auth-pass/index.js

auth-pass is a lightweight & powerful password validation package that ensures smooth, secure, and password updates. No more weak passwords, no more reuse—just pure security vibes!

const commonPasswords = new Set([
    "password", "123456", "123456789", "qwerty", "abc123", "password1", "admin", "welcome",
    "123123", "iloveyou", "letmein", "football", "monkey", "shadow", "sunshine"
]);

function validatePasswordUpdate(oldPassword, newPassword, confirmPassword) {
    let errors = {};

    if (!oldPassword) {
        errors.oldPassword = "Old password is required.";
    }

    if (!newPassword) {
        errors.newPassword = "New password is required.";
    } else if (newPassword.length < 8) {
        errors.newPassword = "New password must be at least 8 characters long.";
    } else if (newPassword.length > 16) {
        errors.newPassword = "New password must be at most 16 characters long.";
    } else if (!/(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])/.test(newPassword)) {
        errors.newPassword = "New password must contain at least one uppercase letter, one lowercase letter, one number, and one special character.";
    } else if (commonPasswords.has(newPassword.toLowerCase())) {
        errors.newPassword = "New password is too common. Choose a stronger password.";
    } else if (levenshteinDistance(oldPassword, newPassword) < 4) {
        errors.newPassword = "New password is too similar to the old password. Use a more unique password.";
    }

    if (!confirmPassword) {
        errors.confirmPassword = "Confirm password is required.";
    } else if (confirmPassword !== newPassword) {
        errors.confirmPassword = "Confirm password does not match new password.";
    }

    return Object.keys(errors).length > 0 ? errors : null;
}

// Levenshtein Distance Algorithm (Checks similarity between old & new passwords)
function levenshteinDistance(s1, s2) {
    if (!s1.length) return s2.length;
    if (!s2.length) return s1.length;

    const matrix = Array.from({ length: s1.length + 1 }, (_, i) => [i]);
    for (let j = 1; j <= s2.length; j++) matrix[0][j] = j;

    for (let i = 1; i <= s1.length; i++) {
        for (let j = 1; j <= s2.length; j++) {
            const cost = s1[i - 1] === s2[j - 1] ? 0 : 1;
            matrix[i][j] = Math.min(
                matrix[i - 1][j] + 1,      // Deletion
                matrix[i][j - 1] + 1,      // Insertion
                matrix[i - 1][j - 1] + cost // Substitution
            );
        }
    }
    return matrix[s1.length][s2.length];
}

module.exports = validatePasswordUpdate;