AES

Tests/Unit/EncryptedRecordLimitTests.cs

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+using System.Reflection;
+using Esiur.Data;
+using Esiur.Protocol;
+using Esiur.Resource;
+using Esiur.Security.Cryptography;
+
+namespace Esiur.Tests.Unit;
+
+public class EncryptedRecordLimitTests
+{
+    [Fact]
+    public void OversizedPlaintext_IsRejectedBeforeCipherSequenceIsConsumed()
+    {
+        var warehouse = new Warehouse();
+        warehouse.Configuration.Encryption.MaximumRecordSize = 32;
+        var provider = new CountingEncryptionProvider();
+        var connection = new EpConnection();
+        connection.Session.EncryptionProvider = provider;
+        connection.Session.SymetricCipher = provider.Cipher;
+
+        typeof(EpConnection)
+            .GetField("_serverWarehouse", BindingFlags.Instance | BindingFlags.NonPublic)!
+            .SetValue(connection, warehouse);
+        var compose = typeof(EpConnection)
+            .GetMethod("ComposeEncryptedRecord", BindingFlags.Instance | BindingFlags.NonPublic)!;
+
+        var error = Assert.Throws<TargetInvocationException>(() =>
+            compose.Invoke(connection, new object[] { new byte[9] }));
+
+        Assert.IsType<ParserLimitException>(error.InnerException);
+        Assert.Equal(0, provider.Cipher.EncryptCalls);
+    }
+
+    sealed class CountingEncryptionProvider : IEncryptionProvider
+    {
+        public string DefaultName => "counting";
+        public uint MaximumRecordOverhead => 24;
+        public CountingCipher Cipher { get; } = new CountingCipher();
+        public ISymetricCipher CreateCipher(EncryptionContext context) => Cipher;
+    }
+
+    sealed class CountingCipher : ISymetricCipher
+    {
+        public int EncryptCalls { get; private set; }
+        public ushort Identifier => 0;
+
+        public byte[] Encrypt(byte[] data)
+        {
+            EncryptCalls++;
+            return new byte[data.Length + 24];
+        }
+
+        public byte[] Decrypt(byte[] data) => data;
+        public byte[] SetKey(byte[] key) => key;
+    }
+}