Core/SSL: AES-256-GCM encryption and decryption (#266)

autotest/AES256/AES256.upp

@@ -0,0 +1,10 @@
+uses
+	Core,
+	Core/SSL;
+
+file
+	main.cpp;
+
+mainconfig
+	"" = "";
+

autotest/AES256/main.cpp

@@ -0,0 +1,85 @@
+#include <Core/Core.h>
+#include <Core/SSL/SSL.h>
+
+using namespace Upp;
+
+
+CONSOLE_APP_MAIN
+{
+    StdLogSetup(LOG_FILE | LOG_COUT);
+    
+    const String password = "password@!^+1234";
+    const String original = "data: username=admin; password=12345!";
+    
+    // Encrypt must succeed and NOT match original
+    String encrypted = AES256Encrypt(original, password);
+    ASSERT(!encrypted.IsVoid());
+    ASSERT(encrypted != original);
+
+     // Decrypt must succeed and match original
+    String decrypted = AES256Decrypt(encrypted, password);
+    ASSERT(decrypted == original);
+
+    // Wrong password should fail
+    ASSERT(AES256Decrypt(encrypted, "wrong_password").IsVoid());
+
+    // Empty string encryption/decryption
+    encrypted = AES256Encrypt("", password);
+    ASSERT(encrypted.IsVoid());
+    decrypted = AES256Decrypt(encrypted, password);
+    ASSERT(decrypted.IsVoid());
+
+    // Multiple encryptions of same blob yield different cipherblobs (non-deterministic output)
+    String encrypted2 = AES256Encrypt(original, password);
+    String encrypted3 = AES256Encrypt(original, password);
+    ASSERT(encrypted2 != encrypted3);
+
+    // Decrypt both variants
+    ASSERT(AES256Decrypt(encrypted2, password) == original);
+    ASSERT(AES256Decrypt(encrypted3, password) == original);
+
+    // Allow empty passwords
+    encrypted = AES256Encrypt(original, Null);
+    decrypted = AES256Decrypt(encrypted, Null);
+    ASSERT(original == decrypted);
+
+	// Tampering
+    StringBuffer tampered = encrypted;
+    tampered[tampered.GetLength() - 1]^= 0x01;
+    ASSERT(AES256Decrypt(tampered, password).IsVoid());
+
+    // Large input (to ensure stream-based encryption works)
+    String large_string('A', 1024 * 1024 * 4);
+    encrypted = AES256Encrypt(large_string, password);
+    decrypted = AES256Decrypt(encrypted, password);
+    ASSERT(!encrypted.IsVoid());
+    ASSERT(!decrypted.IsVoid());
+    ASSERT(large_string == decrypted);
+
+    // Large input + tampering
+    tampered = encrypted;
+    tampered[tampered.GetLength() - 1] ^= 0x01;
+    ASSERT(AES256Decrypt(tampered, password).IsVoid());
+
+	{
+	    const String filename = GetTempFileName();
+		{
+			// Write encrypted blob to a file
+			MemReadStream ms(large_string, large_string.GetLength());
+			FileOut fo(filename);
+			ASSERT(AES256Encrypt(ms, password, fo));
+		}
+		{
+			// Read encrypted blob from a file
+			StringStream ss;
+			FileIn fi(filename);
+			ASSERT(AES256Decrypt(fi, password, ss));
+			ASSERT(ss.GetResult() == large_string);
+		}
+		
+		if(FileExists(filename))
+			DeleteFile(filename);
+	}
+
+	LOG("================ OK");
+}