PasswordManager.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace howto_password_tracker
{
    public partial class frmNewPassword : Form
    {
        public frmNewPassword()
        {
            InitializeComponent();
        }

        // Required implies allowed.
        private void chkRequireLowercase_CheckedChanged(object sender, EventArgs e)
        {
            if (chkRequireLowercase.Checked) chkAllowLowercase.Checked = true;
        }
        private void chkRequireUppercase_CheckedChanged(object sender, EventArgs e)
        {
            if (chkRequireUppercase.Checked) chkAllowUppercase.Checked = true;
        }
        private void chkRequireNumber_CheckedChanged(object sender, EventArgs e)
        {
            if (chkRequireNumber.Checked) chkAllowNumber.Checked = true;
        }
        private void chkRequireSpecial_CheckedChanged(object sender, EventArgs e)
        {
            if (chkRequireSpecial.Checked) chkAllowSpecial.Checked = true;
        }
        private void chkRequireUnderscore_CheckedChanged(object sender, EventArgs e)
        {
            if (chkRequireUnderscore.Checked) chkAllowUnderscore.Checked = true;
        }
        private void chkRequireSpace_CheckedChanged(object sender, EventArgs e)
        {
            if (chkRequireSpace.Checked) chkAllowSpace.Checked = true;
        }
        private void chkRequireOther_CheckedChanged(object sender, EventArgs e)
        {
            if (chkRequireOther.Checked) chkAllowOther.Checked = true;
        }

        // Not allowed implies not required.
        private void chkAllowLowercase_CheckedChanged(object sender, EventArgs e)
        {
            if (!chkAllowLowercase.Checked) chkRequireLowercase.Checked = false;
        }
        private void chkAllowUppercase_CheckedChanged(object sender, EventArgs e)
        {
            if (!chkAllowUppercase.Checked) chkRequireUppercase.Checked = false;
        }
        private void chkAllowNumber_CheckedChanged(object sender, EventArgs e)
        {
            if (!chkAllowNumber.Checked) chkRequireNumber.Checked = false;
        }
        private void chkAllowSpecial_CheckedChanged(object sender, EventArgs e)
        {
            if (!chkAllowSpecial.Checked) chkRequireSpecial.Checked = false;
        }
        private void chkAllowUnderscore_CheckedChanged(object sender, EventArgs e)
        {
            if (!chkAllowUnderscore.Checked) chkRequireUnderscore.Checked = false;
        }
        private void chkAllowSpace_CheckedChanged(object sender, EventArgs e)
        {
            if (!chkAllowSpace.Checked) chkRequireSpace.Checked = false;
        }
        private void chkAllowOther_CheckedChanged(object sender, EventArgs e)
        {
            if (!chkAllowOther.Checked) chkRequireOther.Checked = false;
        }

        // Generate a new password.
        private void btnGenerate_Click(object sender, EventArgs e)
        {
            try
            {
                txtPassword.Text = RandomPassword();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

        // Generate a password that meets the reuirements.
        private string RandomPassword()
        {
            const string LOWER = "abcdefghijklmnopqrstuvwxyz";
            const string UPPER = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
            const string NUMBER = "0123456789";
            const string SPECIAL = @"~!@#$%^&*():;[]{}<>,.?/\|";
            string other = txtOther.Text;
            if (chkRequireOther.Checked && (other.Length < 1))
            {
                MessageBox.Show("You cannot require characters from a blank string.",
                    "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                txtOther.Focus();
                return txtPassword.Text;
            }

            // Make a list of allowed characters.
            string allowed = "";
            if (chkAllowLowercase.Checked) allowed += LOWER;
            if (chkAllowUppercase.Checked) allowed += UPPER;
            if (chkAllowNumber.Checked) allowed += NUMBER;
            if (chkAllowSpecial.Checked) allowed += SPECIAL;
            if (chkAllowUnderscore.Checked) allowed += "_";
            if (chkAllowSpace.Checked) allowed += " ";
            if (chkAllowOther.Checked) allowed += other;

            // Pick the number of characters.
            int min_chars = int.Parse(txtMinLength.Text);
            int max_chars = int.Parse(txtMaxLength.Text);
            int num_chars = Crypto.RandomInteger(min_chars, max_chars);

            // Satisfy requirements.
            string password = "";
            if (chkRequireLowercase.Checked &&
                (password.IndexOfAny(LOWER.ToCharArray()) == -1))
                password += RandomChar(LOWER);
            if (chkRequireUppercase.Checked &&
                (password.IndexOfAny(UPPER.ToCharArray()) == -1))
                password += RandomChar(UPPER);
            if (chkRequireNumber.Checked &&
                (password.IndexOfAny(LOWER.ToCharArray()) == -1))
                password += RandomChar(NUMBER);
            if (chkRequireSpecial.Checked &&
                (password.IndexOfAny(SPECIAL.ToCharArray()) == -1))
                password += RandomChar(SPECIAL);
            if (chkRequireUnderscore.Checked &&
                (password.IndexOfAny("_".ToCharArray()) == -1))
                password += "_";
            if (chkRequireSpace.Checked &&
                (password.IndexOfAny(" ".ToCharArray()) == -1))
                password += " ";
            if (chkRequireOther.Checked &&
                (password.IndexOfAny(other.ToCharArray()) == -1))
                password += RandomChar(other);

            // Add the remaining characters randomly.
            while (password.Length < num_chars)
                password += allowed.Substring(
                    Crypto.RandomInteger(0, allowed.Length - 1), 1);

            // Randomize (to mix up the required characters at the front).
            password = RandomizeString(password);

            return password;
        }

        // Return a random character from a string.
        private string RandomChar(string str)
        {
            return str.Substring(Crypto.RandomInteger(0, str.Length - 1), 1);
        }

        // Return a random permutation of a string.
        private string RandomizeString(string str)
        {
            string result = "";
            while (str.Length > 0)
            {
                // Pick a random character.
                int i = Crypto.RandomInteger(0, str.Length - 1);
                result += str.Substring(i, 1);
                str = str.Remove(i, 1);
            }
            return result;
        }

        private void frmNewPassword_Load(object sender, EventArgs e)
        {

        }
    }
}