Password validation with regexp

Question

I am trying to write password validation function with regexp and don't know how to do it.

The regex package provided by the standard API of the Go language is different to other languages.

Have someone an idea, how this regexp pattern should looks like?

The pattern should validate:

/*
 * Password rules:
 * at least 7 letters
 * at least 1 number
 * at least 1 upper case
 * at least 1 special character
 */

Answer 1

That's actually impossible since Go's regex doesn't support backtracking.

However, it's easy to implement, a simple example:

func verifyPassword(s string) (sevenOrMore, number, upper, special bool) {
    letters := 0
    for _, c := range s {
        switch {
        case unicode.IsNumber(c):
            number = true
        case unicode.IsUpper(c):
            upper = true
            letters++
        case unicode.IsPunct(c) || unicode.IsSymbol(c):
            special = true
        case unicode.IsLetter(c) || c == ' ':
            letters++
        default:
            //return false, false, false, false
        }
    }
    sevenOrMore = letters >= 7
    return
}