# HTTP/S API supporting HMAC API keys

So all the other containers are in the Docker Swarm and we want to expose a real HTTP/S interface to clients outside of the Swarm, that makes sense.  Clients have to get an API key first.

## Build

### Create your API key and put it in keys.properties

Let's produce a 256-bits key that we'll convert in an hex string to store and use with openssl hmac feature.

Alpine (Busybox):

```shell
dd if=/dev/urandom bs=32 count=1 2> /dev/null | xxd -pc 32
```

Linux:

```shell
dd if=/dev/urandom bs=32 count=1 2> /dev/null | xxd -ps -c 32
```

Put the key in keys.properties and keep it for the client.  This is a secret key.  keys.properties looks like this:

```property
#group.id=hex(key)
watcher.001=2df1eeea370eacdc5cf7e96c2d82140d1568079a5d4d87006ec8718a98883b36
watcher.002=50c5e483b80964595508f214229b014aa6c013594d57d38bcb841093a39f1d83
spender.001=b9b8d527a1a27af2ad1697db3521f883760c342fc386dbc42c4efbb1a4d5e0af
spender.002=bb0458b705e774c0c9622efaccfe573aa30c82f62386d9435f04e9727cdc26fd
admin.001=6c009201b123e8c24c6b74590de28c0c96f3287e88cac9460a2173a53d73fb87
admin.002=19e121b698014fac638f772c4ff5775a738856bf6cbdef0dc88971059c69da4b
```

You can have multiple keys, but be aware that this container has **not** been built to support thousands of API keys!  **Cyphernode should be used locally**, not publicly as a service.

## SSL

If you already have your certificates and keystores infra, you already know what to do and your can skip this section.  Put your files in the bound volume (~/cyphernode-ssl/ see volume path in docker-compose.yml).

If not, you can create your keys and self-signed certificates.

```shell
mkdir -p ~/cyphernode-ssl/certs ~/cyphernode-ssl/private
openssl req -subj '/CN=localhost' -x509 -newkey rsa:4096 -nodes -keyout ~/cyphernode-ssl/private/key.pem -out ~/cyphernode-ssl/certs/cert.pem -days 365
```

If you don't want to use HTTPS, just copy default.conf instead of default-ssl.conf in Dockerfile.

**Nota bene**: If you self-sign the certificate, you have to trust the certificate on the client side by adding it to the Trusted Root Certification Authorities or whatever your client needs.

### Build and run docker image

```shell
docker build -t authapi .
```

If you are using it independantly from the Docker stack (docker-compose.yml), you can run it like that:

```shell
docker run -d --rm --name authapi -p 80:80 -p 443:443 --network cyphernodenet -v "~/cyphernode-ssl/certs:/etc/ssl/certs" -v "~/cyphernode-ssl/private:/etc/ssl/private" authapi
```

## FYI: Bearer token

Following JWT (JSON Web Tokens) standard, we build a bearer token that will be in the request header and signed with the secret key.  We need this in the request header:

```shell
Authorization: Bearer <token>
```

...where token is:

```shell
token = hhh.ppp.sss
```

...where hhh is the header in base64, ppp is the payload in base64 and sss is the signature.  Here are the expected formats and contents:

```shell
header = {"alg":"HS256","typ":"JWT"}
header64 = base64(header) = eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9Cg==
```

```shell
payload = {"id":"001","exp":1538528077}
payload64 = base64(payload) = eyJpZCI6IjAwMSIsImV4cCI6MTUzODUyODA3N30K
```

The "id" property is the client id and the "exp" property should be current epoch time + 10 seconds, like:

```shell
$((`date +"%s"`+10))
```

...so that the request will be expired in 10 seconds.  That should take care of most Replay attacks if any.  You should run nginx with TLS so that the replay attack can't be possible.

```shell
signature = hmacsha256(header64.payload64, key)
```

```shell
token = header64 + "." + payload64 + "." + signature
```

### cURL example of an API invocation

Instruction should be in the form:

```shell
curl -v -H "Authorization: Bearer hhh.ppp.sss" localhost
```

10 seconds request expiration:

```shell
id="001";h64=$(echo "{\"alg\":\"HS256\",\"typ\":\"JWT\"}" | base64);p64=$(echo "{\"id\":\"$id\",\"exp\":$((`date +"%s"`+10))}" | base64);k="2df1eeea370eacdc5cf7e96c2d82140d1568079a5d4d87006ec8718a98883b36";s=$(echo "$h64.$p64" | openssl dgst -hmac "$k" -sha256 -r | cut -sd ' ' -f1);token="$h64.$p64.$s";curl -v -H "Authorization: Bearer $token" -k https://localhost/getbestblockhash
```

60 seconds request expiration:

```shell
id="001";h64=$(echo "{\"alg\":\"HS256\",\"typ\":\"JWT\"}" | base64);p64=$(echo "{\"id\":\"$id\",\"exp\":$((`date +"%s"`+60))}" | base64);k="2df1eeea370eacdc5cf7e96c2d82140d1568079a5d4d87006ec8718a98883b36";s=$(echo "$h64.$p64" | openssl dgst -hmac "$k" -sha256 -r | cut -sd ' ' -f1);token="$h64.$p64.$s";curl -v -H "Authorization: Bearer $token" -k https://localhost/getbestblockhash
```

## Technicalities

```shell
h64=$(echo "{\"alg\":\"HS256\",\"typ\":\"JWT\"}" | base64)
p64=$(echo "{\"id\":\"001\",\"exp\":$((`date +"%s"`+10))}" | base64)
k="2df1eeea370eacdc5cf7e96c2d82140d1568079a5d4d87006ec8718a98883b36"
s=$(echo "$h64.$p64" | openssl dgst -hmac "$k" -sha256 -r | cut -sd ' ' -f1)
token="$h64.$p64.$s"
```