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The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.5 to JDK 1.8. The APIs can be used in conjunction with a JCE/JCA provider such as the one provided with the Bouncy Castle Cryptography APIs.

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package org.bouncycastle.cms;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import org.bouncycastle.asn1.ASN1Encodable;
import org.bouncycastle.asn1.cms.PasswordRecipientInfo;
import org.bouncycastle.asn1.pkcs.PBKDF2Params;
import org.bouncycastle.asn1.x509.AlgorithmIdentifier;
import org.bouncycastle.crypto.PBEParametersGenerator;
import org.bouncycastle.crypto.generators.PKCS5S2ParametersGenerator;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.util.Integers;

/**
 * the RecipientInfo class for a recipient who has been sent a message
 * encrypted using a password.
 */
public class PasswordRecipientInformation
    extends RecipientInformation
{
    static Map KEYSIZES = new HashMap();
    static Map BLOCKSIZES = new HashMap();

    static
    {
        BLOCKSIZES.put(CMSAlgorithm.DES_EDE3_CBC, Integers.valueOf(8));
        BLOCKSIZES.put(CMSAlgorithm.AES128_CBC, Integers.valueOf(16));
        BLOCKSIZES.put(CMSAlgorithm.AES192_CBC, Integers.valueOf(16));
        BLOCKSIZES.put(CMSAlgorithm.AES256_CBC, Integers.valueOf(16));

        KEYSIZES.put(CMSAlgorithm.DES_EDE3_CBC, Integers.valueOf(192));
        KEYSIZES.put(CMSAlgorithm.AES128_CBC, Integers.valueOf(128));
        KEYSIZES.put(CMSAlgorithm.AES192_CBC, Integers.valueOf(192));
        KEYSIZES.put(CMSAlgorithm.AES256_CBC, Integers.valueOf(256));
    }

    private PasswordRecipientInfo info;

    PasswordRecipientInformation(
        PasswordRecipientInfo   info,
        AlgorithmIdentifier     messageAlgorithm,
        CMSSecureReadable       secureReadable,
        AuthAttributesProvider  additionalData)
    {
        super(info.getKeyEncryptionAlgorithm(), messageAlgorithm, secureReadable, additionalData);

        this.info = info;
        this.rid = new PasswordRecipientId();
    }

    /**
     * return the object identifier for the key derivation algorithm, or null
     * if there is none present.
     *
     * @return OID for key derivation algorithm, if present.
     */
    public String getKeyDerivationAlgOID()
    {
        if (info.getKeyDerivationAlgorithm() != null)
        {
            return info.getKeyDerivationAlgorithm().getAlgorithm().getId();
        }

        return null;
    }

    /**
     * return the ASN.1 encoded key derivation algorithm parameters, or null if
     * there aren't any.
     * @return ASN.1 encoding of key derivation algorithm parameters.
     */
    public byte[] getKeyDerivationAlgParams()
    {
        try
        {
            if (info.getKeyDerivationAlgorithm() != null)
            {
                ASN1Encodable params = info.getKeyDerivationAlgorithm().getParameters();
                if (params != null)
                {
                    return params.toASN1Primitive().getEncoded();
                }
            }

            return null;
        }
        catch (Exception e)
        {
            throw new RuntimeException("exception getting encryption parameters " + e);
        }
    }

    /**
     * Return the key derivation algorithm details for the key in this recipient.
     *
     * @return AlgorithmIdentifier representing the key derivation algorithm.
     */
    public AlgorithmIdentifier getKeyDerivationAlgorithm()
    {
        return info.getKeyDerivationAlgorithm();
    }

    protected RecipientOperator getRecipientOperator(Recipient recipient)
        throws CMSException, IOException
    {
        PasswordRecipient pbeRecipient = (PasswordRecipient)recipient;
        AlgorithmIdentifier kekAlg = AlgorithmIdentifier.getInstance(info.getKeyEncryptionAlgorithm());
        AlgorithmIdentifier kekAlgParams = AlgorithmIdentifier.getInstance(kekAlg.getParameters());

        byte[] passwordBytes = getPasswordBytes(pbeRecipient.getPasswordConversionScheme(),
            pbeRecipient.getPassword());
        PBKDF2Params params = PBKDF2Params.getInstance(info.getKeyDerivationAlgorithm().getParameters());

        PKCS5S2ParametersGenerator gen = new PKCS5S2ParametersGenerator();
        gen.init(passwordBytes, params.getSalt(), params.getIterationCount().intValue());

        int keySize = ((Integer)KEYSIZES.get(kekAlgParams.getAlgorithm())).intValue();

        byte[] derivedKey = ((KeyParameter)gen.generateDerivedParameters(keySize)).getKey();

        return pbeRecipient.getRecipientOperator(kekAlgParams, messageAlgorithm, derivedKey, info.getEncryptedKey().getOctets());
    }
    
    protected byte[] getPasswordBytes(int scheme, char[] password)
    {
        if (scheme == PasswordRecipient.PKCS5_SCHEME2)
        {
            return PBEParametersGenerator.PKCS5PasswordToBytes(password);
        }

        return PBEParametersGenerator.PKCS5PasswordToUTF8Bytes(password);
    }
}