Bogus generates invalid Finnish Henkilötunnus

[niklashaetty]

Version Information

Software	Version(s)
Bogus NuGet Package	33.1.1
.NET Core?	3.1
.NET Full Framework?
Windows OS?	N/A
Linux OS?	N/A
Visual Studio?	N/A

What locale are you using with Bogus?

Default, en

What is the expected behavior?

API Extension method Bogus.Person.Henkilötunnus() to return a valid Henkilötunnus.

What is the actual behavior?

I believe the algorithm for calculating the control digit is wrong.

Please provide a stack trace.

N/A

Any possible solutions?

Implement the correct algorithm for the control digit: https://en.wikipedia.org/wiki/National_identification_number#Finland

How do you reproduce the issue?

   var person = new Faker<Person>()
                .RuleFor(p => p.DateOfBirth, f => DateTime.Parse("1989-07-14"))
                .CustomInstantiator(f => new Person())
                .Generate();
            
            var hetu = person.Henkilötunnus();

will generate a control digit of I (upper case i) which is not an allowed character

Do you have a unit test that can demonstrate the bug?

        [Fact]
        public void ShouldProduceValidHetu()
        {
            var person = new Person();
            var hetu = person.Henkilötunnus();
            var expectedControlDigit = CalculateControlDigit(hetu);
            var actualControlDigit = hetu[^1];
            Assert.Equal(expectedControlDigit, actualControlDigit);
        }

        private char CalculateControlDigit(string hetu)
        {
            const string allowedCharacters = "0123456789ABCDEFHJKLMNPRSTUVWXY";
            var removedDelimiters = hetu
                .Replace("-", string.Empty)
                .Replace("+", string.Empty)
                .Replace("A", string.Empty);
                
            var ddMMyyzzz =  
                removedDelimiters
                .Remove(removedDelimiters.Length - 1);
            var n = int.Parse(ddMMyyzzz) % 31;
            return allowedCharacters[n];
        }

Can you identify the location in Bogus' source code where the problem exists?

Bogus.Extensions.Finland.Henkilötunnus()

         var ddMMyy = $"{p.DateOfBirth:ddMMyy}";

         var n = int.Parse(ddMMyy) % 31;

         var q = n.ToString();
         if( n >= 10 )
            q = ((char)('A' + (n - 10))).ToString();

         //no idea if its female or male.
         var zzz = r.Replace("###");

zzz is created after the control digit has been set, which is wrong because the control digit depends on the zzz value.

If the bug is confirmed, would you be willing to submit a PR?

Yes, I wrote an implementation i think works above.

[bchavez]

Hi @niklashaetty , yes, this looks like a bug. At least according to:

https://fi.wikipedia.org/wiki/Henkil%C3%B6tunnus

it looks like the check character needs to use this table for a lookup value. Can you submit a PR with only the necessary changes to fix the issue?

If not, I can try to get to it this weekend.

Thanks, Brian

[niklashaetty]

@bchavez Yup, i fixed it on a local branch. Not allowed to push it to remote though. Do you have any restrictions in place?

[bchavez]

@niklashaetty nice. glad you have a fix. correct, this repo is protected (by default, on GitHub).

to contribute on GitHub:

• first you need to fork bchavez/Bogus to niklashaetty/Bogus;
• git clone niklashaetty/Bogus
• create an issue-392-fix branch
• commit the fix on issue-392-fix branch
• push your issue-392-fix branch to GitHub at niklashaetty/Bogus
• issue a pull request from niklasheatty/Bogus on issue-392-fix to bchavez/Bogus on master.

and that should do it.