Text Extraction Done, UI Fixes Done, Extracted Template Layout Saved in DB

docengine/app/core/aes.py

@@ -0,0 +1,38 @@
+import base64
+from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
+
+def decrypt(base64_input: str, secret: bytes) -> str | None:
+    try:
+        combined = base64.b64decode(base64_input)
+        
+        # IV length is 12 bytes in the Java implementation
+        iv_length = 12
+        if len(combined) <= iv_length + 16:
+            return None
+            
+        iv = combined[:iv_length]
+        
+        # Java AES/GCM appends a 16-byte authentication tag at the end of cipherBytes
+        # cryptography library expects it to be passed into the modes.GCM(iv, tag)
+        cipher_bytes_with_tag = combined[iv_length:]
+        actual_ciphertext = cipher_bytes_with_tag[:-16]
+        tag = cipher_bytes_with_tag[-16:]
+        
+        cipher = Cipher(algorithms.AES(secret), modes.GCM(iv, tag))
+        decryptor = cipher.decryptor()
+        
+        plain_bytes = decryptor.update(actual_ciphertext) + decryptor.finalize()
+        return plain_bytes.decode('utf-8')
+    except Exception:
+        return None
+
+def get_string_value(encrypted_id: str, secret: str, secret_key_internal: str) -> str | None:
+    if not secret or not secret_key_internal:
+        return None
+    try:
+        # Replicate Java's logic: (s + secretKeyInternal).substring(0, Math.min(..., 16))
+        combined_str = secret + secret_key_internal
+        combined_secret = combined_str[:16].encode('utf-8')
+        return decrypt(encrypted_id, combined_secret)
+    except Exception:
+        return None