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//! Implementation of the ZipCrypto algorithm
//!
//! The following paper was used to implement the ZipCrypto algorithm:
//! [https://courses.cs.ut.ee/MTAT.07.022/2015_fall/uploads/Main/dmitri-report-f15-16.pdf](https://courses.cs.ut.ee/MTAT.07.022/2015_fall/uploads/Main/dmitri-report-f15-16.pdf)
use std::num::Wrapping;
/// A container to hold the current key state
#[derive(Clone, Copy)]
pub(crate) struct ZipCryptoKeys {
key_0: Wrapping<u32>,
key_1: Wrapping<u32>,
key_2: Wrapping<u32>,
}
impl ZipCryptoKeys {
fn new() -> ZipCryptoKeys {
ZipCryptoKeys {
key_0: Wrapping(0x12345678),
key_1: Wrapping(0x23456789),
key_2: Wrapping(0x34567890),
}
}
fn update(&mut self, input: u8) {
self.key_0 = ZipCryptoKeys::crc32(self.key_0, input);
self.key_1 =
(self.key_1 + (self.key_0 & Wrapping(0xff))) * Wrapping(0x08088405) + Wrapping(1);
self.key_2 = ZipCryptoKeys::crc32(self.key_2, (self.key_1 >> 24).0 as u8);
}
fn stream_byte(&mut self) -> u8 {
let temp: Wrapping<u16> = Wrapping(self.key_2.0 as u16) | Wrapping(3);
((temp * (temp ^ Wrapping(1))) >> 8).0 as u8
}
fn decrypt_byte(&mut self, cipher_byte: u8) -> u8 {
let plain_byte: u8 = self.stream_byte() ^ cipher_byte;
self.update(plain_byte);
plain_byte
}
#[allow(dead_code)]
fn encrypt_byte(&mut self, plain_byte: u8) -> u8 {
let cipher_byte: u8 = self.stream_byte() ^ plain_byte;
self.update(plain_byte);
cipher_byte
}
fn crc32(crc: Wrapping<u32>, input: u8) -> Wrapping<u32> {
(crc >> 8) ^ Wrapping(CRCTABLE[((crc & Wrapping(0xff)).0 as u8 ^ input) as usize])
}
pub(crate) fn derive(password: &[u8]) -> ZipCryptoKeys {
let mut keys = ZipCryptoKeys::new();
for byte in password.iter() {
keys.update(*byte);
}
keys
}
}
/// A ZipCrypto reader with unverified password
pub struct ZipCryptoReader<R> {
file: R,
keys: ZipCryptoKeys,
}
pub enum ZipCryptoValidator {
PkzipCrc32(u32),
InfoZipMsdosTime(u16),
}
impl<R: std::io::Read> ZipCryptoReader<R> {
/// Note: The password is `&[u8]` and not `&str` because the
/// [zip specification](https://pkware.cachefly.net/webdocs/APPNOTE/APPNOTE-6.3.3.TXT)
/// does not specify password encoding (see function `update_keys` in the specification).
/// Therefore, if `&str` was used, the password would be UTF-8 and it
/// would be impossible to decrypt files that were encrypted with a
/// password byte sequence that is unrepresentable in UTF-8.
pub fn new(file: R, password: &[u8]) -> ZipCryptoReader<R> {
ZipCryptoReader {
file,
keys: ZipCryptoKeys::derive(password),
}
}
/// Read the ZipCrypto header bytes and validate the password.
pub fn validate(
mut self,
validator: ZipCryptoValidator,
) -> Result<Option<ZipCryptoReaderValid<R>>, std::io::Error> {
// ZipCrypto prefixes a file with a 12 byte header
let mut header_buf = [0u8; 12];
self.file.read_exact(&mut header_buf)?;
for byte in header_buf.iter_mut() {
*byte = self.keys.decrypt_byte(*byte);
}
match validator {
ZipCryptoValidator::PkzipCrc32(crc32_plaintext) => {
// PKZIP before 2.0 used 2 byte CRC check.
// PKZIP 2.0+ used 1 byte CRC check. It's more secure.
// We also use 1 byte CRC.
if (crc32_plaintext >> 24) as u8 != header_buf[11] {
return Ok(None); // Wrong password
}
}
ZipCryptoValidator::InfoZipMsdosTime(last_mod_time) => {
// Info-ZIP modification to ZipCrypto format:
// If bit 3 of the general purpose bit flag is set
// (indicates that the file uses a data-descriptor section),
// it uses high byte of 16-bit File Time.
// Info-ZIP code probably writes 2 bytes of File Time.
// We check only 1 byte.
if (last_mod_time >> 8) as u8 != header_buf[11] {
return Ok(None); // Wrong password
}
}
}
Ok(Some(ZipCryptoReaderValid { reader: self }))
}
}
pub(crate) struct ZipCryptoWriter<W> {
pub(crate) writer: W,
pub(crate) buffer: Vec<u8>,
pub(crate) keys: ZipCryptoKeys,
}
impl<W: std::io::Write> ZipCryptoWriter<W> {
pub(crate) fn finish(mut self, crc32: u32) -> std::io::Result<W> {
self.buffer[11] = (crc32 >> 24) as u8;
for byte in self.buffer.iter_mut() {
*byte = self.keys.encrypt_byte(*byte);
}
self.writer.write_all(&self.buffer)?;
self.writer.flush()?;
Ok(self.writer)
}
}
impl<W: std::io::Write> std::io::Write for ZipCryptoWriter<W> {
fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
self.buffer.extend_from_slice(buf);
Ok(buf.len())
}
fn flush(&mut self) -> std::io::Result<()> {
Ok(())
}
}
/// A ZipCrypto reader with verified password
pub struct ZipCryptoReaderValid<R> {
reader: ZipCryptoReader<R>,
}
impl<R: std::io::Read> std::io::Read for ZipCryptoReaderValid<R> {
fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
// Note: There might be potential for optimization. Inspiration can be found at:
// https://github.com/kornelski/7z/blob/master/CPP/7zip/Crypto/ZipCrypto.cpp
let result = self.reader.file.read(buf);
for byte in buf.iter_mut() {
*byte = self.reader.keys.decrypt_byte(*byte);
}
result
}
}
impl<R: std::io::Read> ZipCryptoReaderValid<R> {
/// Consumes this decoder, returning the underlying reader.
pub fn into_inner(self) -> R {
self.reader.file
}
}
static CRCTABLE: [u32; 256] = [
0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d,
];
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