Obscura Server

Obscura Server is a minimalist, secure relay server for the Signal Protocol. It facilitates end-to-end encrypted asynchronous messaging while knowing nothing about the content of the messages.

Features

Zero-Knowledge Architecture: The server stores opaque encrypted blobs. It cannot read message content.
Signal Protocol Support: Uses PreKeys (Identity, Signed, One-Time) to enable X3DH key exchanges.
Asynchronous Delivery: Stores encrypted messages until the recipient comes online to fetch them.
Strict Privacy Limits: Automatic garbage collection of old messages and global inbox limits to prevent metadata buildup.
Container Native: Built with Docker in mind for easy deployment.
Configurable: Fully configurable via command-line flags or environment variables.

Configuration

Obscura Server can be configured using either command-line options or by setting corresponding environment variables. Command-line options take precedence over environment variables.

Option	Description	Environment Variable	Default	Required
`--database-url`	PostgreSQL connection string	`DATABASE_URL`	-	Yes
`--jwt-secret`	Secret key for signing JWTs	`JWT_SECRET`	-	Yes
`--server-host`	Interface to bind the server to	`SERVER_HOST`	`0.0.0.0`	No
`--port`	Port to bind the server to	`PORT`	`3000`	No
`--message-ttl-days`	Days before a message is auto-deleted	`MESSAGE_TTL_DAYS`	`30`	No
`--max-inbox-size`	Max pending messages per user	`MAX_INBOX_SIZE`	`1000`	No
`--message-batch-limit`	Max messages sent per DB fetch loop	`MESSAGE_BATCH_LIMIT`	`50`	No
`--rate-limit-per-second`	API requests allowed per second	`RATE_LIMIT_PER_SECOND`	`10`	No
`--rate-limit-burst`	Max API burst allowance per IP	`RATE_LIMIT_BURST`	`20`	No
`--auth-rate-limit-per-second`	Auth requests allowed per second	`AUTH_RATE_LIMIT_PER_SECOND`	`1`	No
`--auth-rate-limit-burst`	Auth API burst allowance per IP	`AUTH_RATE_LIMIT_BURST`	`3`	No
`--trusted-proxies`	CIDR ranges of trusted proxies	`TRUSTED_PROXIES`	`10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 127.0.0.1/32`	No
`--ws-outbound-buffer-size`	WS outbound channel capacity	`WS_OUTBOUND_BUFFER_SIZE`	`32`	No
`--ws-ack-buffer-size`	WS ACK channel capacity	`WS_ACK_BUFFER_SIZE`	`100`	No
`--ws-ack-batch-size`	WS ACK DB batch size	`WS_ACK_BATCH_SIZE`	`50`	No
`--ws-ack-flush-interval-ms`	WS ACK DB flush interval	`WS_ACK_FLUSH_INTERVAL_MS`	`500`	No

Example

# Using Flags
./obscura-server \
  --database-url postgres://user:pass@localhost/db \
  --jwt-secret my_secret \
  --port 8080

# Using Environment Variables
export DATABASE_URL=postgres://user:pass@localhost/db
export JWT_SECRET=my_secret
./obscura-server

Docker

A Dockerfile is included for easy deployment.

Build and Run

Build the image:
```
docker build -t obscura-server .
```

Run with Docker:

docker run -d \
  -p 3000:3000 \
  -e DATABASE_URL="postgres://user:pass@host.docker.internal:5432/obscura" \
  -e JWT_SECRET="your_secret_key" \
  obscura-server

Docker Compose

A docker-compose.yml is provided for a complete local stack (Postgres + Server):

docker compose up -d

Development

Prerequisites

Rust 1.83+
PostgreSQL 16+
protoc (Protocol Buffers compiler)

Running Locally

Start Postgres:
```
docker compose up -d db
```

Run the server:

export DATABASE_URL=postgres://user:password@localhost/signal_server
export JWT_SECRET=test
cargo run

Migrations are applied automatically on startup.

Testing

cargo test

API Documentation

REST API: Defined in specs/001-signal-server/contracts/openapi.yaml.
WebSocket: Available at /v1/gateway. Expects Protobuf messages defined in proto/obscura.proto.

License

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.

obscura-server 0.2.3