Support reloading configuration file

Resolves #2.

CONFIGURATION.md

@@ -16,12 +16,23 @@ Address to listen for connections on in the format of `interface:port`.
 
 `:1965`
 
-## Certificates
+## Hosts
 
-At least one certificate and private key must be specified, as Gemini requires
-TLS.
+Hosts are defined by their hostname followed by one or more paths to serve.
 
-### localhost certificate
+Paths may be defined as fixed strings or regular expressions (starting with `^`).
+
+Paths are matched in the order they are defined.
+
+Fixed string paths will match with and without a trailing slash.
+
+When accessing a directory the file `index.gemini` or `index.gmi` is served.
+
+### Certificates
+
+A certificate and private key must be specified.
+
+#### localhost certificate
 
 Use `openssl` generate a certificate for localhost.
 
@@ -32,7 +43,7 @@ openssl req -x509 -out localhost.crt -keyout localhost.key \
    printf "[dn]\nCN=localhost\n[req]\ndistinguished_name = dn\n[EXT]\nsubjectAltName=DNS:localhost\nkeyUsage=digitalSignature\nextendedKeyUsage=serverAuth")
 ```
 
-### Domain certificate
+#### Domain certificate
 
 Use [certbot](https://certbot.eff.org) to get a certificate from [Let's Encrypt](https://letsencrypt.org) for a domain.
 
@@ -49,18 +60,6 @@ certbot certonly --config-dir /home/www/certs \
 Provide the path to the certificate file at `certs/live/$DOMAIN/fullchain.pem`
 and the private key file at `certs/live/$DOMAIN/privkey.pem` to twins.
 
-## Hosts
-
-Hosts are defined by their hostname followed by one or more paths to serve.
-
-Paths may be defined as fixed strings or regular expressions (starting with `^`).
-
-Paths are matched in the order they are defined.
-
-Fixed string paths will match with and without a trailing slash.
-
-When accessing a directory the file `index.gemini` or `index.gmi` is served.
-
 ### Path
 
 #### Resources
@@ -110,33 +109,37 @@ listen: :1965
 # TLS certificates
 certificates:
   -
-    cert: /home/gemini.rocks/data/cert.crt
-    key: /home/gemini.rocks/data/cert.key
 
 # Hosts and paths to serve
 hosts:
   gemini.rocks:
-    -
-      path: /sites
-      root: /home/gemini.rocks/data/sites
-      listdirectory: true
-    -
-      path: ^/(help|info)$
-      root: /home/gemini.rocks/data/help
-    -
-      path: ^/proxy-example$
-      proxy: gemini://localhost:1966
-    -
-      path: ^/cmd-example$
-      command: uname -a
-    -
-      path: /
-      root: /home/gemini.rocks/data/home
+    cert: /srv/gemini.rocks/data/cert.crt
+    key: /srv/gemini.rocks/data/cert.key
+    paths:
+      -
+        path: /sites
+        root: /home/geminirocks/data/sites
+        listdirectory: true
+      -
+        path: ^/(help|info)$
+        root: /home/geminirocks/data/help
+      -
+        path: ^/proxy-example$
+        proxy: gemini://localhost:1966
+      -
+        path: ^/cmd-example$
+        command: uname -a
+      -
+        path: /
+        root: /home/geminirocks/data/home
   twins.rocketnine.space:
-    -
-      path: /sites
-      root: /home/twins/data/sites
-    -
-      path: /
-      root: /home/twins/data/home
+    cert: /srv/twins.rocketnine.space/data/cert.crt
+    key: /srv/twins.rocketnine.space/data/cert.key
+    paths:
+      -
+        path: /sites
+        root: /home/twins/data/sites
+      -
+        path: /
+        root: /home/twins/data/home
 ```

README.md

@@ -13,6 +13,7 @@ Breaking changes may be made.
   - Directory listing (when enabled)
 - Serve the output of system commands
 - Reverse proxy requests
+- Reload configuration on `SIGHUP`
 
 ## Download
 

config.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"crypto/tls"
 	"errors"
 	"io/ioutil"
 	"log"
@@ -35,26 +36,24 @@ type pathConfig struct {
 	cmd []string
 }
 
-type certConfig struct {
-	Cert string
-	Key  string
+type hostConfig struct {
+	Cert  string
+	Key   string
+	Paths []*pathConfig
+
+	cert *tls.Certificate
 }
 
 type serverConfig struct {
 	Listen string
 
-	Certificates []*certConfig
-
-	Hosts map[string][]*pathConfig
+	Hosts map[string]*hostConfig
 
 	hostname string
 	port     int
 }
 
-var config = &serverConfig{
-	hostname: "localhost",
-	port:     1965,
-}
+var config *serverConfig
 
 func readconfig(configPath string) error {
 	if configPath == "" {
@@ -70,10 +69,16 @@ func readconfig(configPath string) error {
 		return err
 	}
 
-	err = yaml.Unmarshal(configData, &config)
+	var newConfig *serverConfig
+	err = yaml.Unmarshal(configData, &newConfig)
 	if err != nil {
 		return err
 	}
+	config = newConfig
+
+	if config.Listen == "" {
+		log.Fatal("listen address must be specified")
+	}
 
 	split := strings.Split(config.Listen, ":")
 	if len(split) != 2 {
@@ -87,8 +92,18 @@ func readconfig(configPath string) error {
 		}
 	}
 
-	for _, paths := range config.Hosts {
-		for _, serve := range paths {
+	for _, host := range config.Hosts {
+		if host.Cert == "" || host.Key == "" {
+			log.Fatal("a certificate must be specified for each domain (gemini requires TLS for all connections)")
+		}
+
+		cert, err := tls.LoadX509KeyPair(host.Cert, host.Key)
+		if err != nil {
+			log.Fatalf("failed to load certificate: %s", err)
+		}
+		host.cert = &cert
+
+		for _, serve := range host.Paths {
 			if serve.Path == "" {
 				log.Fatal("path must be specified in serve entry")
 			} else if (serve.Root != "" && (serve.Proxy != "" || serve.Command != "")) ||

main.go

@@ -1,11 +1,12 @@
 package main
 
 import (
-	"crypto/tls"
 	"flag"
 	"log"
 	"os"
+	"os/signal"
 	"path"
+	"syscall"
 )
 
 func init() {
@@ -26,29 +27,25 @@ func main() {
 		}
 	}
 
+	sig := make(chan os.Signal, 1)
+	signal.Notify(sig, syscall.SIGHUP)
+	go func() {
+		for {
+			<-sig
+			err := readconfig(*configFile)
+			if err != nil {
+				log.Fatalf("failed to reload configuration file at %s: %v", *configFile, err)
+			}
+			log.Println("configuration reloaded successfully")
+		}
+	}()
+
 	err := readconfig(*configFile)
 	if err != nil {
 		log.Fatalf("failed to read configuration file at %s: %v\nSee CONFIGURATION.md for information on configuring twins", *configFile, err)
 	}
 
-	if config.hostname == "" || config.port <= 0 {
-		log.Fatal("hostname and port must be specified")
-	}
-
-	if len(config.Certificates) == 0 {
-		log.Fatal("at least one certificate must be specified (gemini requires TLS for all connections)")
-	}
-
-	var certificates []tls.Certificate
-	for _, cert := range config.Certificates {
-		cert, err := tls.LoadX509KeyPair(cert.Cert, cert.Key)
-		if err != nil {
-			log.Fatalf("failed to load certificate: %s", err)
-		}
-		certificates = append(certificates, cert)
-	}
-
 	log.Printf("twins running on %s:%d", config.hostname, config.port)
 
-	listen(config.Listen, certificates)
+	listen(config.Listen)
 }

server.go

@@ -382,7 +382,7 @@ func handleConn(c net.Conn) {
 		}
 		matchedHost = true
 
-		for _, serve := range config.Hosts[hostname] {
+		for _, serve := range config.Hosts[hostname].Paths {
 			matchedRegexp := serve.r != nil && serve.r.Match(pathBytes)
 			matchedPrefix := serve.r == nil && strings.HasPrefix(request.Path, serve.Path)
 			if !matchedRegexp && !matchedPrefix {
@@ -440,6 +440,7 @@ func handleConn(c net.Conn) {
 				return
 			}
 		}
+		break
 	}
 
 	if matchedHost {
@@ -449,6 +450,17 @@ func handleConn(c net.Conn) {
 	}
 }
 
+func getCertificate(info *tls.ClientHelloInfo) (*tls.Certificate, error) {
+	host := config.Hosts[info.ServerName]
+	if host != nil {
+		return host.cert, nil
+	}
+	for _, host := range config.Hosts {
+		return host.cert, nil
+	}
+	return nil, nil
+}
+
 func handleListener(l net.Listener) {
 	for {
 		conn, err := l.Accept()
@@ -460,9 +472,10 @@ func handleListener(l net.Listener) {
 	}
 }
 
-func listen(address string, certificates []tls.Certificate) {
+func listen(address string) {
 	tlsConfig := &tls.Config{
-		Certificates: certificates,
+		ClientAuth:     tls.RequestClientCert,
+		GetCertificate: getCertificate,
 	}
 
 	listener, err := tls.Listen("tcp", address, tlsConfig)