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The Bouncy Castle Java APIs for the OpenPGP Protocol. The APIs are designed primarily to be used in conjunction with the BC FIPS provider. The APIs may also be used with other providers although if being used in a FIPS context it is the responsibility of the user to ensure that any other providers used are FIPS certified and used appropriately.
package org.bouncycastle.openpgp.operator;
import java.security.SecureRandom;
import org.bouncycastle.bcpg.AEADUtils;
import org.bouncycastle.bcpg.ContainedPacket;
import org.bouncycastle.bcpg.S2K;
import org.bouncycastle.bcpg.SymmetricKeyAlgorithmTags;
import org.bouncycastle.bcpg.SymmetricKeyEncSessionPacket;
import org.bouncycastle.openpgp.PGPException;
import org.bouncycastle.util.Arrays;
/**
* PGP style PBE encryption method.
*
* A pass phrase is used to generate an encryption key using the PGP {@link S2K string-to-key}
* method. This class always uses the {@link S2K#SALTED_AND_ITERATED salted and iterated form of the
* S2K algorithm}.
*
* Note that the iteration count provided to this method is a single byte as described by the
* {@link S2K} algorithm, and the actual iteration count ranges exponentially from
* 0x01 == 1088 to 0xFF == 65,011,712.
*
*/
public abstract class PBEKeyEncryptionMethodGenerator
extends PGPKeyEncryptionMethodGenerator
{
private char[] passPhrase;
private PGPDigestCalculator s2kDigestCalculator;
private S2K s2k;
private SecureRandom random;
private int s2kCount;
private int wrapAlg = -1;
/**
* Construct a PBE key generator using the default iteration count (0x60 == 65536
* iterations).
*
* @param passPhrase the pass phrase to encrypt with.
* @param s2kDigestCalculator a digest calculator to use in the string-to-key function.
*/
protected PBEKeyEncryptionMethodGenerator(
char[] passPhrase,
PGPDigestCalculator s2kDigestCalculator)
{
this(passPhrase, s2kDigestCalculator, 0x60);
}
/**
* Construct a PBE key generator using Argon2 as S2K mechanism.
*
* @param passPhrase passphrase
* @param params argon2 parameters
*/
protected PBEKeyEncryptionMethodGenerator(
char[] passPhrase, S2K.Argon2Params params)
{
this.passPhrase = passPhrase;
this.s2k = new S2K(params);
}
/**
* Construct a PBE key generator using a specific iteration level.
*
* @param passPhrase the pass phrase to encrypt with.
* @param s2kDigestCalculator a digest calculator to use in the string-to-key function.
* @param s2kCount a single byte {@link S2K} iteration count specifier, which is translated to
* an actual iteration count by the S2K class.
*/
protected PBEKeyEncryptionMethodGenerator(
char[] passPhrase,
PGPDigestCalculator s2kDigestCalculator,
int s2kCount)
{
this.passPhrase = passPhrase;
this.s2kDigestCalculator = s2kDigestCalculator;
if (s2kCount < 0 || s2kCount > 0xff)
{
throw new IllegalArgumentException("s2kCount value outside of range 0 to 255.");
}
this.s2kCount = s2kCount;
}
/**
* Sets a user defined source of randomness.
*
* If no SecureRandom is configured, a default SecureRandom will be used.
*
*
* @return the current generator.
*/
public PBEKeyEncryptionMethodGenerator setSecureRandom(SecureRandom random)
{
this.random = random;
return this;
}
/**
* Set a specific algorithm to be used where this PBE method generator is
* used to wrap a session key for encrypting data, rather than providing the
* encryption key for the data.
*
* The default wrapping algorithm is the same algorithm as the one specified for
* data encryption with the PGPEncryptedDataGenerator used.
*
*
* @return the current generator.
*/
public PBEKeyEncryptionMethodGenerator setSessionKeyWrapperAlgorithm(int wrapAlg)
{
this.wrapAlg = wrapAlg;
return this;
}
/**
* Return the key wrapping algorithm this PBE key method is associated with.
*
* @param defaultWrapAlg the default wrapping algorithm if none was set.
* @return the PBE method's wrapping algorithm, defaultWrapAlg is setSessionKeyWrapperAlgorithm was not called.
*/
public int getSessionKeyWrapperAlgorithm(int defaultWrapAlg)
{
if (wrapAlg < 0)
{
return defaultWrapAlg;
}
return wrapAlg;
}
/**
* Generate a key for a symmetric encryption algorithm using the PBE configuration in this
* method.
*
* @param encAlgorithm the {@link SymmetricKeyAlgorithmTags encryption algorithm} to generate
* the key for.
* @return the bytes of the generated key.
* @throws PGPException if an error occurs performing the string-to-key generation.
*/
public byte[] getKey(int encAlgorithm)
throws PGPException
{
if (s2k == null)
{
byte[] iv = new byte[8];
if (random == null)
{
random = new SecureRandom();
}
random.nextBytes(iv);
s2k = new S2K(s2kDigestCalculator.getAlgorithm(), iv, s2kCount);
}
return PGPUtil.makeKeyFromPassPhrase(s2kDigestCalculator, encAlgorithm, s2k, passPhrase);
}
@Override
public ContainedPacket generateV5(int kekAlgorithm, int aeadAlgorithm, byte[] sessionInfo)
throws PGPException
{
return generate(kekAlgorithm, sessionInfo);
// TODO: Implement v5 SKESK creation properly.
// return generateV5ESK(kekAlgorithm, aeadAlgorithm, sessionInfo);
}
@Override
public ContainedPacket generateV6(int kekAlgorithm, int aeadAlgorithm, byte[] sessionInfo)
throws PGPException
{
return generateV6ESK(kekAlgorithm, aeadAlgorithm, sessionInfo);
}
// If we use this method, roundtripping v5 AEAD is broken.
// TODO: Investigate
private ContainedPacket generateV5ESK(int kekAlgorithm, int aeadAlgorithm, byte[] sessionInfo)
throws PGPException
{
byte[] ikm = getKey(kekAlgorithm);
byte[] info = new byte[] {
(byte) 0xC3,
(byte) SymmetricKeyEncSessionPacket.VERSION_5,
(byte) kekAlgorithm,
(byte) aeadAlgorithm
};
byte[] iv = new byte[AEADUtils.getIVLength(aeadAlgorithm)];
random.nextBytes(iv);
int tagLen = AEADUtils.getAuthTagLength(aeadAlgorithm);
byte[] eskAndTag = getEskAndTag(kekAlgorithm, aeadAlgorithm, sessionInfo, ikm, iv, info);
byte[] esk = Arrays.copyOfRange(eskAndTag, 0, eskAndTag.length - tagLen);
byte[] tag = Arrays.copyOfRange(eskAndTag, esk.length, eskAndTag.length);
return SymmetricKeyEncSessionPacket.createV5Packet(kekAlgorithm, aeadAlgorithm, iv, s2k, esk, tag);
}
private ContainedPacket generateV6ESK(int kekAlgorithm, int aeadAlgorithm, byte[] sessionInfo)
throws PGPException
{
byte[] ikm = getKey(kekAlgorithm);
byte[] info = new byte[] {
(byte) 0xC3,
(byte) SymmetricKeyEncSessionPacket.VERSION_6,
(byte) kekAlgorithm,
(byte) aeadAlgorithm
};
byte[] kek = generateV6KEK(kekAlgorithm, ikm, info);
byte[] iv = new byte[AEADUtils.getIVLength(aeadAlgorithm)];
random.nextBytes(iv);
int tagLen = AEADUtils.getAuthTagLength(aeadAlgorithm);
byte[] eskAndTag = getEskAndTag(kekAlgorithm, aeadAlgorithm, sessionInfo, kek, iv, info);
byte[] esk = Arrays.copyOfRange(eskAndTag, 0, eskAndTag.length - tagLen);
byte[] tag = Arrays.copyOfRange(eskAndTag, esk.length, eskAndTag.length);
return SymmetricKeyEncSessionPacket.createV6Packet(kekAlgorithm, aeadAlgorithm, iv, s2k, esk, tag);
}
/**
* Generate a V4 SKESK packet.
*
* @param encAlgorithm the {@link SymmetricKeyAlgorithmTags encryption algorithm} being used
* @param sessionInfo session data generated by the encrypted data generator.
* @return v4 SKESK packet
* @throws PGPException
*/
public ContainedPacket generate(int encAlgorithm, byte[] sessionInfo)
throws PGPException
{
if (sessionInfo == null)
{
return SymmetricKeyEncSessionPacket.createV4Packet(encAlgorithm, s2k, null);
}
byte[] key = getKey(encAlgorithm);
//
// the passed in session info has the an RSA/ElGamal checksum added to it, for PBE this is not included.
//
byte[] nSessionInfo = new byte[sessionInfo.length - 2];
System.arraycopy(sessionInfo, 0, nSessionInfo, 0, nSessionInfo.length);
return SymmetricKeyEncSessionPacket.createV4Packet(encAlgorithm, s2k, encryptSessionInfo(encAlgorithm, key, nSessionInfo));
}
abstract protected byte[] encryptSessionInfo(int encAlgorithm, byte[] key, byte[] sessionInfo)
throws PGPException;
abstract protected byte[] getEskAndTag(int kekAlgorithm, int aeadAlgorithm, byte[] sessionInfo, byte[] key, byte[] iv, byte[] info)
throws PGPException;
abstract protected byte[] generateV6KEK(int kekAlgorithm, byte[] ikm, byte[] info)
throws PGPException;
}