From 4c411b76cad9cc735687dc739d2e2db5d00e5eac Mon Sep 17 00:00:00 2001
From: Igor Tolmachev <me@igorek.dev>
Date: Sun, 21 Jul 2024 16:59:14 +0900
Subject: Add AES encryption

---
 src/zip/encryption/aes.rs | 49 +++++++++++++++++++++++++++++++++++------------
 1 file changed, 37 insertions(+), 12 deletions(-)

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

diff --git a/src/zip/encryption/aes.rs b/src/zip/encryption/aes.rs
index 6f41aaa..b690482 100644
--- a/src/zip/encryption/aes.rs
+++ b/src/zip/encryption/aes.rs
@@ -1,4 +1,3 @@
-use crate::utils::ReadUtils;
 use aes::cipher::generic_array::GenericArray;
 use aes::cipher::BlockEncrypt;
 use std::io::{Read, Result as IoResult};
@@ -10,37 +9,63 @@ pub struct AesDecoder<Io: Read, Aes: BlockEncrypt> {
 
     counter: u128,
     block: [u8; 16],
-    cursor: usize,
+    lower: usize,
+    upper: usize,
 }
 
 impl<Io: Read, Aes: BlockEncrypt> AesDecoder<Io, Aes> {
-    pub fn new(mut io: Io, aes: Aes) -> IoResult<Self> {
-        let block = io.read_arr::<16>()?;
+    pub fn new(io: Io, aes: Aes) -> IoResult<Self> {
         let mut decoder = Self {
             io,
             aes,
-            counter: 1,
-            block,
-            cursor: 0,
+
+            counter: 0,
+            block: [0; 16],
+            lower: 0,
+            upper: 0,
         };
-        decoder.decrypt_block();
+
+        decoder.update_block()?;
+
         Ok(decoder)
     }
 
     #[inline]
-    fn decrypt_block(&mut self) {
+    fn update_block(&mut self) -> IoResult<()> {
+        self.upper = self.io.read(&mut self.block)?;
+        self.lower = 0;
+
+        self.counter += 1;
         let mut mask = self.counter.to_le_bytes();
+
         self.aes
             .encrypt_block(GenericArray::from_mut_slice(&mut mask));
+
         for (b, m) in self.block.iter_mut().zip(mask) {
             *b ^= m
         }
-        self.counter += 1;
+
+        Ok(())
     }
 }
 
 impl<Io: Read, Aes: BlockEncrypt> Read for AesDecoder<Io, Aes> {
-    fn read(&mut self, buf: &mut [u8]) -> IoResult<usize> {
-        todo!()
+    fn read(&mut self, mut buf: &mut [u8]) -> IoResult<usize> {
+        let mut bytes = 0;
+        while !buf.is_empty() && self.lower != self.upper {
+            for (to, fr) in buf.iter_mut().zip(&self.block[self.lower..self.upper]) {
+                *to = *fr
+            }
+
+            let consumed = buf.len().min(self.upper - self.lower);
+            buf = &mut buf[consumed..];
+            self.lower += consumed;
+            bytes += consumed;
+
+            if self.lower == 16 {
+                self.update_block()?;
+            }
+        }
+        Ok(bytes)
     }
 }
-- 
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