Domain redirects: send an address to another, over HTTP and HTTPS

A website resource can now redirect to a full address (301 or 302), optionally
keeping the path and query, with no target or login. The Add resource wizard
has a Domain redirect choice that opens the HTTPS and HTTP sides together.
Deleting a site no longer removes redirects. Uses Reef v0.1.10 and Blacktip v0.1.9.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

mappings.go

@@ -6,6 +6,8 @@ import (
 	"fmt"
 	"net"
 	"net/http"
+	"net/url"
+	"strconv"
 	"strings"
 	"time"
 
@@ -97,7 +99,16 @@ func (s *Server) validateMapping(c *orgCtx, m *model.Mapping) error {
 	if edge == nil || !s.edgeAllowedFor(edge, c.Org.ID) {
 		return errors.New("choose an edge")
 	}
-	if len(m.Targets) == 0 {
+	redirect := strings.TrimSpace(m.RedirectTo) != ""
+	if redirect {
+		if !model.Web(m.Proto) {
+			return errors.New("only websites (http or https) can redirect")
+		}
+		m.Targets = []model.Target{} // a redirect has nothing behind it
+	} else {
+		m.RedirectTo, m.RedirectPermanent, m.RedirectKeepPath = "", false, false
+	}
+	if len(m.Targets) == 0 && !redirect {
 		return errors.New("add at least one target")
 	}
 	if m.Proto == model.ProtoUDP && len(m.Targets) > 1 {
@@ -173,9 +184,19 @@ func (s *Server) validateMapping(c *orgCtx, m *model.Mapping) error {
 		return errors.New("PROXY protocol must be v1, v2 or off")
 	}
 	// web-only options
-	if !model.Web(m.Proto) {
+	if redirect {
+		to, err := cleanRedirect(m)
+		if err != nil {
+			return err
+		}
+		m.RedirectTo = to
+	}
+	if !model.Web(m.Proto) || redirect {
 		m.Auth, m.Rules, m.RewriteHost = model.Auth{}, nil, ""
 		m.RedirectHTTP, m.BackendHTTPS, m.HealthPath = false, false, ""
+		if redirect {
+			m.HealthSeconds = -1 // nothing to check
+		}
 	} else {
 		a := &m.Auth
 		a.AllowedRoles, a.AllowedUsers, a.AllowedMails = listFromCSV(a.AllowedRoles), listFromCSV(a.AllowedUsers), listFromCSV(a.AllowedMails)
@@ -262,6 +283,28 @@ func (s *Server) validateMapping(c *orgCtx, m *model.Mapping) error {
 	return nil
 }
 
+// cleanRedirect checks where a redirect sends visitors and refuses a destination that would
+// send them straight back to the same address.
+func cleanRedirect(m *model.Mapping) (string, error) {
+	to := strings.TrimSpace(m.RedirectTo)
+	u, err := url.Parse(to)
+	if err != nil || (u.Scheme != "http" && u.Scheme != "https") || u.Hostname() == "" || u.User != nil {
+		return "", errors.New("Redirect to a full address such as https://www.example.com.")
+	}
+	if len(to) > 2048 || strings.ContainsAny(to, " \t\r\n$") {
+		return "", errors.New("The redirect address is too long or contains spaces or a dollar sign.")
+	}
+	port := u.Port()
+	if port == "" {
+		port = map[string]string{"http": "80", "https": "443"}[u.Scheme]
+	}
+	same := u.Scheme == m.Proto && strings.EqualFold(u.Hostname(), m.Hostname) && port == strconv.Itoa(m.Port)
+	if same && (m.RedirectKeepPath || u.Path == "" || u.Path == "/") {
+		return "", errors.New("That redirect would send visitors back to the same address.")
+	}
+	return to, nil
+}
+
 // portLabel is "25565" or, for a range, "2456-2458".
 func portLabel(m model.Mapping) string {
 	if m.LastPort() > m.Port {