[java-storage] CRC32C validation is skipped on all normal HTTP downloads #14773

Issue Details

CRC32C validation is effectively disabled for ALL normal HTTP downloads through reader(), readAllBytes(), and downloadTo(). Damaged data can be returned without a checksum error.

GCS sends x-goog-stored-content-encoding and x-goog-stored-content-length to describe the stored file. The client treats either header as evidence that GCS changed the file before sending it, so it skips validation even when the bytes are unchanged.

Environment

• OS: Ubuntu 24.04
• Java: OpenJDK 21 (Ubuntu)
• Service: Google Cloud Storage, HTTP transport

Dependencies

com.google.cloud:google-cloud-storage:2.75.0

Reproducer

Set a breakpoint in HttpStorageRpcHasherHelper.shouldValidate() and run this download of a public Landsat file. No credentials are needed.

import com.google.cloud.NoCredentials;
import com.google.cloud.storage.Storage;
import com.google.cloud.storage.StorageOptions;

public class LandsatRepro {
  public static void main(String[] args) throws Exception {
    String scene = "LC08_L1GT_044034_20130330_20170310_01_T2";
    String object = "LC08/01/044/034/" + scene + "/" + scene + "_MTL.txt";

    try (Storage storage = StorageOptions.http()
        .setProjectId("landsat-crc32c-repro")
        .setCredentials(NoCredentials.getInstance())
        .build()
        .getService()) {
      byte[] data = storage.readAllBytes("gcp-public-data-landsat", object);
      System.out.println("Downloaded " + data.length + " bytes");
    }
  }
}

• Expected: shouldValidate() returns true, and the client checks the downloaded bytes against GCS's checksum.
• Actual: It returns false, and the download completes without checking the checksum.

Logs and Stack Trace

GCS returns HTTP 200 with:

Content-Length: 8454
x-goog-stored-content-length: 8454
x-goog-stored-content-encoding: identity
x-goog-hash: crc32c=TeBDMA==,md5=ziZNd8uikTtDCkBTgS5Riw==

There is no Content-Encoding header. The program prints Downloaded 8454 bytes. No exception is thrown.

The public file is intact; this example shows the skipped check. In separate tests that changed one downloaded byte, the client accepted the damaged data without an error.

Proposed fix: #14768