如何为Android中的Azure事件中心生成SAS令牌

Question

How can I generate a SAS Token in an Android application using the sas key from Azure Event Hubs?

I found this post, but the libraries are too outdated at this point to be useful: Generate Azure SAS Token on Android

================================================================================

Update: Adding code to illustrate how I am generating a sas token and sending messages to Azure - in response to @Peter Pan - MSFT

Imports:

import android.app.IntentService;
import android.content.Intent;
import android.os.IBinder;
import android.content.Context;
import android.util.Log;

import java.io.IOException;

import okhttp3.FormBody;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.RequestBody;
import okhttp3.Response;

import java.net.URLEncoder;
import java.text.SimpleDateFormat;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import android.util.Base64;

On intent start of background service:

@Override
    public void onHandleIntent(Intent intent){

        // Now recover the connection URL and the message content from the started intent
        url = intent.getStringExtra("URL");
        message = intent.getStringExtra("content");
        sasKey = intent.getStringExtra("sasKey");

        // Generate the sas token
        Log.i("sasKey",sasKey);
        Log.i("url",url);
        String token = generateSasToken();

        // Now send the message
        Log.i("sasToken",token);
        sendMessageOkHttp( message, url, token);
    }

Generating the sas token:

private String generateSasToken() {

        Log.i(TAG,"generating token");
        String targetUri;
        String token = null;
        Log.i(TAG,"received uri "+url);
        try {
            targetUri = URLEncoder
                    .encode(url.toLowerCase(), "UTF-8")
                    .toLowerCase();

            long expiresOnDate = System.currentTimeMillis();
            int expiresInMins = 60; // 1 hour
            expiresOnDate += expiresInMins * 60 * 1000;
            long expires = expiresOnDate / 1000;
            String toSign = targetUri + "\n" + expires;

            Log.i(TAG,"to Sign " + toSign);
            // Get an hmac_sha1 key from the raw key bytes
            byte[] keyBytes = sasKey.getBytes("UTF-8");
            SecretKeySpec signingKey = new SecretKeySpec(keyBytes, "HmacSHA256");

            // Get an hmac_sha1 Mac instance and initialize with the signing key
            Mac mac = Mac.getInstance("HmacSHA256");
            mac.init(signingKey);

            // Compute the hmac on input data bytes
            byte[] rawHmac = mac.doFinal(toSign.getBytes("UTF-8"));

            // Using android.util.Base64 for Android Studio instead of
            // Apache commons codec
            String signature = URLEncoder.encode(Base64.encodeToString(rawHmac, Base64.NO_WRAP), "UTF-8");

            // Construct authorization string
            token = "sig="
                    + signature + "&se=" + expires + "&skn=" + "android"+"&sr=" + targetUri;
        } catch (Exception e) {
                Log.i("sasGeneration","Exception Generating SaS : " + e.getMessage());

        }

        return token;
    }

Sending Message using OkHttp:

   public void sendMessageOkHttp(String dataPacket, String connectionString, String token){

        // Instantiate the OkHttp Client
        OkHttpClient client = new OkHttpClient();

        // Create the body of the message to be send
        RequestBody formBody = new FormBody.Builder()
                .add("message", dataPacket)
                .build();

        Log.i("ConnStr",connectionString);
        // Now create the request and post it
        Request request = new Request.Builder()
                .header("Authorization", token)
                .url(connectionString)
                .post(formBody)
                .build();
        Log.i(TAG,"about to send message");
        // Now try to send the message
        try {
            Log.i(TAG,"sending message....");
            Response response = client.newCall(request).execute();
            Log.i(TAG,"message sent");
            Log.i("Azure Response",String.valueOf(response.message()));
            Log.i("Azure Body",String.valueOf(response.networkResponse()));

            // Do something with the response.
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

This code compiles and the application runs. However, when I post a message to azure, the response I get is "Unauthorized". It seems as though I am generating the token correctly, what could be the problem?

I have checked the event hub permissions multiple times. And they seem correct too.

Answer 1

It sounds like you want to know how to generate a SAS Token of EventHub for Android. There is an offical tutorial Service Bus authentication with Shared Access Signatures which you can follow to generate the SAS token, and @Jambor-MSFT code for your referenced SO thread should works for your scenario without any Azure Java SDK. Please try, and if any error/exception got when you develop for android, please post for helping us analysis your real issue.

Answer 2

Here's the helper API from azure event-hubs java library to generate SASToken (public utility method: SharedAccessSignatureTokenProvider.generateSharedAccessSignature(...) ) :

• https://github.com/Azure/azure-event-hubs-java/blob/0.10.0/azure-eventhubs/src/main/java/com/microsoft/azure/servicebus/SharedAccessSignatureTokenProvider.java#L49