added: ipn hash validation

sslcommerz_python/payment.py

@@ -3,6 +3,7 @@
 from uuid import uuid4
 import requests
 import json
+import hashlib
 
 import sslcommerz_python._constants as const
 
@@ -120,4 +121,39 @@ def validate_transaction(self, validation_id):
         else:
             response_data['status'] = 'FAILED'
             response_data['data'] = 'Validation failed due to status code ' + str(validation_response.status_code)
-        return response_data
+        return response_data
+
+
+    def validate_ipn_hash(self, ipn_data):
+        if self.key_check(ipn_data, 'verify_key') and self.key_check(ipn_data, 'verify_sign'):
+            check_params : Dict[str, str] = {}
+            verify_key = ipn_data['verify_key'].split(',')
+
+            for key in verify_key:
+                check_params[key] = ipn_data[key]
+
+            store_pass = self.sslc_store_pass.encode()
+            store_pass_hash = hashlib.md5(store_pass).hexdigest()
+            check_params['store_passwd'] = store_pass_hash
+            check_params = self.sort_keys(check_params)
+
+            sign_string = ''
+            for key in check_params:
+                sign_string += key[0] + '=' + str(key[1]) + '&'
+
+            sign_string = sign_string.strip('&')
+            sign_string_hash = hashlib.md5(sign_string.encode()).hexdigest()
+
+            if sign_string_hash == ipn_data['verify_sign']:
+                return True
+            return False
+
+    @staticmethod
+    def key_check(data_dict, check_key):
+        if check_key in data_dict.keys():
+            return True
+        return False
+
+    @staticmethod
+    def sort_keys(data_dict):
+        return [(key, data_dict[k]) for key in sorted(data_dict.keys())]