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use crate::utils::ReadUtils;
use crate::zip::{ZipError, ZipResult};
use std::io::{Read, Result as IoResult};
const TABLE: [u32; 256] = generate_table();
const fn generate_table() -> [u32; 256] {
let mut table = [0; 256];
let mut b = 0;
while b <= 255 {
let mut crc = b as u32;
let mut i = 0;
while i < 8 {
if (crc & 1) > 0 {
crc = (crc >> 1) ^ 0xEDB88320
} else {
crc >>= 1
}
i += 1;
}
table[b] = crc;
b += 1
}
table
}
fn crc32(byte: u8, crc: u32) -> u32 {
(crc >> 8) ^ TABLE[((crc & 0xFF) as u8 ^ byte) as usize]
}
pub struct WeakDecoder<Io: Read> {
key0: u32,
key1: u32,
key2: u32,
io: Io,
}
impl<Io: Read> WeakDecoder<Io> {
pub fn new(io: Io, check: u8, password: &[u8]) -> ZipResult<Self> {
let mut decoder = Self {
key0: 305419896,
key1: 591751049,
key2: 878082192,
io,
};
for c in password {
decoder.update_keys(*c)
}
let buf = decoder.read_arr::<12>()?;
if check != buf[11] {
return Err(ZipError::IncorrectPassword.into());
}
Ok(decoder)
}
fn update_keys(&mut self, byte: u8) {
self.key0 = crc32(byte, self.key0);
self.key1 = self
.key1
.wrapping_add(self.key0 & 0xFF)
.wrapping_mul(134775813)
.wrapping_add(1);
self.key2 = crc32((self.key1 >> 24) as u8, self.key2);
}
fn decode_byte(&mut self, byte: u8) -> u8 {
let key = self.key2 | 2;
let byte = byte ^ ((key * (key ^ 1)) >> 8) as u8;
self.update_keys(byte);
byte
}
}
impl<Io: Read> Read for WeakDecoder<Io> {
fn read(&mut self, buf: &mut [u8]) -> IoResult<usize> {
let bytes = self.io.read(buf)?;
for i in 0..bytes {
buf[i] = self.decode_byte(buf[i]);
}
Ok(bytes)
}
}
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