Mailgun Relayery

Mailgun Relayery is a tool for relaying messages with different API keys through the single-key MailGun API.

The problem: MailGun gives out a single API key to each account. For entities dealing with multiple clients or applications, giving out their API key to each of them constitutes a security violation.

The solution: Mailgun Relayery acts as a middle layer between message senders and the MailGun API. Senders are issued descriptor strings (analogous to usernames) and authentication tokens (analogous to passwords), which are used to authenticate their requests to the middle layer and to relay their messages to MailGun.

The tool stores authentication data (tokens) and channeling data (mailing fields like recipients, cc, bcc, etc.) in a local database, guaranteeing persistency. Two servers have access to the database:

the Control server (with read-write access to the database) manages authentication data and mailing channels; this server should only be accessed via secure connection and managed by a trusted party.
the Relay server (with read-only access to the database) receives and authenticates HTTP requests to relay messages to the MailGun API; this server is open to the whole Internet.

All communication with the servers takes place via HTTP following the relay server API and the control server API.

An example Python script is available for a quick start.

Usage

Compilation

If you're running a linux x64 architecture, you can directly use the binaries available in the Releases page.

Run the release script to compile and release the two server binaries to a target directory:
```
./release.py --release_dir your/release/directory
```
Run the database initialization binary to create an empty channel database in a target directory:
```
./your/release/directory/mailgun-relayery-init -database_dir /your/database/directory
```

Running the servers

Run the Control Server:

your/release/directory/bin/mailgun-relay-controlery -database_dir your/database/directory

Run the Relay Server:

your/release/directory/bin/mailgun-relayery \
   -database_dir your/database/directory \
   -api_key_path path/to/mailgun/api/key.txt

Sending requests

Use the Control Server API to create a mailing channel and authorization token:

curl -i \
    -X PUT \
    -H "Accept: application/json" \
    -H "Content-Type: application/json" \
    --data '{
        "domain": "marketing.domainname.com",
        "descriptor": "some-channel",
        "token": "oqiwdJKNsdK",
        "sender": {
          "email": "your-name@company.com",
          "name":"Some Sender"
        },
        "recipients":[
          {
            "email": "your-client@client.com",
            "name": "Recipient"
          }
        ],
        "cc": [],
        "bcc": [],
        "min_period":0.1,
        "max_size":10000000
      }' \
  "localhost:8300/api/channel"

Use the Relay Server API to relay a message:

curl -i \
    -X POST \
    -H "Accept: application/json" \
    -H "Content-Type: application/json" \
    -H "X-Descriptor: some-channel" \
    -H "X-Token: oqiwdJKNsdK" \
    --data '{
      "message": "hello there",
      "subject": "a message from your friend"
    }' \
    "localhost:8200/api/message

Development

Please refer to CONTRIBUTING.md.

Versioning

We follow Semantic Versioning. The version X.Y.Z indicates:

X is the major version (backward-incompatible),
Y is the minor version (backward-compatible), and
Z is the patch version (backward-compatible bug fix).