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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.common.signature;
import java.nio.charset.StandardCharsets;
import java.security.GeneralSecurityException;
import java.security.Key;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SignatureException;
import java.util.AbstractMap.SimpleImmutableEntry;
import java.util.Collection;
import java.util.Map;
import java.util.Objects;
import java.util.function.Predicate;
import org.apache.sshd.common.session.SessionContext;
import org.apache.sshd.common.util.GenericUtils;
import org.apache.sshd.common.util.NumberUtils;
import org.apache.sshd.common.util.ValidateUtils;
import org.apache.sshd.common.util.buffer.BufferUtils;
import org.apache.sshd.common.util.security.SecurityUtils;
/**
* Useful base class for {@link Signature} implementation
*
* @author Apache MINA SSHD Project
*/
public abstract class AbstractSignature implements Signature {
private java.security.Signature signatureInstance;
private final String algorithm;
protected AbstractSignature(String algorithm) {
this.algorithm = ValidateUtils.checkNotNullAndNotEmpty(algorithm, "No signature algorithm specified");
}
@Override
public final String getAlgorithm() {
return algorithm;
}
/**
* Initializes the internal signature instance
*
* @param session The {@link SessionContext} for calling this method - may be {@code null} if not
* called within a session context
* @param algo The signature's algorithm name
* @param key the {@link Key} that is provided for initialization - a {@link PrivateKey} for
* signing and a {@link PublicKey} for verification
* @param forSigning If {@code true} then it is being initialized for signing, otherwise for
* verifying a signature
* @return The {@link java.security.Signature} instance
* @throws GeneralSecurityException if failed to initialize
*/
protected java.security.Signature doInitSignature(
SessionContext session, String algo, Key key, boolean forSigning)
throws GeneralSecurityException {
return SecurityUtils.getSignature(algo);
}
/**
* @return The current {@link java.security.Signature} instance - {@code null} if not initialized
* @see #doInitSignature(SessionContext, String, Key, boolean)
*/
protected java.security.Signature getSignature() {
return signatureInstance;
}
@Override
public byte[] sign(SessionContext session) throws Exception {
java.security.Signature signature = Objects.requireNonNull(getSignature(), "Signature not initialized");
return signature.sign();
}
@Override
public void initVerifier(SessionContext session, PublicKey key) throws Exception {
String algo = getAlgorithm();
signatureInstance = Objects.requireNonNull(
doInitSignature(session, algo, key, false), "No signature instance create");
signatureInstance.initVerify(Objects.requireNonNull(key, "No public key provided"));
}
@Override
public void initSigner(SessionContext session, PrivateKey key) throws Exception {
String algo = getAlgorithm();
signatureInstance = Objects.requireNonNull(
doInitSignature(session, algo, key, true), "No signature instance create");
signatureInstance.initSign(Objects.requireNonNull(key, "No private key provided"));
}
@Override
public void update(SessionContext session, byte[] hash, int off, int len) throws Exception {
java.security.Signature signature = Objects.requireNonNull(getSignature(), "Signature not initialized");
signature.update(hash, off, len);
}
/**
* Makes an attempt to detect if the signature is encoded or pure data
*
* @param sig The original signature
* @param expectedTypes The expected encoded key types
* @return A {@link SimpleImmutableEntry} where first value is the key type and second value is the
* data - {@code null} if not encoded
*/
protected Map.Entry extractEncodedSignature(byte[] sig, Collection expectedTypes) {
return GenericUtils.isEmpty(expectedTypes) ? null : extractEncodedSignature(sig, expectedTypes::contains);
}
protected Map.Entry extractEncodedSignature(byte[] sig, Predicate typeSelector) {
int dataLen = NumberUtils.length(sig);
// if it is encoded then we must have at least 2 UINT32 values
if (dataLen < (2 * Integer.BYTES)) {
return null;
}
long keyTypeLen = BufferUtils.getUInt(sig, 0, dataLen);
// after the key type we MUST have data bytes
if (keyTypeLen >= (dataLen - Integer.BYTES)) {
return null;
}
int keyTypeStartPos = Integer.BYTES;
int keyTypeEndPos = keyTypeStartPos + (int) keyTypeLen;
int remainLen = dataLen - keyTypeEndPos;
// must have UINT32 with the data bytes length
if (remainLen < Integer.BYTES) {
return null;
}
long dataBytesLen = BufferUtils.getUInt(sig, keyTypeEndPos, remainLen);
// make sure reported number of bytes does not exceed available
if (dataBytesLen > (remainLen - Integer.BYTES)) {
return null;
}
String keyType = new String(sig, keyTypeStartPos, (int) keyTypeLen, StandardCharsets.UTF_8);
if (!typeSelector.test(keyType)) {
return null;
}
byte[] data = new byte[(int) dataBytesLen];
System.arraycopy(sig, keyTypeEndPos + Integer.BYTES, data, 0, (int) dataBytesLen);
return new SimpleImmutableEntry<>(keyType, data);
}
protected boolean doVerify(byte[] data) throws SignatureException {
java.security.Signature signature = Objects.requireNonNull(getSignature(), "Signature not initialized");
return signature.verify(data);
}
@Override
public String toString() {
return getClass().getSimpleName() + "[" + getAlgorithm() + "]";
}
}
