1 files changed, 105 insertions, 0 deletions

diff --git a/src/zip/encryption/weak.rs b/src/zip/encryption/weak.rs
new file mode 100644
index 0000000..144cd53
--- /dev/null
+++ b/src/zip/encryption/weak.rs
@@ -0,0 +1,105 @@
+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 i = 0;
+    while i <= 255 {
+        let mut t = i as u32;
+
+        let mut j = 0;
+        while j < 8 {
+            if (t & 1) > 0 {
+                t = (t >> 1) ^ 0xEDB88320
+            } else {
+                t >>= 1
+            }
+            j += 1;
+        }
+
+        table[i] = t;
+        i += 1
+    }
+
+    table
+}
+
+fn crc32(byte: u8, crc: u32) -> u32 {
+    (crc >> 8) ^ TABLE[((crc & 0xFF) as u8 ^ byte) as usize]
+}
+
+pub struct Keys {
+    key0: u32,
+    key1: u32,
+    key2: u32,
+}
+
+impl Keys {
+    pub fn new() -> Self {
+        Self {
+            key0: 305419896,
+            key1: 591751049,
+            key2: 878082192,
+        }
+    }
+
+    fn update(&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);
+    }
+
+    pub fn set_password(&mut self, passwd: &[u8]) {
+        for b in passwd {
+            self.update(*b)
+        }
+    }
+
+    pub fn set_header(&mut self, header: [u8; 12]) -> u8 {
+        for b in &header[..11] {
+            self.decode_byte(*b);
+        }
+        self.decode_byte(header[11])
+    }
+
+    #[allow(dead_code)]
+    pub fn encode_bytes(&mut self, byte: u8) -> u8 {
+        let key = self.key2 | 2;
+        self.update(byte);
+        byte ^ ((key.wrapping_mul(key ^ 1)) >> 8) as u8
+    }
+
+    pub fn decode_byte(&mut self, byte: u8) -> u8 {
+        let key = self.key2 | 2;
+        let byte = byte ^ ((key.wrapping_mul(key ^ 1)) >> 8) as u8;
+        self.update(byte);
+        byte
+    }
+}
+
+pub struct WeakDecoder<Io: Read> {
+    io: Io,
+    keys: Keys,
+}
+
+impl<Io: Read> WeakDecoder<Io> {
+    pub fn new(io: Io, keys: Keys) -> Self {
+        WeakDecoder { io, keys }
+    }
+}
+
+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.keys.decode_byte(buf[i]);
+        }
+        Ok(bytes)
+    }
+}