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iText, a free Java-PDF library
/*
* $Id: PdfEncryption.java 3707 2009-02-20 18:47:51Z xlv $
*
* Copyright 2001-2006 Paulo Soares
*
* The contents of this file are subject to the Mozilla Public License Version 1.1
* (the "License"); you may not use this file except in compliance with the License.
* You may obtain a copy of the License at http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the License.
*
* The Original Code is 'iText, a free JAVA-PDF library'.
*
* The Initial Developer of the Original Code is Bruno Lowagie. Portions created by
* the Initial Developer are Copyright (C) 1999, 2000, 2001, 2002 by Bruno Lowagie.
* All Rights Reserved.
* Co-Developer of the code is Paulo Soares. Portions created by the Co-Developer
* are Copyright (C) 2000, 2001, 2002 by Paulo Soares. All Rights Reserved.
*
* Contributor(s): all the names of the contributors are added in the source code
* where applicable.
*
* Alternatively, the contents of this file may be used under the terms of the
* LGPL license (the "GNU LIBRARY GENERAL PUBLIC LICENSE"), in which case the
* provisions of LGPL are applicable instead of those above. If you wish to
* allow use of your version of this file only under the terms of the LGPL
* License and not to allow others to use your version of this file under
* the MPL, indicate your decision by deleting the provisions above and
* replace them with the notice and other provisions required by the LGPL.
* If you do not delete the provisions above, a recipient may use your version
* of this file under either the MPL or the GNU LIBRARY GENERAL PUBLIC LICENSE.
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the MPL as stated above or under the terms of the GNU
* Library General Public License as published by the Free Software Foundation;
* either version 2 of the License, or any later version.
*
* This library is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU Library general Public License for more
* details.
*
* If you didn't download this code from the following link, you should check if
* you aren't using an obsolete version:
* http://www.lowagie.com/iText/
*/
package com.lowagie.text.pdf;
import com.lowagie.text.pdf.crypto.ARCFOUREncryption;
import java.io.IOException;
import java.io.OutputStream;
import java.io.ByteArrayOutputStream;
import java.security.MessageDigest;
import java.security.cert.Certificate;
import com.lowagie.text.ExceptionConverter;
/**
*
* @author Paulo Soares ([email protected])
* @author Kazuya Ujihara
*/
public class PdfEncryption {
public static final int STANDARD_ENCRYPTION_40 = 2;
public static final int STANDARD_ENCRYPTION_128 = 3;
public static final int AES_128 = 4;
private static final byte[] pad = { (byte) 0x28, (byte) 0xBF, (byte) 0x4E,
(byte) 0x5E, (byte) 0x4E, (byte) 0x75, (byte) 0x8A, (byte) 0x41,
(byte) 0x64, (byte) 0x00, (byte) 0x4E, (byte) 0x56, (byte) 0xFF,
(byte) 0xFA, (byte) 0x01, (byte) 0x08, (byte) 0x2E, (byte) 0x2E,
(byte) 0x00, (byte) 0xB6, (byte) 0xD0, (byte) 0x68, (byte) 0x3E,
(byte) 0x80, (byte) 0x2F, (byte) 0x0C, (byte) 0xA9, (byte) 0xFE,
(byte) 0x64, (byte) 0x53, (byte) 0x69, (byte) 0x7A };
private static final byte[] salt = { (byte) 0x73, (byte) 0x41, (byte) 0x6c,
(byte) 0x54 };
private static final byte[] metadataPad = { (byte) 255, (byte) 255,
(byte) 255, (byte) 255 };
/** The encryption key for a particular object/generation */
byte key[];
/** The encryption key length for a particular object/generation */
int keySize;
/** The global encryption key */
byte mkey[];
/** Work area to prepare the object/generation bytes */
byte extra[] = new byte[5];
/** The message digest algorithm MD5 */
MessageDigest md5;
/** The encryption key for the owner */
byte ownerKey[] = new byte[32];
/** The encryption key for the user */
byte userKey[] = new byte[32];
/** The public key security handler for certificate encryption */
protected PdfPublicKeySecurityHandler publicKeyHandler = null;
int permissions;
byte documentID[];
static long seq = System.currentTimeMillis();
private int revision;
private ARCFOUREncryption arcfour = new ARCFOUREncryption();
/** The generic key length. It may be 40 or 128. */
private int keyLength;
private boolean encryptMetadata;
/**
* Indicates if the encryption is only necessary for embedded files.
* @since 2.1.3
*/
private boolean embeddedFilesOnly;
private int cryptoMode;
public PdfEncryption() {
try {
md5 = MessageDigest.getInstance("MD5");
} catch (Exception e) {
throw new ExceptionConverter(e);
}
publicKeyHandler = new PdfPublicKeySecurityHandler();
}
public PdfEncryption(PdfEncryption enc) {
this();
mkey = (byte[]) enc.mkey.clone();
ownerKey = (byte[]) enc.ownerKey.clone();
userKey = (byte[]) enc.userKey.clone();
permissions = enc.permissions;
if (enc.documentID != null)
documentID = (byte[]) enc.documentID.clone();
revision = enc.revision;
keyLength = enc.keyLength;
encryptMetadata = enc.encryptMetadata;
embeddedFilesOnly = enc.embeddedFilesOnly;
publicKeyHandler = enc.publicKeyHandler;
}
public void setCryptoMode(int mode, int kl) {
cryptoMode = mode;
encryptMetadata = (mode & PdfWriter.DO_NOT_ENCRYPT_METADATA) == 0;
embeddedFilesOnly = (mode & PdfWriter.EMBEDDED_FILES_ONLY) != 0;
mode &= PdfWriter.ENCRYPTION_MASK;
switch (mode) {
case PdfWriter.STANDARD_ENCRYPTION_40:
encryptMetadata = true;
embeddedFilesOnly = false;
keyLength = 40;
revision = STANDARD_ENCRYPTION_40;
break;
case PdfWriter.STANDARD_ENCRYPTION_128:
embeddedFilesOnly = false;
if (kl > 0)
keyLength = kl;
else
keyLength = 128;
revision = STANDARD_ENCRYPTION_128;
break;
case PdfWriter.ENCRYPTION_AES_128:
keyLength = 128;
revision = AES_128;
break;
default:
throw new IllegalArgumentException("No valid encryption mode");
}
}
public int getCryptoMode() {
return cryptoMode;
}
public boolean isMetadataEncrypted() {
return encryptMetadata;
}
/**
* Indicates if only the embedded files have to be encrypted.
* @return if true only the embedded files will be encrypted
* @since 2.1.3
*/
public boolean isEmbeddedFilesOnly() {
return embeddedFilesOnly;
}
/**
*/
private byte[] padPassword(byte userPassword[]) {
byte userPad[] = new byte[32];
if (userPassword == null) {
System.arraycopy(pad, 0, userPad, 0, 32);
} else {
System.arraycopy(userPassword, 0, userPad, 0, Math.min(
userPassword.length, 32));
if (userPassword.length < 32)
System.arraycopy(pad, 0, userPad, userPassword.length,
32 - userPassword.length);
}
return userPad;
}
/**
*/
private byte[] computeOwnerKey(byte userPad[], byte ownerPad[]) {
byte ownerKey[] = new byte[32];
byte digest[] = md5.digest(ownerPad);
if (revision == STANDARD_ENCRYPTION_128 || revision == AES_128) {
byte mkey[] = new byte[keyLength / 8];
// only use for the input as many bit as the key consists of
for (int k = 0; k < 50; ++k)
System.arraycopy(md5.digest(digest), 0, digest, 0, mkey.length);
System.arraycopy(userPad, 0, ownerKey, 0, 32);
for (int i = 0; i < 20; ++i) {
for (int j = 0; j < mkey.length; ++j)
mkey[j] = (byte) (digest[j] ^ i);
arcfour.prepareARCFOURKey(mkey);
arcfour.encryptARCFOUR(ownerKey);
}
} else {
arcfour.prepareARCFOURKey(digest, 0, 5);
arcfour.encryptARCFOUR(userPad, ownerKey);
}
return ownerKey;
}
/**
*
* ownerKey, documentID must be setup
*/
private void setupGlobalEncryptionKey(byte[] documentID, byte userPad[],
byte ownerKey[], int permissions) {
this.documentID = documentID;
this.ownerKey = ownerKey;
this.permissions = permissions;
// use variable keylength
mkey = new byte[keyLength / 8];
// fixed by ujihara in order to follow PDF reference
md5.reset();
md5.update(userPad);
md5.update(ownerKey);
byte ext[] = new byte[4];
ext[0] = (byte) permissions;
ext[1] = (byte) (permissions >> 8);
ext[2] = (byte) (permissions >> 16);
ext[3] = (byte) (permissions >> 24);
md5.update(ext, 0, 4);
if (documentID != null)
md5.update(documentID);
if (!encryptMetadata)
md5.update(metadataPad);
byte digest[] = new byte[mkey.length];
System.arraycopy(md5.digest(), 0, digest, 0, mkey.length);
// only use the really needed bits as input for the hash
if (revision == STANDARD_ENCRYPTION_128 || revision == AES_128) {
for (int k = 0; k < 50; ++k)
System.arraycopy(md5.digest(digest), 0, digest, 0, mkey.length);
}
System.arraycopy(digest, 0, mkey, 0, mkey.length);
}
/**
*
* mkey must be setup
*/
// use the revision to choose the setup method
private void setupUserKey() {
if (revision == STANDARD_ENCRYPTION_128 || revision == AES_128) {
md5.update(pad);
byte digest[] = md5.digest(documentID);
System.arraycopy(digest, 0, userKey, 0, 16);
for (int k = 16; k < 32; ++k)
userKey[k] = 0;
for (int i = 0; i < 20; ++i) {
for (int j = 0; j < mkey.length; ++j)
digest[j] = (byte) (mkey[j] ^ i);
arcfour.prepareARCFOURKey(digest, 0, mkey.length);
arcfour.encryptARCFOUR(userKey, 0, 16);
}
} else {
arcfour.prepareARCFOURKey(mkey);
arcfour.encryptARCFOUR(pad, userKey);
}
}
// gets keylength and revision and uses revision to choose the initial values
// for permissions
public void setupAllKeys(byte userPassword[], byte ownerPassword[],
int permissions) {
if (ownerPassword == null || ownerPassword.length == 0)
ownerPassword = md5.digest(createDocumentId());
permissions |= (revision == STANDARD_ENCRYPTION_128 || revision == AES_128) ? 0xfffff0c0
: 0xffffffc0;
permissions &= 0xfffffffc;
// PDF reference 3.5.2 Standard Security Handler, Algorithm 3.3-1
// If there is no owner password, use the user password instead.
byte userPad[] = padPassword(userPassword);
byte ownerPad[] = padPassword(ownerPassword);
this.ownerKey = computeOwnerKey(userPad, ownerPad);
documentID = createDocumentId();
setupByUserPad(this.documentID, userPad, this.ownerKey, permissions);
}
public static byte[] createDocumentId() {
MessageDigest md5;
try {
md5 = MessageDigest.getInstance("MD5");
} catch (Exception e) {
throw new ExceptionConverter(e);
}
long time = System.currentTimeMillis();
long mem = Runtime.getRuntime().freeMemory();
String s = time + "+" + mem + "+" + (seq++);
return md5.digest(s.getBytes());
}
/**
*/
public void setupByUserPassword(byte[] documentID, byte userPassword[],
byte ownerKey[], int permissions) {
setupByUserPad(documentID, padPassword(userPassword), ownerKey,
permissions);
}
/**
*/
private void setupByUserPad(byte[] documentID, byte userPad[],
byte ownerKey[], int permissions) {
setupGlobalEncryptionKey(documentID, userPad, ownerKey, permissions);
setupUserKey();
}
/**
*/
public void setupByOwnerPassword(byte[] documentID, byte ownerPassword[],
byte userKey[], byte ownerKey[], int permissions) {
setupByOwnerPad(documentID, padPassword(ownerPassword), userKey,
ownerKey, permissions);
}
private void setupByOwnerPad(byte[] documentID, byte ownerPad[],
byte userKey[], byte ownerKey[], int permissions) {
byte userPad[] = computeOwnerKey(ownerKey, ownerPad); // userPad will
// be set in
// this.ownerKey
setupGlobalEncryptionKey(documentID, userPad, ownerKey, permissions); // step
// 3
setupUserKey();
}
public void setupByEncryptionKey(byte[] key, int keylength) {
mkey = new byte[keylength / 8];
System.arraycopy(key, 0, mkey, 0, mkey.length);
}
public void setHashKey(int number, int generation) {
md5.reset(); // added by ujihara
extra[0] = (byte) number;
extra[1] = (byte) (number >> 8);
extra[2] = (byte) (number >> 16);
extra[3] = (byte) generation;
extra[4] = (byte) (generation >> 8);
md5.update(mkey);
md5.update(extra);
if (revision == AES_128)
md5.update(salt);
key = md5.digest();
keySize = mkey.length + 5;
if (keySize > 16)
keySize = 16;
}
public static PdfObject createInfoId(byte id[]) {
ByteBuffer buf = new ByteBuffer(90);
buf.append('[').append('<');
for (int k = 0; k < 16; ++k)
buf.appendHex(id[k]);
buf.append('>').append('<');
id = createDocumentId();
for (int k = 0; k < 16; ++k)
buf.appendHex(id[k]);
buf.append('>').append(']');
return new PdfLiteral(buf.toByteArray());
}
public PdfDictionary getEncryptionDictionary() {
PdfDictionary dic = new PdfDictionary();
if (publicKeyHandler.getRecipientsSize() > 0) {
PdfArray recipients = null;
dic.put(PdfName.FILTER, PdfName.PUBSEC);
dic.put(PdfName.R, new PdfNumber(revision));
try {
recipients = publicKeyHandler.getEncodedRecipients();
} catch (Exception f) {
throw new ExceptionConverter(f);
}
if (revision == STANDARD_ENCRYPTION_40) {
dic.put(PdfName.V, new PdfNumber(1));
dic.put(PdfName.SUBFILTER, PdfName.ADBE_PKCS7_S4);
dic.put(PdfName.RECIPIENTS, recipients);
} else if (revision == STANDARD_ENCRYPTION_128 && encryptMetadata) {
dic.put(PdfName.V, new PdfNumber(2));
dic.put(PdfName.LENGTH, new PdfNumber(128));
dic.put(PdfName.SUBFILTER, PdfName.ADBE_PKCS7_S4);
dic.put(PdfName.RECIPIENTS, recipients);
} else {
dic.put(PdfName.R, new PdfNumber(AES_128));
dic.put(PdfName.V, new PdfNumber(4));
dic.put(PdfName.SUBFILTER, PdfName.ADBE_PKCS7_S5);
PdfDictionary stdcf = new PdfDictionary();
stdcf.put(PdfName.RECIPIENTS, recipients);
if (!encryptMetadata)
stdcf.put(PdfName.ENCRYPTMETADATA, PdfBoolean.PDFFALSE);
if (revision == AES_128)
stdcf.put(PdfName.CFM, PdfName.AESV2);
else
stdcf.put(PdfName.CFM, PdfName.V2);
PdfDictionary cf = new PdfDictionary();
cf.put(PdfName.DEFAULTCRYPTFILTER, stdcf);
dic.put(PdfName.CF, cf);if (embeddedFilesOnly) {
dic.put(PdfName.EFF, PdfName.DEFAULTCRYPTFILTER);
dic.put(PdfName.STRF, PdfName.IDENTITY);
dic.put(PdfName.STMF, PdfName.IDENTITY);
}
else {
dic.put(PdfName.STRF, PdfName.DEFAULTCRYPTFILTER);
dic.put(PdfName.STMF, PdfName.DEFAULTCRYPTFILTER);
}
}
MessageDigest md = null;
byte[] encodedRecipient = null;
try {
md = MessageDigest.getInstance("SHA-1");
md.update(publicKeyHandler.getSeed());
for (int i = 0; i < publicKeyHandler.getRecipientsSize(); i++) {
encodedRecipient = publicKeyHandler.getEncodedRecipient(i);
md.update(encodedRecipient);
}
if (!encryptMetadata)
md.update(new byte[] { (byte) 255, (byte) 255, (byte) 255,
(byte) 255 });
} catch (Exception f) {
throw new ExceptionConverter(f);
}
byte[] mdResult = md.digest();
setupByEncryptionKey(mdResult, keyLength);
} else {
dic.put(PdfName.FILTER, PdfName.STANDARD);
dic.put(PdfName.O, new PdfLiteral(PdfContentByte
.escapeString(ownerKey)));
dic.put(PdfName.U, new PdfLiteral(PdfContentByte
.escapeString(userKey)));
dic.put(PdfName.P, new PdfNumber(permissions));
dic.put(PdfName.R, new PdfNumber(revision));
if (revision == STANDARD_ENCRYPTION_40) {
dic.put(PdfName.V, new PdfNumber(1));
} else if (revision == STANDARD_ENCRYPTION_128 && encryptMetadata) {
dic.put(PdfName.V, new PdfNumber(2));
dic.put(PdfName.LENGTH, new PdfNumber(128));
} else {
if (!encryptMetadata)
dic.put(PdfName.ENCRYPTMETADATA, PdfBoolean.PDFFALSE);
dic.put(PdfName.R, new PdfNumber(AES_128));
dic.put(PdfName.V, new PdfNumber(4));
dic.put(PdfName.LENGTH, new PdfNumber(128));
PdfDictionary stdcf = new PdfDictionary();
stdcf.put(PdfName.LENGTH, new PdfNumber(16));
if (embeddedFilesOnly) {
stdcf.put(PdfName.AUTHEVENT, PdfName.EFOPEN);
dic.put(PdfName.EFF, PdfName.STDCF);
dic.put(PdfName.STRF, PdfName.IDENTITY);
dic.put(PdfName.STMF, PdfName.IDENTITY);
}
else {
stdcf.put(PdfName.AUTHEVENT, PdfName.DOCOPEN);
dic.put(PdfName.STRF, PdfName.STDCF);
dic.put(PdfName.STMF, PdfName.STDCF);
}
if (revision == AES_128)
stdcf.put(PdfName.CFM, PdfName.AESV2);
else
stdcf.put(PdfName.CFM, PdfName.V2);
PdfDictionary cf = new PdfDictionary();
cf.put(PdfName.STDCF, stdcf);
dic.put(PdfName.CF, cf);
}
}
return dic;
}
public PdfObject getFileID() {
return createInfoId(documentID);
}
public OutputStreamEncryption getEncryptionStream(OutputStream os) {
return new OutputStreamEncryption(os, key, 0, keySize, revision);
}
public int calculateStreamSize(int n) {
if (revision == AES_128)
return (n & 0x7ffffff0) + 32;
else
return n;
}
public byte[] encryptByteArray(byte[] b) {
try {
ByteArrayOutputStream ba = new ByteArrayOutputStream();
OutputStreamEncryption os2 = getEncryptionStream(ba);
os2.write(b);
os2.finish();
return ba.toByteArray();
} catch (IOException ex) {
throw new ExceptionConverter(ex);
}
}
public StandardDecryption getDecryptor() {
return new StandardDecryption(key, 0, keySize, revision);
}
public byte[] decryptByteArray(byte[] b) {
try {
ByteArrayOutputStream ba = new ByteArrayOutputStream();
StandardDecryption dec = getDecryptor();
byte[] b2 = dec.update(b, 0, b.length);
if (b2 != null)
ba.write(b2);
b2 = dec.finish();
if (b2 != null)
ba.write(b2);
return ba.toByteArray();
} catch (IOException ex) {
throw new ExceptionConverter(ex);
}
}
public void addRecipient(Certificate cert, int permission) {
documentID = createDocumentId();
publicKeyHandler.addRecipient(new PdfPublicKeyRecipient(cert,
permission));
}
public byte[] computeUserPassword(byte[] ownerPassword) {
byte[] userPad = computeOwnerKey(ownerKey, padPassword(ownerPassword));
for (int i = 0; i < userPad.length; i++) {
boolean match = true;
for (int j = 0; j < userPad.length - i; j++) {
if (userPad[i + j] != pad[j]) {
match = false;
break;
}
}
if (!match) continue;
byte[] userPassword = new byte[i];
System.arraycopy(userPad, 0, userPassword, 0, i);
return userPassword;
}
return userPad;
}
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