Add helper for subscribing to callback events

Author: nightowlengineer

src/main/java/engineer/nightowl/sonos/api/util/SonosCallbackHelper.java

@@ -0,0 +1,79 @@
+package engineer.nightowl.sonos.api.util;
+
+import engineer.nightowl.sonos.api.SonosApiClient;
+import engineer.nightowl.sonos.api.exception.SonosApiClientException;
+import org.apache.http.Header;
+import org.apache.http.HttpMessage;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.Arrays;
+import java.util.Base64;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+public class SonosCallbackHelper
+{
+    private static final Logger logger = LoggerFactory.getLogger(SonosCallbackHelper.class);
+
+    /**
+     * Verify that the message was signed by Sonos.
+     *
+     * @param headers from the message
+     * @return true if the message is cryptographically provable to be from Sonos
+     * @throws SonosApiClientException if in an unsupported environment
+     */
+    public static Boolean verifySignature(final Map<String, String> headers, final String apiKey, final String apiSecret) throws SonosApiClientException
+    {
+        MessageDigest messageDigest = null;
+        try
+        {
+            messageDigest = MessageDigest.getInstance("SHA-256");
+        } catch (NoSuchAlgorithmException e)
+        {
+            throw new SonosApiClientException("Unsupported execution environment", e);
+        }
+
+        messageDigest.update(headers.get("X-Sonos-Event-Seq-Id").getBytes(UTF_8));
+        messageDigest.update(headers.get("X-Sonos-Namespace").getBytes(UTF_8));
+        messageDigest.update(headers.get("X-Sonos-Type").getBytes(UTF_8));
+        messageDigest.update(headers.get("X-Sonos-Target-Type").getBytes(UTF_8));
+        messageDigest.update(headers.get("X-Sonos-Target-Value").getBytes(UTF_8));
+        messageDigest.update(apiKey.getBytes(UTF_8));
+        messageDigest.update(apiSecret.getBytes(UTF_8));
+
+        final String signature = Base64.getUrlEncoder().withoutPadding().encodeToString(messageDigest.digest());
+
+        logger.debug("Verifying signature: " + signature);
+
+        return signature.equals(headers.get("X-Sonos-Event-Signature"));
+    }
+
+    public static Boolean verifySignature(final Map<String, String> headers, final SonosApiClient apiClient) throws SonosApiClientException
+    {
+        return SonosCallbackHelper.verifySignature(headers, apiClient.getConfiguration().getApiKey(), apiClient.getConfiguration().getApiSecret());
+    }
+
+    public static Boolean verifySignature(final HttpMessage message, final SonosApiClient apiClient) throws SonosApiClientException
+    {
+        return SonosCallbackHelper.verifySignature(message, apiClient.getConfiguration().getApiKey(), apiClient.getConfiguration().getApiSecret());
+    }
+
+    public static Boolean verifySignature(final HttpMessage message, final String apiKey, final String apiSecret) throws SonosApiClientException
+    {
+        // Map of headers - Name, Value
+        Map<String, String> headers = convertHeadersToMap(message.getAllHeaders());
+        return SonosCallbackHelper.verifySignature(headers, apiKey, apiSecret);
+    }
+
+    public static Map<String, String> convertHeadersToMap(final Header[] headers)
+    {
+        return Arrays
+                .stream(headers)
+                .collect(Collectors.toMap(Header::getName, Header::getValue));
+    }
+}

src/test/java/engineer/nightowl/sonos/api/util/SonosCallbackHelperTest.java

@@ -0,0 +1,56 @@
+package engineer.nightowl.sonos.api.util;
+
+import engineer.nightowl.sonos.api.exception.SonosApiClientException;
+import org.apache.http.entity.ContentType;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.security.NoSuchAlgorithmException;
+import java.util.HashMap;
+import java.util.Map;
+
+public class SonosCallbackHelperTest
+{
+    final String apiKey = "sonos";
+    final String apiSecret = "secret";
+
+    private Map<String, String> getHeaders()
+    {
+        final Map<String, String> headers = new HashMap<>();
+        headers.put("X-Sonos-Event-Seq-Id", "event-seq-id");
+        headers.put("X-Sonos-Namespace", "namespace");
+        headers.put("X-Sonos-Type", "type");
+        headers.put("X-Sonos-Target-Type", "target-type");
+        headers.put("X-Sonos-Target-Value", "target-value");
+        headers.put("Unrelated-Header", "sonos123");
+        headers.put("Content-Type", ContentType.APPLICATION_JSON.getMimeType());
+
+        return headers;
+    }
+
+    private Map<String, String> getValidHeaders()
+    {
+        final Map<String, String> headers = getHeaders();
+        headers.put("X-Sonos-Event-Signature", "n9V0MCdGYaOPy_dJb_nUPqw5dHiBSd_g0NOQTe4IaVI");
+        return headers;
+    }
+
+    private Map<String, String> getInvalidHeaders()
+    {
+        final Map<String, String> headers = getHeaders();
+        headers.put("X-Sonos-Event-Signature", "invalidSignature");
+        return headers;
+    }
+
+    @Test
+    public void testVerifySignatureWithValidHeaders() throws SonosApiClientException, NoSuchAlgorithmException
+    {
+        Assert.assertTrue(SonosCallbackHelper.verifySignature(getValidHeaders(), apiKey, apiSecret));
+    }
+
+    @Test
+    public void testVerifySignatureWithInvalidHeaders() throws SonosApiClientException, NoSuchAlgorithmException
+    {
+        Assert.assertFalse(SonosCallbackHelper.verifySignature(getInvalidHeaders(), apiKey, apiSecret));
+    }
+}