gRPC ALTS Example
==================

This example suite shows secure communication between a Hello World 
client and a Hello World server authenticated by Google's Application Layer 
Transport Security (ALTS). For more information about ALTS itself, see 
[ALTS Whiltepaper](https://cloud.google.com/security/encryption-in-transit/application-layer-transport-security) or [grpc.io tutorial](https://grpc.io/docs/languages/java/alts/).

In the gRPC-java context, for both the ALTS client and the ALTS server, a 
`gRPC-client`-backed handshaker is installed in their channel protocol 
negotiator. Once a connection is established between the ALTS Client and the 
ALTS Server, the protocol negotiators will trigger the ALTS handshaking process, 
which fires multiple rounds of gRPC communication between multiple parties, 
including the ALTS client, the ALTS server and a pre-deployed handshaker 
server. At the end, they will reach a shared secret to be used to encrypt the 
following RPC calls.

The example runs successfully in a GCP environment 
out-of-the-box, and can be further configured to run in any environments
with a pre-deployed handshaker service.


### Build the example

To build the example,

1. **[Install gRPC Java library SNAPSHOT locally, including code generation plugin](../../COMPILING.md) (Only need this step for non-released versions, e.g. master HEAD).**

2. Run in this directory:
```
$ ../gradlew installDist
```

This creates the scripts `hello-world-alts-server`, `hello-world-alts-client`,
in the
`build/install/example-atls/bin/` directory that run the example.

### Run the example in a GCP environment
ALTS handshake protocol negotiation requires a separate handshaker service. It is
available in the GCP environment, so we can run the application directly:

```bash
# Run the server:
./build/install/example-alts/bin/hello-world-alts-server

```

In another terminal run the client

```
./build/install/example-alts/bin/hello-world-alts-client
```

That's it!

### Test the example in a non-GCP environment

To run the example in a non-GCP environment, you should first deploy a 
[handshaker service](https://github.com/grpc/grpc/blob/7e367da22a137e2e7caeae8342c239a91434ba50/src/proto/grpc/gcp/handshaker.proto#L224-L234) 
and know its name. You should configure both the [ALTS client](https://github.com/grpc/grpc-java/blob/master/alts/src/main/java/io/grpc/alts/AltsChannelBuilder.java#L63-L76) 
and [ALTS server](https://github.com/grpc/grpc-java/blob/master/alts/src/main/java/io/grpc/alts/AltsServerCredentials.java#L55-L72)
to use the known handshaker server for testing. See [example](https://github.com/grpc/grpc-java/blob/master/interop-testing/src/test/java/io/grpc/testing/integration/AltsHandshakerTest.java#L45).