feat: validate IBAN in backend

frappe/model/base_document.py

@@ -993,6 +993,7 @@ class BaseDocument:
 		from frappe.utils import (
 			split_emails,
 			validate_email_address,
+			validate_iban,
 			validate_name,
 			validate_phone_number,
 			validate_phone_number_with_country_code,
@@ -1031,6 +1032,9 @@ class BaseDocument:
 			if data_field_options == "URL":
 				validate_url(data, throw=True)
 
+			if data_field_options == "IBAN":
+				validate_iban(data, throw=True)
+
 	def _validate_constants(self):
 		if frappe.flags.in_import or self.is_new() or self.flags.ignore_validate_constants:
 			return

frappe/tests/test_utils.py

@@ -34,6 +34,7 @@ from frappe.utils import (
 	get_site_info,
 	get_sites,
 	get_url,
+	is_valid_iban,
 	money_in_words,
 	parse_and_map_trackers_from_url,
 	parse_timedelta,
@@ -479,6 +480,26 @@ class TestValidationUtils(IntegrationTestCase):
 		for name in invalid_names:
 			self.assertRaises(frappe.InvalidNameError, validate_name, name, True)
 
+	def test_validate_iban(self):
+		valid_ibans = [
+			"GB82 WEST 1234 5698 7654 32",
+			"DE91 1000 0000 0123 4567 89",
+			"FR76 3000 6000 0112 3456 7890 189",
+		]
+
+		invalid_ibans = [
+			# wrong checksum (3rd place)
+			"GB72 WEST 1234 5698 7654 32",
+			"DE81 1000 0000 0123 4567 89",
+			"FR66 3000 6000 0112 3456 7890 189",
+		]
+
+		for iban in valid_ibans:
+			self.assertTrue(is_valid_iban(iban))
+
+		for not_iban in invalid_ibans:
+			self.assertFalse(is_valid_iban(not_iban))
+
 
 class TestImage(IntegrationTestCase):
 	def test_strip_exif_data(self):

frappe/utils/__init__.py

@@ -261,6 +261,44 @@ def validate_url(
 	return is_valid
 
 
+def validate_iban(iban: str, throw: bool = False) -> bool:
+	from frappe import _
+
+	valid = is_valid_iban(iban)
+	if not valid and throw:
+		frappe.throw(frappe._("'{0}' is not a valid IBAN").format(frappe.bold(iban)))
+
+	return valid
+
+
+def is_valid_iban(iban: str) -> bool:
+	"""
+	Algorithm: https://en.wikipedia.org/wiki/International_Bank_Account_Number#Validating_the_IBAN
+	"""
+	if not iban:
+		return False
+
+	def encode_char(c):
+		# Position in the alphabet (A=1, B=2, ...) plus nine
+		return str(9 + ord(c) - 64)
+
+	# remove whitespaces, upper case to get the right number from ord()
+	iban = iban.replace(" ", "").upper()
+
+	# Move country code and checksum from the start to the end
+	flipped = iban[4:] + iban[:4]
+
+	# Encode characters as numbers
+	encoded = [encode_char(c) if ord(c) >= 65 and ord(c) <= 90 else c for c in flipped]
+
+	try:
+		to_check = int("".join(encoded))
+	except ValueError:
+		return False
+
+	return to_check % 97 == 1
+
+
 def random_string(length: int) -> str:
 	"""generate a random string"""
 	import string