Native Root Certificate Support in Nativelink

Open source thrives on community contributions, and today’s story is a perfect example of why. External engineer Sam Eskandar identified a pain point in Nativelink's TLS configuration and delivered a clean solution that eliminates deployment friction for teams using managed certificates.

Problem: Manual Certificate Management

Before this change, connecting to gRPC endpoints using TLS required specifying ClientTlsConfig like this:

{
  ca_file: "path/to/ca.pem",
  cert_file: "path/to/client.pem",
  key_file: "path/to/client-key.pem"
}

Teams had to distribute CA certificates, client certificates, and key files across workers - creating friction for cloud deployments and potential security concerns when secrets need to be managed manually.

Solution: Native Root Certificate Support

The new implementation adds a use_native_roots option that leverages the system's native root certificate store, eliminating manual certificate file management for most deployment scenarios.

The core change is:

if config.use_native_roots == Some(true) {
    if config.ca_file.is_some() {
        warn!("Native root certificates are being used, all certificate files will be ignored");
    }
    return Ok(Some(
        tonic::transport::ClientTlsConfig::new().with_native_roots(),
    ));
}

This implementation provides three distinct behaviors:

• Native roots enabled: Use system native root certificates, ignore any provided certificate files
• Manual certificate path: Use existing manual certificate configuration
• Clear validation: Warn users when configurations conflict

Configuration Examples

Here are the main ways to configure TLS in Nativelink. For complete configuration options, see the configuration reference.

Native Root Certificates

For the majority of modern deployments, you can now enable native roots with one parameter:

{
  "tls_config": {
    "use_native_roots": true
  }
}

This configuration automatically trusts certificates signed by any certificate authority in your system’s trust store - perfect for cloud environments with managed certificates.

Manual Certificate Path

Since use_native_roots defaults to false, you can still use the previous configuration:

{
  "tls_config": {
    "ca_file": "/path/to/ca.pem",
    "cert_file": "/path/to/client.pem",
    "key_file": "/path/to/client-key.pem"
  }
}

gRPC Store and Local Worker Configuration

The tls_config field can be used in gRPC store endpoints:

"stores": [
  {
    "grpc": {
      "endpoints": [
        {
          "address": "grpcs://example.com:443",
          "tls_config": {
            "use_native_roots": true
          }
        }
      ],
      "instance_name": "main",
      "store_type": "cas"
    },
    "name": "CAS_STORE"
  }
]

And in worker API endpoints:

"workers": [{
  "local": {
    "worker_api_endpoint": {
      "uri": "grpcs://127.0.0.1:50061",
      "tls_config": {
        "use_native_roots": true
      }
    },
    // ...
  }
}]

Community Contributions

The PR discussion shows how the review process strengthened the implementation. The contributor included comprehensive unit tests covering all configuration scenarios. Reviewers suggested UX improvements like warning users when certificate files are ignored, identified documentation needs, and planned future enhancements. One reviewer opened a follow-up PR to extend native roots to S3 stores.

This collaborative refinement process caught edge cases, improved error handling, and identified future improvements - resulting in a more robust implementation than any single contributor could have produced alone.

Looking forward

With native root certificate support, Nativelink becomes more accessible to teams across diverse infrastructure environments. Whether you’re running containerized workloads in Kubernetes, deploying on traditional virtual machines with corporate PKI, or prototyping locally, TLS configuration no longer presents a barrier to adoption.

This is the power of open source in action - community-driven improvements that make technology more accessible, secure, and flexible for everyone building the future. We’re grateful for contributions like this that strengthen Nativelink’s position as the premier open source remote execution platform.

---

Interested in contributing? Check out our GitHub repository.