POM file detail:

      <dependency>
    <groupId>com.google.auth</groupId>
    <artifactId>google-auth-library-appengine</artifactId>
</dependency>

1.2.4.RELEASE

Libs included in jar:
Line 643: Step #0: [INFO] Downloading from central: https://repo.maven.apache.org/maven2/com/google/auth/google-auth-library-oauth2-http/0.21.1/google-auth-library-oauth2-http-0.21.1.pom
Line 643: Step #0: [INFO] Downloading from central: https://repo.maven.apache.org/maven2/com/google/auth/google-auth-library-oauth2-http/0.21.1/google-auth-library-oauth2-http-0.21.1.pom

Environment details

• OS: Debian
• Java version: 11
• google-auth-library-java version(s): 0.21.1

Steps to reproduce

• upload a file in GCS bucket.
• Try to download it using code given below.
  Stacktrace

com.google.auth.ServiceAccountSigner$SigningException: Failed to sign the provided bytes
at com.google.auth.oauth2.IamUtils.sign(IamUtils.java:87)
at com.google.auth.oauth2.ComputeEngineCredentials.sign(ComputeEngineCredentials.java:361)
at com.google.cloud.storage.StorageImpl.signUrl(StorageImpl.java:772)
at com.google.cloud.storage.Blob.signUrl(Blob.java:822)

Caused by: java.io.IOException: Error code 403 trying to sign provided bytes: The caller does not have permission
at com.google.auth.oauth2.IamUtils.getSignature(IamUtils.java:125)
at com.google.auth.oauth2.IamUtils.sign(IamUtils.java:84)
... 69 more

Code snippet

// [START auth_cloud_explicit_compute_engine]
public Storage authCompute() throws IOException {
// Explicitly request service account credentials from the compute engine
// instance.
//GoogleCredentials credentials = ComputeEngineCredentials.create();
GoogleCredentials credentials = ComputeEngineCredentials.getApplicationDefault();
Storage storage = StorageOptions.newBuilder().setCredentials(credentials).build().getService();

    System.out.println("Buckets:");
    Page<Bucket> buckets = storage.list();
    for (Bucket bucket : buckets.iterateAll()) {
        System.out.println(bucket.toString());
    }
    return storage;
}
// [END auth_cloud_explicit_compute_engine]
Storage storage = authUtil.authCompute();
Blob blob = storage.get(BlobId.of(bucketName, objectName));
return blob.signUrl(urlExpirationTime, TimeUnit.MILLISECONDS);

My application is deployed on GKE. From there we are trying to download/get signed url a file i.e. stored in GCS.