در ادامه بررسی تصویر امنیتی سایت مواردی که باید پیاده سازی شود برای مورد اول میتوان کلاس زیر را در نظر گرفت که متدهایی برای تولید اعداد بصورت تصادفی در بین بازه معرفی شده را بازگشت میدهد:
// RandomGenerator.cs
using System;
using System.Security.Cryptography;
namespace PersianCaptchaHandler
{
public class RandomGenerator
{
private static readonly byte[] Randb = new byte[4];
private static readonly RNGCryptoServiceProvider Rand = new RNGCryptoServiceProvider();
public static int Next()
{
Rand.GetBytes(Randb);
var value = BitConverter.ToInt32(Randb, 0);
if (value < 0) value = -value;
return value;
}
public static int Next(int max)
{
Rand.GetBytes(Randb);
var value = BitConverter.ToInt32(Randb, 0);
value = value%(max + 1);
if (value < 0) value = -value;
return value;
}
public static int Next(int min, int max)
{
var value = Next(max - min) + min;
return value;
}
}
}
// NumberToString.cs
namespace PersianCaptchaHandler
{
public class NumberToString
{
#region Fields
private static readonly string[] Yakan = new[] { "صفر", "یک", "دو", "سه", "چهار", "پنج", "شش", "هفت", "هشت", "نه" };
private static readonly string[] Dahgan = new[] { "", "", "بیست", "سی", "چهل", "پنجاه", "شصت", "هفتاد", "هشتاد", "نود" };
private static readonly string[] Dahyek = new [] { "ده", "یازده", "دوازده", "سیزده", "چهارده", "پانزده", "شانزده", "هفده", "هجده", "نوزده" };
private static readonly string[] Sadgan = new [] { "", "یکصد", "دوصد", "سیصد", "چهارصد", "پانصد", "ششصد", "هفتصد", "هشتصد", "نهصد" };
private static readonly string[] Basex = new [] { "", "هزار", "میلیون", "میلیارد", "تریلیون" };
#endregion
private static string Getnum3(int num3)
{
var s = "";
var d12 = num3 % 100;
var d3 = num3 / 100;
if (d3 != 0)
s = Sadgan[d3] + " و ";
if ((d12 >= 10) && (d12 <= 19))
{
s = s + Dahyek[d12 - 10];
}
else
{
var d2 = d12 / 10;
if (d2 != 0)
s = s + Dahgan[d2] + " و ";
var d1 = d12 % 10;
if (d1 != 0)
s = s + Yakan[d1] + " و ";
s = s.Substring(0, s.Length - 3);
}
return s;
}
public static string ConvertIntNumberToFarsiAlphabatic(string snum)
{
var stotal = "";
if (snum == "0") return Yakan[0];
snum = snum.PadLeft(((snum.Length - 1) / 3 + 1) * 3, '0');
var l = snum.Length / 3 - 1;
for (var i = 0; i <= l; i++)
{
var b = int.Parse(snum.Substring(i * 3, 3));
if (b != 0)
stotal = stotal + Getnum3(b) + " " + Basex[l - i] + " و ";
}
stotal = stotal.Substring(0, stotal.Length - 3);
return stotal;
}
}
}
using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
namespace PersianCaptchaHandler
{
public class Encryptor
{
#region constraints
private static string Password { get { return "Mehdi"; } }
private static string Salt { get { return "Payervand"; } }
#endregion
public static string Encrypt(string clearText)
{
// Turn text to bytes
var clearBytes = Encoding.Unicode.GetBytes(clearText);
var pdb = new PasswordDeriveBytes(Password, Encoding.Unicode.GetBytes(Salt));
var ms = new MemoryStream();
var alg = Rijndael.Create();
alg.Key = pdb.GetBytes(32);
alg.IV = pdb.GetBytes(16);
var cs = new CryptoStream(ms, alg.CreateEncryptor(), CryptoStreamMode.Write);
cs.Write(clearBytes, 0, clearBytes.Length);
cs.Close();
var encryptedData = ms.ToArray();
return Convert.ToBase64String(encryptedData);
}
public static string Decrypt(string cipherText)
{
// Convert text to byte
var cipherBytes = Convert.FromBase64String(cipherText);
var pdb = new PasswordDeriveBytes(Password, Encoding.Unicode.GetBytes(Salt));
var ms = new MemoryStream();
var alg = Rijndael.Create();
alg.Key = pdb.GetBytes(32);
alg.IV = pdb.GetBytes(16);
var cs = new CryptoStream(ms, alg.CreateDecryptor(), CryptoStreamMode.Write);
cs.Write(cipherBytes, 0, cipherBytes.Length);
cs.Close();
var decryptedData = ms.ToArray();
return Encoding.Unicode.GetString(decryptedData);
}
}
}
و نیز برای اعتبار سنجی عدد دریافتی از کاربر میتوان از عبارت با قاعده زیر استفاده کرد:
// Utils.cs
using System.Text.RegularExpressions;
namespace PersianCaptchaHandler
{
public class Utils
{
private static readonly Regex NumberMatch = new Regex(@"^([0-9]*|\d*\.\d{1}?\d*)$", RegexOptions.Compiled);
public static bool IsNumber(string number2Match)
{
return NumberMatch.IsMatch(number2Match);
}
}
}
<add verb="GET" path="/captcha/" type="PersianCaptchaHandler.CaptchaHandler, PersianCaptchaHandler, Version=1.0.0.0, Culture=neutral" />
<!-- ASPX -->
<dl>
<dt>تصویر امنیتی</dt>
<dd>
<asp:Image ID="imgCaptchaText" runat="server" AlternateText="CaptchaImage" />
<asp:HiddenField ID="hfCaptchaText" runat="server" />
<asp:ImageButton ID="btnRefreshCaptcha" runat="server" ImageUrl="/img/refresh.png"
OnClick="btnRefreshCaptcha_Click" />
<br />
<asp:TextBox ID="txtCaptcha" runat="server" AutoCompleteType="Disabled"></asp:TextBox>
</dd>
<dd>
<asp:Button ID="btnSubmit" runat="server" Text="ثبت" OnClick="btnSubmit_Click" />
</dd>
</dl>
<asp:Label ID="lblMessage" runat="server"></asp:Label>
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
SetCaptcha();
}
private void SetCaptcha()
{
lblMessage.Text =
txtCaptcha.Text = string.Empty;
var newNumber =
RandomGenerator.Next(100, 999)
;
var farsiAlphabatic = NumberToString.ConvertIntNumberToFarsiAlphabatic(newNumber.ToString());
hfCaptchaText.Value =
HttpUtility
.UrlEncode(
Encryptor.Encrypt(
farsiAlphabatic
)
);
txtCaptcha.Text = string.Empty;
imgCaptchaText.ImageUrl =
"/captcha/?text=" + hfCaptchaText.Value;
}
private string GetCaptcha()
{
var farsiAlphabatic = NumberToString.ConvertIntNumberToFarsiAlphabatic(txtCaptcha.Text);
var encryptedString =
HttpUtility
.UrlEncode(
Encryptor.Encrypt(
farsiAlphabatic
)
);
return encryptedString;
}
private bool ValidateUserInputForLogin()
{
if (!Utils.IsNumber(txtCaptcha.Text))
{
lblMessage.Text = "تصویر امنیتی را بطور صحیح وارد نکرده اید";
return false;
}
var strGetCaptcha =
GetCaptcha();
var strDecodedVAlue =
hfCaptchaText.Value;
if (strDecodedVAlue != strGetCaptcha)
{
lblMessage.Text = "کلمه امنیتی اشتباه است";
SetCaptcha();
return false;
}
return true;
}
protected void btnSubmit_Click(object sender, EventArgs e)
{
if (!ValidateUserInputForLogin()) return;
lblMessage.Text = "کلمه امنیتی درست است";
}
protected void btnRefreshCaptcha_Click(object sender, ImageClickEventArgs e)
{
SetCaptcha();
}
