| /* |
| * 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.io.StreamCorruptedException; |
| import java.math.BigInteger; |
| import java.security.SignatureException; |
| import java.util.Map; |
| |
| import org.apache.sshd.common.keyprovider.KeyPairProvider; |
| import org.apache.sshd.common.session.SessionContext; |
| 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.io.der.DERParser; |
| import org.apache.sshd.common.util.io.der.DERWriter; |
| |
| /** |
| * DSA <code>Signature</code> |
| * |
| * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a> |
| * @see <A HREF="https://tools.ietf.org/html/rfc4253#section-6.6">RFC4253 section 6.6</A> |
| */ |
| public class SignatureDSA extends AbstractSignature { |
| public static final String DEFAULT_ALGORITHM = "SHA1withDSA"; |
| |
| public static final int DSA_SIGNATURE_LENGTH = 40; |
| // result must be 40 bytes, but length of r and s may not exceed 20 bytes |
| public static final int MAX_SIGNATURE_VALUE_LENGTH = DSA_SIGNATURE_LENGTH / 2; |
| |
| public SignatureDSA() { |
| this(DEFAULT_ALGORITHM); |
| } |
| |
| protected SignatureDSA(String algorithm) { |
| super(algorithm); |
| } |
| |
| @Override |
| public byte[] sign(SessionContext session) throws Exception { |
| byte[] sig = super.sign(session); |
| |
| try (DERParser parser = new DERParser(sig)) { |
| int type = parser.read(); |
| if (type != 0x30) { |
| throw new StreamCorruptedException( |
| "Invalid signature format - not a DER SEQUENCE: 0x" + Integer.toHexString(type)); |
| } |
| |
| // length of remaining encoding of the 2 integers |
| int remainLen = parser.readLength(); |
| /* |
| * There are supposed to be 2 INTEGERs, each encoded with: |
| * |
| * - one byte representing the fact that it is an INTEGER - one byte of the integer encoding length - at |
| * least one byte of integer data (zero length is not an option) |
| */ |
| if (remainLen < (2 * 3)) { |
| throw new StreamCorruptedException("Invalid signature format - not enough encoded data length: " + remainLen); |
| } |
| |
| BigInteger r = parser.readBigInteger(); |
| BigInteger s = parser.readBigInteger(); |
| |
| byte[] result = new byte[DSA_SIGNATURE_LENGTH]; |
| putBigInteger(r, result, 0); |
| putBigInteger(s, result, MAX_SIGNATURE_VALUE_LENGTH); |
| return result; |
| } |
| } |
| |
| public static void putBigInteger(BigInteger value, byte[] result, int offset) { |
| byte[] data = value.toByteArray(); |
| boolean maxExceeded = data.length > MAX_SIGNATURE_VALUE_LENGTH; |
| int dstOffset = maxExceeded ? 0 : (MAX_SIGNATURE_VALUE_LENGTH - data.length); |
| System.arraycopy(data, maxExceeded ? 1 : 0, |
| result, offset + dstOffset, |
| Math.min(MAX_SIGNATURE_VALUE_LENGTH, data.length)); |
| } |
| |
| @Override |
| public boolean verify(SessionContext session, byte[] sig) throws Exception { |
| int sigLen = NumberUtils.length(sig); |
| byte[] data = sig; |
| |
| if (sigLen != DSA_SIGNATURE_LENGTH) { |
| // probably some encoded data |
| Map.Entry<String, byte[]> encoding = extractEncodedSignature(sig, KeyPairProvider.SSH_DSS::equalsIgnoreCase); |
| if (encoding != null) { |
| String keyType = encoding.getKey(); |
| ValidateUtils.checkTrue( |
| KeyPairProvider.SSH_DSS.equals(keyType), "Mismatched key type: %s", keyType); |
| data = encoding.getValue(); |
| sigLen = NumberUtils.length(data); |
| } |
| } |
| |
| if (sigLen != DSA_SIGNATURE_LENGTH) { |
| throw new SignatureException("Bad signature length (" + sigLen + " instead of " + DSA_SIGNATURE_LENGTH + ")" |
| + " for " + BufferUtils.toHex(':', data)); |
| } |
| |
| byte[] rEncoding; |
| try (DERWriter w = new DERWriter(MAX_SIGNATURE_VALUE_LENGTH + 4)) { // in case length > 0x7F |
| w.writeBigInteger(data, 0, MAX_SIGNATURE_VALUE_LENGTH); |
| rEncoding = w.toByteArray(); |
| } |
| |
| byte[] sEncoding; |
| try (DERWriter w = new DERWriter(MAX_SIGNATURE_VALUE_LENGTH + 4)) { // in case length > 0x7F |
| w.writeBigInteger(data, MAX_SIGNATURE_VALUE_LENGTH, MAX_SIGNATURE_VALUE_LENGTH); |
| sEncoding = w.toByteArray(); |
| } |
| |
| int length = rEncoding.length + sEncoding.length; |
| byte[] encoded; |
| try (DERWriter w = new DERWriter(1 + length + 4)) { // in case length > 0x7F |
| w.write(0x30); // SEQUENCE |
| w.writeLength(length); |
| w.write(rEncoding); |
| w.write(sEncoding); |
| encoded = w.toByteArray(); |
| } |
| |
| return doVerify(encoded); |
| } |
| } |