// 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 com.cloud.bridge.util;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

import org.apache.axis2.AxisFault;
import org.apache.commons.codec.binary.Base64;
import org.apache.log4j.Logger;

/**
 * Both the SOAP code and the DIME implementation in the REST servlet need
 * this authentication functionality.
 */
public class S3SoapAuth {
    protected final static Logger logger = Logger.getLogger(S3SoapAuth.class);

    public S3SoapAuth() {
    }

    public static void verifySignature(String givenSignature, String operation, String timestamp, String accessKey, String secretKey) throws AxisFault {
        // -> calculate RFC 2104 HMAC-SHA1 digest over the constructed string
        String signString = "AmazonS3" + operation + timestamp;
        String calSig = calculateRFC2104HMAC(signString, secretKey);

        if (null == calSig || !givenSignature.equals(calSig)) {
            logger.error("Signature mismatch, [" + givenSignature + "] [" + calSig + "] over [" + signString + "]");
            throw new AxisFault("Authentication signature mismatch on AccessKey: [" + accessKey + "] [" + operation + "]", "Client.SignatureDoesNotMatch");
        }
    }

    /**
     * Create a signature by the following method:
     *     new String( Base64( SHA1( key, byte array )))
     *
     * @param signIt    - the data to generate a keyed HMAC over
     * @param secretKey - the user's unique key for the HMAC operation
     * @return String   - the recalculated string
     */
    private static String calculateRFC2104HMAC(String signIt, String secretKey) {
        String result = null;
        try {
            SecretKeySpec key = new SecretKeySpec(secretKey.getBytes(), "HmacSHA1");
            Mac hmacSha1 = Mac.getInstance("HmacSHA1");
            hmacSha1.init(key);
            byte[] rawHmac = hmacSha1.doFinal(signIt.getBytes());
            result = new String(Base64.encodeBase64(rawHmac));

        } catch (Exception e) {
            logger.error("Failed to generate keyed HMAC on soap request: " + e.getMessage());
            return null;
        }
        return result.trim();
    }
}