Last week, I had the opportunity to help implement and integrate a strong password policy to the legacy web application developed using ASP technology. The solution I proposed was to use jQuery to display the password strength meter to help users create strong password. Then one of my colleagues had asked "Do we have to modify the client-side script, code behind and password policy page if the client decided to alter the password policy?" The answer is "no", thanks to jQuery, the client-side script and code behind can share the same XML file. The password policy information is stored to an XML file and the client-side script and code behind are using the information in the XML file to perform the password strength validation.
I found several fine jQuery plug-in to display the user's password strength but I prefer to have something somewhat similar to the ASP.NET AJAX PasswordStrength control. After spending some time doing research, I was able to find all the necessary resources and assemble the jQuery plug-in to achieve the goal. Listed below are the features of the plug-in and I have put together a demo, everyone are welcome to download it. - Display password strength indicator in text and progress bar meter.
- The password policy, bar color and width are stored in the XML file and consume by the client-side and server side
- Use XSLT to transform the password policy XML file into HTML.
Figure 1
Shown below is the content of the sample application. If you want to test the Classic ASP code, deploy the application to your IIS Web Server. The local ASP.NET Development Server does not support Classic ASP. Figure 2
 • Default.aspx – sample code in ASP.NET c# with MasterPage
• Default.aspx2 – sample code in ASP.NET c# without MasterPage
• Password_strength_Indicator.asp – sample code in Classic ASP
• jQuery_Password_Strength_Indicator.htm – sample code in HTML
• PasswordPolicy.xml – contains password policy information
• Password.xslt – to transform PasswordPoclicy.xml file into HTML format
• jQuery.password-strength.js –this is the plug-in I have created
• Download latest jQuery library from here In this section, I'll touch base briefly with the contents in the jQuery.password-strength.js file. The code is very straight forward and comments are included. There is a jQuery AJAX request to read the XML file and populate the local variables based on the data in the XML file. If you are unsure of the relative URL, I would recommend using absolute URL to your XML file. The getStrengthInfo() function contains the logic to check the password strength and return appropriate message based on user input. The password strength meter bar and text position are relative to the Textbox position. Shown below is the code in the jQuery.password-strength.js file. Listing 1 (function($) {
var password_Strength = new function() {
//return count that match the regular expression
this.countRegExp = function(passwordVal, regx) {
var match = passwordVal.match(regx);
return match ? match.length : 0;
}
this.getStrengthInfo = function(passwordVal) {
var len = passwordVal.length;
var pStrength = 0; //password strength
var msg = "", inValidChars = ""; //message
//get special characters from xml file
var allowableSpecilaChars = new RegExp("[" + password_settings.specialChars + "]", "g")
var nums = this.countRegExp(passwordVal, /\d/g), //numbers
lowers = this.countRegExp(passwordVal, /[a-z]/g),
uppers = this.countRegExp(passwordVal, /[A-Z]/g), //upper case
specials = this.countRegExp(passwordVal, allowableSpecilaChars), //special characters
spaces = this.countRegExp(passwordVal, /\s/g);
//check for invalid characters
inValidChars = passwordVal.replace(/[a-z]/gi, "") + inValidChars.replace(/\d/g, "");
inValidChars = inValidChars.replace(/\d/g, "");
inValidChars = inValidChars.replace(allowableSpecilaChars, "");
//check space
if (spaces > 0) {
return "No spaces!";
}
//invalid characters
if (inValidChars !== '') {
return "Invalid character: " + inValidChars;
}
//max length
if (len > password_settings.maxLength) {
return "Password too long!";
}
//GET NUMBER OF CHARACTERS left
if ((specials + uppers + nums + lowers) < password_settings.minLength) {
msg += password_settings.minLength - (specials + uppers + nums + lowers) + " more characters, ";
}
//at the "at least" at the front
if (specials == 0 || uppers == 0 || nums == 0 || lowers == 0) {
msg += "At least ";
}
//GET NUMBERS
if (nums >= password_settings.numberLength) {
nums = password_settings.numberLength;
}
else {
msg += (password_settings.numberLength - nums) + " more numbers, ";
}
//special characters
if (specials >= password_settings.specialLength) {
specials = password_settings.specialLength
}
else {
msg += (password_settings.specialLength - specials) + " more symbol, ";
}
//upper case letter
if (uppers >= password_settings.upperLength) {
uppers = password_settings.upperLength
}
else {
msg += (password_settings.upperLength - uppers) + " Upper case characters, ";
}
//strength for length
if ((len - (uppers + specials + nums)) >= (password_settings.minLength - password_settings.numberLength - password_settings.specialLength - password_settings.upperLength)) {
pStrength += (password_settings.minLength - password_settings.numberLength - password_settings.specialLength - password_settings.upperLength);
}
else {
pStrength += (len - (uppers + specials + nums));
}
//password strength
pStrength += uppers + specials + nums;
//detect missing lower case character
if (lowers === 0) {
if (pStrength > 1) {
pStrength -= 1; //Reduce 1
}
msg += "1 lower case character, ";
}
//strong password
if (pStrength == password_settings.minLength && lowers > 0) {
msg = "Strong password!";
}
return msg + ';' + pStrength;
}
}
//default setting
var password_settings = {
minLength: 12,
maxLength: 25,
specialLength: 1,
upperLength: 1,
numberLength: 1,
barWidth: 200,
barColor: 'Red',
specialChars: '!@#$', //allowable special characters
metRequirement: false
};
//password strength plugin
$.fn.password_strength = function(options) {
//check if password met requirement
this.metReq = function() {
return password_settings.metRequirement;
}
//read password setting from xml file
$.ajax({
type: "GET",
url: "PasswordPolicy.xml", //use absolute link if possible
dataType: "xml",
success: function(xml) {
$(xml).find('Password').each(function() {
var _minLength = $(this).find('minLength').text(),
_maxLength = $(this).find('maxLength').text(),
_numsLength = $(this).find('numsLength').text(),
_upperLength = $(this).find('upperLength').text(),
_specialLength = $(this).find('specialLength').text(),
_barWidth = $(this).find('barWidth').text(),
_barColor = $(this).find('barColor').text(),
_specialChars = $(this).find('specialChars').text();
//set variables
password_settings.minLength = parseInt(_minLength);
password_settings.maxLength = parseInt(_maxLength);
password_settings.specialLength = parseInt(_specialLength);
password_settings.upperLength = parseInt(_upperLength);
password_settings.numberLength = parseInt(_numsLength);
password_settings.barWidth = parseInt(_barWidth);
password_settings.barColor = _barColor;
password_settings.specialChars = _specialChars;
});
}
});
return this.each(function() {
//bar position
var barLeftPos = $("[id$='" + this.id + "']").position().left + $("[id$='" + this.id + "']").width();
var barTopPos = $("[id$='" + this.id + "']").position().top + $("[id$='" + this.id + "']").height();
//password indicator text container
var container = $('')
.css({ position: 'absolute', top: barTopPos - 6, left: barLeftPos + 15, 'font-size': '75%', display: 'inline-block', width: password_settings.barWidth + 40 });
//add the container next to textbox
$(this).after(container);
//bar border and indicator div
var passIndi = $(' ')
.css({ position: 'absolute', display: 'none' })
.eq(0).css({ height: 3, top: barTopPos - 16, left: barLeftPos + 15, 'border-style': 'solid', 'border-width': 1, padding: 2 }).end()
.eq(1).css({ height: 5, top: barTopPos - 14, left: barLeftPos + 17 }).end()
//set max length of textbox
//$("[id$='" + this.id + "']").attr('maxLength', password_settings.maxLength);
//add the boder and div
container.before(passIndi);
$(this).keyup(function() {
var passwordVal = $(this).val(); //get textbox value
//set met requirement to false
password_settings.metRequirement = false;
if (passwordVal.length > 0) {
var msgNstrength = password_Strength.getStrengthInfo(passwordVal);
var msgNstrength_array = msgNstrength.split(";"), strengthPercent = 0,
barWidth = password_settings.barWidth;
//calculate the bar indicator length
if (msgNstrength_array.length > 1) {
strengthPercent = (msgNstrength_array[1] / password_settings.minLength) * barWidth;
}
$("[id$='PasswordStrengthBorder']").css({ display: 'inline', width: barWidth });
$("[id$='PasswordStrengthBar']").css({ display: 'inline', width: strengthPercent, 'background-color': password_settings.barColor });
//remove last "," character
if (msgNstrength_array[0].lastIndexOf(",") !== -1) {
container.text(msgNstrength_array[0].substring(0, msgNstrength_array[0].length - 2));
}
else {
container.text(msgNstrength_array[0]);
}
if (strengthPercent == barWidth) {
password_settings.metRequirement = true;
}
}
else {
container.text('');
$("[id$='PasswordStrengthBorder']").css("display", "none"); //hide
$("[id$='PasswordStrengthBar']").css("display", "none"); //hide
}
});
});
};
})(jQuery);
Include a Textbox control, jQuery library and the plug-in into the web page. Change the txtPassword id to your desire id. Use this line of code "var myPlugin = $("[id$='txtPassword']").password_strength();" to call the plug-in. To check if the password met the password policy, call the metReq() function with this line of code " myPlugin.metReq()". Please refer to Listing 2for full details. The jQuery $("[id$='txtPassword']") selector will work with ASP.NET server control, so don't bother using my 'txtPassword.ClientID'. The bar color, width and password policy information can be modified through the XML file. Listing 2 <div style="height:400px"><br />
<asp:label runat="server" id="lblPassword"
AssociatedControlId="txtPassword">Enter Password:</asp:label>
<asp:TextBox ID="txtPassword" runat="server"></asp:TextBox><br />
<a id="passwordPolicy" href="#">Password policy
<asp:Button ID="btnSubmit" runat="server" Text="Submit" />
<br /><br />
<asp:Label ID="ResultLabel" runat="server" Text=""></asp:Label>
</div>
<script src="Script/jquery-1.4.4.min.js" type="text/javascript"></script>
<script src="Script/jquery.password-strength.js" type="text/javascript"></script>
<script type="text/javascript">
$(document).ready(function() {
var myPlugin = $("[id$='txtPassword']").password_strength();
$("[id$='btnSubmit']").click(function() {
return myPlugin.metReq(); //return true or false
});
$("[id$='passwordPolicy']").click(function(event) {
var width = 350, height = 300, left = (screen.width / 2) - (width / 2),
top = (screen.height / 2) - (height / 2);
window.open("PasswordPolicy.xml", 'Password_poplicy', 'width=' + width + ',height=' + height + ',left=' + left + ',top=' + top);
event.preventDefault();
return false;
});
});
</script>
We can use the XLST to display the contents of the PasswordPolicy.xml or write code to extract its contents. I preferred to use XLST to avoid writing additional code. Displayed below is the password policy page. If you want to learn more on how to displaying XML with XSLT click on here.
Figure 2
 The regular expression that we are using is listed in listing 3. The numbers are adjustable and come from the XML file. Listing 3 (?=^.{12,25}$)(?=(?:.*?\d){2})(?=.*[a-z])(?=(?:.*?[A-Z]){2})(?=(?:.*?[!@#$%*()_+^&}{:;?.]){2})(?!.*\s)[0-9a-zA-Z!@#$%*()_+^&]*$
Shown in listing 4is the code to generate regular expression dynamically. So, tomorrow if your client told you to increase the required numeric in the password policy, you don't have to search or create a new regular expression. All you have to do is change the setting in the PasswordPolicy.xml file. You can verify the regular expression here. Listing 4 void btnSubmit_Click(object sender, EventArgs e)
{
PasswordSetting passwordSetting = Helper.GetPasswordSetting();
StringBuilder sbPasswordRegx = new StringBuilder(string.Empty);
//min and max
sbPasswordRegx.Append(@"(?=^.{" + passwordSetting.MinLength + "," + passwordSetting.MaxLength + "}$)");
//numbers length
sbPasswordRegx.Append(@"(?=(?:.*?\d){" + passwordSetting.NumsLength + "})");
//a-z characters
sbPasswordRegx.Append(@"(?=.*[a-z])");
//A-Z length
sbPasswordRegx.Append(@"(?=(?:.*?[A-Z]){" + passwordSetting.UpperLength + "})");
//special characters length
sbPasswordRegx.Append(@"(?=(?:.*?[" + passwordSetting.SpecialChars + "]){" + passwordSetting.SpecialLength + "})");
//(?!.*\s) - no spaces
//[0-9a-zA-Z!@#$%*()_+^&] -- valid characters
sbPasswordRegx.Append(@"(?!.*\s)[0-9a-zA-Z" + passwordSetting.SpecialChars + "]*$");
if (Regex.IsMatch(txtPassword.Text, sbPasswordRegx.ToString()))
{
ResultLabel.Text = "Password confront password policy!";
}
else
{
ResultLabel.Text = "Password does not confront password policy!";
}
}
Why the progress bar indicators look different from the one in the demo application?
Make sure that there is a proper DocType declare before the <html> tag. Click here to learn more about it.
Figure 4
How to change the TextBox to password mode?
For ASP.NET control, set the TextMode attribute to "Password".
For HTML control, set the type property to "Password".
Why I'm getting the error "This type of page is not served." when running the Classic ASP code on the local ASP.NET Development Server?
Deploy the demo application to the IIS Web Application Server.
Can I use this plug-in with other programming languages? Yes. I hope someone will find this information useful and make your programming job easier. If you find any bugs or disagree with the contents or want to help improve this article, please drop me a line and I'll work with you to correct it. I would suggest downloading the demo and explore it in order to grasp the full concept of it because I might miss some important information in this article. Please send me an email if you want to help improve this article. Dynamic Regular Expressions in Javascript
HTML <!DOCTYPE> Declaration
jQuery Password Indicator
Plugins/Authoring
Public functions from within a jQuery plug-in live Demo Download Source |