Feat: Pass encoded characters in path unchanged

We enable passing substrings that represent encoded reserved symbols, like
`%2f` for `/`, in the path of a request.

NB: This does not enable using encoded characters in rewrite rules (e.g. in the
urlprefix directive).

Cf. fabiolb#347 and fabiolb#486

route/target.go

@@ -70,20 +70,37 @@ func (t *Target) BuildRedirectURL(requestURL *url.URL) {
 		Scheme:   t.URL.Scheme,
 		Host:     t.URL.Host,
 		Path:     t.URL.Path,
+		RawPath:  t.URL.Path,
 		RawQuery: t.URL.RawQuery,
 	}
+	// treat case of $path not separated with a / from host
 	if strings.HasSuffix(t.RedirectURL.Host, "$path") {
 		t.RedirectURL.Host = t.RedirectURL.Host[:len(t.RedirectURL.Host)-len("$path")]
 		t.RedirectURL.Path = "$path"
 	}
+	// remove / before $path in redirect url
 	if strings.Contains(t.RedirectURL.Path, "/$path") {
 		t.RedirectURL.Path = strings.Replace(t.RedirectURL.Path, "/$path", "$path", 1)
+		t.RedirectURL.RawPath = strings.Replace(t.RedirectURL.RawPath, "/$path", "$path", 1)
 	}
+	// insert passed request path, remove strip path, set quer
 	if strings.Contains(t.RedirectURL.Path, "$path") {
+		// replace in not raw path
 		t.RedirectURL.Path = strings.Replace(t.RedirectURL.Path, "$path", requestURL.Path, 1)
+		// replace in raw path - determine replacement first
+		var replaceRawPath string
+		if requestURL.RawPath == "" {
+			replaceRawPath = requestURL.Path
+		} else {
+			replaceRawPath = requestURL.RawPath
+		}
+		t.RedirectURL.RawPath = strings.Replace(t.RedirectURL.RawPath, "$path", replaceRawPath, 1)
+		// remove stip path
 		if t.StripPath != "" && strings.HasPrefix(t.RedirectURL.Path, t.StripPath) {
 			t.RedirectURL.Path = t.RedirectURL.Path[len(t.StripPath):]
+			t.RedirectURL.RawPath = t.RedirectURL.RawPath[len(t.StripPath):]
 		}
+		// set query
 		if t.RedirectURL.RawQuery == "" && requestURL.RawQuery != "" {
 			t.RedirectURL.RawQuery = requestURL.RawQuery
 		}

route/target_test.go

@@ -123,6 +123,16 @@ func TestTarget_BuildRedirectURL(t *testing.T) {
 				{req: "/abc/?aaa=1", want: "https://foo.com/bbb/abc/?aaa=1"},
 			},
 		},
+		{ // simple redirect to corresponding path with encoded char in path
+			route: "route add svc / http://bar.com/$path",
+			tests: []routeTest{
+				{req: "/%20", want: "http://bar.com/%20"},
+				{req: "/a%2fbc", want: "http://bar.com/a%2fbc"},
+				{req: "/a/b%22/c", want: "http://bar.com/a/b%22/c"},
+				{req: "/%2f/?aaa=1", want: "http://bar.com/%2f/?aaa=1"},
+				{req: "/%20/a%2f/", want: "http://bar.com/%20/a%2f/"},
+			},
+		},
 		{ // strip prefix
 			route: "route add svc /stripme http://bar.com/$path opts \"strip=/stripme\"",
 			tests: []routeTest{