view rust/hg-core/src/checkexec.rs @ 51502:a5d8f261b716 stable

obsutil: sort metadata before comparing in geteffectflag()

This is probably less important now that we dropped Python 2. We do still
support Python 3.6 though, and the dictionaries aren't ordered there either
(that was a big change that came with 3.7).

Still, maybe it's a good idea to sort metadata explicitly.

use std::fs;
use std::io;
use std::os::unix::fs::{MetadataExt, PermissionsExt};
use std::path::Path;

const EXECFLAGS: u32 = 0o111;

fn is_executable(path: impl AsRef<Path>) -> Result<bool, io::Error> {
    let metadata = fs::metadata(path)?;
    let mode = metadata.mode();
    Ok(mode & EXECFLAGS != 0)
}

fn make_executable(path: impl AsRef<Path>) -> Result<(), io::Error> {
    let mode = fs::metadata(path.as_ref())?.mode();
    fs::set_permissions(
        path,
        fs::Permissions::from_mode((mode & 0o777) | EXECFLAGS),
    )?;
    Ok(())
}

fn copy_mode(
    src: impl AsRef<Path>,
    dst: impl AsRef<Path>,
) -> Result<(), io::Error> {
    let mode = match fs::symlink_metadata(src) {
        Ok(metadata) => metadata.mode(),
        Err(e) if e.kind() == io::ErrorKind::NotFound =>
        // copymode in python has a more complicated handling of FileNotFound
        // error, which we don't need because all it does is applying
        // umask, which the OS already does when we mkdir.
        {
            return Ok(())
        }
        Err(e) => return Err(e),
    };
    fs::set_permissions(dst, fs::Permissions::from_mode(mode))?;
    Ok(())
}

fn check_exec_impl(path: impl AsRef<Path>) -> Result<bool, io::Error> {
    let basedir = path.as_ref().join(".hg");
    let cachedir = basedir.join("wcache");
    let storedir = basedir.join("store");

    if !cachedir.exists() {
        // we want to create the 'cache' directory, not the '.hg' one.
        // Automatically creating '.hg' directory could silently spawn
        // invalid Mercurial repositories. That seems like a bad idea.
        fs::create_dir(&cachedir)
            .and_then(|()| {
                if storedir.exists() {
                    copy_mode(&storedir, &cachedir)
                } else {
                    copy_mode(&basedir, &cachedir)
                }
            })
            .ok();
    }

    let leave_file: bool;
    let checkdir: &Path;
    let checkisexec = cachedir.join("checkisexec");
    let checknoexec = cachedir.join("checknoexec");
    if cachedir.is_dir() {
        // Check if both files already exist in cache and have correct
        // permissions. if so, we assume that permissions work.
        // If not, we delete the files and try again.
        match is_executable(&checkisexec) {
            Err(e) if e.kind() == io::ErrorKind::NotFound => (),
            Err(e) => return Err(e),
            Ok(is_exec) => {
                if is_exec {
                    let noexec_is_exec = match is_executable(&checknoexec) {
                        Err(e) if e.kind() == io::ErrorKind::NotFound => {
                            fs::write(&checknoexec, "")?;
                            is_executable(&checknoexec)?
                        }
                        Err(e) => return Err(e),
                        Ok(exec) => exec,
                    };
                    if !noexec_is_exec {
                        // check-exec is exec and check-no-exec is not exec
                        return Ok(true);
                    }
                    fs::remove_file(&checknoexec)?;
                }
                fs::remove_file(&checkisexec)?;
            }
        }
        checkdir = &cachedir;
        leave_file = true;
    } else {
        // no cache directory (probably because .hg doesn't exist):
        // check directly in `path` and don't leave the temp file behind
        checkdir = path.as_ref();
        leave_file = false;
    };

    let tmp_file = tempfile::NamedTempFile::new_in(checkdir)?;
    if !is_executable(tmp_file.path())? {
        make_executable(tmp_file.path())?;
        if is_executable(tmp_file.path())? {
            if leave_file {
                tmp_file.persist(checkisexec).ok();
            }
            return Ok(true);
        }
    }

    Ok(false)
}

/// This function is a Rust rewrite of the `checkexec` function from
/// `posix.py`.
///
/// Returns `true` if the filesystem supports execute permissions.
pub fn check_exec(path: impl AsRef<Path>) -> bool {
    check_exec_impl(path).unwrap_or(false)
}