Please do not open a public issue for a security problem. Report it privately through GitHub: go to the repository's Security tab and choose Report a vulnerability.

Include what an attacker can do, the steps to reproduce it and the version (the release or commit) you tested. Never send a real NOTIFY_TOKEN. You will get an answer as soon as possible, and credit in the fix if you want it.

Only the latest release and master are supported; fixes are not backported.

dont-dry is meant to run on a home or office local network, next to the printer.

• It listens on nothing. dont-dry only makes outgoing connections: to the printer and, if set, to the notification URL. There is no port to expose.
• The printer is not fully trusted. Answers are size-capped and parsed defensively; a malformed or oversized answer is reported as a failed print, never a crash.
• Settings are checked at start-up. The printer and notification addresses must be ipp://, ipps://, http:// or https:// URLs without a user name or password in them. NOTIFY_TOKEN is never logged, and logs and messages show URLs without their query string.
• Notifications go where you point them. They never follow a redirect, which would carry the token to another address.
• The image is minimal and unprivileged. It runs as a fixed non-root user, needs no capabilities, works with a read-only file system, and installs Python packages at exact versions checked against their hashes, on a base image pinned by digest.
• The systemd unit is sandboxed. A throwaway user that can only write /var/lib/dont-dry, with no capabilities and a system call filter. Its settings file, /etc/dont-dry.env, is readable by root only.
• First installs start from a release. The documented commands download install.sh and create-lxc.sh attached to the latest release, which CI takes from the signed tag, with a SHA256SUMS file to check them.
• Installs are verified. deploy/install.sh (also run by the Proxmox script) installs a release only when its tag is signed with the dont-dry release key and names itself with that same version, and the Python packages at exact versions checked against their hashes. An update never moves back to an older release. A branch or tag you name with --ref is installed as it is.
• Images come from signed tags. CI publishes release images only from a tag signed with a key in master's RELEASE_SIGNERS, with a provenance attestation: gh attestation verify oci://ghcr.io/frkey/dont-dry:latest --owner frkey.
• The supply chain is pinned. CI runs with a read-only token that checkouts do not keep, pins its actions by commit and its own tools with hashes, audits the locked packages for known vulnerabilities every week, and publishes images with provenance and an SBOM. Dependabot proposes updates.

These are accepted trade-offs, documented so you can decide whether they fit your network:

• ipp:// is plain HTTP. Anyone who can watch your network traffic can see the test page (it holds nothing private). Use ipps:// to encrypt it.
• Printer certificates are not checked by default. Printers almost always ship a self-signed certificate, so ipps:// encrypts but does not authenticate unless TLS_VERIFY=true and the printer has a certificate your system trusts.
• The notification URL is a secret of sorts. On ntfy.sh, anyone who knows the topic can read it; pick a long random topic or use a token on a server you control.