chroot: implement --skip-chdir

src/uu/chroot/src/chroot.rs

@@ -6,14 +6,14 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 
-// spell-checker:ignore (ToDO) NEWROOT Userspec pstatus
+// spell-checker:ignore (ToDO) NEWROOT Userspec pstatus chdir
 mod error;
 
 use crate::error::ChrootError;
 use clap::{crate_version, Arg, Command};
 use std::ffi::CString;
 use std::io::Error;
-use std::path::Path;
+use std::path::{Path, PathBuf};
 use std::process;
 use uucore::error::{set_exit_code, UClapError, UResult};
 use uucore::libc::{self, chroot, setgid, setgroups, setuid};
@@ -29,6 +29,7 @@ mod options {
     pub const GROUPS: &str = "groups";
     pub const USERSPEC: &str = "userspec";
     pub const COMMAND: &str = "command";
+    pub const SKIP_CHDIR: &str = "skip-chdir";
 }
 
 #[uucore::main]
@@ -143,6 +144,15 @@ pub fn uu_app<'a>() -> Command<'a> {
                 )
                 .value_name("USER:GROUP"),
         )
+        .arg(
+            Arg::new(options::SKIP_CHDIR)
+                .long(options::SKIP_CHDIR)
+                .help(
+                    "Use this option to not change the working directory \
+                    to / after changing the root directory to newroot, \
+                    i.e., inside the chroot.",
+                ),
+        )
         .arg(
             Arg::new(options::COMMAND)
                 .value_hint(clap::ValueHint::CommandName)
@@ -157,6 +167,7 @@ fn set_context(root: &Path, options: &clap::ArgMatches) -> UResult<()> {
     let user_str = options.value_of(options::USER).unwrap_or_default();
     let group_str = options.value_of(options::GROUP).unwrap_or_default();
     let groups_str = options.value_of(options::GROUPS).unwrap_or_default();
+    let skip_chdir = options.contains_id(options::SKIP_CHDIR);
     let userspec = match userspec_str {
         Some(u) => {
             let s: Vec<&str> = u.split(':').collect();
@@ -174,20 +185,35 @@ fn set_context(root: &Path, options: &clap::ArgMatches) -> UResult<()> {
         (userspec[0], userspec[1])
     };
 
-    enter_chroot(root)?;
+    enter_chroot(root, skip_chdir)?;
 
     set_groups_from_str(groups_str)?;
     set_main_group(group)?;
     set_user(user)?;
     Ok(())
 }
 
-fn enter_chroot(root: &Path) -> UResult<()> {
+fn enter_chroot(root: &Path, skip_chdir: bool) -> UResult<()> {
+    let cwd = if skip_chdir {
+        // We want to keep the current working directory
+        // So, we store the current path
+        std::env::current_dir().unwrap()
+    } else {
+        // Empty path, we won't use it
+        PathBuf::from("")
+    };
+
     std::env::set_current_dir(root).unwrap();
     let err = unsafe {
         chroot(CString::new(".").unwrap().as_bytes_with_nul().as_ptr() as *const libc::c_char)
     };
     if err == 0 {
+        // We have successful chroot
+        // Set the previous path back
+        if skip_chdir {
+            std::env::set_current_dir(cwd).unwrap();
+        }
+
         Ok(())
     } else {
         Err(ChrootError::CannotEnter(format!("{}", root.display()), Error::last_os_error()).into())

tests/by-util/test_chroot.rs

@@ -1,4 +1,4 @@
-// spell-checker:ignore (words) araba newroot userspec
+// spell-checker:ignore (words) araba newroot userspec chdir
 
 use crate::common::util::*;
 
@@ -143,3 +143,22 @@ fn test_chroot() {
         print!("Test skipped; requires root user");
     }
 }
+
+#[test]
+fn test_chroot_skip_chdir() {
+    let ts = TestScenario::new(util_name!());
+    let at = &ts.fixtures;
+
+    let dir = "CHROOT_DIR";
+    at.mkdir(dir);
+    let env_cd = std::env::current_dir().unwrap();
+    if let Ok(result) = run_ucmd_as_root(&ts, &[dir, "--skip-chdir", "pwd"]) {
+        // Should return the same path
+        assert_eq!(
+            result.success().no_stderr().stdout_str(),
+            env_cd.to_str().unwrap()
+        );
+    } else {
+        print!("Test skipped; requires root user");
+    }
+}