"cmd" modifier to override CGI executable

fixes #6

8 files changed, 41 insertions, 9 deletions

diff --git a/example.conf b/example.conf
index 6181fcf..18f58f7 100644
--- a/example.conf
+++ b/example.conf
@@ -86,7 +86,14 @@ gemini 0.0.0.0:1965 {
 	# "static" and "cgi" directives work much like in gopher servers.
 	# There is no "extendedgophermap" modifier in gemini, however.
 	static /var/gemini/docs at / with dirdefault index.gmi, dirlist, exec
-	cgi /var/gemini/cgi at /cgi-bin
+
+	# The "cmd" directive modifier can apply to any "cgi" or "static ... with exec" directives.
+	# It specifies a filesystem path to an executable file, which will be executed in place of the CGI script.
+	# Even with "cmd" in use, it will only be invoked if the request path points to a world-executable file
+	#   and with the working directory and environment variables of the requested script.
+	# So generally "cmd" scripts can end with something like "exec $SCRIPT_PATH", perhaps after imposing
+	#   resource limits or some other security sandbox around it first.
+	cgi /var/gemini/cgi at /cgi-bin with cmd /var/runcgi
 
 	# The "autoatom" modifier is allowed on directives in a gemini server.
 	# It causes any text/gemini responses to be available as atom at <path>.atom.
diff --git a/finger.go b/finger.go
index 941e705..75d8160 100644
--- a/finger.go
+++ b/finger.go
@@ -61,7 +61,12 @@ func fingerHandler(route RouteDirective) sr.Handler {
 		}
 
 		if st.Mode()&5 == 5 && (route.Modifiers.Exec || route.Type == "cgi") {
-			buf, code, err := cgi.RunCGI(ctx, request, fpath, "/", nil)
+			workdir := filepath.Dir(fpath)
+			if route.Modifiers.ExecCmd != "" {
+				fpath = route.Modifiers.ExecCmd
+			}
+
+			buf, code, err := cgi.RunCGI(ctx, request, fpath, "/", workdir, nil)
 			if err != nil {
 				return finger.Error("execution error")
 			}
diff --git a/gemini.go b/gemini.go
index 3fb7a46..87af01f 100644
--- a/gemini.go
+++ b/gemini.go
@@ -94,7 +94,7 @@ func addGeminiRoute(router *sr.Router, route RouteDirective) {
 		addGeminiStaticRoute(router, route)
 	case "cgi":
 		buildAndAddRoute(router, route, func(route RouteDirective) sr.Handler {
-			handler := cgi.GeminiCGIDirectory(route.FsPath, route.URLPath)
+			handler := cgi.GeminiCGIDirectory(route.FsPath, route.URLPath, route.Modifiers.ExecCmd)
 			if route.Modifiers.AutoAtom {
 				handler = atomconv.Auto(handler)
 			}
@@ -110,7 +110,7 @@ func addGeminiStaticRoute(router *sr.Router, route RouteDirective) {
 		handlers := []sr.Handler{}
 
 		if route.Modifiers.Exec {
-			handlers = append(handlers, cgi.GeminiCGIDirectory(route.FsPath, route.URLPath))
+			handlers = append(handlers, cgi.GeminiCGIDirectory(route.FsPath, route.URLPath, route.Modifiers.ExecCmd))
 		}
 
 		handlers = append(handlers, fs.GeminiFileHandler(route.FsPath, route.URLPath))
diff --git a/go.mod b/go.mod
index 09affeb..6c67c53 100644
--- a/go.mod
+++ b/go.mod
@@ -4,7 +4,7 @@ go 1.21.0
 
 require (
 	github.com/go-kit/log v0.2.1
-	tildegit.org/tjp/sliderule v1.4.1
+	tildegit.org/tjp/sliderule v1.4.2-0.20231010204754-04449ed66e42
 	tildegit.org/tjp/syw v0.9.2
 )
 
diff --git a/go.sum b/go.sum
index 7c0c074..d0231f4 100644
--- a/go.sum
+++ b/go.sum
@@ -10,7 +10,7 @@ github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKs
 github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-tildegit.org/tjp/sliderule v1.4.1 h1:L1evSiVqhiHSVgWBCFgDXhT30OZdWUHRq8CahCDkd+I=
-tildegit.org/tjp/sliderule v1.4.1/go.mod h1:opdo8E25iS9X9pNismM8U7pCH8XO0PdRIIhdADn8Uik=
+tildegit.org/tjp/sliderule v1.4.2-0.20231010204754-04449ed66e42 h1:KkbiQO/kIxwABGqhocShHvehchDuGyQzvhV61SKfhO8=
+tildegit.org/tjp/sliderule v1.4.2-0.20231010204754-04449ed66e42/go.mod h1:opdo8E25iS9X9pNismM8U7pCH8XO0PdRIIhdADn8Uik=
 tildegit.org/tjp/syw v0.9.2 h1:bwLRXJqC5RHes2dfntgePHYnh6iIQC9FZpFBTReemQ0=
 tildegit.org/tjp/syw v0.9.2/go.mod h1:Oo05KA7QibiXxoPh5jzpKUq/RG4U3nz7qs6QVitZw8I=
diff --git a/gopher.go b/gopher.go
index 3030bac..1c13886 100644
--- a/gopher.go
+++ b/gopher.go
@@ -57,7 +57,7 @@ func addGopherStaticRoute(router *sr.Router, route RouteDirective) {
 		handlers := []sr.Handler{}
 
 		if route.Modifiers.Exec {
-			handlers = append(handlers, cgi.ExecGopherMaps(route.FsPath, route.URLPath, settings))
+			handlers = append(handlers, cgi.ExecGopherMaps(route.FsPath, route.URLPath, route.Modifiers.ExecCmd, settings))
 		}
 
 		handlers = append(handlers, fs.GopherFileHandler(route.FsPath, route.URLPath, settings))
@@ -90,7 +90,7 @@ func addGopherCGIRoute(router *sr.Router, route RouteDirective) {
 	}
 
 	buildAndAddRoute(router, route, func(route RouteDirective) sr.Handler {
-		return cgi.GopherCGIDirectory(route.FsPath, route.URLPath, settings)
+		return cgi.GopherCGIDirectory(route.FsPath, route.URLPath, route.Modifiers.ExecCmd, settings)
 	})
 }
 
diff --git a/parse.go b/parse.go
index 0fe3f30..d087e95 100644
--- a/parse.go
+++ b/parse.go
@@ -293,6 +293,10 @@ func validateRoute(serverType string, dir *RouteDirective) error {
 		return fmt.Errorf("titan modifier only allowed on gemini{static}")
 	}
 
+	if dir.Modifiers.ExecCmd != "" && !(dir.Type == "cgi" || (dir.Type == "static" && dir.Modifiers.Exec)) {
+		return fmt.Errorf("'cmd' modifier only valid on 'cgi' and 'static...with exec' directives")
+	}
+
 	return nil
 }
 
@@ -410,6 +414,21 @@ func parseModifiers(text string) (Modifiers, string, error) {
 			mod.DirList = true
 		case "exec":
 			mod.Exec = true
+		case "cmd":
+			if sep != " " {
+				return mod, "", errors.New("invalid 'cmd' clause")
+			}
+			text = strings.TrimLeft(text, " \t")
+			idx = strings.IndexAny(text, " \t,")
+			if idx == 0 {
+				return mod, "", errors.New("invalid 'cmd' clause")
+			} else if idx < 0 {
+				mod.ExecCmd = text
+				text = ""
+			} else {
+				mod.ExecCmd = text[0:idx]
+				text = text[idx+1:]
+			}
 		case "extendedgophermap":
 			mod.ExtendedGophermap = true
 		case "autoatom":
diff --git a/types.go b/types.go
index 8d010b2..3dd3935 100644
--- a/types.go
+++ b/types.go
@@ -14,6 +14,7 @@ type Modifiers struct {
 	DirDefault        string
 	DirList           bool
 	Exec              bool
+	ExecCmd           string
 	ExtendedGophermap bool
 	AutoAtom          bool
 	Titan             *Auth