Add environmental variables

README.md

@@ -18,6 +18,8 @@ Then edit the configuration file `orion.conf` to your wishes and launch the prog
 
     ./orion -config orion.conf
 
+`orion` can also be configured via [environmental variables](variables.md), which should be particularly useful for containerized applications.
+
 ### Create self-signed certificates
 
 To create self-signed certificates for quick testing, you can use the following recipe
@@ -45,6 +47,8 @@ It's recommended to place your certificates in the `/conf` direcory and use the
 
 Note: Use the `chroot` setting in containers for additional security.
 
+See also the supported [environmental variables](variables.md) for additional configuration possibilities.
+
 ## Credits
 
 * This project was inspired by the [titan2](https://gitlab.com/lostleonardo/titan2) minimalistic Gemini server written by lostleonardo.

cmd/orion/config.go

@@ -27,6 +27,38 @@ func (cf *Config) SetDefaults() {
 	cf.ContentDir = "gemini/"
 }
 
+// getenv reads a given environmental variable and returns it's value if present or defval if not present or empty
+func getenv(key string, defval string) string {
+	val := os.Getenv(key)
+	if val == "" {
+		return defval
+	}
+	return val
+}
+
+func getenv_i(key string, defval int) int {
+	val := os.Getenv(key)
+	if val == "" {
+		return defval
+	} else if ret, err := strconv.Atoi(val); err != nil {
+		return defval
+	} else {
+		return ret
+	}
+}
+
+// Load environmental variables
+func (cf *Config) LoadEnv() {
+	cf.Hostname = getenv("ORION_HOSTNAME", cf.Hostname)
+	cf.CertFile = getenv("ORION_CERTFILE", cf.CertFile)
+	cf.Keyfile = getenv("ORION_KEYFILE", cf.Keyfile)
+	cf.BindAddr = getenv("ORION_BIND", cf.BindAddr)
+	cf.ContentDir = getenv("ORION_CONTENTDIR", cf.ContentDir)
+	cf.Chroot = getenv("ORION_CHROOT", cf.Chroot)
+	cf.Uid = getenv_i("ORION_UID", cf.Uid)
+	cf.Gid = getenv_i("ORION_UID", cf.Gid)
+}
+
 func (cf *Config) LoadConfigFile(filename string) error {
 	file, err := os.Open(filename)
 	if err != nil {

cmd/orion/orion.go

@@ -74,6 +74,7 @@ func setgid(gid int) error {
 
 func main() {
 	config.SetDefaults()
+	config.LoadEnv()
 
 	customConfigFile := flag.String("config", "", "Configuration file")
 	flag.Parse()

variables.md

@@ -0,0 +1,15 @@
+# Environmental variables
+
+
+The following table lists all supported environmental variables for usage in `orion`. Environmental variables are in particular useful when working with `orion` as containerized application.
+
+| Name | Description |
+|------|-------------|
+| `ORION_HOSTNAME` | Server hostname to use |
+| `ORION_CERTFILE` | TLS certificate file |
+| `ORION_KEYFILE` | TLS key file |
+| `ORION_BIND` | Bind address for orion (e.g. `:1965`) |
+| `ORION_CONTENTDIR` | Content/data directory |
+| `ORION_CHROOT` | If set, orion will chroot into this directory |
+| `ORION_UID` | If set, orion will perform a setuid to this uid after initialization |
+| `ORION_GID` | If set, orion will perform a setgid to this gid after initialization |