Add ability to drop privileges after binding to port

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(())
+}