refactor: move act under internal

The runner is an application, not a library. `act/model` and
`act/exprparser` were the last packages anything outside this repository
consumed and they now live in actionslib, so nothing needs the rest of
`act` to be importable, and keeping it importable invites the coupling
that was just removed.

Import paths only, the files are unchanged.

Assisted-by: Codet:GPT-5.1-Codex

internal/act/artifactcache/doc.go

@@ -0,0 +1,12 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// Copyright 2023 The nektos/act Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+// Package artifactcache provides a cache handler for the runner.
+//
+// Inspired by https://github.com/sp-ricard-valverde/github-act-cache-server
+//
+// TODO: Authorization
+// TODO: Restrictions for accessing a cache, see https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#restrictions-for-accessing-a-cache
+// TODO: Force deleting cache entries, see https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#force-deleting-cache-entries
+package artifactcache

internal/act/artifactcache/handler.go

@@ -0,0 +1,962 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// Copyright 2023 The nektos/act Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package artifactcache
+
+import (
+	"context"
+	"crypto/hmac"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"gitea.com/gitea/runner/internal/act/common"
+
+	"github.com/julienschmidt/httprouter"
+	"github.com/sirupsen/logrus"
+	"github.com/timshannon/bolthold"
+	"go.etcd.io/bbolt"
+)
+
+const (
+	apiPath      = "/_apis/artifactcache"
+	internalPath = "/_internal"
+
+	// artifactURLTTL bounds how long a signed artifactLocation URL stays valid.
+	// Short enough that a leaked URL is near-worthless; long enough to let the
+	// @actions/cache client download a big blob that was returned from /cache.
+	artifactURLTTL = 10 * time.Minute
+)
+
+type credKey struct{}
+
+// JobCredential ties a per-job bearer token (ACTIONS_RUNTIME_TOKEN) to the
+// repository that owns it. Every cache entry is stamped with Repo on
+// reserve/commit and checked on read/write so one repo can never observe or
+// poison another repo's cache, even from inside a container that reaches the
+// cache server over the docker bridge network.
+type JobCredential struct {
+	Repo string `json:"repo"`
+
+	// Results is the instance whose artifact service this server forwards for the job, and
+	// InsecureTLS how the runner reaches it; see results.go. The tags are the wire format a
+	// remote runner registers with.
+	Results     string `json:"results"`
+	InsecureTLS bool   `json:"insecure_tls"`
+}
+
+// credEntry holds a registered job's credential along with an active
+// registration count. RegisterJob is reference-counted so that if two tasks
+// briefly share an ACTIONS_RUNTIME_TOKEN — e.g. a runner that retries a task
+// after a crash before the old registration is revoked — the first task's
+// revoker does not cut the second task's auth out from under it.
+type credEntry struct {
+	cred JobCredential
+	refs int
+}
+
+type Handler struct {
+	dir      string
+	storage  *Storage
+	router   *httprouter.Router
+	listener net.Listener
+	port     int
+	server   *http.Server
+	logger   logrus.FieldLogger
+
+	gcing atomic.Bool
+	gcAt  time.Time
+
+	outboundIP string
+
+	// internalSecret guards /_internal/{register,revoke}. When set, a remote
+	// runner can use these endpoints to pre-register per-job
+	// ACTIONS_RUNTIME_TOKENs against this server, enabling the same
+	// per-job auth and repo scoping as the embedded handler over the
+	// network. Empty disables the control-plane entirely.
+	internalSecret string
+
+	// secret signs short-lived artifact download URLs. The @actions/cache
+	// toolkit does not send Authorization on the download request, so blob
+	// GETs authenticate via a per-URL HMAC signature with expiry rather than
+	// via the bearer token used for management endpoints.
+	secret []byte
+
+	credMu sync.RWMutex
+	creds  map[string]*credEntry
+}
+
+// StartHandler opens the on-disk cache store and starts the HTTP server.
+//
+// internalSecret, when non-empty, enables a control-plane API at
+// /_internal/{register,revoke} that lets a remote runner pre-register the
+// per-job ACTIONS_RUNTIME_TOKENs it expects this server to honor. The
+// embedded in-process handler leaves it empty and registers tokens via the
+// in-process RegisterJob method directly.
+func StartHandler(dir, outboundIP string, port uint16, internalSecret string, logger logrus.FieldLogger) (*Handler, error) {
+	h := &Handler{
+		creds:          make(map[string]*credEntry),
+		internalSecret: internalSecret,
+	}
+
+	if logger == nil {
+		discard := logrus.New()
+		discard.Out = io.Discard
+		logger = discard
+	}
+	logger = logger.WithField("module", "artifactcache")
+	h.logger = logger
+
+	if dir == "" {
+		home, err := os.UserHomeDir()
+		if err != nil {
+			return nil, err
+		}
+		dir = filepath.Join(home, ".cache", "actcache")
+	}
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		return nil, err
+	}
+
+	h.dir = dir
+
+	storage, err := NewStorage(filepath.Join(dir, "cache"))
+	if err != nil {
+		return nil, err
+	}
+	h.storage = storage
+
+	if outboundIP != "" {
+		h.outboundIP = outboundIP
+	} else if ip := common.GetOutboundIP(); ip == nil {
+		return nil, errors.New("unable to determine outbound IP address")
+	} else {
+		h.outboundIP = ip.String()
+	}
+
+	secret, err := loadOrCreateSecret(dir)
+	if err != nil {
+		return nil, err
+	}
+	h.secret = secret
+
+	router := httprouter.New()
+	router.GET(apiPath+"/cache", h.bearerAuth(h.find))
+	router.POST(apiPath+"/caches", h.bearerAuth(h.reserve))
+	router.PATCH(apiPath+"/caches/:id", h.bearerAuth(h.upload))
+	router.POST(apiPath+"/caches/:id", h.bearerAuth(h.commit))
+	router.POST(apiPath+"/clean", h.bearerAuth(h.clean))
+	// Artifact GET is signed via query-string HMAC because @actions/cache
+	// does not attach Authorization when downloading archiveLocation.
+	router.GET(apiPath+"/artifacts/:id", h.signedAuth("", h.get))
+	// Control-plane: a remote runner registers/revokes per-job tokens so the
+	// cache API can authenticate them. Always wired so the routes exist; the
+	// handlers themselves 401 when internalSecret is unset.
+	router.POST(internalPath+"/register", h.internalAuth(h.internalRegister))
+	router.POST(internalPath+"/revoke", h.internalAuth(h.internalRevoke))
+	h.registerV2Routes(router)
+	router.NotFound = http.HandlerFunc(h.forwardOrNotFound)
+
+	h.router = router
+
+	h.gcCache()
+
+	// Listen on all interfaces. Binding to outboundIP only would give no real
+	// security benefit (it is the LAN/internet-facing address either way) and
+	// can break Docker Desktop variants where the host's outbound IP is not
+	// routable from inside the container network. Authentication is enforced
+	// by the bearer middleware and per-repo scoping, not by reachability.
+	listener, err := net.Listen("tcp", fmt.Sprintf(":%d", port))
+	if err != nil {
+		return nil, err
+	}
+	addr, ok := listener.Addr().(*net.TCPAddr)
+	if !ok {
+		listener.Close()
+		return nil, fmt.Errorf("cache server listens on %T, want a TCP address", listener.Addr())
+	}
+	h.port = addr.Port
+	server := &http.Server{
+		ReadHeaderTimeout: 2 * time.Second,
+		Handler:           router,
+	}
+	go func() {
+		if err := server.Serve(listener); err != nil && errors.Is(err, net.ErrClosed) {
+			logger.Errorf("http serve: %v", err)
+		}
+	}()
+	h.listener = listener
+	h.server = server
+
+	return h, nil
+}
+
+func (h *Handler) ExternalURL() string {
+	// TODO: make the external url configurable if necessary
+	return fmt.Sprintf("http://%s:%d", h.outboundIP, h.port)
+}
+
+// RegisterJob makes token a valid bearer credential for cache requests from
+// the given repository and returns a function that removes it. The runner
+// calls this at job start and defers the returned func so that the credential
+// is only accepted while the job is running.
+//
+// Registrations are reference-counted: if a token is already registered, the
+// credential it was registered with is kept and the refcount is incremented.
+// The entry is removed only when every revoker returned by RegisterJob has
+// been called.
+// This keeps a stray re-registration from silently revoking a live job.
+func (h *Handler) RegisterJob(token string, cred JobCredential) func() {
+	if h == nil || token == "" {
+		return func() {}
+	}
+	h.credMu.Lock()
+	if existing, ok := h.creds[token]; ok {
+		existing.refs++
+	} else {
+		h.creds[token] = &credEntry{
+			cred: cred,
+			refs: 1,
+		}
+	}
+	h.credMu.Unlock()
+	return func() {
+		h.credMu.Lock()
+		if entry, ok := h.creds[token]; ok {
+			entry.refs--
+			if entry.refs <= 0 {
+				delete(h.creds, token)
+			}
+		}
+		h.credMu.Unlock()
+	}
+}
+
+// RevokeJob explicitly revokes one registration of token, mirroring one call
+// of the closure returned by RegisterJob. Used by the control-plane endpoint
+// so a remote runner can revoke without holding the closure.
+func (h *Handler) RevokeJob(token string) {
+	if h == nil || token == "" {
+		return
+	}
+	h.credMu.Lock()
+	if entry, ok := h.creds[token]; ok {
+		entry.refs--
+		if entry.refs <= 0 {
+			delete(h.creds, token)
+		}
+	}
+	h.credMu.Unlock()
+}
+
+func (h *Handler) lookupCredential(token string) (JobCredential, bool) {
+	h.credMu.RLock()
+	entry, ok := h.creds[token]
+	h.credMu.RUnlock()
+	if !ok {
+		return JobCredential{}, false
+	}
+	return entry.cred, true
+}
+
+// loadOrCreateSecret returns the 32-byte HMAC signing key for artifact URLs,
+// persisted in dir/.secret so signed URLs handed out before a restart stay
+// valid across the restart and so the standalone cache-server can be pointed
+// at by config.Cache.ExternalServer without the URL rotating.
+func loadOrCreateSecret(dir string) ([]byte, error) {
+	path := filepath.Join(dir, ".secret")
+	if data, err := os.ReadFile(path); err == nil {
+		if secret, err := hex.DecodeString(strings.TrimSpace(string(data))); err == nil && len(secret) >= 32 {
+			return secret, nil
+		}
+	} else if !os.IsNotExist(err) {
+		return nil, fmt.Errorf("read cache secret: %w", err)
+	}
+	secret := make([]byte, 32)
+	if _, err := rand.Read(secret); err != nil {
+		return nil, fmt.Errorf("generate cache secret: %w", err)
+	}
+	if err := os.WriteFile(path, []byte(hex.EncodeToString(secret)), 0o600); err != nil {
+		return nil, fmt.Errorf("write cache secret: %w", err)
+	}
+	return secret, nil
+}
+
+func (h *Handler) Close() error {
+	if h == nil {
+		return nil
+	}
+	var retErr error
+	if h.server != nil {
+		err := h.server.Close()
+		if err != nil {
+			retErr = err
+		}
+		h.server = nil
+	}
+	if h.listener != nil {
+		err := h.listener.Close()
+		if errors.Is(err, net.ErrClosed) {
+			err = nil
+		}
+		if err != nil {
+			retErr = err
+		}
+		h.listener = nil
+	}
+	return retErr
+}
+
+func (h *Handler) openDB() (*bolthold.Store, error) {
+	return bolthold.Open(filepath.Join(h.dir, "bolt.db"), 0o644, &bolthold.Options{
+		Encoder: json.Marshal,
+		Decoder: json.Unmarshal,
+		Options: &bbolt.Options{
+			Timeout:      5 * time.Second,
+			NoGrowSync:   bbolt.DefaultOptions.NoGrowSync,
+			FreelistType: bbolt.DefaultOptions.FreelistType,
+		},
+	})
+}
+
+// GET /_apis/artifactcache/cache
+func (h *Handler) find(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
+	cred := credFromContext(r.Context())
+	keys := strings.Split(r.URL.Query().Get("keys"), ",")
+	version := r.URL.Query().Get("version")
+
+	db, err := h.openDB()
+	if err != nil {
+		h.responseJSON(w, r, 500, err)
+		return
+	}
+	defer db.Close()
+
+	cache, err := h.lookupCache(db, cred.Repo, keys, version)
+	if err != nil {
+		h.responseJSON(w, r, 500, err)
+		return
+	}
+	if cache == nil {
+		h.responseJSON(w, r, 204)
+		return
+	}
+	h.responseJSON(w, r, 200, map[string]any{
+		"result":          "hit",
+		"archiveLocation": h.signedArtifactURL(cache.ID, time.Now().Add(artifactURLTTL)),
+		"cacheKey":        cache.Key,
+	})
+}
+
+// lookupCache returns the entry to restore for these keys, or (nil, nil) when there is none:
+// either nothing matched, or the match had lost its blob to a prune, in which case the dangling
+// entry is dropped on the way out.
+func (h *Handler) lookupCache(db *bolthold.Store, repo string, keys []string, version string) (*Cache, error) {
+	cache, err := findCache(db, repo, keys, version)
+	if err != nil || cache == nil {
+		return nil, err
+	}
+	ok, err := h.storage.Exist(cache.ID)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		_ = db.Delete(cache.ID, cache)
+		return nil, nil //nolint:nilnil // absence is not an error here
+	}
+	return cache, nil
+}
+
+// POST /_apis/artifactcache/caches
+func (h *Handler) reserve(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
+	cred := credFromContext(r.Context())
+	api := &Request{}
+	if err := json.NewDecoder(r.Body).Decode(api); err != nil {
+		h.responseJSON(w, r, 400, err)
+		return
+	}
+
+	cache := api.ToCache()
+	cache.Repo = cred.Repo
+	db, err := h.openDB()
+	if err != nil {
+		h.responseJSON(w, r, 500, err)
+		return
+	}
+	defer db.Close()
+
+	now := time.Now().Unix()
+	cache.CreatedAt = now
+	cache.UsedAt = now
+	if err := insertCache(db, cache); err != nil {
+		h.responseJSON(w, r, 500, err)
+		return
+	}
+	h.responseJSON(w, r, 200, map[string]any{
+		"cacheId": cache.ID,
+	})
+}
+
+// PATCH /_apis/artifactcache/caches/:id
+func (h *Handler) upload(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
+	cred := credFromContext(r.Context())
+	id, err := strconv.ParseInt(params.ByName("id"), 10, 64)
+	if err != nil {
+		h.responseJSON(w, r, 400, err)
+		return
+	}
+
+	cache := &Cache{}
+	db, err := h.openDB()
+	if err != nil {
+		h.responseJSON(w, r, 500, err)
+		return
+	}
+	defer db.Close()
+	if err := db.Get(id, cache); err != nil {
+		if errors.Is(err, bolthold.ErrNotFound) {
+			h.responseJSON(w, r, 400, fmt.Errorf("cache %d: not reserved", id))
+			return
+		}
+		h.responseJSON(w, r, 500, err)
+		return
+	}
+
+	if cache.Repo != cred.Repo {
+		h.responseJSON(w, r, 403, fmt.Errorf("cache %d: forbidden", id))
+		return
+	}
+
+	if cache.Complete {
+		h.responseJSON(w, r, 400, fmt.Errorf("cache %v %q: already complete", cache.ID, cache.Key))
+		return
+	}
+	db.Close()
+	start, _, err := parseContentRange(r.Header.Get("Content-Range"))
+	if err != nil {
+		h.responseJSON(w, r, 400, err)
+		return
+	}
+	if err := h.storage.Write(cache.ID, start, r.Body); err != nil {
+		h.responseJSON(w, r, 500, err)
+		return
+	}
+	_ = h.touchCache(uint64(id), false)
+	h.responseJSON(w, r, 200)
+}
+
+// POST /_apis/artifactcache/caches/:id
+func (h *Handler) commit(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
+	cred := credFromContext(r.Context())
+	id, err := strconv.ParseInt(params.ByName("id"), 10, 64)
+	if err != nil {
+		h.responseJSON(w, r, 400, err)
+		return
+	}
+
+	cache := &Cache{}
+	db, err := h.openDB()
+	if err != nil {
+		h.responseJSON(w, r, 500, err)
+		return
+	}
+	defer db.Close()
+	if err := db.Get(id, cache); err != nil {
+		if errors.Is(err, bolthold.ErrNotFound) {
+			h.responseJSON(w, r, 400, fmt.Errorf("cache %d: not reserved", id))
+			return
+		}
+		h.responseJSON(w, r, 500, err)
+		return
+	}
+
+	if cache.Repo != cred.Repo {
+		h.responseJSON(w, r, 403, fmt.Errorf("cache %d: forbidden", id))
+		return
+	}
+
+	if cache.Complete {
+		h.responseJSON(w, r, 400, fmt.Errorf("cache %v %q: already complete", cache.ID, cache.Key))
+		return
+	}
+
+	db.Close()
+
+	if err := h.commitCache(cache); err != nil {
+		h.responseJSON(w, r, 500, err)
+		return
+	}
+
+	h.responseJSON(w, r, 200)
+}
+
+// commitCache assembles the uploaded parts and marks the entry complete. The caller must
+// have closed its store first: Commit concatenates the whole archive and would otherwise
+// hold bolt's exclusive file lock for the duration.
+func (h *Handler) commitCache(cache *Cache) error {
+	written, err := h.storage.Commit(cache.ID, cache.Size)
+	if err != nil {
+		return err
+	}
+	// write real size back to cache, it may be different from the current value when the request doesn't specify it.
+	cache.Size = written
+	cache.Complete = true
+
+	db, err := h.openDB()
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+	return db.Update(cache.ID, cache)
+}
+
+// GET /_apis/artifactcache/artifacts/:id
+// Authenticated via signed URL (see signedAuth), not bearer, because the
+// @actions/cache toolkit downloads archiveLocation without Authorization.
+// Repository scoping is already enforced at find() time; the signature binds
+// the URL to the specific cache ID and an expiry.
+func (h *Handler) get(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
+	id, err := strconv.ParseInt(params.ByName("id"), 10, 64)
+	if err != nil {
+		h.responseJSON(w, r, 400, err)
+		return
+	}
+	_ = h.touchCache(uint64(id), false)
+	h.storage.Serve(w, r, uint64(id))
+}
+
+// POST /_apis/artifactcache/clean
+func (h *Handler) clean(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
+	// TODO: don't support force deleting cache entries
+	// see: https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#force-deleting-cache-entries
+
+	h.responseJSON(w, r, 200)
+}
+
+// bearerAuth resolves ACTIONS_RUNTIME_TOKEN against the set of currently
+// registered jobs. A match attaches the job's JobCredential to the request
+// context; a miss returns 401 before the handler body runs.
+func (h *Handler) bearerAuth(handler httprouter.Handle) httprouter.Handle {
+	return func(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
+		h.logger.Debugf("%s %s", r.Method, r.URL.Path)
+		token := bearerToken(r)
+		if token == "" {
+			h.responseJSON(w, r, http.StatusUnauthorized, errors.New("missing bearer token"))
+			return
+		}
+		cred, ok := h.lookupCredential(token)
+		if !ok {
+			h.responseJSON(w, r, http.StatusUnauthorized, errors.New("unknown bearer token"))
+			return
+		}
+		ctx := context.WithValue(r.Context(), credKey{}, cred)
+		handler(w, r.WithContext(ctx), params)
+		go h.gcCache()
+	}
+}
+
+// signedAuth authenticates a signed URL. purpose separates the flavours of URL the
+// handler hands out, so one cannot be replayed as another; see computeSignature.
+func (h *Handler) signedAuth(purpose string, handler httprouter.Handle) httprouter.Handle {
+	return func(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
+		h.logger.Debugf("%s %s", r.Method, r.URL.Path)
+		id, err := strconv.ParseInt(params.ByName("id"), 10, 64)
+		if err != nil {
+			h.responseJSON(w, r, 400, err)
+			return
+		}
+		expStr := r.URL.Query().Get("exp")
+		sig := r.URL.Query().Get("sig")
+		if expStr == "" || sig == "" {
+			h.responseJSON(w, r, http.StatusUnauthorized, errors.New("missing signature"))
+			return
+		}
+		exp, err := strconv.ParseInt(expStr, 10, 64)
+		if err != nil {
+			h.responseJSON(w, r, http.StatusUnauthorized, errors.New("invalid expiry"))
+			return
+		}
+		if time.Now().Unix() > exp {
+			h.responseJSON(w, r, http.StatusUnauthorized, errors.New("signature expired"))
+			return
+		}
+		expected := h.computeSignature(purpose, id, exp)
+		if !hmac.Equal([]byte(sig), []byte(expected)) {
+			h.responseJSON(w, r, http.StatusUnauthorized, errors.New("bad signature"))
+			return
+		}
+		handler(w, r, params)
+		go h.gcCache()
+	}
+}
+
+// internalAuth gates the control-plane endpoints. The bearer must
+// constant-time-equal the configured internalSecret. If the secret is empty,
+// the control-plane is disabled and every request gets 404 — which matches
+// the upstream nektos/act behavior of "the route does not exist".
+func (h *Handler) internalAuth(handler httprouter.Handle) httprouter.Handle {
+	return func(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
+		if h.internalSecret == "" {
+			http.NotFound(w, r)
+			return
+		}
+		token := bearerToken(r)
+		if token == "" || !hmac.Equal([]byte(token), []byte(h.internalSecret)) {
+			h.responseJSON(w, r, http.StatusUnauthorized, errors.New("internal: bad secret"))
+			return
+		}
+		handler(w, r, params)
+	}
+}
+
+type internalRegisterBody struct {
+	Token string `json:"token"`
+	JobCredential
+}
+
+type internalRevokeBody struct {
+	Token string `json:"token"`
+}
+
+// POST /_internal/register
+// ResultsURL is what a job registered with cred should be given as ACTIONS_RESULTS_URL, or "" when
+// the credential names no instance to forward the artifact half to.
+func (h *Handler) ResultsURL(cred JobCredential) string {
+	if h == nil || cred.Results == "" {
+		return ""
+	}
+	return h.ExternalURL()
+}
+
+func (h *Handler) internalRegister(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
+	var body internalRegisterBody
+	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+		h.responseJSON(w, r, http.StatusBadRequest, err)
+		return
+	}
+	if body.Token == "" {
+		h.responseJSON(w, r, http.StatusBadRequest, errors.New("token is required"))
+		return
+	}
+	h.RegisterJob(body.Token, body.JobCredential)
+	// A server too old to forward answers without this, which is how the caller knows.
+	h.responseJSON(w, r, http.StatusOK, map[string]any{"results_url": h.ResultsURL(body.JobCredential)})
+}
+
+// POST /_internal/revoke
+func (h *Handler) internalRevoke(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
+	var body internalRevokeBody
+	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+		h.responseJSON(w, r, http.StatusBadRequest, err)
+		return
+	}
+	if body.Token == "" {
+		h.responseJSON(w, r, http.StatusBadRequest, errors.New("token is required"))
+		return
+	}
+	h.RevokeJob(body.Token)
+	h.responseJSON(w, r, http.StatusOK)
+}
+
+func bearerToken(r *http.Request) string {
+	auth := r.Header.Get("Authorization")
+	const prefix = "Bearer "
+	if len(auth) > len(prefix) && strings.EqualFold(auth[:len(prefix)], prefix) {
+		return auth[len(prefix):]
+	}
+	return ""
+}
+
+func credFromContext(ctx context.Context) JobCredential {
+	if cred, ok := ctx.Value(credKey{}).(JobCredential); ok {
+		return cred
+	}
+	return JobCredential{}
+}
+
+// computeSignature signs a URL for one cache entry and expiry. purpose is mixed into the
+// message so a URL handed out for writing an entry cannot be replayed to read one, and the
+// other way round. Downloads use the empty purpose, the message v1 has always signed.
+func (h *Handler) computeSignature(purpose string, cacheID, exp int64) string {
+	mac := hmac.New(sha256.New, h.secret)
+	fmt.Fprintf(mac, "%s%d:%d", purpose, cacheID, exp)
+	return hex.EncodeToString(mac.Sum(nil))
+}
+
+// signedURL builds a URL under path that signedAuth accepts for the same purpose.
+func (h *Handler) signedURL(path, purpose string, cacheID uint64, exp time.Time) string {
+	expUnix := exp.Unix()
+	q := url.Values{}
+	q.Set("exp", strconv.FormatInt(expUnix, 10))
+	q.Set("sig", h.computeSignature(purpose, int64(cacheID), expUnix))
+	return fmt.Sprintf("%s%s/%d?%s", h.ExternalURL(), path, cacheID, q.Encode())
+}
+
+func (h *Handler) signedArtifactURL(cacheID uint64, exp time.Time) string {
+	return h.signedURL(apiPath+"/artifacts", "", cacheID, exp)
+}
+
+// if not found, return (nil, nil) instead of an error.
+func findCache(db *bolthold.Store, repo string, keys []string, version string) (*Cache, error) {
+	cache := &Cache{}
+	for _, prefix := range keys {
+		// if a key in the list matches exactly, don't return partial matches
+		exact, err := findExactCache(db, repo, prefix, version, true)
+		if err != nil {
+			return nil, err
+		}
+		if exact != nil {
+			return exact, nil
+		}
+		prefixPattern := "^" + regexp.QuoteMeta(prefix)
+		re, err := regexp.Compile(prefixPattern)
+		if err != nil {
+			continue
+		}
+		if err := db.FindOne(cache,
+			bolthold.Where("Repo").Eq(repo).
+				And("Key").RegExp(re).
+				And("Version").Eq(version).
+				And("Complete").Eq(true).
+				SortBy("CreatedAt").Reverse()); err != nil {
+			if errors.Is(err, bolthold.ErrNotFound) {
+				continue
+			}
+			return nil, fmt.Errorf("find cache: %w", err)
+		}
+		return cache, nil
+	}
+	return nil, nil //nolint:nilnil // pre-existing issue from nektos/act
+}
+
+// findExactCache returns the entry for exactly this key and version, or (nil, nil) if there is
+// none. Unlike findCache it never falls back to a prefix (restore-key) match, which is what both
+// its callers need: a new key that is only a prefix of an existing key is not the same entry.
+//
+// A completed entry is the one to restore, sorted by when it was written. An incomplete one is a
+// reservation being uploaded to, sorted by when it was last written to, because the upload route
+// touches UsedAt on every part.
+func findExactCache(db *bolthold.Store, repo, key, version string, complete bool) (*Cache, error) {
+	sortBy := "UsedAt"
+	if complete {
+		sortBy = "CreatedAt"
+	}
+	cache := &Cache{}
+	err := db.FindOne(cache,
+		bolthold.Where("Repo").Eq(repo).
+			And("Key").Eq(key).
+			And("Version").Eq(version).
+			And("Complete").Eq(complete).
+			SortBy(sortBy).Reverse())
+	if errors.Is(err, bolthold.ErrNotFound) {
+		return nil, nil //nolint:nilnil // absence is not an error here
+	}
+	if err != nil {
+		return nil, fmt.Errorf("find cache: %w", err)
+	}
+	return cache, nil
+}
+
+func insertCache(db *bolthold.Store, cache *Cache) error {
+	if err := db.Insert(bolthold.NextSequence(), cache); err != nil {
+		return fmt.Errorf("insert cache: %w", err)
+	}
+	// write back id to db
+	if err := db.Update(cache.ID, cache); err != nil {
+		return fmt.Errorf("write back id to db: %w", err)
+	}
+	return nil
+}
+
+// touchCache stamps UsedAt so gcCache does not reap an entry mid-upload. With requireIncomplete
+// it also refuses an entry that is already complete, which is what the v2 blob route needs: its
+// upload URL outlives the finalize call, and overwriting a finished entry would leave the blob
+// other jobs restore no longer matching its recorded size. An entry missing from the store is
+// accepted, since the signature proves the id was handed out.
+func (h *Handler) touchCache(id uint64, requireIncomplete bool) error {
+	db, err := h.openDB()
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+
+	cache := &Cache{}
+	if err := db.Get(id, cache); err != nil {
+		if errors.Is(err, bolthold.ErrNotFound) {
+			return nil
+		}
+		return err
+	}
+	if requireIncomplete && cache.Complete {
+		return fmt.Errorf("cache %d: already complete", id)
+	}
+	cache.UsedAt = time.Now().Unix()
+	return db.Update(cache.ID, cache)
+}
+
+const (
+	keepUsed   = 30 * 24 * time.Hour
+	keepUnused = 7 * 24 * time.Hour
+	keepTemp   = 5 * time.Minute
+	keepOld    = 5 * time.Minute
+)
+
+func (h *Handler) gcCache() {
+	if h.gcing.Load() {
+		return
+	}
+	if !h.gcing.CompareAndSwap(false, true) {
+		return
+	}
+	defer h.gcing.Store(false)
+
+	if time.Since(h.gcAt) < time.Hour {
+		h.logger.Debugf("skip gc: %v", h.gcAt.String())
+		return
+	}
+	h.gcAt = time.Now()
+	h.logger.Debugf("gc: %v", h.gcAt.String())
+
+	db, err := h.openDB()
+	if err != nil {
+		return
+	}
+	defer db.Close()
+
+	// Remove the caches which are not completed for a while, they are most likely to be broken.
+	var caches []*Cache
+	if err := db.Find(&caches, bolthold.
+		Where("UsedAt").Lt(time.Now().Add(-keepTemp).Unix()).
+		And("Complete").Eq(false),
+	); err != nil {
+		h.logger.Warnf("find caches: %v", err)
+	} else {
+		for _, cache := range caches {
+			h.storage.Remove(cache.ID)
+			if err := db.Delete(cache.ID, cache); err != nil {
+				h.logger.Warnf("delete cache: %v", err)
+				continue
+			}
+			h.logger.Infof("deleted cache: %+v", cache)
+		}
+	}
+
+	// Remove the old caches which have not been used recently.
+	caches = caches[:0]
+	if err := db.Find(&caches, bolthold.
+		Where("UsedAt").Lt(time.Now().Add(-keepUnused).Unix()),
+	); err != nil {
+		h.logger.Warnf("find caches: %v", err)
+	} else {
+		for _, cache := range caches {
+			h.storage.Remove(cache.ID)
+			if err := db.Delete(cache.ID, cache); err != nil {
+				h.logger.Warnf("delete cache: %v", err)
+				continue
+			}
+			h.logger.Infof("deleted cache: %+v", cache)
+		}
+	}
+
+	// Remove the old caches which are too old.
+	caches = caches[:0]
+	if err := db.Find(&caches, bolthold.
+		Where("CreatedAt").Lt(time.Now().Add(-keepUsed).Unix()),
+	); err != nil {
+		h.logger.Warnf("find caches: %v", err)
+	} else {
+		for _, cache := range caches {
+			h.storage.Remove(cache.ID)
+			if err := db.Delete(cache.ID, cache); err != nil {
+				h.logger.Warnf("delete cache: %v", err)
+				continue
+			}
+			h.logger.Infof("deleted cache: %+v", cache)
+		}
+	}
+
+	// Remove the old caches with the same key and version within the same
+	// repository, keep the latest one. Aggregation must include Repo so two
+	// repos that happen to share a (key, version) do not evict each other —
+	// otherwise per-repo scoping holds for reads but one repo can age
+	// another out after keepOld.
+	// Also keep the olds which have been used recently for a while in case of the cache is still in use.
+	if results, err := db.FindAggregate(
+		&Cache{},
+		bolthold.Where("Complete").Eq(true),
+		"Repo", "Key", "Version",
+	); err != nil {
+		h.logger.Warnf("find aggregate caches: %v", err)
+	} else {
+		for _, result := range results {
+			if result.Count() <= 1 {
+				continue
+			}
+			result.Sort("CreatedAt")
+			caches = caches[:0]
+			result.Reduction(&caches)
+			for _, cache := range caches[:len(caches)-1] {
+				if time.Since(time.Unix(cache.UsedAt, 0)) < keepOld {
+					// Keep it since it has been used recently, even if it's old.
+					// Or it could break downloading in process.
+					continue
+				}
+				h.storage.Remove(cache.ID)
+				if err := db.Delete(cache.ID, cache); err != nil {
+					h.logger.Warnf("delete cache: %v", err)
+					continue
+				}
+				h.logger.Infof("deleted cache: %+v", cache)
+			}
+		}
+	}
+}
+
+func (h *Handler) responseJSON(w http.ResponseWriter, r *http.Request, code int, v ...any) {
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	var data []byte
+	if len(v) == 0 || v[0] == nil {
+		data, _ = json.Marshal(struct{}{})
+	} else if err, ok := v[0].(error); ok {
+		h.logger.Errorf("%v %v: %v", r.Method, r.URL.Path, err)
+		data, _ = json.Marshal(map[string]any{
+			"error": err.Error(),
+		})
+	} else {
+		data, _ = json.Marshal(v[0])
+	}
+	w.WriteHeader(code)
+	_, _ = w.Write(data)
+}
+
+func parseContentRange(s string) (int64, int64, error) {
+	// support the format like "bytes 11-22/*" only
+	s, _, _ = strings.Cut(strings.TrimPrefix(s, "bytes "), "/")
+	s1, s2, _ := strings.Cut(s, "-")
+
+	start, err := strconv.ParseInt(s1, 10, 64)
+	if err != nil {
+		return 0, 0, fmt.Errorf("parse %q: %w", s, err)
+	}
+	stop, err := strconv.ParseInt(s2, 10, 64)
+	if err != nil {
+		return 0, 0, fmt.Errorf("parse %q: %w", s, err)
+	}
+	return start, stop, nil
+}

internal/act/artifactcache/handler_v2.go

@@ -0,0 +1,273 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package artifactcache
+
+import (
+	"cmp"
+	"encoding/json"
+	"encoding/xml"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/julienschmidt/httprouter"
+)
+
+// The cache service v2 API. A client on this version talks twirp to
+// `github.actions.results.api.v1.CacheService` instead of the /_apis/artifactcache
+// endpoints, and uploads the archive to the returned URL with the Azure blob protocol.
+// Both API versions are served from the same store, so a repository keeps its cache
+// when a workflow moves between action versions.
+//
+// Responses carry the proto field names, which is what Gitea's own results API emits and the only
+// spelling the Go clients parse. The JavaScript toolkit accepts either.
+const (
+	cacheServiceV2Path = "/twirp/github.actions.results.api.v1.CacheService"
+
+	// blobPath authenticates by signature, because the client uploads without an
+	// Authorization header. Downloads are handed the v1 artifact URL instead.
+	blobPath = apiPath + "/blobs"
+
+	// blobUploadPurpose keeps an upload URL from being replayed to read an entry.
+	blobUploadPurpose = "upload:"
+
+	blobUploadURLTTL = time.Hour
+
+	// twirpInternal is the only error code that is not the client's fault.
+	twirpInternal = "internal"
+)
+
+func (h *Handler) registerV2Routes(router *httprouter.Router) {
+	router.POST(cacheServiceV2Path+"/CreateCacheEntry", h.bearerAuth(h.v2CreateCacheEntry))
+	router.POST(cacheServiceV2Path+"/FinalizeCacheEntryUpload", h.bearerAuth(h.v2FinalizeCacheEntryUpload))
+	router.POST(cacheServiceV2Path+"/GetCacheEntryDownloadURL", h.bearerAuth(h.v2GetCacheEntryDownloadURL))
+	router.PUT(blobPath+"/:id", h.signedAuth(blobUploadPurpose, h.v2UploadBlob))
+}
+
+// An entry that already exists is reported as not ok, which is how the client learns to skip
+// the upload.
+func (h *Handler) v2CreateCacheEntry(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
+	cred := credFromContext(r.Context())
+	req, err := decodeTwirpRequest[v2CreateRequest](r)
+	if err != nil {
+		h.twirpError(w, r, "malformed_request", err)
+		return
+	}
+	if req.Key == "" || req.Version == "" {
+		h.twirpError(w, r, "invalid_argument", errors.New("key and version are required"))
+		return
+	}
+
+	db, err := h.openDB()
+	if err != nil {
+		h.twirpError(w, r, twirpInternal, err)
+		return
+	}
+	defer db.Close()
+
+	// An exact (key, version) match means the entry is already cached; the client then skips
+	// the upload. A prefix match must not count here, or a shorter key would be reported as
+	// existing and silently never saved.
+	if existing, err := findExactCache(db, cred.Repo, req.Key, req.Version, true); err != nil {
+		h.twirpError(w, r, twirpInternal, err)
+		return
+	} else if existing != nil {
+		h.twirpNotOK(w, r)
+		return
+	}
+
+	now := time.Now().Unix()
+	cache := &Cache{
+		Repo:      cred.Repo,
+		Key:       req.Key,
+		Version:   req.Version,
+		Size:      -1, // the size is only known at finalize time
+		CreatedAt: now,
+		UsedAt:    now,
+	}
+	if err := insertCache(db, cache); err != nil {
+		h.twirpError(w, r, twirpInternal, err)
+		return
+	}
+
+	h.responseJSON(w, r, http.StatusOK, map[string]any{
+		"ok":                true,
+		"signed_upload_url": h.signedURL(blobPath, blobUploadPurpose, cache.ID, time.Now().Add(blobUploadURLTTL)),
+	})
+}
+
+func (h *Handler) v2FinalizeCacheEntryUpload(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
+	cred := credFromContext(r.Context())
+	req, err := decodeTwirpRequest[v2FinalizeRequest](r)
+	if err != nil {
+		h.twirpError(w, r, "malformed_request", err)
+		return
+	}
+
+	db, err := h.openDB()
+	if err != nil {
+		h.twirpError(w, r, twirpInternal, err)
+		return
+	}
+	defer db.Close()
+
+	cache, err := findExactCache(db, cred.Repo, req.Key, req.Version, false)
+	if err != nil {
+		h.twirpError(w, r, twirpInternal, err)
+		return
+	}
+	if cache == nil {
+		h.twirpNotOK(w, r)
+		return
+	}
+	db.Close() // commitCache needs the store closed
+
+	cache.Size, _ = cmp.Or(req.SizeBytes, req.SizeBytesCamel).Int64()
+	if err := h.commitCache(cache); err != nil {
+		h.logger.Errorf("finalize cache %d (%s): %v", cache.ID, cache.Key, err)
+		h.twirpNotOK(w, r)
+		return
+	}
+
+	h.responseJSON(w, r, http.StatusOK, map[string]any{
+		"ok": true,
+		// int64 fields travel as strings in the proto JSON mapping.
+		"entry_id": strconv.FormatUint(cache.ID, 10),
+	})
+}
+
+func (h *Handler) v2GetCacheEntryDownloadURL(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
+	cred := credFromContext(r.Context())
+	req, err := decodeTwirpRequest[v2DownloadRequest](r)
+	if err != nil {
+		h.twirpError(w, r, "malformed_request", err)
+		return
+	}
+
+	db, err := h.openDB()
+	if err != nil {
+		h.twirpError(w, r, twirpInternal, err)
+		return
+	}
+	defer db.Close()
+
+	cache, err := h.lookupCache(db, cred.Repo, req.keys(), req.Version)
+	if err != nil {
+		h.twirpError(w, r, twirpInternal, err)
+		return
+	}
+	if cache == nil {
+		h.twirpNotOK(w, r)
+		return
+	}
+
+	h.responseJSON(w, r, http.StatusOK, map[string]any{
+		"ok":                  true,
+		"signed_download_url": h.signedArtifactURL(cache.ID, time.Now().Add(artifactURLTTL)),
+		"matched_key":         cache.Key,
+	})
+}
+
+// The archive arrives over the subset of the Azure blob API the toolkit uses: a small
+// cache is a single PUT, a large one is staged as blocks that a final block list puts
+// in order.
+func (h *Handler) v2UploadBlob(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
+	id, err := strconv.ParseUint(params.ByName("id"), 10, 64)
+	if err != nil {
+		h.responseJSON(w, r, http.StatusBadRequest, err)
+		return
+	}
+
+	if err := h.touchCache(id, true); err != nil {
+		h.responseJSON(w, r, http.StatusBadRequest, err)
+		return
+	}
+
+	query := r.URL.Query()
+	switch strings.ToLower(query.Get("comp")) {
+	case "block":
+		blockID := query.Get("blockid")
+		if blockID == "" {
+			h.responseJSON(w, r, http.StatusBadRequest, errors.New("missing blockid"))
+			return
+		}
+		err = h.storage.WriteBlock(id, blockID, r.Body)
+	case "blocklist":
+		var list struct{ Latest []string }
+		if err := xml.NewDecoder(io.LimitReader(r.Body, 8<<20)).Decode(&list); err != nil {
+			h.responseJSON(w, r, http.StatusBadRequest, fmt.Errorf("malformed block list: %w", err))
+			return
+		}
+		err = h.storage.OrderBlocks(id, list.Latest)
+	default:
+		err = h.storage.Write(id, 0, r.Body)
+	}
+	if err != nil {
+		h.responseJSON(w, r, http.StatusInternalServerError, err)
+		return
+	}
+
+	// The Azure SDK client dereferences this without checking, so its absence panics the caller.
+	w.Header().Set("x-ms-request-id", strconv.FormatInt(time.Now().UnixNano(), 10))
+	w.WriteHeader(http.StatusCreated)
+}
+
+// twirpNotOK is the negative answer all three endpoints share: no such entry to restore, no
+// reservation to finalize, or an entry that already exists and need not be uploaded again.
+func (h *Handler) twirpNotOK(w http.ResponseWriter, r *http.Request) {
+	h.responseJSON(w, r, http.StatusOK, map[string]any{"ok": false})
+}
+
+// twirpError reports in the shape a twirp client expects, so the toolkit surfaces the message
+// instead of a parse error.
+func (h *Handler) twirpError(w http.ResponseWriter, r *http.Request, code string, err error) {
+	h.logger.Debugf("%s %s: %v", r.Method, r.URL.Path, err)
+	status := http.StatusBadRequest
+	if code == twirpInternal {
+		status = http.StatusInternalServerError
+	}
+	h.responseJSON(w, r, status, map[string]any{"code": code, "msg": err.Error()})
+}
+
+// The twirp request bodies. The toolkit's client serialises with useProtoFieldName, so the proto
+// names are what arrive; the camelCase spellings of the same mapping are accepted too, as are
+// int64s sent as a bare number rather than the string the mapping prescribes.
+type (
+	v2CreateRequest struct {
+		Key     string `json:"key"`
+		Version string `json:"version"`
+	}
+
+	v2FinalizeRequest struct {
+		Key            string      `json:"key"`
+		Version        string      `json:"version"`
+		SizeBytes      json.Number `json:"size_bytes"`
+		SizeBytesCamel json.Number `json:"sizeBytes"`
+	}
+
+	v2DownloadRequest struct {
+		Key              string   `json:"key"`
+		Version          string   `json:"version"`
+		RestoreKeys      []string `json:"restore_keys"`
+		RestoreKeysCamel []string `json:"restoreKeys"`
+	}
+)
+
+func (d v2DownloadRequest) keys() []string {
+	restoreKeys := d.RestoreKeys
+	if len(restoreKeys) == 0 {
+		restoreKeys = d.RestoreKeysCamel
+	}
+	return append([]string{d.Key}, restoreKeys...)
+}
+
+func decodeTwirpRequest[T any](r *http.Request) (T, error) {
+	var req T
+	err := json.NewDecoder(io.LimitReader(r.Body, 1<<20)).Decode(&req)
+	return req, err
+}

internal/act/artifactcache/handler_v2_test.go

@@ -0,0 +1,241 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package artifactcache
+
+import (
+	"bytes"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"path/filepath"
+	"strconv"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// v2Call posts a twirp request to the cache service and returns the decoded response.
+// Field names are the proto ones, which is what the toolkit's client sends.
+func v2Call(t *testing.T, handler *Handler, client *http.Client, method string, request any) map[string]any {
+	t.Helper()
+
+	body, err := json.Marshal(request)
+	require.NoError(t, err)
+
+	resp, err := client.Post(handler.ExternalURL()+cacheServiceV2Path+"/"+method, "application/json", bytes.NewReader(body))
+	require.NoError(t, err)
+	defer resp.Body.Close()
+	require.Equal(t, http.StatusOK, resp.StatusCode)
+
+	got := map[string]any{}
+	require.NoError(t, json.NewDecoder(resp.Body).Decode(&got))
+	return got
+}
+
+// putBlob uploads to a signed URL and returns the status, so a test can assert a refusal.
+func putBlob(t *testing.T, url string, content []byte) int {
+	t.Helper()
+
+	req, err := http.NewRequestWithContext(t.Context(), http.MethodPut, url, bytes.NewReader(content))
+	require.NoError(t, err)
+	resp, err := http.DefaultClient.Do(req)
+	require.NoError(t, err)
+	defer resp.Body.Close()
+	if resp.StatusCode == http.StatusCreated {
+		// The Azure SDK client dereferences this header without checking, so a blob upload that
+		// omits it panics the caller rather than failing it.
+		require.NotEmpty(t, resp.Header.Get("x-ms-request-id"))
+	}
+	return resp.StatusCode
+}
+
+func getURL(t *testing.T, url string) []byte {
+	t.Helper()
+
+	req, err := http.NewRequestWithContext(t.Context(), http.MethodGet, url, nil)
+	require.NoError(t, err)
+	resp, err := http.DefaultClient.Do(req)
+	require.NoError(t, err)
+	defer resp.Body.Close()
+	body, err := io.ReadAll(resp.Body)
+	require.NoError(t, err)
+	return body
+}
+
+func startTestHandler(t *testing.T) *Handler {
+	t.Helper()
+
+	handler, err := StartHandler(filepath.Join(t.TempDir(), "artifactcache"), "127.0.0.1", 0, "", nil)
+	require.NoError(t, err)
+	t.Cleanup(func() { _ = handler.Close() })
+	handler.RegisterJob(testToken, JobCredential{Repo: testRepo})
+	return handler
+}
+
+// saveV2 runs the reserve/upload/finalize sequence and returns the finalize response along
+// with the upload URL it used.
+func saveV2(t *testing.T, handler *Handler, key, version string, content []byte) (finalized map[string]any, uploadURL string) {
+	t.Helper()
+
+	created := v2Call(t, handler, testClient, "CreateCacheEntry", map[string]any{"key": key, "version": version})
+	require.Equal(t, true, created["ok"])
+	uploadURL, _ = created["signed_upload_url"].(string)
+	require.NotEmpty(t, uploadURL)
+	require.Equal(t, http.StatusCreated, putBlob(t, uploadURL, content))
+
+	return v2Call(t, handler, testClient, "FinalizeCacheEntryUpload", map[string]any{
+		"key": key, "version": version,
+		"size_bytes": strconv.Itoa(len(content)),
+	}), uploadURL
+}
+
+// The whole round trip an actions/cache v2 client makes, plus the guarantees on the signed
+// URLs it is handed: unsigned requests are refused, an upload URL cannot be replayed to read
+// or to replace a finalized entry.
+func TestCacheServiceV2RoundTrip(t *testing.T) {
+	handler := startTestHandler(t)
+	content := []byte("the cached archive")
+
+	unsigned := fmt.Sprintf("%s%s/1", handler.ExternalURL(), blobPath)
+	assert.Equal(t, http.StatusUnauthorized, putBlob(t, unsigned, content))
+
+	finalized, uploadURL := saveV2(t, handler, "deps-v1", "abc123", content)
+	require.Equal(t, true, finalized["ok"])
+	assert.NotEmpty(t, finalized["entry_id"])
+
+	// The upload URL outlives the finalize call, so replaying it must not poison the entry,
+	// and it is an upload URL only: nothing reads a blob back through it.
+	assert.Equal(t, http.StatusBadRequest, putBlob(t, uploadURL, []byte("poisoned")))
+	resp, err := http.Get(uploadURL) //nolint:noctx // the URL is the server under test
+	require.NoError(t, err)
+	defer resp.Body.Close()
+	assert.Equal(t, http.StatusMethodNotAllowed, resp.StatusCode)
+
+	got := v2Call(t, handler, testClient, "GetCacheEntryDownloadURL", map[string]any{"key": "deps-v1", "version": "abc123"})
+	require.Equal(t, true, got["ok"])
+	assert.Equal(t, "deps-v1", got["matched_key"])
+	downloadURL, _ := got["signed_download_url"].(string)
+	require.NotEmpty(t, downloadURL)
+	assert.Equal(t, content, getURL(t, downloadURL))
+}
+
+// A large archive is staged as blocks and only put in order by the final block list, so
+// blocks that arrive out of order must still be assembled the way the client asked.
+func TestCacheServiceV2BlockUpload(t *testing.T) {
+	handler := startTestHandler(t)
+
+	created := v2Call(t, handler, testClient, "CreateCacheEntry", map[string]any{"key": "blocks", "version": "v1"})
+	uploadURL, _ := created["signed_upload_url"].(string)
+	require.NotEmpty(t, uploadURL)
+
+	blocks := map[string][]byte{}
+	var order []string
+	for i, part := range []string{"hello ", "world", "!"} {
+		blockID := base64.StdEncoding.EncodeToString(fmt.Appendf(nil, "block-%d", i))
+		blocks[blockID] = []byte(part)
+		order = append(order, blockID)
+	}
+	// Upload in an order that is not the block list order.
+	for _, blockID := range []string{order[2], order[0], order[1]} {
+		require.Equal(t, http.StatusCreated, putBlob(t, uploadURL+"&comp=block&blockid="+blockID, blocks[blockID]))
+	}
+
+	var list bytes.Buffer
+	list.WriteString(`<?xml version="1.0" encoding="utf-8"?><BlockList>`)
+	for _, blockID := range order {
+		fmt.Fprintf(&list, "<Latest>%s</Latest>", blockID)
+	}
+	list.WriteString(`</BlockList>`)
+	require.Equal(t, http.StatusCreated, putBlob(t, uploadURL+"&comp=blocklist", list.Bytes()))
+
+	finalized := v2Call(t, handler, testClient, "FinalizeCacheEntryUpload", map[string]any{
+		"key": "blocks", "version": "v1", "size_bytes": len("hello world!"),
+	})
+	require.Equal(t, true, finalized["ok"])
+
+	got := v2Call(t, handler, testClient, "GetCacheEntryDownloadURL", map[string]any{"key": "blocks", "version": "v1"})
+	require.Equal(t, true, got["ok"])
+	assert.Equal(t, "hello world!", string(getURL(t, got["signed_download_url"].(string))))
+}
+
+func TestCacheServiceV2Lookups(t *testing.T) {
+	handler := startTestHandler(t)
+	saved, _ := saveV2(t, handler, "deps-abc", "v1", []byte("x"))
+	require.Equal(t, true, saved["ok"])
+
+	t.Run("reports a miss for an unknown key", func(t *testing.T) {
+		got := v2Call(t, handler, testClient, "GetCacheEntryDownloadURL", map[string]any{"key": "nothing", "version": "v1"})
+		assert.Equal(t, false, got["ok"])
+	})
+
+	// The toolkit serialises with the proto field names; the camelCase spellings of the same
+	// proto JSON mapping are accepted alongside them.
+	for _, field := range []string{"restore_keys", "restoreKeys"} {
+		t.Run("restore keys match by prefix, spelled "+field, func(t *testing.T) {
+			got := v2Call(t, handler, testClient, "GetCacheEntryDownloadURL", map[string]any{
+				"key": "deps-zzz", field: []string{"deps-"}, "version": "v1",
+			})
+			require.Equal(t, true, got["ok"])
+			assert.Equal(t, "deps-abc", got["matched_key"])
+		})
+	}
+
+	t.Run("an existing entry is not reserved twice", func(t *testing.T) {
+		again := v2Call(t, handler, testClient, "CreateCacheEntry", map[string]any{"key": "deps-abc", "version": "v1"})
+		assert.Equal(t, false, again["ok"])
+	})
+
+	// A key that is only a prefix of an existing one is a different entry, so the
+	// reservation check must be exact and not a restore-key prefix match, or the shorter
+	// key would be reported as existing and silently never saved.
+	t.Run("a prefix of an existing key is still reserved", func(t *testing.T) {
+		reserved := v2Call(t, handler, testClient, "CreateCacheEntry", map[string]any{"key": "deps", "version": "v1"})
+		require.Equal(t, true, reserved["ok"])
+		assert.NotEmpty(t, reserved["signed_upload_url"])
+	})
+
+	t.Run("finalizing without a reservation is not ok", func(t *testing.T) {
+		got := v2Call(t, handler, testClient, "FinalizeCacheEntryUpload", map[string]any{
+			"key": "never-reserved", "version": "v1", "size_bytes": 1,
+		})
+		assert.Equal(t, false, got["ok"])
+	})
+
+	// The size the client declares is what Commit validates the assembled archive against.
+	t.Run("finalizing with the wrong size is not ok", func(t *testing.T) {
+		created := v2Call(t, handler, testClient, "CreateCacheEntry", map[string]any{"key": "wrong-size", "version": "v1"})
+		require.Equal(t, http.StatusCreated, putBlob(t, created["signed_upload_url"].(string), []byte("four")))
+
+		got := v2Call(t, handler, testClient, "FinalizeCacheEntryUpload", map[string]any{
+			"key": "wrong-size", "version": "v1", "size_bytes": 99,
+		})
+		assert.Equal(t, false, got["ok"])
+	})
+
+	// Both API versions are served from one store, so an entry written through v2 is a hit for
+	// a v1 client asking for the same key and version.
+	t.Run("a v1 client sees an entry written through v2", func(t *testing.T) {
+		resp, err := testClient.Get(fmt.Sprintf("%s%s/cache?keys=deps-abc&version=v1", handler.ExternalURL(), apiPath))
+		require.NoError(t, err)
+		defer resp.Body.Close()
+		require.Equal(t, http.StatusOK, resp.StatusCode)
+
+		got := map[string]any{}
+		require.NoError(t, json.NewDecoder(resp.Body).Decode(&got))
+		assert.Equal(t, "deps-abc", got["cacheKey"])
+		assert.NotEmpty(t, got["archiveLocation"])
+	})
+
+	// The cache of one repository must stay invisible to another, as it does for the v1 API.
+	t.Run("another repository sees nothing", func(t *testing.T) {
+		handler.RegisterJob("other-runtime-token", JobCredential{Repo: "other/repo"})
+		otherClient := &http.Client{Transport: &bearerTransport{token: "other-runtime-token"}}
+
+		got := v2Call(t, handler, otherClient, "GetCacheEntryDownloadURL", map[string]any{"key": "deps-abc", "version": "v1"})
+		assert.Equal(t, false, got["ok"])
+	})
+}

internal/act/artifactcache/model.go

@@ -0,0 +1,39 @@
+// 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"`
+}

internal/act/artifactcache/results.go

@@ -0,0 +1,59 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package artifactcache
+
+import (
+	"crypto/tls"
+	"net/http"
+	"net/http/httputil"
+	"net/url"
+	"strings"
+)
+
+// The results service is one origin serving every github.actions.results.api.v1 service, and
+// Gitea implements only the artifact half of it. Forwarding that half from here makes this origin
+// the whole service, so ACTIONS_RESULTS_URL can point at it truthfully, which is what the clients
+// this runner cannot patch need, docker buildx among them.
+//
+// The instance to forward to travels with the job registration rather than with configuration, so
+// a cache server shared between runners serves each of their instances.
+const artifactServicePath = "/twirp/github.actions.results.api.v1.ArtifactService/"
+
+// forwardOrNotFound is the router's fallback: the artifact service of the instance the job
+// registered with, and the 404 the router would have written otherwise.
+func (h *Handler) forwardOrNotFound(w http.ResponseWriter, r *http.Request) {
+	cred, ok := h.lookupCredential(bearerToken(r))
+	if !ok || cred.Results == "" || !strings.HasPrefix(r.URL.Path, artifactServicePath) {
+		http.NotFound(w, r)
+		return
+	}
+	target, err := url.Parse(strings.TrimSuffix(cred.Results, "/"))
+	if err != nil {
+		h.logger.Errorf("artifact service forward to %q: %v", cred.Results, err)
+		w.WriteHeader(http.StatusBadGateway)
+		return
+	}
+	h.logger.Debugf("%s %s: forwarding to %s", r.Method, r.URL.Path, target)
+
+	proxy := &httputil.ReverseProxy{
+		Rewrite: func(r *httputil.ProxyRequest) {
+			r.SetURL(target)
+			// Gitea builds the URLs it hands back from this Host, and their scheme from the
+			// connection unless a forwarded header overrides it, so artifact bodies go to Gitea
+			// directly and never through here.
+			r.Out.Host = target.Host
+		},
+		ErrorHandler: func(w http.ResponseWriter, _ *http.Request, err error) {
+			h.logger.Warnf("artifact service forward to %s: %v", target, err)
+			w.WriteHeader(http.StatusBadGateway)
+		},
+	}
+	if cred.InsecureTLS {
+		proxy.Transport = insecureTransport
+	}
+	proxy.ServeHTTP(w, r)
+}
+
+// insecureTransport is shared, because a transport per request would pool no connections.
+var insecureTransport = &http.Transport{TLSClientConfig: &tls.Config{InsecureSkipVerify: true}} //nolint:gosec // the runner reaches its instance on the operator's say-so

internal/act/artifactcache/results_test.go

@@ -0,0 +1,56 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package artifactcache
+
+import (
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// The artifact half is forwarded under the Host Gitea knows itself by, so the URLs it hands back
+// still point at Gitea, and nothing else is proxied.
+func TestFrontResultsService(t *testing.T) {
+	var gotHost, gotPath, gotProto string
+	gitea := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		gotHost, gotPath, gotProto = r.Host, r.URL.Path, r.Header.Get("X-Forwarded-Proto")
+		_, _ = io.WriteString(w, `{"ok":true}`)
+	}))
+	defer gitea.Close()
+
+	handler, err := StartHandler(t.TempDir(), "127.0.0.1", 0, "", nil)
+	require.NoError(t, err)
+	defer handler.Close()
+	const token = "forward-token"
+
+	client := &http.Client{Transport: &bearerTransport{token: token}}
+	post := func(path string) int {
+		req, err := http.NewRequestWithContext(t.Context(), http.MethodPost, handler.ExternalURL()+path, nil)
+		require.NoError(t, err)
+		resp, err := client.Do(req)
+		require.NoError(t, err)
+		resp.Body.Close()
+		return resp.StatusCode
+	}
+
+	assert.Equal(t, http.StatusNotFound, post(artifactServicePath+"CreateArtifact"),
+		"an unregistered token is forwarded nowhere")
+
+	defer handler.RegisterJob(token, JobCredential{Repo: "owner/repo", Results: gitea.URL})()
+
+	assert.Equal(t, http.StatusOK, post(artifactServicePath+"CreateArtifact"))
+	assert.Equal(t, strings.TrimPrefix(gitea.URL, "http://"), gotHost, "Gitea must see the host it mints its URLs from")
+	assert.Empty(t, gotProto, "a forwarded scheme would make an https Gitea mint http URLs")
+	assert.Equal(t, artifactServicePath+"CreateArtifact", gotPath)
+
+	gotPath = ""
+	assert.Equal(t, http.StatusNotFound, post("/twirp/github.actions.results.api.v1.OtherService/Do"))
+	assert.Equal(t, http.StatusNotFound, post("/api/v1/repos/owner/repo"))
+	assert.Empty(t, gotPath, "only the artifact service is forwarded")
+}

internal/act/artifactcache/storage.go

@@ -0,0 +1,187 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// Copyright 2023 The nektos/act Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package artifactcache
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+type Storage struct {
+	rootDir string
+}
+
+func NewStorage(rootDir string) (*Storage, error) {
+	if err := os.MkdirAll(rootDir, 0o755); err != nil {
+		return nil, err
+	}
+	return &Storage{
+		rootDir: rootDir,
+	}, nil
+}
+
+func (s *Storage) Exist(id uint64) (bool, error) {
+	name := s.filename(id)
+	if _, err := os.Stat(name); os.IsNotExist(err) {
+		return false, nil
+	} else if err != nil {
+		return false, err
+	}
+	return true, nil
+}
+
+func (s *Storage) Write(id uint64, offset int64, reader io.Reader) error {
+	return s.writeFile(s.tempName(id, offset), reader)
+}
+
+func (s *Storage) writeFile(name string, reader io.Reader) error {
+	if err := os.MkdirAll(filepath.Dir(name), 0o755); err != nil {
+		return err
+	}
+	file, err := os.Create(name)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	_, err = io.Copy(file, reader)
+	return err
+}
+
+func (s *Storage) WriteBlock(id uint64, blockID string, reader io.Reader) error {
+	return s.writeFile(s.blockName(id, blockID), reader)
+}
+
+// OrderBlocks renames the staged blocks into the order the block list gives. A block the list
+// does not name keeps its staged name, which is how Commit leaves it out, as Azure drops it. One
+// rename pass is safe because a staged name always carries blockFilePrefix and a target name
+// never does, so no rename can collide with a block not yet moved.
+func (s *Storage) OrderBlocks(id uint64, blockIDs []string) error {
+	for i, blockID := range blockIDs {
+		if err := os.Rename(s.blockName(id, blockID), s.tempName(id, int64(i))); err != nil {
+			if os.IsNotExist(err) {
+				return fmt.Errorf("block %q of cache %d was never uploaded: %w", blockID, id, err)
+			}
+			return err
+		}
+	}
+	return nil
+}
+
+func (s *Storage) Commit(id uint64, size int64) (int64, error) {
+	defer func() {
+		_ = os.RemoveAll(s.tempDir(id))
+	}()
+
+	name := s.filename(id)
+	tempNames, err := s.tempNames(id)
+	if err != nil {
+		return 0, err
+	}
+
+	if err := os.MkdirAll(filepath.Dir(name), 0o755); err != nil {
+		return 0, err
+	}
+	written, err := assemble(name, tempNames)
+	if err != nil {
+		return 0, err
+	}
+	// If size is less than 0, it means the size is unknown.
+	// We can't check the size of the file, just skip the check.
+	// It happens when the request comes from old versions of actions, like `actions/cache@v2`.
+	if size >= 0 && written != size {
+		_ = os.Remove(name)
+		return 0, fmt.Errorf("broken file: %v != %v", written, size)
+	}
+	return written, nil
+}
+
+// assemble concatenates the uploaded parts into name. A single part, which is what the v2 API
+// produces below the client's block threshold, is already the whole archive and is moved.
+func assemble(name string, tempNames []string) (int64, error) {
+	if len(tempNames) == 1 {
+		info, err := os.Stat(tempNames[0])
+		if err != nil {
+			return 0, err
+		}
+		return info.Size(), os.Rename(tempNames[0], name)
+	}
+
+	file, err := os.Create(name)
+	if err != nil {
+		return 0, err
+	}
+	defer file.Close()
+
+	var written int64
+	for _, v := range tempNames {
+		f, err := os.Open(v)
+		if err != nil {
+			return 0, err
+		}
+		n, err := io.Copy(file, f)
+		_ = f.Close()
+		if err != nil {
+			return 0, err
+		}
+		written += n
+	}
+	return written, nil
+}
+
+func (s *Storage) Serve(w http.ResponseWriter, r *http.Request, id uint64) {
+	name := s.filename(id)
+	http.ServeFile(w, r, name)
+}
+
+func (s *Storage) Remove(id uint64) {
+	_ = os.Remove(s.filename(id))
+	_ = os.RemoveAll(s.tempDir(id))
+}
+
+func (s *Storage) filename(id uint64) string {
+	return filepath.Join(s.rootDir, fmt.Sprintf("%02x", id%0xff), strconv.FormatUint(id, 10))
+}
+
+func (s *Storage) tempDir(id uint64) string {
+	return filepath.Join(s.rootDir, "tmp", strconv.FormatUint(id, 10))
+}
+
+func (s *Storage) tempName(id uint64, offset int64) string {
+	return filepath.Join(s.tempDir(id), fmt.Sprintf("%016x", offset))
+}
+
+// blockFilePrefix marks a staged, not yet ordered block, so that tempNames can keep it out of
+// Commit's name-ordered concatenation.
+const blockFilePrefix = "block-"
+
+func (s *Storage) blockName(id uint64, blockID string) string {
+	// The block id is client-chosen (base64), so it is hashed rather than trusted as a
+	// path element.
+	sum := sha256.Sum256([]byte(blockID))
+	return filepath.Join(s.tempDir(id), blockFilePrefix+hex.EncodeToString(sum[:]))
+}
+
+func (s *Storage) tempNames(id uint64) ([]string, error) {
+	dir := s.tempDir(id)
+	files, err := os.ReadDir(dir)
+	if err != nil {
+		return nil, err
+	}
+	var names []string
+	for _, v := range files {
+		if !v.IsDir() && !strings.HasPrefix(v.Name(), blockFilePrefix) {
+			names = append(names, filepath.Join(dir, v.Name()))
+		}
+	}
+	return names, nil
+}