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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.sshd.server.keyprovider;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.LinkOption;
import java.nio.file.OpenOption;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.nio.file.attribute.AclEntry;
import java.nio.file.attribute.AclEntryPermission;
import java.nio.file.attribute.AclEntryType;
import java.nio.file.attribute.AclFileAttributeView;
import java.nio.file.attribute.UserPrincipal;
import java.security.GeneralSecurityException;
import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PublicKey;
import java.security.spec.AlgorithmParameterSpec;
import java.util.ArrayList;
import java.util.Collections;
import java.util.EnumSet;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicReference;
import org.apache.sshd.common.AlgorithmNameProvider;
import org.apache.sshd.common.NamedResource;
import org.apache.sshd.common.cipher.ECCurves;
import org.apache.sshd.common.config.keys.BuiltinIdentities;
import org.apache.sshd.common.config.keys.KeyUtils;
import org.apache.sshd.common.keyprovider.AbstractKeyPairProvider;
import org.apache.sshd.common.keyprovider.KeySizeIndicator;
import org.apache.sshd.common.session.SessionContext;
import org.apache.sshd.common.util.GenericUtils;
import org.apache.sshd.common.util.OsUtils;
import org.apache.sshd.common.util.io.IoUtils;
import org.apache.sshd.common.util.io.resource.PathResource;
import org.apache.sshd.common.util.security.SecurityUtils;
/**
* Holds a single {@link KeyPair} which is generated the 1st time {@link #loadKeys(SessionContext)} is called. If
* there is a file backing it up and the file exists, the key is loaded from it. Otherwise a new key pair is generated
* and saved (provided a path is configured and {@link #isOverwriteAllowed()}
*
* @author Apache MINA SSHD Project
*/
public abstract class AbstractGeneratorHostKeyProvider
extends AbstractKeyPairProvider
implements AlgorithmNameProvider, KeySizeIndicator {
public static final String DEFAULT_ALGORITHM = KeyUtils.EC_ALGORITHM;
public static final boolean DEFAULT_ALLOWED_TO_OVERWRITE = true;
private final AtomicReference> keyPairHolder = new AtomicReference<>();
private Path path;
private String algorithm = DEFAULT_ALGORITHM;
private int keySize;
private AlgorithmParameterSpec keySpec;
private boolean overwriteAllowed = DEFAULT_ALLOWED_TO_OVERWRITE;
private boolean enforceFilePermissions = true;
protected AbstractGeneratorHostKeyProvider() {
super();
}
public Path getPath() {
return path;
}
public void setPath(Path path) {
this.path = (path == null) ? null : path.toAbsolutePath();
}
@Override
public String getAlgorithm() {
return algorithm;
}
public void setAlgorithm(String algorithm) {
this.algorithm = algorithm;
}
@Override
public int getKeySize() {
return keySize;
}
public void setKeySize(int keySize) {
this.keySize = keySize;
}
public AlgorithmParameterSpec getKeySpec() {
return keySpec;
}
public void setKeySpec(AlgorithmParameterSpec keySpec) {
this.keySpec = keySpec;
}
public boolean isOverwriteAllowed() {
return overwriteAllowed;
}
public void setOverwriteAllowed(boolean overwriteAllowed) {
this.overwriteAllowed = overwriteAllowed;
}
public boolean hasStrictFilePermissions() {
return enforceFilePermissions;
}
/**
* Sets whether this {@link AbstractGeneratorHostKeyProvider} shall enforce that a newly created host key file has
* file access permissions that allow only the owner to access it. By default {@code true}.
*
* @param strict whether to restrict file permissions to owner-only access
*/
public void setStrictFilePermissions(boolean strict) {
this.enforceFilePermissions = strict;
}
public void clearLoadedKeys() {
Iterable ids;
synchronized (keyPairHolder) {
ids = keyPairHolder.getAndSet(null);
}
if ((ids != null) && log.isDebugEnabled()) {
log.debug("clearLoadedKeys({}) removed keys", getPath());
}
}
@Override
public synchronized List loadKeys(SessionContext session) {
Path keyPath = getPath();
Iterable ids;
synchronized (keyPairHolder) {
ids = keyPairHolder.get();
if (ids == null) {
try {
ids = resolveKeyPairs(session, keyPath);
if (ids != null) {
keyPairHolder.set(ids);
}
} catch (Exception t) {
warn("loadKeys({}) Failed ({}) to resolve: {}",
keyPath, t.getClass().getSimpleName(), t.getMessage(), t);
}
}
}
List pairs = Collections.emptyList();
if (ids instanceof List) {
pairs = (List) ids;
} else if (ids != null) {
pairs = new ArrayList<>();
for (KeyPair kp : ids) {
if (kp == null) {
continue;
}
pairs.add(kp);
}
}
return pairs;
}
protected Iterable resolveKeyPairs(SessionContext session, Path keyPath)
throws IOException, GeneralSecurityException {
String alg = getAlgorithm();
if (keyPath != null) {
try {
Iterable ids = loadFromFile(session, alg, keyPath);
KeyPair kp = GenericUtils.head(ids);
if (kp != null) {
return ids;
}
} catch (Exception e) {
warn("resolveKeyPair({}) Failed ({}) to load: {}",
keyPath, e.getClass().getSimpleName(), e.getMessage(), e);
}
}
// either no file specified or no key in file
KeyPair kp = null;
try {
kp = generateKeyPair(alg);
if (kp == null) {
return null;
}
if (log.isDebugEnabled()) {
PublicKey key = kp.getPublic();
log.debug("resolveKeyPair({}) generated {} key={}-{}",
keyPath, alg, KeyUtils.getKeyType(key), KeyUtils.getFingerPrint(key));
}
} catch (Exception e) {
warn("resolveKeyPair({})[{}] Failed ({}) to generate {} key-pair: {}",
keyPath, alg, e.getClass().getSimpleName(), alg, e.getMessage(), e);
return null;
}
if (keyPath != null) {
try {
writeKeyPair(kp, keyPath);
} catch (Exception e) {
warn("resolveKeyPair({})[{}] Failed ({}) to write {} key: {}",
alg, keyPath, e.getClass().getSimpleName(), alg, e.getMessage(), e);
}
}
return Collections.singletonList(kp);
}
protected Iterable loadFromFile(SessionContext session, String alg, Path keyPath)
throws IOException, GeneralSecurityException {
LinkOption[] options = IoUtils.getLinkOptions(true);
if ((!Files.exists(keyPath, options)) || (!Files.isRegularFile(keyPath, options))) {
return null;
}
Iterable ids = readKeyPairs(session, keyPath, IoUtils.EMPTY_OPEN_OPTIONS);
KeyPair kp = GenericUtils.head(ids);
if (kp == null) {
return null;
}
// Assume all keys are of same type
PublicKey key = kp.getPublic();
String keyAlgorithm = key.getAlgorithm();
if (BuiltinIdentities.Constants.ECDSA.equalsIgnoreCase(keyAlgorithm)) {
keyAlgorithm = KeyUtils.EC_ALGORITHM;
} else if (BuiltinIdentities.Constants.ED25519.equalsIgnoreCase(keyAlgorithm)) {
keyAlgorithm = SecurityUtils.EDDSA;
}
if (Objects.equals(alg, keyAlgorithm)) {
if (log.isDebugEnabled()) {
log.debug("resolveKeyPair({}) loaded key={}-{}",
keyPath, KeyUtils.getKeyType(key), KeyUtils.getFingerPrint(key));
}
return ids;
}
// Not same algorithm - start again
if (log.isDebugEnabled()) {
log.debug("resolveKeyPair({}) mismatched loaded key algorithm: expected={}, loaded={}",
keyPath, alg, keyAlgorithm);
}
Files.deleteIfExists(keyPath);
return null;
}
protected Iterable readKeyPairs(SessionContext session, Path keyPath, OpenOption... options)
throws IOException, GeneralSecurityException {
PathResource location = new PathResource(keyPath, options);
try (InputStream inputStream = location.openInputStream()) {
return doReadKeyPairs(session, location, inputStream);
}
}
protected Iterable doReadKeyPairs(SessionContext session, NamedResource resourceKey, InputStream inputStream)
throws IOException, GeneralSecurityException {
return SecurityUtils.loadKeyPairIdentities(session, resourceKey, inputStream, null);
}
protected void writeKeyPair(KeyPair kp, Path keyPath)
throws IOException, GeneralSecurityException {
Objects.requireNonNull(kp, "No host key");
if (!Files.exists(keyPath) || isOverwriteAllowed()) {
// Create an empty file or truncate an existing file
Files.newOutputStream(keyPath).close();
if (enforceFilePermissions) {
setFilePermissions(keyPath);
}
try (OutputStream os = Files.newOutputStream(keyPath, StandardOpenOption.WRITE,
StandardOpenOption.TRUNCATE_EXISTING)) {
doWriteKeyPair(new PathResource(keyPath), kp, os);
} catch (Exception e) {
error("writeKeyPair({}) failed ({}) to write {} host key : {}",
keyPath, e.getClass().getSimpleName(),
KeyUtils.getKeyType(kp), e.getMessage(), e);
}
} else {
log.warn("Overwriting host key ({}) is disabled: using throwaway {} key: {}",
keyPath, KeyUtils.getKeyType(kp), KeyUtils.getFingerPrint(kp.getPublic()));
}
}
/**
* Restricts the file permissions such that only the owner can access the file.
*
* @param path {@link Path} of a newly created (empty) host key file
* @throws IOException on errors
*/
protected void setFilePermissions(Path path) throws IOException {
Throwable t = null;
if (OsUtils.isWin32()) {
AclFileAttributeView view = Files.getFileAttributeView(path, AclFileAttributeView.class);
UserPrincipal owner = Files.getOwner(path);
if (view != null && owner != null) {
try {
// Remove all access rights from non-owners.
List restricted = new ArrayList<>();
for (AclEntry acl : view.getAcl()) {
if (owner.equals(acl.principal())) {
// We explicitly give the owner full access permissions below.
continue;
}
if (!AclEntryType.ALLOW.equals(acl.type())) {
// DENY, AUDIT, and ALARM: keep them. The owner has successfully created the (empty) file,
// so any existing DENY entries are assumed not to have any influence on reading from or
// writing to this file by the owner.
restricted.add(acl);
}
}
// Give the owner full permissions to work with this file.
restricted.add(AclEntry.newBuilder()
.setType(AclEntryType.ALLOW)
.setPrincipal(owner)
.setPermissions(EnumSet.allOf(AclEntryPermission.class))
.build());
view.setAcl(restricted);
return;
} catch (IOException | SecurityException e) {
t = e;
}
}
} else {
File file = path.toFile();
if (!file.setExecutable(false)) {
log.debug("Host key file {}: cannot set non-executable", path);
}
boolean success = file.setWritable(false, false) && file.setWritable(true, true);
success = file.setReadable(false, false) && file.setReadable(true, true) && success;
if (success) {
return;
}
}
log.warn("Host key file {}: cannot set file permissions correctly (readable and writeable only by owner)", path, t);
}
protected abstract void doWriteKeyPair(
NamedResource resourceKey, KeyPair kp, OutputStream outputStream)
throws IOException, GeneralSecurityException;
protected KeyPair generateKeyPair(String algorithm) throws GeneralSecurityException {
KeyPairGenerator generator = SecurityUtils.getKeyPairGenerator(algorithm);
if (keySpec != null) {
generator.initialize(keySpec);
log.info("generateKeyPair({}) generating host key - spec={}", algorithm, keySpec.getClass().getSimpleName());
} else if (KeyUtils.EC_ALGORITHM.equals(algorithm)) {
ECCurves curve;
// If left to our own devices choose the biggest key size possible
if (keySize == 0) {
int numCurves = ECCurves.SORTED_KEY_SIZE.size();
curve = ECCurves.SORTED_KEY_SIZE.get(numCurves - 1);
} else {
curve = ECCurves.fromCurveSize(keySize);
if (curve == null) {
throw new InvalidKeyException("No match found for curve with key size=" + keySize);
}
}
generator.initialize(curve.getParameters());
log.info("generateKeyPair({}) generating host key={}", algorithm, curve);
} else if (keySize != 0) {
generator.initialize(keySize);
log.info("generateKeyPair({}) generating host key - size={}", algorithm, keySize);
} else {
log.info("generateKeyPair({}) generating host key", algorithm);
}
return generator.generateKeyPair();
}
}
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