Check the size of the message before decrypting it.

[rup.git] / src / crypto.rs

diff --git a/src/crypto.rs b/src/crypto.rs
index 6d791eb..caf34f7 100644 (file)
--- a/src/crypto.rs
+++ b/src/crypto.rs
@@ -1,14 +1,89 @@
+use openssl::{symm, sha::sha256};\r
+use rand::prelude::*;\r
 \r
-pub fn encrypt(key: &str, plain_text: &str) -> String {\r
-    let key_as_bytes = base64::decode(key);\r
+use crate::consts;\r
 \r
+#[derive(Debug)]\r
+pub enum KeyError {\r
+    UnableToDecodeBase64Key,\r
+    WrongKeyLength,\r
+}\r
+\r
+#[derive(Debug)]\r
+pub enum EncryptError {\r
+    KeyError(KeyError),\r
+    UnableToEncrypt,\r
+}\r
+\r
+#[derive(Debug)]\r
+pub enum DecryptError {\r
+    KeyError(KeyError),\r
+    WrongMessageVersion,\r
+    MessageToShort,\r
+    UnableToDecodeBase64Message,\r
+    UnableToDecrypt,\r
+    UnableToDecodeMessageAsUTF8String,\r
+    HashMismatch,\r
+}\r
+\r
+fn decode_key(key: &str) -> Result<Vec<u8>, KeyError> {\r
+    match base64::decode(key) {\r
+        Ok(k) => if k.len() != 16 { Err(KeyError::WrongKeyLength) } else { Ok(k) },\r
+        Err(_e) => Err(KeyError::UnableToDecodeBase64Key)\r
+    }\r
+}\r
+\r
+/// Encrypt the given text with the given key. The key length must be 128 bits encoded in base64.\r
+/// Ouput format: "1" + base_64(<IV> + <hash(message)> + <aes(message)>)\r
+/// IV: 16 bytes randomized.\r
+/// Mode : CBC.\r
+pub fn encrypt(key: &str, plain_text: &str) -> Result<String, EncryptError> {\r
+    let key_as_bytes = decode_key(key).map_err(EncryptError::KeyError)?;\r
+\r
+    let text_as_bytes = plain_text.as_bytes();\r
+    let iv = rand::thread_rng().gen::<[u8; 16]>();\r
 \r
+    let cipher_text =\r
+        symm::encrypt(symm::Cipher::aes_128_cbc(), &key_as_bytes, Some(&iv), text_as_bytes)\r
+            .map_err(|_e| EncryptError::UnableToEncrypt)?;\r
 \r
-    String::new()\r
+    let hash_text = sha256(&text_as_bytes);\r
+\r
+    let mut result: Vec<u8> = Vec::new();\r
+    result.extend(&iv);\r
+    result.extend(&hash_text);\r
+    result.extend(&cipher_text);\r
+\r
+    Ok(String::from("1") + &base64::encode(&result))\r
 }\r
 \r
-pub fn decrypt(key: &str, cypher_text: &str) -> Option<String> {\r
+/// Decrypt the given text with the given key. The key length must be 128 bits encoded in base64.\r
+/// Input format: "1" + base_64(<IV> + <hash(message)> + <aes(message)>)\r
+pub fn decrypt(key: &str, cipher_text: &str) -> Result<String, DecryptError> {\r
+    let key_as_bytes = decode_key(key).map_err(DecryptError::KeyError)?;\r
+\r
+    // Can't decrypt a message with the wrong version.\r
+    if !cipher_text.starts_with(consts::CURRENT_MESSAGE_VERSION) { return Err(DecryptError::WrongMessageVersion) }\r
+\r
+    let cipher_text_bytes =\r
+        base64::decode(&cipher_text.as_bytes()[consts::CURRENT_MESSAGE_VERSION.as_bytes().len()..])\r
+            .map_err(|_e| DecryptError::UnableToDecodeBase64Message)?;\r
+\r
+    if cipher_text_bytes.len() <= 48 { return Err(DecryptError::MessageToShort) }\r
+\r
+    let iv = &cipher_text_bytes[0..16];\r
+    let hash = &cipher_text_bytes[16..48];\r
+    let encrypted_message = &cipher_text_bytes[48..];\r
+\r
+    let plain_message_bytes =\r
+        symm::decrypt(symm::Cipher::aes_128_cbc(), &key_as_bytes, Some(iv), encrypted_message)\r
+            .map_err(|_e| DecryptError::UnableToDecrypt)?;\r
+\r
+    if sha256(&plain_message_bytes) != hash { return Err(DecryptError::HashMismatch) }\r
+\r
+    let plain_message =\r
+        String::from_utf8(plain_message_bytes)\r
+            .map_err(|_e| DecryptError::UnableToDecodeMessageAsUTF8String)?;\r
 \r
-    println!("cypher: {}", cypher_text);\r
-    Some(String::new())\r
+    Ok(plain_message)\r
 }\r