Signet

Signet is a decentralized code signing network. Unlike traditional systems which focus on authors signing their releases, Signet enables third parties to publish cryptographically verified statements about software. These statements, called attestations, can be published to public respositories which enable global lookup and exchange.

Purpose

Validating the authenticity and security of open source packages is no simple task. How can we assure that the software we use hasn't been tampered with? How do we know it functions as expected? To answer these questions, code must be inspected in a time and labor intensive process. Reviews are typically carried out on a case-by-case basis by individuals and organizations. The results of such reviews are rarely published, and there is no standard way to publish the results of such reviews.

The trustworthiness of the open source ecosystem is a massive shared problem. For large projects with formal release processes such as the Linux kernel, this problem is solved via gpg-signed releases. However, the long tail of github-hosted packages is unsigned. Even if all github users started signing their releases, this approach wouldn't work because there is no central authority (such as the official Linux signing key). The peer-to-peer development community needs a peer-to-peer trust system.

Signet proposes to solve this problem by putting code signing in the hands of users instead of publishers. By opening this process up to the individuals and organizations who depend on open source software, participants in development communities can vouch for each other. Everyone who participates in or uses open source is a stakeholder in trustworthy ecosystem. Signet's aim is to combine everyone's knowledge and individual effort into a federated public index.

Building a trust network is a human problem. Even with easily accessible code signatures, there remains the problem of determining who to trust and how to verify their identities. Building a large network (and the tooling required to maintain it) starts with small groups of people. If you're interested in helping tackle this, check out sig, a small utility which facilitates exchanging code signatures.

sig

:construction: sig is an early proof of concept. Please try it out and give feedback, but proceed with caution! :construction:

The sig tool creates, validates, and publishes attestations, gpg-signed JSON blobs which annotate files. Sig checks attestations with your set of trusted public keys to verify that software has been signed by yourself or trusted third party.

To get started, configure sig with your public key:

$ sig setup B32780D9
Initialized config directory at: /home/demo/.signet/
With public key fingerprint: DFDD705124843F878C6183EBD8C1B99DB32780D9
Welcome to Signet! :)

Let's create an attestation about a file we know about:

$ sig attest ./signet.py
I have reviewed this file (yes/no): yes
It performs as expected and is free of major flaws (yes/no): yes
Comment: My first attestation!
Saved attestation for ./signet.py:
{
  "comment": "My first attestation!",
  "id": "sha256:7c47d79b2e292c509fcdd546ea42427fe3cb02aca40577c1bd8c6f61948c28eb",
  "ok": true,
  "reviewed": true
}

Now to verify the same file:

$ sig verify ./signet.py
identified file as sha256:7c47d79b2e292c509fcdd546ea42427fe3cb02aca40577c1bd8c6f61948c28eb
ok [B32780D9] Dev Test Key <test@demo.com>
file /mnt/shared/signet.py is ok.

Your attestations are stored in a repository at ~/.signet/repo. You can publish this directory on the internet to share it with other people.

Let's fetch another repository:

$ sig remote add hello-world http://world.com/signet/
$ sig fetch
GET http://world.com/signet/repo.json... done.
GET http://world.com/signet/key.asc... done.
Imported [D9886717] Hello World <hello@world.com>.

Now if we verify a file they have signed:

$ sig verify ./test.txt
identified file as sha256:91751cee0a1ab8414400238a761411daa29643ab4b8243e9a91649e25be53ada
untrusted [D9886717] Hello World <hello@world.com>
file /mnt/shared/signet.py is not verified.

We need to mark the new repo's key as trusted before sig verify will use its attestations:

$ sig trust add B32780D9
Trusted: [D9886717] Hello World <hello@world.com>

If we verify the file again, we can see that it is now accepted.

$ sig verify ./test.txt
identified file as sha256:91751cee0a1ab8414400238a761411daa29643ab4b8243e9a91649e25be53ada
ok [D9886717] Hello World <hello@world.com>
file /mnt/shared/signet.py is ok.

A complete listing of available sig commands can be viewed via sig help.

Data Formats

Attestations

An attestation is a signed JSON blob of arbitrary data. It consists of the following properties:

{
    "data": { ... },
    "key": "full gpg key fingerprint (SHA1)",
    "sig": "base64-encoded gpg signature of json-encoded data property (keys sorted alphabetically)"
}

Currently, sig records the following data in attestations:

"data": {
    "comment": "My first attestation!",
    "id": "sha256:7c47d79b2e292c509fcdd546ea42427fe3cb02aca40577c1bd8c6f61948c28eb",

    // is this file trustworthy, and does it perform as expected?
    "ok": true,

    // has this file been reviewed by a human?
    "reviewed": true
},

Repositories

A repository stores a mapping of identifiers (file content hashes) to attestations. This is wrapped inside its own attestation made by the owner of the repository. It also contains a version number to aid future format changes.

{
    "data": {
        "attestations": {
            "sha256:7c47d79b2e292c509fcdd546ea42427fe3cb02aca40577c1bd8c6f61948c28eb": [
                {
                    "data": { ... },
                    "key": "...",
                    "sig": "..."
                }
            ],
            "sha256:91751cee0a1ab8414400238a761411daa29643ab4b8243e9a91649e25be53ada": [
                {
                    "data": { ... },
                    "key": "...",
                    "sig": "..."
                }
            ]
        },
        "version": "0.0.1"
    },
    "key": "repo attestation key fingerprint",
    "sig": "repo attestation signature"
}

Future plans

Please the issues listing for planned features and open projects.