cap_primitives/rustix/linux/fs/
stat_impl.rs

1//! Linux has an `O_PATH` flag which allows opening a file without necessary
2//! having read or write access to it; we can use that with `openat2` and
3//! `fstat` to perform a fast sandboxed `stat`.
4
5use super::file_metadata::file_metadata;
6use crate::fs::{manually, open_beneath, FollowSymlinks, Metadata, OpenOptions};
7use rustix::fs::OFlags;
8use std::path::Path;
9use std::{fs, io};
10
11/// Use `openat2` with `O_PATH` and `fstat`. If that's not available, fallback
12/// to `manually::stat`.
13pub(crate) fn stat_impl(
14    start: &fs::File,
15    path: &Path,
16    follow: FollowSymlinks,
17) -> io::Result<Metadata> {
18    use crate::fs::{stat_unchecked, OpenOptionsExt};
19    use std::path::Component;
20
21    // Optimization: if path has exactly one component and it's not ".." or
22    // anything non-normal and we're not following symlinks we can go straight
23    // to `stat_unchecked`, which is faster than doing an open with a separate
24    // `fstat`.
25    if follow == FollowSymlinks::No {
26        let mut components = path.components();
27        if let Some(Component::Normal(component)) = components.next() {
28            if components.next().is_none() {
29                return stat_unchecked(start, component.as_ref(), FollowSymlinks::No);
30            }
31        }
32    }
33
34    // Open the path with `O_PATH`. Use `read(true)` even though we don't need
35    // `read` permissions, because Rust's libstd requires an access mode, and
36    // Linux ignores `O_RDONLY` with `O_PATH`.
37    let result = open_beneath(
38        start,
39        path,
40        OpenOptions::new()
41            .read(true)
42            .follow(follow)
43            .custom_flags(OFlags::PATH.bits() as i32),
44    );
45
46    // If that worked, call `fstat`.
47    match result {
48        Ok(file) => file_metadata(&file),
49        Err(err) => match rustix::io::Errno::from_io_error(&err) {
50            // `ENOSYS` from `open_beneath` means `openat2` is unavailable
51            // and we should use a fallback.
52            Some(rustix::io::Errno::NOSYS) => manually::stat(start, path, follow),
53            _ => Err(err),
54        },
55    }
56}
cap_primitives/rustix/linux/fs/stat_impl.rs

cap_primitives/rustix/linux/fs/
stat_impl.rs
