rustjail: get home dir using nix crate

Get user's home dir using `nix::unistd` crate instead of `utils` crate,
and remove useless code from agent.

Fixes: #4209

Signed-off-by: Xuewei Niu <justxuewei@apache.org>

src/agent/rustjail/src/container.rs

@@ -42,7 +42,7 @@ use nix::pty;
 use nix::sched::{self, CloneFlags};
 use nix::sys::signal::{self, Signal};
 use nix::sys::stat::{self, Mode};
-use nix::unistd::{self, fork, ForkResult, Gid, Pid, Uid};
+use nix::unistd::{self, fork, ForkResult, Gid, Pid, Uid, User};
 use std::os::unix::fs::MetadataExt;
 use std::os::unix::io::AsRawFd;
 
@@ -64,8 +64,6 @@ use rlimit::{setrlimit, Resource, Rlim};
 use tokio::io::AsyncBufReadExt;
 use tokio::sync::Mutex;
 
-use crate::utils;
-
 pub const EXEC_FIFO_FILENAME: &str = "exec.fifo";
 
 const INIT: &str = "INIT";
@@ -665,12 +663,17 @@ fn do_init_child(cwfd: RawFd) -> Result<()> {
         }
     }
 
-    // set the "HOME" env getting from "/etc/passwd", if
-    // there's no uid entry in /etc/passwd, set "/" as the
-    // home env.
     if env::var_os(HOME_ENV_KEY).is_none() {
-        let home_dir = utils::home_dir(guser.uid).unwrap_or_else(|_| String::from("/"));
+        // try to set "HOME" env by uid
-        env::set_var(HOME_ENV_KEY, home_dir);
+        if let Ok(Some(user)) = User::from_uid(Uid::from_raw(guser.uid)) {
+            if let Ok(user_home_dir) = user.dir.into_os_string().into_string() {
+                env::set_var(HOME_ENV_KEY, user_home_dir);
+            }
+        }
+        // set default home dir as "/" if "HOME" env is still empty
+        if env::var_os(HOME_ENV_KEY).is_none() {
+            env::set_var(HOME_ENV_KEY, String::from("/"));
+        }
     }
 
     let exec_file = Path::new(&args[0]);

src/agent/rustjail/src/lib.rs

@@ -41,7 +41,6 @@ pub mod seccomp;
 pub mod specconv;
 pub mod sync;
 pub mod sync_with_async;
-pub mod utils;
 pub mod validator;
 
 use std::collections::HashMap;

src/agent/rustjail/src/utils.rs

@@ -1,120 +0,0 @@
-// Copyright (c) 2021 Ant Group
-//
-// SPDX-License-Identifier: Apache-2.0
-//
-use anyhow::{anyhow, Context, Result};
-use libc::gid_t;
-use libc::uid_t;
-use std::fs::File;
-use std::io::{BufRead, BufReader};
-
-const PASSWD_FILE: &str = "/etc/passwd";
-
-// An entry from /etc/passwd
-#[derive(Debug, PartialEq, PartialOrd)]
-pub struct PasswdEntry {
-    // username
-    pub name: String,
-    // user password
-    pub passwd: String,
-    // user id
-    pub uid: uid_t,
-    // group id
-    pub gid: gid_t,
-    // user Information
-    pub gecos: String,
-    // home directory
-    pub dir: String,
-    // User's Shell
-    pub shell: String,
-}
-
-// get an entry for a given `uid` from `/etc/passwd`
-fn get_entry_by_uid(uid: uid_t, path: &str) -> Result<PasswdEntry> {
-    let file = File::open(path).with_context(|| format!("open file {}", path))?;
-    let mut reader = BufReader::new(file);
-
-    let mut line = String::new();
-    loop {
-        line.clear();
-        match reader.read_line(&mut line) {
-            Ok(0) => return Err(anyhow!(format!("file {} is empty", path))),
-            Ok(_) => (),
-            Err(e) => {
-                return Err(anyhow!(format!(
-                    "failed to read file {} with {:?}",
-                    path, e
-                )))
-            }
-        }
-
-        if line.starts_with('#') {
-            continue;
-        }
-
-        let parts: Vec<&str> = line.split(':').map(|part| part.trim()).collect();
-        if parts.len() != 7 {
-            continue;
-        }
-
-        match parts[2].parse() {
-            Err(_e) => continue,
-            Ok(new_uid) => {
-                if uid != new_uid {
-                    continue;
-                }
-
-                let entry = PasswdEntry {
-                    name: parts[0].to_string(),
-                    passwd: parts[1].to_string(),
-                    uid: new_uid,
-                    gid: parts[3].parse().unwrap_or(0),
-                    gecos: parts[4].to_string(),
-                    dir: parts[5].to_string(),
-                    shell: parts[6].to_string(),
-                };
-
-                return Ok(entry);
-            }
-        }
-    }
-}
-
-pub fn home_dir(uid: uid_t) -> Result<String> {
-    get_entry_by_uid(uid, PASSWD_FILE).map(|entry| entry.dir)
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use std::io::Write;
-    use tempfile::Builder;
-
-    #[test]
-    fn test_get_entry_by_uid() {
-        let tmpdir = Builder::new().tempdir().unwrap();
-        let tmpdir_path = tmpdir.path().to_str().unwrap();
-        let temp_passwd = format!("{}/passwd", tmpdir_path);
-
-        let mut tempf = File::create(temp_passwd.as_str()).unwrap();
-        let passwd_entries = "root:x:0:0:root:/root0:/bin/bash
-root:x:1:0:root:/root1:/bin/bash
-#root:x:1:0:root:/rootx:/bin/bash
-root:x:2:0:root:/root2:/bin/bash
-root:x:3:0:root:/root3
-root:x:3:0:root:/root3:/bin/bash";
-        writeln!(tempf, "{}", passwd_entries).unwrap();
-
-        let entry = get_entry_by_uid(0, temp_passwd.as_str()).unwrap();
-        assert_eq!(entry.dir.as_str(), "/root0");
-
-        let entry = get_entry_by_uid(1, temp_passwd.as_str()).unwrap();
-        assert_eq!(entry.dir.as_str(), "/root1");
-
-        let entry = get_entry_by_uid(2, temp_passwd.as_str()).unwrap();
-        assert_eq!(entry.dir.as_str(), "/root2");
-
-        let entry = get_entry_by_uid(3, temp_passwd.as_str()).unwrap();
-        assert_eq!(entry.dir.as_str(), "/root3");
-    }
-}