Refactor drop privileges method

emgauwa-core/Cargo.toml

@@ -23,3 +23,4 @@ serde_json = "1.0"
 serde_derive = "1.0"
 
 futures = "0.3.29"
+libc = "0.2"

emgauwa-core/src/main.rs

@@ -2,14 +2,15 @@ use actix_cors::Cors;
 use std::net::TcpListener;
 use std::str::FromStr;
 
+use crate::utils::drop_privileges;
 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;
 
 mod settings;
+mod utils;
 
 #[actix_web::main]
 async fn main() -> std::io::Result<()> {
@@ -27,23 +28,13 @@ async fn main() -> std::io::Result<()> {
 	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");
-	}
+	drop_privileges(&settings).expect("Error dropping privileges");
 
 	let pool = emgauwa_lib::db::init(&settings.database).await;
 
 	log::info!("Starting server on {}:{}", settings.host, settings.port);
 	HttpServer::new(move || {
-		let cors = Cors::default()
-			.allow_any_method()
-			.allow_any_header()
-			.max_age(3600);
+		let cors = Cors::default().allow_any_method().allow_any_header();
 
 		let origins = settings.origins.clone();
 		let cors = match settings.origins.is_empty() {

emgauwa-core/src/utils.rs

@@ -0,0 +1,64 @@
+use crate::settings::Settings;
+use std::ffi::CString;
+use std::io::{Error, ErrorKind};
+
+// https://blog.lxsang.me/post/id/28.0
+pub fn drop_privileges(settings: &Settings) -> Result<(), Error> {
+	log::info!(
+		"Dropping privileges to {}:{}",
+		settings.user,
+		settings.group
+	);
+
+	// the group id need to be set first, because, when the user privileges drop,
+	// we are unable to drop the group privileges
+	if !settings.group.is_empty() {
+		drop_privileges_group(&settings.group)?;
+	}
+	if !settings.user.is_empty() {
+		drop_privileges_user(&settings.user)?;
+	}
+	Ok(())
+}
+
+fn drop_privileges_group(group: &str) -> Result<(), Error> {
+	// 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)!",
+		));
+	}
+	Ok(())
+}
+
+fn drop_privileges_user(user: &str) -> Result<(), Error> {
+	// 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(())
+}