Coverage Report

Created: 2026-07-10 07:15

next uncovered line (L), next uncovered region (R), next uncovered branch (B)
/src/zip/src/zipcrypto.rs
Line
Count
Source
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
6
use std::num::Wrapping;
7
8
/// A container to hold the current key state
9
#[derive(Clone, Copy)]
10
pub(crate) struct ZipCryptoKeys {
11
    key_0: Wrapping<u32>,
12
    key_1: Wrapping<u32>,
13
    key_2: Wrapping<u32>,
14
}
15
16
impl ZipCryptoKeys {
17
778
    fn new() -> ZipCryptoKeys {
18
778
        ZipCryptoKeys {
19
778
            key_0: Wrapping(0x12345678),
20
778
            key_1: Wrapping(0x23456789),
21
778
            key_2: Wrapping(0x34567890),
22
778
        }
23
778
    }
24
25
22.1M
    fn update(&mut self, input: u8) {
26
22.1M
        self.key_0 = ZipCryptoKeys::crc32(self.key_0, input);
27
22.1M
        self.key_1 =
28
22.1M
            (self.key_1 + (self.key_0 & Wrapping(0xff))) * Wrapping(0x08088405) + Wrapping(1);
29
22.1M
        self.key_2 = ZipCryptoKeys::crc32(self.key_2, (self.key_1 >> 24).0 as u8);
30
22.1M
    }
31
32
22.1M
    fn stream_byte(&mut self) -> u8 {
33
22.1M
        let temp: Wrapping<u16> = Wrapping(self.key_2.0 as u16) | Wrapping(3);
34
22.1M
        ((temp * (temp ^ Wrapping(1))) >> 8).0 as u8
35
22.1M
    }
36
37
22.1M
    fn decrypt_byte(&mut self, cipher_byte: u8) -> u8 {
38
22.1M
        let plain_byte: u8 = self.stream_byte() ^ cipher_byte;
39
22.1M
        self.update(plain_byte);
40
22.1M
        plain_byte
41
22.1M
    }
42
43
    #[allow(dead_code)]
44
0
    fn encrypt_byte(&mut self, plain_byte: u8) -> u8 {
45
0
        let cipher_byte: u8 = self.stream_byte() ^ plain_byte;
46
0
        self.update(plain_byte);
47
0
        cipher_byte
48
0
    }
49
50
44.2M
    fn crc32(crc: Wrapping<u32>, input: u8) -> Wrapping<u32> {
51
44.2M
        (crc >> 8) ^ Wrapping(CRCTABLE[((crc & Wrapping(0xff)).0 as u8 ^ input) as usize])
52
44.2M
    }
53
778
    pub(crate) fn derive(password: &[u8]) -> ZipCryptoKeys {
54
778
        let mut keys = ZipCryptoKeys::new();
55
3.66k
        for byte in password.iter() {
56
3.66k
            keys.update(*byte);
57
3.66k
        }
58
778
        keys
59
778
    }
60
}
61
62
/// A ZipCrypto reader with unverified password
63
pub struct ZipCryptoReader<R> {
64
    file: R,
65
    keys: ZipCryptoKeys,
66
}
67
68
pub enum ZipCryptoValidator {
69
    PkzipCrc32(u32),
70
    InfoZipMsdosTime(u16),
71
}
72
73
impl<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
778
    pub fn new(file: R, password: &[u8]) -> ZipCryptoReader<R> {
81
778
        ZipCryptoReader {
82
778
            file,
83
778
            keys: ZipCryptoKeys::derive(password),
84
778
        }
85
778
    }
86
87
    /// Read the ZipCrypto header bytes and validate the password.
88
778
    pub fn validate(
89
778
        mut self,
90
778
        validator: ZipCryptoValidator,
91
778
    ) -> Result<Option<ZipCryptoReaderValid<R>>, std::io::Error> {
92
        // ZipCrypto prefixes a file with a 12 byte header
93
778
        let mut header_buf = [0u8; 12];
94
778
        self.file.read_exact(&mut header_buf)?;
95
9.33k
        for byte in header_buf.iter_mut() {
96
9.33k
            *byte = self.keys.decrypt_byte(*byte);
97
9.33k
        }
98
99
778
        match validator {
100
217
            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
217
                if (crc32_plaintext >> 24) as u8 != header_buf[11] {
106
2
                    return Ok(None); // Wrong password
107
215
                }
108
            }
109
561
            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
561
                if (last_mod_time >> 8) as u8 != header_buf[11] {
118
397
                    return Ok(None); // Wrong password
119
164
                }
120
            }
121
        }
122
123
379
        Ok(Some(ZipCryptoReaderValid { reader: self }))
124
778
    }
125
}
126
pub(crate) struct ZipCryptoWriter<W> {
127
    pub(crate) writer: W,
128
    pub(crate) buffer: Vec<u8>,
129
    pub(crate) keys: ZipCryptoKeys,
130
}
131
impl<W: std::io::Write> ZipCryptoWriter<W> {
132
0
    pub(crate) fn finish(mut self, crc32: u32) -> std::io::Result<W> {
133
0
        self.buffer[11] = (crc32 >> 24) as u8;
134
0
        for byte in self.buffer.iter_mut() {
135
0
            *byte = self.keys.encrypt_byte(*byte);
136
0
        }
137
0
        self.writer.write_all(&self.buffer)?;
138
0
        self.writer.flush()?;
139
0
        Ok(self.writer)
140
0
    }
141
}
142
impl<W: std::io::Write> std::io::Write for ZipCryptoWriter<W> {
143
0
    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
144
0
        self.buffer.extend_from_slice(buf);
145
0
        Ok(buf.len())
146
0
    }
147
0
    fn flush(&mut self) -> std::io::Result<()> {
148
0
        Ok(())
149
0
    }
150
}
151
152
/// A ZipCrypto reader with verified password
153
pub struct ZipCryptoReaderValid<R> {
154
    reader: ZipCryptoReader<R>,
155
}
156
157
impl<R: std::io::Read> std::io::Read for ZipCryptoReaderValid<R> {
158
1.87k
    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
1.87k
        let result = self.reader.file.read(buf);
163
22.1M
        for byte in buf.iter_mut() {
164
22.1M
            *byte = self.reader.keys.decrypt_byte(*byte);
165
22.1M
        }
166
1.87k
        result
167
1.87k
    }
168
}
169
170
impl<R: std::io::Read> ZipCryptoReaderValid<R> {
171
    /// Consumes this decoder, returning the underlying reader.
172
0
    pub fn into_inner(self) -> R {
173
0
        self.reader.file
174
0
    }
175
}
176
177
static 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
];