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use crate::{error::*, fields, format::*};
use nom::{
bytes::streaming::tag,
combinator::map,
multi::length_data,
number::streaming::{le_u16, le_u32, le_u64},
sequence::{preceded, tuple},
};
use tracing::trace;
/// 4.3.16 End of central directory record:
pub struct EndOfCentralDirectoryRecord {
/// number of this disk
pub disk_nbr: u16,
/// number of the disk with the start of the central directory
pub dir_disk_nbr: u16,
/// total number of entries in the central directory on this disk
pub dir_records_this_disk: u16,
/// total number of entries in the central directory
pub directory_records: u16,
// size of the central directory
pub directory_size: u32,
/// offset of start of central directory with respect to the starting disk number
pub directory_offset: u32,
/// .ZIP file comment
pub comment: ZipString,
}
impl EndOfCentralDirectoryRecord {
/// Does not include comment size & comment data
const MIN_LENGTH: usize = 20;
const SIGNATURE: &'static str = "PK\x05\x06";
pub fn find_in_block(b: &[u8]) -> Option<Located<Self>> {
for i in (0..(b.len() - Self::MIN_LENGTH + 1)).rev() {
let slice = &b[i..];
if let Ok((_, directory)) = Self::parse(slice) {
return Some(Located {
offset: i as u64,
inner: directory,
});
}
}
None
}
pub fn parse(i: &[u8]) -> parse::Result<'_, Self> {
preceded(
tag(Self::SIGNATURE),
map(
tuple((
le_u16::<&[u8], _>,
le_u16,
le_u16,
le_u16,
le_u32,
le_u32,
length_data(le_u16),
)),
|(
disk_nbr,
dir_disk_nbr,
dir_records_this_disk,
directory_records,
directory_size,
directory_offset,
comment,
)| Self {
disk_nbr,
dir_disk_nbr,
dir_records_this_disk,
directory_records,
directory_size,
directory_offset,
comment: comment.into(),
},
),
)(i)
}
}
/// 4.3.15 Zip64 end of central directory locator
pub struct EndOfCentralDirectory64Locator {
/// number of the disk with the start of the zip64 end of central directory
pub dir_disk_number: u32,
/// relative offset of the zip64 end of central directory record
pub directory_offset: u64,
/// total number of disks
pub total_disks: u32,
}
impl EndOfCentralDirectory64Locator {
pub const LENGTH: usize = 20;
const SIGNATURE: &'static str = "PK\x06\x07";
pub fn parse(i: &[u8]) -> parse::Result<'_, Self> {
preceded(
tag(Self::SIGNATURE),
fields!(Self {
dir_disk_number: le_u32,
directory_offset: le_u64,
total_disks: le_u32,
}),
)(i)
}
}
/// 4.3.14 Zip64 end of central directory record
pub struct EndOfCentralDirectory64Record {
/// size of zip64 end of central directory record
pub record_size: u64,
/// version made by
pub creator_version: u16,
/// version needed to extract
pub reader_version: u16,
/// number of this disk
pub disk_nbr: u32,
/// number of the disk with the start of the central directory
pub dir_disk_nbr: u32,
// total number of entries in the central directory on this disk
pub dir_records_this_disk: u64,
// total number of entries in the central directory
pub directory_records: u64,
// size of the central directory
pub directory_size: u64,
// offset of the start of central directory with respect to the
// starting disk number
pub directory_offset: u64,
}
impl EndOfCentralDirectory64Record {
const SIGNATURE: &'static str = "PK\x06\x06";
pub fn parse(i: &[u8]) -> parse::Result<'_, Self> {
preceded(
tag(Self::SIGNATURE),
fields!(Self {
record_size: le_u64,
creator_version: le_u16,
reader_version: le_u16,
disk_nbr: le_u32,
dir_disk_nbr: le_u32,
dir_records_this_disk: le_u64,
directory_records: le_u64,
directory_size: le_u64,
directory_offset: le_u64,
}),
)(i)
}
}
pub struct Located<T> {
pub offset: u64,
pub inner: T,
}
impl<T> std::ops::Deref for Located<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
&self.inner
}
}
impl<T> std::ops::DerefMut for Located<T> {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.inner
}
}
/// Coalesces zip and zip64 "end of central directory" record info
pub struct EndOfCentralDirectory {
pub dir: Located<EndOfCentralDirectoryRecord>,
pub dir64: Option<Located<EndOfCentralDirectory64Record>>,
pub global_offset: i64,
}
impl EndOfCentralDirectory {
pub fn new(
size: u64,
dir: Located<EndOfCentralDirectoryRecord>,
dir64: Option<Located<EndOfCentralDirectory64Record>>,
) -> Result<Self, Error> {
let mut res = Self {
dir,
dir64,
global_offset: 0,
};
//
// Pure .zip files look like this:
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// <------directory_size----->
// [ Data 1 ][ Data 2 ][ Central directory ][ ??? ]
// ^ ^ ^
// 0 directory_offset directory_end_offset
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//
// But there exist some valid zip archives with padding at the beginning, like so:
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// <--global_offset-> <------directory_size----->
// [ Padding ][ Data 1 ][ Data 2 ][ Central directory ][ ??? ]
// ^ ^ ^ ^
// 0 global_offset computed_directory_offset directory_end_offset
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//
// (e.g. https://www.icculus.org/mojosetup/ installers are ELF binaries with a .zip file appended)
//
// `directory_end_offfset` is found by scanning the file (so it accounts for padding), but
// `directory_offset` is found by reading a data structure (so it does not account for padding).
// If we just trusted `directory_offset`, we'd be reading the central directory at the wrong place:
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// <------directory_size----->
// [ Padding ][ Data 1 ][ Data 2 ][ Central directory ][ ??? ]
// ^ ^ ^
// 0 directory_offset - woops! directory_end_offset
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
let computed_directory_offset = res.located_directory_offset() - res.directory_size();
// did we find a valid offset?
if (0..size).contains(&computed_directory_offset) {
// that's different from the recorded one?
if computed_directory_offset != res.directory_offset() {
// then assume the whole file is offset
res.global_offset =
computed_directory_offset as i64 - res.directory_offset() as i64;
res.set_directory_offset(computed_directory_offset);
}
}
// make sure directory_offset points to somewhere in our file
trace!(
"directory offset = {}, valid range = 0..{}",
res.directory_offset(),
size
);
if !(0..size).contains(&res.directory_offset()) {
return Err(FormatError::DirectoryOffsetPointsOutsideFile.into());
}
Ok(res)
}
pub fn located_directory_offset(&self) -> u64 {
match self.dir64.as_ref() {
Some(d64) => d64.offset,
None => self.dir.offset,
}
}
pub fn directory_offset(&self) -> u64 {
match self.dir64.as_ref() {
Some(d64) => d64.directory_offset,
None => self.dir.directory_offset as u64,
}
}
pub fn directory_size(&self) -> u64 {
match self.dir64.as_ref() {
Some(d64) => d64.directory_size,
None => self.dir.directory_size as u64,
}
}
pub fn set_directory_offset(&mut self, offset: u64) {
match self.dir64.as_mut() {
Some(d64) => d64.directory_offset = offset,
None => self.dir.directory_offset = offset as u32,
};
}
pub fn directory_records(&self) -> u64 {
match self.dir64.as_ref() {
Some(d64) => d64.directory_records,
None => self.dir.directory_records as u64,
}
}
pub fn comment(&self) -> &ZipString {
&self.dir.comment
}
}