Ovi Ovi - 3 months ago 27
ASP.NET (C#) Question

Alternative to System.Web.Security.Membership.GeneratePassword in aspnetcore (netcoreapp1.0)

Is there any alternative to

System.Web.Security.Membership.GeneratePassword
in
AspNetCore
(
netcoreapp1.0
).

The easiest way would be to just use a
Guid.NewGuid().ToString("n")
which is long enough to be worthy of a password but it's not fully random.

Answer

Here's a class/method, based on the source of Membership.GeneratePassword of that works on .NET Core:

public static class Password
{
    private static readonly char[] Punctuations = "!@#$%^&*()_-+=[{]};:>|./?".ToCharArray();

    public static string Generate(int length, int numberOfNonAlphanumericCharacters)
    {
        if (length < 1 || length > 128)
        {
            throw new ArgumentException(nameof(length));
        }

        if (numberOfNonAlphanumericCharacters > length || numberOfNonAlphanumericCharacters < 0)
        {
            throw new ArgumentException(nameof(numberOfNonAlphanumericCharacters));
        }

        using (var rng = RandomNumberGenerator.Create())
        {
            var byteBuffer = new byte[length];

            rng.GetBytes(byteBuffer);

            var count = 0;
            var characterBuffer = new char[length];

            for (var iter = 0; iter < length; iter++)
            {
                var i = byteBuffer[iter] % 87;

                if (i < 10)
                {
                    characterBuffer[iter] = (char)('0' + i);
                }
                else if (i < 36)
                {
                    characterBuffer[iter] = (char)('A' + i - 10);
                }
                else if (i < 62)
                {
                    characterBuffer[iter] = (char)('a' + i - 36);
                }
                else
                {
                    characterBuffer[iter] = Punctuations[i - 62];
                    count++;
                }
            }

            if (count >= numberOfNonAlphanumericCharacters)
            {
                return new string(characterBuffer);
            }

            int j;
            var rand = new Random();

            for (j = 0; j < numberOfNonAlphanumericCharacters - count; j++)
            {
                int k;
                do
                {
                    k = rand.Next(0, length);
                }
                while (!char.IsLetterOrDigit(characterBuffer[k]));

                characterBuffer[k] = Punctuations[rand.Next(0, Punctuations.Length)];
            }

            return new string(characterBuffer);
        }
    }
}

I've omitted the do...while loop over the CrossSiteScriptingValidation.IsDangerousString. You can add that back in yourself if you need it.

You use it like this:

var password = Password.Generate(32, 12);

Also, make sure you reference "System.Security.Cryptography.Algorithms": "4.2.0".

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