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enricobuehlerandClaude Opus 5 907985a0b9 docs(packaging/windows): record the driver-signing fingerprint

The stable cert is live and CI is signing with it. Fills in the placeholder in
both docs and adds the one-liner to check an installed driver against it.

Thumbprint 4B8493E7CD565758D335F8F4F05C5A7261A13E02, verified off the .cer a real
windows-host build produced on the runner, not from the key material: RSA 3072,
valid to 2036, extensions 2.5.29.15/37/14 and nothing else. The decisive part is
that the pf-vdisplay and gamepad bundles now carry the SAME thumbprint — the
per-build fallback had each script mint its own 2048-bit cert, so they never
matched. That is what proves the secret reached the build rather than the
fallback quietly running again.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

2026-07-29 13:01:42 +02:00

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Security Policy

punktfunk is a low-latency desktop/game streaming stack. A host is effectively remote control of a machine, so we take security reports seriously and appreciate responsible disclosure.

Reporting a vulnerability

Please report security issues privately by email to security@punktfunk.com.

Do not open a public issue, pull request, or chat/forum post for a suspected vulnerability — that exposes other users before a fix exists.

What to include

The more of this you can give us, the faster we can act:

The component and version (e.g. punktfunk-host 0.9.0, Windows or Linux, which client).
The impact — what an attacker can do, and from what position (same LAN, a local service account, admin, a paired client, …).
Steps to reproduce, a proof-of-concept, or a crash/log if you have one.
Any suggested fix or mitigation (optional).

What to expect

We're a small team, so timelines are best-effort, but we commit to:

Acknowledge your report within 3 business days.
Give an initial assessment (severity + whether we can reproduce) within about 7 days.
Keep you updated, and tell you when a fix ships.
Credit you in the advisory / release notes when the fix is public — unless you'd rather stay anonymous.

We practice coordinated disclosure: please give us reasonable time to release a fix before publishing details. We aim to resolve valid issues within 90 days and will agree a disclosure date with you.

Scope

In scope — the code in this repository:

The host (punktfunk-host), its Windows drivers, and the protocol/crypto core (punktfunk-core).
The native clients (Apple, Linux, Windows, Android), the web management console, and the management API.

Known limits — documented behavior, not vulnerabilities (see https://docs.punktfunk.unom.io/docs/security):

Admin/SYSTEM already on the host = out of scope. An attacker who is already administrator or SYSTEM on the host owns the machine regardless of punktfunk.
The virtual display is a real monitor — any process already in the interactive desktop session can capture it via the normal OS screen-capture APIs, exactly as it could a physical monitor.
GameStream/Moonlight compatibility (--gamestream) uses legacy encryption and is documented as opt-in, trusted-LAN-only.
Public-internet exposure is unsupported — issues that only arise from exposing the host to the WAN are expected; keep the host on a trusted LAN or a VPN.

If you're unsure whether something is in scope, report it anyway — we'd rather hear about it.

Verifying what you downloaded

Every distribution path is authenticated. Nothing below needs an account or a network round trip to us beyond the download itself.

Release-page downloads (DMG, MSIX, setup.exe, APK, decky zip, .deb/.rpm) each ship a <file>.sha256 next to them. In your download directory: sha256sum -c punktfunk-1.2.3.dmg.sha256 (macOS: shasum -a 256 -c …).
RPMs from the dnf repo are OpenPGP-signed with packages@unom.io (AF245C506F4E4763); the repo file in packaging/rpm/README.md sets gpgcheck=1, so dnf checks every package for you. rpmkeys --checksig on a downloaded RPM verifies it by hand.
The Bazzite sysext feed carries a detached signature over its SHA256SUMS, from that same key. punktfunk-sysext verifies it before installing and refuses a feed it cannot verify — the public key is baked into the script rather than fetched from the feed.
Windows installers and MSIX packages are Authenticode-signed; a release build that cannot reach its code-signing certificate fails to build rather than falling back to a self-signed one. Check with Get-AuthenticodeSignature punktfunk-host-setup-1.2.3.exe.
The Windows drivers (virtual display, virtual gamepads) are signed with a stable self-signed certificate, CN=punktfunk-driver (SHA-1 4B8493E7CD565758D335F8F4F05C5A7261A13E02), also published in packaging/windows/README.md. The installer has to add it to the machine's trusted roots for a self-signed driver to install at all, so — unlike the cases above — this signature does not authenticate the download: it gives the drivers a stable publisher identity you can compare against the published fingerprint, and it is removed again on uninstall. Verify with Get-AuthenticodeSignature on the installed pf_vdisplay.dll, or list what is trusted with Get-ChildItem Cert:\LocalMachine\Root | ? Subject -like '*punktfunk*'.

A checksum on its own only tells you the download wasn't corrupted in transit — it says nothing about who produced the file, since anyone able to replace an artifact can replace its checksum. Where that distinction matters (the update feeds, the package repos), the checksums are covered by a signature. If a signature check fails, please don't work around it; report it.

Safe harbor

We consider good-faith security research that follows this policy to be authorized, and we won't pursue legal action against researchers who:

make a good-faith effort to avoid privacy violations, data loss, and service disruption,
only test systems they own or have explicit permission to test,
give us reasonable time to remediate before public disclosure,
don't exfiltrate more data than needed to demonstrate the issue.

Thank you for helping keep punktfunk and its users safe.

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