add support for reading password from secret/file (#22)

* add support for reading password from secret/file

Signed-off-by: mvadu <8618235+mvadu@users.noreply.github.com>

* avoid trimming

Signed-off-by: mvadu <8618235+mvadu@users.noreply.github.com>

README.md

@@ -127,6 +127,7 @@ services:
       - server_port=9617
       - interval=10s
       - log_limit=10000
+      - password_from_file=true
 ```
 ### Swarm mode (docker swarm init)
 
@@ -159,6 +160,7 @@ services:
       - server_port=9617
       - interval=10s
       - log_limit=10000
+      - password_from_file=true
 ```
 
 ## Usage

config/configuration.go

@@ -3,6 +3,7 @@ package config
 import (
 	"context"
 	"fmt"
+	"io/ioutil"
 	"log"
 	"os"
 	"reflect"
@@ -16,28 +17,30 @@ import (
 
 // Config is the exporter CLI configuration.
 type Config struct {
-	AdguardProtocol string        `config:"adguard_protocol"`
-	AdguardHostname string        `config:"adguard_hostname"`
-	AdguardUsername string        `config:"adguard_username"`
-	AdguardPassword string        `config:"adguard_password"`
-	AdguardPort     string        `config:"adguard_port"`
-	ServerPort      string        `config:"server_port"`
-	Interval        time.Duration `config:"interval"`
-	LogLimit        string        `config:"log_limit"`
-	RDnsEnabled     bool          `config:"rdns_enabled"`
+	AdguardProtocol  string        `config:"adguard_protocol"`
+	AdguardHostname  string        `config:"adguard_hostname"`
+	AdguardUsername  string        `config:"adguard_username"`
+	AdguardPassword  string        `config:"adguard_password"`
+	AdguardPort      string        `config:"adguard_port"`
+	ServerPort       string        `config:"server_port"`
+	Interval         time.Duration `config:"interval"`
+	LogLimit         string        `config:"log_limit"`
+	RDnsEnabled      bool          `config:"rdns_enabled"`
+	PasswordFromFile bool          `config:"password_from_file"`
 }
 
 func getDefaultConfig() *Config {
 	return &Config{
-		AdguardProtocol: "http",
-		AdguardHostname: "127.0.0.1",
-		AdguardUsername: "",
-		AdguardPassword: "",
-		AdguardPort:     "80",
-		ServerPort:      "9617",
-		Interval:        10 * time.Second,
-		LogLimit:        "1000",
-		RDnsEnabled:     true,
+		AdguardProtocol:  "http",
+		AdguardHostname:  "127.0.0.1",
+		AdguardUsername:  "",
+		AdguardPassword:  "",
+		AdguardPort:      "80",
+		ServerPort:       "9617",
+		Interval:         10 * time.Second,
+		LogLimit:         "1000",
+		RDnsEnabled:      true,
+		PasswordFromFile: false,
 	}
 }
 
@@ -69,6 +72,17 @@ func Load() *Config {
 		}
 	}
 
+	//Set the adguard password based on the input configuration
+	if cfg.PasswordFromFile {
+		secret, err := ioutil.ReadFile(cfg.AdguardPassword)
+		if err != nil {
+			log.Printf("unable to read AdguardPassword from %s due to %s", cfg.AdguardPassword, err)
+			os.Exit(1)
+		}
+
+		cfg.AdguardPassword = string(secret)
+	}
+
 	cfg.show()
 
 	return cfg