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Gateway Communication

Overview

This document describes how the CLI resolves a gateway and communicates with it once the endpoint already exists. The gateway exposes gRPC and HTTP services on a single multiplexed port, and the CLI chooses one of three connection modes: direct mTLS, edge-authenticated WebSocket tunnel, or plaintext HTTP/2 behind a trusted proxy.

Connection Flow

Gateway resolution

When any CLI command needs to talk to the gateway, it resolves the target through a priority chain (crates/openshell-cli/src/main.rs -- resolve_gateway()):

  1. --gateway-endpoint <URL> flag (direct URL, reusing stored metadata when the gateway is known).
  2. --cluster <NAME> / -g <NAME> flag.
  3. OPENSHELL_GATEWAY environment variable.
  4. Active gateway from ~/.config/openshell/active_gateway.

Resolution loads ClusterMetadata from disk to get the gateway_endpoint URL and auth_mode. When --gateway-endpoint is used, the CLI still tries to match the URL to stored metadata so edge auth tokens and TLS bundles continue to resolve by cluster name.

Connection modes

graph TD
    CLI["CLI Command"]
    RESOLVE["Resolve Gateway"]
    MODE{"auth_mode?"}

    MTLS["mTLS Channel"]
    EDGE["Edge Tunnel"]
    PLAIN["Plaintext Channel"]

    GW["Gateway (gRPC + HTTP)"]

    CLI --> RESOLVE
    RESOLVE --> MODE

    MODE -->|"null / mtls"| MTLS
    MODE -->|"cloudflare_jwt"| EDGE
    MODE -->|"plaintext endpoint"| PLAIN

    MTLS -->|"TLS + client cert"| GW
    EDGE -->|"WSS tunnel + JWT"| GW
    PLAIN -->|"HTTP/2 plaintext"| GW
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mTLS connection (default)

File: crates/openshell-cli/src/tls.rs -- build_channel()

The default mode for self-deployed gateways. The CLI loads three PEM files from ~/.config/openshell/clusters/<name>/mtls/:

File Purpose
ca.crt Cluster CA certificate -- verifies the gateway's server cert
tls.crt Client certificate -- proves the CLI's identity to the gateway
tls.key Client private key

These are used to build a tonic::transport::ClientTlsConfig, which configures a tonic::transport::Channel for gRPC communication over HTTP/2 with mTLS.

sequenceDiagram
    participant CLI as CLI
    participant GW as Gateway

    CLI->>CLI: Load ca.crt, tls.crt, tls.key
    CLI->>GW: TCP connect to gateway_endpoint
    CLI->>GW: TLS handshake (present client cert)
    GW->>GW: Verify client cert against CA
    GW-->>CLI: TLS established (HTTP/2 via ALPN)
    CLI->>GW: gRPC requests (OpenShell / Inference service)
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Edge-authenticated connection

Files: crates/openshell-cli/src/edge_tunnel.rs, crates/openshell-cli/src/auth.rs

For gateways behind an edge proxy (e.g., Cloudflare Access), the CLI routes traffic through a local WebSocket tunnel proxy:

  1. start_tunnel_proxy() binds an ephemeral local TCP port.
  2. Opens a WebSocket connection (wss://<gateway>/_ws_tunnel) to the edge with the stored bearer token in headers.
  3. The gateway's ws_tunnel.rs handler upgrades the WebSocket and bridges it to an in-memory MultiplexService instance.
  4. The gRPC channel connects to http://127.0.0.1:<local_port> (plaintext HTTP/2 over the tunnel).

Authentication uses a browser-based flow: gateway add opens the user's browser to the gateway's /auth/connect endpoint, which reads the CF_Authorization cookie and relays it back to a localhost callback server. The token is stored at ~/.config/openshell/clusters/<name>/edge_token.

Plaintext connection

When the gateway is deployed with --plaintext, TLS is disabled entirely. The CLI connects over plain HTTP/2. This mode is intended for gateways behind a trusted reverse proxy or tunnel that handles TLS termination.

File System Layout

All connection artifacts are stored under $XDG_CONFIG_HOME/openshell/ (default ~/.config/openshell/):

openshell/
  active_cluster                          # plain text: active cluster name
  clusters/
    <name>_metadata.json                  # ClusterMetadata JSON
    <name>/
      mtls/                               # mTLS bundle (when TLS enabled)
        ca.crt                            # cluster CA certificate
        tls.crt                           # client certificate
        tls.key                           # client private key
      edge_token                          # Edge auth JWT (when auth_mode=cloudflare_jwt)

Registering an Edge-Authenticated Gateway

For gateways that are already deployed behind an edge proxy (e.g., Cloudflare Access), deployment is not needed -- only registration.

File: crates/openshell-cli/src/run.rs -- gateway_add()

sequenceDiagram
    participant U as User
    participant CLI as openshell-cli
    participant Browser as Browser
    participant Edge as Edge Proxy
    participant GW as Gateway

    U->>CLI: openshell gateway add https://gw.example.com
    CLI->>CLI: Store metadata (auth_mode: cloudflare_jwt)
    CLI->>Browser: Open https://gw.example.com/auth/connect
    Browser->>Edge: Edge proxy login
    Edge-->>Browser: CF_Authorization cookie
    Browser->>GW: GET /auth/connect (with cookie)
    GW-->>Browser: Relay page (extracts token, POSTs to localhost)
    Browser->>CLI: POST token to localhost callback
    CLI->>CLI: Store edge_token
    CLI->>CLI: save_active_cluster
    CLI-->>U: Gateway added and set as active
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