Support serving the output of local commands

CONFIGURATION.md

@@ -11,10 +11,15 @@ When accessing a directory `index.gemini` or `index.gmi` is served.
 # config.yaml
 
 ```yaml
+# Hostname and port to listen for connections on
+hostname: gemini.rocks
+port: 1965
+
 # Path to certificate and private key
 cert: /home/twins/data/certfile.crt
 key: /home/twins/data/keyfile.key
 
+
 # Server paths
 serve:
   -
@@ -25,7 +30,10 @@ serve:
     root: /home/twins/data/help
   -
     path: ^/proxy-example$
-    proxy: gemini://gemini.rocks
+    proxy: gemini://localhost:1966
+  -
+    path: ^/cmd-example$
+    command: uname -a
   -
     path: /
     root: /home/twins/data/home

README.md

@@ -7,7 +7,8 @@
 ## Features
 
 - Serve static files
-- Reverse proxy support
+- Serve output of system commands
+- Reverse proxy requests
 
 ## Download
 

config.go

@@ -7,26 +7,35 @@ import (
 	"os"
 	"regexp"
 
+	"github.com/kballard/go-shellquote"
 	"gopkg.in/yaml.v3"
 )
 
 type serveConfig struct {
+	// Path to match
 	Path string
 
-	Root  string
-	Proxy string
+	// Resource to serve
+	Root    string
+	Proxy   string
+	Command string
 
-	r *regexp.Regexp
+	r   *regexp.Regexp
+	cmd []string
 }
 
 type serverConfig struct {
-	Cert    string
-	Key     string
-	Address string
-	Serve   []*serveConfig
+	Cert     string
+	Key      string
+	Hostname string
+	Port     int
+	Serve    []*serveConfig
 }
 
-var config = &serverConfig{}
+var config = &serverConfig{
+	Hostname: "localhost",
+	Port:     1965,
+}
 
 func readconfig(configPath string) error {
 	if configPath == "" {
@@ -50,8 +59,10 @@ func readconfig(configPath string) error {
 	for _, serve := range config.Serve {
 		if serve.Path == "" {
 			log.Fatal("path must be specified in serve entry")
-		} else if serve.Root != "" && serve.Proxy != "" {
-			log.Fatal("only one root or reverse proxy may defined for a serve entry")
+		} else if (serve.Root != "" && (serve.Proxy != "" || serve.Command != "")) ||
+			(serve.Proxy != "" && (serve.Root != "" || serve.Command != "")) ||
+			(serve.Command != "" && (serve.Root != "" || serve.Proxy != "")) {
+			log.Fatal("only one root, reverse proxy or command may specified in a serve entry")
 		}
 
 		if serve.Path[0] == '^' {
@@ -59,6 +70,13 @@ func readconfig(configPath string) error {
 		} else if serve.Path[len(serve.Path)-1] == '/' {
 			serve.Path = serve.Path[:len(serve.Path)-1]
 		}
+
+		if serve.Command != "" {
+			serve.cmd, err = shellquote.Split(serve.Command)
+			if err != nil {
+				log.Fatalf("failed to parse command %s: %s", serve.cmd, err)
+			}
+		}
 	}
 
 	return nil

go.mod

@@ -4,6 +4,7 @@ go 1.15
 
 require (
 	github.com/h2non/filetype v1.1.0
+	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51
 	github.com/makeworld-the-better-one/go-gemini v0.9.0
 	gopkg.in/yaml.v3 v3.0.0-20200615113413-eeeca48fe776
 )

go.sum

@@ -2,6 +2,8 @@ github.com/google/go-cmp v0.3.1 h1:Xye71clBPdm5HgqGwUkwhbynsUJZhDbS20FvLhQ2izg=
 github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/h2non/filetype v1.1.0 h1:Or/gjocJrJRNK/Cri/TDEKFjAR+cfG6eK65NGYB6gBA=
 github.com/h2non/filetype v1.1.0/go.mod h1:319b3zT68BvV+WRj7cwy856M2ehB3HqNOt6sy1HndBY=
+github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 h1:Z9n2FFNUXsshfwJMBgNA0RU6/i7WVaAegv3PtuIHPMs=
+github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51/go.mod h1:CzGEWj7cYgsdH8dAjBGEr58BoE7ScuLd+fwFZ44+/x8=
 github.com/makeworld-the-better-one/go-gemini v0.9.0 h1:Iz4ywRDrfsyoR8xZOkSKGXXftMR2spIV6ibVuhrKvSw=
 github.com/makeworld-the-better-one/go-gemini v0.9.0/go.mod h1:P7/FbZ+IEIbA/d+A0Y3w2GNgD8SA2AcNv7aDGJbaWG4=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=

main.go

@@ -30,13 +30,15 @@ func main() {
 		log.Fatalf("failed to read configuration file at %s: %v\nSee CONFIGURATION.md for information on configuring twins", *configFile, err)
 	}
 
-	if config.Address == "" {
-		log.Fatal("listen address must be specified")
+	if config.Hostname == "" || config.Port <= 0 {
+		log.Fatal("hostname and port must be specified")
 	}
 
 	if config.Cert == "" || config.Key == "" {
 		log.Fatal("certificate file and private key must be specified (gemini requires TLS for all connections)")
 	}
 
-	listen(config.Address, config.Cert, config.Key)
+	log.Printf("twins running on port %d", config.Port)
+
+	listen(config.Hostname, config.Port, config.Cert, config.Key)
 }

server.go

@@ -10,9 +10,12 @@ import (
 	"net"
 	"net/url"
 	"os"
+	"os/exec"
 	"path"
+	"strconv"
 	"strings"
 	"time"
+	"unicode/utf8"
 
 	"github.com/h2non/filetype"
 	"github.com/makeworld-the-better-one/go-gemini"
@@ -39,39 +42,12 @@ func writeStatus(c net.Conn, code int) {
 		meta = "Bad request"
 	case gemini.StatusNotFound:
 		meta = "Not found"
+	case gemini.StatusProxyRequestRefused:
+		meta = "Proxy request refused"
 	}
 	writeHeader(c, code, meta)
 }
 
-func serveProxy(c net.Conn, proxyURL, requestData string) {
-	original := proxyURL
-
-	tlsConfig := &tls.Config{}
-	if strings.HasPrefix(proxyURL, "gemini://") {
-		proxyURL = proxyURL[9:]
-	} else if strings.HasPrefix(proxyURL, "gemini-insecure://") {
-		proxyURL = proxyURL[18:]
-		tlsConfig.InsecureSkipVerify = true
-	}
-	proxy, err := tls.Dial("tcp", proxyURL, tlsConfig)
-	if err != nil {
-		writeStatus(c, gemini.StatusProxyError)
-		return
-	}
-	defer proxy.Close()
-
-	// Forward request
-	proxy.Write([]byte(requestData))
-	proxy.Write([]byte("\r\n"))
-
-	// Forward response
-	io.Copy(c, proxy)
-
-	if verbose {
-		log.Printf("< %s\n", original)
-	}
-}
-
 func serveFile(c net.Conn, filePath string) {
 	fi, err := os.Stat(filePath)
 	if os.IsNotExist(err) {
@@ -130,6 +106,60 @@ func serveFile(c net.Conn, filePath string) {
 	io.Copy(c, file)
 }
 
+func serveProxy(c net.Conn, requestData, proxyURL string) {
+	original := proxyURL
+
+	tlsConfig := &tls.Config{}
+	if strings.HasPrefix(proxyURL, "gemini://") {
+		proxyURL = proxyURL[9:]
+	} else if strings.HasPrefix(proxyURL, "gemini-insecure://") {
+		proxyURL = proxyURL[18:]
+		tlsConfig.InsecureSkipVerify = true
+	}
+	proxy, err := tls.Dial("tcp", proxyURL, tlsConfig)
+	if err != nil {
+		writeStatus(c, gemini.StatusProxyError)
+		return
+	}
+	defer proxy.Close()
+
+	// Forward request
+	proxy.Write([]byte(requestData))
+	proxy.Write([]byte("\r\n"))
+
+	// Forward response
+	io.Copy(c, proxy)
+
+	if verbose {
+		log.Printf("< %s\n", original)
+	}
+}
+
+func serveCommand(c net.Conn, command []string) {
+	var args []string
+	if len(command) > 0 {
+		args = command[1:]
+	}
+	cmd := exec.Command(command[0], args...)
+
+	var buf bytes.Buffer
+	cmd.Stdout = &buf
+	cmd.Stderr = &buf
+
+	err := cmd.Run()
+	if err != nil {
+		writeStatus(c, gemini.StatusProxyError)
+		return
+	}
+
+	writeHeader(c, gemini.StatusSuccess, "text/gemini; charset=utf-8")
+	c.Write(buf.Bytes())
+
+	if verbose {
+		log.Printf("< %s\n", command)
+	}
+}
+
 func scanCRLF(data []byte, atEOF bool) (advance int, token []byte, err error) {
 	if atEOF && len(data) == 0 {
 		return 0, nil, nil
@@ -147,8 +177,20 @@ func scanCRLF(data []byte, atEOF bool) (advance int, token []byte, err error) {
 }
 
 func handleConn(c net.Conn) {
-	defer c.Close()
+	if verbose {
+		t := time.Now()
+		defer func() {
+			d := time.Since(t)
+			if d > time.Second {
+				d = d.Round(time.Second)
+			} else {
+				d = d.Round(time.Millisecond)
+			}
+			log.Printf("took %s", d)
+		}()
+	}
 
+	defer c.Close()
 	c.SetReadDeadline(time.Now().Add(readTimeout))
 
 	var requestData string
@@ -162,30 +204,63 @@ func handleConn(c net.Conn) {
 		return
 	}
 
-	request, err := url.Parse(requestData)
-	if err != nil || request.Scheme != "gemini" || request.Host == "" {
+	if verbose {
+		log.Printf("> %s\n", requestData)
+	}
+
+	if len(requestData) > 1024 || !utf8.ValidString(requestData) {
 		writeStatus(c, gemini.StatusBadRequest)
 		return
 	}
-	if request.Path == "" {
-		request.Path = "/"
+
+	request, err := url.Parse(requestData)
+	if err != nil || request.Hostname() == "" || strings.ContainsRune(request.Hostname(), ' ') {
+		writeStatus(c, gemini.StatusBadRequest)
+		return
 	}
+
+	var requestPort int
+	if request.Port() != "" {
+		requestPort, err = strconv.Atoi(request.Port())
+		if err != nil {
+			requestPort = 0
+		}
+	}
+
+	if request.Scheme == "" {
+		request.Scheme = "gemini"
+	}
+	if request.Scheme != "gemini" || request.Hostname() != config.Hostname || (requestPort > 0 && requestPort != config.Port) {
+		writeStatus(c, gemini.StatusProxyRequestRefused)
+	}
+
+	if request.Path == "" {
+		// Redirect to /
+		writeHeader(c, gemini.StatusRedirectPermanent, requestData+"/")
+		return
+	}
+
 	pathBytes := []byte(request.Path)
 	strippedPath := request.Path
 	if strippedPath[0] == '/' {
 		strippedPath = strippedPath[1:]
 	}
-	if verbose {
-		log.Printf("> %s\n", request)
-	}
 
 	for _, serve := range config.Serve {
 		if serve.Proxy != "" {
 			if serve.r != nil && serve.r.Match(pathBytes) {
-				serveProxy(c, serve.Proxy, requestData)
+				serveProxy(c, requestData, serve.Proxy)
 				return
 			} else if serve.r == nil && strings.HasPrefix(request.Path, serve.Path) {
-				serveProxy(c, serve.Proxy, requestData)
+				serveProxy(c, requestData, serve.Proxy)
+				return
+			}
+		} else if serve.cmd != nil {
+			if serve.r != nil && serve.r.Match(pathBytes) {
+				serveCommand(c, serve.cmd)
+				return
+			} else if serve.r == nil && strings.HasPrefix(request.Path, serve.Path) {
+				serveCommand(c, serve.cmd)
 				return
 			}
 		}
@@ -213,7 +288,7 @@ func handleListener(l net.Listener) {
 	}
 }
 
-func listen(address, certFile, keyFile string) {
+func listen(hostname string, port int, certFile, keyFile string) {
 	cert, err := tls.LoadX509KeyPair(certFile, keyFile)
 	if err != nil {
 		log.Fatalf("failed to load certificate: %s", err)
@@ -223,9 +298,9 @@ func listen(address, certFile, keyFile string) {
 		Certificates: []tls.Certificate{cert},
 	}
 
-	listener, err := tls.Listen("tcp", address, tlsConfig)
+	listener, err := tls.Listen("tcp", fmt.Sprintf("%s:%d", hostname, port), tlsConfig)
 	if err != nil {
-		log.Fatalf("failed to listen on %s: %s", address, err)
+		log.Fatalf("failed to listen on %s:%d: %s", hostname, port, err)
 	}
 
 	handleListener(listener)