lucet-wasi-wasmsbx/src/fdentry.rs

use crate::host;
use std::fs::File;
use std::os::unix::prelude::{FileTypeExt, FromRawFd, IntoRawFd, RawFd};
use std::path::PathBuf;

#[derive(Debug)]
pub struct FdEntry {
    pub fd_object: FdObject,
    pub rights_base: host::__wasi_rights_t,
    pub rights_inheriting: host::__wasi_rights_t,
    pub preopen_path: Option<PathBuf>,
}

impl FdEntry {
    pub fn from_file(file: File) -> FdEntry {
        unsafe { FdEntry::from_raw_fd(file.into_raw_fd()) }
    }
    pub unsafe fn from_raw_fd_for_io_desc(rawfd: RawFd, writable : bool) -> FdEntry {
        let (ty, mut rights_base, rights_inheriting) =
        (
            host::__WASI_FILETYPE_CHARACTER_DEVICE,
            host::RIGHTS_TTY_BASE,
            host::RIGHTS_TTY_BASE,
        );

        if !writable {
            rights_base &= !host::__WASI_RIGHT_FD_WRITE as host::__wasi_rights_t;
        } else {
            rights_base &= !host::__WASI_RIGHT_FD_READ as host::__wasi_rights_t;
        }

        FdEntry {
            fd_object: FdObject {
                ty: ty as u8,
                rawfd,
                needs_close: true,
            },
            rights_base,
            rights_inheriting,
            preopen_path: None,
        }
    }

}

impl FromRawFd for FdEntry {
    // TODO: make this a different function with error handling, rather than using the trait method
    unsafe fn from_raw_fd(rawfd: RawFd) -> FdEntry {
        let (ty, mut rights_base, rights_inheriting) =
            determine_type_rights(rawfd).expect("can determine file rights");

        use nix::fcntl::{fcntl, OFlag, F_GETFL};
        let flags_bits = fcntl(rawfd, F_GETFL).expect("fcntl succeeds");
        let flags = OFlag::from_bits_truncate(flags_bits);
        let accmode = flags & OFlag::O_ACCMODE;
        if accmode == OFlag::O_RDONLY {
            rights_base &= !host::__WASI_RIGHT_FD_WRITE as host::__wasi_rights_t;
        } else if accmode == OFlag::O_WRONLY {
            rights_base &= !host::__WASI_RIGHT_FD_READ as host::__wasi_rights_t;
        }

        FdEntry {
            fd_object: FdObject {
                ty: ty as u8,
                rawfd,
                needs_close: true,
            },
            rights_base,
            rights_inheriting,
            preopen_path: None,
        }
    }
}

// TODO: can probably make this safe by using fcntl directly rather than going through `File`
pub unsafe fn determine_type_rights(
    rawfd: RawFd,
) -> Result<
    (
        host::__wasi_filetype_t,
        host::__wasi_rights_t,
        host::__wasi_rights_t,
    ),
    host::__wasi_errno_t,
> {
    let (ty, rights_base, rights_inheriting) = {
        let file = File::from_raw_fd(rawfd);
        let ft = file.metadata().unwrap().file_type();
        // we just make a `File` here for convenience; we don't want it to close when it drops
        std::mem::forget(file);
        if ft.is_block_device() {
            (
                host::__WASI_FILETYPE_BLOCK_DEVICE,
                host::RIGHTS_BLOCK_DEVICE_BASE,
                host::RIGHTS_BLOCK_DEVICE_INHERITING,
            )
        } else if ft.is_char_device() {
            if nix::unistd::isatty(rawfd).unwrap() {
                (
                    host::__WASI_FILETYPE_CHARACTER_DEVICE,
                    host::RIGHTS_TTY_BASE,
                    host::RIGHTS_TTY_BASE,
                )
            } else {
                (
                    host::__WASI_FILETYPE_CHARACTER_DEVICE,
                    host::RIGHTS_CHARACTER_DEVICE_BASE,
                    host::RIGHTS_CHARACTER_DEVICE_INHERITING,
                )
            }
        } else if ft.is_dir() {
            (
                host::__WASI_FILETYPE_DIRECTORY,
                host::RIGHTS_DIRECTORY_BASE,
                host::RIGHTS_DIRECTORY_INHERITING,
            )
        } else if ft.is_file() {
            (
                host::__WASI_FILETYPE_REGULAR_FILE,
                host::RIGHTS_REGULAR_FILE_BASE,
                host::RIGHTS_REGULAR_FILE_INHERITING,
            )
        // } else if ft.is_socket() {
        //     use nix::sys::socket;
        //     match socket::getsockopt(rawfd, socket::sockopt::SockType).unwrap() {
        //         socket::SockType::Datagram => (
        //             host::__WASI_FILETYPE_SOCKET_DGRAM,
        //             host::RIGHTS_SOCKET_BASE,
        //             host::RIGHTS_SOCKET_INHERITING,
        //         ),
        //         socket::SockType::Stream => (
        //             host::__WASI_FILETYPE_SOCKET_STREAM,
        //             host::RIGHTS_SOCKET_BASE,
        //             host::RIGHTS_SOCKET_INHERITING,
        //         ),
        //         _ => return Err(host::__WASI_EINVAL as host::__wasi_errno_t),
        //     }
        } else if ft.is_fifo() {
            (
                host::__WASI_FILETYPE_SOCKET_STREAM,
                host::RIGHTS_SOCKET_BASE,
                host::RIGHTS_SOCKET_INHERITING,
            )
        } else {
            return Err(host::__WASI_EINVAL as host::__wasi_errno_t);
        }
    };
    Ok((
        ty as host::__wasi_filetype_t,
        rights_base,
        rights_inheriting,
    ))
}

#[derive(Debug)]
pub struct FdObject {
    pub ty: host::__wasi_filetype_t,
    pub rawfd: RawFd,
    pub needs_close: bool,
    // TODO: directories
}

impl Drop for FdObject {
    fn drop(&mut self) {
        if self.needs_close {
            nix::unistd::close(self.rawfd).unwrap_or_else(|e| eprintln!("FdObject::drop(): {}", e));
        }
    }
}