KnownHostEntryReader.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.nio.charset.StandardCharsets.UTF_8;
import static java.text.MessageFormat.format;
import static org.apache.sshd.client.config.hosts.HostPatternsHolder.NON_STANDARD_PORT_PATTERN_ENCLOSURE_END_DELIM;
import static org.apache.sshd.client.config.hosts.HostPatternsHolder.NON_STANDARD_PORT_PATTERN_ENCLOSURE_START_DELIM;

import java.io.BufferedReader;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Arrays;
import java.util.Collection;
import java.util.LinkedList;
import java.util.List;
import java.util.stream.Collectors;

import org.apache.sshd.client.config.hosts.HostPatternValue;
import org.apache.sshd.client.config.hosts.HostPatternsHolder;
import org.apache.sshd.client.config.hosts.KnownHostEntry;
import org.apache.sshd.client.config.hosts.KnownHostHashValue;
import org.apache.sshd.common.config.keys.AuthorizedKeyEntry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Apache MINA sshd 2.0.0 KnownHostEntry cannot read a host entry line like
 * "host:port ssh-rsa <key>"; it complains about an illegal character in the
 * host name (correct would be "[host]:port"). The default known_hosts reader
 * also aborts reading on the first error.
 * <p>
 * This reader is a bit more robust and tries to handle this case if there is
 * only one colon (otherwise it might be an IPv6 address (without port)), and it
 * skips and logs invalid entries, but still returns all other valid entries
 * from the file.
 * </p>
 */
public class KnownHostEntryReader {

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

    private KnownHostEntryReader() {
        // No instantiation
    }

    /**
     * Reads a known_hosts file and returns all valid entries. Invalid entries
     * are skipped (and a message is logged).
     *
     * @param path
     *            of the file to read
     * @return a {@link List} of all valid entries read from the file
     * @throws IOException
     *             if the file cannot be read.
     */
    public static List<KnownHostEntry> readFromFile(Path path)
            throws IOException {
        List<KnownHostEntry> result = new LinkedList<>();
        try (BufferedReader r = Files.newBufferedReader(path, UTF_8)) {
            r.lines().forEachOrdered(l -> {
                if (l == null) {
                    return;
                }
                String line = clean(l);
                if (line.isEmpty()) {
                    return;
                }
                try {
                    KnownHostEntry entry = parseHostEntry(line);
                    if (entry != null) {
                        result.add(entry);
                    } else {
                        LOG.warn(format(SshdText.get().knownHostsInvalidLine,
                                path, line));
                    }
                } catch (RuntimeException e) {
                    LOG.warn(format(SshdText.get().knownHostsInvalidLine, path,
                            line), e);
                }
            });
        }
        return result;
    }

    private static String clean(String line) {
        int i = line.indexOf('#');
        return i < 0 ? line.trim() : line.substring(0, i).trim();
    }

    private static KnownHostEntry parseHostEntry(String line) {
        KnownHostEntry entry = new KnownHostEntry();
        entry.setConfigLine(line);
        String tmp = line;
        int i = 0;
        if (tmp.charAt(0) == KnownHostEntry.MARKER_INDICATOR) {
            // A marker
            i = tmp.indexOf(' ', 1);
            if (i < 0) {
                return null;
            }
            entry.setMarker(tmp.substring(1, i));
            tmp = tmp.substring(i + 1).trim();
        }
        i = tmp.indexOf(' ');
        if (i < 0) {
            return null;
        }
        // Hash, or host patterns
        if (tmp.charAt(0) == KnownHostHashValue.HASHED_HOST_DELIMITER) {
            // Hashed host entry
            KnownHostHashValue hash = KnownHostHashValue
                    .parse(tmp.substring(0, i));
            if (hash == null) {
                return null;
            }
            entry.setHashedEntry(hash);
            entry.setPatterns(null);
        } else {
            Collection<HostPatternValue> patterns = parsePatterns(
                    tmp.substring(0, i));
            if (patterns == null || patterns.isEmpty()) {
                return null;
            }
            entry.setHashedEntry(null);
            entry.setPatterns(patterns);
        }
        tmp = tmp.substring(i + 1).trim();
        AuthorizedKeyEntry key = AuthorizedKeyEntry
                .parseAuthorizedKeyEntry(tmp);
        if (key == null) {
            return null;
        }
        entry.setKeyEntry(key);
        return entry;
    }

    private static Collection<HostPatternValue> parsePatterns(String text) {
        if (text.isEmpty()) {
            return null;
        }
        List<String> items = Arrays.stream(text.split(",")) //$NON-NLS-1$
                .filter(item -> item != null && !item.isEmpty()).map(item -> {
                    if (NON_STANDARD_PORT_PATTERN_ENCLOSURE_START_DELIM == item
                            .charAt(0)) {
                        return item;
                    }
                    int firstColon = item.indexOf(':');
                    if (firstColon < 0) {
                        return item;
                    }
                    int secondColon = item.indexOf(':', firstColon + 1);
                    if (secondColon > 0) {
                        // Assume an IPv6 address (without port).
                        return item;
                    }
                    // We have "host:port", should be "[host]:port"
                    return NON_STANDARD_PORT_PATTERN_ENCLOSURE_START_DELIM
                            + item.substring(0, firstColon)
                            + NON_STANDARD_PORT_PATTERN_ENCLOSURE_END_DELIM
                            + item.substring(firstColon);
                }).collect(Collectors.toList());
        return items.isEmpty() ? null : HostPatternsHolder.parsePatterns(items);
    }
}