src/crypto.rs

   1 use openssl::{symm, sha::sha256};
   2 use rand::prelude::*;
   3
   4 use crate::consts;
   5
   6 #[derive(Debug)]
   7 pub enum KeyError {
   8     UnableToDecodeBase64Key,
   9     WrongKeyLength,
  10 }
  11
  12 #[derive(Debug)]
  13 pub enum EncryptError {
  14     KeyError(KeyError),
  15     UnableToEncrypt,
  16 }
  17
  18 #[derive(Debug)]
  19 pub enum DecryptError {
  20     KeyError(KeyError),
  21     WrongMessageVersion,
  22     UnableToDecodeBase64Message,
  23     UnableToDecrypt,
  24     UnableToDecodeMessageAsUTF8String,
  25     HashMismatch,
  26 }
  27
  28 fn decode_key(key: &str) -> Result<Vec<u8>, KeyError> {
  29     match base64::decode(key) {
  30         Ok(k) => if k.len() != 16 { Err(KeyError::WrongKeyLength) } else { Ok(k) },
  31         Err(_e) => Err(KeyError::UnableToDecodeBase64Key)
  32     }
  33 }
  34
  35 /// Encrypt the given text with the given key. The key length must be 128 bits encoded in base64.
  36 /// Ouput format: "1" + base_64(<IV> + <hash(message)> + <aes(message)>)
  37 /// IV: 16 bytes randomized.
  38 /// Mode : CBC.
  39 pub fn encrypt(key: &str, plain_text: &str) -> Result<String, EncryptError> {
  40     let key_as_bytes = decode_key(key).map_err(EncryptError::KeyError)?;
  41
  42     let text_as_bytes = plain_text.as_bytes();
  43     let iv = rand::thread_rng().gen::<[u8; 16]>();
  44
  45     let cipher_text =
  46         symm::encrypt(symm::Cipher::aes_128_cbc(), &key_as_bytes, Some(&iv), text_as_bytes)
  47             .map_err(|_e| EncryptError::UnableToEncrypt)?;
  48
  49     let hash_text = sha256(&text_as_bytes);
  50
  51     let mut result: Vec<u8> = Vec::new();
  52     result.extend(&iv);
  53     result.extend(&hash_text);
  54     result.extend(&cipher_text);
  55
  56     Ok(String::from("1") + &base64::encode(&result))
  57 }
  58
  59 /// Decrypt the given text with the given key. The key length must be 128 bits encoded in base64.
  60 /// Input format: "1" + base_64(<IV> + <hash(message)> + <aes(message)>)
  61 pub fn decrypt(key: &str, cipher_text: &str) -> Result<String, DecryptError> {
  62     let key_as_bytes = decode_key(key).map_err(DecryptError::KeyError)?;
  63
  64     // Can't decrypt a message with the wrong version.
  65     if !cipher_text.starts_with(consts::CURRENT_MESSAGE_VERSION) { return Err(DecryptError::WrongMessageVersion) }
  66
  67     let cipher_text_bytes =
  68         base64::decode(&cipher_text.as_bytes()[consts::CURRENT_MESSAGE_VERSION.as_bytes().len()..])
  69             .map_err(|_e| DecryptError::UnableToDecodeBase64Message)?;
  70
  71     let iv = &cipher_text_bytes[0..16];
  72     let hash = &cipher_text_bytes[16..48];
  73     let encrypted_message = &cipher_text_bytes[48..];
  74
  75     let plain_message_bytes =
  76         symm::decrypt(symm::Cipher::aes_128_cbc(), &key_as_bytes, Some(iv), encrypted_message)
  77             .map_err(|_e| DecryptError::UnableToDecrypt)?;
  78
  79     if sha256(&plain_message_bytes) != hash { return Err(DecryptError::HashMismatch) }
  80
  81     let plain_message =
  82         String::from_utf8(plain_message_bytes)
  83             .map_err(|_e| DecryptError::UnableToDecodeMessageAsUTF8String)?;
  84
  85     Ok(plain_message)
  86 }