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The Apache PDFBox library is an open source Java tool for working with PDF documents.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (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.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.pdfbox.pdmodel.encryption;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.security.AlgorithmParameterGenerator;
import java.security.AlgorithmParameters;
import java.security.GeneralSecurityException;
import java.security.InvalidKeyException;
import java.security.KeyStoreException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.SecureRandom;
import java.security.cert.CertificateEncodingException;
import java.security.cert.X509Certificate;
import java.util.Collection;
import java.util.Iterator;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import org.apache.pdfbox.cos.COSArray;
import org.apache.pdfbox.cos.COSString;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.bouncycastle.asn1.ASN1InputStream;
import org.bouncycastle.asn1.ASN1ObjectIdentifier;
import org.bouncycastle.asn1.ASN1Primitive;
import org.bouncycastle.asn1.ASN1Set;
import org.bouncycastle.asn1.DEROctetString;
import org.bouncycastle.asn1.DEROutputStream;
import org.bouncycastle.asn1.DERSet;
import org.bouncycastle.asn1.cms.ContentInfo;
import org.bouncycastle.asn1.cms.EncryptedContentInfo;
import org.bouncycastle.asn1.cms.EnvelopedData;
import org.bouncycastle.asn1.cms.IssuerAndSerialNumber;
import org.bouncycastle.asn1.cms.KeyTransRecipientInfo;
import org.bouncycastle.asn1.cms.RecipientIdentifier;
import org.bouncycastle.asn1.cms.RecipientInfo;
import org.bouncycastle.asn1.pkcs.PKCSObjectIdentifiers;
import org.bouncycastle.asn1.x509.AlgorithmIdentifier;
import org.bouncycastle.asn1.x509.TBSCertificate;
import org.bouncycastle.cert.X509CertificateHolder;
import org.bouncycastle.cms.CMSEnvelopedData;
import org.bouncycastle.cms.CMSException;
import org.bouncycastle.cms.KeyTransRecipientId;
import org.bouncycastle.cms.RecipientId;
import org.bouncycastle.cms.RecipientInformation;
import org.bouncycastle.cms.jcajce.JceKeyTransEnvelopedRecipient;
/**
* This class implements the public key security handler described in the PDF specification.
*
* @see PublicKeyProtectionPolicy to see how to protect document with this security handler.
* @author Benoit Guillon
*/
public final class PublicKeySecurityHandler extends SecurityHandler
{
/** The filter name. */
public static final String FILTER = "Adobe.PubSec";
private static final String SUBFILTER = "adbe.pkcs7.s4";
private PublicKeyProtectionPolicy policy = null;
/**
* Constructor.
*/
public PublicKeySecurityHandler()
{
}
/**
* Constructor used for encryption.
*
* @param p The protection policy.
*/
public PublicKeySecurityHandler(PublicKeyProtectionPolicy p)
{
policy = p;
this.keyLength = policy.getEncryptionKeyLength();
}
/**
* Prepares everything to decrypt the document.
*
* @param encryption encryption dictionary, can be retrieved via
* {@link PDDocument#getEncryption()}
* @param documentIDArray document id which is returned via
* {@link org.apache.pdfbox.cos.COSDocument#getDocumentID()} (not used by
* this handler)
* @param decryptionMaterial Information used to decrypt the document.
*
* @throws IOException If there is an error accessing data. If verbose mode
* is enabled, the exception message will provide more details why the
* match wasn't successful.
*/
@Override
public void prepareForDecryption(PDEncryption encryption, COSArray documentIDArray,
DecryptionMaterial decryptionMaterial)
throws IOException
{
if (!(decryptionMaterial instanceof PublicKeyDecryptionMaterial))
{
throw new IOException(
"Provided decryption material is not compatible with the document");
}
setDecryptMetadata(encryption.isEncryptMetaData());
if (encryption.getLength() != 0)
{
this.keyLength = encryption.getLength();
}
PublicKeyDecryptionMaterial material = (PublicKeyDecryptionMaterial) decryptionMaterial;
try
{
boolean foundRecipient = false;
X509Certificate certificate = material.getCertificate();
X509CertificateHolder materialCert = null;
if (certificate != null)
{
materialCert = new X509CertificateHolder(certificate.getEncoded());
}
// the decrypted content of the enveloped data that match
// the certificate in the decryption material provided
byte[] envelopedData = null;
// the bytes of each recipient in the recipients array
byte[][] recipientFieldsBytes = new byte[encryption.getRecipientsLength()][];
int recipientFieldsLength = 0;
int i = 0;
StringBuilder extraInfo = new StringBuilder();
for (; i < encryption.getRecipientsLength(); i++)
{
COSString recipientFieldString = encryption.getRecipientStringAt(i);
byte[] recipientBytes = recipientFieldString.getBytes();
CMSEnvelopedData data = new CMSEnvelopedData(recipientBytes);
Collection recipCertificatesIt = data.getRecipientInfos()
.getRecipients();
int j = 0;
for (RecipientInformation ri : recipCertificatesIt)
{
// Impl: if a matching certificate was previously found it is an error,
// here we just don't care about it
RecipientId rid = ri.getRID();
if (!foundRecipient && rid.match(materialCert))
{
foundRecipient = true;
PrivateKey privateKey = (PrivateKey) material.getPrivateKey();
envelopedData = ri.getContent(new JceKeyTransEnvelopedRecipient(privateKey));
break;
}
j++;
if (certificate != null)
{
extraInfo.append('\n');
extraInfo.append(j);
extraInfo.append(": ");
if (rid instanceof KeyTransRecipientId)
{
appendCertInfo(extraInfo, (KeyTransRecipientId) rid, certificate, materialCert);
}
}
}
recipientFieldsBytes[i] = recipientBytes;
recipientFieldsLength += recipientBytes.length;
}
if (!foundRecipient || envelopedData == null)
{
throw new IOException("The certificate matches none of " + i
+ " recipient entries" + extraInfo.toString());
}
if (envelopedData.length != 24)
{
throw new IOException("The enveloped data does not contain 24 bytes");
}
// now envelopedData contains:
// - the 20 bytes seed
// - the 4 bytes of permission for the current user
byte[] accessBytes = new byte[4];
System.arraycopy(envelopedData, 20, accessBytes, 0, 4);
AccessPermission currentAccessPermission = new AccessPermission(accessBytes);
currentAccessPermission.setReadOnly();
setCurrentAccessPermission(currentAccessPermission);
// what we will put in the SHA1 = the seed + each byte contained in the recipients array
byte[] sha1Input = new byte[recipientFieldsLength + 20];
// put the seed in the sha1 input
System.arraycopy(envelopedData, 0, sha1Input, 0, 20);
// put each bytes of the recipients array in the sha1 input
int sha1InputOffset = 20;
for (byte[] recipientFieldsByte : recipientFieldsBytes)
{
System.arraycopy(recipientFieldsByte, 0, sha1Input, sha1InputOffset,
recipientFieldsByte.length);
sha1InputOffset += recipientFieldsByte.length;
}
MessageDigest md = MessageDigests.getSHA1();
byte[] mdResult = md.digest(sha1Input);
// we have the encryption key ...
encryptionKey = new byte[this.keyLength / 8];
System.arraycopy(mdResult, 0, encryptionKey, 0, this.keyLength / 8);
}
catch (CMSException e)
{
throw new IOException(e);
}
catch (KeyStoreException e)
{
throw new IOException(e);
}
catch (CertificateEncodingException e)
{
throw new IOException(e);
}
}
private void appendCertInfo(StringBuilder extraInfo, KeyTransRecipientId ktRid,
X509Certificate certificate, X509CertificateHolder materialCert)
{
BigInteger ridSerialNumber = ktRid.getSerialNumber();
if (ridSerialNumber != null)
{
String certSerial = "unknown";
BigInteger certSerialNumber = certificate.getSerialNumber();
if (certSerialNumber != null)
{
certSerial = certSerialNumber.toString(16);
}
extraInfo.append("serial-#: rid ");
extraInfo.append(ridSerialNumber.toString(16));
extraInfo.append(" vs. cert ");
extraInfo.append(certSerial);
extraInfo.append(" issuer: rid \'");
extraInfo.append(ktRid.getIssuer());
extraInfo.append("\' vs. cert \'");
extraInfo.append(materialCert == null ? "null" : materialCert.getIssuer());
extraInfo.append("\' ");
}
}
/**
* Prepare the document for encryption.
*
* @param doc The document that will be encrypted.
*
* @throws IOException If there is an error while encrypting.
*/
@Override
public void prepareDocumentForEncryption(PDDocument doc) throws IOException
{
if (keyLength == 256)
{
throw new IOException("256 bit key length is not supported yet for public key security");
}
try
{
PDEncryption dictionary = doc.getEncryption();
if (dictionary == null)
{
dictionary = new PDEncryption();
}
dictionary.setFilter(FILTER);
dictionary.setLength(this.keyLength);
dictionary.setVersion(2);
// remove CF, StmF, and StrF entries that may be left from a previous encryption
dictionary.removeV45filters();
dictionary.setSubFilter(SUBFILTER);
// create the 20 bytes seed
byte[] seed = new byte[20];
KeyGenerator key;
try
{
key = KeyGenerator.getInstance("AES");
}
catch (NoSuchAlgorithmException e)
{
// should never happen
throw new RuntimeException(e);
}
key.init(192, new SecureRandom());
SecretKey sk = key.generateKey();
System.arraycopy(sk.getEncoded(), 0, seed, 0, 20); // create the 20 bytes seed
byte[][] recipientsField = computeRecipientsField(seed);
dictionary.setRecipients(recipientsField);
int sha1InputLength = seed.length;
for(int j=0; j it = policy.getRecipientsIterator();
int i = 0;
while(it.hasNext())
{
PublicKeyRecipient recipient = it.next();
X509Certificate certificate = recipient.getX509();
int permission = recipient.getPermission().getPermissionBytesForPublicKey();
byte[] pkcs7input = new byte[24];
byte one = (byte)(permission);
byte two = (byte)(permission >>> 8);
byte three = (byte)(permission >>> 16);
byte four = (byte)(permission >>> 24);
System.arraycopy(seed, 0, pkcs7input, 0, 20); // put this seed in the pkcs7 input
pkcs7input[20] = four;
pkcs7input[21] = three;
pkcs7input[22] = two;
pkcs7input[23] = one;
ASN1Primitive obj = createDERForRecipient(pkcs7input, certificate);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DEROutputStream k = new DEROutputStream(baos);
k.writeObject(obj);
recipientsField[i] = baos.toByteArray();
i++;
}
return recipientsField;
}
private ASN1Primitive createDERForRecipient(byte[] in, X509Certificate cert)
throws IOException, GeneralSecurityException
{
String algorithm = "1.2.840.113549.3.2";
AlgorithmParameterGenerator apg;
KeyGenerator keygen;
Cipher cipher;
try
{
apg = AlgorithmParameterGenerator.getInstance(algorithm,
SecurityProvider.getProvider());
keygen = KeyGenerator.getInstance(algorithm, SecurityProvider.getProvider());
cipher = Cipher.getInstance(algorithm, SecurityProvider.getProvider());
}
catch (NoSuchAlgorithmException e)
{
// happens when using the command line app .jar file
throw new IOException("Could not find a suitable javax.crypto provider for algorithm " +
algorithm + "; possible reason: using an unsigned .jar file", e);
}
catch (NoSuchPaddingException e)
{
// should never happen, if this happens throw IOException instead
throw new RuntimeException("Could not find a suitable javax.crypto provider", e);
}
AlgorithmParameters parameters = apg.generateParameters();
ASN1InputStream input = new ASN1InputStream(parameters.getEncoded("ASN.1"));
ASN1Primitive object = input.readObject();
input.close();
keygen.init(128);
SecretKey secretkey = keygen.generateKey();
cipher.init(1, secretkey, parameters);
byte[] bytes = cipher.doFinal(in);
KeyTransRecipientInfo recipientInfo = computeRecipientInfo(cert, secretkey.getEncoded());
DERSet set = new DERSet(new RecipientInfo(recipientInfo));
AlgorithmIdentifier algorithmId = new AlgorithmIdentifier(new ASN1ObjectIdentifier(algorithm), object);
EncryptedContentInfo encryptedInfo =
new EncryptedContentInfo(PKCSObjectIdentifiers.data, algorithmId, new DEROctetString(bytes));
EnvelopedData enveloped = new EnvelopedData(null, set, encryptedInfo, (ASN1Set) null);
ContentInfo contentInfo = new ContentInfo(PKCSObjectIdentifiers.envelopedData, enveloped);
return contentInfo.toASN1Primitive();
}
private KeyTransRecipientInfo computeRecipientInfo(X509Certificate x509certificate, byte[] abyte0)
throws IOException, CertificateEncodingException, InvalidKeyException,
BadPaddingException, IllegalBlockSizeException
{
ASN1InputStream input = new ASN1InputStream(x509certificate.getTBSCertificate());
TBSCertificate certificate = TBSCertificate.getInstance(input.readObject());
input.close();
AlgorithmIdentifier algorithmId = certificate.getSubjectPublicKeyInfo().getAlgorithm();
IssuerAndSerialNumber serial = new IssuerAndSerialNumber(
certificate.getIssuer(),
certificate.getSerialNumber().getValue());
Cipher cipher;
try
{
cipher = Cipher.getInstance(algorithmId.getAlgorithm().getId(),
SecurityProvider.getProvider());
}
catch (NoSuchAlgorithmException e)
{
// should never happen, if this happens throw IOException instead
throw new RuntimeException("Could not find a suitable javax.crypto provider", e);
}
catch (NoSuchPaddingException e)
{
// should never happen, if this happens throw IOException instead
throw new RuntimeException("Could not find a suitable javax.crypto provider", e);
}
cipher.init(1, x509certificate.getPublicKey());
DEROctetString octets = new DEROctetString(cipher.doFinal(abyte0));
RecipientIdentifier recipientId = new RecipientIdentifier(serial);
return new KeyTransRecipientInfo(recipientId, algorithmId, octets);
}
/**
* {@inheritDoc}
*/
@Override
public boolean hasProtectionPolicy()
{
return policy != null;
}
}