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Tuesday, September 21, 2010

ASP.NET Security Vulnerability: Take Action Immediately

This is very important for those who have application running out there. Attacker can get data encrypted data in view state or web.config data if you ignore this.

Detail informations and workaround stated in Scottgu's Blog

For more others information, please refer to

Monday, September 20, 2010

Keep track download in ASP.NET

I have a software in my web server and let visitor download for free, i wish to keep track of total download and visitor location. 

For the location keep tracking, i use GeoIP (GeoLiteCity.dat) 


I have create a table called downloadlog with field below. I plan to have different type of product in future, so i add ProductFamilyID field. If you don't have that, you can ignore it.

Now, i need a stored procedure called psp_DownloadLog_Add that insert data into table above. The code should be as simple as possible

CREATE PROCEDURE [dbo].[psp_DownloadLog_Add]
@p_Country NVARCHAR(255),
@p_CountryCode VARCHAR(50),
@p_City NVARCHAR(255),
@p_ReferrerURL        NVARCHAR(512),
@p_ProductFamilyID INT

INSERT INTO tblDownloadLog




To make the system more structural and manageable, I have create 2 classes to handle the download log. DownloadLogInfo class mainly is use the deal with the information that need to log into database. DownloadLog class is mainly the class who do the communication with the database. Please check the code below.

DownloadLogInfo class

 public sealed class DownloadLogInfo
         public DownloadLogInfo() { }
         int _downloadID = 0;
         string _ip = "";
         string _country = "";
         string _countryCode = "";
         string _city = "";
         int _productFamilyID = 0;
         string _referrerURL = "";
         DateTime _downloadDate = DateTime.Now;

         public int DownloadID { get { return _downloadID; } set { _downloadID = value; } }
         public string IP { get { return _ip; } set { _ip = value; } }
         public string Country { get { return _country; } set { _country = value; } }
         public string CountryCode { get { return _countryCode; } set { _countryCode = value; } }
         public string City { get { return _city; } set { _city = value; } }
         public int ProductFamilyID { get { return _productFamilyID; } set { _productFamilyID = value; } }
         public string ReferrerURL { get { return _referrerURL; } set { _referrerURL = value; } }
         public DateTime DownloadDate { get { return _downloadDate; } set { _downloadDate = value; } }

         public DownloadLogInfo(int pDownloadID, string pIP, string pCountry, string pCountryCode, string pCity, int pProductFamilyID, string pReferrerURL, DateTime pDownloadDate)
             _downloadID = pDownloadID;
             _ip = pIP;
             _country = pCountry;
             _countryCode = pCountryCode;
             _city = pCity;
             _productFamilyID = pProductFamilyID;
             _referrerURL = pReferrerURL;
             _downloadDate = pDownloadDate;



DownloadLog Class

    public sealed class DownloadLog
        public void Add(DownloadLogInfo pInfo, string pConnectionString)
            SpParamInfo[] myParamInfo = new SpParamInfo[6];
            myParamInfo[0] = new SpParamInfo("@p_IP", SqlDbType.NVarChar, pInfo.IP);
            myParamInfo[1] = new SpParamInfo("@p_Country", SqlDbType.NVarChar, pInfo.Country);
            myParamInfo[2] = new SpParamInfo("@p_CountryCode", SqlDbType.NVarChar, pInfo.CountryCode);
            myParamInfo[3] = new SpParamInfo("@p_City", SqlDbType.NVarChar, pInfo.City);
            myParamInfo[4] = new SpParamInfo("@p_ProductFamilyID", SqlDbType.Int, pInfo.ProductFamilyID);
            myParamInfo[5] = new SpParamInfo("@p_ReferrerURL", SqlDbType.NVarChar, pInfo.ReferrerURL);

            DbAdapter myDbAdapter = new DbAdapter(pConnectionString);
            myDbAdapter.ExecuteNonQuery("psp_DownloadLog_Add", myParamInfo);




Now, I have create a page, call download.aspx. This page will actually get information from the visitor and insert into database. After that it will force a file to be downloaded. Before that, i already GeoLiteCity.dat file and put into my App_Data folder.

Code behind for download.aspx

protected void Page_Load(object sender, EventArgs e)
        string VisitorReferrer;

        // Full path to GeoLiteCity.dat file
        string FullDBPath = Server.MapPath("~/App_Data/GeoLiteCity.dat");
        // Visitor's IP address
        string VisitorIP; 
        VisitorIP  = Request.ServerVariables["REMOTE_ADDR"];
        if (Request.UrlReferrer != null)
            VisitorReferrer = Request.UrlReferrer.ToString();
            VisitorReferrer = "";

        // Create objects needed for geo targeting
        Geotargeting.LookupService ls = new Geotargeting.LookupService(FullDBPath, Geotargeting.LookupService.GEOIP_STANDARD);
        Geotargeting.Location visitorLocation = ls.getLocation(VisitorIP);
        DownloadLog myDownloadLog = new DownloadLog();
        DownloadLogInfo myDownloadLogInfo = new DownloadLogInfo();

        if (visitorLocation != null) // get the geoip information using visitor IP address
            myDownloadLogInfo.Country = visitorLocation.countryName;
            myDownloadLogInfo.CountryCode = visitorLocation.countryCode;
            myDownloadLogInfo.City = "unknown";
            if ( != null)
                myDownloadLogInfo.City =;
            myDownloadLogInfo.IP = VisitorIP;
            myDownloadLogInfo.ProductFamilyID = 1;
            myDownloadLogInfo.ReferrerURL = VisitorReferrer;
            string country = "unknown";
            string countryCode = "unknown";
            string city = "unknown";
            myDownloadLogInfo.Country = country;
            myDownloadLogInfo.CountryCode = countryCode;
            myDownloadLogInfo.City = city;
            myDownloadLogInfo.IP = VisitorIP;
            myDownloadLogInfo.ProductFamilyID = 1;
            myDownloadLogInfo.ReferrerURL = VisitorReferrer;

       // WebConfig.Connection is the connection the database and insert data into database
       myDownloadLog.Add(myDownloadLogInfo, WebConfig.Connection);
       Response.ContentType = "application/zip";
       Response.AddHeader("content-disposition", "attachment;");

       FileStream sourceFile = new FileStream(@"C:\inetpub\dotnetfish\software\", FileMode.Open);
       long FileSize;
       FileSize = sourceFile.Length;
       byte[] getContent = new byte[(int)FileSize];
       sourceFile.Read(getContent, 0, (int)sourceFile.Length);


Tuesday, September 14, 2010

Cannot Delete xxx: Access is denied Make sure the disk is not full or write-protected and that the file is not currently in use

Have you come across the annoying error when try to delete files from you computer or even external harddisk? 
I've tried to change the permission setting in security tab but i cannot do anything because only system can change the setting. 

Finally, i found a tool named unlocker that help me to delete the files.

Hope this help.

Attempted to read or write protected memory. This is often an indication that other memory has been corrupted.

Hit below error when deploy a new app to existing running application.

Attempted to read or write protected memory. This is often an indication that other memory has been corrupted. 
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory has been corrupted. 

Source Error: 

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Try to set the folder permission but still hit the same error after restart iis. 

Next, i try to run the permissions wizard in the IIS. After run it, restart iis and i'm lucky. It work like normal.

Hope this help.