Properly align decrypted contents

We previously did not properly account for the needed length to read. Nintendo supplies encrypted contents aligned to 16. We read that much, decrypt, and then remove the additional padding.

file.go

@@ -31,7 +31,16 @@ func readData(data []byte, contents []ContentRecord, titleKey [16]byte) ([]WADFi
 	for _, content := range contents {
 		// It's okay to cast this from a uint64 as the WAD file format
 		// cannot exceed the maximum uint32 value within the data section.
-		encryptedData := r.getRange(uint32(content.Size))
+		// We read aligned to 16 bytes as the encrypted data is stored with padding.
+		// Not all contents meet the expected 16-byte boundary.
+		paddedSize := uint32(content.Size)
+		leftover := paddedSize % 16
+		if leftover != 0 {
+			paddedSize += 16 - leftover
+		}
+
+		// Read the padded amount as aligned to 64 bytes.
+		encryptedData := r.getRange(paddedSize)
 
 		// The title's decrypted key will be what we'll decrypt with.
 		block, err := aes.NewCipher(titleKey[:])
@@ -51,11 +60,14 @@ func readData(data []byte, contents []ContentRecord, titleKey [16]byte) ([]WADFi
 		blockMode := cipher.NewCBCDecrypter(block, iv)
 
 		// The resulting decrypted contents is the same size as the input, including padding.
-		decryptedData := make([]byte, content.Size)
+		decryptedData := make([]byte, paddedSize)
 
 		// ...and we're off!
 		blockMode.CryptBlocks(decryptedData, encryptedData)
 
+		// Trim off the excess padding once decrypted.
+		decryptedData = decryptedData[:content.Size]
+
 		// Ensure that the decrypted data matches the SHA-1 hash given in the contents list.
 		sha := sha1.Sum(decryptedData)
 		if bytes.Compare(sha[:], content.Hash[:]) != 0 {

wad.go

@@ -31,7 +31,7 @@ type WADHeader struct {
 }
 
 // getPadding returns the given size, padded to the nearest 0x40/64-byte boundary.
-// This is useful as all WAD contents are padded to such.
+// This is useful as many types of contents are padded to such.
 func getPadding(size uint32) uint32 {
 	// Empty things aren't padded.
 	if size == 0 {
@@ -112,8 +112,7 @@ func LoadWAD(contents []byte) (*WAD, error) {
 	certificate := r.getRange(header.CertificateSize)
 	crl := r.getRange(header.CRLSize)
 
-	// We'll next
-	// Load a ticket from our contents into the struct.
+	// We'll next load a ticket from our contents into the struct.
 	var ticket Ticket
 	loadingBuf = r.getBuffer(header.TicketSize)
 	err = binary.Read(loadingBuf, binary.BigEndian, &ticket)