/*
* Copyright 2010-2012 sshj contributors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package net.schmizz.sshj.transport.verification;
import net.schmizz.sshj.common.Base64;
import net.schmizz.sshj.common.Buffer;
import net.schmizz.sshj.common.IOUtils;
import net.schmizz.sshj.common.KeyType;
import net.schmizz.sshj.common.SSHException;
import net.schmizz.sshj.common.SecurityUtils;
import net.schmizz.sshj.transport.mac.HMACSHA1;
import net.schmizz.sshj.transport.mac.MAC;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.PublicKey;
import java.security.spec.RSAPublicKeySpec;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* A {@link HostKeyVerifier} implementation for a {@code known_hosts} file i.e. in the format used by OpenSSH.
*
* @see <a href="http://nms.lcs.mit.edu/projects/ssh/README.hashed-hosts">Hashed hostnames spec</a>
*/
public class OpenSSHKnownHosts
implements HostKeyVerifier {
private static final Logger LOG = LoggerFactory.getLogger(OpenSSHKnownHosts.class);
protected final Logger log = LoggerFactory.getLogger(getClass());
protected final File khFile;
protected final List<HostEntry> entries = new ArrayList<HostEntry>();
public OpenSSHKnownHosts(File khFile)
throws IOException {
this.khFile = khFile;
if (khFile.exists()) {
final BufferedReader br = new BufferedReader(new FileReader(khFile));
try {
// Read in the file, storing each line as an entry
String line;
while ((line = br.readLine()) != null)
try {
HostEntry entry = EntryFactory.parseEntry(line);
if (entry != null) {
entries.add(entry);
}
} catch (SSHException ignore) {
log.debug("Bad line ({}): {} ", ignore.toString(), line);
}
} finally {
IOUtils.closeQuietly(br);
}
}
}
public File getFile() {
return khFile;
}
@Override
public boolean verify(final String hostname, final int port, final PublicKey key) {
final KeyType type = KeyType.fromKey(key);
if (type == KeyType.UNKNOWN)
return false;
final String adjustedHostname = (port != 22) ? "[" + hostname + "]:" + port : hostname;
for (HostEntry e : entries) {
try {
if (e.appliesTo(type, adjustedHostname))
return e.verify(key) || hostKeyChangedAction(e, adjustedHostname, key);
} catch (IOException ioe) {
log.error("Error with {}: {}", e, ioe);
return false;
}
}
return hostKeyUnverifiableAction(adjustedHostname, key);
}
protected boolean hostKeyUnverifiableAction(String hostname, PublicKey key) {
return false;
}
protected boolean hostKeyChangedAction(HostEntry entry, String hostname, PublicKey key) {
log.warn("Host key for `{}` has changed!", hostname);
return false;
}
public List<HostEntry> entries() {
return entries;
}
private static final String LS = System.getProperty("line.separator");
public void write()
throws IOException {
final BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(khFile));
try {
for (HostEntry entry : entries)
bos.write((entry.getLine() + LS).getBytes(IOUtils.UTF8));
} finally {
bos.close();
}
}
public static File detectSSHDir() {
final File sshDir = new File(System.getProperty("user.home"), ".ssh");
return sshDir.exists() ? sshDir : null;
}
/**
* Each line in these files contains the following fields: markers
* (optional), hostnames, bits, exponent, modulus, comment. The fields are
* separated by spaces.
* <p/>
* The marker is optional, but if it is present then it must be one of
* ``@cert-authority'', to indicate that the line contains a certification
* authority (CA) key, or ``@revoked'', to indicate that the key contained
* on the line is revoked and must not ever be accepted. Only one marker
* should be used on a key line.
* <p/>
* Hostnames is a comma-separated list of patterns (`*' and `?' act as
* wildcards); each pattern in turn is matched against the canonical host
* name (when authenticating a client) or against the user-supplied name
* (when authenticating a server). A pattern may also be preceded by `!' to
* indicate negation: if the host name matches a negated pattern, it is not
* accepted (by that line) even if it matched another pattern on the line.
* A hostname or address may optionally be enclosed within `[' and `]'
* brackets then followed by `:' and a non-standard port number.
* <p/>
* Alternately, hostnames may be stored in a hashed form which hides host
* names and addresses should the file's contents be disclosed. Hashed
* hostnames start with a `|' character. Only one hashed hostname may
* appear on a single line and none of the above negation or wildcard
* operators may be applied.
* <p/>
* Bits, exponent, and modulus are taken directly from the RSA host key;
* they can be obtained, for example, from /etc/ssh/ssh_host_key.pub. The
* optional comment field continues to the end of the line, and is not used.
* <p/>
* Lines starting with `#' and empty lines are ignored as comments.
*/
public static class EntryFactory {
public static HostEntry parseEntry(String line)
throws IOException {
if (isComment(line)) {
return new CommentEntry(line);
}
final String[] split = line.split(" ");
int i = 0;
final Marker marker = Marker.fromString(split[i]);
if (marker != null) {
i++;
}
final String hostnames = split[i++];
final String sType = split[i++];
KeyType type = KeyType.fromString(sType);
PublicKey key;
if (type != KeyType.UNKNOWN) {
final String sKey = split[i++];
key = getKey(sKey);
} else if (isBits(sType)) {
type = KeyType.RSA;
// int bits = Integer.valueOf(sType);
final BigInteger e = new BigInteger(split[i++]);
final BigInteger n = new BigInteger(split[i++]);
try {
final KeyFactory keyFactory = SecurityUtils.getKeyFactory("RSA");
key = keyFactory.generatePublic(new RSAPublicKeySpec(n, e));
} catch (Exception ex) {
LOG.error("Error reading entry `{}`, could not create key", line, ex);
return null;
}
} else {
LOG.error("Error reading entry `{}`, could not determine type", line);
return null;
}
if (isHashed(hostnames)) {
return new HashedEntry(marker, hostnames, type, key);
} else {
return new SimpleEntry(marker, hostnames, type, key);
}
}
private static PublicKey getKey(String sKey)
throws IOException {
return new Buffer.PlainBuffer(Base64.decode(sKey)).readPublicKey();
}
private static boolean isBits(String type) {
try {
Integer.parseInt(type);
return true;
} catch (NumberFormatException e) {
return false;
}
}
private static boolean isComment(String line) {
return line.isEmpty() || line.startsWith("#");
}
public static boolean isHashed(String line) {
return line.startsWith("|1|");
}
}
public interface HostEntry {
boolean appliesTo(KeyType type, String host)
throws IOException;
boolean verify(PublicKey key)
throws IOException;
String getLine();
}
public static class CommentEntry
implements HostEntry {
private final String comment;
public CommentEntry(String comment) {
this.comment = comment;
}
@Override
public boolean appliesTo(KeyType type, String host) {
return false;
}
@Override
public boolean verify(PublicKey key) {
return false;
}
@Override
public String getLine() {
return comment;
}
}
public static abstract class AbstractEntry
implements HostEntry {
protected final OpenSSHKnownHosts.Marker marker;
protected final KeyType type;
protected final PublicKey key;
public AbstractEntry(Marker marker, KeyType type, PublicKey key) {
this.marker = marker;
this.type = type;
this.key = key;
}
@Override
public boolean verify(PublicKey key)
throws IOException {
return key.equals(this.key) && marker != Marker.REVOKED;
}
public String getLine() {
final StringBuilder line = new StringBuilder();
if (marker != null) line.append(marker.getMarkerString()).append(" ");
line.append(getHostPart());
line.append(" ").append(type.toString());
line.append(" ").append(getKeyString());
return line.toString();
}
private String getKeyString() {
final Buffer.PlainBuffer buf = new Buffer.PlainBuffer().putPublicKey(key);
return Base64.encodeBytes(buf.array(), buf.rpos(), buf.available());
}
protected abstract String getHostPart();
}
public static class SimpleEntry
extends AbstractEntry {
private final List<String> hosts;
private final String hostnames;
public SimpleEntry(Marker marker, String hostnames, KeyType type, PublicKey key) {
super(marker, type, key);
this.hostnames = hostnames;
hosts = Arrays.asList(hostnames.split(","));
}
@Override
protected String getHostPart() {
return hostnames;
}
@Override
public boolean appliesTo(KeyType type, String host)
throws IOException {
return type == this.type && hostnames.contains(host);
}
}
public static class HashedEntry
extends AbstractEntry {
private final MAC sha1 = new HMACSHA1();
private final String hashedHost;
private final String salt;
private byte[] saltyBytes;
public HashedEntry(Marker marker, String hash, KeyType type, PublicKey key)
throws SSHException {
super(marker, type, key);
this.hashedHost = hash;
{
final String[] hostParts = hashedHost.split("\\|");
if (hostParts.length != 4)
throw new SSHException("Unrecognized format for hashed hostname");
salt = hostParts[2];
}
}
@Override
public boolean appliesTo(KeyType type, String host)
throws IOException {
return this.type == type && hashedHost.equals(hashHost(host));
}
private String hashHost(String host)
throws IOException {
sha1.init(getSaltyBytes());
return "|1|" + salt + "|" + Base64.encodeBytes(sha1.doFinal(host.getBytes(IOUtils.UTF8)));
}
private byte[] getSaltyBytes()
throws IOException {
if (saltyBytes == null) {
saltyBytes = Base64.decode(salt);
}
return saltyBytes;
}
@Override
public String getLine() {
return null;
}
@Override
protected String getHostPart() {
return hashedHost;
}
}
public enum Marker {
CA_CERT("@cert-authority"),
REVOKED("@revoked");
private final String sMarker;
Marker(String sMarker) {
this.sMarker = sMarker;
}
public String getMarkerString() {
return sMarker;
}
public static Marker fromString(String str) {
for (Marker m: values())
if (m.sMarker.equals(str))
return m;
return null;
}
}
}