PasswordProviderWrapper.java

/*
 * Copyright (C) 2018, 2020 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 org.apache.sshd.core.CoreModuleProperties.PASSWORD_PROMPTS;

import java.io.IOException;
import java.net.URISyntaxException;
import java.security.GeneralSecurityException;
import java.util.Arrays;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Supplier;

import org.apache.sshd.common.AttributeRepository.AttributeKey;
import org.apache.sshd.common.NamedResource;
import org.apache.sshd.common.config.keys.FilePasswordProvider;
import org.apache.sshd.common.session.SessionContext;
import org.eclipse.jgit.annotations.NonNull;
import org.eclipse.jgit.transport.CredentialsProvider;
import org.eclipse.jgit.transport.URIish;
import org.eclipse.jgit.transport.sshd.KeyPasswordProvider;

/**
 * A bridge from sshd's {@link FilePasswordProvider} to our per-session
 * {@link KeyPasswordProvider} API.
 */
public class PasswordProviderWrapper implements FilePasswordProvider {

    private static final AttributeKey<PerSessionState> STATE = new AttributeKey<>();

    private static class PerSessionState {

        Map<String, AtomicInteger> counts = new ConcurrentHashMap<>();

        KeyPasswordProvider delegate;

    }

    private final Supplier<KeyPasswordProvider> factory;

    /**
     * Creates a new {@link PasswordProviderWrapper}.
     *
     * @param factory
     *            to use to create per-session {@link KeyPasswordProvider}s
     */
    public PasswordProviderWrapper(
            @NonNull Supplier<KeyPasswordProvider> factory) {
        this.factory = factory;
    }

    private PerSessionState getState(SessionContext context) {
        PerSessionState state = context.getAttribute(STATE);
        if (state == null) {
            state = new PerSessionState();
            state.delegate = factory.get();
            state.delegate.setAttempts(
                    PASSWORD_PROMPTS.getRequiredDefault().intValue());
            context.setAttribute(STATE, state);
        }
        return state;
    }

    @Override
    public String getPassword(SessionContext session, NamedResource resource,
            int attemptIndex) throws IOException {
        String key = resource.getName();
        PerSessionState state = getState(session);
        int attempt = state.counts
                .computeIfAbsent(key, k -> new AtomicInteger()).get();
        char[] passphrase = state.delegate.getPassphrase(toUri(key), attempt);
        if (passphrase == null) {
            return null;
        }
        try {
            return new String(passphrase);
        } finally {
            Arrays.fill(passphrase, '\000');
        }
    }

    @Override
    public ResourceDecodeResult handleDecodeAttemptResult(
            SessionContext session, NamedResource resource, int retryIndex,
            String password, Exception err)
            throws IOException, GeneralSecurityException {
        String key = resource.getName();
        PerSessionState state = getState(session);
        AtomicInteger count = state.counts.get(key);
        int numberOfAttempts = count == null ? 0 : count.incrementAndGet();
        ResourceDecodeResult result = null;
        try {
            if (state.delegate.keyLoaded(toUri(key), numberOfAttempts, err)) {
                result = ResourceDecodeResult.RETRY;
            } else {
                result = ResourceDecodeResult.TERMINATE;
            }
        } finally {
            if (result != ResourceDecodeResult.RETRY) {
                state.counts.remove(key);
            }
        }
        return result;
    }

    /**
     * Creates a {@link URIish} from a given string. The
     * {@link CredentialsProvider} uses uris as resource identifications.
     *
     * @param resourceKey
     *            to convert
     * @return the uri
     */
    private URIish toUri(String resourceKey) {
        try {
            return new URIish(resourceKey);
        } catch (URISyntaxException e) {
            return new URIish().setPath(resourceKey); // Doesn't check!!
        }
    }

}