silverwind 5edc4ba550 Authenticate cache requests via ACTIONS_RUNTIME_TOKEN and scope by repo (#849)
Closes #848. Addresses [GHSA-82g9-637c-2fx2](https://github.com/go-gitea/gitea/security/advisories/GHSA-82g9-637c-2fx2) and the follow-up points raised by @ChristopherHX and @haroutp in that thread.

The change is breaking only for `cache.external_server` which uses auth via a pre-shared secret.

## How auth works now

1. **Runner starts** → opens the embedded cache server on `:port`. Loads / creates a 32-byte HMAC signing key in `<cache-dir>/.secret`.
2. **Runner receives a task** → calls `handler.RegisterJob(ACTIONS_RUNTIME_TOKEN, repository)` before the job runs, defers a revoker that removes the credential on completion. Registrations are reference-counted so a stray re-register cannot revoke a live job.
3. **Job container runs `actions/cache`** → the toolkit sends `Authorization: Bearer $ACTIONS_RUNTIME_TOKEN` on every management call (`reserve`, `upload`, `commit`, `find`, `clean`). The cache server's middleware looks the token up in the registered-jobs map: miss → 401; hit → the job's repository is injected into the request context.
4. **Repository scoping** — every cache entry is stamped with `Repo` on reserve; `find`, `upload`, `commit` all verify the caller's repo matches. A job in repo A cannot see or poison a cache entry owned by repo B, even when both reach the server over the same docker bridge. GC dedup also groups by `(Repo, Key, Version)` so one repo can't age out another.
5. **Archive downloads** — `@actions/cache` does not attach Authorization when downloading `archiveLocation`, so the `find` response is a short-lived HMAC-signed URL: `…/artifacts/:id?exp=<unix>&sig=<hmac>`, 10-minute TTL, signature binds `cacheID:exp`. Tampered, expired, or foreign-secret URLs get 401.
6. **Defence-in-depth** — `ACTIONS_RUNTIME_TOKEN` is added to `task.Secrets` so the runner's log masker scrubs it from step output.

## `cache.external_server` (standalone `act_runner cache-server`)

Operators set `cache.external_secret` to the same value on the runner config and the `act_runner cache-server` config. The `cache-server` then runs with bearer auth on the cache API and exposes a control-plane at `POST /_internal/{register,revoke}` (gated by the shared secret). The runner pre-registers each task's `ACTIONS_RUNTIME_TOKEN` with the remote server before the job runs and revokes it on completion. Same per-job auth + repo scoping as the embedded handler, just over the network.

`cache-server` refuses to start without `cache.external_secret`; runner config load also fails when `cache.external_server` is set without `cache.external_secret`.

## User-facing changes

- **One-time cache miss after upgrade.** Pre-existing entries in `bolt.db` have no `Repo` stamp and won't match any job — they'll be evicted by the normal GC. First job per cache key rebuilds its cache.
- **`cache.external_server` deployments must add `cache.external_secret`.** Breaking change for anyone running a standalone `act_runner cache-server`: set the same `cache.external_secret` in both the runner config and the cache-server config. Without it neither side starts.
- **No config changes required for the default setup.** Runners using the embedded cache server (the common case) keep working without any yaml edits; the auth mechanism is invisible to workflows.

---
This PR was written with the help of Claude Opus 4.7

---------

Co-authored-by: Nicolas <bircni@icloud.com>
Co-authored-by: Christopher Homberger <christopher.homberger@web.de>
Reviewed-on: https://gitea.com/gitea/act_runner/pulls/849
Reviewed-by: ChristopherHX <38043+christopherhx@noreply.gitea.com>
2026-04-27 23:59:20 +00:00
2026-04-24 13:04:47 +02:00
2026-04-24 13:04:47 +02:00
2023-04-04 21:32:04 +08:00
2026-04-22 22:29:06 +02:00

act runner

Act runner is a runner for Gitea.

Installation

Prerequisites

Docker Engine Community version is required for docker mode. To install Docker CE, follow the official install instructions.

Download pre-built binary

Visit here and download the right version for your platform.

Build from source

make build

Build a docker image

make docker

Quickstart

Actions are disabled by default, so you need to add the following to the configuration file of your Gitea instance to enable it:

[actions]
ENABLED=true

Register

./act_runner register

And you will be asked to input:

  1. Gitea instance URL, like http://192.168.8.8:3000/. You should use your gitea instance ROOT_URL as the instance argument and you should not use localhost or 127.0.0.1 as instance IP;
  2. Runner token, you can get it from http://192.168.8.8:3000/admin/actions/runners;
  3. Runner name, you can just leave it blank;
  4. Runner labels, you can just leave it blank.

The process looks like:

INFO Registering runner, arch=amd64, os=darwin, version=0.1.5.
WARN Runner in user-mode.
INFO Enter the Gitea instance URL (for example, https://gitea.com/):
http://192.168.8.8:3000/
INFO Enter the runner token:
fe884e8027dc292970d4e0303fe82b14xxxxxxxx
INFO Enter the runner name (if set empty, use hostname: Test.local):

INFO Enter the runner labels, leave blank to use the default labels (comma-separated, for example, ubuntu-latest:docker://docker.gitea.com/runner-images:ubuntu-latest):

INFO Registering runner, name=Test.local, instance=http://192.168.8.8:3000/, labels=[ubuntu-latest:docker://docker.gitea.com/runner-images:ubuntu-latest ubuntu-22.04:docker://docker.gitea.com/runner-images:ubuntu-22.04 ubuntu-20.04:docker://docker.gitea.com/runner-images:ubuntu-20.04].
DEBU Successfully pinged the Gitea instance server
INFO Runner registered successfully.

You can also register with command line arguments.

./act_runner register --instance http://192.168.8.8:3000 --token <my_runner_token> --no-interactive

If the registry succeed, it will run immediately. Next time, you could run the runner directly.

Run

./act_runner daemon

Run with docker

docker run -e GITEA_INSTANCE_URL=https://your_gitea.com -e GITEA_RUNNER_REGISTRATION_TOKEN=<your_token> -v /var/run/docker.sock:/var/run/docker.sock --name my_runner gitea/act_runner:nightly

Configuration

You can also configure the runner with a configuration file. The configuration file is a YAML file, you can generate a sample configuration file with ./act_runner generate-config.

./act_runner generate-config > config.yaml

You can specify the configuration file path with -c/--config argument.

./act_runner -c config.yaml register # register with config file
./act_runner -c config.yaml daemon # run with config file

You can read the latest version of the configuration file online at config.example.yaml.

Example Deployments

Check out the examples directory for sample deployment types.

Description
A runner for Gitea based on act.
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