GpgSigner.java

/*
 * Copyright (C) 2018, 2022 Salesforce and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */
package org.eclipse.jgit.lib;

import java.util.Iterator;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;

import org.eclipse.jgit.annotations.NonNull;
import org.eclipse.jgit.annotations.Nullable;
import org.eclipse.jgit.api.errors.CanceledException;
import org.eclipse.jgit.transport.CredentialsProvider;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Creates GPG signatures for Git objects.
 *
 * @since 5.3
 */
public abstract class GpgSigner {

    private static final Logger LOG = LoggerFactory.getLogger(GpgSigner.class);

    private static class DefaultSigner {

        private static volatile GpgSigner defaultSigner = loadGpgSigner();

        private static GpgSigner loadGpgSigner() {
            try {
                ServiceLoader<GpgSigner> loader = ServiceLoader
                        .load(GpgSigner.class);
                Iterator<GpgSigner> iter = loader.iterator();
                if (iter.hasNext()) {
                    return iter.next();
                }
            } catch (ServiceConfigurationError e) {
                LOG.error(e.getMessage(), e);
            }
            return null;
        }

        private DefaultSigner() {
            // No instantiation
        }

        public static GpgSigner getDefault() {
            return defaultSigner;
        }

        public static void setDefault(GpgSigner signer) {
            defaultSigner = signer;
        }
    }

    /**
     * Get the default signer, or <code>null</code>.
     *
     * @return the default signer, or <code>null</code>.
     */
    public static GpgSigner getDefault() {
        return DefaultSigner.getDefault();
    }

    /**
     * Set the default signer.
     *
     * @param signer
     *            the new default signer, may be <code>null</code> to select no
     *            default.
     */
    public static void setDefault(GpgSigner signer) {
        DefaultSigner.setDefault(signer);
    }

    /**
     * Signs the specified commit.
     *
     * <p>
     * Implementors should obtain the payload for signing from the specified
     * commit via {@link CommitBuilder#build()} and create a proper
     * {@link GpgSignature}. The generated signature must be set on the
     * specified {@code commit} (see
     * {@link CommitBuilder#setGpgSignature(GpgSignature)}).
     * </p>
     * <p>
     * Any existing signature on the commit must be discarded prior obtaining
     * the payload via {@link CommitBuilder#build()}.
     * </p>
     *
     * @param commit
     *            the commit to sign (must not be <code>null</code> and must be
     *            complete to allow proper calculation of payload)
     * @param gpgSigningKey
     *            the signing key to locate (passed as is to the GPG signing
     *            tool as is; eg., value of <code>user.signingkey</code>)
     * @param committer
     *            the signing identity (to help with key lookup in case signing
     *            key is not specified)
     * @param credentialsProvider
     *            provider to use when querying for signing key credentials (eg.
     *            passphrase)
     * @throws CanceledException
     *             when signing was canceled (eg., user aborted when entering
     *             passphrase)
     */
    public abstract void sign(@NonNull CommitBuilder commit,
            @Nullable String gpgSigningKey, @NonNull PersonIdent committer,
            CredentialsProvider credentialsProvider) throws CanceledException;

    /**
     * Indicates if a signing key is available for the specified committer
     * and/or signing key.
     *
     * @param gpgSigningKey
     *            the signing key to locate (passed as is to the GPG signing
     *            tool as is; eg., value of <code>user.signingkey</code>)
     * @param committer
     *            the signing identity (to help with key lookup in case signing
     *            key is not specified)
     * @param credentialsProvider
     *            provider to use when querying for signing key credentials (eg.
     *            passphrase)
     * @return <code>true</code> if a signing key is available,
     *         <code>false</code> otherwise
     * @throws CanceledException
     *             when signing was canceled (eg., user aborted when entering
     *             passphrase)
     */
    public abstract boolean canLocateSigningKey(@Nullable String gpgSigningKey,
            @NonNull PersonIdent committer,
            CredentialsProvider credentialsProvider) throws CanceledException;

}