Add ability to drop privileges after binding to port

Cargo.lock

@@ -902,6 +902,7 @@ dependencies = [
  "chrono",
  "config",
  "futures",
+ "libc",
  "libsqlite3-sys",
  "log",
  "serde",

emgauwa-core.toml

@@ -1,6 +1,10 @@
 port = 4419
 host = "127.0.0.1"
 
+# Set to a user AND a group to drop privileges to after binding to the port
+#user = "emgauwa"
+#group = "emgauwa"
+
 # Leave empty to allow all origins (will always respond with Origin and not "*")
 #origins = ["http://localhost", "https://emgauwa.app"]
 

emgauwa-core/src/main.rs

@@ -1,9 +1,11 @@
 use actix_cors::Cors;
+use std::net::TcpListener;
 use std::str::FromStr;
 
 use actix_web::middleware::TrailingSlash;
 use actix_web::{middleware, web, App, HttpServer};
 use emgauwa_lib::handlers;
+use emgauwa_lib::utils::drop_privileges;
 use log::{trace, LevelFilter};
 use simple_logger::SimpleLogger;
 
@@ -22,6 +24,18 @@ async fn main() -> std::io::Result<()> {
 		.init()
 		.expect("Error initializing logger.");
 
+	let listener = TcpListener::bind(format!("{}:{}", settings.host, settings.port))
+		.expect("Error creating listener");
+
+	if !settings.user.is_empty() && !settings.group.is_empty() {
+		log::info!(
+			"Dropping privileges to {}:{}",
+			settings.user,
+			settings.group
+		);
+		drop_privileges(&settings.user, &settings.group).expect("Error dropping privileges");
+	}
+
 	let pool = emgauwa_lib::db::init(&settings.database).await;
 
 	log::info!("Starting server on {}:{}", settings.host, settings.port);
@@ -55,7 +69,7 @@ async fn main() -> std::io::Result<()> {
 			.service(handlers::v1::schedules::delete)
 			.service(handlers::v1::ws::controllers::index)
 	})
-	.bind(format!("{}:{}", settings.host, settings.port))?
+	.listen(listener)?
 	.run()
 	.await
 }

emgauwa-core/src/settings.rs

@@ -14,9 +14,14 @@ pub struct Logging {
 #[allow(unused)]
 pub struct Settings {
 	pub database: String,
-	pub port: u16,
+
 	pub host: String,
+	pub port: u16,
 	pub origins: Vec<String>,
+
+	pub user: String,
+	pub group: String,
+
 	pub logging: Logging,
 }
 
@@ -24,9 +29,14 @@ impl Default for Settings {
 	fn default() -> Self {
 		Settings {
 			database: String::from("sqlite://emgauwa-core.sqlite"),
-			port: constants::DEFAULT_PORT,
+
 			host: String::from("127.0.0.1"),
+			port: constants::DEFAULT_PORT,
 			origins: Vec::new(),
+
+			user: String::from(""),
+			group: String::from(""),
+
 			logging: Logging::default(),
 		}
 	}

emgauwa-lib/Cargo.toml

@@ -24,3 +24,4 @@ libsqlite3-sys = { version = "*", features = ["bundled"] }
 log = "0.4"
 uuid = "1.6"
 futures = "0.3"
+libc = "0.2"

emgauwa-lib/src/handlers/v1/ws/controllers.rs

@@ -6,7 +6,6 @@ use actix::{Actor, StreamHandler};
 use actix_web::{get, web, HttpRequest, HttpResponse};
 use actix_web_actors::ws;
 use actix_web_actors::ws::ProtocolError;
-use futures::FutureExt;
 use serde_derive::{Deserialize, Serialize};
 use sqlx::pool::PoolConnection;
 use sqlx::{Pool, Sqlite};

emgauwa-lib/src/utils.rs

@@ -1,3 +1,6 @@
+use std::ffi::CString;
+use std::io::{Error, ErrorKind};
+
 pub fn load_settings<T>(config_name: &str, env_prefix: &str) -> T
 where
 	for<'de> T: serde::Deserialize<'de>,
@@ -16,3 +19,46 @@ where
 		.try_deserialize::<T>()
 		.expect("Error reading settings")
 }
+
+// https://blog.lxsang.me/post/id/28.0
+pub fn drop_privileges(user: &str, group: &str) -> Result<(), Error> {
+	// the group id need to be set first, otherwise,
+	// when the user privileges drop, it is unable to
+	// drop the group privileges
+	// get the gid from username
+	if let Ok(cstr) = CString::new(group.as_bytes()) {
+		let p = unsafe { libc::getgrnam(cstr.as_ptr()) };
+		if p.is_null() {
+			eprintln!("Unable to getgrnam of group: {}", group);
+			return Err(Error::last_os_error());
+		}
+		if unsafe { libc::setgid((*p).gr_gid) } != 0 {
+			eprintln!("Unable to setgid of group: {}", group);
+			return Err(Error::last_os_error());
+		}
+	} else {
+		return Err(Error::new(
+			ErrorKind::Other,
+			"Cannot create CString from String (group)!",
+		));
+	}
+	// drop the user privileges
+	// get the uid from username
+	if let Ok(cstr) = CString::new(user.as_bytes()) {
+		let p = unsafe { libc::getpwnam(cstr.as_ptr()) };
+		if p.is_null() {
+			eprintln!("Unable to getpwnam of user: {}", user);
+			return Err(Error::last_os_error());
+		}
+		if unsafe { libc::setuid((*p).pw_uid) } != 0 {
+			eprintln!("Unable to setuid of user: {}", user);
+			return Err(Error::last_os_error());
+		}
+	} else {
+		return Err(Error::new(
+			ErrorKind::Other,
+			"Cannot create CString from String (user)!",
+		));
+	}
+	Ok(())
+}