CachingKeyPairProvider.java

/*
 * Copyright (C) 2018, Thomas Wolf <thomas.wolf@paranor.ch> 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.internal.transport.sshd;

import static java.text.MessageFormat.format;

import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.security.GeneralSecurityException;
import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.PrivateKey;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.concurrent.CancellationException;

import javax.security.auth.DestroyFailedException;

import org.apache.sshd.common.NamedResource;
import org.apache.sshd.common.config.keys.FilePasswordProvider;
import org.apache.sshd.common.keyprovider.FileKeyPairProvider;
import org.apache.sshd.common.session.SessionContext;
import org.apache.sshd.common.util.io.resource.IoResource;
import org.apache.sshd.common.util.security.SecurityUtils;
import org.eclipse.jgit.transport.sshd.KeyCache;

/**
 * A {@link FileKeyPairProvider} that uses an external {@link KeyCache}.
 */
public class CachingKeyPairProvider extends FileKeyPairProvider
        implements Iterable<KeyPair> {

    private final KeyCache cache;

    /**
     * Creates a new {@link CachingKeyPairProvider} using the given
     * {@link KeyCache}. If the cache is {@code null}, this is a simple
     * {@link FileKeyPairProvider}.
     *
     * @param paths
     *            to load keys from
     * @param cache
     *            to use, may be {@code null} if no external caching is desired
     */
    public CachingKeyPairProvider(List<Path> paths, KeyCache cache) {
        super(paths);
        this.cache = cache;
    }

    @Override
    public Iterator<KeyPair> iterator() {
        return iterator(null);
    }

    private Iterator<KeyPair> iterator(SessionContext session) {
        Collection<? extends Path> resources = getPaths();
        if (resources.isEmpty()) {
            return Collections.emptyListIterator();
        }
        return new CancellingKeyPairIterator(session, resources);
    }

    @Override
    public Iterable<KeyPair> loadKeys(SessionContext session) {
        return () -> iterator(session);
    }

    private KeyPair loadKey(SessionContext session, Path path)
            throws IOException, GeneralSecurityException {
        if (!Files.exists(path)) {
            log.warn(format(SshdText.get().identityFileNotFound, path));
            return null;
        }
        IoResource<Path> resource = getIoResource(session, path);
        if (cache == null) {
            return loadKey(session, resource, path, getPasswordFinder());
        }
        Throwable[] t = { null };
        KeyPair key = cache.get(path, p -> {
            try {
                return loadKey(session, resource, p, getPasswordFinder());
            } catch (IOException | GeneralSecurityException e) {
                t[0] = e;
                return null;
            }
        });
        if (t[0] != null) {
            if (t[0] instanceof CancellationException) {
                throw (CancellationException) t[0];
            }
            throw new IOException(
                    format(SshdText.get().keyLoadFailed, resource), t[0]);
        }
        return key;
    }

    private KeyPair loadKey(SessionContext session, NamedResource resource,
            Path path, FilePasswordProvider passwordProvider)
            throws IOException, GeneralSecurityException {
        try (InputStream stream = Files.newInputStream(path)) {
            Iterable<KeyPair> ids = SecurityUtils.loadKeyPairIdentities(session,
                    resource, stream, passwordProvider);
            if (ids == null) {
                throw new InvalidKeyException(
                        format(SshdText.get().identityFileNoKey, path));
            }
            Iterator<KeyPair> keys = ids.iterator();
            if (!keys.hasNext()) {
                throw new InvalidKeyException(format(
                        SshdText.get().identityFileUnsupportedFormat, path));
            }
            KeyPair result = keys.next();
            if (keys.hasNext()) {
                log.warn(format(SshdText.get().identityFileMultipleKeys, path));
                keys.forEachRemaining(k -> {
                    PrivateKey pk = k.getPrivate();
                    if (pk != null) {
                        try {
                            pk.destroy();
                        } catch (DestroyFailedException e) {
                            // Ignore
                        }
                    }
                });
            }
            return result;
        }
    }

    private class CancellingKeyPairIterator implements Iterator<KeyPair> {

        private final SessionContext context;

        private final Iterator<Path> paths;

        private KeyPair nextItem;

        private boolean nextSet;

        public CancellingKeyPairIterator(SessionContext session,
                Collection<? extends Path> resources) {
            List<Path> copy = new ArrayList<>(resources.size());
            copy.addAll(resources);
            paths = copy.iterator();
            context = session;
        }

        @Override
        public boolean hasNext() {
            if (nextSet) {
                return nextItem != null;
            }
            nextSet = true;
            while (nextItem == null && paths.hasNext()) {
                try {
                    nextItem = loadKey(context, paths.next());
                } catch (CancellationException cancelled) {
                    throw cancelled;
                } catch (Exception other) {
                    log.warn(other.getMessage(), other);
                }
            }
            return nextItem != null;
        }

        @Override
        public KeyPair next() {
            if (!nextSet && !hasNext()) {
                throw new NoSuchElementException();
            }
            KeyPair result = nextItem;
            nextItem = null;
            nextSet = false;
            if (result == null) {
                throw new NoSuchElementException();
            }
            return result;
        }

    }
}