Authenticate with JWTs

The BigQuery API accepts JSON Web Tokens (JWTs) to authenticate requests.

As a best practice, you should use Application Default Credentials (ADC) to authenticate to BigQuery. If you can't use ADC and you're using a service account for authentication, then you can use a signed JWT instead. JWTs let you make an API call without a network request to Google's authorization server.

You can use JWTs to authenticate in the following ways:

Scope and Audience

Use scopes with service account when possible. If not possible, you can use an audience claim. For the BigQuery APIs, set the audience value to https://bigquery.googleapis.com/.

Create JWTs with client libraries

For service account keys created in Trusted Cloud console or by using the gcloud CLI, use a client library that provides JWT signing. The following list provides some appropriate options for popular programming languages:

Java example

The following example uses the BigQuery client library for Java to create and sign a JWT. The default scope for BigQuery API is set to https://www.googleapis.com/auth/bigquery in the client library.

import com.google.auth.oauth2.ServiceAccountCredentials;
import com.google.cloud.bigquery.BigQuery;
import com.google.cloud.bigquery.BigQueryOptions;
import com.google.common.collect.ImmutableList;

import java.io.FileInputStream;
import java.io.IOException;
import java.net.URI;

public class Example {
    public static void main(String... args) throws IOException {
        String projectId = "myproject";
        // Load JSON file that contains service account keys and create ServiceAccountCredentials object.
        String credentialsPath = "/path/to/key.json";
        ServiceAccountCredentials credentials = null;
        try (FileInputStream is = new FileInputStream(credentialsPath)) {
          credentials =  ServiceAccountCredentials.fromStream(is);
          // The default scope for BigQuery is used. 
          // Alternatively, use `.setScopes()` to set custom scopes.
          credentials = credentials.toBuilder()
              .setUseJwtAccessWithScope(true)
              .build();
        }
        // Instantiate BigQuery client with the credentials object.
        BigQuery bigquery =
                BigQueryOptions.newBuilder().setCredentials(credentials).build().getService();
        // Use the client to list BigQuery datasets.
        System.out.println("Datasets:");
        bigquery
            .listDatasets(projectId)
            .iterateAll()
            .forEach(dataset -> System.out.printf("%s%n", dataset.getDatasetId().getDataset()));
    }
}

Create JWTs with REST or the gcloud CLI

For system-managed service accounts, you must manually assemble the JWT, then use the REST method projects.serviceAccounts.signJwt or the Google Cloud CLI command gcloud beta iam service-accounts sign-jwt to sign the JWT. To use either of these approaches, you must be a member of the Service Account Token Creator Identity and Access Management role.

gcloud CLI example

The following example shows a bash script that assembles a JWT and then uses the gcloud beta iam service-accounts sign-jwt command to sign it.

#!/bin/bash

SA_EMAIL_ADDRESS="myserviceaccount@myproject.s3ns-system.iam.gserviceaccount.com"

TMP_DIR=$(mktemp -d /tmp/sa_signed_jwt.XXXXX)
trap "rm -rf ${TMP_DIR}" EXIT
JWT_FILE="${TMP_DIR}/jwt-claim-set.json"
SIGNED_JWT_FILE="${TMP_DIR}/output.jwt"

IAT=$(date '+%s')
EXP=$((IAT+3600))

cat <<EOF > $JWT_FILE
{
  "aud": "https://bigquery.googleapis.com/",
  "iat": $IAT,
  "exp": $EXP,
  "iss": "$SA_EMAIL_ADDRESS",
  "sub": "$SA_EMAIL_ADDRESS"
}
EOF

gcloud beta iam service-accounts sign-jwt --iam-account $SA_EMAIL_ADDRESS $JWT_FILE $SIGNED_JWT_FILE

echo "Datasets:"
curl -L -H "Authorization: Bearer $(cat $SIGNED_JWT_FILE)" \
-X GET \
"https://bigquery.googleapis.com/bigquery/v2/projects/myproject/datasets?alt=json"

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