spasteg

A secure, self-hostable "burn after reading" paste service with ephemeral storage written in Gleam.

Features

Deletes pastes after they are viewed
Data is stored only in memory
No user accounts needed
Easy to run yourself
Fast and reliable
Written in Gleam (type-safe)

Configuration

SECRET_KEY_BASE (Required for Production)

The application uses a secret key base for signing cookies and security tokens.

You must set this for production deployments to ensure security and session persistence across restarts.

# Generate a secure key (48 bytes of random data)
export SECRET_KEY_BASE=$(openssl rand -base64 48)

# Or set it manually
export SECRET_KEY_BASE="your-secret-key-here"

⚠️ Warning: If not set, a temporary key will be generated on each startup. This:

Invalidates all existing user sessions/cookies after restart
Reduces security (new key generated each time)
Generates a warning in the logs

For development, you can use:

SECRET_KEY_BASE=dev gleam run

Quick Start

# Clone and build
git clone https://git.kharec.info/Kharec/spasteg.git
cd spasteg
gleam run

The server starts on http://localhost:3000.

Usage

Visit http://localhost:3000
Enter your text in the form
Click "Create Paste"
Share the generated URL
The paste auto-destructs after first access

Note: the creator cannot see their post with the copied link (except in private browsing) - it would be burned immediately.

Architecture

Gleam: Type-safe language built upon the BEAM
Web: Wisp framework + Mist HTTP server
Frontend: Lustre for HTML rendering
Storage: In-memory only (no persistence)
Security: AES-256-GCM client-side encryption, CSRF tokens, rate limiting, security headers

Security Notes

Pastes are client-side encrypted (AES-256-GCM) before being sent to server
Server never sees the decryption key (stored in URL fragment after #)
Data is stored encrypted in server memory only
Data is never written to disk
All data is lost on server restart
CSRF protection via double-submit cookie pattern
Rate limiting: 10 requests per minute per IP
Security headers: CSP, X-Frame-Options, X-Content-Type-Options, Referrer-Policy
10MB maximum paste size limit
Intended for ephemeral sharing only — do not store sensitive data

License

This project is licensed under the GNU General Public License v3.0 or later (GPLv3+). See the LICENSE file for details.