--- /dev/null
+package org.readium.r2_streamer.parser;
+
+import org.readium.r2_streamer.model.publication.Encryption;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.UnsupportedEncodingException;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.Formatter;
+import java.util.HashMap;
+
+/**
+ * Created by gautam chibde on 18/5/17.
+ */
+
+public final class EncryptionDecoder {
+ private final static String TAG = EncryptionDecoder.class.getName();
+
+ private static HashMap<String, Integer> decoders = new HashMap<>();
+
+ static {
+ EncryptionDecoder.decoders.put("http://www.idpf.org/2008/embedding", 1040);
+ EncryptionDecoder.decoders.put("http://ns.adobe.com/pdf/enc#RC", 1024);
+ }
+
+ /**
+ * Decode obfuscated font from a InputStream, if the encryption is known.
+ *
+ * @param identifier The associated publication Identifier.
+ * @param inStream font input stream
+ * @param encryption {@link Encryption} object contains encryption type
+ * @return The InputStream containing the unencrypted resource.
+ */
+ public static InputStream decode(String identifier, InputStream inStream, Encryption encryption) {
+ if (identifier == null) {
+ System.out.println(TAG + " Couldn't get the publication identifier.");
+ return inStream;
+ }
+
+ if (!decoders.containsKey(encryption.getAlgorithm())) {
+ System.out.println(TAG + " " + encryption.getProfile() + " is encrypted but decoder cant handle it");
+ return inStream;
+ }
+ return decodeFont(identifier, inStream, decoders.get(encryption.getAlgorithm()), encryption.getAlgorithm());
+ }
+
+ /**
+ * Decode the given inputStream first X characters, depending of the obfuscation type.
+ *
+ * @param identifier The associated publication Identifier.
+ * @param inStream The input stream containing the data of an obfuscated font
+ * @param length The ObfuscationLength depending of the obfuscation type.
+ * @param algorithm type of algorithm
+ * @return The Deobfuscated InputStream.
+ */
+ private static InputStream decodeFont(String identifier, InputStream inStream, Integer length, String algorithm) {
+
+ byte[] publicationKey = null;
+ switch (algorithm) {
+ case "http://ns.adobe.com/pdf/enc#RC":
+ publicationKey = getHashKeyAdobe(identifier);
+ break;
+ case "http://www.idpf.org/2008/embedding":
+ publicationKey = getHashKeyIdpf(identifier);
+ break;
+ }
+ return deobfuscate(inStream, publicationKey, length);
+ }
+
+ /**
+ * Receive an obfuscated InputStream and return deabfuscated InputStream
+ *
+ * @param inStream The input stream containing the data of an obfuscated font
+ * @param publicationKey The publicationKey used to decode the X first characters.
+ * @param length The number of characters obfuscated at the first of the file.
+ * @return The Deobfuscated InputStream.
+ */
+ private static InputStream deobfuscate(InputStream inStream, byte[] publicationKey, Integer length) {
+ if (publicationKey == null) {
+ return inStream;
+ }
+ try {
+ byte[] bytes = new byte[inStream.available()];
+ int size = inStream.read(bytes);
+ int count = size > length ? length : size;
+ int pubKeyLength = publicationKey.length;
+ int i = 0;
+ while (i < count) {
+ bytes[i] = (byte) (bytes[i] ^ (publicationKey[i % pubKeyLength]));
+ i++;
+ }
+ return new ByteArrayInputStream(bytes);
+ } catch (IOException e) {
+ System.out.println(TAG + ".deobfuscate() " + e);
+ }
+
+ return null;
+ }
+
+ /**
+ * Create an EPUB font obfuscation key from one or more strings according to the rules
+ * defined in the EPUB 3 spec, 4.3 Generating the Obfuscation Key
+ * (http://www.idpf.org/epub/30/spec/epub30-ocf.html#fobfus-keygen)
+ * <p>
+ * Squeezes out any whitespace in each UID and then concatenates the result
+ * using single space characters as the separator.
+ *
+ * @param identifier The string to convert into a key.
+ * @return obfuscation key string
+ */
+ private static byte[] getHashKeyIdpf(String identifier) {
+ try {
+ MessageDigest crypt = MessageDigest.getInstance("SHA-1");
+ crypt.reset();
+ crypt.update(identifier.getBytes("UTF-8"));
+ return hexToBytes(byteToHex(crypt.digest()));
+ } catch (NoSuchAlgorithmException | UnsupportedEncodingException e) {
+ return null;
+ }
+ }
+
+ /**
+ * Generate the Hashkey used to salt the 1024 starting character of the Adobe font files.
+ *
+ * @param pubId The publication Identifier.
+ * @return The key's bytes array.
+ */
+ private static byte[] getHashKeyAdobe(String pubId) {
+ String cleanPubId = pubId.replaceAll("urn:uuid", "");
+ cleanPubId = cleanPubId.replaceAll("-", "");
+ cleanPubId = cleanPubId.replaceAll(":","");
+ return hexToBytes(cleanPubId);
+ }
+
+ /**
+ * Convert hexadecimal String to Bytes (UInt8) array.
+ *
+ * @param hexa The hexadecimal String
+ * @return The key's bytes array.
+ */
+ private static byte[] hexToBytes(String hexa) {
+ char[] hex = hexa.toCharArray();
+ int length = hex.length / 2;
+ byte[] raw = new byte[length];
+ for (int i = 0; i < length; i++) {
+ int high = Character.digit(hex[i * 2], 16);
+ int low = Character.digit(hex[i * 2 + 1], 16);
+ int value = (high << 4) | low;
+ if (value > 127)
+ value -= 256;
+ raw[i] = (byte) value;
+ }
+ return raw;
+ }
+
+ /**
+ * Convert Bytes array to hexadecimal String.
+ *
+ * @param hash bytes array.
+ * @return The hexadecimal String.
+ */
+ private static String byteToHex(byte[] hash) {
+ Formatter formatter = new Formatter();
+ for (byte b : hash) {
+ formatter.format("%02x", b);
+ }
+ String result = formatter.toString();
+ formatter.close();
+ return result;
+ }
+}
fnp / wl-app.git / blobdiff