This repo allows exposing a Ethereum JSON-RPC server to remote hosts using nginx as a reverse proxy. For security purpose, an Ethereum client (geth, parity, ...) exposes the JSON-RPC service only to localhost interface. In some cases (permisionned chain by example), it can be interesting to expose JSON-RPC to remote hosts but with limited access.

This solution is to use a LUA script, used with nginx-lua-module to control access to the upstream Ethereum client. You can blacklist or whitelist certain JSON-RPC methods (for example, authorize only JSON-RPC requests to eth_sendRawTransaction to allow remote hosts to send transactions to the client, without allowing them to read states in the chain).

nginx has some interesting characteristics as a reverse proxy on top of Ethereum JSON-RPC service:

• Can expose the JSON-RPC service through a TLS channel
• Can load balance between multiple JSON-RPC backends
• Can forward HTTP incoming traffic to the IPC interface of Ethereum client
• Can plug standard authentication on top of the JSON-RPC interface (basic authentication, TLS mutual authentication, ...)

The script eth-jsonrpc-access.lua must be put in your nginx, to be used from access_by_lua_file directive. In order to have a fully functional nginx proxy, you have to install:

• lua-nginx-module, see the setup here.
• cjson lua package installed, see here

Or you can use an adapt the provided Docker image (see Docker image section).

The lua script must be used in a location nginx using the access_by_lua_file directive.

You have to set one of jsonrpc_whitelist or jsonrpc_blacklist nginx variable to restrict the list of JSON-RPC methods available for this location, separated by commas:

location / {
  set $jsonrpc_whitelist 'eth_getTransactionByHash,eth_getTransactionReceipt,eth_sendRawTransaction';
  access_by_lua_file 'eth-jsonrpc-access.lua';
  proxy_pass http://localhost:8545;
}

With the configuration above, only eth_getTransactionByHash, eth_getTransactionReceipt, eth_sendRawTransaction calls will be fowarded to JSON-RPC interface at http://localhost:8545, other requests will be rejected with HTTP 403 status.

You can find a full nginx.conf example file in the repo.

A ready to use image is published to Docker Hub.

Pull the image:
docker pull antoine/ethereum-nginx-proxy:latest

And run a container with your custom nginx.conf:
docker run -p 8080:8080 -v /my/nginx.conf:/etc/nginx.conf antoine/ethereum-nginx-proxy:latest

This image is based on Nginx 1.11.7, Lua Nginx module 0.10.7 and Lua CJSON 2.1.0.