Resolve build failiures when selinux is enabled (#1927)

libs/users/src/lib.rs

@@ -1,4 +1,8 @@
+use libc::passwd as c_passwd;
 use libc::{gid_t, uid_t};
+use std::ffi::{CStr, OsStr, OsString};
+use std::os::unix::ffi::OsStrExt;
+use std::{mem, ptr};
 
 pub fn get_current_uid() -> uid_t {
     unsafe { libc::getuid() }
@@ -15,3 +19,41 @@ pub fn get_current_gid() -> gid_t {
 pub fn get_effective_gid() -> gid_t {
     unsafe { libc::getegid() }
 }
+
+pub fn get_user_name_by_uid(uid: uid_t) -> Option<OsString> {
+    let mut passwd = unsafe { mem::zeroed::<c_passwd>() };
+    let mut buf = vec![0; 2048];
+    let mut result = ptr::null_mut::<c_passwd>();
+
+    #[cfg(feature = "logging")]
+    trace!("Running getpwuid_r for user #{}", uid);
+
+    loop {
+        let r =
+            unsafe { libc::getpwuid_r(uid, &mut passwd, buf.as_mut_ptr(), buf.len(), &mut result) };
+
+        if r != libc::ERANGE {
+            break;
+        }
+
+        let newsize = buf.len().checked_mul(2)?;
+        buf.resize(newsize, 0);
+    }
+
+    if result.is_null() {
+        // There is no such user, or an error has occurred.
+        // errno gets set if there’s an error.
+        return None;
+    }
+
+    if result != &mut passwd {
+        // The result of getpwuid_r should be its input passwd.
+        return None;
+    }
+
+    let name = unsafe {
+        OsStr::from_bytes(CStr::from_ptr(result.read().pw_name).to_bytes()).to_os_string()
+    };
+
+    Some(name)
+}

unix_integration/src/selinux_util.rs

@@ -1,7 +1,7 @@
+use kanidm_utils_users::get_user_name_by_uid;
 use std::ffi::CString;
 use std::path::Path;
 use std::process::Command;
-use users::get_user_by_uid;
 
 use selinux::{
     current_mode, kernel_support, label::back_end::File, label::Labeler, KernelSupport,
@@ -63,8 +63,8 @@ impl SelinuxLabeler {
         // so that relabels in the future do not break it.
         #[cfg(all(target_family = "unix", feature = "selinux"))]
         // Yes, gid, because we use the GID number for both the user's UID and primary GID
-        let sel_lookup_path_raw = match get_user_by_uid(gid) {
-            Some(v) => format!("{}{}", home_prefix, v.name().to_str().unwrap()),
+        let sel_lookup_path_raw = match get_user_name_by_uid(gid) {
+            Some(v) => format!("{}{}", home_prefix, v.to_str().unwrap()),
             None => {
                 return Err("Failed looking up username by uid for SELinux relabeling".to_string());
             }