rust implementation

src/crypto.rs

@@ -0,0 +1,54 @@
+use std::fmt;
+
+use aes::Aes128;
+use base64::{engine::general_purpose::STANDARD, Engine as _};
+use cbc::{
+    cipher::{block_padding::Pkcs7, BlockDecryptMut, KeyIvInit},
+    Decryptor,
+};
+
+type Aes128CbcDec = Decryptor<Aes128>;
+
+#[derive(Debug)]
+pub enum CryptoError {
+    Base64(base64::DecodeError),
+    Aes(cbc::cipher::InvalidLength),
+    Unpad(cbc::cipher::block_padding::UnpadError),
+}
+
+impl fmt::Display for CryptoError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            CryptoError::Base64(e) => write!(f, "Base64 decode failed: {}", e),
+            CryptoError::Aes(e) => write!(f, "AES decryption failed: {}", e),
+            CryptoError::Unpad(e) => write!(f, "PKCS7 unpadding failed: {}", e),
+        }
+    }
+}
+
+impl std::error::Error for CryptoError {}
+
+pub fn decrypt(ciphertext_b64: &str, key: &str, iv: &str) -> Result<String, CryptoError> {
+    // 1. Base64 decode the ciphertext
+    let ciphertext = STANDARD
+        .decode(ciphertext_b64)
+        .map_err(CryptoError::Base64)?;
+
+    // 2. Initialize AES-128 in CBC mode
+    let key_bytes = key.as_bytes();
+    let iv_bytes = iv.as_bytes();
+    let decryptor = Aes128CbcDec::new_from_slices(key_bytes, iv_bytes).map_err(CryptoError::Aes)?;
+
+    // 3. Decrypt the ciphertext, handling padding
+    let decrypted_len = ciphertext.len();
+    let mut plaintext = vec![0u8; decrypted_len];
+    let copy_len = ciphertext.len();
+    plaintext[..copy_len].copy_from_slice(&ciphertext);
+
+    let plaintext_slice = decryptor
+        .decrypt_padded_mut::<Pkcs7>(&mut plaintext[..decrypted_len])
+        .map_err(CryptoError::Unpad)?;
+
+    // 4. Convert plaintext to a UTF-8 string
+    Ok(String::from_utf8_lossy(plaintext_slice).to_string())
+}