ssh-cipher: add round trip test (#371)

Adds a basic round trip encryption test for all supported ciphers

Author: tarcieri

ssh-cipher/tests/lib.rs

@@ -0,0 +1,43 @@
+use ssh_cipher::Cipher;
+
+#[test]
+fn round_trip() {
+    const MSG: &[u8] = b"Testing 1 2 3...";
+    const CIPHERS: &[Cipher] = &[
+        #[cfg(feature = "aes-cbc")]
+        Cipher::Aes128Cbc,
+        #[cfg(feature = "aes-cbc")]
+        Cipher::Aes192Cbc,
+        #[cfg(feature = "aes-cbc")]
+        Cipher::Aes256Cbc,
+        #[cfg(feature = "aes-ctr")]
+        Cipher::Aes128Ctr,
+        #[cfg(feature = "aes-ctr")]
+        Cipher::Aes192Ctr,
+        #[cfg(feature = "aes-ctr")]
+        Cipher::Aes256Ctr,
+        #[cfg(feature = "aes-gcm")]
+        Cipher::Aes128Gcm,
+        #[cfg(feature = "aes-gcm")]
+        Cipher::Aes256Gcm,
+        #[cfg(feature = "chacha20poly1305")]
+        Cipher::ChaCha20Poly1305,
+        #[cfg(feature = "tdes")]
+        Cipher::TDesCbc,
+    ];
+
+    for &cipher in CIPHERS {
+        let (key_len, iv_len) = cipher.key_and_iv_size().unwrap();
+
+        // TODO(tarcieri): randomize keys?
+        let key = vec![0; key_len];
+        let iv = vec![0; iv_len];
+        let mut buffer = Vec::from(MSG);
+
+        let tag = cipher.encrypt(&key, &iv, &mut buffer).unwrap();
+        assert_ne!(buffer, MSG);
+
+        cipher.decrypt(&key, &iv, &mut buffer, tag).unwrap();
+        assert_eq!(buffer, MSG);
+    }
+}