2 files changed, 62 insertions, 0 deletions
diff --git a/routers/web/repo/http.go b/routers/web/repo/http.go
index 30d382b8ef..649d6d1eb1 100644
--- a/routers/web/repo/http.go
+++ b/routers/web/repo/http.go
@@ -366,7 +366,26 @@ func (h *serviceHandler) setHeaderCacheForever() {
 	h.w.Header().Set("Cache-Control", "public, max-age=31536000")
 }
 
+func containsParentDirectorySeparator(v string) bool {
+	if !strings.Contains(v, "..") {
+		return false
+	}
+	for _, ent := range strings.FieldsFunc(v, isSlashRune) {
+		if ent == ".." {
+			return true
+		}
+	}
+	return false
+}
+
+func isSlashRune(r rune) bool { return r == '/' || r == '\\' }
+
 func (h *serviceHandler) sendFile(contentType, file string) {
+	if containsParentDirectorySeparator(file) {
+		log.Error("request file path contains invalid path: %v", file)
+		h.w.WriteHeader(http.StatusBadRequest)
+		return
+	}
 	reqFile := path.Join(h.dir, file)
 
 	fi, err := os.Stat(reqFile)
diff --git a/routers/web/repo/http_test.go b/routers/web/repo/http_test.go
new file mode 100644
index 0000000000..58ac1c07a1
--- /dev/null
+++ b/routers/web/repo/http_test.go
@@ -0,0 +1,43 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package repo
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestContainsParentDirectorySeparator(t *testing.T) {
+	tests := []struct {
+		v string
+		b bool
+	}{
+		{
+			v: `user2/repo1/info/refs`,
+			b: false,
+		},
+		{
+			v: `user2/repo1/HEAD`,
+			b: false,
+		},
+		{
+			v: `user2/repo1/some.../strange_file...mp3`,
+			b: false,
+		},
+		{
+			v: `user2/repo1/../../custom/conf/app.ini`,
+			b: true,
+		},
+		{
+			v: `user2/repo1/objects/info/..\..\..\..\custom\conf\app.ini`,
+			b: true,
+		},
+	}
+
+	for i := range tests {
+		assert.EqualValues(t, tests[i].b, containsParentDirectorySeparator(tests[i].v))
+	}
+}