Autenticación de la firma en un URL

import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Base64;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.TreeMap;

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

import org.omg.CosNaming.IstringHelper;


public class SignDemo {
	private static final String SIGN_SEP = "\n";
	private static final String OBS_PREFIX = "x-obs-";
	private static final String DEFAULT_ENCODING = "UTF-8";
	private static final List<String> SUB_RESOURCES = Collections.unmodifiableList(Arrays.asList(
			"CDNNotifyConfiguration", "acl", "append", "attname", "backtosource", "cors", "customdomain", "delete",
			"deletebucket", "directcoldaccess", "encryption", "inventory", "length", "lifecycle", "location", "logging",
			"metadata", "modify", "name", "notification", "partNumber", "policy", "position", "quota",
			"rename", "replication", "response-cache-control", "response-content-disposition",
			"response-content-encoding", "response-content-language", "response-content-type", "response-expires",
			"restore", " storageClass", "storagePolicy", "storageinfo", "tagging", "torrent", "truncate",
			"uploadId", "uploads", "versionId", "versioning", "versions", "website", "x-image-process",
			"x-image-save-bucket", "x-image-save-object", "x-obs-security-token"));
	private String ak;
	private String sk;
	 public String urlEncode(String input) throws UnsupportedEncodingException
    {
		return URLEncoder.encode(input, DEFAULT_ENCODING)
        .replaceAll("%7E", "~") //for browser
        .replaceAll("%2F", "/");
    }
	private String join(List<?> items, String delimiter)
    {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < items.size(); i++)
        {
	String item = items.get(i).toString();
            sb.append(item);
            if (i < items.size() - 1)
            {
                sb.append(delimiter);
            }
        }
        return sb.toString();
    }
	private boolean isValid(String input) {
		return input != null && !input.equals("");
	}
	public String hamcSha1(String input) throws NoSuchAlgorithmException, InvalidKeyException, UnsupportedEncodingException {
		SecretKeySpec signingKey = new SecretKeySpec(this.sk.getBytes(DEFAULT_ENCODING), "HmacSHA1");
		Mac mac = Mac.getInstance("HmacSHA1");
		mac.init(signingKey);
		return Base64.getEncoder().encodeToString(mac.doFinal(input.getBytes(DEFAULT_ENCODING)));
	}
	private String stringToSign(String httpMethod, Map<String, String[]> headers, Map<String, String> queries,
			String bucketName, String objectName) throws Exception{
		String contentMd5 = "";
		String contentType = "";
		String date = "";
		TreeMap<String, String> canonicalizedHeaders = new TreeMap<String, String>();
		String key;
		List<String> temp = new ArrayList<String>();
		for(Map.Entry<String, String[]> entry : headers.entrySet()) {
			key = entry.getKey();
			if(key == null || entry.getValue() == null || entry.getValue().length == 0) {
				continue;
			}
			key = key.trim().toLowerCase(Locale.ENGLISH);
			if(key.equals("content-md5")) {
				contentMd5 = entry.getValue()[0];
				continue;
			}
			if(key.equals("content-type")) {
				contentType = entry.getValue()[0];
				continue;
			}
			if(key.equals("date")) {
				date = entry.getValue()[0];
				continue;
			}
			if(key.startsWith(OBS_PREFIX)) {
				for(String value : entry.getValue()) {
					if(value != null) {
						temp.add(value.trim());
					}
				}
				canonicalizedHeaders.put(key, this.join(temp, ","));
				temp.clear();
			}
		}
		if(canonicalizedHeaders.containsKey("x-obs-date")) {
			date = "";
		}
		// handle method/content-md5/content-type/date
		StringBuilder stringToSign = new StringBuilder();
		stringToSign.append(httpMethod).append(SIGN_SEP)
			.append(contentMd5).append(SIGN_SEP)
			.append(contentType).append(SIGN_SEP)
			.append(date).append(SIGN_SEP);
		// handle canonicalizedHeaders
		for(Map.Entry<String, String> entry : canonicalizedHeaders.entrySet()) {
			stringToSign.append(entry.getKey()).append(":").append(entry.getValue()).append(SIGN_SEP);
		}
		// handle CanonicalizedResource
		stringToSign.append("/");
		if(this.isValid(bucketName)) {
			stringToSign.append(bucketName).append("/");
			if(this.isValid(objectName)) {
				stringToSign.append(this.urlEncode(objectName));
			}
		}
		TreeMap<String, String> canonicalizedResource = new TreeMap<String, String>();
		for(Map.Entry<String, String> entry : queries.entrySet()) {
			key = entry.getKey();
			if(key == null) {
				continue;
			}
			if(SUB_RESOURCES.contains(key)) {
				canonicalizedResource.put(key, entry.getValue());
			}
		}
		if(canonicalizedResource.size() > 0) {
			stringToSign.append("?");
			for(Map.Entry<String, String> entry : canonicalizedResource.entrySet()) {
				stringToSign.append(entry.getKey());
				if(this.isValid(entry.getValue())) {
					stringToSign.append("=").append(entry.getValue());
				}
                                stringToSign.append("&");
			}
                        stringToSign.deleteCharAt(stringToSign.length()-1);
		}
//		System.out.println(String.format("StringToSign:%s%s", SIGN_SEP, stringToSign.toString()));
		return stringToSign.toString();
	}
	public String headerSignature(String httpMethod, Map<String, String[]> headers, Map<String, String> queries,
			String bucketName, String objectName) throws Exception {

		//1. stringToSign
		String stringToSign = this.stringToSign(httpMethod, headers, queries, bucketName, objectName);
		//2. signature
		return String.format("OBS %s:%s", this.ak, this.hamcSha1(stringToSign));
	}
	public String querySignature(String httpMethod, Map<String, String[]> headers, Map<String, String> queries,
			String bucketName, String objectName, long expires) throws Exception {
		if(headers.containsKey("x-obs-date")) {
			headers.put("x-obs-date", new String[] {String.valueOf(expires)});
		}else {
			headers.put("date", new String[] {String.valueOf(expires)});
		}
		//1. stringToSign
		String stringToSign = this.stringToSign(httpMethod, headers, queries, bucketName, objectName);
		//2. signature
		return this.urlEncode(this.hamcSha1(stringToSign));
	}

        public String getURL(String endpoint, Map<String, String> queries,
                String bucketName, String objectName, String signature, long expires) {
                StringBuilder URL = new StringBuilder();
                URL.append("https://").append(bucketName).append(".").append(endpoint).append("/").        
                    append(objectName).append("?");    
                String key;    
                for (Map.Entry<String, String> entry : queries.entrySet()) {        
                    key = entry.getKey();        
                    if (key == null) {
                        continue;        
                    }
                    if (SUB_RESOURCES.contains(key)) {            
                        String value = entry.getValue();            
                        URL.append(key);            
                        if (value != null) {                
                            URL.append("=").append(value).append("&");            
                        } else {                
                            URL.append("&");            
                        }        
                    }    
                }    
                URL.append("AccessKeyId=").append(this.ak).append("&Expires=").append(expires).        
                    append("&Signature=").append(signature);    
                return URL.toString();
        }

	public static void main(String[] args) throws Exception {
		SignDemo demo = new SignDemo();
		demo.ak = "<your-access-key-id>";
		demo.sk = "<your-secret-key-id>";
                String endpoint = "<your-endpoint>";
		String bucketName = "bucket-test";
		String objectName = "hello.jpg";
// A header cannot be carried if you want to use a URL to access OBS through a browser. If a header is added to headers, the signature does not match. To use the headers, it must be processed by the client.
		Map<String, String[]> headers = new HashMap<String, String[]>();
		Map<String, String> queries = new HashMap<String, String>();
                //  Expiration time of the request message. Set it to expire in 24 hours.
                long expires = (System.currentTimeMillis() + 86400000L) / 1000;
                String signature = demo.querySignature("GET", headers, queries, bucketName, objectName, expires);
                System.out.println(signature);
                String URL = demo.getURL(endpoint, queries, bucketName, objectName, signature, expires);
                System.out.println(URL);
	}
}