api.rs - source
Description: Source of the Rust file `src/api.rs`.
Keywords: rust, rustlang, rust-lang

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    //! Low level function mapping for fanotify
    //!

    use crate::types::*;
    use libc::c_void;
    use std::ffi::{CString, OsStr};
    use std::io::Error;
    use std::mem;
    use std::os::unix::ffi::OsStrExt;
    use std::slice;

    #[allow(unused_imports)]
    use crate::flags::*;

    /// Get current platform sizeof of fanotify_event_metadata.
    const FAN_EVENT_METADATA_LEN: usize = mem::size_of::<fanotify_event_metadata>();

    /// Length of memory to be allocated for read buffer
    pub static mut FAN_EVENT_BUFFER_LEN: usize = 250;

    /// Initializes a new fanotify group and returns a
    /// file descriptor for the event queue associated with the group.
    ///
    /// The file descriptor is used in calls to [`fanotify_mark()`] to
    /// specify the files, directories, mounts, or filesystems for which
    /// fanotify events shall be created.  These events are received by
    /// reading from the file descriptor.  Some events are only
    /// informative, indicating that a file has been accessed.  Other
    /// events can be used to determine whether another application is
    /// permitted to access a file or directory.  Permission to access
    /// filesystem objects is granted by writing to the file descriptor.
    ///
    /// Multiple programs may be using the fanotify interface at the same
    /// time to monitor the same files.
    ///
    /// In the current implementation, the number of fanotify groups per
    /// user is limited to 128.  This limit cannot be overridden.
    ///
    /// Calling [`fanotify_init()`] requires the `CAP_SYS_ADMIN` capability.
    /// This constraint might be relaxed in future versions of the API.
    /// Therefore, certain additional capability checks have been
    /// implemented as indicated below.
    ///
    /// The flags argument contains a multi-bit field defining the
    /// notification class of the listening application and further
    /// single bit fields specifying the behavior of the file descriptor.
    ///
    /// If multiple listeners for permission events exist, the
    /// notification class is used to establish the sequence in which the
    /// listeners receive the events.
    ///
    /// # Arguments
    /// * `flags` - Sets the notification group, can be mask of <br>
    ///     * [`FAN_CLASS_PRE_CONTENT`]
    ///     * [`FAN_CLASS_CONTENT`]
    ///     * [`FAN_CLASS_NOTIF`]
    ///
    ///     The following bits can additionally be set in `flags`: <br>
    ///     * [`FAN_CLOEXEC`]
    ///     * [`FAN_NONBLOCK`]
    ///     * [`FAN_UNLIMITED_QUEUE`]
    ///     * [`FAN_UNLIMITED_MARKS`]
    ///     * [`FAN_ENABLE_AUDIT`]
    ///     * [`FAN_REPORT_FID`]
    ///     * [`FAN_REPORT_DIR_FID`]
    ///     * [`FAN_REPORT_NAME`]
    ///     * [`FAN_REPORT_DFID_NAME`]
    /// * `event_f_flags` - Defines the file status flags that
    ///                     will be set on the open file descriptions that are created for
    ///                     fanotify events.  For details of these flags, see the description
    ///                     of the flags values in open(2).  `event_f_flags` includes a multi-
    ///                     bit field for the access mode. This field can take the following
    ///                     values:
    ///     * [`O_RDONLY`]
    ///     * [`O_WRONLY`]
    ///     * [`O_RDWR`]
    ///
    ///     Additional bits can be set in `event_f_flags`.
    ///     * [`O_LARGEFILE`]
    ///     * [`O_CLOEXEC`]
    ///     * [`O_APPEND`]
    ///     * [`O_DSYNC`]
    ///     * [`O_NOATIME`]
    ///     * [`O_NONBLOCK`]
    ///
    /// # Example
    /// This example will panic due to absence of `CAP_SYS_ADMIN` [capabilitity](https://man7.org/linux/man-pages/man7/capabilities.7.html)
    /// ```rust
    /// # #[should_panic]
    /// # use naughtyfy::flags::*;
    /// # use naughtyfy::api::*;
    /// let fd = fanotify_init(FAN_CLASS_NOTIF | FAN_NONBLOCK, O_RDONLY);
    /// ```
    ///
    pub fn fanotify_init(flags: u32, event_f_flags: u32) -> Result<i32, Error> {
        unsafe {
            match libc::fanotify_init(flags, event_f_flags) {
                -1 => Err(Error::last_os_error()),
                fd => Ok(fd),
            }
        }
    }

    /// Converts the implemented types to [`OsStr`] using `as_os_str()` method. <br>
    /// This is *NOT* [`std::path::Path`]
    ///
    /// # Example
    /// ```
    /// # use std::ffi::OsStr;
    /// # pub trait Path {
    /// # fn as_os_str(&self) -> &OsStr;
    /// # }
    /// #
    /// # impl Path for str {
    /// #     fn as_os_str(&self) -> &OsStr {
    /// #         OsStr::new(self)
    /// #     }
    /// # }
    /// let path = std::path::Path::new("/usr/bin");
    /// let ostr = path.as_os_str();
    /// assert_eq!(ostr,"/usr/bin");
    /// ```
    pub trait Path {
        fn as_os_str(&self) -> &OsStr;
    }

    impl Path for std::path::Path {
        fn as_os_str(&self) -> &OsStr {
            self.as_os_str()
        }
    }

    impl Path for str {
        fn as_os_str(&self) -> &OsStr {
            OsStr::new(self)
        }
    }

    impl Path for String {
        fn as_os_str(&self) -> &OsStr {
            OsStr::new(self.as_str())
        }
    }

    /// Adds, removes, or modifies an fanotify mark on a
    /// filesystem object. The caller must have read permission on the
    /// filesystem object that is to be marked.
    ///
    /// # Arguments
    /// * `fanotify_fd` - File descriptor returned by [`fanotify_init()`].
    /// * `flags` - Bit mask describing the modification to perform. <br>
    ///     It must include **exactly one** of the following values:
    ///     * [`FAN_MARK_ADD`]
    ///     * [`FAN_MARK_REMOVE`]
    ///     * [`FAN_MARK_FLUSH`]
    ///
    ///      In addition, zero or more of the following values may be ORed
    ///      into flags:
    ///     * [`FAN_MARK_DONT_FOLLOW`]
    ///     * [`FAN_MARK_ONLYDIR`]
    ///     * [`FAN_MARK_MOUNT`]
    ///     * [`FAN_MARK_FILESYSTEM`]
    ///     * [`FAN_MARK_IGNORED_MASK`]
    ///     * [`FAN_MARK_IGNORED_SURV_MODIFY`]
    /// * `mask` - Which events shall be listened for (or which shall be ignored). <br>
    ///     It is a bit mask composed of the following values:
    ///     * [`FAN_ACCESS`]
    ///     * [`FAN_MODIFY`]
    ///     * [`FAN_CLOSE_WRITE`]
    ///     * [`FAN_CLOSE_NOWRITE`]
    ///     * [`FAN_OPEN`]
    ///     * [`FAN_OPEN_EXEC`]
    ///     * [`FAN_ATTRIB`]
    ///     * [`FAN_CREATE`]
    ///     * [`FAN_DELETE`]
    ///     * [`FAN_DELETE_SELF`]
    ///     * [`FAN_MOVED_FROM`]
    ///     * [`FAN_MOVED_TO`]
    ///     * [`FAN_MOVE_SELF`]
    ///     * [`FAN_OPEN_PERM`]
    ///     * [`FAN_OPEN_EXEC_PERM`]
    ///     * [`FAN_ACCESS_PERM`]
    ///     * [`FAN_ONDIR`]
    ///     * [`FAN_EVENT_ON_CHILD`]
    ///     * [`FAN_CLOSE`]
    ///     * [`FAN_MOVE`]
    /// * `dirfd` - Defines the filesystem object to be marked.
    /// * `path` - Filesystem path of file or diretory.
    ///
    /// The filesystem object to be marked is determined by the file
    /// descriptor dirfd and the pathname specified in path:
    ///
    /// * If pathname is `NULL`, dirfd defines the filesystem object to be
    ///   marked.
    /// * If pathname is `NULL`, and dirfd takes the special value
    ///   `AT_FDCWD`, the current working directory is to be marked.

    /// * If pathname is absolute, it defines the filesystem object to
    ///   be marked, and dirfd is ignored.

    /// * If pathname is relative, and dirfd does not have the value
    ///   `AT_FDCWD`, then the filesystem object to be marked is
    ///   determined by interpreting pathname relative the directory
    ///   referred to by dirfd.

    /// * If pathname is relative, and dirfd has the value `AT_FDCWD`,
    ///   then the filesystem object to be marked is determined by
    ///   interpreting pathname relative to the current working
    ///   directory.
    ///
    /// # Example
    /// This example will panic due to absence of `CAP_SYS_ADMIN` [capabilitity](https://man7.org/linux/man-pages/man7/capabilities.7.html)
    /// ```rust
    /// # #[should_panic]
    /// # fn ex() {
    /// # use naughtyfy::flags::*;
    /// # use naughtyfy::types::*;
    /// # use naughtyfy::api::*;
    /// let fd = fanotify_init(FAN_CLASS_NOTIF, 0).unwrap();
    /// fanotify_mark(fd, FAN_MARK_ADD | FAN_MARK_MOUNT, FAN_ACCESS, libc::AT_FDCWD, "./");
    /// # }
    /// ```
    pub fn fanotify_mark<P: ?Sized + Path>(
        fanotify_fd: i32,
        flags: u32,
        mask: u64,
        dirfd: i32,
        path: &P,
    ) -> Result<(), Error> {
        unsafe {
            let path = CString::new(path.as_os_str().as_bytes())?;
            match libc::fanotify_mark(fanotify_fd, flags, mask, dirfd, path.as_ptr()) {
                0 => Ok(()),
                _ => Err(Error::last_os_error()),
            }
        }
    }

    /// This function ateempts to read from a file descriptor `fanotify_fd`
    /// into a `Vec<fanotify_event_metadata>` and return a Result.
    ///
    /// # Argument
    /// * `fd` - file descriptor returned by [`fanotify_init()`]
    ///
    /// # Example
    /// ```rust
    /// # #[should_panic]
    /// # fn ex() {
    /// # use naughtyfy::flags::*;
    /// # use naughtyfy::types::*;
    /// # use naughtyfy::api::*;
    /// let fd = fanotify_init(FAN_CLASS_NOTIF, 0).unwrap();
    /// fanotify_mark(fd, FAN_MARK_ADD | FAN_MARK_MOUNT, FAN_ACCESS, libc::AT_FDCWD, "./");
    /// let fan_events = fanotify_read(fd);
    /// println!("{fan_events:#?}");
    /// # }
    /// ```
    pub fn fanotify_read(fanotify_fd: i32) -> Result<Vec<fanotify_event_metadata>, Error> {
        let mut vec = Vec::new();
        unsafe {
            let buffer = libc::malloc(FAN_EVENT_METADATA_LEN * FAN_EVENT_BUFFER_LEN);

            // allocation may fail due to limited memory.
            if buffer == libc::PT_NULL as *mut c_void {
                return Err(Error::last_os_error());
            }
            let sizeof = libc::read(
                fanotify_fd,
                buffer,
                FAN_EVENT_METADATA_LEN * FAN_EVENT_BUFFER_LEN,
            );
            if sizeof != libc::EAGAIN as isize && sizeof > 0 {
                let src = slice::from_raw_parts(
                    buffer as *mut fanotify_event_metadata,
                    sizeof as usize / FAN_EVENT_METADATA_LEN,
                );
                vec = src.to_vec();
            }
            libc::free(buffer);
        }
        Ok(vec)
    }

    /// Closes the file descriptor returned by [`fanotify_init()`]
    ///
    /// # Argument
    /// * `fd` - `fd` - file descriptor returned by [`fanotify_init()`]
    ///
    /// # Example
    /// ```rust
    /// # #[should_panic]
    /// # fn ex() {
    /// # use naughtyfy::flags::*;
    /// # use naughtyfy::types::*;
    /// # use naughtyfy::api::*;
    /// let fd = fanotify_init(FAN_CLASS_NOTIF, 0).unwrap();
    /// fanotify_mark(fd, FAN_MARK_ADD | FAN_MARK_MOUNT, FAN_ACCESS, libc::AT_FDCWD, "./");
    /// let fan_events = fanotify_read(fd);
    /// println!("{fan_events:#?}");
    ///
    /// # }
    /// ```
    pub fn fanotify_close(fd: i32) -> Result<(), Error> {
        unsafe {
            match libc::close(fd) {
                0 => Ok(()),
                _ => Err(Error::last_os_error()),
            }
        }
    }