Regex special characters required

Question

I need to create a regex to validate password.

It must contain at least 8 characters, of which it must have at least 1 letter, 1 number and 1 special character.

Answer 1

Regex Usada

This regex does the validation, you can test it here:

(?=.*[}{,.^?~=+\-_\/*\-+.\|])(?=.*[a-zA-Z])(?=.*[0-9]).{8,}

Remembering that you should use double escape where it has the character \, so in Java code all backslashes must be double \\.

---

Application in Java code

In Java code you can validate with String.matches, the way I showed below:

public class JavaFiddle
{
   public static void main(String[] args)
   {
     System.out.println("A{123456".matches("(?=.*[}{,.^?~=+\\-_\\/*\\-+.\\|])(?=.*[a-zA-Z])(?=.*[0-9]).{8,}")); //exemplo que passa
     System.out.println("ASD1ASDA".matches("(?=.*[}{,.^?~=+\\-_\\/*\\-+.\\|])(?=.*[a-zA-Z])(?=.*[0-9]).{8,}")); //exemplo que nao passa (falta caractere especial)
     System.out.println("ASDAS^^?".matches("(?=.*[}{,.^?~=+\\-_\\/*\\-+.\\|])(?=.*[a-zA-Z])(?=.*[0-9]).{8,}")); //exemplo que nao passa (falta numero)
     System.out.println("123^8542".matches("(?=.*[}{,.^?~=+\\-_\\/*\\-+.\\|])(?=.*[a-zA-Z])(?=.*[0-9]).{8,}")); //exemplo que nao passa (falta letra)
     System.out.println("WWEA^^1".matches("(?=.*[}{,.^?~=+\\-_\\/*\\-+.\\|])(?=.*[a-zA-Z])(?=.*[0-9]).{8,}")); //exemplo que nao passa (nao tem minimo de 8 caracteres)
   }
}

This code displays true on the console when it is a valid standard, and false for invalid patterns.
You can test this code on Javafiddle like I did too, just copy and paste the code from that reply.

NOTE: As it was not specified which would be the special characters I used as valid the following characters (,.^?~=+-_/*\+)
You can change the characters that enter as special characters in this part of regex:
(?=.*[}{,.^?~=+\-_\/*\-+.\|]), just don’t take the part (?= ... ), because it signals a Positive Lookahead, which is required to validate that there is at least one of the characters flagged in the group before starting capture.

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Explanation by Regex

• (?=.*...) - Is a Positive Lookahead which will ensure that the following character group MUST be in the string for it to be validated.
• [}{,.^?~=+\-_\/*\-+.\|] - Is the set defining which characters can be captured by Positive Lookahead.
• (?=.*...) - Is a Positive Lookahead which will ensure that the following character group MUST be in the string for it to be validated.
• [a-zA-Z] - It is the set that characterizes any letter character being uppercase or lowercase.
• (?=.*...) - Is a Positive Lookahead which will ensure that the following character group MUST be in the string for it to be validated.
• [0-9] - It is the set that characterizes any number between 0 and 9.
• .{8,} - After these validations, a sequence of any character that does not contain line breaks will be captured (signaled by .).
  And a minimum length of 8 characters (marked by {8,}), no maximum limit (if you want to set a limit you can put the maximum number of character after the ,).

EDITED
Thank you to the user @hkotsubo for warning me of my mistake

Answer 2

Good afternoon.

I’m using Fluentvalidation and I made some validations for password today. See if this helps you (If you have any questions about the code tell me):

using FluentValidation;
using System.Linq;
using System.Text.RegularExpressions;

namespace SaleTheaterTickets.Models.ViewModelValidators
{
    public class RegisterViewModelValidator : AbstractValidator<RegisterViewModel>
    {
        public RegisterViewModelValidator()
        {
            RuleFor(x => x.Email)
                .NotEmpty().WithMessage("Informe o e-mail")
                .EmailAddress().WithMessage("Digite um e-mail válido ([email protected])");
            RuleFor(x => x.Password)
                .NotEmpty().WithMessage("Informe a senha")
                .Length(6, 20).WithMessage("Senha deve ter no mínimo 6 e no máximo 20 caractéres")
                .Must(RequireDigit).WithMessage("Senha deve ter pelo menos 1 número")
                .Must(RequiredLowerCase).WithMessage("Senha deve ter pelo menos 1 caracter minúsculo")
                .Must(RequireUppercase).WithMessage("Senha deve ter pelo menos 1 caracter maiúsculo")
                .Must(RequireNonAlphanumeric).WithMessage("Digite pelo menos 1 caracter especial (@ ! & * ...)");
            RuleFor(x => x.ConfirmPassword)
                .NotEmpty().WithMessage("Confirme a senha")
                .Equal(x => x.Password).WithMessage("Senhas não conferem");
        }

        private bool RequireDigit(string password)
        {
            if (password.Any(x => char.IsDigit(x)))
            {
                return true;
            }
            return false;
        }

        private bool RequiredLowerCase(string password)
        {
            if (password.Any(x => char.IsLower(x)))
            {
                return true;
            }
            return false;
        }

        private bool RequireUppercase(string password)
        {
            if (password.Any(x => char.IsUpper(x)))
            {
                return true;
            }
            return false;
        }

        private bool RequireNonAlphanumeric(string password)
        {
            //if (password.Any(x => char.IsSymbol(x)))
            //{
            //    return true;
            //}
            //return false;

            if (Regex.IsMatch(password, "(?=.*[@#$%^&+=])"))
            {
                return true;
            }
            return false;
        }
    }
}

NOTE: The methods are English, but they serve the following:

Requiredigit - at least 1 number in the password Requiredlowercase - at least 1 lower case letter in password Requireuppercase - at least 1 uppercase letter in password Requirenonalphanumeric - at least one special character in the password

NOTE: Asp.Net Core Identity already does these checks, but I was not able to translate the messages that came as default, so I took and created each validation by myself (following the validations I saw in the documentation that Identity does for password) in order to generate my sentences in Portuguese.

I hope it helps you somehow!