How can I test HMAC authentication using Dropwizard? - dropwizard

Question

I'm just getting started with Dropwizard 0.4.0, and I would like some help with HMAC authentication. Has anybody got any advice?
Thank you in advance.

Answer 1

At present Dropwizard doesn't support HMAC authentication right out of the box, so you'd have to write your own authenticator. A typical choice for HMAC authentication is to use the HTTP Authorization header. The following code expects this header in the following format:
Authorization: <algorithm> <apiKey> <digest>
An example would be
Authorization: HmacSHA1 abcd-efgh-1234 sdafkljlkansdaflk2354jlkj5345345dflkmsdf
The digest is built from the content of the body (marshalled entity) prior to URL encoding with the HMAC shared secret appended as base64. For a non-body request, such as GET or HEAD, the content is taken as the complete URI path and parameters with the secret key appended.
To implement this in a way that Dropwizard can work with it requires you to copy the BasicAuthenticator code present in the dropwizard-auth module into your own code and modify it with something like this:
import com.google.common.base.Optional;
import com.sun.jersey.api.core.HttpContext;
import com.sun.jersey.server.impl.inject.AbstractHttpContextInjectable;
import com.yammer.dropwizard.auth.AuthenticationException;
import com.yammer.dropwizard.auth.Authenticator;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.HttpHeaders;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
class HmacAuthInjectable<T> extends AbstractHttpContextInjectable<T> {
private static final String PREFIX = "HmacSHA1";
private static final String HEADER_VALUE = PREFIX + " realm=\"%s\"";
private final Authenticator<HmacCredentials, T> authenticator;
private final String realm;
private final boolean required;
HmacAuthInjectable(Authenticator<HmacCredentials, T> authenticator, String realm, boolean required) {
this.authenticator = authenticator;
this.realm = realm;
this.required = required;
}
public Authenticator<HmacCredentials, T> getAuthenticator() {
return authenticator;
}
public String getRealm() {
return realm;
}
public boolean isRequired() {
return required;
}
#Override
public T getValue(HttpContext c) {
try {
final String header = c.getRequest().getHeaderValue(HttpHeaders.AUTHORIZATION);
if (header != null) {
final String[] authTokens = header.split(" ");
if (authTokens.length != 3) {
// Malformed
HmacAuthProvider.LOG.debug("Error decoding credentials (length is {})", authTokens.length);
throw new WebApplicationException(Response.Status.BAD_REQUEST);
}
final String algorithm = authTokens[0];
final String apiKey = authTokens[1];
final String signature = authTokens[2];
final String contents;
// Determine which part of the request will be used for the content
final String method = c.getRequest().getMethod().toUpperCase();
if ("GET".equals(method) ||
"HEAD".equals(method) ||
"DELETE".equals(method)) {
// No entity so use the URI
contents = c.getRequest().getRequestUri().toString();
} else {
// Potentially have an entity (even in OPTIONS) so use that
contents = c.getRequest().getEntity(String.class);
}
final HmacCredentials credentials = new HmacCredentials(algorithm, apiKey, signature, contents);
final Optional<T> result = authenticator.authenticate(credentials);
if (result.isPresent()) {
return result.get();
}
}
} catch (IllegalArgumentException e) {
HmacAuthProvider.LOG.debug(e, "Error decoding credentials");
} catch (AuthenticationException e) {
HmacAuthProvider.LOG.warn(e, "Error authenticating credentials");
throw new WebApplicationException(Response.Status.INTERNAL_SERVER_ERROR);
}
if (required) {
throw new WebApplicationException(Response.status(Response.Status.UNAUTHORIZED)
.header(HttpHeaders.AUTHORIZATION,
String.format(HEADER_VALUE, realm))
.entity("Credentials are required to access this resource.")
.type(MediaType.TEXT_PLAIN_TYPE)
.build());
}
return null;
}
}
The above is not perfect, but it'll get you started. You may want to refer to the MultiBit Merchant release candidate source code (MIT license) for a more up to date version and the various supporting classes.
The next step is to integrate the authentication process into your ResourceTest subclass. Unfortunately, Dropwizard doesn't provide a good entry point for authentication providers in v0.4.0, so you may want to introduce your own base class, similar to this:
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
import com.sun.jersey.api.client.Client;
import com.sun.jersey.test.framework.AppDescriptor;
import com.sun.jersey.test.framework.JerseyTest;
import com.sun.jersey.test.framework.LowLevelAppDescriptor;
import com.xeiam.xchange.utils.CryptoUtils;
import com.yammer.dropwizard.bundles.JavaBundle;
import com.yammer.dropwizard.jersey.DropwizardResourceConfig;
import com.yammer.dropwizard.jersey.JacksonMessageBodyProvider;
import com.yammer.dropwizard.json.Json;
import org.codehaus.jackson.map.Module;
import org.junit.After;
import org.junit.Before;
import org.multibit.mbm.auth.hmac.HmacAuthProvider;
import org.multibit.mbm.auth.hmac.HmacAuthenticator;
import org.multibit.mbm.persistence.dao.UserDao;
import org.multibit.mbm.persistence.dto.User;
import org.multibit.mbm.persistence.dto.UserBuilder;
import java.io.UnsupportedEncodingException;
import java.security.GeneralSecurityException;
import java.util.List;
import java.util.Set;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;
/**
* A base test class for testing Dropwizard resources.
*/
public abstract class BaseResourceTest {
private final Set<Object> singletons = Sets.newHashSet();
private final Set<Object> providers = Sets.newHashSet();
private final List<Module> modules = Lists.newArrayList();
private JerseyTest test;
protected abstract void setUpResources() throws Exception;
protected void addResource(Object resource) {
singletons.add(resource);
}
public void addProvider(Object provider) {
providers.add(provider);
}
protected void addJacksonModule(Module module) {
modules.add(module);
}
protected Json getJson() {
return new Json();
}
protected Client client() {
return test.client();
}
#Before
public void setUpJersey() throws Exception {
setUpResources();
this.test = new JerseyTest() {
#Override
protected AppDescriptor configure() {
final DropwizardResourceConfig config = new DropwizardResourceConfig();
for (Object provider : JavaBundle.DEFAULT_PROVIDERS) { // sorry, Scala folks
config.getSingletons().add(provider);
}
for (Object provider : providers) {
config.getSingletons().add(provider);
}
Json json = getJson();
for (Module module : modules) {
json.registerModule(module);
}
config.getSingletons().add(new JacksonMessageBodyProvider(json));
config.getSingletons().addAll(singletons);
return new LowLevelAppDescriptor.Builder(config).build();
}
};
test.setUp();
}
#After
public void tearDownJersey() throws Exception {
if (test != null) {
test.tearDown();
}
}
/**
* #param contents The content to sign with the default HMAC process (POST body, GET resource path)
* #return
*/
protected String buildHmacAuthorization(String contents, String apiKey, String secretKey) throws UnsupportedEncodingException, GeneralSecurityException {
return String.format("HmacSHA1 %s %s",apiKey, CryptoUtils.computeSignature("HmacSHA1", contents, secretKey));
}
protected void setUpAuthenticator() {
User user = UserBuilder
.getInstance()
.setUUID("abc123")
.setSecretKey("def456")
.build();
//
UserDao userDao = mock(UserDao.class);
when(userDao.getUserByUUID("abc123")).thenReturn(user);
HmacAuthenticator authenticator = new HmacAuthenticator();
authenticator.setUserDao(userDao);
addProvider(new HmacAuthProvider<User>(authenticator, "REST"));
}
}
Again, the above code is not perfect, but the idea is to allow a mocked up UserDao to provide a standard user with a known shared secret key. You'd have to introduce your own UserBuilder implementation for testing purposes.
Finally, with the above code a Dropwizard Resource that had an endpoint like this:
import com.google.common.base.Optional;
import com.yammer.dropwizard.auth.Auth;
import com.yammer.metrics.annotation.Timed;
import org.multibit.mbm.core.Saying;
import org.multibit.mbm.persistence.dto.User;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import javax.ws.rs.core.MediaType;
import java.util.concurrent.atomic.AtomicLong;
#Path("/")
#Produces(MediaType.APPLICATION_JSON)
public class HelloWorldResource {
private final String template;
private final String defaultName;
private final AtomicLong counter;
public HelloWorldResource(String template, String defaultName) {
this.template = template;
this.defaultName = defaultName;
this.counter = new AtomicLong();
}
#GET
#Timed
#Path("/hello-world")
public Saying sayHello(#QueryParam("name") Optional<String> name) {
return new Saying(counter.incrementAndGet(),
String.format(template, name.or(defaultName)));
}
#GET
#Timed
#Path("/secret")
public Saying saySecuredHello(#Auth User user) {
return new Saying(counter.incrementAndGet(),
"You cracked the code!");
}
}
could be tested with a unit test that was configured like this:
import org.junit.Test;
import org.multibit.mbm.core.Saying;
import org.multibit.mbm.test.BaseResourceTest;
import javax.ws.rs.core.HttpHeaders;
import static org.junit.Assert.assertEquals;
public class HelloWorldResourceTest extends BaseResourceTest {
#Override
protected void setUpResources() {
addResource(new HelloWorldResource("Hello, %s!","Stranger"));
setUpAuthenticator();
}
#Test
public void simpleResourceTest() throws Exception {
Saying expectedSaying = new Saying(1,"Hello, Stranger!");
Saying actualSaying = client()
.resource("/hello-world")
.get(Saying.class);
assertEquals("GET hello-world returns a default",expectedSaying.getContent(),actualSaying.getContent());
}
#Test
public void hmacResourceTest() throws Exception {
String authorization = buildHmacAuthorization("/secret", "abc123", "def456");
Saying actual = client()
.resource("/secret")
.header(HttpHeaders.AUTHORIZATION, authorization)
.get(Saying.class);
assertEquals("GET secret returns unauthorized","You cracked the code!", actual.getContent());
}
}
Hope this helps you get started.