id: fix group loading; still a WIP

plib/src/group.rs

@@ -0,0 +1,71 @@
+//
+// Copyright (c) 2024 Jeff Garzik
+//
+// This file is part of the posixutils-rs project covered under
+// the MIT License.  For the full license text, please see the LICENSE
+// file in the root directory of this project.
+// SPDX-License-Identifier: MIT
+//
+
+extern crate libc;
+use libc::{endgrent, getgrent, setgrent};
+use std::ffi::CStr;
+use std::ptr;
+
+pub struct Group {
+    pub name: String,
+    pub passwd: String,
+    pub gid: libc::gid_t,
+    pub members: Vec<String>,
+}
+
+pub fn load() -> Vec<Group> {
+    let mut groups = Vec::new();
+
+    unsafe {
+        setgrent(); // Initialize the group entry stream
+        let mut groupent = getgrent(); // Get the first group entry
+
+        // Loop through all group entries
+        while !groupent.is_null() {
+            let group = &*groupent;
+
+            // copy basic group fields: name, passwd, gid
+            let name = CStr::from_ptr(group.gr_name).to_string_lossy().to_string();
+            let passwd = CStr::from_ptr(group.gr_passwd)
+                .to_string_lossy()
+                .to_string();
+            let gid = group.gr_gid;
+
+            // copy group members, a null-terminated array of C strings
+            let mut members = Vec::new();
+            if !group.gr_mem.is_null() {
+                let mut member_ptr_arr = group.gr_mem;
+
+                // Loop through all group members
+                // read_unaligned is necessary on MacOS, possibly
+                // other platforms, to avoid alignment issues
+                while !ptr::read_unaligned(member_ptr_arr).is_null() {
+                    let member_ptr = ptr::read_unaligned(member_ptr_arr);
+                    let member = CStr::from_ptr(member_ptr).to_string_lossy().to_string();
+                    members.push(member);
+                    member_ptr_arr = member_ptr_arr.add(1);
+                }
+            }
+
+            // Add the group to the returned list of groups
+            groups.push(Group {
+                name,
+                passwd,
+                gid,
+                members,
+            });
+
+            groupent = getgrent(); // Move to the next group entry
+        }
+
+        endgrent(); // Close the group entry stream
+    }
+
+    groups
+}

plib/src/lib.rs

@@ -10,6 +10,7 @@
 use std::io::Write;
 use std::process::{Command, Stdio};
 
+pub mod group;
 pub mod modestr;
 
 pub const PROJECT_NAME: &'static str = "posixutils-rs";

users/src/id.rs

@@ -125,35 +125,25 @@ fn get_user_info(args: &Args) -> Result<UserInfo, Box<dyn std::error::Error>> {
     Ok(userinfo)
 }
 
-fn load_group_db() -> Vec<libc::group> {
-    let mut groups = Vec::new();
-
-    unsafe { libc::setgrent() };
-
-    loop {
-        let group = unsafe { libc::getgrent() };
-        if group.is_null() {
-            break;
-        }
-
-        groups.push(unsafe { *group });
-    }
-
-    unsafe { libc::endgrent() };
-
-    groups
-}
-
 fn get_group_info(userinfo: &mut UserInfo) -> Result<(), Box<dyn std::error::Error>> {
-    let groups = load_group_db();
+    let groups = plib::group::load();
 
     for group in &groups {
-        userinfo.groups.push(group.gr_gid);
-        userinfo.group_names.insert(group.gr_gid, unsafe {
-            std::ffi::CStr::from_ptr(group.gr_name)
-                .to_string_lossy()
-                .to_string()
-        });
+        // skip groups that the user is not a member of
+        let mut found = false;
+        for member in &group.members {
+            if *member == userinfo.username {
+                found = true;
+                break;
+            }
+        }
+        if !found && group.gid != userinfo.gid {
+            continue;
+        }
+
+        // add group to user's group list
+        userinfo.groups.push(group.gid);
+        userinfo.group_names.insert(group.gid, group.name.clone());
     }
 
     Ok(())
@@ -190,7 +180,7 @@ fn display_user_info(args: &Args, userinfo: &UserInfo) {
             userinfo.uid, userinfo.username, userinfo.gid, group_name, userinfo.egid
         );
         for gid in &userinfo.groups {
-            print!("{},", userinfo.group_names[gid]);
+            print!("{}({}),", gid, userinfo.group_names[gid]);
         }
         println!();
         return;