mountinfo 0.2.0

/**
 * The MIT License
 * Copyright (c) 2022 Guillem Castro
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

use std::str::FromStr;
use std::path::{Path, PathBuf};
use std::io::{self, BufRead};
use std::fs::File;
use std::fmt;
use regex::Regex;

/// Some common filesystems types
/// The String representation must be the same when creating using `from_str`
/// and when converting to `String` using `fmt::Display`
#[derive(Debug, PartialEq)]
pub enum FsType {
    /// procfs filesystem. Pseudo filesystem that exposes the kernel's process table. 
    /// Usually mounted at /proc.
    Proc,
    /// overlayfs filesystem. A filesystem that combines multiple lower filesystems into a single directory.
    Overlay,
    /// tmpfs filesystem. A filesystem that provides a temporary file system stored in volatile memory.
    Tmpfs,
    /// sysfs filesystem. A filesystem that provides access to the kernel's internal device tree.
    Sysfs,
    /// btrfs filesystem. A filesystem that provides a hierarchical data structure for storing data in a compressed fashion.
    Btrfs,
    /// ext2 filesystem. A filesystem that provides a file system that is optimized for storing data on a local disk.
    Ext2,
    /// ext3 filesystem. A filesystem that provides a file system that is optimized for storing data on a local disk.
    Ext3,
    /// ext4 filesystem. A filesystem that provides a file system that is optimized for storing data on a local disk.
    Ext4,
    /// devtmpfs filesystem.
    Devtmpfs,
    /// Other filesystems.
    Other(String)
}

impl FromStr for FsType {
    
    type Err = ();

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s {
            "proc" => Ok(FsType::Proc),
            "tmpfs" => Ok(FsType::Tmpfs),
            "overlay" => Ok(FsType::Overlay),
            "sysfs" => Ok(FsType::Sysfs),
            "btrfs" => Ok(FsType::Btrfs),
            "ext2" => Ok(FsType::Ext2),
            "ext3" => Ok(FsType::Ext3),
            "ext4" => Ok(FsType::Ext4),
            "devtmpfs" => Ok(FsType::Devtmpfs),
            _ => Ok(FsType::Other(s.to_string()))
        }
    }
}

impl fmt::Display for FsType {

    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { 
        let fsname = match self {
            FsType::Proc => "proc",
            FsType::Overlay => "overlay",
            FsType::Tmpfs => "tmpfs",
            FsType::Sysfs => "sysfs",
            FsType::Btrfs => "btrfs",
            FsType::Ext2 => "ext2",
            FsType::Ext3 => "ext3",
            FsType::Ext4 => "ext4",
            FsType::Devtmpfs => "devtmpfs",
            FsType::Other(ref fsname) => fsname
        };
        write!(f, "{}", fsname)
    }

}

/// A struct representing a mount point.
#[derive(Debug)]
pub struct MountPoint {
    /// The id of the mount point. It is unique for each mount point,
    /// but can be resused afer a call to the umount syscall.
    pub id: Option<u32>,
    /// The id of the parent mount.
    pub parent_id: Option<u32>,
    /// The path to the directory that acts as the root for this mount point.
    pub root: Option<PathBuf>,
    // Filesystem-specific information
    pub what: String,
    /// The mount point directory relative to the root.
    pub path: PathBuf,
    /// The filesystem type.
    pub fstype: FsType,
    /// Some additional mount options
    pub options: MountOptions,
}

impl MountPoint {
    
    /// Creates a new mount point from a line of the `/proc/self/mountinfo` file.
    fn parse_proc_mountinfo_line(line: &String) -> Result<Self, io::Error> {
        // The line format is:
        // <id> <parent_id> <major>:<minor> <root> <mount_point> <mount_options> <optional tags> "-" <fstype> <mount souce> <super options>
        // Ref: https://www.kernel.org/doc/Documentation/filesystems/proc.txt - /proc/<pid>/mountinfo - Information about mounts
        let re = Regex::new(r"(\d*)\s(\d*)\s(\d*:\d*)\s([\S]*)\s([\S]*)\s([A-Za-z0-9,]*)\s([A-Za-z0-9:\s]*)\s\- ([\S]*)\s([\S]*)(.*)").unwrap();
        if !re.is_match(line) {
            return Err(io::Error::new(io::ErrorKind::InvalidData, "Invalid format"));
        }
        let caps = re.captures(line).unwrap();
        Ok(MountPoint {
            id: Some(caps[1].parse::<u32>().unwrap()),
            parent_id: Some(caps[2].parse::<u32>().unwrap()),
            root: Some(PathBuf::from(caps[4].to_string())),
            path: PathBuf::from(caps[5].to_string()),
            options: MountOptions::new(&caps[6].to_string()),
            fstype: FsType::from_str(&caps[8]).unwrap(),
            what: caps[9].to_string()
        })
    }

}

#[derive(Debug)]
#[derive(PartialEq)]
pub enum ReadWrite {
    ReadOnly,
    ReadWrite
}

/// A struct representing the mount options.
#[derive(Debug)]
pub struct MountOptions {
    /// If it was mounted as read-only or read-write.
    pub read_write: ReadWrite,
    /// Additional options, not currently parsed by this library.
    pub others: Vec<String>
}

impl MountOptions {
    
    /// Creates a new mount options from a string.
    /// The string must be a comma-separated list of options.
    pub fn new(options: &str) -> Self {
        let mut read_write = ReadWrite::ReadOnly;
        let mut others = Vec::new();
        for option in options.split(',') {
            match option {
                "ro" => read_write = ReadWrite::ReadOnly,
                "rw" => read_write = ReadWrite::ReadWrite,
                &_ => others.push(option.to_owned())
            }
        }
        MountOptions {
            read_write,
            others
        }
    }

}

/// A struct containing the mount information.
/// Note that it will only contain the mount points visible for the calling process.
/// If the calling process is inside a chroot, not all mount points will be visible. 
#[derive(Debug)]
pub struct MountInfo {
    /// The list of mount points visible for the current process.
    pub mounting_points: Vec<MountPoint>
}

impl MountInfo {

    /// The most "modern" file with mount information. Introduced in Linux 2.6.26.
    /// According to the docs, this should be the most reliable (and up-to-date) way to get the mount information.
    const MOUNT_INFO_FILE: &'static str = "/proc/self/mountinfo";

    /// This file should exists even in ancient versions of the Linux kernel.
    /// We use it as a fallback, if for some reason /proc/self/mountinfo is not available.
    /// Believe it or not, there are still devices running ancient versions of the Linux kernel.
    const MTAB_FILE: &'static str = "/etc/mtab";

    /// Creates a new instance of the MountInfo struct.
    /// It will read the contents of the /proc/self/mountinfo file, if it exists.
    /// If it does not exist, it will fall-back to read the contents of the /etc/mtab file.
    pub fn new() -> Result<Self, io::Error> {
        if Path::new(MountInfo::MOUNT_INFO_FILE).exists() {
            let mut mtab = File::open("/proc/self/mountinfo")?;
            return Ok(MountInfo {
                mounting_points: MountInfo::parse_proc_mountinfo(&mut mtab)?
            })
        }
        else if Path::new(MountInfo::MTAB_FILE).exists() {
            let mut mtab = File::open(MountInfo::MTAB_FILE)?;
            return Ok(MountInfo {
                mounting_points: MountInfo::parse_mtab(&mut mtab)?
            })
        }
        else {
            return Err(io::Error::new(io::ErrorKind::NotFound, "No mountinfo file found"))
        }
    }

    /// Check if a certain filesystem type is mounted at the given path. 
    pub fn contains<P: AsRef<Path>>(&self, mounting_point: P, fstype: FsType) -> bool {
        let path = mounting_point.as_ref();
        let filtered: Vec<&MountPoint> = self.mounting_points.iter().
            filter(|mts| 
                mts.path == path.to_owned() && mts.fstype == fstype)
            .collect();
        filtered.len() > 0
    }

    /// Check if the given path is a mount point.
    pub fn is_mounted<P: AsRef<Path>>(&self, path: P) -> bool {
        let filtered: Vec<&MountPoint> = self.mounting_points.iter().
            filter(|mts| 
                mts.path == path.as_ref().to_path_buf())
            .collect();
        filtered.len() > 0
    }

    fn parse_proc_mountinfo(file: &mut dyn std::io::Read) -> Result<Vec<MountPoint>, std::io::Error> {
        let mut result = Vec::new();
        let reader = io::BufReader::new(file);
        for line in reader.lines() {
            let mpoint = MountPoint::parse_proc_mountinfo_line(&line?)?;
            result.push(mpoint);
        }
        Ok(result)
    }

    fn parse_mtab(file: &mut dyn std::io::Read) -> Result<Vec<MountPoint>, std::io::Error> {
        let mut results: Vec<MountPoint> = vec![];
        let reader = io::BufReader::new(file);
        for line in reader.lines() {
            let l = line?;
            let parts: Vec<&str> = l.split_whitespace().collect();
            if !parts.is_empty() {
                results.push(MountPoint {
                    what: parts[0].to_string(),
                    path: PathBuf::from(parts[1]),
                    fstype: FsType::from_str(parts[2]).unwrap(),
                    options: MountOptions::new(parts[3]),
                    id: None,
                    parent_id: None,
                    root: None,
                })
            }
        }
        Ok(results)
    }

}

// unit tests
#[cfg(test)]
mod test {

    use super::*;

    struct FakeFile {
        s: String,
        read: bool
    }

    impl io::Read for FakeFile {
        fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
            if self.read {
                return Ok(0);
            }
            let mut i = 0;
            while i < self.s.len() {
                buf[i] = self.s.as_bytes()[i];
                i += 1;
            }
            self.read = true;
            Ok(buf.len())
        }
    }

    #[test]
    fn test_load_mount_points() {
        let mut file = FakeFile { s: "tmpfs /tmp tmpfs rw,seclabel,nosuid,nodev,size=8026512k,nr_inodes=1048576,inode64 0 0".to_owned(), read: false };
        let munt_points = MountInfo::parse_mtab(&mut file).unwrap();
        assert_eq!(munt_points.len(), 1);
        assert_eq!(munt_points[0].what, "tmpfs".to_owned());
        assert_eq!(munt_points[0].path, PathBuf::from("/tmp"));
        assert_eq!(munt_points[0].fstype, FsType::Tmpfs);
    }

    #[test]
    fn test_contains() {
        let mut file = FakeFile { s: "tmpfs /tmp tmpfs rw,seclabel,nosuid,nodev,size=8026512k,nr_inodes=1048576,inode64 0 0".to_owned(), read: false };
        let mtab = MountInfo { mounting_points: MountInfo::parse_mtab(&mut file).unwrap() };
        assert_eq!(mtab.contains("/tmp", FsType::Tmpfs), true);
    }

    #[test]
    fn test_is_mounted() {
        let mut file = FakeFile { s: "tmpfs /tmp tmpfs rw,seclabel,nosuid,nodev,size=8026512k,nr_inodes=1048576,inode64 0 0".to_owned(), read: false };
        let mtab = MountInfo { mounting_points: MountInfo::parse_mtab(&mut file).unwrap() };
        assert_eq!(mtab.is_mounted("/tmp"), true);
    }

    #[test]
    fn test_mount_options() {
        let options = MountOptions::new("rw,seclabel,nosuid,nodev,size=8026512k,nr_inodes=1048576,inode64");
        assert_eq!(options.read_write, ReadWrite::ReadWrite);
        assert_ne!(options.others.len(), 0);
        let more_options = MountOptions::new("ro,seclabel,nosuid,nodev,size=8026512k,nr_inodes=1048576,inode64");
        assert_eq!(more_options.read_write, ReadWrite::ReadOnly);
        assert_ne!(more_options.others.len(), 0);
    }
}