[] decryptFileChunkHash(byte[] blockBuffer, int block, int contentIndex, byte[] h3_hashes)
+    private byte[] decryptFileChunkHash(byte[] blockBuffer, int block, byte[] h3_hashes) throws CheckSumWrongException, NoSuchAlgorithmException {
-            throws CheckSumWrongException, NoSuchAlgorithmException {
         int hashSize = 0x400;
         int blocksize = 0xFC00;
-        byte[] IV = ByteBuffer.allocate(16).putShort((short) contentIndex).array();
 
-        byte[] hashes = decryptFileChunk(blockBuffer, hashSize, IV);
+        byte[] hashes = decryptFileChunk(blockBuffer, hashSize, new byte[16]);
-
-        hashes[0] ^= (byte) ((contentIndex >> 8) & 0xFF);
-        hashes[1] ^= (byte) (contentIndex & 0xFF);
 
         int H0_start = (block % 16) * 20;
 
-        IV = Arrays.copyOfRange(hashes, H0_start, H0_start + 16);
+        byte[] IV = Arrays.copyOfRange(hashes, H0_start, H0_start + 16);
         byte[] output = decryptFileChunk(blockBuffer, hashSize, blocksize, IV);
 
         HashUtil.checkFileChunkHashes(hashes, h3_hashes, output, block);
@@ -256,10 +225,8 @@ public class NUSDecryption extends AESDecryption {
         return output;
     }
 
-    public boolean decryptStreams(InputStream inputStream, OutputStream outputStream, long offset, long size, Content content, Optional<byte[]> h3HashHashed,
+    public boolean decryptStreams(InputStream inputStream, OutputStream outputStream, long offset, long size, Content content, Optional<byte[]> IV,
-            boolean partial) throws IOException, CheckSumWrongException, NoSuchAlgorithmException {
+            Optional<byte[]> h3HashHashed, boolean partial) throws IOException, CheckSumWrongException, NoSuchAlgorithmException {
-
-        short contentIndex = (short) content.getIndex();
 
         long encryptedFileSize = content.getEncryptedFileSize();
 
@@ -267,14 +234,14 @@ public class NUSDecryption extends AESDecryption {
             if (content.isEncrypted()) {
                 if (content.isHashed()) {
                     byte[] h3 = h3HashHashed.orElseThrow(() -> new FileNotFoundException("h3 hash not found."));
-                    decryptFileStreamHashed(inputStream, outputStream, offset, size, (short) contentIndex, h3);
+                    decryptFileStreamHashed(inputStream, outputStream, offset, size, h3);
                 } else {
                     byte[] h3Hash = content.getSHA2Hash();
                     // Ignore the h3hash if we don't read the whole file.
                     if (partial) {
                         h3Hash = null;
                     }
-                    decryptFileStream(inputStream, outputStream, offset, size, (short) contentIndex, h3Hash, encryptedFileSize);
+                    decryptFileStream(inputStream, outputStream, offset, size, IV.orElseThrow(() -> new IOException("Missing IV")), h3Hash, encryptedFileSize);
                 }
             } else {
                 StreamUtils.saveInputStreamToOutputStreamWithHash(inputStream, outputStream, size, content.getSHA2Hash(), encryptedFileSize);