Merge pull request #12 from keithduncan/add-env-var-support

Add support for reading SSH_AUTH_SOCK environment variable

Author: keithduncan

agent/src/main.rs

@@ -1,4 +1,4 @@
-use std::{fs, path::Path};
+use std::{env, fs, path::Path};
 use ssh_agent::agent::Agent;
 use clap::{App, Arg, SubCommand};
 use url::Url;
@@ -23,19 +23,18 @@ fn main() {
 		.subcommand(SubCommand::with_name("list-keys")
 			.about("List all keys for the caller's IAM identity."))
 		.subcommand(SubCommand::with_name("daemon")
-			.about("Run the daemon, bind a UNIX domain socket to provide ssh list and sign operations.")
+			.about("Run the daemon, bind a UNIX domain socket to provide ssh list and sign operations. Defaults to SSH_AUTH_SOCK if unspecified.")
 			.arg(Arg::with_name("bind-to")
 				.long("bind-to")
 				.short("b")
 				.takes_value(true)
-				.value_name("PATH")
-				.required(true)))
+				.value_name("PATH")))
 		.setting(clap::AppSettings::SubcommandRequired)
 		.get_matches();
 
 	// Uses an environment variable rather than an argument so that this can be
 	// an ECS ValueFrom in an ECS task.
-	let ssh_agent_backend_url = Url::parse(&std::env::var("IAM_SSH_AGENT_BACKEND_URL").expect("IAM_SSH_AGENT_BACKEND_URL is required")).expect("IAM_SSH_AGENT_BACKEND_URL is a valid url");
+	let ssh_agent_backend_url = Url::parse(&env::var("IAM_SSH_AGENT_BACKEND_URL").expect("IAM_SSH_AGENT_BACKEND_URL is required")).expect("IAM_SSH_AGENT_BACKEND_URL is a valid url");
 	let agent = agent::Backend::new(ssh_agent_backend_url);
 
 	if let Some(_matches) = matches.subcommand_matches("list-keys") {
@@ -46,8 +45,10 @@ fn main() {
 	if let Some(matches) = matches.subcommand_matches("daemon") {
 		// TODO support exec mode and export SSH_AUTH_SOCK
 
-		let pipe = matches.value_of("bind-to").expect("bind-to is required");
-        let pipe = Path::new(pipe);
+		// Support command line for testing and an environment variable for
+		// systemd units.
+		let pipe: String = matches.value_of("bind-to").map(str::to_string).or(env::var("SSH_AUTH_SOCK").ok()).expect("bind-to is required");
+        let pipe = Path::new(&pipe);
 
         if fs::metadata(&pipe).is_ok() {
             if let Ok(_) = fs::remove_file(&pipe){