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Fix an issue parsing zip64 files

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Offset to the start of central directory may be 0xFFFFFFFF if it is a
Zip64 file. Previously, that value was used when calculating the archive
offset. The value will now be ignored if the Zip64 central directory
could be located.
This commit is contained in:
Mathijs van de Nes 2018-06-22 15:16:04 +02:00
parent 9b0a6930d4
commit 2fa4111042
1 changed files with 59 additions and 53 deletions
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112
src/read.rs
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@ -135,71 +135,77 @@ impl<R: Read+io::Seek> ZipArchive<R>
{
/// Get the directory start offset and number of files. This is done in a
/// separate function to ease the control flow design.
fn get_directory_counts(mut reader: &mut R,
fn get_directory_counts(reader: &mut R,
footer: &spec::CentralDirectoryEnd,
cde_start_pos: u64) -> ZipResult<(u64, u64, usize)> {
// Some zip files have data prepended to them, resulting in the
// offsets all being too small. Get the amount of error by comparing
// the actual file position we found the CDE at with the offset
// recorded in the CDE.
let archive_offset = cde_start_pos.checked_sub(footer.central_directory_size as u64)
.and_then(|x| x.checked_sub(footer.central_directory_offset as u64))
.ok_or(ZipError::InvalidArchive("Invalid central directory size or offset"))?;
let directory_start = footer.central_directory_offset as u64 + archive_offset;
let number_of_files = footer.number_of_files_on_this_disk as usize;
// See if there's a ZIP64 footer. The ZIP64 locator if present will
// have its signature 20 bytes in front of the standard footer. The
// standard footer, in turn, is 22+N bytes large, where N is the
// comment length. Therefore:
if let Err(_) = reader.seek(io::SeekFrom::Current(-(20 + 22 + footer.zip_file_comment.len() as i64))) {
let zip64locator = if reader.seek(io::SeekFrom::End(-(20 + 22 + footer.zip_file_comment.len() as i64))).is_ok() {
match spec::Zip64CentralDirectoryEndLocator::parse(reader) {
Ok(loc) => Some(loc),
Err(ZipError::InvalidArchive(_)) => {
// No ZIP64 header; that's actually fine. We're done here.
None
},
Err(e) => {
// Yikes, a real problem
return Err(e);
}
}
}
else {
// Empty Zip files will have nothing else so this error might be fine. If
// not, we'll find out soon.
return Ok((archive_offset, directory_start, number_of_files));
}
let locator64 = match spec::Zip64CentralDirectoryEndLocator::parse(&mut reader) {
Ok(loc) => loc,
Err(ZipError::InvalidArchive(_)) => {
// No ZIP64 header; that's actually fine. We're done here.
return Ok((archive_offset, directory_start, number_of_files));
},
Err(e) => {
// Yikes, a real problem
return Err(e);
},
None
};
// If we got here, this is indeed a ZIP64 file.
match zip64locator {
None => {
// Some zip files have data prepended to them, resulting in the
// offsets all being too small. Get the amount of error by comparing
// the actual file position we found the CDE at with the offset
// recorded in the CDE.
let archive_offset = cde_start_pos.checked_sub(footer.central_directory_size as u64)
.and_then(|x| x.checked_sub(footer.central_directory_offset as u64))
.ok_or(ZipError::InvalidArchive("Invalid central directory size or offset"))?;
if footer.disk_number as u32 != locator64.disk_with_central_directory {
return unsupported_zip_error("Support for multi-disk files is not implemented")
let directory_start = footer.central_directory_offset as u64 + archive_offset;
let number_of_files = footer.number_of_files_on_this_disk as usize;
return Ok((archive_offset, directory_start, number_of_files));
},
Some(locator64) => {
// If we got here, this is indeed a ZIP64 file.
if footer.disk_number as u32 != locator64.disk_with_central_directory {
return unsupported_zip_error("Support for multi-disk files is not implemented")
}
// We need to reassess `archive_offset`. We know where the ZIP64
// central-directory-end structure *should* be, but unfortunately we
// don't know how to precisely relate that location to our current
// actual offset in the file, since there may be junk at its
// beginning. Therefore we need to perform another search, as in
// read::CentralDirectoryEnd::find_and_parse, except now we search
// forward.
let search_upper_bound = cde_start_pos
.checked_sub(60) // minimum size of Zip64CentralDirectoryEnd + Zip64CentralDirectoryEndLocator
.ok_or(ZipError::InvalidArchive("File cannot contain ZIP64 central directory end"))?;
let (footer, archive_offset) = spec::Zip64CentralDirectoryEnd::find_and_parse(
reader,
locator64.end_of_central_directory_offset,
search_upper_bound)?;
if footer.disk_number != footer.disk_with_central_directory {
return unsupported_zip_error("Support for multi-disk files is not implemented")
}
let directory_start = footer.central_directory_offset + archive_offset;
Ok((archive_offset, directory_start, footer.number_of_files as usize))
},
}
// We need to reassess `archive_offset`. We know where the ZIP64
// central-directory-end structure *should* be, but unfortunately we
// don't know how to precisely relate that location to our current
// actual offset in the file, since there may be junk at its
// beginning. Therefore we need to perform another search, as in
// read::CentralDirectoryEnd::find_and_parse, except now we search
// forward.
let search_upper_bound = reader.seek(io::SeekFrom::Current(0))?
.checked_sub(60) // minimum size of Zip64CentralDirectoryEnd + Zip64CentralDirectoryEndLocator
.ok_or(ZipError::InvalidArchive("File cannot contain ZIP64 central directory end"))?;
let (footer, archive_offset) = spec::Zip64CentralDirectoryEnd::find_and_parse(
&mut reader,
locator64.end_of_central_directory_offset,
search_upper_bound)?;
if footer.disk_number != footer.disk_with_central_directory {
return unsupported_zip_error("Support for multi-disk files is not implemented")
}
let directory_start = footer.central_directory_offset + archive_offset;
Ok((archive_offset, directory_start, footer.number_of_files as usize))
}
/// Opens a Zip archive and parses the central directory