Merge pull request from GHSA-55r9-5mx9-qq7r

when a client pushes an image zot's inline dedupe
will try to find the blob path corresponding with the blob digest
that it's currently pushed and if it's found in the cache
then zot will make a symbolic link to that cache entry and report
to the client that the blob already exists on the location.

Before this patch authorization was not applied on this process meaning
that a user could copy blobs without having permissions on the source repo.

Added a rule which says that the client should have read permissions on the source repo
before deduping, otherwise just Stat() the blob and return the corresponding status code.

Signed-off-by: Petu Eusebiu <peusebiu@cisco.com>
Co-authored-by: Petu Eusebiu <peusebiu@cisco.com>

pkg/api/routes.go

@@ -873,6 +873,37 @@ func (rh *RouteHandler) DeleteManifest(response http.ResponseWriter, request *ht
 	response.WriteHeader(http.StatusAccepted)
 }
 
+// canMount checks if a user has read permission on cached blobs with this specific digest.
+// returns true if the user have permission to copy blob from cache.
+func canMount(userAc *reqCtx.UserAccessControl, imgStore storageTypes.ImageStore, digest godigest.Digest,
+) (bool, error) {
+	canMount := true
+
+	// authz enabled
+	if userAc != nil {
+		canMount = false
+
+		repos, err := imgStore.GetAllDedupeReposCandidates(digest)
+		if err != nil {
+			// first write
+			return false, err
+		}
+
+		if len(repos) == 0 {
+			canMount = false
+		}
+
+		// check if user can read any repo which contain this blob
+		for _, repo := range repos {
+			if userAc.Can(constants.ReadPermission, repo) {
+				canMount = true
+			}
+		}
+	}
+
+	return canMount, nil
+}
+
 // CheckBlob godoc
 // @Summary Check image blob/layer
 // @Description Check an image's blob/layer given a digest
@@ -905,7 +936,31 @@ func (rh *RouteHandler) CheckBlob(response http.ResponseWriter, request *http.Re
 
 	digest := godigest.Digest(digestStr)
 
-	ok, blen, err := imgStore.CheckBlob(name, digest)
+	userAc, err := reqCtx.UserAcFromContext(request.Context())
+	if err != nil {
+		response.WriteHeader(http.StatusInternalServerError)
+
+		return
+	}
+
+	userCanMount, err := canMount(userAc, imgStore, digest)
+	if err != nil {
+		rh.c.Log.Error().Err(err).Msg("unexpected error")
+	}
+
+	var blen int64
+
+	if userCanMount {
+		ok, blen, err = imgStore.CheckBlob(name, digest)
+	} else {
+		var lockLatency time.Time
+
+		imgStore.RLock(&lockLatency)
+		defer imgStore.RUnlock(&lockLatency)
+
+		ok, blen, _, err = imgStore.StatBlob(name, digest)
+	}
+
 	if err != nil {
 		details := zerr.GetDetails(err)
 		if errors.Is(err, zerr.ErrBadBlobDigest) { //nolint:gocritic // errorslint conflicts with gocritic:IfElseChain
@@ -1191,11 +1246,27 @@ func (rh *RouteHandler) CreateBlobUpload(response http.ResponseWriter, request *
 		}
 
 		mountDigest := godigest.Digest(mountDigests[0])
+
+		userAc, err := reqCtx.UserAcFromContext(request.Context())
+		if err != nil {
+			response.WriteHeader(http.StatusInternalServerError)
+
+			return
+		}
+
+		userCanMount, err := canMount(userAc, imgStore, mountDigest)
+		if err != nil {
+			rh.c.Log.Error().Err(err).Msg("unexpected error")
+		}
+
 		// zot does not support cross mounting directly and do a workaround creating using hard link.
 		// check blob looks for actual path (name+mountDigests[0]) first then look for cache and
 		// if found in cache, will do hard link and if fails we will start new upload.
-		_, _, err := imgStore.CheckBlob(name, mountDigest)
-		if err != nil {
+		if userCanMount {
+			_, _, err = imgStore.CheckBlob(name, mountDigest)
+		}
+
+		if err != nil || !userCanMount {
 			upload, err := imgStore.NewBlobUpload(name)
 			if err != nil {
 				details := zerr.GetDetails(err)