DDC (Direct Download Client)

Self-hosted direct download client that fetches files onto the server, extracts archives, and moves the results into media folders.

Stack

• Backend: Go standard library only (no third-party dependencies), single static binary
• Frontend: plain HTML, CSS, and JavaScript modules embedded in the binary
• Container: distroless static image, non-root, read-only root filesystem

Project Layout

Path	Purpose
main.go	Startup and graceful shutdown
internal/config	Environment configuration and library root parsing
internal/preferences	Settings editable from the web page, saved to .settings.json
internal/libraries	Discovers and validates first level library folders
internal/auth	Sessions, credential check, login rate limiting
internal/guard	URL validation and SSRF-safe HTTP client
internal/fetch	Resumable multi-connection downloads with progress, size and stall limits
internal/history	Move history saved to .history.json
internal/extract	Zip and tar extraction with Zip Slip and bomb protection
internal/files	Safe path resolution, file tree, cross-device moves
internal/diskspace	Free space checks
internal/jobs	Download job lifecycle, pause and resume, state saved to .job.json per download
internal/server	HTTP routes, middleware, handlers
web/static	Single page frontend
deploy/nginx	Reverse proxy example

Destinations

Every first level folder inside these roots is a move destination:

• /media/blob/TeaNet/Plex
• /media/blob/ChaiNet/Plex

Security

• Session login with HttpOnly, Secure, SameSite=Strict cookie
• Login lockout after 5 failed attempts per client for 15 minutes
• Same-origin check and JSON-only bodies on state changing requests
• SSRF protection: http/https only, allowed port list, every resolved IP checked at connect time (blocks loopback, private, link-local, CGNAT, metadata, ULA, NAT64, multicast), redirects revalidated, proxies ignored
• Zip Slip protection: absolute paths and .. entries rejected, symlinks, hardlinks and devices skipped
• Extraction limited by free disk space and entry count
• Move targets restricted to first level folders of the destination roots (hidden folders and symlinks excluded), subfolders validated component by component, existing files never overwritten
• Disk space checked before download, during download, before extraction, and before cross-device copies
• Strict Content-Security-Policy, no inline scripts, all untrusted names rendered as text

Supported Archives

.zip, .tar, .tar.gz, .tgz, .tar.bz2, .tbz2, .tbz

Configuration

Variable	Default	Description
AUTH_USERNAME	required	Login username
AUTH_PASSWORD	required	Login password, minimum 12 characters
COOKIE_SECURE	true	Set false only for plain HTTP testing
SESSION_TTL_HOURS	12	Session lifetime
TRUST_PROXY_HEADERS	false	Use X-Real-IP for login rate limiting (enable behind nginx)
LISTEN_ADDR	:8080	Listen address inside the container
DOWNLOAD_DIR	/data/downloads	Temporary download directory
MIN_FREE_GB	10	Initial value: free space that must always remain
MAX_CONCURRENT_DOWNLOADS	2	Initial value: parallel downloads, others wait in queue
ALLOWED_PORTS	80,443	Initial value: allowed remote ports, * for any

Web Settings

The Settings dialog edits parallel downloads, free space to keep, allowed ports, default extract and cleanup options, and the theme. Server settings are saved to .settings.json in the download folder and override the initial values above. The theme is stored per browser.

Local Testing

1. Create the download folder first, so Docker does not create it as root:

   mkdir -p data/downloads
   

2. .env is preset for testing: downloads go to ./data/downloads, cookies work over plain HTTP. Both destination drives must be mounted before starting.
3. Start and open http://127.0.0.1:8080 (user admin, password from .env):

   docker compose up -d --build
   

Deployment

1. Make sure PUID/PGID can write to the download folder and to the first level folders of both destination roots.
2. Copy and edit the environment file:

   cp .env.example .env
   

3. Start the service:

   docker compose up -d --build
   

4. Install the nginx site:

   sudo cp deploy/nginx/ddc.conf /etc/nginx/sites-available/ddc.conf
   sudo ln -s /etc/nginx/sites-available/ddc.conf /etc/nginx/sites-enabled/
   sudo nginx -t && sudo systemctl reload nginx
   

Notes

• Moves are instant renames when the download directory and destination share a mount, otherwise files are copied and the source removed.
• Downloads left in the download directory after a restart are listed again as ready.