secrets as environment variables. closes bitly#5

Author: Kevin Lamontagne

README.md

@@ -96,7 +96,9 @@ The command line to run `google_auth_proxy` would look like this:
    --client-secret=...
 ```
 
+## Environment variables
 
+The environment variables `google_auth_client_id`, `google_auth_secret` and `google_auth_cookie_secret` can be used in place of the corresponding command-line arguments.
 
 ## Endpoint Documentation
 

main.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"log"
 	"net"
+	"os"
 	"net/http"
 	"net/url"
 	"strings"
@@ -32,8 +33,20 @@ func init() {
 }
 
 func main() {
+
 	flag.Parse()
 
+	// Try to use env for secrets if no flag is set
+	if *clientID == "" {
+		*clientID = os.Getenv("google_auth_client_id")
+	}
+	if *clientSecret == "" {
+		*clientSecret = os.Getenv("google_auth_secret")
+	}
+	if *cookieSecret == "" {
+		*cookieSecret = os.Getenv("google_auth_cookie_secret")
+	}
+
 	if *showVersion {
 		fmt.Printf("google_auth_proxy v%s\n", VERSION)
 		return