From e2232a8dc8f551c108a8c12a2dce0dff3106f372 Mon Sep 17 00:00:00 2001
From: Trevor Slocum <trevor@rocketnine.space>
Date: Tue, 24 Nov 2020 18:18:16 -0800
Subject: [PATCH] Add option to allow local file access

---
 CHANGELOG                |  1 +
 CONFIGURATION.md         |  8 ++++++++
 main.go                  |  4 +++-
 pkg/gmitohtml/convert.go |  5 +++++
 pkg/gmitohtml/daemon.go  | 43 +++++++++++++++++++++++++++++++---------
 5 files changed, 51 insertions(+), 10 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index 44587e4..389a39f 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,6 @@
 1.0.1:
 - Display navigation bar in pages
+- Add option to allow local file access
 
 1.0.0:
 - Initial release
diff --git a/CONFIGURATION.md b/CONFIGURATION.md
index 33ab118..19139c7 100644
--- a/CONFIGURATION.md
+++ b/CONFIGURATION.md
@@ -19,6 +19,14 @@ openssl req -x509 -out localhost.crt -keyout localhost.key \
 Files `localhost.crt` and `localhost.key` are generated. Rename these files to
 match the domain where the certificate will be used.
 
+## Allow file:// access
+
+By default, local files are not served by gmitohtml. When executed with the
+`--allow-file` argument, local files may be accessed via `file://`.
+
+For example, to view `/home/dioscuri/sites/gemlog/index.gmi`, navigate to
+`file:///home/dioscuri/sites/gemlog/index.gmi`. 
+ 
 # Example config.yaml
 
 ```yaml
diff --git a/main.go b/main.go
index f5eb093..da503f0 100644
--- a/main.go
+++ b/main.go
@@ -33,9 +33,11 @@ func openBrowser(url string) {
 
 func main() {
 	var view bool
+	var allowFile bool
 	var daemon string
 	var configFile string
 	flag.BoolVar(&view, "view", false, "open web browser")
+	flag.BoolVar(&allowFile, "allow-file", false, "allow local file access via file://")
 	flag.StringVar(&daemon, "daemon", "", "start daemon on specified address")
 	flag.StringVar(&configFile, "config", "", "path to configuration file")
 	// TODO option to include response header in page
@@ -76,7 +78,7 @@ func main() {
 	}
 
 	if daemon != "" {
-		err := gmitohtml.StartDaemon(daemon)
+		err := gmitohtml.StartDaemon(daemon, allowFile)
 		if err != nil {
 			log.Fatal(err)
 		}
diff --git a/pkg/gmitohtml/convert.go b/pkg/gmitohtml/convert.go
index 7b35753..819678d 100644
--- a/pkg/gmitohtml/convert.go
+++ b/pkg/gmitohtml/convert.go
@@ -22,6 +22,11 @@ func rewriteURL(u string, loc *url.URL) string {
 	if daemonAddress != "" {
 		if strings.HasPrefix(u, "gemini://") {
 			return "http://" + daemonAddress + "/gemini/" + u[9:]
+		} else if strings.HasPrefix(u, "file://") {
+			if !allowFileAccess {
+				return "http://" + daemonAddress + "/?FileAccessNotAllowed"
+			}
+			return "http://" + daemonAddress + "/file/" + u[7:]
 		} else if strings.Contains(u, "://") {
 			return u
 		} else if loc != nil && len(u) > 0 && !strings.HasPrefix(u, "//") {
diff --git a/pkg/gmitohtml/daemon.go b/pkg/gmitohtml/daemon.go
index abad18b..ef2b665 100644
--- a/pkg/gmitohtml/daemon.go
+++ b/pkg/gmitohtml/daemon.go
@@ -11,13 +11,17 @@ import (
 	"log"
 	"net/http"
 	"net/url"
+	"path"
 	"strings"
 	"time"
 )
 
 var lastRequestTime = time.Now().Unix()
 
-var clientCerts = make(map[string]tls.Certificate)
+var (
+	clientCerts     = make(map[string]tls.Certificate)
+	allowFileAccess bool
+)
 
 // ErrInvalidCertificate is the error returned when an invalid certificate is provided.
 var ErrInvalidCertificate = errors.New("invalid certificate")
@@ -165,12 +169,17 @@ func handleRequest(writer http.ResponseWriter, request *http.Request) {
 	}
 
 	pathSplit := strings.Split(request.URL.Path, "/")
-	if len(pathSplit) < 2 || pathSplit[1] != "gemini" {
+	if len(pathSplit) < 2 || (pathSplit[1] != "gemini" && (!allowFileAccess || pathSplit[1] != "file")) {
 		writer.Write([]byte("Error: invalid protocol, only Gemini is supported"))
 		return
 	}
 
-	u, err := url.ParseRequestURI("gemini://" + strings.Join(pathSplit[2:], "/"))
+	scheme := "gemini://"
+	if pathSplit[1] == "file" {
+		scheme = "file://"
+	}
+
+	u, err := url.ParseRequestURI(scheme + strings.Join(pathSplit[2:], "/"))
 	if err != nil {
 		writer.Write([]byte("Error: invalid URL"))
 		return
@@ -186,9 +195,24 @@ func handleRequest(writer http.ResponseWriter, request *http.Request) {
 		return
 	}
 
-	header, data, err := fetch(u.String())
-	if err != nil {
-		fmt.Fprintf(writer, "Error: failed to fetch %s: %s", u, err)
+	var header []byte
+	var data []byte
+	if scheme == "gemini://" {
+		header, data, err = fetch(u.String())
+		if err != nil {
+			fmt.Fprintf(writer, "Error: failed to fetch %s: %s", u, err)
+			return
+		}
+	} else if allowFileAccess && scheme == "file://" {
+		header = []byte("20 text/gemini; charset=utf-8")
+		data, err = ioutil.ReadFile(path.Join("/", strings.Join(pathSplit[2:], "/")))
+		if err != nil {
+			fmt.Fprintf(writer, "Error: failed to read file %s: %s", u, err)
+			return
+		}
+		data = Convert(data, u.String())
+	} else {
+		writer.Write([]byte("Error: invalid URL"))
 		return
 	}
 
@@ -219,10 +243,11 @@ func handleAssets(writer http.ResponseWriter, request *http.Request) {
 }
 
 // StartDaemon starts the page conversion daemon.
-func StartDaemon(address string) error {
-	loadAssets()
-
+func StartDaemon(address string, allowFile bool) error {
 	daemonAddress = address
+	allowFileAccess = allowFile
+
+	loadAssets()
 
 	handler := http.NewServeMux()
 	handler.HandleFunc("/assets/style.css", handleAssets)