1//! Implementation of the ZipCrypto algorithm
2//!
3//! The following paper was used to implement the ZipCrypto algorithm:
4//! [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)
5
6use std::num::Wrapping;
7
8/// A container to hold the current key state
9#[derive(Clone, Copy)]
10pub(crate) struct ZipCryptoKeys {
11 key_0: Wrapping<u32>,
12 key_1: Wrapping<u32>,
13 key_2: Wrapping<u32>,
14}
15
16impl ZipCryptoKeys {
17 fn new() -> ZipCryptoKeys {
18 ZipCryptoKeys {
19 key_0: Wrapping(0x12345678),
20 key_1: Wrapping(0x23456789),
21 key_2: Wrapping(0x34567890),
22 }
23 }
24
25 fn update(&mut self, input: u8) {
26 self.key_0 = ZipCryptoKeys::crc32(self.key_0, input);
27 self.key_1 =
28 (self.key_1 + (self.key_0 & Wrapping(0xff))) * Wrapping(0x08088405) + Wrapping(1);
29 self.key_2 = ZipCryptoKeys::crc32(self.key_2, (self.key_1 >> 24).0 as u8);
30 }
31
32 fn stream_byte(&mut self) -> u8 {
33 let temp: Wrapping<u16> = Wrapping(self.key_2.0 as u16) | Wrapping(3);
34 ((temp * (temp ^ Wrapping(1))) >> 8).0 as u8
35 }
36
37 fn decrypt_byte(&mut self, cipher_byte: u8) -> u8 {
38 let plain_byte: u8 = self.stream_byte() ^ cipher_byte;
39 self.update(plain_byte);
40 plain_byte
41 }
42
43 #[allow(dead_code)]
44 fn encrypt_byte(&mut self, plain_byte: u8) -> u8 {
45 let cipher_byte: u8 = self.stream_byte() ^ plain_byte;
46 self.update(plain_byte);
47 cipher_byte
48 }
49
50 fn crc32(crc: Wrapping<u32>, input: u8) -> Wrapping<u32> {
51 (crc >> 8) ^ Wrapping(CRCTABLE[((crc & Wrapping(0xff)).0 as u8 ^ input) as usize])
52 }
53 pub(crate) fn derive(password: &[u8]) -> ZipCryptoKeys {
54 let mut keys = ZipCryptoKeys::new();
55 for byte in password.iter() {
56 keys.update(*byte);
57 }
58 keys
59 }
60}
61
62/// A ZipCrypto reader with unverified password
63pub struct ZipCryptoReader<R> {
64 file: R,
65 keys: ZipCryptoKeys,
66}
67
68pub enum ZipCryptoValidator {
69 PkzipCrc32(u32),
70 InfoZipMsdosTime(u16),
71}
72
73impl<R: std::io::Read> ZipCryptoReader<R> {
74 /// Note: The password is `&[u8]` and not `&str` because the
75 /// [zip specification](https://pkware.cachefly.net/webdocs/APPNOTE/APPNOTE-6.3.3.TXT)
76 /// does not specify password encoding (see function `update_keys` in the specification).
77 /// Therefore, if `&str` was used, the password would be UTF-8 and it
78 /// would be impossible to decrypt files that were encrypted with a
79 /// password byte sequence that is unrepresentable in UTF-8.
80 pub fn new(file: R, password: &[u8]) -> ZipCryptoReader<R> {
81 ZipCryptoReader {
82 file,
83 keys: ZipCryptoKeys::derive(password),
84 }
85 }
86
87 /// Read the ZipCrypto header bytes and validate the password.
88 pub fn validate(
89 mut self,
90 validator: ZipCryptoValidator,
91 ) -> Result<Option<ZipCryptoReaderValid<R>>, std::io::Error> {
92 // ZipCrypto prefixes a file with a 12 byte header
93 let mut header_buf = [0u8; 12];
94 self.file.read_exact(&mut header_buf)?;
95 for byte in header_buf.iter_mut() {
96 *byte = self.keys.decrypt_byte(*byte);
97 }
98
99 match validator {
100 ZipCryptoValidator::PkzipCrc32(crc32_plaintext) => {
101 // PKZIP before 2.0 used 2 byte CRC check.
102 // PKZIP 2.0+ used 1 byte CRC check. It's more secure.
103 // We also use 1 byte CRC.
104
105 if (crc32_plaintext >> 24) as u8 != header_buf[11] {
106 return Ok(None); // Wrong password
107 }
108 }
109 ZipCryptoValidator::InfoZipMsdosTime(last_mod_time) => {
110 // Info-ZIP modification to ZipCrypto format:
111 // If bit 3 of the general purpose bit flag is set
112 // (indicates that the file uses a data-descriptor section),
113 // it uses high byte of 16-bit File Time.
114 // Info-ZIP code probably writes 2 bytes of File Time.
115 // We check only 1 byte.
116
117 if (last_mod_time >> 8) as u8 != header_buf[11] {
118 return Ok(None); // Wrong password
119 }
120 }
121 }
122
123 Ok(Some(ZipCryptoReaderValid { reader: self }))
124 }
125}
126pub(crate) struct ZipCryptoWriter<W> {
127 pub(crate) writer: W,
128 pub(crate) buffer: Vec<u8>,
129 pub(crate) keys: ZipCryptoKeys,
130}
131impl<W: std::io::Write> ZipCryptoWriter<W> {
132 pub(crate) fn finish(mut self, crc32: u32) -> std::io::Result<W> {
133 self.buffer[11] = (crc32 >> 24) as u8;
134 for byte: &mut u8 in self.buffer.iter_mut() {
135 *byte = self.keys.encrypt_byte(*byte);
136 }
137 self.writer.write_all(&self.buffer)?;
138 self.writer.flush()?;
139 Ok(self.writer)
140 }
141}
142impl<W: std::io::Write> std::io::Write for ZipCryptoWriter<W> {
143 fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
144 self.buffer.extend_from_slice(buf);
145 Ok(buf.len())
146 }
147 fn flush(&mut self) -> std::io::Result<()> {
148 Ok(())
149 }
150}
151
152/// A ZipCrypto reader with verified password
153pub struct ZipCryptoReaderValid<R> {
154 reader: ZipCryptoReader<R>,
155}
156
157impl<R: std::io::Read> std::io::Read for ZipCryptoReaderValid<R> {
158 fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
159 // Note: There might be potential for optimization. Inspiration can be found at:
160 // https://github.com/kornelski/7z/blob/master/CPP/7zip/Crypto/ZipCrypto.cpp
161
162 let result: Result = self.reader.file.read(buf);
163 for byte: &mut u8 in buf.iter_mut() {
164 *byte = self.reader.keys.decrypt_byte(*byte);
165 }
166 result
167 }
168}
169
170impl<R: std::io::Read> ZipCryptoReaderValid<R> {
171 /// Consumes this decoder, returning the underlying reader.
172 pub fn into_inner(self) -> R {
173 self.reader.file
174 }
175}
176
177static CRCTABLE: [u32; 256] = [
178 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
179 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
180 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
181 0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
182 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
183 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
184 0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
185 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
186 0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
187 0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
188 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
189 0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
190 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
191 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
192 0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
193 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
194 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
195 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
196 0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
197 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
198 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
199 0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
200 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
201 0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
202 0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
203 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
204 0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
205 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
206 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
207 0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
208 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
209 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d,
210];
211