From e4781e7f379ca3572a4c4a82dfd0e218ee082a77 Mon Sep 17 00:00:00 2001
From: Erick Ruiz de Chavez <erick@fastmail.net>
Date: Wed, 8 Jan 2025 08:29:17 -0500
Subject: [PATCH] Add portal flag

Proxing all small web through /x/ might not be desirable. In this commit I am adding a new argument, -p, that allows proxing all external requests using a third party proxy, like Portal (https://portal.mozz.us).

By proding a value for this parameter any request made to `/x/` whose host does not match the root host will be rejected.
---
 .gitignore |  1 +
 README.md  |  6 +++++-
 main.go    | 61 +++++++++++++++++++++++++++++++++++++++++-------------
 3 files changed, 53 insertions(+), 15 deletions(-)
 create mode 100644 .gitignore

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..863e216
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+kineto
diff --git a/README.md b/README.md
index f0851f3..977abe5 100644
--- a/README.md
+++ b/README.md
@@ -12,7 +12,7 @@ Geminispace, but it defaults to a specific domain.
 
 ```
 $ go build
-$ ./kineto [-b 127.0.0.1:8080] [-s style.css] [-e style.css] gemini://example.org
+$ ./kineto [-b 127.0.0.1:8080] [-s style.css] [-e style.css] [-p https://portal.mozz.us] gemini://example.org
 ```
 
 The -b argument is optional and allows you to bind to an arbitrary address; by
@@ -30,6 +30,10 @@ in a `<style>` block like with the -s flag. The given stylesheet can be a
 relative link, for instance `-e /main.css` will serve `main.css` from the root
 of the proxied Gemini capsule.
 
+The -p argument is optional and allows you to specify a custom Portal to proxy
+external gemini requests. This option will effectively disable the use of `/x/`
+for all external URLs, that is al URLs whose host does not match the proxied site.
+
 ## "kineto"?
 
 It's named after the Contraves-Goerz Kineto Tracking Mount, which is used by
diff --git a/main.go b/main.go
index c96b8a1..5d3b09d 100644
--- a/main.go
+++ b/main.go
@@ -102,18 +102,35 @@ var gemtextPage = template.Must(template.
 		},
 		"url": func(ctx *GemtextContext, s string) template.URL {
 			u, err := url.Parse(s)
+
 			if err != nil {
 				return template.URL("error")
 			}
+
 			u = ctx.URL.ResolveReference(u)
 
 			if u.Scheme == "" || u.Scheme == "gemini" {
 				if u.Host != ctx.Root.Host {
-					u.Path = fmt.Sprintf("/x/%s%s", u.Host, u.Path)
+					if ctx.UsePortal {
+						p, err := url.Parse(ctx.Portal)
+						if err != nil {
+							return template.URL("error")
+						}
+						p = ctx.URL.ResolveReference(p)
+						u.Path = fmt.Sprintf("%s/gemini/%s%s", p.Path, u.Host, u.Path)
+						u.Scheme = p.Scheme
+						u.Host = p.Host
+					} else {
+						u.Path = fmt.Sprintf("/x/%s%s", u.Host, u.Path)
+						u.Scheme = ""
+						u.Host = ""		
+					}
+				} else {
+					u.Scheme = ""
+					u.Host = ""	
 				}
-				u.Scheme = ""
-				u.Host = ""
 			}
+
 			return template.URL(u.String())
 		},
 		"safeCSS": func(s string) template.CSS {
@@ -378,6 +395,8 @@ type GemtextContext struct {
 	Lang        string
 	URL         *url.URL
 	Root        *url.URL
+	UsePortal   bool
+	Portal      string
 }
 
 type InputContext struct {
@@ -410,7 +429,7 @@ func createAnchor(heading string) string {
 }
 
 func proxyGemini(req gemini.Request, external bool, root *url.URL,
-	w http.ResponseWriter, r *http.Request, css string, externalCSS bool) {
+	w http.ResponseWriter, r *http.Request, css string, externalCSS bool, usePortal bool, portal string) {
 
 	ctx, cancel := context.WithTimeout(r.Context(), 20*time.Second)
 	defer cancel()
@@ -514,6 +533,8 @@ func proxyGemini(req gemini.Request, external bool, root *url.URL,
 		Lang:        lang,
 		URL:         req.URL,
 		Root:        root,
+		UsePortal:   usePortal,
+		Portal:      portal,
 	}
 
 	var title bool
@@ -537,12 +558,14 @@ func proxyGemini(req gemini.Request, external bool, root *url.URL,
 
 func main() {
 	var (
-		bind     string = ":8080"
-		css      string = defaultCSS
-		external bool   = false
+		bind      string = ":8080"
+		css       string = defaultCSS
+		external  bool   = false
+		usePortal bool   = false
+		portal    string = ""
 	)
 
-	opts, optind, err := getopt.Getopts(os.Args, "b:c:s:e:")
+	opts, optind, err := getopt.Getopts(os.Args, "b:c:s:e:p:")
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -561,6 +584,9 @@ func main() {
 		case 'e':
 			external = true
 			css = opt.Value
+		case 'p':
+			usePortal = true
+			portal = opt.Value
 		}
 	}
 
@@ -612,10 +638,21 @@ func main() {
 		req.URL.Host = root.Host
 		req.URL.Path = r.URL.Path
 		req.URL.RawQuery = r.URL.RawQuery
-		proxyGemini(req, false, root, w, r, css, external)
+		proxyGemini(req, false, root, w, r, css, external, usePortal, portal)
 	}))
 
 	http.Handle("/x/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		path := strings.SplitN(r.URL.Path, "/", 4)
+		if len(path) != 4 {
+			path = append(path, "")
+		}
+
+		if usePortal && path[2] != root.Host {
+			w.WriteHeader(http.StatusMethodNotAllowed)
+			w.Write([]byte("404 Not found"))
+			return
+		}
+
 		if r.Method == "POST" {
 			r.ParseForm()
 			if q, ok := r.Form["q"]; !ok {
@@ -635,10 +672,6 @@ func main() {
 			return
 		}
 
-		path := strings.SplitN(r.URL.Path, "/", 4)
-		if len(path) != 4 {
-			path = append(path, "")
-		}
 		req := gemini.Request{}
 		req.URL = &url.URL{}
 		req.URL.Scheme = "gemini"
@@ -646,7 +679,7 @@ func main() {
 		req.URL.Path = "/" + path[3]
 		req.URL.RawQuery = r.URL.RawQuery
 		log.Printf("%s (external) %s%s", r.Method, r.URL.Host, r.URL.Path)
-		proxyGemini(req, true, root, w, r, css, external)
+		proxyGemini(req, true, root, w, r, css, external, usePortal, portal)
 	}))
 
 	log.Printf("HTTP server listening on %s", bind)