feat: Add initiate transaction logic - paytm

feat: added checksum file from paytm

Added condition for sandbox & live

added paytm in schema choices

app/api/helpers/checksum.py

@@ -0,0 +1,139 @@
+# Checksum module from https://github.com/Paytm-Payments/Paytm_Web_Sample_Kit_Python
+
+import base64
+import string
+import random
+import hashlib
+
+from Crypto.Cipher import AES
+
+
+IV = "@@@@&&&&####$$$$"
+BLOCK_SIZE = 16
+
+
+def generate_checksum(param_dict, merchant_key, salt=None):
+    params_string = __get_param_string__(param_dict)
+    salt = salt if salt else __id_generator__(4)
+    final_string = '%s|%s' % (params_string, salt)
+
+    hasher = hashlib.sha256(final_string.encode())
+    hash_string = hasher.hexdigest()
+
+    hash_string += salt
+
+    return __encode__(hash_string, IV, merchant_key)
+
+
+def generate_refund_checksum(param_dict, merchant_key, salt=None):
+    for i in param_dict:
+        if("|" in param_dict[i]):
+            param_dict = {}
+            exit()
+    params_string = __get_param_string__(param_dict)
+    salt = salt if salt else __id_generator__(4)
+    final_string = '%s|%s' % (params_string, salt)
+
+    hasher = hashlib.sha256(final_string.encode())
+    hash_string = hasher.hexdigest()
+
+    hash_string += salt
+
+    return __encode__(hash_string, IV, merchant_key)
+
+
+def generate_checksum_by_str(param_str, merchant_key, salt=None):
+    params_string = param_str
+    salt = salt if salt else __id_generator__(4)
+    final_string = '%s|%s' % (params_string, salt)
+
+    hasher = hashlib.sha256(final_string.encode())
+    hash_string = hasher.hexdigest()
+
+    hash_string += salt
+
+    return __encode__(hash_string, IV, merchant_key)
+
+
+def verify_checksum(param_dict, merchant_key, checksum):
+    # Remove checksum
+    if 'CHECKSUMHASH' in param_dict:
+        param_dict.pop('CHECKSUMHASH')
+
+    # Get salt
+    paytm_hash = __decode__(checksum, IV, merchant_key)
+    salt = paytm_hash[-4:]
+    calculated_checksum = generate_checksum(param_dict, merchant_key, salt=salt)
+    return calculated_checksum == checksum
+
+
+def verify_checksum_by_str(param_str, merchant_key, checksum):
+    # Get salt
+    paytm_hash = __decode__(checksum, IV, merchant_key)
+    salt = paytm_hash[-4:]
+    calculated_checksum = generate_checksum_by_str(param_str, merchant_key, salt=salt)
+    return calculated_checksum == checksum
+
+
+def __id_generator__(size=6, chars=string.ascii_uppercase + string.digits + string.ascii_lowercase):
+    return ''.join(random.choice(chars) for _ in range(size))
+
+
+def __get_param_string__(params):
+    params_string = []
+    for key in sorted(params.keys()):
+        if("REFUND" in params[key] or "|" in params[key]):
+            exit()
+        value = params[key]
+        params_string.append('' if value == 'null' else str(value))
+    return '|'.join(params_string)
+
+
+def __pad__(string_literal):
+    return (string_literal + (BLOCK_SIZE - len(string_literal) % BLOCK_SIZE) *
+            chr(BLOCK_SIZE - len(string_literal) % BLOCK_SIZE))
+
+
+def __unpad__(string_literal):
+    return string_literal[0:-ord(string_literal[-1])]
+
+
+def __encode__(to_encode, iv, key):
+    # Pad
+    to_encode = __pad__(to_encode)
+    # Encrypt
+    c = AES.new(key, AES.MODE_CBC, iv)
+    to_encode = c.encrypt(to_encode)
+    # Encode
+    to_encode = base64.b64encode(to_encode)
+    return to_encode.decode("UTF-8")
+
+
+def __decode__(to_decode, iv, key):
+    # Decode
+    to_decode = base64.b64decode(to_decode)
+    # Decrypt
+    c = AES.new(key, AES.MODE_CBC, iv)
+    to_decode = c.decrypt(to_decode)
+    if type(to_decode) == bytes:
+        # convert bytes array to str.
+        to_decode = to_decode.decode()
+    # remove pad
+    return __unpad__(to_decode)
+
+
+if __name__ == "__main__":
+    params = {
+        "MID": "mid",
+        "ORDER_ID": "order_id",
+        "CUST_ID": "cust_id",
+        "TXN_AMOUNT": "1",
+        "CHANNEL_ID": "WEB",
+        "INDUSTRY_TYPE_ID": "Retail",
+        "WEBSITE": "xxxxxxxxxxx"
+    }
+
+    print(verify_checksum(
+        params, 'xxxxxxxxxxxxxxxx',
+        "CD5ndX8VVjlzjWbbYoAtKQIlvtXPypQYOg0Fi2AUYKXZA5XSHiRF0FDj7vQu6\
+        6S8MHx9NaDZ/uYm3WBOWHf+sDQAmTyxqUipA7i1nILlxrk="))

app/api/helpers/payment.py

@@ -7,6 +7,8 @@
 from forex_python.converter import CurrencyRates
 
 from app.api.helpers.cache import cache
+from app.settings import get_settings
+from app.api.helpers import checksum
 from app.api.helpers.exceptions import ForbiddenException, ConflictException
 from app.api.helpers.utilities import represents_int
 from app.models.stripe_authorization import StripeAuthorization
@@ -274,3 +276,17 @@ def charge_payment(order_identifier, token):
                 },
                 )
         return charge
+
+
+class PaytmPaymentsManager(object):
+    """
+    Class to manage PayTM payments
+    """
+
+    @staticmethod
+    def generate_checksum(paytm_params):
+        if get_settings()['paytm_mode'] == 'sandbox':
+            merchant_key = get_settings()['paytm_sandbox_secret']
+        else:
+            merchant_key = get_settings()['paytm_live_secret']
+        return checksum.generate_checksum_by_str(json.dumps(paytm_params["body"]), merchant_key)

app/api/orders.py

@@ -1,6 +1,9 @@
 import logging
+import json
 import pytz
 from datetime import datetime
+import requests
+
 
 import omise
 from flask import request, jsonify, Blueprint, url_for, redirect
@@ -10,6 +13,7 @@
 from marshmallow_jsonapi.flask import Schema
 from sqlalchemy.orm.exc import NoResultFound
 
+from app.settings import get_settings
 from app.api.bootstrap import api
 from app.api.data_layers.ChargesLayer import ChargesLayer
 from app.api.helpers.db import save_to_db, safe_query, safe_query_without_soft_deleted_entries
@@ -22,7 +26,7 @@
     send_notif_ticket_cancel
 from app.api.helpers.order import delete_related_attendees_for_order, set_expiry_for_order, \
     create_pdf_tickets_for_holder, create_onsite_attendees_for_order
-from app.api.helpers.payment import AliPayPaymentsManager, OmisePaymentsManager
+from app.api.helpers.payment import AliPayPaymentsManager, OmisePaymentsManager, PaytmPaymentsManager
 from app.api.helpers.payment import PayPalPaymentsManager
 from app.api.helpers.permission_manager import has_access
 from app.api.helpers.permissions import jwt_required
@@ -606,3 +610,45 @@ def omise_checkout(order_identifier):
         logging.info(f"Successful charge: {charge.id}.  Order ID: {order_identifier}")
 
         return redirect(make_frontend_url('orders/{}/view'.format(order_identifier)))
+
+
+@order_misc_routes.route('/orders/<string:order_identifier>/paytm/initiate-transaction', methods=['POST', 'GET'])
+def initiate_transaction(order_identifier):
+    """
+    Initiating a PayTM transaction to obtain the txn token
+    :param order_identifier:
+    :return: JSON response containing the signature & txn token
+    """
+    order = safe_query(db, Order, 'identifier', order_identifier, 'identifier')
+    paytm_mode = get_settings()['paytm_mode']
+    paytm_params = {}
+    # body parameters
+    paytm_params["body"] = {
+        "requestType": "Payment",
+        "mid": (get_settings()['paytm_sandbox_merchant'] if paytm_mode == 'sandbox'
+                else get_settings()['paytm_live_merchant']),
+        "websiteName": "eventyay",
+        "orderId": order.id,
+        "callbackUrl": "",
+        "txnAmount": {
+            "value": order.amount,
+            "currency": order.event.payment_currency,
+        },
+        "userInfo": {
+            "custId": order.user.id,
+        },
+    }
+    checksum = PaytmPaymentsManager.generate_checksum(paytm_params)
+    # head parameters
+    paytm_params["head"] = {
+        "signature"	: checksum
+    }
+    post_data = json.dumps(paytm_params)
+    if paytm_mode == 'sandbox':
+        url = "https://securegw-stage.paytm.in/theia/api/v1/initiateTransaction?mid={}&orderId={}".\
+              format(get_settings()['paytm_sandbox_merchant'], order.id)
+    else:
+        url = "https://securegw.paytm.in/theia/api/v1/initiateTransaction?mid={}&orderId={}".\
+              format(get_settings()['paytm_sandbox_merchant'], order.id)
+    response = requests.post(url, data=post_data, headers={"Content-type": "application/json"})
+    return response.json()

app/api/schema/orders.py

@@ -61,7 +61,7 @@ def initial_values(self, data):
     payment_mode = fields.Str(
                             default="free",
                             validate=validate.OneOf(choices=["free", "stripe", "paypal", "bank",
-                                                             "cheque", "onsite", "omise", "alipay"]),
+                                                             "cheque", "onsite", "omise", "alipay", "paytm"]),
                             allow_none=True)
     paid_via = fields.Str(dump_only=True)
     is_billing_enabled = fields.Boolean(default=False)

requirements/common.txt

@@ -32,6 +32,7 @@ stripe~=2.35.0
 xhtml2pdf~=0.2
 flask-caching~=1.4
 forex-python~=1.5
+pycrypto~=2.6.1
 oauth2~=1.9
 qrcode~=6.1
 python-magic~=0.4