Use URL.EscapePath() in upstream router

changelogs/unreleased/jv-router-escape-path.yml

+---
+title: Use URL.EscapePath() in upstream router
+merge_request:
+author:
+type: security

internal/staticpages/deploy_page_test.go

@@ -23,7 +23,7 @@ func TestIfNoDeployPageExist(t *testing.T) {
 	w := httptest.NewRecorder()
 
 	executed := false
-	st := &Static{dir}
+	st := &Static{DocumentRoot: dir}
 	st.DeployPage(http.HandlerFunc(func(_ http.ResponseWriter, _ *http.Request) {
 		executed = true
 	})).ServeHTTP(w, nil)
@@ -45,7 +45,7 @@ func TestIfDeployPageExist(t *testing.T) {
 	w := httptest.NewRecorder()
 
 	executed := false
-	st := &Static{dir}
+	st := &Static{DocumentRoot: dir}
 	st.DeployPage(http.HandlerFunc(func(_ http.ResponseWriter, _ *http.Request) {
 		executed = true
 	})).ServeHTTP(w, nil)

internal/staticpages/error_pages_test.go

@@ -32,7 +32,7 @@ func TestIfErrorPageIsPresented(t *testing.T) {
 		require.NoError(t, err)
 		require.Equal(t, len(upstreamBody), n, "bytes written")
 	})
-	st := &Static{dir}
+	st := &Static{DocumentRoot: dir}
 	st.ErrorPagesUnless(false, ErrorFormatHTML, h).ServeHTTP(w, nil)
 	w.Flush()
 
@@ -54,7 +54,7 @@ func TestIfErrorPassedIfNoErrorPageIsFound(t *testing.T) {
 		w.WriteHeader(404)
 		fmt.Fprint(w, errorResponse)
 	})
-	st := &Static{dir}
+	st := &Static{DocumentRoot: dir}
 	st.ErrorPagesUnless(false, ErrorFormatHTML, h).ServeHTTP(w, nil)
 	w.Flush()
 
@@ -78,7 +78,7 @@ func TestIfErrorPageIsIgnoredInDevelopment(t *testing.T) {
 		w.WriteHeader(500)
 		fmt.Fprint(w, serverError)
 	})
-	st := &Static{dir}
+	st := &Static{DocumentRoot: dir}
 	st.ErrorPagesUnless(true, ErrorFormatHTML, h).ServeHTTP(w, nil)
 	w.Flush()
 	require.Equal(t, 500, w.Code)
@@ -102,7 +102,7 @@ func TestIfErrorPageIsIgnoredIfCustomError(t *testing.T) {
 		w.WriteHeader(500)
 		fmt.Fprint(w, serverError)
 	})
-	st := &Static{dir}
+	st := &Static{DocumentRoot: dir}
 	st.ErrorPagesUnless(false, ErrorFormatHTML, h).ServeHTTP(w, nil)
 	w.Flush()
 	require.Equal(t, 500, w.Code)
@@ -137,7 +137,7 @@ func TestErrorPageInterceptedByContentType(t *testing.T) {
 			w.WriteHeader(500)
 			fmt.Fprint(w, serverError)
 		})
-		st := &Static{dir}
+		st := &Static{DocumentRoot: dir}
 		st.ErrorPagesUnless(false, ErrorFormatHTML, h).ServeHTTP(w, nil)
 		w.Flush()
 		require.Equal(t, 500, w.Code)
@@ -161,7 +161,7 @@ func TestIfErrorPageIsPresentedJSON(t *testing.T) {
 		require.NoError(t, err)
 		require.Equal(t, len(upstreamBody), n, "bytes written")
 	})
-	st := &Static{""}
+	st := &Static{}
 	st.ErrorPagesUnless(false, ErrorFormatJSON, h).ServeHTTP(w, nil)
 	w.Flush()
 
@@ -181,7 +181,7 @@ func TestIfErrorPageIsPresentedText(t *testing.T) {
 		require.NoError(t, err)
 		require.Equal(t, len(upstreamBody), n, "bytes written")
 	})
-	st := &Static{""}
+	st := &Static{}
 	st.ErrorPagesUnless(false, ErrorFormatText, h).ServeHTTP(w, nil)
 	w.Flush()
 

internal/staticpages/servefile.go

 package staticpages
 
 import (
+	"errors"
+	"fmt"
 	"net/http"
 	"os"
 	"path/filepath"
 	"strings"
 	"time"
 
-	"gitlab.com/gitlab-org/labkit/log"
 	"gitlab.com/gitlab-org/labkit/mask"
 
 	"gitlab.com/gitlab-org/gitlab-workhorse/internal/helper"
+	"gitlab.com/gitlab-org/gitlab-workhorse/internal/log"
 	"gitlab.com/gitlab-org/gitlab-workhorse/internal/urlprefix"
 )
 
@@ -26,21 +28,29 @@ const (
 // upstream.
 func (s *Static) ServeExisting(prefix urlprefix.Prefix, cache CacheMode, notFoundHandler http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		file := filepath.Join(s.DocumentRoot, prefix.Strip(r.URL.Path))
+		if notFoundHandler == nil {
+			notFoundHandler = http.HandlerFunc(http.NotFound)
+		}
+
+		// We intentionally use r.URL.Path instead of r.URL.EscaptedPath() below.
+		// This is to make it possible to serve static files with e.g. a space
+		// %20 in their name.
+		relativePath, err := s.validatePath(prefix.Strip(r.URL.Path))
+		if err != nil {
+			log.WithRequest(r).WithError(err).Error()
+			notFoundHandler.ServeHTTP(w, r)
+			return
+		}
 
-		// The filepath.Join does Clean traversing directories up
+		file := filepath.Join(s.DocumentRoot, relativePath)
 		if !strings.HasPrefix(file, s.DocumentRoot) {
-			helper.Fail500(w, r, &os.PathError{
-				Op:   "open",
-				Path: file,
-				Err:  os.ErrInvalid,
-			})
+			log.WithRequest(r).WithError(errPathTraversal).Error()
+			notFoundHandler.ServeHTTP(w, r)
 			return
 		}
 
 		var content *os.File
 		var fi os.FileInfo
-		var err error
 
 		// Serve pre-gzipped assets
 		if acceptEncoding := r.Header.Get("Accept-Encoding"); strings.Contains(acceptEncoding, "gzip") {
@@ -55,11 +65,7 @@ func (s *Static) ServeExisting(prefix urlprefix.Prefix, cache CacheMode, notFoun
 			content, fi, err = helper.OpenFile(file)
 		}
 		if err != nil {
-			if notFoundHandler != nil {
-				notFoundHandler.ServeHTTP(w, r)
-			} else {
-				http.NotFound(w, r)
-			}
+			notFoundHandler.ServeHTTP(w, r)
 			return
 		}
 		defer content.Close()
@@ -82,3 +88,17 @@ func (s *Static) ServeExisting(prefix urlprefix.Prefix, cache CacheMode, notFoun
 		http.ServeContent(w, r, filepath.Base(file), fi.ModTime(), content)
 	})
 }
+
+var errPathTraversal = errors.New("path traversal")
+
+func (s *Static) validatePath(filename string) (string, error) {
+	filename = filepath.Clean(filename)
+
+	for _, exc := range s.Exclude {
+		if strings.HasPrefix(filename, exc) {
+			return "", fmt.Errorf("file is excluded: %s", exc)
+		}
+	}
+
+	return filename, nil
+}

internal/staticpages/servefile_test.go

@@ -20,7 +20,7 @@ func TestServingNonExistingFile(t *testing.T) {
 	httpRequest, _ := http.NewRequest("GET", "/file", nil)
 
 	w := httptest.NewRecorder()
-	st := &Static{dir}
+	st := &Static{DocumentRoot: dir}
 	st.ServeExisting("/", CacheDisabled, nil).ServeHTTP(w, httpRequest)
 	require.Equal(t, 404, w.Code)
 }
@@ -34,7 +34,7 @@ func TestServingDirectory(t *testing.T) {
 
 	httpRequest, _ := http.NewRequest("GET", "/file", nil)
 	w := httptest.NewRecorder()
-	st := &Static{dir}
+	st := &Static{DocumentRoot: dir}
 	st.ServeExisting("/", CacheDisabled, nil).ServeHTTP(w, httpRequest)
 	require.Equal(t, 404, w.Code)
 }
@@ -44,7 +44,7 @@ func TestServingMalformedUri(t *testing.T) {
 	httpRequest, _ := http.NewRequest("GET", "/../../../static/file", nil)
 
 	w := httptest.NewRecorder()
-	st := &Static{dir}
+	st := &Static{DocumentRoot: dir}
 	st.ServeExisting("/", CacheDisabled, nil).ServeHTTP(w, httpRequest)
 	require.Equal(t, 404, w.Code)
 }
@@ -54,7 +54,7 @@ func TestExecutingHandlerWhenNoFileFound(t *testing.T) {
 	httpRequest, _ := http.NewRequest("GET", "/file", nil)
 
 	executed := false
-	st := &Static{dir}
+	st := &Static{DocumentRoot: dir}
 	st.ServeExisting("/", CacheDisabled, http.HandlerFunc(func(_ http.ResponseWriter, r *http.Request) {
 		executed = (r == httpRequest)
 	})).ServeHTTP(nil, httpRequest)
@@ -76,7 +76,7 @@ func TestServingTheActualFile(t *testing.T) {
 	ioutil.WriteFile(filepath.Join(dir, "file"), []byte(fileContent), 0600)
 
 	w := httptest.NewRecorder()
-	st := &Static{dir}
+	st := &Static{DocumentRoot: dir}
 	st.ServeExisting("/", CacheDisabled, nil).ServeHTTP(w, httpRequest)
 	require.Equal(t, 200, w.Code)
 	if w.Body.String() != fileContent {
@@ -84,6 +84,40 @@ func TestServingTheActualFile(t *testing.T) {
 	}
 }
 
+func TestExcludedPaths(t *testing.T) {
+	testCases := []struct {
+		desc     string
+		path     string
+		found    bool
+		contents string
+	}{
+		{"allowed file", "/file1", true, "contents1"},
+		{"path traversal is allowed", "/uploads/../file1", true, "contents1"},
+		{"files in /uploads/ are invisible", "/uploads/file2", false, ""},
+		{"cannot use path traversal to get to /uploads/", "/foobar/../uploads/file2", false, ""},
+		{"cannot use escaped path traversal to get to /uploads/", "/foobar%2f%2e%2e%2fuploads/file2", false, ""},
+		{"cannot use double escaped path traversal to get to /uploads/", "/foobar%252f%252e%252e%252fuploads/file2", false, ""},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.desc, func(t *testing.T) {
+			httpRequest, err := http.NewRequest("GET", tc.path, nil)
+			require.NoError(t, err)
+
+			w := httptest.NewRecorder()
+			st := &Static{DocumentRoot: "testdata", Exclude: []string{"/uploads/"}}
+			st.ServeExisting("/", CacheDisabled, nil).ServeHTTP(w, httpRequest)
+
+			if tc.found {
+				require.Equal(t, 200, w.Code)
+				require.Equal(t, tc.contents, w.Body.String())
+			} else {
+				require.Equal(t, 404, w.Code)
+			}
+		})
+	}
+}
+
 func testServingThePregzippedFile(t *testing.T, enableGzip bool) {
 	dir, err := ioutil.TempDir("", "deploy")
 	if err != nil {
@@ -108,7 +142,7 @@ func testServingThePregzippedFile(t *testing.T, enableGzip bool) {
 	ioutil.WriteFile(filepath.Join(dir, "file"), []byte(fileContent), 0600)
 
 	w := httptest.NewRecorder()
-	st := &Static{dir}
+	st := &Static{DocumentRoot: dir}
 	st.ServeExisting("/", CacheDisabled, nil).ServeHTTP(w, httpRequest)
 	require.Equal(t, 200, w.Code)
 	if enableGzip {

internal/staticpages/static.go

@@ -2,4 +2,5 @@ package staticpages
 
 type Static struct {
 	DocumentRoot string
+	Exclude      []string
 }

internal/staticpages/testdata/file1

+contents1
\ No newline at end of file

internal/staticpages/testdata/uploads/file2

+contents2
\ No newline at end of file

internal/upstream/routes.go

@@ -62,6 +62,14 @@ const (
 	importPattern        = `^/import/`
 )
 
+var (
+	// For legacy reasons, user uploads are stored in public/uploads.  To
+	// prevent anybody who knows/guesses the URL of a user-uploaded file
+	// from downloading it we configure static.ServeExisting to treat files
+	// under public/uploads/ as if they do not exist.
+	staticExclude = []string{"/uploads/"}
+)
+
 func compileRegexp(regexpStr string) *regexp.Regexp {
 	if len(regexpStr) == 0 {
 		return nil
@@ -181,20 +189,20 @@ func buildProxy(backend *url.URL, version string, rt http.RoundTripper, cfg conf
 // We match against URI not containing the relativeUrlRoot:
 // see upstream.ServeHTTP
 
-func (u *upstream) configureRoutes() {
+func configureRoutes(u *upstream) {
 	api := apipkg.NewAPI(
 		u.Backend,
 		u.Version,
 		u.RoundTripper,
 	)
 
-	static := &staticpages.Static{DocumentRoot: u.DocumentRoot}
+	static := &staticpages.Static{DocumentRoot: u.DocumentRoot, Exclude: staticExclude}
 	proxy := buildProxy(u.Backend, u.Version, u.RoundTripper, u.Config)
 	cableProxy := proxypkg.NewProxy(u.CableBackend, u.Version, u.CableRoundTripper)
 
 	assetsNotFoundHandler := NotFoundUnless(u.DevelopmentMode, proxy)
 	if u.AltDocumentRoot != "" {
-		altStatic := &staticpages.Static{DocumentRoot: u.AltDocumentRoot}
+		altStatic := &staticpages.Static{DocumentRoot: u.AltDocumentRoot, Exclude: staticExclude}
 		assetsNotFoundHandler = altStatic.ServeExisting(
 			u.URLPrefix,
 			staticpages.CacheExpireMax,
@@ -306,12 +314,6 @@ func (u *upstream) configureRoutes() {
 		u.route("POST", snippetUploadPattern, upload.Accelerate(api, signingProxy, preparers.uploads)),
 		u.route("POST", userUploadPattern, upload.Accelerate(api, signingProxy, preparers.uploads)),
 
-		// For legacy reasons, user uploads are stored under the document root.
-		// To prevent anybody who knows/guesses the URL of a user-uploaded file
-		// from downloading it we make sure requests to /uploads/ do _not_ pass
-		// through static.ServeExisting.
-		u.route("", `^/uploads/`, static.ErrorPagesUnless(u.DevelopmentMode, staticpages.ErrorFormatHTML, proxy)),
-
 		// health checks don't intercept errors and go straight to rails
 		// TODO: We should probably not return a HTML deploy page?
 		//       https://gitlab.com/gitlab-org/gitlab-workhorse/issues/230

internal/upstream/upstream.go

@@ -40,6 +40,10 @@ type upstream struct {
 }
 
 func NewUpstream(cfg config.Config, accessLogger *logrus.Logger) http.Handler {
+	return newUpstream(cfg, accessLogger, configureRoutes)
+}
+
+func newUpstream(cfg config.Config, accessLogger *logrus.Logger, routesCallback func(*upstream)) http.Handler {
 	up := upstream{
 		Config:       cfg,
 		accessLogger: accessLogger,
@@ -56,7 +60,7 @@ func NewUpstream(cfg config.Config, accessLogger *logrus.Logger) http.Handler {
 	up.RoundTripper = roundtripper.NewBackendRoundTripper(up.Backend, up.Socket, up.ProxyHeadersTimeout, cfg.DevelopmentMode)
 	up.CableRoundTripper = roundtripper.NewBackendRoundTripper(up.CableBackend, up.CableSocket, up.ProxyHeadersTimeout, cfg.DevelopmentMode)
 	up.configureURLPrefix()
-	up.configureRoutes()
+	routesCallback(&up)
 
 	var correlationOpts []correlation.InboundHandlerOption
 	if cfg.PropagateCorrelationID {
@@ -95,7 +99,7 @@ func (u *upstream) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// Check URL Root
-	URIPath := urlprefix.CleanURIPath(r.URL.Path)
+	URIPath := urlprefix.CleanURIPath(r.URL.EscapedPath())
 	prefix := u.URLPrefix
 	if !prefix.Match(URIPath) {
 		helper.HTTPError(w, r, fmt.Sprintf("Not found %q", URIPath), http.StatusNotFound)

internal/upstream/upstream_test.go

+package upstream
+
+import (
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/require"
+
+	"gitlab.com/gitlab-org/gitlab-workhorse/internal/config"
+)
+
+func TestRouting(t *testing.T) {
+	handle := func(u *upstream, regex string) routeEntry {
+		handler := http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+			io.WriteString(w, regex)
+		})
+		return u.route("", regex, handler)
+	}
+
+	const (
+		foobar = `\A/foobar\z`
+		quxbaz = `\A/quxbaz\z`
+		main   = ""
+	)
+
+	u := newUpstream(config.Config{}, logrus.StandardLogger(), func(u *upstream) {
+		u.Routes = []routeEntry{
+			handle(u, foobar),
+			handle(u, quxbaz),
+			handle(u, main),
+		}
+	})
+
+	ts := httptest.NewServer(u)
+	defer ts.Close()
+
+	testCases := []struct {
+		desc  string
+		path  string
+		route string
+	}{
+		{"main route works", "/", main},
+		{"foobar route works", "/foobar", foobar},
+		{"quxbaz route works", "/quxbaz", quxbaz},
+		{"path traversal works, ends up in quxbaz", "/foobar/../quxbaz", quxbaz},
+		{"escaped path traversal does not match any route", "/foobar%2f%2e%2e%2fquxbaz", main},
+		{"double escaped path traversal does not match any route", "/foobar%252f%252e%252e%252fquxbaz", main},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.desc, func(t *testing.T) {
+			resp, err := http.Get(ts.URL + tc.path)
+			require.NoError(t, err)
+			defer resp.Body.Close()
+
+			body, err := ioutil.ReadAll(resp.Body)
+			require.NoError(t, err)
+
+			require.Equal(t, 200, resp.StatusCode, "response code")
+			require.Equal(t, tc.route, string(body))
+		})
+	}
+}

main_test.go

@@ -222,12 +222,15 @@ func TestDeniedPublicUploadsFile(t *testing.T) {
 	for _, resource := range []string{
 		"/uploads/static.txt",
 		"/uploads%2Fstatic.txt",
+		"/foobar%2F%2E%2E%2Fuploads/static.txt",
 	} {
-		resp, body := httpGet(t, ws.URL+resource, nil)
+		t.Run(resource, func(t *testing.T) {
+			resp, body := httpGet(t, ws.URL+resource, nil)
 
-		require.Equal(t, 404, resp.StatusCode, "GET %q: status code", resource)
-		require.Equal(t, "", body, "GET %q: response body", resource)
-		require.True(t, proxied, "GET %q: never made it to backend", resource)
+			require.Equal(t, 404, resp.StatusCode, "GET %q: status code", resource)
+			require.Equal(t, "", body, "GET %q: response body", resource)
+			require.True(t, proxied, "GET %q: never made it to backend", resource)
+		})
 	}
 }