Networking

Nitro enclaves are stripped down virtual machines that do not have a networking interface, except for localhost. The only conduit is a virtual socket (vsock) that connects the enclave to the host. Enclaver uses this vsock to proxy networking traffic to and from the enclave.

Egress proxy

HTTP Tunnel

At this time, Enclaver only supports HTTP Tunnel. While the tunnel uses the HTTP CONNECT verb to initiate a connection, once a connection is established, any TCP traffic can be proxied through it.

The application needs to have support for the HTTP tunnel (proxy), however, many high level HTTP libraries, such as Python’s “requests” have this capability built-in. For others, there is often an easy plugin/middleware that can be installed to gain this functionality.

For libraries that have support out of the box, they often automatically detect the presence of http_proxy and https_proxy environment variables to automatically establish a tunnel for requests. Enclaver sets http_proxy, HTTP_PROXY, https_proxy, HTTPS_PROXY, no_proxy, NO_PROXY environment variables if the egress proxy is enabled.

Configuration

To enable the egress proxy (HTTP tunnel), set the egress object in the manifest file and include hostnames and IPs that should be allowed for the application to connect to. The configuration supports both regular (*) and greedy (**) wildcards. The greedy versions match multiple components of a hostname/IP. For example:

egress:
  allow:
    - "kms.*.amazonaws.com"
    - "s3.amazonaws.com"
    - "**.mycorp.com"

  deny:
    - "auth.mycorp.com"

Ingress proxy

The Enclaver supports a TCP ingress proxy which proxies from the host to the localhost inside the enclave. To accept connections on a port 3000, the application should bind to 127.0.0.1:3000 and then instruct the Encalver to start the proxy in the manifest file:

ingress:
  - listen_port: 3000

This will also cause the “outer” proxy to listen on 0.0.0.0:3000 on the host. It is recommended to use TLS to secure the communication flowing through the host.