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feat: Java auth. Add new GOOGLE_MANAGED_KAFKA_AUTH_PRINCIPAL environment variable that allows users to provide the auth principal for credential types where it cannot be programmatically fetched #47

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feat: Java auth. Add new GOOGLE_MANAGED_KAFKA_AUTH_PRINCIPAL environment variable that allows users to provide the auth principal for credential types where it cannot be programmatically fetched #47

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19 changes: 17 additions & 2 deletions ...a-java-auth/src/main/java/com/google/cloud/hosted/kafka/auth/GcpLoginCallbackHandler.java
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Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,10 @@ abstract static class StubGoogleCredentials extends GoogleCredentials {
abstract String getAccount();
}

String getPrincipalFromEnvironmentVariable() {
return System.getenv("GOOGLE_MANAGED_KAFKA_AUTH_PRINCIPAL");
}

private static final String HEADER =
new Gson().toJson(ImmutableMap.of("typ", "JWT", "alg", "GOOG_OAUTH2_TOKEN"));

Expand Down Expand Up @@ -138,9 +142,20 @@ private void handleTokenCallback(OAuthBearerTokenCallback callback) throws IOExc
subject = ((StubGoogleCredentials) credentials).getAccount();
} else if (credentials instanceof IdTokenProvider) {
subject = parseGoogleIdToken((IdTokenProvider) credentials).getEmail();
} else {
throw new IOException("Unknown credentials type: " + credentials.getClass().getName());
}

// Allow overriding the principal via an environment variable. This is useful for
// credentials that do not support the getAccount() or similar method, such as
// Workforce Identity Federation
String envSubject = getPrincipalFromEnvironmentVariable();
if (envSubject != null && !envSubject.isEmpty()) {
subject = envSubject;
}
if (subject == null || subject.isEmpty()) {
throw new IOException("Unable to determine principal for credentials type: " + credentials.getClass().getName() +
". Please set the GOOGLE_MANAGED_KAFKA_AUTH_PRINCIPAL environment variable.");
}

credentials.refreshIfExpired();
AccessToken googleAccessToken = credentials.getAccessToken();
String kafkaToken = getKafkaAccessToken(googleAccessToken, subject);
Expand Down
92 changes: 85 additions & 7 deletions ...va-auth/src/test/java/com/google/cloud/hosted/kafka/auth/GcpLoginCallbackHandlerTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -56,10 +56,15 @@ public String getAccount() {
}
}

static class UnsupportedCredentials extends GoogleCredentials {}
static class UnsupportedCredentials extends GoogleCredentials {
@Override
public AccessToken refreshAccessToken() throws IOException {
return new AccessToken("fake-access-token", Date.from(Instant.now().plusSeconds(3600)));
}
}

public GcpLoginCallbackHandler createHandler(GoogleCredentials credentials) throws Exception {
GcpLoginCallbackHandler gcpLoginCallbackHandler = new GcpLoginCallbackHandler(credentials);
public GcpLoginCallbackHandlerWithEnv createHandler(GoogleCredentials credentials, String principal) throws Exception {
GcpLoginCallbackHandlerWithEnv gcpLoginCallbackHandler = new GcpLoginCallbackHandlerWithEnv(credentials, principal);
HashMap configs = new HashMap<String, Object>();
ArrayList jaasConfig = new ArrayList<AppConfigurationEntry>();
jaasConfig.add(
Expand All @@ -72,13 +77,27 @@ public GcpLoginCallbackHandler createHandler(GoogleCredentials credentials) thro
return gcpLoginCallbackHandler;
}

static class GcpLoginCallbackHandlerWithEnv extends GcpLoginCallbackHandler {
private final String principal;

GcpLoginCallbackHandlerWithEnv(GoogleCredentials credentials, String principal) {
super(credentials);
this.principal = principal;
}

@Override
String getPrincipalFromEnvironmentVariable() {
return principal;
}
}

@Test
public void success() throws Exception {
public void success_withSupportedCredentials() throws Exception {
Instant now = Instant.now();
OAuthBearerTokenCallback oauthBearerTokenCallback = new OAuthBearerTokenCallback();
Callback[] callbacks = {oauthBearerTokenCallback};

GcpLoginCallbackHandler gcpOAuthBearerLoginCallbackHandler = createHandler(new FakeGoogleCredentials());
GcpLoginCallbackHandler gcpOAuthBearerLoginCallbackHandler = createHandler(new FakeGoogleCredentials(), null);
gcpOAuthBearerLoginCallbackHandler.handle(callbacks);

OAuthBearerToken oauthBearerToken = oauthBearerTokenCallback.token();
Expand All @@ -102,11 +121,70 @@ public void success() throws Exception {
}

@Test
public void fail_unsupportedCredentialType() throws Exception {
// Test that we can override the principal when using a supported credentials type.
public void success_withSupportedCredentialsEnvPrincipalOverride() throws Exception {
Instant now = Instant.now();
OAuthBearerTokenCallback oauthBearerTokenCallback = new OAuthBearerTokenCallback();
Callback[] callbacks = {oauthBearerTokenCallback};

GcpLoginCallbackHandler gcpOAuthBearerLoginCallbackHandler = createHandler(new FakeGoogleCredentials(), "fake-environment-account@google.com");
gcpOAuthBearerLoginCallbackHandler.handle(callbacks);

OAuthBearerToken oauthBearerToken = oauthBearerTokenCallback.token();
SerializedJwt jwtToken = new SerializedJwt(oauthBearerToken.value());

Map<String, Object> header = OAuthBearerUnsecuredJws.toMap(jwtToken.getHeader());
Map<String, Object> payload = OAuthBearerUnsecuredJws.toMap(jwtToken.getPayload());

// Validate the JWT token is as expected by our server.
assertThat(header.get("typ")).isEqualTo("JWT");
assertThat(header.get("alg")).isEqualTo("GOOG_OAUTH2_TOKEN");

assertThat(payload.get("exp")).isInstanceOf(Integer.class);
assertThat(((int) payload.get("exp"))).isGreaterThan((int) now.getEpochSecond());

// The signature is the base64 encoded Google OAuth token.
assertThat(new String(Base64.getUrlDecoder().decode(jwtToken.getSignature()), UTF_8))
.isEqualTo("fake-access-token");
assertThat(oauthBearerToken.scope()).isEqualTo(ImmutableSet.of("kafka"));
assertThat(oauthBearerToken.principalName()).isEqualTo("fake-environment-account@google.com");
}

@Test
public void fail_withUnsupportedCredentialsNoEnvPrincipal() throws Exception {
OAuthBearerTokenCallback oauthBearerTokenCallback = new OAuthBearerTokenCallback();
Callback[] callbacks = {oauthBearerTokenCallback};

GcpLoginCallbackHandler gcpOAuthBearerLoginCallbackHandler = createHandler(new UnsupportedCredentials());
GcpLoginCallbackHandler gcpOAuthBearerLoginCallbackHandler = createHandler(new UnsupportedCredentials(), null);
assertThrows(IOException.class, () -> gcpOAuthBearerLoginCallbackHandler.handle(callbacks));
}

@Test
public void success_withUnsupportedCredentialsEnvPrincipal() throws Exception {
Instant now = Instant.now();
OAuthBearerTokenCallback oauthBearerTokenCallback = new OAuthBearerTokenCallback();
Callback[] callbacks = {oauthBearerTokenCallback};

GcpLoginCallbackHandler gcpOAuthBearerLoginCallbackHandler = createHandler(new UnsupportedCredentials(), "fake-environment-account@google.com");
gcpOAuthBearerLoginCallbackHandler.handle(callbacks);

OAuthBearerToken oauthBearerToken = oauthBearerTokenCallback.token();
SerializedJwt jwtToken = new SerializedJwt(oauthBearerToken.value());

Map<String, Object> header = OAuthBearerUnsecuredJws.toMap(jwtToken.getHeader());
Map<String, Object> payload = OAuthBearerUnsecuredJws.toMap(jwtToken.getPayload());

// Validate the JWT token is as expected by our server.
assertThat(header.get("typ")).isEqualTo("JWT");
assertThat(header.get("alg")).isEqualTo("GOOG_OAUTH2_TOKEN");

assertThat(payload.get("exp")).isInstanceOf(Integer.class);
assertThat(((int) payload.get("exp"))).isGreaterThan((int) now.getEpochSecond());

// The signature is the base64 encoded Google OAuth token.
assertThat(new String(Base64.getUrlDecoder().decode(jwtToken.getSignature()), UTF_8))
.isEqualTo("fake-access-token");
assertThat(oauthBearerToken.scope()).isEqualTo(ImmutableSet.of("kafka"));
assertThat(oauthBearerToken.principalName()).isEqualTo("fake-environment-account@google.com");
}
}