Elimited Daemonize dependency

src/util.rs

@@ -0,0 +1,86 @@
+use std::fmt;
+use std::process::exit;
+
+use libc::{c_char, chdir, chroot, fork, getpwnam, getuid, setgid, setsid, setuid, umask};
+
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone)]
+pub enum DaemonizeError {
+    Fork,
+    SetSession,
+    SetGroup,
+    SetUser,
+    Chroot,
+    Chdir,
+}
+
+impl fmt::Display for DaemonizeError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            DaemonizeError::Fork => "unable to fork",
+            DaemonizeError::SetSession => "unable to create new process session",
+            DaemonizeError::SetGroup => "unable to set group (drop privileges)",
+            DaemonizeError::SetUser => "unable to set user (drop privileges)",
+            DaemonizeError::Chroot => "unable to enter chroot jail",
+            DaemonizeError::Chdir => "failed to change directory",
+        }
+        .fmt(f)
+    }
+}
+
+fn fork_and_exit() -> Result<(), DaemonizeError> {
+    let pid = unsafe { fork() };
+    if pid < 0 {
+        Err(DaemonizeError::Fork)
+    } else if pid == 0 {
+        Ok(())
+    } else {
+        exit(0);
+    }
+}
+
+pub fn daemonize() -> Result<(), DaemonizeError> {
+    // fork from the original parent
+    fork_and_exit()?;
+
+    // avoid killing the child when this parent dies
+    if unsafe { setsid() } < 0 {
+        return Err(DaemonizeError::SetSession);
+    }
+
+    // fork again to create orphan
+    fork_and_exit()
+}
+
+pub fn drop_privileges() -> Result<(), DaemonizeError> {
+    // retrieve nobody's uid & gid
+    let usr = unsafe { getpwnam("nobody\x00".as_ptr() as *const c_char) };
+    if usr.is_null() {
+        return Err(DaemonizeError::SetGroup);
+    }
+
+    // change root directory
+    let uid = unsafe { getuid() };
+    if uid == 0 && unsafe { chroot("/tmp\x00".as_ptr() as *const c_char) } != 0 {
+        return Err(DaemonizeError::Chroot);
+    }
+
+    // set umask for files
+    unsafe { umask(0) };
+
+    // change directory
+    if unsafe { chdir("/\x00".as_ptr() as *const c_char) } != 0 {
+        return Err(DaemonizeError::Chdir);
+    }
+
+    // set group id to nobody
+    if unsafe { setgid((*usr).pw_gid) } != 0 {
+        return Err(DaemonizeError::SetGroup);
+    }
+
+    // set user id to nobody
+    if unsafe { setuid((*usr).pw_uid) } != 0 {
+        Err(DaemonizeError::SetUser)
+    } else {
+        Ok(())
+    }
+}