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• Diffie-Hellman in Silverlight

  - by cmaduro

  I am trying to devise a security scheme for encrypting the application level data between a silverlight client, and a php webservice that I created. Since I am dealing with a public website the information I am pulling from the service is public, but the information I'm submitting to the webservice is not public. There is also a back end to the website for administration, so naturally all application data being pushed and pulled from the webservice to the silverlight administration back end must also be encrypted. Silverlight does not support asymmetric encryption, which would work for the public website. Symmetric encryption would only work on the back end because users do not log in to the public website, so no password based keys could be derived. Still symmetric encryption would be great, but I cannot securely save the private key in the silverlight client. Because it would either have to be hardcoded or read from some kind of config file. None of that is considered secure. So... plan B. My final alternative would be then to implement the Diffie-Hellman algorithm, which supports symmetric encryption by means of key agreement. However Diffie-Hellman is vulnerable to man-in-the-middle attacks. In other words, there is no guarantee that either side is sure of each others identity, making it possible for communication to be intercepted and altered without the receiving party knowing about it. It is thus recommended to use a private shared key to encrypt the key agreement handshaking, so that the identity of either party is confirmed. This brings me back to my initial problem that resulted in me needing to use Diffie-Hellman, how can I use a private key in a silverlight client without hardcoding it either in the code or an xml file. I'm all out of love on this one... is there any answer to this?

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• User roles - why not store in session?

  - by Phil

  I'm porting an ASP.NET application to MVC and need to store two items relating to an authenitcated user: a list of roles and a list of visible item IDs, to determine what the user can or cannot see. We've used WSE with a web service in the past and this made things unbelievably complex and impossible to debug properly. Now we're ditching the web service I was looking foward to drastically simplifying the solution simply to store these things in the session. A colleague suggested using the roles and membership providers but on looking into this I've found a number of problems: a) It suffers from similar but different problems to WSE in that it has to be used in a very constrained way maing it tricky even to write tests; b) The only caching option for the RolesProvider is based on cookies which we've rejected on security grounds; c) It introduces no end of complications and extra unwanted baggage; All we want to do, in a nutshell, is store two string variables in a user's session or something equivalent in a secure way and refer to them when we need to. What seems to be a ten minute job has so far taken several days of investigation and to compound the problem we have now discovered that session IDs can apparently be faked, see http://blogs.sans.org/appsecstreetfighter/2009/06/14/session-attacks-and-aspnet-part-1/ I'm left thinking there is no easy way to do this very simple job, but I find that impossible to believe. Could anyone: a) provide simple information on how to make ASP.NET MVC sessions secure as I always believed they were? b) suggest another simple way to store these two string variables for a logged in user's roles etc. without having to replace one complex nightmare with another as described above? Thank you.

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• How to detect hidden field tampering?

  - by Myron

  On a form of my web app, I've got a hidden field that I need to protect from tampering for security reasons. I'm trying to come up with a solution whereby I can detect if the value of the hidden field has been changed, and react appropriately (i.e. with a generic "Something went wrong, please try again" error message). The solution should be secure enough that brute force attacks are infeasible. I've got a basic solution that I think will work, but I'm not security expert and I may be totally missing something here. My idea is to render two hidden inputs: one named "important_value", containing the value I need to protect, and one named "important_value_hash" containing the SHA hash of the important value concatenated with a constant long random string (i.e. the same string will be used every time). When the form is submitted, the server will re-compute the SHA hash, and compare against the submitted value of important_value_hash. If they are not the same, the important_value has been tampered with. I could also concatenate additional values with the SHA's input string (maybe the user's IP address?), but I don't know if that really gains me anything. Will this be secure? Anyone have any insight into how it might be broken, and what could/should be done to improve it? Thanks!

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• session regeneration in tomcat ?

  - by shrini1000

  Hi, I am using Spring security to secure my Java web application which is deployed in tomcat. I found out that it is vulnerable to session fixation attacks because tomcat does not create a new session upon successful log in. On debugging some more, here's what I found. For the following code (which is supposed to create a new session - pl. note, it's just a snippet and not full code): HttpSession session = request.getSession(false); session.invalidate(); session = request.getSession(true); // we now have a new session I thought a new session will be created, but tomcat simply uses the same session that got invalidated and hence the session id does not change. I searched online and found a solution which uses a 'valve' - http://marvinsmutterings.blogspot.com/2010/02/fixing-session-fixation-in-liferay-on.html but could not get it to work because it's looking for a jboss logging class and when I add it to lib, I get a reflection exception and the server doesn't start up. I'm using tomcat 5.5.28. Will be glad to have any pointers. Pl. let me know if you need more details, since I don't want to make this post too long. Sincere thanks!

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• GET params in ruby-on-rails project - best practices?

  - by Lynn C

  I've inherited a little rails app and I need to extend it slightly. It's actually quite simple, but I want to make sure I'm doing it the right way... If I visit myapp:3000/api/persons it gives me a full list of people in XML format. I want to pass param in the URL so that I can return users that match the login or the email e.g. yapp:3000/api/persons?login=jsmith would give me the person with the corresponding login. Here's the code: def index if params.size > 2 # We have 'action' & 'controller' by default if params['login'] @person = [Person.find(:first, :conditions => { :login => params['login'] })] elsif params['email'] @persons = [Person.find(:first, :conditions => { :email => params['email'] })] end else @persons = Person.find(:all) end end Two questions... Is it safe? Does ActiveRecord protect me from SQL injection attacks (notice I'm trusting the params that are coming in)? Is this the best way to do it, or is there some automagical rails feature I'm not familiar with?

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• Using MD5 to generate an encryption key from password?

  - by Charles

  I'm writing a simple program for file encryption. Mostly as an academic exercise but possibly for future serious use. All of the heavy lifting is done with third-party libraries, but putting the pieces together in a secure manner is still quite a challenge for the non-cryptographer. Basically, I've got just about everything working the way I think it should. I'm using 128-bit AES for the encryption with a 128-bit key length. I want users to be able to enter in variable-length passwords, so I decided to hash the password with MD5 and then use the hash as the key. I figured this was acceptable--the key is always supposed to be a secret, so there's no reason to worry about collision attacks. Now that I've implemented this, I ran across a couple articles indicating that this is a bad idea. My question is: why? If a good password is chosen, the cipher is supposed to be strong enough on its own to never reveal the key except via an extraordinary (read: currently infeasible) brute-force effort, right? Should I be using something like PBKDF2 to generate the key or is that just overkill for all but the most extreme cryptographic applications?

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• When *not* to use prepared statements?

  - by Ben Blank

  I'm re-engineering a PHP-driven web site which uses a minimal database. The original version used "pseudo-prepared-statements" (PHP functions which did quoting and parameter replacement) to prevent injection attacks and to separate database logic from page logic. It seemed natural to replace these ad-hoc functions with an object which uses PDO and real prepared statements, but after doing my reading on them, I'm not so sure. PDO still seems like a great idea, but one of the primary selling points of prepared statements is being able to reuse them… which I never will. Here's my setup: The statements are all trivially simple. Most are in the form SELECT foo,bar FROM baz WHERE quux = ? ORDER BY bar LIMIT 1. The most complex statement in the lot is simply three such selects joined together with UNION ALLs. Each page hit executes at most one statement and executes it only once. I'm in a hosted environment and therefore leery of slamming their servers by doing any "stress tests" personally. Given that using prepared statements will, at minimum, double the number of database round-trips I'm making, am I better off avoiding them? Can I use PDO::MYSQL_ATTR_DIRECT_QUERY to avoid the overhead of multiple database trips while retaining the benefit of parametrization and injection defense? Or do the binary calls used by the prepared statement API perform well enough compared to executing non-prepared queries that I shouldn't worry about it? EDIT: Thanks for all the good advice, folks. This is one where I wish I could mark more than one answer as "accepted" — lots of different perspectives. Ultimately, though, I have to give rick his due… without his answer I would have blissfully gone off and done the completely Wrong Thing even after following everyone's advice. :-) Emulated prepared statements it is!

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• Understanding CSRF - Simple Question

  - by byronh

  I know this might make me seem like an idiot, I've read everything there is to read about CSRF and I still don't understand how using a 'challenge token' would add any sort of prevention. Please help me clarify the basic concept, none of the articles and posts here on SO I read seemed to really explicitly state what value you're comparing with what. From OWASP: In general, developers need only generate this token once for the current session. After initial generation of this token, the value is stored in the session and is utilized for each subsequent request until the session expires. If I understand the process correctly, this is what happens. I log in at http://example.com and a session/cookie is created containing this random token. Then, every form includes a hidden input also containing this random value from the session which is compared with the session/cookie upon form submission. But what does that accomplish? Aren't you just taking session data, putting it in the page, and then comparing it with the exact same session data? Seems like circular reasoning. These articles keep talking about following the "same-origin policy" but that makes no sense, because all CSRF attacks ARE of the same origin as the user, just tricking the user into doing actions he/she didn't intend. Is there any alternative other than appending the token to every single URL as a query string? Seems very ugly and impractical, and makes bookmarking harder for the user.

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• Simulating O_NOFOLLOW (2): Is this other approach safe?

  - by Daniel Trebbien

  As a follow-up question to this one, I thought of another approach which builds off of @caf's answer for the case where I want to append to file name and create it if it does not exist. Here is what I came up with: Create a temporary directory with mode 0700 in a system temporary directory on the same filesystem as file name. Create an empty, temporary, regular file (temp_name) in the temporary directory (only serves as placeholder). Open file name for reading only, just to create it if it does not exist. The OS may follow name if it is a symbolic link; I don't care at this point. Make a hard link to name at temp_name (overwriting the placeholder file). If the link call fails, then exit. (Maybe someone has come along and removed the file at name, who knows?) Use lstat on temp_name (now a hard link). If S_ISLNK(lst.st_mode), then exit. open temp_name for writing, append (O_WRONLY | O_APPEND). Write everything out. Close the file descriptor. unlink the hard link. Remove the temporary directory. (All of this, by the way, is for an open source project that I am working on. You can view the source of my implementation of this approach here.) Is this procedure safe against symbolic link attacks? For example, is it possible for a malicious process to ensure that the inode for name represents a regular file for the duration of the lstat check, then make the inode a symbolic link with the temp_name hard link now pointing to the new, symbolic link? I am assuming that a malicious process cannot affect temp_name.

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• ASP.NET webservice API security.

  - by Tejaswi Yerukalapudi

  Hi, I have an iPhone app accessing an ASP.NET Webservice for data. Since I'm building both the ASP.NET end and the iPhone part of the app, and we'll shortly be publishing it in the Appstore, I'd like to know what security checks I need to make. The basic flow of the program (without divulging too much info about it) is as follows - . Login (Enter Username, pass on the app) . Primary screen where the data is loaded from a webservice and presented . And post data back after a few updates by the user I'm using POST to send the data to the Webservice via HTTPS. I'm sanitizing the inputs, checking for length of the inputs, but that's the limit of my knowledge as far as security goes. Any other tips are greatly appreciated! Edit: I should probably add that our service needs to be subscribed to separately and the iPhone component of it cannot be used alone. So the average user will not have login credentials. And the app itself has healthcare data in it, so I'd rather not have anyone trying attacks from my login page. Thanks, Teja.

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• Help, my CentOS servers keep going down , No route to host after a random uptime [closed]

  - by user249071

  Hello , I have a couple of Centos linux servers, that have a very simple task, they run nginx + fastcgi for php , and some NFS mounts between them, readonly They have some RPC commands to start some downloading processes with wget, nothing fancy , from a main server, but their behavior is very unstable, they simply go down, we tried to monitor ram , processor usage, even network connections, they don't load up so much, max network connections up to... 250 max, 15% processor usage and memory , well, doesn't even fill up, 2.5GB from 8GB max , I have no ideea why can a linux server go down like that, they aren't even public servers, no domain names installed no public serving, for sites. The only thing that I've discovered was that if i didn't restart the network service every couple of hours or so... the servers were becoming very slow, starting apps very slow, but not repoting a high usage of resources...Maybe Centos doesn't free the timeout connections, or something like that...It's based on Red Hat right? I'm not a linux expert , but I'm sure that there are a few guys out there that can easily have an answer to this , or even have some leads to what i can do ... I haven't installed snort, or other things to view if we have some DOS attacks, still the scheduled script that restarts the network each hour should put the system back online, and it doesn't.... Thank you in advance

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• HTTP: can GET and POST requests from a same machine come from different IPs?

  - by NoozNooz42

  I'm pretty sure I remember reading --but cannot find back the links anymore-- about this: on some ISP (including at least one big ISP in the U.S.) it is possible to have a user's GET and POST request appearing to come from different IPs. (note that this is totally programming related, and I'll give an example below) I'm not talking about having your IP adress dynamically change between two requests. I'm talking about this: IP 1: 123.45.67.89 IP 2: 101.22.33.44 The same user makes a GET, then a POST, then a GET again, then a POST again and the servers see this: - GET from IP 1 - POST from IP 2 - GET from IP 1 - POST from IP 2 So altough it's the same user, the webserver sees different IPs for the GET and the POSTs. Surely seen that HTTP is a stateless protocol this is perfectly legit right? I'd like to find back the explanation as to how/why certain ISP have their networks configured such that this may happen. I'm asking because someone asked me to implement the following IP filter and I'm pretty sure it is fundamentally broken code (breaking havoc for at least one major american ISP users). Here's a Java servlet filter that is supposed to protect against some attacks. The reasoning is that: "For any session filter checks that IP address in the request is the same that was used when session was created. So in this case session ID could not be stolen for forming fake sessions." http://www.servletsuite.com/servlets/protectsessionsflt.htm However I'm pretty sure this is inherently broken because there are ISPs where you may see GET and POST coming from different IPs. Any info on this subject is very welcome.

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• Is this a good job description? What title would you give this position?

  - by Zack Peterson

  Department: Information Technology Reports To: Chief Information Officer Purpose: Company's ________________ is specifically engaged in the development of World Wide Web applications and distributed network applications. This person is concerned with all facets of the software development process and specializes in software product management. He or she contributes to projects in an application architect role and also performs individual programming tasks. Essential Duties & Responsibilities: This person is involved in all aspects of the software development process such as: Participation in software product definitions, including requirements analysis and specification Development and refinement of simulations or prototypes to confirm requirements Feasibility and cost-benefit analysis, including the choice of architecture and framework Application and database design Implementation (e.g. installation, configuration, customization, integration, data migration) Authoring of documentation needed by users and partners Testing, including defining/supporting acceptance testing and gathering feedback from pre-release testers Participation in software release and post-release activities, including support for product launch evangelism (e.g. developing demonstrations and/or samples) and subsequent product build/release cycles Maintenance Qualifications: Bachelor's degree in computer science or software engineering Several years of professional programming experience Proficiency in the general technology of the World Wide Web: Hypertext Transfer Protocol (HTTP) Hypertext Markup Language (HTML) JavaScript Cascading Style Sheets (CSS) Proficiency in the following principles, practices, and techniques: Accessibility Interoperability Usability Security (especially prevention of SQL injection and cross-site scripting (XSS) attacks) Object-oriented programming (e.g. encapsulation, inheritance, modularity, polymorphism, etc.) Relational database design (e.g. normalization, orthogonality) Search engine optimization (SEO) Asynchronous JavaScript and XML (AJAX) Proficiency in the following specific technologies utilized by Company: C# or Visual Basic .NET ADO.NET (including ADO.NET Entity Framework) ASP.NET (including ASP.NET MVC Framework) Windows Presentation Foundation (WPF) Language Integrated Query (LINQ) Extensible Application Markup Language (XAML) jQuery Transact-SQL (T-SQL) Microsoft Visual Studio Microsoft Internet Information Services (IIS) Microsoft SQL Server Adobe Photoshop

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• Is a GWT app running on Google App Engine protected from CSRF

  - by gerdemb

  I'm developing a GWT app running on the Google App Engine and wondering if I need to worry about Cross-site request forgery or is that automatically taken care of for me? For every RPC request that requires authentication, I have the following code: public class BookServiceImpl extends RemoteServiceServlet implements BookService { public void deleteInventory(Key<Inventory> inventoryKey) throws NotLoggedInException, InvalidStateException, NotFoundException { DAO dao = new DAO(); // This will throw NotLoggedInException if user is not logged in User user = dao.getCurrentUser(); // Do deletion here } } public final class DAO extends DAOBase { public User getCurrentUser() throws NotLoggedInException { currentUser = UserServiceFactory.getUserService().getCurrentUser(); if(currentUser == null) { throw new NotLoggedInException(); } return currentUser; } I couldn't find any documentation on how the UserService checks authentication. Is it enough to rely on the code above or do I need to to more? I'm a beginner at this, but from what I understand to avoid CSRF attacks some of the strategies are: adding an authentication token in the request payload instead of just checking a cookie checking the HTTP Referer header I can see that I have cookies set from Google with what look like SID values, but I can't tell from the serialized Java objects in the payloads if tokens are being passed or not. I also don't know if the Referer header is being used or not. So, am I worrying about a non-issue? If not, what is the best strategy here? This is a common enough problem, that there must be standard solutions out there...

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• ASP.Net MVC, JS injection and System.ArgumentException - Illegal Characters in path

  - by Mose

  Hi, In my ASP.Net MVC application, I use custom error handling. I want to perform custom actions for each error case I meet in my application. So I override Application_Error, get the Server.GetLastError(); and do my business depending on the exception, the current user, the current URL (the application runs on many domains), the user IP, and many others. Obviousely, the application is often the target of hackers. In almost all the case it's not a problem to detect and manage it, but for some JS URL attacks, my error handling does not perform what I want it to do. Ex (from logs) : http://localhost:1809/Scripts/]||!o.support.htmlSerialize&&[1 When I got such an URL, an exception is raised when accessing the ConnectionStrings section in the web.config, and I can't even redirect to another URL. It leads to a "System.ArgumentException - Illegal Characters in path, etc." The screenshot below shows the problem : http://screencast.com/t/Y2I1YWU4 An obvious solution is to write a HTTP module to filter the urls before they reach my application, but I'd like to avoid it because : I like having the whole security being managed in one place (in the Application_Error() method) In the module I cannot access the whole data I have in the application itself (application specific data I don't want to debate here) Questions : Did you meet this problem ? How did you manage it ? Thanks for you suggestions, Mose

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• wmd editor, why does it keep showing html instead of just going straight to markup

  - by Ke

  hi, im wondering how wmd is supposed to work, when i type in the textarea the text doesnt have html, but once the text is stored in db it turns to html. wmd also shows all this html when reloading the content? is it supposed to work like this? Do I have to sanitize the text before its put into the db? if so how? I thought wmd doesnt deal with html? except in code blocks. Also there are p tags being added Using the beneath html it gets added directly. I guess this could cause xss attacks? - (1) <a onmouseover="alert(1)" href="#">read this!</a> - (2) <p <script>alert(1)</script>hello - (3) </td <script>alert(1)</script>hello I wonder how is wmd supposed to work? I thought it was supposed to enter everything in its own mark up, store its on mark up and retrieve it etc. instead of storing plain html Chees Ke

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• Would an immutable keyword in Java be a good idea?

  - by berry120

  Generally speaking, the more I use immutable objects in Java the more I'm thinking they're a great idea. They've got lots of advantages from automatically being thread-safe to not needing to worry about cloning or copy constructors. This has got me thinking, would an "immutable" keyword go amiss? Obviously there's the disadvantages with adding another reserved word to the language, and I doubt it will actually happen primarily for the above reason - but ignoring that I can't really see many disadvantages. At present great care has to be taken to make sure objects are immutable, and even then a dodgy javadoc comment claiming a component object is immutable when it's in fact not can wreck the whole thing. There's also the argument that even basic objects like string aren't truly immutable because they're easily vunerable to reflection attacks. If we had an immutable keyword the compiler could surely recursively check and give an iron clad guarantee that all instances of a class were immutable, something that can't presently be done. Especially with concurrency becoming more and more used, I personally think it'd be good to add a keyword to this effect. But are there any disadvantages or implementation details I'm missing that makes this a bad idea?

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• What characters are NOT escaped with a mysqli prepared statement?

  - by barfoon

  Hey everyone, I'm trying to harden some of my PHP code and use mysqli prepared statements to better validate user input and prevent injection attacks. I switched away from mysqli_real_escape_string as it does not escape % and _. However, when I create my query as a mysqli prepared statement, the same flaw is still present. The query pulls a users salt value based on their username. I'd do something similar for passwords and other lookups. Code: $db = new sitedatalayer(); if ($stmt = $db->_conn->prepare("SELECT `salt` FROM admins WHERE `username` LIKE ? LIMIT 1")) { $stmt->bind_param('s', $username); $stmt->execute(); $stmt->bind_result($salt); while ($stmt->fetch()) { printf("%s\n", $salt); } $stmt->close(); } else return false; Am I composing the statement correctly? If I am what other characters need to be examined? What other flaws are there? What is best practice for doing these types of selects? Thanks,

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• PHP -- automatic SQL injection protection?

  - by ashgromnies

  I took over maintenance of a PHP app recently and I'm not super familiar with PHP but some of the things I've been seeing on the site are making me nervous that it could be vulnerable to a SQL injection attack. For example, see how this code for logging into the administrative section works: $password = md5(HASH_SALT . $_POST['loginPass']); $query = "SELECT * FROM `administrators` WHERE `active`='1' AND `email`='{$_POST['loginEmail']}' AND `password`='{$password}'"; $userInfo = db_fetch_array(db_query($query)); if($userInfo['id']) { $_SESSION['adminLoggedIn'] = true; // user is logged in, other junk happens here, not important The creators of the site made a special db_query method and db_fetch_array method, shown here: function db_query($qstring,$print=0) { return @mysql(DB_NAME,$qstring); } function db_fetch_array($qhandle) { return @mysql_fetch_array($qhandle); } Now, this makes me think I should be able to do some sort of SQL injection attack with an email address like: ' OR 'x'='x' LIMIT 1; and some random password. When I use that on the command line, I get an administrative user back, but when I try it in the application, I get an invalid username/password error, like I should. Could there be some sort of global PHP configuration they have enabled to block these attacks? Where would that be configured? Here is the PHP --version information: # php --version PHP 5.2.12 (cli) (built: Feb 28 2010 15:59:21) Copyright (c) 1997-2009 The PHP Group Zend Engine v2.2.0, Copyright (c) 1998-2009 Zend Technologies with the ionCube PHP Loader v3.3.14, Copyright (c) 2002-2010, by ionCube Ltd., and with Zend Optimizer v3.3.9, Copyright (c) 1998-2009, by Zend Technologies

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• Best practices for encrypting continuous/small UDP data

  - by temp

  Hello everyone, I am having an application where I have to send several small data per second through the network using UDP. The application need to send the data in real-time (no waiting). I want to encrypt these data and insure that what I am doing is as secure as possible. Since I am using UDP, there is no way to use SSL/TLS, so I have to encrypt each packet alone since the protocol is connectionless/unreliable/unregulated. Right now, I am using a 128-bit key derived from a passphrase from the user, and AES in CBC mode (PBE using AES-CBC). I decided to use a random salt with the passphrase to derive the 128-bit key (prevent dictionary attack on the passphrase), and of course use IVs (to prevent statistical analysis for packets). However I am concerned about few things: Each packet contains small amount of data (like a couple of integer values per packet) which will make the encrypted packets vulnerable to known-plaintext attacks (which will result in making it easier to crack the key). Also, since the encryption key is derived from a passphrase, this will make the key space way less (I know the salt will help, but I have to send the salt through the network once and anyone can get it). Given these two things, anyone can sniff and store the sent data, and try to crack the key. Although this process might take some time, once the key is cracked all the stored data will be decrypted, which will be a real problem for my application. So my question is, what is the best practices for sending/encrypting continuous small data using a connectionless protocol (UDP)? Is my way the best way to do it? ...flowed? ...Overkill? ... Please note that I am not asking for a 100% secure solution, as there is no such thing. Cheers

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• Best practices for encrytping continuous/small UDP data

  - by temp

  Hello everyone, I am having an application where I have to send several small data per second through the network using UDP. The application need to send the data in real-time (on waiting). I want to encrypt these data and insure that what I am doing is as secure as possible. Since I am using UDP, there is no way to use SSL/TLS, so I have to encrypt each packet alone since the protocol is connectionless/unreliable/unregulated. Right now, I am using a 128-bit key derived from a passphrase from the user, and AES in CBC mode (PBE using AES-CBC). I decided to use a random salt with the passphrase to derive the 128-bit key (prevent dictionary attack on the passphrase), and of course use IVs (to prevent statistical analysis for packets). However I am concerned about few things: Each packet contains small amount of data (like a couple of integer values per packet) which will make the encrypted packets vulnerable to known-plaintext attacks (which will result in making it easier to crack the key). Also, since the encryption key is derived from a passphrase, this will make the key space way less (I know the salt will help, but I have to send the salt through the network once and anyone can get it). Given these two things, anyone can sniff and store the sent data, and try to crack the key. Although this process might take some time, once the key is cracked all the stored data will be decrypted, which will be a real problem for my application. So my question is, what is the best practices for sending/encrypting continuous small data using a connectionless protocol (UDP)? Is my way the best way to do it? ...flowed? ...Overkill? ... Please note that I am not asking for a 100% secure solution, as there is no such thing. Cheers

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• HMAC URLs instead of login?

  - by Tres

  In implementing my site (a Rails site if it makes any difference), one of my design priorities is to relieve the user of the need to create yet another username and password while still providing useful per-user functionality. The way I am planning to do this is: User enters information on the site. Information is associated with the user via server-side session. User completes entering information, server sends an access URL via e-mail to the user roughly in the form of: http://siteurl/<user identifier>/<signature: HMAC(secret + salt + user identifier)> User clicks URL, site looks up user ID and salt and computes the HMAC with the server-stored secret and authenticates if the computed HMAC and signature match. My question is: is this a reasonably secure way to accomplish what I'm looking to do? Are there common attacks that would render it useless? Is there a compelling reason to abandon my desire to avoid a username/password? Is there a must-read book or article on the subject? Note that I'm not dealing with credit card numbers or anything exceedingly private, but I would still like to keep the information reasonably secure.

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• Best way to implement plugin framework - are DLLs the only way (C/C++ project)?

  - by Microkernel

  Introduction: I am currently developing a document classifier software in C/C++ and I will be using Naive-Bayesian model for classification. But I wanted the users to use any algorithm that they want(or I want in the future), hence I went to separate the algorithm part in the architecture as a plugin that will be attached to the main app @ app start-up. Hence any user can write his own algorithm as a plugin and use it with my app. Problem Statement: The way I am intending to develop this is to have each of the algorithms that user wants to use to be made into a DLL file and put into a specific directory. And at the start, my app will search for all the DLLs in that directory and load them. My Questions: (1) What if a malicious code is made as a DLL (and that will have same functions mandated by plugin framework) and put into my plugins directory? In that case, my app will think that its a plugin and picks it and calls its functions, so the malicious code can easily bring down my entire app down (In the worst case could make my app as a malicious code launcher!!!). (2) Is using DLLs the only way available to implement plugin design pattern? (Not only for the fear of malicious plugin, but its a generic question out of curiosity :) ) (3) I think a lot of softwares are written with plugin model for extendability, if so, how do they defend against such attacks? (4) In general what do you think about my decision to use plugin model for extendability (do you think I should look at any other alternatives?) Thank you -MicroKernel :)

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• iPhone Custom CA certificate for an application which uses NSURLConnection?

  - by jr

  I have an application which is communicating with many different sites and each site has its own SSL certificate signed by our own internal CA. Doing this prevents us the need from purchasing SSL certificates for each site (hundreds or thousands) and is more secure then using a wildcard certificate with a shared key on each of those sites. So, basically using a CA certificate is the only way. Right now, I have a mobileprovision file which will install the CA certificate as a profile on the phone. When our iPhone application launches if it gets an SSL Certificate error it redirects to a this mobile provision file via Safari and the user will be prompted to install the CA. The problem is that I am concerned that the Apple AppStore might deny my app for doing this (Just some feedback from other developers at this point), and I wanted to research other ways to accomplish this. Basically what I need to accomplish is allow an SSL connection which will verify against a custom CA certificate which will be embedded in my application. This will make the CA certificate active for only the calls I make. I am using the standard NSURLConnection methods in order to communicate with the service. Is this possible? Can someone show me how to load the CA (what form PEM?) and add it to the list of trusted CA certificates for my application? If that is not possible what other options do I have? Just trusting all certificates isn't really any option, we want to prevent man in the middle attacks and only trust our CA issued certificates. Thanks!

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• Security of Flex for payment website

  - by Mario

  So, it's been about 3 years since I wrote and went live with my company's main internet facing website. Originally written in php, I've since just been making minor changes here and there to progress the site as we've needed to. I've wanted to rewrite it from the ground up in the last year or so and now, we want to add some major features so this is a perfect time. The website in question is as close to a banking website as you'd get (without being a bank; sorry for the obscurity, but the less info I can give out, the better). For the rewrite, I want to separate the presentation layer from the processing layer as much as I can. I want the end user to be stuck in a box and not be able to get out so to speak (this is all because of PCI complacency, being PEN tested every 3 months, etc...) So, being probed every 3 months has increasingly made me nervous. We haven't failed yet and there hasen't been a breach yet, but I want to make sure I continue to pass (as much as I can anyways) So, I'm considering rewriting the presentation layer in Adobe Flex and do all the processing in PHP (effectively IMO, separating presentation from processing) - I would do all my normal form validation in flex (as opposed to javascript or php) and do my reads and writes to the db via php. My questions are: I know Flash has something like 99% market penetration - do people find this to be true? Has anyone seen on their own sites being in flash that someone couldn't access it? Flash in general has come under alot of attacks about security and the like - i know this. I would use a swf encryptor - disable debugging (which i got snagged on once on a different application), continue to use https and any other means i can think of. At the end of the day, everyone knows if someone wants in to the data bad enough, their going to find a ways in; i just wanna make it as difficult for them as i can. Any thoughts are appreciated. -Mario

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