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Broken b64 implementation (Ugly and no padding)

master
Benoît 2 years ago
parent
commit
f8a7c5527a
  1. 95
      set1/chal1/src/main.rs

95
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 char_vec: Vec<char> = input.chars().collect();
let split = &char_vec.chunks(2)
.map(|chunk| chunk.iter().collect::<String>())
.collect::<Vec<_>>();
// 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 args: Vec<String> = env::args().collect();
let input = &args[1];
let mut input_str = String::new();
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!(" »");
// 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();
// Now we can unroll the base64 algorithm
// We need to : http://www.herongyang.com/Encoding/Base64-Encoding-Algorithm.html
print!("{}", BASE64_TABLE[tmp1]);
print!("{}", BASE64_TABLE[tmp2]);
print!("{}", BASE64_TABLE[tmp3]);
print!("{}", BASE64_TABLE[tmp4]);
}
println!();
}

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