This is a C# port of Bitwarden's random password algorithm.
A couple minor changes to this version from the original are:
Ideally the use of System.Random would be replaced with RNGCryptoServiceProvider but that's out of scope of my use for this right now.
| void Main() | |
| { | |
| var options = new PasswordOptions | |
| { | |
| Length = 13, | |
| MinLowercase = 2, | |
| MinNumbers = 2, | |
| MinSpecial = 1, | |
| MinUppercase = 2, | |
| UseLowercase = true, | |
| UseNumbers = true, | |
| UseSpecial = true, | |
| UseUppercase = true, | |
| }; | |
| RandomPasswordGenerator.Generate(options).Dump(); | |
| } | |
| public class PasswordOptions | |
| { | |
| public bool UseLowercase { get; set; } | |
| public bool UseUppercase { get; set; } | |
| public bool UseNumbers { get; set; } | |
| public bool UseSpecial { get; set; } | |
| public int MinLowercase { get; set; } | |
| public int MinUppercase { get; set; } | |
| public int MinNumbers { get; set; } | |
| public int MinSpecial { get; set; } | |
| public int Length { get; set; } | |
| } | |
| public class RandomPasswordGenerator | |
| { | |
| public static string Generate(PasswordOptions options) | |
| { | |
| const string lowercaseChars = "bcdfghjkmnpqrstvwxyz"; // no aeiou | |
| const string uppercaseChars = "BCDFGHJKLMNPQRSTVWXYZ"; // no AEIOU | |
| const string numberChars = "23456789"; // no 01 | |
| const string specialChars = "!@#$%^&*"; | |
| string allChars = ""; | |
| var positions = new List<char>(); | |
| if (options.UseLowercase) | |
| { | |
| allChars += lowercaseChars; | |
| if (options.MinLowercase > 0) | |
| { | |
| for (int i = 0; i < options.MinLowercase; i++) | |
| { | |
| positions.Add('l'); | |
| } | |
| } | |
| } | |
| if (options.UseUppercase) | |
| { | |
| allChars += uppercaseChars; | |
| if (options.UseUppercase && options.MinUppercase > 0) | |
| { | |
| for (int i = 0; i < options.MinUppercase; i++) | |
| { | |
| positions.Add('u'); | |
| } | |
| } | |
| } | |
| if (options.UseNumbers) | |
| { | |
| allChars += numberChars; | |
| if (options.UseNumbers && options.MinNumbers > 0) | |
| { | |
| for (int i = 0; i < options.MinNumbers; i++) | |
| { | |
| positions.Add('n'); | |
| } | |
| } | |
| } | |
| if (options.UseSpecial) | |
| { | |
| allChars += specialChars; | |
| if (options.UseSpecial && options.MinSpecial > 0) | |
| { | |
| for (int i = 0; i < options.MinSpecial; i++) | |
| { | |
| positions.Add('s'); | |
| } | |
| } | |
| } | |
| while (positions.Count < options.Length) | |
| { | |
| positions.Add('a'); | |
| } | |
| var rnd = new Random(); | |
| ShuffleList(rnd, positions); | |
| var password = ""; | |
| for (int i = 0; i < positions.Count; i++) | |
| { | |
| string positionChars = null; | |
| switch (positions[i]) | |
| { | |
| case 'l': | |
| positionChars = lowercaseChars; | |
| break; | |
| case 'u': | |
| positionChars = uppercaseChars; | |
| break; | |
| case 'n': | |
| positionChars = numberChars; | |
| break; | |
| case 's': | |
| positionChars = specialChars; | |
| break; | |
| case 'a': | |
| positionChars = allChars; | |
| break; | |
| default: | |
| break; | |
| } | |
| var randomCharIndex = rnd.Next(0, positionChars.Length - 1); | |
| var randomChar = positionChars[randomCharIndex]; | |
| // no consecutive characters in a row | |
| if (i > 0 && password[i - 1] == randomChar) | |
| { | |
| i--; | |
| continue; | |
| } | |
| password += randomChar; | |
| } | |
| return password; | |
| } | |
| private static void ShuffleList<T>(Random rnd, List<T> list) | |
| { | |
| var length = list.Count - 1; | |
| while (length > 0) | |
| { | |
| var i = rnd.Next(0, length); | |
| (list[i], list[length]) = (list[length], list[i]); | |
| length--; | |
| } | |
| } | |
| } |
@dantclee I used this to generate temporary passwords that were sent to users. Based on prior experiences it was safer to exclude vowels so they couldn't contain offensive words than it was to risk an angry user.
@dantclee I used this to generate temporary passwords that were sent to users. Based on prior experiences it was safer to exclude vowels so they couldn't contain offensive words than it was to risk an angry user.
Thank you for your reply.
There is a bug in the random next() - it never returns the max value...
I changed it to this
public override int Next(int minValue, int maxValue)
{
if (minValue > maxValue) throw new ArgumentOutOfRangeException(nameof(minValue));
if (minValue == maxValue) return minValue;
var diff = maxValue - minValue;
_rng.GetBytes(_uint32Buffer);
var rand = BitConverter.ToUInt32(_uint32Buffer, 0);
var remainder = rand % (diff + 1);
return minValue + (int) remainder;
}
@xt0rted Why do you exclude all vowels?