Fetches access tokens from the Google Compute Engine metadata server. * *
These credentials use the IAM API to sign data. See {@link #sign(byte[])} for more details.
*/
public class ComputeEngineCredentials extends GoogleCredentials
implements ServiceAccountSigner, IdTokenProvider {
// Decrease timing margins on GCE.
// This is needed because GCE VMs maintain their own OAuth cache that expires T-4 mins, attempting
// to refresh a token before then, will yield the same stale token. To enable pre-emptive
// refreshes, the margins must be shortened. This shouldn't cause problems since the clock skew
// on the VM and metadata proxy should be non-existent.
static final Duration COMPUTE_EXPIRATION_MARGIN = Duration.ofMinutes(3);
static final Duration COMPUTE_REFRESH_MARGIN = Duration.ofMinutes(3).plusSeconds(45);
private static final Logger LOGGER = Logger.getLogger(ComputeEngineCredentials.class.getName());
static final String DEFAULT_METADATA_SERVER_URL = "http://metadata.google.internal";
static final String SIGN_BLOB_URL_FORMAT =
"https://iamcredentials.googleapis.com/v1/projects/-/serviceAccounts/%s:signBlob";
// Note: the explicit `timeout` and `tries` below is a workaround. The underlying
// issue is that resolving an unknown host on some networks will take
// 20-30 seconds; making this timeout short fixes the issue, but
// could lead to false negatives in the event that we are on GCE, but
// the metadata resolution was particularly slow. The latter case is
// "unlikely" since the expected 4-nines time is about 0.5 seconds.
// This allows us to limit the total ping maximum timeout to 1.5 seconds
// for developer desktop scenarios.
static final int MAX_COMPUTE_PING_TRIES = 3;
static final int COMPUTE_PING_CONNECTION_TIMEOUT_MS = 500;
private static final String METADATA_FLAVOR = "Metadata-Flavor";
private static final String GOOGLE = "Google";
private static final String WINDOWS = "windows";
private static final String LINUX = "linux";
private static final String PARSE_ERROR_PREFIX = "Error parsing token refresh response. ";
private static final String PARSE_ERROR_ACCOUNT = "Error parsing service account response. ";
private static final long serialVersionUID = -4113476462526554235L;
private final String transportFactoryClassName;
private final Collection Returns an explicit universe domain if it was provided during credential initialization.
*
* Returns the {@link Credentials#GOOGLE_DEFAULT_UNIVERSE} if universe domain endpoint is not
* found (404) or returns an empty string.
*
* Otherwise, returns universe domain from GCE metadata service.
*
* Any above value is cached for the credential lifetime.
*
* @throws IOException if a call to GCE metadata service was unsuccessful. Check if exception
* implements the {@link Retryable} and {@code isRetryable()} will return true if the
* operation may be retried.
* @return string representing a universe domain in the format some-domain.xyz
*/
@Override
public String getUniverseDomain() throws IOException {
if (isExplicitUniverseDomain()) {
return super.getUniverseDomain();
}
synchronized (this) {
if (this.universeDomainFromMetadata != null) {
return this.universeDomainFromMetadata;
}
}
String universeDomainFromMetadata = getUniverseDomainFromMetadata();
synchronized (this) {
this.universeDomainFromMetadata = universeDomainFromMetadata;
}
return universeDomainFromMetadata;
}
private String getUniverseDomainFromMetadata() throws IOException {
HttpResponse response = getMetadataResponse(getUniverseDomainUrl());
int statusCode = response.getStatusCode();
if (statusCode == HttpStatusCodes.STATUS_CODE_NOT_FOUND) {
return Credentials.GOOGLE_DEFAULT_UNIVERSE;
}
if (statusCode != HttpStatusCodes.STATUS_CODE_OK) {
IOException cause =
new IOException(
String.format(
"Unexpected Error code %s trying to get universe domain"
+ " from Compute Engine metadata for the default service account: %s",
statusCode, response.parseAsString()));
throw new GoogleAuthException(true, cause);
}
String responseString = response.parseAsString();
/* Earlier versions of MDS that supports universe_domain return empty string instead of GDU. */
if (responseString.isEmpty()) {
return Credentials.GOOGLE_DEFAULT_UNIVERSE;
}
return responseString;
}
/** Refresh the access token by getting it from the GCE metadata server */
@Override
public AccessToken refreshAccessToken() throws IOException {
HttpResponse response = getMetadataResponse(createTokenUrlWithScopes());
int statusCode = response.getStatusCode();
if (statusCode == HttpStatusCodes.STATUS_CODE_NOT_FOUND) {
throw new IOException(
String.format(
"Error code %s trying to get security access token from"
+ " Compute Engine metadata for the default service account. This may be because"
+ " the virtual machine instance does not have permission scopes specified."
+ " It is possible to skip checking for Compute Engine metadata by specifying the environment "
+ " variable "
+ DefaultCredentialsProvider.NO_GCE_CHECK_ENV_VAR
+ "=true.",
statusCode));
}
if (statusCode != HttpStatusCodes.STATUS_CODE_OK) {
throw new IOException(
String.format(
"Unexpected Error code %s trying to get security access"
+ " token from Compute Engine metadata for the default service account: %s",
statusCode, response.parseAsString()));
}
InputStream content = response.getContent();
if (content == null) {
// Throw explicitly here on empty content to avoid NullPointerException from parseAs call.
// Mock transports will have success code with empty content by default.
throw new IOException("Empty content from metadata token server request.");
}
GenericData responseData = response.parseAs(GenericData.class);
String accessToken =
OAuth2Utils.validateString(responseData, "access_token", PARSE_ERROR_PREFIX);
int expiresInSeconds =
OAuth2Utils.validateInt32(responseData, "expires_in", PARSE_ERROR_PREFIX);
long expiresAtMilliseconds = clock.currentTimeMillis() + expiresInSeconds * 1000;
return new AccessToken(accessToken, new Date(expiresAtMilliseconds));
}
/**
* Returns a Google ID Token from the metadata server on ComputeEngine
*
* @param targetAudience the aud: field the IdToken should include
* @param options list of Credential specific options for the token. For example, an IDToken for a
* ComputeEngineCredential could have the full formatted claims returned if
* IdTokenProvider.Option.FORMAT_FULL) is provided as a list option. Valid option values are:
* Passive: to check if SMBIOS variable is present and contains expected value. This
* step is platform specific:
*
* For Linux: check if the file "/sys/class/dmi/id/product_name" exists and contains a
* line that starts with Google.
*
* For Windows: to be implemented
*
* Other platforms: not supported
*
* This algorithm can be disabled with environment variable {@code
* DefaultCredentialsProvider.NO_GCE_CHECK_ENV_VAR} set to {@code true}. In this case, the
* algorithm will always return {@code false} Returns {@code true} if currently running on Google
* Compute Environment (GCE) or equivalent runtime. Returns {@code false} if detection fails,
* platform is not supported or if detection disabled using the environment variable.
*/
static synchronized boolean isOnGce(
HttpTransportFactory transportFactory, DefaultCredentialsProvider provider) {
// If the environment has requested that we do no GCE checks, return immediately.
if (Boolean.parseBoolean(provider.getEnv(DefaultCredentialsProvider.NO_GCE_CHECK_ENV_VAR))) {
return false;
}
boolean result = pingComputeEngineMetadata(transportFactory, provider);
if (!result) {
result = checkStaticGceDetection(provider);
}
if (!result) {
LOGGER.log(Level.FINE, "Failed to detect whether running on Google Compute Engine.");
}
return result;
}
@VisibleForTesting
static boolean checkProductNameOnLinux(BufferedReader reader) throws IOException {
String name = reader.readLine().trim();
return name.startsWith(GOOGLE);
}
@VisibleForTesting
static boolean checkStaticGceDetection(DefaultCredentialsProvider provider) {
String osName = provider.getOsName();
try {
if (osName.startsWith(LINUX)) {
// Checks GCE residency on Linux platform.
File linuxFile = new File("/sys/class/dmi/id/product_name");
return checkProductNameOnLinux(
new BufferedReader(new InputStreamReader(provider.readStream(linuxFile))));
} else if (osName.startsWith(WINDOWS)) {
// Checks GCE residency on Windows platform.
// TODO: implement registry check via FFI
return false;
}
} catch (IOException e) {
LOGGER.log(Level.FINE, "Encountered an unexpected exception when checking SMBIOS value", e);
return false;
}
// Platforms other than Linux and Windows are not supported.
return false;
}
private static boolean pingComputeEngineMetadata(
HttpTransportFactory transportFactory, DefaultCredentialsProvider provider) {
GenericUrl tokenUrl = new GenericUrl(getMetadataServerUrl(provider));
for (int i = 1; i <= MAX_COMPUTE_PING_TRIES; ++i) {
try {
HttpRequest request =
transportFactory.create().createRequestFactory().buildGetRequest(tokenUrl);
request.setConnectTimeout(COMPUTE_PING_CONNECTION_TIMEOUT_MS);
request.getHeaders().set(METADATA_FLAVOR, GOOGLE);
HttpResponse response = request.execute();
try {
// Internet providers can return a generic response to all requests, so it is necessary
// to check that metadata header is present also.
HttpHeaders headers = response.getHeaders();
return OAuth2Utils.headersContainValue(headers, METADATA_FLAVOR, GOOGLE);
} finally {
response.disconnect();
}
} catch (SocketTimeoutException expected) {
// Ignore logging timeouts which is the expected failure mode in non GCE environments.
} catch (IOException e) {
LOGGER.log(
Level.FINE,
"Encountered an unexpected exception when checking"
+ " if running on Google Compute Engine using Metadata Service ping.",
e);
}
}
return false;
}
public static String getMetadataServerUrl(DefaultCredentialsProvider provider) {
String metadataServerAddress =
provider.getEnv(DefaultCredentialsProvider.GCE_METADATA_HOST_ENV_VAR);
if (metadataServerAddress != null) {
return "http://" + metadataServerAddress;
}
return DEFAULT_METADATA_SERVER_URL;
}
public static String getMetadataServerUrl() {
return getMetadataServerUrl(DefaultCredentialsProvider.DEFAULT);
}
public static String getTokenServerEncodedUrl(DefaultCredentialsProvider provider) {
return getMetadataServerUrl(provider)
+ "/computeMetadata/v1/instance/service-accounts/default/token";
}
public static String getTokenServerEncodedUrl() {
return getTokenServerEncodedUrl(DefaultCredentialsProvider.DEFAULT);
}
public static String getUniverseDomainUrl() {
return getMetadataServerUrl(DefaultCredentialsProvider.DEFAULT)
+ "/computeMetadata/v1/universe/universe_domain";
}
public static String getServiceAccountsUrl() {
return getMetadataServerUrl(DefaultCredentialsProvider.DEFAULT)
+ "/computeMetadata/v1/instance/service-accounts/?recursive=true";
}
public static String getIdentityDocumentUrl() {
return getMetadataServerUrl(DefaultCredentialsProvider.DEFAULT)
+ "/computeMetadata/v1/instance/service-accounts/default/identity";
}
@Override
public int hashCode() {
return Objects.hash(transportFactoryClassName);
}
@Override
protected ToStringHelper toStringHelper() {
synchronized (this) {
return super.toStringHelper()
.add("transportFactoryClassName", transportFactoryClassName)
.add("scopes", scopes)
.add("universeDomainFromMetadata", universeDomainFromMetadata);
}
}
@Override
public boolean equals(Object obj) {
if (!(obj instanceof ComputeEngineCredentials)) {
return false;
}
if (!super.equals(obj)) {
return false;
}
ComputeEngineCredentials other = (ComputeEngineCredentials) obj;
return Objects.equals(this.transportFactoryClassName, other.transportFactoryClassName)
&& Objects.equals(this.scopes, other.scopes)
&& Objects.equals(this.universeDomainFromMetadata, other.universeDomainFromMetadata);
}
private void readObject(ObjectInputStream input) throws IOException, ClassNotFoundException {
input.defaultReadObject();
transportFactory = newInstance(transportFactoryClassName);
}
@Override
public Builder toBuilder() {
return new Builder(this);
}
public static Builder newBuilder() {
return new Builder();
}
/**
* Returns the email address associated with the GCE default service account.
*
* @throws RuntimeException if the default service account cannot be read
*/
@Override
// todo(#314) getAccount should not throw a RuntimeException
public String getAccount() {
if (serviceAccountEmail == null) {
try {
serviceAccountEmail = getDefaultServiceAccount();
} catch (IOException ex) {
throw new RuntimeException("Failed to get service account", ex);
}
}
return serviceAccountEmail;
}
/**
* Signs the provided bytes using the private key associated with the service account.
*
* The Compute Engine's project must enable the Identity and Access Management (IAM) API and
* the instance's service account must have the iam.serviceAccounts.signBlob permission.
*
* @param toSign bytes to sign
* @return signed bytes
* @throws SigningException if the attempt to sign the provided bytes failed
* @see Blob
* Signing
*/
@Override
public byte[] sign(byte[] toSign) {
try {
String account = getAccount();
return IamUtils.sign(
account, this, transportFactory.create(), toSign, Collections.
* IdTokenProvider.Option.FORMAT_FULL
* IdTokenProvider.Option.LICENSES_TRUE
* If no options are set, the defaults are "&format=standard&licenses=false"
* @throws IOException if the attempt to get an IdToken failed
* @return IdToken object which includes the raw id_token, JsonWebSignature
*/
@Override
public IdToken idTokenWithAudience(String targetAudience, List
* Active: to check that GCE Metadata service is present by sending a http request to send
* a request to {@code ComputeEngineCredentials.DEFAULT_METADATA_SERVER_URL}
*
*