From cc18a545a87ca616f05114d174690e5cc9614669 Mon Sep 17 00:00:00 2001
From: Igor Tolmachev <me@igorek.dev>
Date: Tue, 16 Jul 2024 17:24:33 +0900
Subject: Optimize encryption

- Add archive for testing encryption of compressed files
- Implement incorrect password check
- Use custom crc32 function
---
 src/zip/encryption.rs | 49 ++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 38 insertions(+), 11 deletions(-)

(limited to 'src/zip/encryption.rs')

diff --git a/src/zip/encryption.rs b/src/zip/encryption.rs
index 84e30d5..28a6bdb 100644
--- a/src/zip/encryption.rs
+++ b/src/zip/encryption.rs
@@ -1,12 +1,35 @@
 use crate::utils::ReadUtils;
-use crate::zip::ZipResult;
-use crc32fast::Hasher;
+use crate::zip::{ZipError, ZipResult};
 use std::io::{Read, Result as IoResult};
 
-fn crc32(byte: u8, crc32: u32) -> u32 {
-    let mut hasher = Hasher::new_with_initial(crc32 ^ 0xFFFFFFFF);
-    hasher.update(&[byte]);
-    hasher.finalize() ^ 0xFFFFFFFF
+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> {
@@ -17,7 +40,7 @@ pub struct WeakDecoder<Io: Read> {
 }
 
 impl<Io: Read> WeakDecoder<Io> {
-    pub fn new(io: Io, password: &str) -> ZipResult<Self> {
+    pub fn new(io: Io, check: u8, password: &[u8]) -> ZipResult<Self> {
         let mut decoder = Self {
             key0: 305419896,
             key1: 591751049,
@@ -25,11 +48,14 @@ impl<Io: Read> WeakDecoder<Io> {
             io,
         };
 
-        for c in password.chars() {
-            decoder.update_keys(c as u8)
+        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)
     }
@@ -46,7 +72,9 @@ impl<Io: Read> WeakDecoder<Io> {
 
     fn decode_byte(&mut self, byte: u8) -> u8 {
         let key = self.key2 | 2;
-        byte ^ (((key * (key ^ 1)) >> 8) as u8)
+        let byte = byte ^ ((key * (key ^ 1)) >> 8) as u8;
+        self.update_keys(byte);
+        byte
     }
 }
 
@@ -55,7 +83,6 @@ impl<Io: Read> Read for WeakDecoder<Io> {
         let bytes = self.io.read(buf)?;
         for i in 0..bytes {
             buf[i] = self.decode_byte(buf[i]);
-            self.update_keys(buf[i])
         }
         Ok(bytes)
     }
-- 
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