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Google Auth Library

Open source authentication client library for Java.

• API Documentation

This project consists of 3 artifacts:

• google-auth-library-credentials: contains base classes and interfaces for Google credentials
• google-auth-library-appengine: contains App Engine credentials. This artifact depends on the App Engine SDK.
• google-auth-library-oauth2-http: contains a wide variety of credentials as well as utility methods to create them and to get Application Default Credentials

Table of contents:

• Quickstart

• google-auth-library-oauth2-http

  • Application Default Credentials
  • ImpersonatedCredentials
  • Workload Identity Federation
    • Accessing resources from AWS
    • Accessing resources from Azure
    • Accessing resources from an OIDC identity provider
    • Accessing resources using Executable-sourced credentials
  • Workforce Identity Federation
    • Accessing resources using an OIDC or SAML 2.0 identity provider
    • Accessing resources using Executable-sourced credentials
  • Downscoping with Credential Access Boundaries
  • Configuring a Proxy
  • Using Credentials with google-http-client
  • Verifying JWT Tokens

• google-auth-library-credentials

• google-auth-library-appengine

• CI Status

• Contributing

• License

Quickstart

If you are using Maven, add this to your pom.xml file (notice that you can replace google-auth-library-oauth2-http with any of google-auth-library-credentials and google-auth-library-appengine, depending on your application needs):

<dependency>
  <groupId>com.google.auth</groupId>
  <artifactId>google-auth-library-oauth2-http</artifactId>
  <version>1.3.0</version>
</dependency>

If you are using Gradle, add this to your dependencies

implementation 'com.google.auth:google-auth-library-oauth2-http:1.3.0'

If you are using SBT, add this to your dependencies

libraryDependencies += "com.google.auth" % "google-auth-library-oauth2-http" % "1.3.0"

google-auth-library-oauth2-http

Application Default Credentials

This library provides an implementation of Application Default Credentials for Java. The Application Default Credentials provide a simple way to get authorization credentials for use in calling Google APIs.

They are best suited for cases when the call needs to have the same identity and authorization level for the application independent of the user. This is the recommended approach to authorize calls to Cloud APIs, particularly when you're building an application that uses Google Cloud Platform.

Application Default Credentials also support workload identity federation to access Google Cloud resources from non-Google Cloud platforms including Amazon Web Services (AWS), Microsoft Azure or any identity provider that supports OpenID Connect (OIDC). Workload identity federation is recommended for non-Google Cloud environments as it avoids the need to download, manage and store service account private keys locally, see: Workload Identity Federation.

Getting Application Default Credentials

To get Application Default Credentials use GoogleCredentials.getApplicationDefault() or GoogleCredentials.getApplicationDefault(HttpTransportFactory). These methods return the Application Default Credentials which are used to identify and authorize the whole application. The following are searched (in order) to find the Application Default Credentials:

1. Credentials file pointed to by the GOOGLE_APPLICATION_CREDENTIALS environment variable
2. Credentials provided by the Google Cloud SDK gcloud auth application-default login command
3. Google App Engine built-in credentials
4. Google Cloud Shell built-in credentials
5. Google Compute Engine built-in credentials
   • Skip this check by setting the environment variable NO_GCE_CHECK=true
   • Customize the GCE metadata server address by setting the environment variable GCE_METADATA_HOST=<hostname>

Explicit Credential Loading

To get Credentials from a Service Account JSON key use GoogleCredentials.fromStream(InputStream) or GoogleCredentials.fromStream(InputStream, HttpTransportFactory). Note that the credentials must be refreshed before the access token is available.

GoogleCredentials credentials = GoogleCredentials.fromStream(new FileInputStream("/path/to/credentials.json"));
credentials.refreshIfExpired();
AccessToken token = credentials.getAccessToken();
// OR
AccessToken token = credentials.refreshAccessToken();

ImpersonatedCredentials

Allows a credentials issued to a user or service account to impersonate another. The source project using ImpersonatedCredentials must enable the "IAMCredentials" API. Also, the target service account must grant the orginating principal the "Service Account Token Creator" IAM role.

String credPath = "/path/to/svc_account.json";
ServiceAccountCredentials sourceCredentials = ServiceAccountCredentials
     .fromStream(new FileInputStream(credPath));
sourceCredentials = (ServiceAccountCredentials) sourceCredentials
    .createScoped(Arrays.asList("https://www.googleapis.com/auth/iam"));

ImpersonatedCredentials targetCredentials = ImpersonatedCredentials.create(sourceCredentials,
    "impersonated-account@project.iam.gserviceaccount.com", null,
    Arrays.asList("https://www.googleapis.com/auth/devstorage.read_only"), 300);

Storage storage_service = StorageOptions.newBuilder().setProjectId("project-id")
    .setCredentials(targetCredentials).build().getService();

for (Bucket b : storage_service.list().iterateAll())
    System.out.println(b); 

Workload Identity Federation

Using workload identity federation, your application can access Google Cloud resources from Amazon Web Services (AWS), Microsoft Azure, or any identity provider that supports OpenID Connect (OIDC).

Traditionally, applications running outside Google Cloud have used service account keys to access Google Cloud resources. Using identity federation, your workload can impersonate a service account. This lets the external workload access Google Cloud resources directly, eliminating the maintenance and security burden associated with service account keys.

Accessing resources from AWS

In order to access Google Cloud resources from Amazon Web Services (AWS), the following requirements are needed:

• A workload identity pool needs to be created.
• AWS needs to be added as an identity provider in the workload identity pool (the Google organization policy needs to allow federation from AWS).
• Permission to impersonate a service account needs to be granted to the external identity.

Follow the detailed instructions on how to configure workload identity federation from AWS.

After configuring the AWS provider to impersonate a service account, a credential configuration file needs to be generated. Unlike service account credential files, the generated credential configuration file contains non-sensitive metadata to instruct the library on how to retrieve external subject tokens and exchange them for service account access tokens. The configuration file can be generated by using the gcloud CLI.

To generate the AWS workload identity configuration, run the following command:

# Generate an AWS configuration file.
gcloud iam workload-identity-pools create-cred-config \
    projects/$PROJECT_NUMBER/locations/global/workloadIdentityPools/$POOL_ID/providers/$AWS_PROVIDER_ID \
    --service-account $SERVICE_ACCOUNT_EMAIL \
    --aws \
    --output-file /path/to/generated/config.json

Where the following variables need to be substituted:

• $PROJECT_NUMBER: The Google Cloud project number.
• $POOL_ID: The workload identity pool ID.
• $AWS_PROVIDER_ID: The AWS provider ID.
• $SERVICE_ACCOUNT_EMAIL: The email of the service account to impersonate.

This generates the configuration file in the specified output file.

If you are using AWS IMDSv2, an additional flag --enable-imdsv2 needs to be added to the gcloud iam workload-identity-pools create-cred-config command:

gcloud iam workload-identity-pools create-cred-config \
    projects/$PROJECT_NUMBER/locations/global/workloadIdentityPools/$POOL_ID/providers/$AWS_PROVIDER_ID \
    --service-account $SERVICE_ACCOUNT_EMAIL \
    --aws \
    --output-file /path/to/generated/config.json \
    --enable-imdsv2

You can now use the Auth library to call Google Cloud resources from AWS.

Access resources from Microsoft Azure

In order to access Google Cloud resources from Microsoft Azure, the following requirements are needed:

• A workload identity pool needs to be created.
• Azure needs to be added as an identity provider in the workload identity pool (the Google organization policy needs to allow federation from Azure).
• The Azure tenant needs to be configured for identity federation.
• Permission to impersonate a service account needs to be granted to the external identity.

Follow the detailed instructions on how to configure workload identity federation from Microsoft Azure.

After configuring the Azure provider to impersonate a service account, a credential configuration file needs to be generated. Unlike service account credential files, the generated credential configuration file contains non-sensitive metadata to instruct the library on how to retrieve external subject tokens and exchange them for service account access tokens. The configuration file can be generated by using the gcloud CLI.

To generate the Azure workload identity configuration, run the following command:

# Generate an Azure configuration file.
gcloud iam workload-identity-pools create-cred-config \
    projects/$PROJECT_NUMBER/locations/global/workloadIdentityPools/$POOL_ID/providers/$AZURE_PROVIDER_ID \
    --service-account $SERVICE_ACCOUNT_EMAIL \
    --azure \
    --output-file /path/to/generated/config.json

Where the following variables need to be substituted:

• $PROJECT_NUMBER: The Google Cloud project number.
• $POOL_ID: The workload identity pool ID.
• $AZURE_PROVIDER_ID: The Azure provider ID.
• $SERVICE_ACCOUNT_EMAIL: The email of the service account to impersonate.

This generates the configuration file in the specified output file.

You can now use the Auth library to call Google Cloud resources from Azure.

Accessing resources from an OIDC identity provider

In order to access Google Cloud resources from an identity provider that supports OpenID Connect (OIDC), the following requirements are needed:

• A workload identity pool needs to be created.
• An OIDC identity provider needs to be added in the workload identity pool (the Google organization policy needs to allow federation from the identity provider).
• Permission to impersonate a service account needs to be granted to the external identity.

Follow the detailed instructions on how to configure workload identity federation from an OIDC identity provider.

After configuring the OIDC provider to impersonate a service account, a credential configuration file needs to be generated. Unlike service account credential files, the generated credential configuration file contains non-sensitive metadata to instruct the library on how to retrieve external subject tokens and exchange them for service account access tokens. The configuration file can be generated by using the gcloud CLI.

For OIDC providers, the Auth library can retrieve OIDC tokens either from a local file location (file-sourced credentials) or from a local server (URL-sourced credentials).

File-sourced credentials For file-sourced credentials, a background process needs to be continuously refreshing the file location with a new OIDC token prior to expiration. For tokens with one hour lifetimes, the token needs to be updated in the file every hour. The token can be stored directly as plain text or in JSON format.

To generate a file-sourced OIDC configuration, run the following command:

# Generate an OIDC configuration file for file-sourced credentials.
gcloud iam workload-identity-pools create-cred-config \
    projects/$PROJECT_NUMBER/locations/global/workloadIdentityPools/$POOL_ID/providers/$OIDC_PROVIDER_ID \
    --service-account $SERVICE_ACCOUNT_EMAIL \
    --credential-source-file $PATH_TO_OIDC_ID_TOKEN \
    # Optional arguments for file types. Default is "text":
    # --credential-source-type "json" \
    # Optional argument for the field that contains the OIDC credential.
    # This is required for json.
    # --credential-source-field-name "id_token" \
    --output-file /path/to/generated/config.json

Where the following variables need to be substituted:

• $PROJECT_NUMBER: The Google Cloud project number.
• $POOL_ID: The workload identity pool ID.
• $OIDC_PROVIDER_ID: The OIDC provider ID.
• $SERVICE_ACCOUNT_EMAIL: The email of the service account to impersonate.
• $PATH_TO_OIDC_ID_TOKEN: The file path used to retrieve the OIDC token.

This generates the configuration file in the specified output file.

URL-sourced credentials For URL-sourced credentials, a local server needs to host a GET endpoint to return the OIDC token. The response can be in plain text or JSON. Additional required request headers can also be specified.

To generate a URL-sourced OIDC workload identity configuration, run the following command:

# Generate an OIDC configuration file for URL-sourced credentials.
gcloud iam workload-identity-pools create-cred-config \
    projects/$PROJECT_NUMBER/locations/global/workloadIdentityPools/$POOL_ID/providers/$OIDC_PROVIDER_ID \
    --service-account $SERVICE_ACCOUNT_EMAIL \
    --credential-source-url $URL_TO_GET_OIDC_TOKEN \
    --credential-source-headers $HEADER_KEY=$HEADER_VALUE \
    # Optional arguments for file types. Default is "text":
    # --credential-source-type "json" \
    # Optional argument for the field that contains the OIDC credential.
    # This is required for json.
    # --credential-source-field-name "id_token" \
    --output-file /path/to/generated/config.json

Where the following variables need to be substituted:

• $PROJECT_NUMBER: The Google Cloud project number.
• $POOL_ID: The workload identity pool ID.
• $OIDC_PROVIDER_ID: The OIDC provider ID.
• $SERVICE_ACCOUNT_EMAIL: The email of the service account to impersonate.
• $URL_TO_GET_OIDC_TOKEN: The URL of the local server endpoint to call to retrieve the OIDC token.
• $HEADER_KEY and $HEADER_VALUE: The additional header key/value pairs to pass along the GET request to $URL_TO_GET_OIDC_TOKEN, e.g. Metadata-Flavor=Google.

You can now use the Auth library to call Google Cloud resources from an OIDC provider.

Using Executable-sourced credentials with OIDC and SAML

Executable-sourced credentials For executable-sourced credentials, a local executable is used to retrieve the 3rd party token. The executable must handle providing a valid, unexpired OIDC ID token or SAML assertion in JSON format to stdout.

To use executable-sourced credentials, the GOOGLE_EXTERNAL_ACCOUNT_ALLOW_EXECUTABLES environment variable must be set to 1.

To generate an executable-sourced workload identity configuration, run the following command:

# Generate a configuration file for executable-sourced credentials.
gcloud iam workload-identity-pools create-cred-config \
    projects/$PROJECT_NUMBER/locations/global/workloadIdentityPools/$POOL_ID/providers/$PROVIDER_ID \
    --service-account=$SERVICE_ACCOUNT_EMAIL \
    --subject-token-type=$SUBJECT_TOKEN_TYPE \
    # The absolute path for the program, including arguments.
    # e.g. --executable-command="/path/to/command --foo=bar"
    --executable-command=$EXECUTABLE_COMMAND \
    # Optional argument for the executable timeout. Defaults to 30s.
    # --executable-timeout-millis=$EXECUTABLE_TIMEOUT \
    # Optional argument for the absolute path to the executable output file.
    # See below on how this argument impacts the library behaviour.
    # --executable-output-file=$EXECUTABLE_OUTPUT_FILE \
    --output-file /path/to/generated/config.json

Where the following variables need to be substituted:

• $PROJECT_NUMBER: The Google Cloud project number.
• $POOL_ID: The workload identity pool ID.
• $PROVIDER_ID: The OIDC or SAML provider ID.
• $SERVICE_ACCOUNT_EMAIL: The email of the service account to impersonate.
• $SUBJECT_TOKEN_TYPE: The subject token type.
• $EXECUTABLE_COMMAND: The full command to run, including arguments. Must be an absolute path to the program.

The --executable-timeout-millis flag is optional. This is the duration for which the auth library will wait for the executable to finish, in milliseconds. Defaults to 30 seconds when not provided. The maximum allowed value is 2 minutes. The minimum is 5 seconds.

The --executable-output-file flag is optional. If provided, the file path must point to the 3PI credential response generated by the executable. This is useful for caching the credentials. By specifying this path, the Auth libraries will first check for its existence before running the executable. By caching the executable JSON response to this file, it improves performance as it avoids the need to run the executable until the cached credentials in the output file are expired. The executable must handle writing to this file - the auth libraries will only attempt to read from this location. The format of contents in the file should match the JSON format expected by the executable shown below.

To retrieve the 3rd party token, the library will call the executable using the command specified. The executable's output must adhere to the response format specified below. It must output the response to stdout.

A sample successful executable OIDC response:

{
  "version": 1,
  "success": true,
  "token_type": "urn:ietf:params:oauth:token-type:id_token",
  "id_token": "HEADER.PAYLOAD.SIGNATURE",
  "expiration_time": 1620499962
}

A sample successful executable SAML response:

{
  "version": 1,
  "success": true,
  "token_type": "urn:ietf:params:oauth:token-type:saml2",
  "saml_response": "...",
  "expiration_time": 1620499962
}

A sample executable error response:

{
  "version": 1,
  "success": false,
  "code": "401",
  "message": "Caller not authorized."
}

These are all required fields for an error response. The code and message fields will be used by the library as part of the thrown exception.

For successful responses, the expiration_time field is only required when an output file is specified in the credential configuration.

Response format fields summary:

• version: The version of the JSON output. Currently only version 1 is supported.
• success: When true, the response must contain the 3rd party token and token type. The response must also contain the expiration_time field if an output file was specified in the credential configuration. The executable must also exit with exit code 0. When false, the response must contain the error code and message fields and exit with a non-zero value.
• token_type: The 3rd party subject token type. Must be urn:ietf:params:oauth:token-type:jwt, urn:ietf:params:oauth:token-type:id_token, or urn:ietf:params:oauth:token-type:saml2.
• id_token: The 3rd party OIDC token.
• saml_response: The 3rd party SAML response.
• expiration_time: The 3rd party subject token expiration time in seconds (unix epoch time).
• code: The error code string.
• message: The error message.

All response types must include both the version and success fields.

• Successful responses must include the token_type and one of id_token or saml_response. The expiration_time field must also be present if an output file was specified in the credential configuration.
• Error responses must include both the code and message fields.

The library will populate the following environment variables when the executable is run:

• GOOGLE_EXTERNAL_ACCOUNT_AUDIENCE: The audience field from the credential configuration. Always present.
• GOOGLE_EXTERNAL_ACCOUNT_TOKEN_TYPE: This expected subject token type. Always present.
• GOOGLE_EXTERNAL_ACCOUNT_IMPERSONATED_EMAIL: The service account email. Only present when service account impersonation is used.
• GOOGLE_EXTERNAL_ACCOUNT_OUTPUT_FILE: The output file location from the credential configuration. Only present when specified in the credential configuration.

These environment variables can be used by the executable to avoid hard-coding these values.

Security considerations

The following security practices are highly recommended:

• Access to the script should be restricted as it will be displaying credentials to stdout. This ensures that rogue processes do not gain access to the script.
• The configuration file should not be modifiable. Write access should be restricted to avoid processes modifying the executable command portion.

Given the complexity of using executable-sourced credentials, it is recommended to use the existing supported mechanisms (file-sourced/URL-sourced) for providing 3rd party credentials unless they do not meet your specific requirements.

You can now use the Auth library to call Google Cloud resources from an OIDC or SAML provider.

Workforce Identity Federation

Workforce identity federation lets you use an external identity provider (IdP) to authenticate and authorize a workforce—a group of users, such as employees, partners, and contractors—using IAM, so that the users can access Google Cloud services. Workforce identity federation extends Google Cloud's identity capabilities to support syncless, attribute-based single sign on.

With workforce identity federation, your workforce can access Google Cloud resources using an external identity provider (IdP) that supports OpenID Connect (OIDC) or SAML 2.0 such as Azure Active Directory (Azure AD), Active Directory Federation Services (AD FS), Okta, and others.

Accessing resources using an OIDC or SAML 2.0 identity provider

In order to access Google Cloud resources from an identity provider that supports OpenID Connect (OIDC), the following requirements are needed:

• A workforce identity pool needs to be created.
• An OIDC or SAML 2.0 identity provider needs to be added in the workforce pool.

Follow the detailed instructions on how to configure workforce identity federation.

After configuring an OIDC or SAML 2.0 provider, a credential configuration file needs to be generated. The generated credential configuration file contains non-sensitive metadata to instruct the library on how to retrieve external subject tokens and exchange them for GCP access tokens. The configuration file can be generated by using the gcloud CLI.

The Auth library can retrieve external subject tokens from a local file location (file-sourced credentials), from a local server (URL-sourced credentials) or by calling an executable (executable-sourced credentials).

File-sourced credentials For file-sourced credentials, a background process needs to be continuously refreshing the file location with a new subject token prior to expiration. For tokens with one hour lifetimes, the token needs to be updated in the file every hour. The token can be stored directly as plain text or in JSON format.

To generate a file-sourced OIDC configuration, run the following command:

# Generate an OIDC configuration file for file-sourced credentials.
gcloud iam workforce-pools create-cred-config \
    locations/global/workforcePools/$WORKFORCE_POOL_ID/providers/$PROVIDER_ID \
    --subject-token-type=urn:ietf:params:oauth:token-type:id_token \
    --credential-source-file=$PATH_TO_OIDC_ID_TOKEN \
    --workforce-pool-user-project=$WORKFORCE_POOL_USER_PROJECT \
    # Optional arguments for file types. Default is "text":
    # --credential-source-type "json" \
    # Optional argument for the field that contains the OIDC credential.
    # This is required for json.
    # --credential-source-field-name "id_token" \
    --output-file=/path/to/generated/config.json

Where the following variables need to be substituted:

• $WORKFORCE_POOL_ID: The workforce pool ID.
• $PROVIDER_ID: The provider ID.
• $PATH_TO_OIDC_ID_TOKEN: The file path used to retrieve the OIDC token.
• $WORKFORCE_POOL_USER_PROJECT: The project number associated with the workforce pools user project.

To generate a file-sourced SAML configuration, run the following command:

# Generate a SAML configuration file for file-sourced credentials.
gcloud iam workforce-pools create-cred-config \
    locations/global/workforcePools/$WORKFORCE_POOL_ID/providers/$PROVIDER_ID \
    --credential-source-file=$PATH_TO_SAML_ASSERTION \
    --subject-token-type=urn:ietf:params:oauth:token-type:saml2 \
    --workforce-pool-user-project=$WORKFORCE_POOL_USER_PROJECT \
    --output-file=/path/to/generated/config.json 

Where the following variables need to be substituted:

• $WORKFORCE_POOL_ID: The workforce pool ID.
• $PROVIDER_ID: The provider ID.
• $PATH_TO_SAML_ASSERTION: The file path used to retrieve the base64-encoded SAML assertion.
• $WORKFORCE_POOL_USER_PROJECT: The project number associated with the workforce pools user project.

These commands generate the configuration file in the specified output file.

URL-sourced credentials For URL-sourced credentials, a local server needs to host a GET endpoint to return the OIDC token. The response can be in plain text or JSON. Additional required request headers can also be specified.

To generate a URL-sourced OIDC workforce identity configuration, run the following command:

# Generate an OIDC configuration file for URL-sourced credentials.
gcloud iam workforce-pools create-cred-config \
    locations/global/workforcePools/$WORKFORCE_POOL_ID/providers/$PROVIDER_ID \
    --subject-token-type=urn:ietf:params:oauth:token-type:id_token \
    --credential-source-url=$URL_TO_RETURN_OIDC_ID_TOKEN \
    --credential-source-headers $HEADER_KEY=$HEADER_VALUE \
    --workforce-pool-user-project=$WORKFORCE_POOL_USER_PROJECT \
    --output-file=/path/to/generated/config.json

Where the following variables need to be substituted:

• $WORKFORCE_POOL_ID: The workforce pool ID.
• $PROVIDER_ID: The provider ID.
• $URL_TO_RETURN_OIDC_ID_TOKEN: The URL of the local server endpoint.
• $HEADER_KEY and $HEADER_VALUE: The additional header key/value pairs to pass along the GET request to $URL_TO_GET_OIDC_TOKEN, e.g. Metadata-Flavor=Google.
• $WORKFORCE_POOL_USER_PROJECT: The project number associated with the workforce pools user project.

To generate a URL-sourced SAML configuration, run the following command:

# Generate a SAML configuration file for file-sourced credentials.
gcloud iam workforce-pools create-cred-config \
    locations/global/workforcePools/$WORKFORCE_POOL_ID/providers/$PROVIDER_ID \
    --subject-token-type=urn:ietf:params:oauth:token-type:saml2 \
    --credential-source-url=$URL_TO_GET_SAML_ASSERTION \
    --credential-source-headers $HEADER_KEY=$HEADER_VALUE \
    --workforce-pool-user-project=$WORKFORCE_POOL_USER_PROJECT \
    --output-file=/path/to/generated/config.json 

These commands generate the configuration file in the specified output file.

Where the following variables need to be substituted:

• $WORKFORCE_POOL_ID: The workforce pool ID.
• $PROVIDER_ID: The provider ID.
• $URL_TO_GET_SAML_ASSERTION: The URL of the local server endpoint.
• $HEADER_KEY and $HEADER_VALUE: The additional header key/value pairs to pass along the GET request to $URL_TO_GET_SAML_ASSERTION, e.g. Metadata-Flavor=Google.
• $WORKFORCE_POOL_USER_PROJECT: The project number associated with the workforce pools user project.

Using Executable-sourced workforce credentials with OIDC and SAML

Executable-sourced credentials For executable-sourced credentials, a local executable is used to retrieve the 3rd party token. The executable must handle providing a valid, unexpired OIDC ID token or SAML assertion in JSON format to stdout.

To use executable-sourced credentials, the GOOGLE_EXTERNAL_ACCOUNT_ALLOW_EXECUTABLES environment variable must be set to 1.

To generate an executable-sourced workforce identity configuration, run the following command:

# Generate a configuration file for executable-sourced credentials.
gcloud iam workforce-pools create-cred-config \
    locations/global/workforcePools/