liminal-server 0.25.4

Standalone server for the liminal messaging bus
Documentation 
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//! Resolve each canonical component through a held directory descriptor.

use crate::services::lifecycle::site::SiteError;
use rustix::fs::{Mode, OFlags, open, openat};
use std::path::{Component, Path};

/// A renamed parent or swapped symlink must refuse rather than redirect the
/// approved canonical path. Nonblocking open prevents a swapped FIFO from
/// holding admission; the caller checks the opened descriptor is regular.
pub(in super::super) fn open_command(path: &Path) -> Result<std::fs::File, SiteError> {
    let flags = OFlags::RDONLY | OFlags::CLOEXEC | OFlags::NOFOLLOW;
    let mut directory = open("/", flags | OFlags::DIRECTORY, Mode::empty())
        .map_err(|_| SiteError::Invalid("template root descriptor"))?;
    let mut components = path.components().peekable();
    if components.next() != Some(Component::RootDir) {
        return Err(SiteError::Invalid("template canonical path"));
    }
    while let Some(component) = components.next() {
        let Component::Normal(name) = component else {
            return Err(SiteError::Invalid("template canonical component"));
        };
        if components.peek().is_none() {
            return openat(&directory, name, flags | OFlags::NONBLOCK, Mode::empty())
                .map(std::fs::File::from)
                .map_err(|_| SiteError::Invalid("template command read"));
        }
        directory = openat(&directory, name, flags | OFlags::DIRECTORY, Mode::empty())
            .map_err(|_| SiteError::Invalid("template command directory"))?;
    }
    Err(SiteError::Invalid("template command path"))
}