GoogleURLSigner.java

/*
 * Copyright (C) 2009  Camptocamp
 *
 * This file is part of MapFish Server
 *
 * MapFish Server is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * MapFish Server is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with MapFish Server.  If not, see <http://www.gnu.org/licenses/>.
 */

package org.mapfish.print.map.readers.google;

import java.io.UnsupportedEncodingException;
import java.net.URISyntaxException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;

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

import com.lowagie.text.pdf.codec.Base64;
import org.mapfish.print.config.Key;

public class GoogleURLSigner {
    // This variable stores the binary key, which is computed from the string
    // (Base64) key
    private byte[] key;
    private String clientId;

    public GoogleURLSigner(Key key) {
        this.clientId = key.getId();
        String keyString = key.getKey();
        // Convert the key from 'web safe' base 64 to binary
        keyString = keyString.replace('-', '+');
        keyString = keyString.replace('_', '/');
        this.key = Base64.decode(keyString);
    }

    public String signature(String resource)
            throws NoSuchAlgorithmException, InvalidKeyException,
            UnsupportedEncodingException, URISyntaxException {

        // Get an HMAC-SHA1 signing key from the raw key bytes
        SecretKeySpec sha1Key = new SecretKeySpec(key, "HmacSHA1");

        // Get an HMAC-SHA1 Mac instance and initialize it with the HMAC-SHA1
        // key
        Mac mac = Mac.getInstance("HmacSHA1");
        mac.init(sha1Key);

        // compute the binary signature for the request
        byte[] sigBytes = mac.doFinal(resource.getBytes());

        // base 64 encode the binary signature
        String signature = Base64.encodeBytes(sigBytes);

        // convert the signature to 'web safe' base 64
        signature = signature.replace('+', '-');
        signature = signature.replace('/', '_');

        return signature;
    }

    public String clientId() {
        return clientId;
    }
}