knotserver/git: reject requests to unknown repos

Signed-off-by: Seongmin Lee <[e-mail]>

knotserver/git.go

···
 	"fmt"
 	"io"
 	"net/http"
-	"path/filepath"
+	"os"
 	"strings"
 
-	securejoin "github.com/cyphar/filepath-securejoin"
 	"github.com/go-chi/chi/v5"
 	"tangled.org/core/knotserver/git/service"
 )
 
 func (h *Knot) InfoRefs(w http.ResponseWriter, r *http.Request) {
-	did := chi.URLParam(r, "did")
 	name := chi.URLParam(r, "name")
-	repoName, err := securejoin.SecureJoin(did, name)
-	if err != nil {
-		gitError(w, "repository not found", http.StatusNotFound)
-		h.l.Error("git: failed to secure join repo path", "handler", "InfoRefs", "error", err)
-		return
-	}
-
-	repoPath, err := securejoin.SecureJoin(h.c.Repo.ScanPath, repoName)
-	if err != nil {
-		gitError(w, "repository not found", http.StatusNotFound)
-		h.l.Error("git: failed to secure join repo path", "handler", "InfoRefs", "error", err)
+	repoPath, ok := repoPathFromcontext(r.Context())
+	if !ok {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte("Failed to find repository path"))
 		return
 	}
 
···
 }
 
 func (h *Knot) UploadArchive(w http.ResponseWriter, r *http.Request) {
-	did := chi.URLParam(r, "did")
-	name := chi.URLParam(r, "name")
-	repo, err := securejoin.SecureJoin(h.c.Repo.ScanPath, filepath.Join(did, name))
-	if err != nil {
-		gitError(w, err.Error(), http.StatusInternalServerError)
-		h.l.Error("git: failed to secure join repo path", "handler", "UploadPack", "error", err)
+	repo, ok := repoPathFromcontext(r.Context())
+	if !ok {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte("Failed to find repository path"))
 		return
 	}
 
···
 }
 
 func (h *Knot) UploadPack(w http.ResponseWriter, r *http.Request) {
-	did := chi.URLParam(r, "did")
-	name := chi.URLParam(r, "name")
-	repo, err := securejoin.SecureJoin(h.c.Repo.ScanPath, filepath.Join(did, name))
-	if err != nil {
-		gitError(w, err.Error(), http.StatusInternalServerError)
-		h.l.Error("git: failed to secure join repo path", "handler", "UploadPack", "error", err)
+	repo, ok := repoPathFromcontext(r.Context())
+	if !ok {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte("Failed to find repository path"))
 		return
 	}
 
···
 }
 
 func (h *Knot) ReceivePack(w http.ResponseWriter, r *http.Request) {
-	did := chi.URLParam(r, "did")
 	name := chi.URLParam(r, "name")
-	_, err := securejoin.SecureJoin(h.c.Repo.ScanPath, filepath.Join(did, name))
-	if err != nil {
-		gitError(w, err.Error(), http.StatusForbidden)
-		h.l.Error("git: failed to secure join repo path", "handler", "ReceivePack", "error", err)
-		return
-	}
-
 	h.RejectPush(w, r, name)
 }
 
···
 		fmt.Fprintf(w, " Try:\ngit remote set-url --push origin git@%s:%s/%s\n\n... and push again.", hostname, ownerHandle, unqualifiedRepoName)
 	}
 	fmt.Fprintf(w, "\n\n")
+}
+
+func isDir(path string) (bool, error) {
+	info, err := os.Stat(path)
+	if err == nil && info.IsDir() {
+		return true, nil
+	}
+	if os.IsNotExist(err) {
+		return false, nil
+	}
+	return false, err
 }
 
 func gitError(w http.ResponseWriter, msg string, status int) {

knotserver/router.go

···
 	"fmt"
 	"log/slog"
 	"net/http"
+	"path/filepath"
 	"strings"
 
+	securejoin "github.com/cyphar/filepath-securejoin"
 	"github.com/go-chi/chi/v5"
 	"tangled.org/core/idresolver"
 	"tangled.org/core/jetstream"
···
 
 	r.Route("/{did}", func(r chi.Router) {
 		r.Use(h.resolveDidRedirect)
+		r.Use(h.resolveRepo)
 		r.Route("/{name}", func(r chi.Router) {
 			// routes for git operations
 			r.Get("/info/refs", h.InfoRefs)
···
 		suffix := strings.TrimPrefix(r.URL.Path, "/"+didOrHandle)
 		newPath := fmt.Sprintf("/%s/%s?%s", id.DID.String(), suffix, r.URL.RawQuery)
 		http.Redirect(w, r, newPath, http.StatusTemporaryRedirect)
+	})
+}
+
+type ctxRepoPathKey struct{}
+
+func repoPathFromcontext(ctx context.Context) (string, bool) {
+	v, ok := ctx.Value(ctxRepoPathKey{}).(string)
+	return v, ok
+}
+
+// resolveRepo is a http middleware that constructs git repo path from given did & name pair.
+// It will reject the requests to unknown repos (when dir doesn't exist)
+func (h *Knot) resolveRepo(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		did := chi.URLParam(r, "did")
+		name := chi.URLParam(r, "name")
+		repoPath, err := securejoin.SecureJoin(h.c.Repo.ScanPath, filepath.Join(did, name))
+		if err != nil {
+			w.WriteHeader(http.StatusNotFound)
+			w.Write([]byte("Repository not found"))
+			return
+		}
+
+		exist, err := isDir(repoPath)
+		if err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte("Failed to check repository path"))
+			return
+		}
+		if !exist {
+			w.WriteHeader(http.StatusNotFound)
+			w.Write([]byte("Repository not found"))
+			return
+		}
+
+		ctx := context.WithValue(r.Context(), "repoPath", repoPath)
+		next.ServeHTTP(w, r.WithContext(ctx))
 	})
 }