src/crypto.rs

   1 use openssl::{symm, sha::sha256};
   2 use rand::prelude::*;
   3
   4 #[derive(Debug)]
   5 pub enum KeyError {
   6     UnableToDecodeBase64Key,
   7     WrongKeyLength,
   8 }
   9
  10 #[derive(Debug)]
  11 pub enum EncryptError {
  12     KeyError(KeyError),
  13     UnsupportedVersion(u8),
  14     UnableToEncrypt,
  15 }
  16
  17 #[derive(Debug)]
  18 pub enum DecryptError {
  19     KeyError(KeyError),
  20     UnableToParseVersion,
  21     UnsupportedVersion(u8),
  22     MessageToShort,
  23     UnableToDecodeBase64Message,
  24     UnableToDecrypt,
  25     UnableToDecodeMessageAsUTF8String,
  26     HashMismatch,
  27 }
  28
  29 fn decode_key(key: &str) -> Result<Vec<u8>, KeyError> {
  30     match base64::decode(key) {
  31         Ok(k) => if k.len() != 16 { Err(KeyError::WrongKeyLength) } else { Ok(k) },
  32         Err(_e) => Err(KeyError::UnableToDecodeBase64Key)
  33     }
  34 }
  35
  36 /// Encrypt the given text with the given key (first version). The key length must be 128 bits encoded in base64.
  37 /// Ouput formats:
  38 /// * 'version' = 1: "1" + base_64(<IV> + hash(message) + aes(message))
  39 /// * 'version' = 2: "2" + base_64(<IV> + aes(hash(message) + message))
  40 /// IV: 16 bytes randomized.
  41 /// Mode : CBC.
  42 pub fn encrypt(key: &str, plain_text: &str, version: u8) -> Result<String, EncryptError> {
  43     let key_as_bytes = decode_key(key).map_err(EncryptError::KeyError)?;
  44
  45     let text_as_bytes = plain_text.as_bytes();
  46     let hash_text = sha256(&text_as_bytes);
  47     let iv = rand::thread_rng().gen::<[u8; 16]>();
  48
  49     let cipher_text =
  50         if version == 1 {
  51             symm::encrypt(symm::Cipher::aes_128_cbc(), &key_as_bytes, Some(&iv), text_as_bytes)
  52                 .map_err(|_e| EncryptError::UnableToEncrypt)?
  53         } else if version == 2 {
  54             symm::encrypt(symm::Cipher::aes_128_cbc(), &key_as_bytes, Some(&iv), &[&hash_text, text_as_bytes].concat())
  55                 .map_err(|_e| EncryptError::UnableToEncrypt)?
  56         } else {
  57             return Err(EncryptError::UnsupportedVersion(version))
  58         };
  59
  60     let mut result: Vec<u8> = Vec::new();
  61     result.extend(&iv);
  62
  63     if version == 1 {
  64         result.extend(&hash_text);
  65     }
  66
  67     result.extend(&cipher_text);
  68
  69     Ok(version.to_string() + &base64::encode(&result))
  70 }
  71
  72 /// Decrypt the given text with the given key. The key length must be 128 bits encoded in base64.
  73 /// Input formats:
  74 /// * version 1: "1" + base_64(<IV> + hash(message) + aes(message))
  75 /// * version 2: "2" + base_64(<IV> + aes(hash(message) + message))
  76 pub fn decrypt(key: &str, cipher_text: &str) -> Result<String, DecryptError> {
  77     let key_as_bytes = decode_key(key).map_err(DecryptError::KeyError)?;
  78
  79     // Can't decrypt a message with the wrong version.
  80     let first_char = &cipher_text[..1];
  81     let version: u8 = first_char.parse().map_err(|_e| DecryptError::UnableToParseVersion)?;
  82
  83     if version != 1 && version != 2 {
  84         return Err(DecryptError::UnsupportedVersion(version))
  85     }
  86
  87     let cipher_text_bytes =
  88         base64::decode(&cipher_text.as_bytes()[1..])
  89             .map_err(|_e| DecryptError::UnableToDecodeBase64Message)?;
  90
  91     if cipher_text_bytes.len() <= 48 { return Err(DecryptError::MessageToShort) }
  92
  93     let iv = &cipher_text_bytes[0..16];
  94
  95     let (plain_message_bytes, hash) =
  96         if version == 1 {
  97             let encrypted_message = &cipher_text_bytes[48..];
  98             (
  99                 symm::decrypt(symm::Cipher::aes_128_cbc(), &key_as_bytes, Some(iv), encrypted_message)
 100                     .map_err(|_e| DecryptError::UnableToDecrypt)?,
 101                 cipher_text_bytes[16..48].to_vec()
 102             )
 103         } else {
 104             let encrypted_message = &cipher_text_bytes[16..];
 105             let plain_text =
 106                 symm::decrypt(symm::Cipher::aes_128_cbc(), &key_as_bytes, Some(iv), encrypted_message)
 107                     .map_err(|_e| DecryptError::UnableToDecrypt)?;
 108             (
 109                 plain_text[32..].to_vec(),
 110                 plain_text[0..32].to_vec()
 111             )
 112         };
 113
 114     if sha256(&plain_message_bytes) != hash[..] { return Err(DecryptError::HashMismatch) }
 115
 116     let plain_message =
 117         String::from_utf8(plain_message_bytes)
 118             .map_err(|_e| DecryptError::UnableToDecodeMessageAsUTF8String)?;
 119
 120     Ok(plain_message)
 121 }