Refactor URL detection (#29960)

"Redirect" functions should only redirect if the target is for current Gitea site.

modules/httplib/url.go

@@ -8,20 +8,40 @@ import (
 	"strings"
 
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
 )
 
-// IsRiskyRedirectURL returns true if the URL is considered risky for redirects
-func IsRiskyRedirectURL(s string) bool {
+func urlIsRelative(s string, u *url.URL) bool {
 	// Unfortunately browsers consider a redirect Location with preceding "//", "\\", "/\" and "\/" as meaning redirect to "http(s)://REST_OF_PATH"
 	// Therefore we should ignore these redirect locations to prevent open redirects
 	if len(s) > 1 && (s[0] == '/' || s[0] == '\\') && (s[1] == '/' || s[1] == '\\') {
-		return true
+		return false
 	}
-
-	u, err := url.Parse(s)
-	if err != nil || ((u.Scheme != "" || u.Host != "") && !strings.HasPrefix(strings.ToLower(s), strings.ToLower(setting.AppURL))) {
-		return true
-	}
-
-	return false
+	return u != nil && u.Scheme == "" && u.Host == ""
+}
+
+// IsRelativeURL detects if a URL is relative (no scheme or host)
+func IsRelativeURL(s string) bool {
+	u, err := url.Parse(s)
+	return err == nil && urlIsRelative(s, u)
+}
+
+func IsCurrentGiteaSiteURL(s string) bool {
+	u, err := url.Parse(s)
+	if err != nil {
+		return false
+	}
+	if u.Path != "" {
+		u.Path = "/" + util.PathJoinRelX(u.Path)
+		if !strings.HasSuffix(u.Path, "/") {
+			u.Path += "/"
+		}
+	}
+	if urlIsRelative(s, u) {
+		return u.Path == "" || strings.HasPrefix(strings.ToLower(u.Path), strings.ToLower(setting.AppSubURL+"/"))
+	}
+	if u.Path == "" {
+		u.Path = "/"
+	}
+	return strings.HasPrefix(strings.ToLower(u.String()), strings.ToLower(setting.AppURL))
 }

modules/httplib/url_test.go

@@ -7,32 +7,65 @@ import (
 	"testing"
 
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/test"
 
 	"github.com/stretchr/testify/assert"
 )
 
-func TestIsRiskyRedirectURL(t *testing.T) {
-	setting.AppURL = "http://localhost:3000/"
-	tests := []struct {
-		input string
-		want  bool
-	}{
-		{"", false},
-		{"foo", false},
-		{"/", false},
-		{"/foo?k=%20#abc", false},
-
-		{"//", true},
-		{"\\\\", true},
-		{"/\\", true},
-		{"\\/", true},
-		{"mail:a@b.com", true},
-		{"https://test.com", true},
-		{setting.AppURL + "/foo", false},
+func TestIsRelativeURL(t *testing.T) {
+	defer test.MockVariableValue(&setting.AppURL, "http://localhost:3000/sub/")()
+	defer test.MockVariableValue(&setting.AppSubURL, "/sub")()
+	rel := []string{
+		"",
+		"foo",
+		"/",
+		"/foo?k=%20#abc",
 	}
-	for _, tt := range tests {
-		t.Run(tt.input, func(t *testing.T) {
-			assert.Equal(t, tt.want, IsRiskyRedirectURL(tt.input))
-		})
+	for _, s := range rel {
+		assert.True(t, IsRelativeURL(s), "rel = %q", s)
+	}
+	abs := []string{
+		"//",
+		"\\\\",
+		"/\\",
+		"\\/",
+		"mailto:a@b.com",
+		"https://test.com",
+	}
+	for _, s := range abs {
+		assert.False(t, IsRelativeURL(s), "abs = %q", s)
 	}
 }
+
+func TestIsCurrentGiteaSiteURL(t *testing.T) {
+	defer test.MockVariableValue(&setting.AppURL, "http://localhost:3000/sub/")()
+	defer test.MockVariableValue(&setting.AppSubURL, "/sub")()
+	good := []string{
+		"?key=val",
+		"/sub",
+		"/sub/",
+		"/sub/foo",
+		"/sub/foo/",
+		"http://localhost:3000/sub?key=val",
+		"http://localhost:3000/sub/",
+	}
+	for _, s := range good {
+		assert.True(t, IsCurrentGiteaSiteURL(s), "good = %q", s)
+	}
+	bad := []string{
+		"/",
+		"//",
+		"\\\\",
+		"/foo",
+		"http://localhost:3000/sub/..",
+		"http://localhost:3000/other",
+		"http://other/",
+	}
+	for _, s := range bad {
+		assert.False(t, IsCurrentGiteaSiteURL(s), "bad = %q", s)
+	}
+
+	setting.AppURL = "http://localhost:3000/"
+	setting.AppSubURL = ""
+	assert.True(t, IsCurrentGiteaSiteURL("http://localhost:3000?key=val"))
+}