org.bouncycastle.cert.dane.DANEEntrySelectorFactory Maven / Gradle / Ivy

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The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. 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.

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package org.bouncycastle.cert.dane;

import java.io.IOException;
import java.io.OutputStream;

import org.bouncycastle.operator.DigestCalculator;
import org.bouncycastle.util.Strings;
import org.bouncycastle.util.encoders.Hex;

/**
 * Factory for creating selector objects to use with the DANECertificateStore.
 */
public class DANEEntrySelectorFactory
{
    private final DigestCalculator digestCalculator;

    /**
     * Base constructor.
     * 
     * At the moment you would call this as:
     * 
     *     new DANEEntrySelectorFactory(new TruncatingDigestCalculator(new SHA256DigestCalculator()));
     * 
     * or some equivalent.
     *
     * @param digestCalculator a calculator for the message digest to filter email addresses currently truncated SHA-256 (originally SHA-224).
     */
    public DANEEntrySelectorFactory(DigestCalculator digestCalculator)
    {
        this.digestCalculator = digestCalculator;
    }

    /**
     * Create a selector for the passed in email address.
     * @param emailAddress the emails address of interest.
     * @throws DANEException in case of issue generating a matching name.
     */
    public DANEEntrySelector createSelector(String emailAddress)
        throws DANEException
    {
        final byte[] enc = Strings.toUTF8ByteArray(emailAddress.substring(0, emailAddress.indexOf('@')));

        try
        {
            OutputStream cOut = digestCalculator.getOutputStream();

            cOut.write(enc);

            cOut.close();
        }
        catch (IOException e)
        {
            throw new DANEException("Unable to calculate digest string: " + e.getMessage(), e);
        }

        byte[] hash = digestCalculator.getDigest();

        final String domainName = Strings.fromByteArray(Hex.encode(hash)) + "._smimecert." + emailAddress.substring(emailAddress.indexOf('@') + 1);

        return new DANEEntrySelector(domainName);
    }
}