From f8a7c5527aa5b00169794a71af0dacb4924b6ae9 Mon Sep 17 00:00:00 2001
From: beneth <bmauduit@beneth.fr>
Date: Sun, 12 Apr 2020 19:08:43 +0200
Subject: [PATCH] Broken b64 implementation (Ugly and no padding)

---
 set1/chal1/src/main.rs | 91 ++++++++++++++++++++++++++++++++++--------
 1 file changed, 75 insertions(+), 16 deletions(-)

diff --git a/set1/chal1/src/main.rs b/set1/chal1/src/main.rs
index e912976..686174b 100644
--- a/set1/chal1/src/main.rs
+++ b/set1/chal1/src/main.rs
@@ -5,29 +5,88 @@
 ////
 
 use std::env;
+use std::convert::TryInto;
 
+static BASE64_TABLE: &'static [char] = &['A','B','C','D','E','F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V' ,'W' ,'X' ,'Y' ,'Z',
+                                         'a','b','c','d','e','f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v' ,'w' ,'x' ,'y' ,'z',
+                                         '0','1','2','3','4','5', '6', '7', '8', '9', '+', '/'];
+
+/// Convert Hex String to char
+///
+/// # Examples
+///
+/// ~~~
+/// hex_to_char("49") => I
+/// ~~~
+/// TODO: the name is not accurate. Take a string and convert to u8
 fn hex_to_char(s: &str) -> Result<char, std::num::ParseIntError> {
-    u8::from_str_radix(s, 16).map(|n| n as char)
+  u8::from_str_radix(s, 16).map(|n| n as char)
 }
 
 fn main() {
-    let args: Vec<String> = env::args().collect();
-    let input = &args[1];
+  let args: Vec<String> = env::args().collect();
+  let input = &args[1];
 
-    let char_vec: Vec<char> = input.chars().collect();
-    let split = &char_vec.chunks(2)
-        .map(|chunk| chunk.iter().collect::<String>())
-        .collect::<Vec<_>>();
+  let mut input_str = String::new();
 
-    // Printing the string in Ascii format - for decoding example
-    for (i, s) in split.iter().enumerate() {
-        match hex_to_char(s) {
-            Ok(s) => print!("{}", s),
-            Err(e) => println!("\nError decoding char '{}' at index {}", e, i),
-        }
+  let char_vec: Vec<char> = input.chars().collect();
+  let hex_char = &char_vec
+    .chunks(2)
+    .map(|chunk| chunk.iter().collect::<String>())
+    .collect::<Vec<_>>();
+
+  // Printing the string in Ascii format - for decoding example
+  print!("Input string in ASCII is : « ");
+  for (i, s) in hex_char.into_iter().enumerate() {
+    match hex_to_char(s) {
+      Ok(s) =>  input_str.push(s),
+      Err(e) => println!("\nError decoding char '{}' at index {}", e, i),
     }
-    println!();
+  }
+  println!(" »");
 
-    // Now we can unroll the base64 algorithm
-    // We need to : http://www.herongyang.com/Encoding/Base64-Encoding-Algorithm.html
+  // Convert hex_char : Vec<String> into Vec<u8>
+  // Warning: Panic if not base16
+  // See this with .map_err if we need to improve :
+  // https://play.rust-lang.org/?version=stable&mode=debug&edition=2015&gist=e241493d100ecaadac3c99f37d0f766f
+  let hex: Vec<u8> = hex_char
+    .into_iter()
+    .map(|i| u8::from_str_radix(i, 16).unwrap())
+    .collect();
+
+  println!(" Len is : {}, is it modulo 3-bytes ? {}",
+           &hex.len(),
+           if &hex.len()%3 == 0 { "true" } else { "false"}
+  );
+
+  print!("b64_encode({:?}) ==> ", &input_str);
+
+  // Ugly right ?
+  for j in (0..hex.len()).step_by(3) {
+    let mut arr = [0u8;4];
+
+    // Must handle Padding here !
+    // Index will be out of bound
+    // Find a way in rust to detect that ? or just compute here.
+    // Si padding 1 = '=' + arr[3] = 0
+    // Si padding 2 = '==' + arr[3] & arr[4] = 0
+    arr[0] = 0;
+    for i in 0..3 {
+      arr[i+1] = hex[i+j];
+    }
+    let tmp = u32::from_be_bytes(arr);
+    let tmp1:usize = ((tmp>>18) & 0x3F).try_into().unwrap();
+    let tmp2:usize = ((tmp>>12) & 0x3F).try_into().unwrap();
+
+    // If this fail we need to PAD '=='
+    let tmp3:usize = ((tmp>>6) & 0x3F).try_into().unwrap();
+    // If this fail we need to PAD '='
+    let tmp4:usize = ((tmp) & 0x3F).try_into().unwrap();
+
+    print!("{}", BASE64_TABLE[tmp1]);
+    print!("{}", BASE64_TABLE[tmp2]);
+    print!("{}", BASE64_TABLE[tmp3]);
+    print!("{}", BASE64_TABLE[tmp4]);
+  }
+  println!();
 }