Files
act_runner/act/artifactcache/model.go
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

40 lines
1.1 KiB
Go

// Copyright 2023 The Gitea Authors. All rights reserved.
// Copyright 2023 The nektos/act Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package artifactcache
type Request struct {
Key string `json:"key" `
Version string `json:"version"`
Size int64 `json:"cacheSize"`
}
func (c *Request) ToCache() *Cache {
if c == nil {
return nil
}
ret := &Cache{
Key: c.Key,
Version: c.Version,
Size: c.Size,
}
if c.Size == 0 {
// So the request comes from old versions of actions, like `actions/cache@v2`.
// It doesn't send cache size. Set it to -1 to indicate that.
ret.Size = -1
}
return ret
}
type Cache struct {
ID uint64 `json:"id" boltholdKey:"ID"`
Repo string `json:"repo" boltholdIndex:"Repo"`
Key string `json:"key" boltholdIndex:"Key"`
Version string `json:"version" boltholdIndex:"Version"`
Size int64 `json:"cacheSize"`
Complete bool `json:"complete" boltholdIndex:"Complete"`
UsedAt int64 `json:"usedAt" boltholdIndex:"UsedAt"`
CreatedAt int64 `json:"createdAt" boltholdIndex:"CreatedAt"`
}