I am using the WebBrowser control to add a WebInterface to C# app. My desire is to verify that only such app is able to connect to our Web server using SSL client certificates.
My idea was to embed the client certificate in the app and just use when connecting via my app. Anybody have a sugestion on how to do this? Or the only way to make it work is to load the key in the X509Store.
If I put it in X509Store, will it make my key available for general Internet Explorer Usage?
Are you sure this is what you want to do? If you embed the private key in your application (as your approach entails), an attacker can extract it and use it to authenticate their rogue software.
A server cannot authenticate client software. It can only test whether a client possesses some secret. When you embed a private key in your client and distribute it, it will not be a secret anymore.
I'd recommend authenticating users of your software, rather than the software itself. You need to let users generate their own secret, whether it is a password or a private key, and give them an incentive to protect it.
So, several thoughts here:
1.
I agree with 'erickson', validating that ONLY your app can communicate with the app is nearly impossible with your current design. It's just a matter of time before someone reverse engineer's your app and then its game over (if that's you only form of security). If you want to validate that its your app and a valid user then you need to authenticate the user as well as some mechanism of checking the signature of the app in question (which I don't believe is possible in a client-server model...after all I can always lie and say that my 'hackyou' app has the same signature as your 'realapp' and you can't verify that from the server-side)
2.
Remember the WebBrowser control is essentially a wrapper around IE, so without some tricks (which I'll get to in a sec) you would have to add the cert to the user store.
3.
Here's a hacky way to accomplish what you're asking (even though its a bad idea):
First use the WebRequest.Create to create a HttpWebRequest object
Manually load a X509Certificate2 object from either a file or the binary stream encoded in the program
use the HttpWebRequest.ClientCertificates to add your cert to the webrequest
Send the request, get the response
Send the response to the WebBrowser by pushing the ResponseStream of the HttpWebResponse to the DocumentStream of the WebBrowser
This essentially means that you will have to write some wrapper classes to handle the Requests and Responses to and from the Server and are just using the WebBrowser to handling the viewing of the HTML.
In reality, you need to redesign and look at the threats you're trying to handle!
The intent of using the key is not so much to validate the users as to restrict access to users of the app instead of using any WebBrowser. This is sort of an intranet behavior over the public internet.
This is a poor man's DRM. The losses due to people extracting the key are not that important. I think the risk of this happening is low and what we could loose is minimal.
Nevertheless if there is any other idea to restrict access to the WebServer to only users of the App I am open for any suggestions. Basically my desire is now to have a public WebServer wide open to be read by anyone, but access over the public network from diverse places is necessary so setting up a intranet infrastructure is not possible either.
Related
I'm trying to create a desktop application that will send updates to a web-service I am developing.
Ideally, the application would be configured only once and deployed to a network share. When configuring the application, the user will enter a password that is used to authenticate within the web-service. After that, a token will be created to be used on future connections.
This would allow any computer with access to the network share (even if it is not the computer in which the app was configured) to just run the application (which will connect to the web-service) without entering any credentials (because the token has been saved).
Question is: How should I protect this token?
I know that storing it client-side will never be completely secure, but I want to make it as hard as possible for someone to gain access to the plaintext token.
I'm looking for an answer that, preferably, does not depend on any operational-system resource (since the application can be executed from different devices).
Assume I have full control over the application and the web-server
I'm developing the console application using C#, but I believe this to be more of a theoretical question (not tied to any specific language)
Here are a few things I've tried/thought about:
Serializing the token using something like C#'s SecureString and storing it on a file: it's the best I've come with. But obviously, very trivial to reverse if someone gains access to the key file.
This answer suggests to use the Windows Data Protection API (DPAPI) (in C#, the ProtectedData class), but apparently, this would allow only the user who initially saved the credentials to access them, which would not work because I have to access the protected data from multiple users/devices.
Pass the token as a parameter to the application: this just changes where I'm going to store the token (on a batch file or OS task that calls the program, for example), but I don't think it makes it any more secure.
Since the user is not an administrator of the machine (this is a fundamental hypothesis), there are many ways to hide things from her.
What I propose is:
Make sure the main app runs under different credentials than the
logged user, a "special user".
Write another end-user app, just for setup, that talks to this app (using any interprocess communication you see fit, TCPIP, whatever, maybe secure but I wouldn't care too much at this). This app is used only to gather credentials and send them to the first app
Now, the main app can write the token anywhere the logged user has no access, but I recommand protected data because it's very easy to use
Here is some graphical explanation:
Since data encrypted using protected data (Windows Data Protection) can only be decrypted by the Windows user who has encrypted it, the logged on user will not be able to read the "special user" data.
I would suggest using JWT.
Your server would generate a Token after a successful authentication. The token would be sent to the client. Each subsequent call to the server would send the token in the header to the server. The server would then verify the token. If verified, the server knows the client has been authenticated.
No need to store usernames/passwords on the client.
There is no bullet-proof way to solve this problem, the client finally needs access to the server, and so can do an attacker with enough privileges on the client.
What you describe is a typical scenario for the OAuth2 protocol, since you have control over the server. With OAuth2 you cannot avoid the need to store a secret on the client, but by exchanging it for a token, you can protect the original password and you can guarantee that the token is very strong (user passwords tends to be weak).
To store the token/password on the client one could encrypt it before storage, but this immediately raises the question of where to store the key for this encryption. An attacker could extract it from the client. There are some ways, which can improve security for the key storage.
Depending on your situation you may consider the usage of a Hardware security module (HSM).
You can use an OS specific key-store like you mentioned with the data-protection-api. A key-store can only help protecting a key, because it has the support of the operating system (I think this is what you meant with SO-independend?). With the DPAPI you can not only restrict access to the logged in user, rather you can restrict it to the local machine. Key-stores are available on other operating systems as well.
Instead of storing the password on the client, it can be requested from the user each time the client starts. This can be reduced to the startup of the device, the password can then be hold exclusively in the memory.
Well, you can't protect anything in client side. Once it's there, anyone with privileged access can see it.
What you can do is make this piece of information useless without something else.
The best approach here would be to store a kind of public key in the client side and use this public key to create a hash to authenticate the user via webservice.
When the user configure the application, the server send this public key that the application stores locally. When the application call the server it will create a hash using this public key and a private key that is only known by the application and the server. Then the server can check if the hash is correct using its private key.
To improve security, you can use a timestamp in the hashing too, so it will change overtime and prevent the reuse of keys. Or it could send a new public key with the each webservice answer.
I would suggest you to use IdentityServer4 as it provides RFC compliant protocols and depending on the GrantType a client application is given in your context your desktop application.
Even though the token is in plaintext it is protected in the webservice where the Access Control(Issuer of token) validates that a token is being received from the correct client by checking the Origin in the clients request and the one stored in the database.
Introduction
Okay so I've got a website (PHP) with a database (MySQL). You can create an account on this website and edit your details and so on (let's say date of birth, real name, address, and so on).
Now, what I wanna do is to create a desktop application (most likely c# with WPF) that interacts with a REST api (in PHP) from the website, which will allow to :
Create accounts directly from the application
Log in to your account
Be able to edit your details directly from the application
As of now I only want to do a desktop application, but it might evolve into a mobile app. I don't think that is relevant though.
Creating accounts and logging in
I'm struggling with the create account / log in part. I want it to be as secure as possible. On the website, I'm using password_hash(PASSWORD_BCRYPT) with a cost of 10 to store passwords in the database, and password-verify to check log ins.
Regarding the application, I imagine the way to go is to pass the username and password to the REST api and do the encryption directly on the server side. But sending the password itself sounds terrible so I thought about encrypting it with a secret key that only the application and the website know, so the website can figure out the password and encode it correctly in the database.
If I'm right, what encryption algorithm should I use? If not, how should I do that?
Edit your details directly from the application
I'm thinking about doing the following : Let's say the user has logged in through the application. If the authentication is successful, the server randomly generates a token (I'll probably use ircmaxell's Random-Lib) and send it as a reply to the application. From then onward, when the application wants to make a request to the api, it adds the username to the datas string, and generates a hash (sha256 for example) with the data string plus the token; then the server can repeat the exact process using the token stored in database to make sure the user actually has the right to access/modify his details, and nobody is trying to pretend to be an user he isn't.
I feel like the problem is, if someone listens to the first api reply after the authentication, he gets the token and can use it to act as if he was the user. Would encrypting it with the same process used for the password be enough to make sure this can't happen?
Last but not least, if I want the user to be able to be directly logged in the next time he starts the application, I guess I have to give the token a permanent durability and store it in a file or something on the computer. But that doesn't sound really safe because anyone could just read the file content and figure out the token.
Final questions
So. What do you think ? Does it sound good or am I completely off the tracks?
The website hosting is in http://* so I guess using HTTPS communications is not an option here. I know that's a big problem to create something really secured, but I'd still like to make something as safe as possible with what I have.
Thanks a lot for your advices. :)
Btw I tried to make this as clear as possible, hope it worked. I have close to pretty little knowledge of security, encryption, ... so you'll have to speak like to a 3 years old to me.
I think the first, most important piece of advice I could give is to never try to roll your own security code, unless you are an absolute expert. You'll want to put together a solution based on the frameworks that .net provides for you.
First things first - your REST API. I'd suggest building on top of ASP.NET Web API. HTTPS is mandatory here - if your hosting provider can't give it to you, you need a new hosting provider. It also conveniently takes care of encryption for you.
There are various security options available for ASP, I'd read this for a detailed overview: https://docs.asp.net/en/latest/security/. Using the existing ASP options will also take care of your requirements around user account creation and self-service.
I asked a question here a while back on how to hide my http request calls and make them more secure in my application. I did not want people to use fiddler 2 to see the call and set up an auto responder. Everyone told me to go SSL and calls will be hidden and information kept safe.
I bought and installed an SSL Certificate and got everything set up. I booted up fiddler 2 and ran a test application that connect to an https web service as well as connected to an https php script.
Fiddler 2 was able to not only detect both requests, but decrypt them as well! I was able to see all information going back and fourth, which brings me to my question.
What is the point of having SSL if it made zero difference to security. With or without SSL I can see all information going back and fourth and STILL set up an auto responder.
Is there something in .NET I am missing to better hide my calls going over SSL?
EDIT
I am adding a new part to this question due to some of the responses I have received. What if an app connects to a web service to login. The app sends the web service a username and a password. The web service then sends data back to the app saying good login data or bad. Even if going over SSL the person using fiddler 2 could just set up an auto responder and the application is then "cracked". I understand how it could be useful to see the data in debugging, but my question is what exactly should one do to make sure the SSL is connecting to the one it was requesting. Basically saying there cannot be a middle man.
This is covered here: http://www.fiddlerbook.com/fiddler/help/httpsdecryption.asp
Fiddler2 relies on a "man-in-the-middle" approach to HTTPS interception. To your web browser, Fiddler2 claims to be the secure web server, and to the web server, Fiddler2 mimics the web browser. In order to pretend to be the web server, Fiddler2 dynamically generates a HTTPS certificate.
Essentially, you manually trust whatever certificate Fiddler provides, the same will be true if you manually accept certificate from random person that does not match domain name.
EDIT:
There are ways to prevent Fiddler/man-in-the-middle attack - i.e. in custom application, using SSL, one can require particular certificates to be used for communication. In case of browsers, they have UI to notify user of certificate mismatch, but eventually allow such communication.
As a publicly available sample for explicit certificates, you can try to use Azure services (i.e. with PowerShell tools for Azure) and sniff traffic with Fiddler. It fails due to explicit cert requirement.
You could set up your web-service to require a Client-side certification for SSL authentication, as well as the server side. This way Fiddler wouldn't be able to connect to your service. Only your application, which has the required certificate would be able to connect.
Of course, then you have the problem of how to protect the certificate within the app, but you've got that problem now with your username & password, anyway. Someone who really wants to crack your app could have a go with Reflector, or even do a memory search for the private key associated with the client-side cert.
There's no real way to make this 100% bullet proof. It's the same problem the movie industry has with securing DVD content. If you've got software capable of decrypting the DVD and playing back the content, then someone can do a memory dump while that software is in action and find the decryption key.
The point of SSL/TLS in general is so that the occasional eavesdropper with Wireshark isn't able to see your payloads. Fiddler/Burp means that you interacted with the system. Yes, it is a very simple interaction, but it does require (one) of the systems to be compromised.
If you want to enhance the security by rendering these MITM programs useless at such a basic level, you would require client certificate authentication (2-way SSL) and pin both the server and client certificates (e.g. require that only the particular certificate is valid for the comms). You would also encrypt the payloads transferred on the wire with the public keys of each party, and ensure that the private keys only reside on the systems they belong to. This way even if one party (Bob) is compromised the attacker can only see what is sent to Bob, and not what Bob sent to Alice.
You would then take the encrypted payloads and sign the data with a verifiable certificate to ensure the data has not been tampered with (there is a lot of debate on whether to encrypt first or sign first, btw).
On top of that, you can hash the signature using several passes of something like sha2 to ensure the signature is 'as-sent' (although this is largely an obscure step).
This would get you about as far in the security way as achievable reasonably when you do not control (one) of the communicating systems.
As others mentioned, if an attacker controls the system, they control the RAM and can modify all method calls in memory.
I have an app in C# which serializes an object into xml into a http stream to my server. The server has some php which runs a stored procedure in mysql with the xml data as its only parameter.
The problem is that someone could very easily just send up an xml of the same format with a whole lot of entires that would ruin the database with crap data. What are my options to prevent this from happening?
I'm pretty new to web requests so I don't even know where to start.
We require a username and password to be supplied to all input parameter lists which is validated against our back-end user login system before a request is processed. Low tech, but works for us.
You should use some form of authentication and authorization. In SOAP based services there's the WS-Security extension. Here's another article on MSDN that explains how this works. However I have no idea what is the support for those standards on the PHP side. If you are using some custom protocol you could simply require a username/password to be sent along with the request and verified on the server side.
Are you planning on having this client out-there in public hands on the internet? If so it may be impossible to prevent people using different software as they could always reverse engineer the application to find out what security mechanism you are using. As a result your only defence will be to validate the data thoroughly on the server.
You might get around this by modifying the client to require a user name and password that gets sent with data to your server using HTTPS, that way at least you know who did the damage. If however you have a more closed audience you could use some kind of client certificate system or IP filtering.
Our solution (and we're hopelessly naive in this respect) is that we generate a unique key per session on the server in a non-uniform manner (ie. it is difficult to predict what the "next" value would be), and give that to the client code as part of its login process. It is then required to pass that value back to use for each request as the first parameter.
This ensures that:
Logging out invalidates the authentication key
Username and password is not sent in cleartext for the web service requests
This does not ensure that:
Only our application code can talk to the server (the user might intercept the request, copy the key, and generate his own requests, as long as the key is still considered valid.)
What you're going to find is that as long as code on the users machine is talking to your server, you have no control over the code on that machine, only the code on that server. So if the users machine is sending you requests originating from a different program, that looks just like they would and should if your code generated them, you're going to have a hard time figuring out that this is what is happening.
I'm building a system that consists of many clients connecting to a server. The clients automatically push data to the server via a web service call.
I've built an authentication mechanism in order for the clients to authenticate with the server so only authenticated clients can upload data.
The problem is that I've hardcoded the password into the client code and it is accessible if someone uses a reflector.
In this scenario, where I have no user input, what would be the best way to store the static password on the client?
Thanks
(.Net version on the client is 2.0 and the .net version on the server is 3.5)
You have a number of methods that you can use, but one of the easiest to implement would be to encrypt the password and then just store it in the app.config for the application that gets deployed to the user.
Have you looked at http://msdn.microsoft.com/en-us/library/system.security.cryptography.protecteddata.aspx?
Also, are your webservices WCF? If so, you could use mutual certificate security. It is much more robust than a password.
HTH
"I've built an authentication mechanism in order for the clients to authenticate with the server so only authenticated clients can upload data."
How are they authenticated to become "authenticated clients"?
Can someone just copy your application to their home computer and now they are an authenticated client?
This seems like a huge security oversight if you're trying to decide who can upload based on a value in your assembly.
If you can do IP based validation, if you want to avoid passwords and login mechanisms.
I would consider getting a good obfuscator for your code, for one thing. That will prevent (or at least deter) people from using reflector on your assemblies.
However, your authentication system doesn't sound too secure. Even if you did encrypt the password, if the password is always the same, it would be as easy as sniffing packets to figure out what needed to be sent to your server to authenticate. Because it would have to be decrypted before it was sent.
You'd have to go over an SSL at the very least.
Also you might want to look into using Asynchronous Encryption with Signed XML using a Machine Hash if you're installing this in some public client's environment. Something like a Licensing Scheme.
I don't know anything about your architecture or the environment you're running in, so I can't make any recommendation as to what would be the best security implementation, but I can tell you the current setup doesn't sound secure to me.