content: /*
   * Copyright (C) 2019 The Android Open Source Project
   *
   * 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 com.android.ike.ikev2.message;
  
  import android.annotation.StringDef;
  
  import com.android.ike.ikev2.exceptions.AuthenticationFailedException;
  import com.android.ike.ikev2.exceptions.IkeException;
  import com.android.ike.ikev2.message.IkeAuthPayload.AuthMethod;
  
  import java.lang.annotation.Retention;
  import java.lang.annotation.RetentionPolicy;
  import java.nio.ByteBuffer;
  import java.util.Arrays;
  
  /**
   * IkeAuthDigitalSignPayload represents Authentication Payload using a specific or generic digital
   * signature authentication method.
   *
   * <p>If AUTH_METHOD_RSA_DIGITAL_SIGN is used, then the hash algorithm is SHA1. If
   * AUTH_METHOD_GENERIC_DIGITAL_SIGN is used, the signature algorihtm and hash algorithm are
   * extracted from authentication data.
   *
   * @see <a href="https://tools.ietf.org/html/rfc7296#section-3.8">RFC 7296, Internet Key Exchange
   *     Protocol Version 2 (IKEv2)</a>
   * @see <a href="https://tools.ietf.org/html/rfc7427">RFC 7427, Signature Authentication in the
   *     Internet Key Exchange Version 2 (IKEv2)</a>
   */
  public class IkeAuthDigitalSignPayload extends IkeAuthPayload {
  
      // Byte arrays of DER encoded identifier ASN.1 objects that indicates the algorithm used to
      // generate the signature, extracted from
      // <a href="https://tools.ietf.org/html/rfc7427#appendix-A"> RFC 7427. There is no need to
      // understand the encoding process. They are just constants to indicate the algorithm type.
      private static final byte[] PKI_ALGO_ID_DER_BYTES_RSA_SHA1 = {
          (byte) 0x30, (byte) 0x0d, (byte) 0x06, (byte) 0x09,
          (byte) 0x2a, (byte) 0x86, (byte) 0x48, (byte) 0x86,
          (byte) 0xf7, (byte) 0x0d, (byte) 0x01, (byte) 0x01,
          (byte) 0x05, (byte) 0x05, (byte) 0x00
      };
      private static final byte[] PKI_ALGO_ID_DER_BYTES_RSA_SHA2_256 = {
          (byte) 0x30, (byte) 0x0d, (byte) 0x06, (byte) 0x09,
          (byte) 0x2a, (byte) 0x86, (byte) 0x48, (byte) 0x86,
          (byte) 0xf7, (byte) 0x0d, (byte) 0x01, (byte) 0x01,
          (byte) 0x0b, (byte) 0x05, (byte) 0x00
      };
      private static final byte[] PKI_ALGO_ID_DER_BYTES_RSA_SHA2_384 = {
          (byte) 0x30, (byte) 0x0d, (byte) 0x06, (byte) 0x09,
          (byte) 0x2a, (byte) 0x86, (byte) 0x48, (byte) 0x86,
          (byte) 0xf7, (byte) 0x0d, (byte) 0x01, (byte) 0x01,
          (byte) 0x0c, (byte) 0x05, (byte) 0x00
      };
      private static final byte[] PKI_ALGO_ID_DER_BYTES_RSA_SHA2_512 = {
          (byte) 0x30, (byte) 0x0d, (byte) 0x06, (byte) 0x09,
          (byte) 0x2a, (byte) 0x86, (byte) 0x48, (byte) 0x86,
          (byte) 0xf7, (byte) 0x0d, (byte) 0x01, (byte) 0x01,
          (byte) 0x0d, (byte) 0x05, (byte) 0x00
      };
  
      // Length of ASN.1 object length field.
      private static final int SIGNATURE_ALGO_ASN1_LEN_LEN = 1;
  
      // Currently we only support RSA for signature algorithm.
      @Retention(RetentionPolicy.SOURCE)
      @StringDef({
          SIGNATURE_ALGO_RSA_SHA1,
          SIGNATURE_ALGO_RSA_SHA2_256,
          SIGNATURE_ALGO_RSA_SHA2_384,
          SIGNATURE_ALGO_RSA_SHA2_512
      })
      public @interface SignatureAlgo {}
  
      public static final String SIGNATURE_ALGO_RSA_SHA1 = "SHA1withRSA";
      public static final String SIGNATURE_ALGO_RSA_SHA2_256 = "SHA256withRSA";
      public static final String SIGNATURE_ALGO_RSA_SHA2_384 = "SHA384withRSA";
      public static final String SIGNATURE_ALGO_RSA_SHA2_512 = "SHA512withRSA";
      // TODO: Allow users to configure authentication method using @SignatureAlgo
  
      public final String signatureAlgoAndHash;
      public final byte[] signature;
  
      protected IkeAuthDigitalSignPayload(
              boolean critical, @AuthMethod int authMethod, byte[] authData) throws IkeException {
          super(critical, authMethod);
          switch (authMethod) {
              case AUTH_METHOD_RSA_DIGITAL_SIGN:
                  signatureAlgoAndHash = SIGNATURE_ALGO_RSA_SHA1;
                  signature = authData;
                  break;
              case AUTH_METHOD_GENERIC_DIGITAL_SIGN:
                  ByteBuffer inputBuffer = ByteBuffer.wrap(authData);
  
                  // Get signature algorithm.
                  int signAlgoLen = Byte.toUnsignedInt(inputBuffer.get());
                  byte[] signAlgoBytes = new byte[signAlgoLen];
                  inputBuffer.get(signAlgoBytes);
                  signatureAlgoAndHash = bytesToSignAlgoName(signAlgoBytes);
  
                  // Get signature.
                  signature = new byte[authData.length - SIGNATURE_ALGO_ASN1_LEN_LEN - signAlgoLen];
                  inputBuffer.get(signature);
                  break;
              default:
                  // Won't hit here.
                  throw new IllegalArgumentException("Unrecognized authentication method.");
          }
      }
  
      private String bytesToSignAlgoName(byte[] signAlgoBytes) throws AuthenticationFailedException {
          if (Arrays.equals(PKI_ALGO_ID_DER_BYTES_RSA_SHA1, signAlgoBytes)) {
              return SIGNATURE_ALGO_RSA_SHA1;
          } else if (Arrays.equals(PKI_ALGO_ID_DER_BYTES_RSA_SHA2_256, signAlgoBytes)) {
              return SIGNATURE_ALGO_RSA_SHA2_256;
          } else if (Arrays.equals(PKI_ALGO_ID_DER_BYTES_RSA_SHA2_384, signAlgoBytes)) {
              return SIGNATURE_ALGO_RSA_SHA2_384;
          } else if (Arrays.equals(PKI_ALGO_ID_DER_BYTES_RSA_SHA2_512, signAlgoBytes)) {
              return SIGNATURE_ALGO_RSA_SHA2_512;
          } else {
              throw new AuthenticationFailedException(
                      "Unrecognized ASN.1 objects for Signature algorithm and Hash");
          }
      }
  
      // TODO: Add methods for generating and validating signature.
  
      @Override
      protected void encodeAuthDataToByteBuffer(ByteBuffer byteBuffer) {
          // TODO: Implement it.
          throw new UnsupportedOperationException(
                  "It is not supported to encode a " + getTypeString());
      }
  
      @Override
      protected int getAuthDataLength() {
          // TODO: Implement it.
          throw new UnsupportedOperationException(
                  "It is not supported to get payload length of " + getTypeString());
      }
  
      @Override
      public String getTypeString() {
          return "Authentication-Digital-Signature Payload";
      }
  }
  