From b6877f107bd712e39a2d2c754b09dbcaa008cf20 Mon Sep 17 00:00:00 2001
From: CoolandonRS <49355953+CoolandonRS@users.noreply.github.com>
Date: Thu, 27 Jul 2023 20:40:53 -0600
Subject: [PATCH] AES support and refactoring

---
 keyring/AESUtil.cs        | 61 +++++++++++++++++++++++++++++++++++++++
 keyring/EncryptionUtil.cs | 35 ++++++++++++++++++++++
 keyring/RSAUtil.cs        | 47 +++++-------------------------
 3 files changed, 104 insertions(+), 39 deletions(-)
 create mode 100644 keyring/AESUtil.cs
 create mode 100644 keyring/EncryptionUtil.cs

diff --git a/keyring/AESUtil.cs b/keyring/AESUtil.cs
new file mode 100644
index 0000000..46fd3e7
--- /dev/null
+++ b/keyring/AESUtil.cs
@@ -0,0 +1,61 @@
+using System.Diagnostics.CodeAnalysis;
+using System.Security.Cryptography;
+using System.Text;
+
+namespace CoolandonRS.keyring; 
+
+public class AESUtil : EncryptionUtil {
+    private Aes aes;
+    private byte[] ivKey;
+    private int interactionCount;
+    private object @lock;
+    
+    public override byte[] Encrypt(byte[] b) {
+        lock (@lock) {
+            DeriveIV();
+            return aes.EncryptCbc(b, aes.IV);
+        }
+    }
+
+    public override byte[] Decrypt(byte[] b) {
+        lock (@lock) {
+            DeriveIV();
+            return aes.DecryptCbc(b, aes.IV);
+        }
+    }
+
+    public (byte[] key, byte[] ivKey) GetSecrets() {
+        lock (@lock) {
+            if (interactionCount != -1) throw new InvalidOperationException("This AESUtil has already been used. Secrets are not retrievable.");
+            return (aes.Key, ivKey);
+        }
+    }
+    
+    private static Aes MakeAes(byte[] key) {
+        var aes = Aes.Create();
+        aes.KeySize = key.Length;
+        aes.Key = key;
+        return aes;
+    }
+
+    private void DeriveIV() {
+        interactionCount++; 
+        aes.IV = Rfc2898DeriveBytes.Pbkdf2(ivKey, BitConverter.GetBytes(interactionCount), 15000, HashAlgorithmName.SHA256, 16);
+    }
+
+    private AESUtil(KeyType keyType, byte[] ivKey, Aes aes, Encoding? encoding = null) : base(keyType, encoding) {
+        if (keyType != KeyType.Symmetric) throw new InvalidOperationException("AESUtil only supports symmetric keys");
+        this.aes = aes;
+        this.ivKey = ivKey;
+        this.interactionCount = -1;
+    }
+    
+    /// <summary>
+    /// Generates a new AES key to use for the AESUtil
+    /// </summary>
+    public AESUtil(Encoding? encoding = null) : this(KeyType.Symmetric, RandomNumberGenerator.GetBytes(64), Aes.Create(), encoding) {
+    }
+    
+    public AESUtil(KeyType keyType, byte[] key, byte[] ivKey, Encoding? encoding = null) : this(keyType, ivKey, MakeAes(key), encoding) {
+    }
+}
\ No newline at end of file
diff --git a/keyring/EncryptionUtil.cs b/keyring/EncryptionUtil.cs
new file mode 100644
index 0000000..3cd9404
--- /dev/null
+++ b/keyring/EncryptionUtil.cs
@@ -0,0 +1,35 @@
+using System.Security.Cryptography;
+using System.Text;
+
+namespace CoolandonRS.keyring; 
+
+public abstract class EncryptionUtil {
+    protected readonly KeyType keyType;
+    protected readonly Encoding encoding;
+    
+    /// <summary>
+    /// Encrypts data using the stored key(s)
+    /// </summary>
+    /// <param name="dat">Data to encrypt</param>
+    /// <returns>Encrypted data</returns>
+    public abstract byte[] Encrypt(byte[] b);
+
+    public virtual byte[] EncryptStr(string s) => Encrypt(encoding.GetBytes(s));
+
+    /// <summary>
+    /// Decrypts data using the stored key(s)
+    /// </summary>
+    /// <param name="dat">Data to decrypt</param>
+    /// <returns>Decrypted Data</returns>
+    /// <exception cref="InvalidOperationException">Unable to decrypt</exception>
+    public abstract byte[] Decrypt(byte[] b);
+
+    public virtual string DecryptStr(byte[] b) => encoding.GetString(Decrypt(b));
+
+    public KeyType GetKeyType() => keyType;
+
+    protected EncryptionUtil(KeyType type, Encoding? encoding) {
+        this.keyType = type;
+        this.encoding = encoding ?? Encoding.UTF8;
+    }
+}
\ No newline at end of file
diff --git a/keyring/RSAUtil.cs b/keyring/RSAUtil.cs
index 72c4f29..f371448 100644
--- a/keyring/RSAUtil.cs
+++ b/keyring/RSAUtil.cs
@@ -1,4 +1,5 @@
-using System.Security.Cryptography;
+using System.CodeDom.Compiler;
+using System.Security.Cryptography;
 using System.Text;
 
 namespace CoolandonRS.keyring;
@@ -6,49 +7,19 @@ namespace CoolandonRS.keyring;
 /// <summary>
 /// Tool for using RSA Encryption/Decryption
 /// </summary>
-public class RSAUtil {
+public class RSAUtil : EncryptionUtil {
     private RSACryptoServiceProvider provider;
-    private readonly KeyType keyType;
     private Encoding encoding;
-
-    /// <summary>
-    /// Encrypts data using the stored key(s)
-    /// </summary>
-    /// <param name="dat">Data to encrypt</param>
-    /// <returns>Encrypted data</returns>
-    public byte[] Encrypt(byte[] dat) {
+    
+    public override byte[] Encrypt(byte[] dat) {
         return provider.Encrypt(dat, false);
     }
-
-    /// <summary>
-    /// Encodes and encrypts a string using the chosen encoding and stored key(s)
-    /// </summary>
-    /// <param name="str">String to encode and encrypt</param>
-    /// <returns>Encrypted data</returns>
-    public byte[] EncryptStr(string str) {
-        return Encrypt(encoding.GetBytes(str));
-    }
-
-    /// <summary>
-    /// Decrypts data using the stored key(s)
-    /// </summary>
-    /// <param name="dat">Data to decrypt</param>
-    /// <returns>Decrypted Data</returns>
-    /// <exception cref="InvalidOperationException"></exception>
-    public byte[] Decrypt(byte[] dat) {
+    
+    public override byte[] Decrypt(byte[] dat) {
         if (keyType != KeyType.Private) throw new InvalidOperationException("Cannot decrypt if keyType is not private");
         return provider.Decrypt(dat, false);
     }
 
-    /// <summary>
-    /// Decrypts data and encodes it into a string using the chosen encoding and stored key(s)
-    /// </summary>
-    /// <param name="dat">Encrypted data</param>
-    /// <returns>Decrypted string</returns>
-    public string DecryptStr(byte[] dat) {
-        return encoding.GetString(Decrypt(dat));
-    }
-    
     /// <summary>
     /// Creates an instance of RSAUtil
     /// </summary>
@@ -56,14 +27,12 @@ public class RSAUtil {
     /// <param name="pemContents">The contents of the PEM file</param>
     /// <param name="encoding">The text encoding to use for strings</param>
     /// <exception cref="InvalidOperationException">If you provide a symmetric key</exception>
-    public RSAUtil(KeyType keyType, string pemContents, Encoding? encoding = null) {
+    public RSAUtil(KeyType keyType, string pemContents, Encoding? encoding = null) : base(keyType, encoding) {
         if (keyType == KeyType.Symmetric) throw new InvalidOperationException("RSAUtil does not support symmetric keys");
         // ReSharper disable once LocalVariableHidesMember // Intentional
         var provider = new RSACryptoServiceProvider();
         provider.ImportFromPem(pemContents);
         if (keyType == KeyType.Private && provider.PublicOnly) throw new ArgumentException("keyType reported as private; no private key found.");
-        this.keyType = keyType;
         this.provider = provider;
-        this.encoding = encoding ?? Encoding.UTF8;
     }
 }
\ No newline at end of file