cloud-hypervisor/block_util/src/vhd.rs

// Copyright © 2021 Intel Corporation
//
// SPDX-License-Identifier: Apache-2.0

use std::convert::TryInto;
use std::fs::File;
use std::io::{Read, Seek, SeekFrom};

#[derive(Clone, Copy)]
pub struct VhdFooter {
    cookie: u64,
    features: u32,
    file_format_version: u32,
    data_offset: u64,
    time_stamp: u32,
    creator_application: u32,
    creator_version: u32,
    creator_host_os: u32,
    original_size: u64,
    current_size: u64,
    disk_geometry: u32,
    disk_type: u32,
    checksum: u32,
    unique_id: u128,
    saved_state: u8,
}

impl VhdFooter {
    pub fn new(file: &mut File) -> std::io::Result<VhdFooter> {
        // We must create a buffer aligned on 512 bytes with a size being a
        // multiple of 512 bytes as the file might be opened with O_DIRECT flag.
        #[repr(align(512))]
        struct Sector {
            data: [u8; 512],
        }
        let mut s = Sector { data: [0; 512] };

        // Place the cursor 512 bytes before the end of the file, as this is
        // where the footer starts.
        file.seek(SeekFrom::End(-512))?;

        // Fill in the VhdFooter structure
        file.read_exact(&mut s.data)?;

        Ok(VhdFooter {
            cookie: u64::from_be_bytes(s.data[0..8].try_into().unwrap()),
            features: u32::from_be_bytes(s.data[8..12].try_into().unwrap()),
            file_format_version: u32::from_be_bytes(s.data[12..16].try_into().unwrap()),
            data_offset: u64::from_be_bytes(s.data[16..24].try_into().unwrap()),
            time_stamp: u32::from_be_bytes(s.data[24..28].try_into().unwrap()),
            creator_application: u32::from_be_bytes(s.data[28..32].try_into().unwrap()),
            creator_version: u32::from_be_bytes(s.data[32..36].try_into().unwrap()),
            creator_host_os: u32::from_be_bytes(s.data[36..40].try_into().unwrap()),
            original_size: u64::from_be_bytes(s.data[40..48].try_into().unwrap()),
            current_size: u64::from_be_bytes(s.data[48..56].try_into().unwrap()),
            disk_geometry: u32::from_be_bytes(s.data[56..60].try_into().unwrap()),
            disk_type: u32::from_be_bytes(s.data[60..64].try_into().unwrap()),
            checksum: u32::from_be_bytes(s.data[64..68].try_into().unwrap()),
            unique_id: u128::from_be_bytes(s.data[68..84].try_into().unwrap()),
            saved_state: u8::from_be_bytes(s.data[84..85].try_into().unwrap()),
        })
    }

    pub fn cookie(&self) -> u64 {
        self.cookie
    }
    pub fn features(&self) -> u32 {
        self.features
    }
    pub fn file_format_version(&self) -> u32 {
        self.file_format_version
    }
    pub fn data_offset(&self) -> u64 {
        self.data_offset
    }
    pub fn time_stamp(&self) -> u32 {
        self.time_stamp
    }
    pub fn creator_application(&self) -> u32 {
        self.creator_application
    }
    pub fn creator_version(&self) -> u32 {
        self.creator_version
    }
    pub fn creator_host_os(&self) -> u32 {
        self.creator_host_os
    }
    pub fn original_size(&self) -> u64 {
        self.original_size
    }
    pub fn current_size(&self) -> u64 {
        self.current_size
    }
    pub fn disk_geometry(&self) -> u32 {
        self.disk_geometry
    }
    pub fn disk_type(&self) -> u32 {
        self.disk_type
    }
    pub fn checksum(&self) -> u32 {
        self.checksum
    }
    pub fn unique_id(&self) -> u128 {
        self.unique_id
    }
    pub fn saved_state(&self) -> u8 {
        self.saved_state
    }
}

/// Determine image type through file parsing.
pub fn is_fixed_vhd(f: &mut File) -> std::io::Result<bool> {
    let footer = VhdFooter::new(f)?;

    // "conectix" => 0x636f6e6563746978
    Ok(footer.cookie() == 0x636f6e6563746978
        && footer.file_format_version() == 0x0001_0000
        && footer.data_offset() == 0xffff_ffff_ffff_ffff
        && footer.disk_type() == 0x2)
}

#[cfg(test)]
mod tests {
    use super::{is_fixed_vhd, VhdFooter};
    use std::fs::File;
    use std::io::{Seek, SeekFrom, Write};
    use vmm_sys_util::tempfile::TempFile;

    fn valid_fixed_vhd_footer() -> Vec<u8> {
        vec![
            0x63, 0x6f, 0x6e, 0x65, 0x63, 0x74, 0x69, 0x78, // cookie
            0x00, 0x00, 0x00, 0x02, // features
            0x00, 0x01, 0x00, 0x00, // file format version
            0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, // data offset
            0x27, 0xa6, 0xa6, 0x5d, // time stamp
            0x71, 0x65, 0x6d, 0x75, // creator application
            0x00, 0x05, 0x00, 0x03, // creator version
            0x57, 0x69, 0x32, 0x6b, // creator host os
            0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, // original size
            0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, // current size
            0x11, 0xe0, 0x10, 0x3f, // disk geometry
            0x00, 0x00, 0x00, 0x02, // disk type
            0x00, 0x00, 0x00, 0x00, // checksum
            0x98, 0x7b, 0xb1, 0xcd, 0x84, 0x14, 0x41, 0xfc, 0xa4, 0xab, 0xd0, 0x69, 0x45, 0x2b,
            0xf2, 0x23, // unique id
            0x00, // saved state
        ]
    }

    fn valid_dynamic_vhd_footer() -> Vec<u8> {
        vec![
            0x63, 0x6f, 0x6e, 0x65, 0x63, 0x74, 0x69, 0x78, // cookie
            0x00, 0x00, 0x00, 0x02, // features
            0x00, 0x01, 0x00, 0x00, // file format version
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // data offset
            0x27, 0xa6, 0xa6, 0x5d, // time stamp
            0x71, 0x65, 0x6d, 0x75, // creator application
            0x00, 0x05, 0x00, 0x03, // creator version
            0x57, 0x69, 0x32, 0x6b, // creator host os
            0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, // original size
            0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, // current size
            0x11, 0xe0, 0x10, 0x3f, // disk geometry
            0x00, 0x00, 0x00, 0x03, // disk type
            0x00, 0x00, 0x00, 0x00, // checksum
            0x98, 0x7b, 0xb1, 0xcd, 0x84, 0x14, 0x41, 0xfc, 0xa4, 0xab, 0xd0, 0x69, 0x45, 0x2b,
            0xf2, 0x23, // unique id
            0x00, // saved state
        ]
    }

    fn with_file<F>(footer: &[u8], mut testfn: F)
    where
        F: FnMut(File),
    {
        let mut disk_file: File = TempFile::new().unwrap().into_file();
        disk_file.set_len(0x1000_0200).unwrap();
        disk_file.seek(SeekFrom::Start(0x1000_0000)).unwrap();
        disk_file.write_all(footer).unwrap();

        testfn(disk_file); // File closed when the function exits.
    }

    #[test]
    fn test_check_vhd_footer() {
        with_file(&valid_fixed_vhd_footer(), |mut file: File| {
            let vhd_footer = VhdFooter::new(&mut file).expect("Failed to create VHD footer");
            assert_eq!(vhd_footer.cookie(), 0x636f_6e65_6374_6978);
            assert_eq!(vhd_footer.features(), 0x0000_0002);
            assert_eq!(vhd_footer.file_format_version(), 0x0001_0000);
            assert_eq!(vhd_footer.data_offset(), 0xffff_ffff_ffff_ffff);
            assert_eq!(vhd_footer.time_stamp(), 0x27a6_a65d);
            assert_eq!(vhd_footer.creator_application(), 0x7165_6d75);
            assert_eq!(vhd_footer.creator_version(), 0x0005_0003);
            assert_eq!(vhd_footer.creator_host_os(), 0x5769_326b);
            assert_eq!(vhd_footer.original_size(), 0x0000_0000_1000_0000);
            assert_eq!(vhd_footer.current_size(), 0x0000_0000_1000_0000);
            assert_eq!(vhd_footer.disk_geometry(), 0x11e0_103f);
            assert_eq!(vhd_footer.disk_type(), 0x0000_0002);
            assert_eq!(vhd_footer.checksum(), 0x0000_0000);
            assert_eq!(
                vhd_footer.unique_id(),
                0x987b_b1cd_8414_41fc_a4ab_d069_452b_f223
            );
            assert_eq!(vhd_footer.saved_state(), 0x00);
        });
    }

    #[test]
    fn test_is_fixed_vhd() {
        with_file(&valid_fixed_vhd_footer(), |mut file: File| {
            assert!(is_fixed_vhd(&mut file).unwrap());
        });
    }

    #[test]
    fn test_is_not_fixed_vhd() {
        with_file(&valid_dynamic_vhd_footer(), |mut file: File| {
            assert!(!(is_fixed_vhd(&mut file).unwrap()));
        });
    }
}