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A lexicon-driven AppView for ATProto.
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#[derive(Debug, thiserror::Error)]pub enum EncryptionError { #[error("Encryption key not configured")] KeyNotConfigured, #[error("Encryption failed")] EncryptionFailed, #[error("Decryption failed")] DecryptionFailed, #[error("Invalid ciphertext format")] InvalidFormat,}
const NONCE_SIZE: usize = 12;
/// Encrypt data using AES-256-GCM/// Returns: nonce || ciphertext || tag (concatenated)pub fn encrypt(key: &[u8; 32], plaintext: &[u8]) -> Result<Vec<u8>, EncryptionError> { let cipher = Aes256Gcm::new_from_slice(key).map_err(|_| EncryptionError::EncryptionFailed)?;
// Generate random nonce let mut nonce_bytes = [0u8; NONCE_SIZE]; rand::rng().fill_bytes(&mut nonce_bytes); let nonce = Nonce::from(nonce_bytes);
// Encrypt let ciphertext = cipher .encrypt(&nonce, plaintext) .map_err(|_| EncryptionError::EncryptionFailed)?;
// Concatenate: nonce || ciphertext let mut result = Vec::with_capacity(NONCE_SIZE + ciphertext.len()); result.extend_from_slice(&nonce_bytes); result.extend_from_slice(&ciphertext);
Ok(result)}
/// Decrypt data encrypted with encrypt()pub fn decrypt(key: &[u8; 32], ciphertext: &[u8]) -> Result<Vec<u8>, EncryptionError> { if ciphertext.len() < NONCE_SIZE + 16 { // Minimum: nonce + auth tag return Err(EncryptionError::InvalidFormat); }
let cipher = Aes256Gcm::new_from_slice(key).map_err(|_| EncryptionError::DecryptionFailed)?;
let mut nonce_bytes = [0u8; NONCE_SIZE]; nonce_bytes.copy_from_slice(&ciphertext[..NONCE_SIZE]); let nonce = Nonce::from(nonce_bytes); let encrypted = &ciphertext[NONCE_SIZE..];
cipher .decrypt(&nonce, encrypted) .map_err(|_| EncryptionError::DecryptionFailed)}
#[cfg(test)]mod tests { use super::*;
#[test] fn test_encrypt_decrypt_roundtrip() { let key = [0x42u8; 32]; let plaintext = b"hello world";
let ciphertext = encrypt(&key, plaintext).unwrap(); assert_ne!(&ciphertext[NONCE_SIZE..], plaintext);
let decrypted = decrypt(&key, &ciphertext).unwrap(); assert_eq!(decrypted, plaintext); }
#[test] fn test_different_nonces() { let key = [0x42u8; 32]; let plaintext = b"hello world";
let ct1 = encrypt(&key, plaintext).unwrap(); let ct2 = encrypt(&key, plaintext).unwrap();
// Same plaintext should produce different ciphertext (different nonces) assert_ne!(ct1, ct2);
// Both should decrypt correctly assert_eq!(decrypt(&key, &ct1).unwrap(), plaintext); assert_eq!(decrypt(&key, &ct2).unwrap(), plaintext); }
#[test] fn test_invalid_ciphertext() { let key = [0x42u8; 32];
// Too short assert!(matches!( decrypt(&key, &[0u8; 10]), Err(EncryptionError::InvalidFormat) ));
// Corrupted let mut ciphertext = encrypt(&key, b"hello").unwrap(); ciphertext[NONCE_SIZE] ^= 0xFF; assert!(matches!( decrypt(&key, &ciphertext), Err(EncryptionError::DecryptionFailed) )); }}