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* Copyright (c) 2003-2006, www.pdfbox.org
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package org.pdfbox.pdmodel.encryption;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import org.pdfbox.cos.COSArray;
import org.pdfbox.cos.COSString;
import org.pdfbox.encryption.ARCFour;
import org.pdfbox.exceptions.CryptographyException;
import org.pdfbox.pdmodel.PDDocument;
/**
*
* The class implements the standard security handler as decribed
* in the PDF specifications. This security handler protects document
* with password.
*
* @see StandardProtectionPolicy to see how to protect document with this security handler.
*
* @author <a href="mailto:ben@benlitchfield.com">Ben Litchfield</a>
* @author Benoit Guillon (benoit.guillon@snv.jussieu.fr)
*
* @version $Revision: 1.3 $
*/
public class StandardSecurityHandler extends SecurityHandler
{
/**
* Type of security handler.
*/
public static final String FILTER = "Standard";
private static final int DEFAULT_VERSION = 1;
private static final int DEFAULT_REVISION = 3;
private int revision = DEFAULT_REVISION;
private StandardProtectionPolicy policy;
private ARCFour rc4 = new ARCFour();
/**
* Protection policy class for this handler.
*/
public static final Class PROTECTION_POLICY_CLASS = StandardProtectionPolicy.class;
/**
* Standard padding for encryption.
*/
public static final byte[] ENCRYPT_PADDING =
{
(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
};
/**
* Constructor.
*/
public StandardSecurityHandler()
{
}
/**
* Constructor used for encryption.
*
* @param p The protection policy.
*/
public StandardSecurityHandler(StandardProtectionPolicy p)
{
policy = p;
keyLength = policy.getEncryptionKeyLength();
}
/**
* Computes the version number of the StandardSecurityHandler
* regarding the encryption key length.
* See PDF Spec 1.6 p 93
*
* @return The computed cersion number.
*/
private int computeVersionNumber()
{
if(keyLength == 40)
{
return DEFAULT_VERSION;
}
return 2;
}
/**
* Computes the revision version of the StandardSecurityHandler to
* use regarding the version number and the permissions bits set.
* See PDF Spec 1.6 p98
*
* @return The computed revision number.
*/
private int computeRevisionNumber()
{
if(version == 2
&& !policy.getPermissions().canFillInForm()
&& !policy.getPermissions().canExtractForAccessibility()
&& !policy.getPermissions().canPrintDegraded() )
{
return 2;
}
return 3;
}
/**
* Decrypt the document.
*
* @param doc The document to be decrypted.
* @param decryptionMaterial Information used to decrypt the document.
*
* @throws IOException If there is an error accessing data.
* @throws CryptographyException If there is an error with decryption.
*/
public void decryptDocument(PDDocument doc, DecryptionMaterial decryptionMaterial)
throws CryptographyException, IOException
{
document = doc;
PDEncryptionDictionary dictionary = document.getEncryptionDictionary();
if(!(decryptionMaterial instanceof StandardDecryptionMaterial))
{
throw new CryptographyException("Provided decryption material is not compatible with the document");
}
StandardDecryptionMaterial material = (StandardDecryptionMaterial)decryptionMaterial;
String password = material.getPassword();
if(password == null)
{
password = "";
}
int dicPermissions = dictionary.getPermissions();
int dicRevision = dictionary.getRevision();
int dicLength = dictionary.getLength()/8;
COSString id = (COSString)document.getDocument().getDocumentID().getObject( 0 );
byte[] u = dictionary.getUserKey();
byte[] o = dictionary.getOwnerKey();
boolean isUserPassword =
isUserPassword(
password.getBytes(),
u,
o,
dicPermissions,
id.getBytes(),
dicRevision,
dicLength );
boolean isOwnerPassword =
isOwnerPassword(
password.getBytes(),
u,
o,
dicPermissions,
id.getBytes(),
dicRevision,
dicLength );
if( isUserPassword )
{
encryptionKey =
computeEncryptedKey(
password.getBytes(),
o,
dicPermissions,
id.getBytes(),
dicRevision,
dicLength );
}
else if( isOwnerPassword )
{
byte[] computedUserPassword = getUserPassword(password.getBytes(),o,dicRevision,dicLength );
encryptionKey =
computeEncryptedKey(
computedUserPassword,
o,
dicPermissions,
id.getBytes(),
dicRevision,
dicLength );
}
else
{
throw new CryptographyException(
"Error: The supplied password does not match either the owner or user password in the document." );
}
this.proceedDecryption();
}
/**
* Prepare document for encryption.
*
* @param doc The documeent to encrypt.
*
* @throws IOException If there is an error accessing data.
* @throws CryptographyException If there is an error with decryption.
*/
public void prepareDocumentForEncryption(PDDocument doc) throws CryptographyException, IOException
{
document = doc;
PDEncryptionDictionary encryptionDictionary = document.getEncryptionDictionary();
if(encryptionDictionary == null)
{
encryptionDictionary = new PDEncryptionDictionary();
}
version = computeVersionNumber();
revision = computeRevisionNumber();
encryptionDictionary.setFilter(FILTER);
encryptionDictionary.setVersion(version);
encryptionDictionary.setRevision(revision);
encryptionDictionary.setLength(keyLength);
String ownerPassword = policy.getOwnerPassword();
String userPassword = policy.getUserPassword();
if( ownerPassword == null )
{
ownerPassword = "";
}
if( userPassword == null )
{
userPassword = "";
}
int permissionInt = policy.getPermissions().getPermissionBytes();
encryptionDictionary.setPermissions(permissionInt);
int length = keyLength/8;
COSArray idArray = document.getDocument().getDocumentID();
//check if the document has an id yet. If it does not then
//generate one
if( idArray == null || idArray.size() < 2 )
{
idArray = new COSArray();
try
{
MessageDigest md = MessageDigest.getInstance( "MD5" );
BigInteger time = BigInteger.valueOf( System.currentTimeMillis() );
md.update( time.toByteArray() );
md.update( ownerPassword.getBytes() );
md.update( userPassword.getBytes() );
md.update( document.getDocument().toString().getBytes() );
byte[] id = md.digest( this.toString().getBytes() );
COSString idString = new COSString();
idString.append( id );
idArray.add( idString );
idArray.add( idString );
document.getDocument().setDocumentID( idArray );
}
catch( NoSuchAlgorithmException e )
{
throw new CryptographyException( e );
}
catch(IOException e )
{
throw new CryptographyException( e );
}
}
COSString id = (COSString)idArray.getObject( 0 );
byte[] o = computeOwnerPassword(
ownerPassword.getBytes("ISO-8859-1"),
userPassword.getBytes("ISO-8859-1"), revision, length);
byte[] u = computeUserPassword(
userPassword.getBytes("ISO-8859-1"),
o, permissionInt, id.getBytes(), revision, length);
encryptionKey = computeEncryptedKey(
userPassword.getBytes("ISO-8859-1"), o, permissionInt, id.getBytes(), revision, length);
encryptionDictionary.setOwnerKey(o);
encryptionDictionary.setUserKey(u);
document.setEncryptionDictionary( encryptionDictionary );
document.getDocument().setEncryptionDictionary(encryptionDictionary.getCOSDictionary());
}
/**
* Check for owner password.
*
* @param ownerPassword The owner password.
* @param u The u entry of the encryption dictionary.
* @param o The o entry of the encryption dictionary.
* @param permissions The set of permissions on the document.
* @param id The document id.
* @param encRevision The encryption algorithm revision.
* @param length The encryption key length.
*
* @return True If the ownerPassword param is the owner password.
*
* @throws CryptographyException If there is an error during encryption.
* @throws IOException If there is an error accessing data.
*/
public final boolean isOwnerPassword(
byte[] ownerPassword,
byte[] u,
byte[] o,
int permissions,
byte[] id,
int encRevision,
int length)
throws CryptographyException, IOException
{
byte[] userPassword = getUserPassword( ownerPassword, o, encRevision, length );
return isUserPassword( userPassword, u, o, permissions, id, encRevision, length );
}
/**
* Get the user password based on the owner password.
*
* @param ownerPassword The plaintext owner password.
* @param o The o entry of the encryption dictionary.
* @param encRevision The encryption revision number.
* @param length The key length.
*
* @return The u entry of the encryption dictionary.
*
* @throws CryptographyException If there is an error generating the user password.
* @throws IOException If there is an error accessing data while generating the user password.
*/
public final byte[] getUserPassword(
byte[] ownerPassword,
byte[] o,
int encRevision,
long length )
throws CryptographyException, IOException
{
try
{
ByteArrayOutputStream result = new ByteArrayOutputStream();
//3.3 STEP 1
byte[] ownerPadded = truncateOrPad( ownerPassword );
//3.3 STEP 2
MessageDigest md = MessageDigest.getInstance( "MD5" );
md.update( ownerPadded );
byte[] digest = md.digest();
//3.3 STEP 3
if( encRevision == 3 || encRevision == 4 )
{
for( int i=0; i<50; i++ )
{
md.reset();
md.update( digest );
digest = md.digest();
}
}
if( encRevision == 2 && length != 5 )
{
throw new CryptographyException(
"Error: Expected length=5 actual=" + length );
}
//3.3 STEP 4
byte[] rc4Key = new byte[ (int)length ];
System.arraycopy( digest, 0, rc4Key, 0, (int)length );
//3.7 step 2
if( encRevision == 2 )
{
rc4.setKey( rc4Key );
rc4.write( o, result );
}
else if( encRevision == 3 || encRevision == 4)
{
/**
byte[] iterationKey = new byte[ rc4Key.length ];
byte[] dataToEncrypt = o;
for( int i=19; i>=0; i-- )
{
System.arraycopy( rc4Key, 0, iterationKey, 0, rc4Key.length );
for( int j=0; j< iterationKey.length; j++ )
{
iterationKey[j] = (byte)(iterationKey[j] ^ (byte)i);
}
rc4.setKey( iterationKey );
rc4.write( dataToEncrypt, result );
dataToEncrypt = result.toByteArray();
result.reset();
}
result.write( dataToEncrypt, 0, dataToEncrypt.length );
*/
byte[] iterationKey = new byte[ rc4Key.length ];
byte[] otemp = new byte[ o.length ]; //sm
System.arraycopy( o, 0, otemp, 0, o.length ); //sm
rc4.write( o, result);//sm
for( int i=19; i>=0; i-- )
{
System.arraycopy( rc4Key, 0, iterationKey, 0, rc4Key.length );
for( int j=0; j< iterationKey.length; j++ )
{
iterationKey[j] = (byte)(iterationKey[j] ^ (byte)i);
}
rc4.setKey( iterationKey );
result.reset(); //sm
rc4.write( otemp, result ); //sm
otemp = result.toByteArray(); //sm
}
}
return result.toByteArray();
}
catch( NoSuchAlgorithmException e )
{
throw new CryptographyException( e );
}
}
/**
* Compute the encryption key.
*
* @param password The password to compute the encrypted key.
* @param o The o entry of the encryption dictionary.
* @param permissions The permissions for the document.
* @param id The document id.
* @param encRevision The revision of the encryption algorithm.
* @param length The length of the encryption key.
*
* @return The encrypted key bytes.
*
* @throws CryptographyException If there is an error with encryption.
*/
public final byte[] computeEncryptedKey(
byte[] password,
byte[] o,
int permissions,
byte[] id,
int encRevision,
int length )
throws CryptographyException
{
byte[] result = new byte[ length ];
try
{
//PDFReference 1.4 pg 78
//step1
byte[] padded = truncateOrPad( password );
//step 2
MessageDigest md = MessageDigest.getInstance("MD5");
md.update( padded );
//step 3
md.update( o );
//step 4
byte zero = (byte)(permissions >>> 0);
byte one = (byte)(permissions >>> 8);
byte two = (byte)(permissions >>> 16);
byte three = (byte)(permissions >>> 24);
md.update( zero );
md.update( one );
md.update( two );
md.update( three );
//step 5
md.update( id );
byte[] digest = md.digest();
//step 6
if( encRevision == 3 || encRevision == 4)
{
for( int i=0; i<50; i++ )
{
md.reset();
md.update( digest, 0, length );
digest = md.digest();
}
}
//step 7
if( encRevision == 2 && length != 5 )
{
throw new CryptographyException(
"Error: length should be 5 when revision is two actual=" + length );
}
System.arraycopy( digest, 0, result, 0, length );
}
catch( NoSuchAlgorithmException e )
{
throw new CryptographyException( e );
}
return result;
}
/**
* This will compute the user password hash.
*
* @param password The plain text password.
* @param o The owner password hash.
* @param permissions The document permissions.
* @param id The document id.
* @param encRevision The revision of the encryption.
* @param length The length of the encryption key.
*
* @return The user password.
*
* @throws CryptographyException If there is an error computing the user password.
* @throws IOException If there is an IO error.
*/
public final byte[] computeUserPassword(
byte[] password,
byte[] o,
int permissions,
byte[] id,
int encRevision,
int length )
throws CryptographyException, IOException
{
ByteArrayOutputStream result = new ByteArrayOutputStream();
//STEP 1
byte[] encryptionKey = computeEncryptedKey( password, o, permissions, id, encRevision, length );
if( encRevision == 2 )
{
//STEP 2
rc4.setKey( encryptionKey );
rc4.write( ENCRYPT_PADDING, result );
}
else if( encRevision == 3 || encRevision == 4 )
{
try
{
//STEP 2
MessageDigest md = MessageDigest.getInstance("MD5");
//md.update( truncateOrPad( password ) );
md.update( ENCRYPT_PADDING );
//STEP 3
md.update( id );
result.write( md.digest() );
//STEP 4 and 5
byte[] iterationKey = new byte[ encryptionKey.length ];
for( int i=0; i<20; i++ )
{
System.arraycopy( encryptionKey, 0, iterationKey, 0, iterationKey.length );
for( int j=0; j< iterationKey.length; j++ )
{
iterationKey[j] = (byte)(iterationKey[j] ^ i);
}
rc4.setKey( iterationKey );
ByteArrayInputStream input = new ByteArrayInputStream( result.toByteArray() );
result.reset();
rc4.write( input, result );
}
//step 6
byte[] finalResult = new byte[32];
System.arraycopy( result.toByteArray(), 0, finalResult, 0, 16 );
System.arraycopy( ENCRYPT_PADDING, 0, finalResult, 16, 16 );
result.reset();
result.write( finalResult );
}
catch( NoSuchAlgorithmException e )
{
throw new CryptographyException( e );
}
}
return result.toByteArray();
}
/**
* Compute the owner entry in the encryption dictionary.
*
* @param ownerPassword The plaintext owner password.
* @param userPassword The plaintext user password.
* @param encRevision The revision number of the encryption algorithm.
* @param length The length of the encryption key.
*
* @return The o entry of the encryption dictionary.
*
* @throws CryptographyException If there is an error with encryption.
* @throws IOException If there is an error accessing data.
*/
public final byte[] computeOwnerPassword(
byte[] ownerPassword,
byte[] userPassword,
int encRevision,
int length )
throws CryptographyException, IOException
{
try
{
//STEP 1
byte[] ownerPadded = truncateOrPad( ownerPassword );
//STEP 2
MessageDigest md = MessageDigest.getInstance( "MD5" );
md.update( ownerPadded );
byte[] digest = md.digest();
//STEP 3
if( encRevision == 3 || encRevision == 4)
{
for( int i=0; i<50; i++ )
{
md.reset();
md.update( digest, 0, length );
digest = md.digest();
}
}
if( encRevision == 2 && length != 5 )
{
throw new CryptographyException(
"Error: Expected length=5 actual=" + length );
}
//STEP 4
byte[] rc4Key = new byte[ length ];
System.arraycopy( digest, 0, rc4Key, 0, length );
//STEP 5
byte[] paddedUser = truncateOrPad( userPassword );
//STEP 6
rc4.setKey( rc4Key );
ByteArrayOutputStream crypted = new ByteArrayOutputStream();
rc4.write( new ByteArrayInputStream( paddedUser ), crypted );
//STEP 7
if( encRevision == 3 || encRevision == 4 )
{
byte[] iterationKey = new byte[ rc4Key.length ];
for( int i=1; i<20; i++ )
{
System.arraycopy( rc4Key, 0, iterationKey, 0, rc4Key.length );
for( int j=0; j< iterationKey.length; j++ )
{
iterationKey[j] = (byte)(iterationKey[j] ^ (byte)i);
}
rc4.setKey( iterationKey );
ByteArrayInputStream input = new ByteArrayInputStream( crypted.toByteArray() );
crypted.reset();
rc4.write( input, crypted );
}
}
//STEP 8
return crypted.toByteArray();
}
catch( NoSuchAlgorithmException e )
{
throw new CryptographyException( e.getMessage() );
}
}
/**
* This will take the password and truncate or pad it as necessary.
*
* @param password The password to pad or truncate.
*
* @return The padded or truncated password.
*/
private final byte[] truncateOrPad( byte[] password )
{
byte[] padded = new byte[ ENCRYPT_PADDING.length ];
int bytesBeforePad = Math.min( password.length, padded.length );
System.arraycopy( password, 0, padded, 0, bytesBeforePad );
System.arraycopy( ENCRYPT_PADDING, 0, padded, bytesBeforePad, ENCRYPT_PADDING.length-bytesBeforePad );
return padded;
}
/**
* Check if a plaintext password is the user password.
*
* @param password The plaintext password.
* @param u The u entry of the encryption dictionary.
* @param o The o entry of the encryption dictionary.
* @param permissions The permissions set in the the PDF.
* @param id The document id used for encryption.
* @param encRevision The revision of the encryption algorithm.
* @param length The length of the encryption key.
*
* @return true If the plaintext password is the user password.
*
* @throws CryptographyException If there is an error during encryption.
* @throws IOException If there is an error accessing data.
*/
public final boolean isUserPassword(
byte[] password,
byte[] u,
byte[] o,
int permissions,
byte[] id,
int encRevision,
int length)
throws CryptographyException, IOException
{
boolean matches = false;
//STEP 1
byte[] computedValue = computeUserPassword( password, o, permissions, id, encRevision, length );
if( encRevision == 2 )
{
//STEP 2
matches = arraysEqual( u, computedValue );
}
else if( encRevision == 3 || encRevision == 4 )
{
//STEP 2
matches = arraysEqual( u, computedValue, 16 );
}
return matches;
}
private static final boolean arraysEqual( byte[] first, byte[] second, int count )
{
boolean equal = first.length >= count && second.length >= count;
for( int i=0; i<count && equal; i++ )
{
equal = first[i] == second[i];
}
return equal;
}
/**
* This will compare two byte[] for equality.
*
* @param first The first byte array.
* @param second The second byte array.
*
* @return true If the arrays contain the exact same data.
*/
private static final boolean arraysEqual( byte[] first, byte[] second )
{
boolean equal = first.length == second.length;
for( int i=0; i<first.length && equal; i++ )
{
equal = first[i] == second[i];
}
return equal;
}
}