We need to design a secure web application. I would like to propose a session handling mechanism which does a challenge-response on every request, not only during login using a CRAM method.
The reason is to harden the web application against session hijacking (eg by CSRF) and replay or man-in-the-middle attacks.
Using a nonce is suggested in some places, but in our webapp it seems impractical, as asynchronous requests can go on, or the user could open new windows, hit the back button etc.
Idea: The client and the server have a shared secret (a previously established user password), every subsequent request does again a challenge/response based on that secret, e.g 'response = hash(challenge + hashedPassword)'. The server executes the request only if the response to the challenge matches. Much like during CRAM, but ongoing for every request.
The question: Is this a feasible idea? If so, it surely has been implemented or is even some standard? How would we use this in a java or php based webapp?
The question really comes down to what you want to achieve. If you want to fight CSRF-Attacks, a secret token in addition to the session key is your way to go. However, changing the token in every request will cause problems - not only will the back-button kill the session, but as one webpage usually contains a lot of asynchronously and parallel loaded data (images, css, javascript, etc.), your approach will not enable any additional data to be loaded afterwards, as each additional request will change the required token, thus killing the session.
You may get around this by embedding all resources into the page via BASE64 and other tricks, but that will seriously hinder your possibilities and may have compatibility issues with some browsers.
So, in the end, your approach will not add much security, but will most likely create a whole set of potential problems for your customers. I'd stick to one secret token per session in the URL to fight CSRF and concentrate on securing against other attacks like XSS and user-friendly security measures like two-factor authentication with a smartphone or something similar. After all, the user is the #1 attack vector nowadays.
Update (2012-06-14)
The token will not fight XSS-attacks, but it will defend against basic CSRF-attacks (e.g. by implanting a bogus url call in an image). I've actually had a situation at work today, where I needed to secure a get-request against user modification and worked up some code. The code may be also usable to secure static, session-timeout form- and link-tokens (right your problem).
The idea is to have a server-secret, which is used to generate a hash/AuthToken over data to secure. If a rogue javascript would try to change any of the given data, the AuthToken would not match. In my specific problem, I have one server authenticating a user and have to send his information over to a third party (username, mailaddress, name, etc.). This GET-Request might be easily changed by any user after authentication, so I have to authenticate the GET-Request-Parameters. By rerunning the AuthenticationToken-Process, the third party can compare the resulting AuthTokens, thus validating the incoming data. Without the shared secret, it is (near-to) impossible to forge the data.
On your problem: Having a static token on GET and POST-requests (or a dynamic one like the project of mine) will protect you against simple CSRF-attacks via e.g. links in forums, which a user has to click to get attacked. As the link will never contain the correct token, your webpage is secure. However, if an attacker manages to load a javascript into the webpage via XSS, you're screwed and no technique in the world will help against it, as the javascript can scan the whole DOM-tree of the page to find an capture any tokens whatsoever.
So, it comes down to this:
use tokens on GET and POST-requests to fight CSRF
secure your page against XSS-injections
I find the OWASP cheat sheets are a good resource for such design decisions:
CSRF Prevention Cheat Sheet
XSS Prevention Cheat Sheet
Your scheme sounds similar to the HTTP digest authentication without establishing any kind of session post authentication. Which is probably an improvement over HTTP Basic. And that is assuming both are over TLS!
I am not sure how feasible your scheme might be or how vulnerable to replay attacks or MITM it might be.
If it is an option you might consider the new <keygen> html5 tag which can help establish a two way TLS session. This would be the most secure option..
Related
I am building my own authentication microservice and although I have the main setup in place (generating access tokens etc.), I am a bit lost when it comes to refresh tokens.
I feel there are a lot of different way to handle this.
You can either store them in Redis or in the database.
You can use a whitelist or a blacklist them
Right now, my idea is to add another database table that links a valid refresh token to a user entity. When a user hits the logout endpoint, the refresh token gets destroyed.
I was wondering if this was a good solution and otherwise, if there are other possible solutions to consider. I have seen a number of articles when googling but they stem from anywhere between 2015 and 2019, and they all have different approaches.
The issue with refresh tokens is not so much where or how you store them on the server side, as well if and how you store them on the client side.
It all depends on whether you can trust your client (software using the token) to keep secrets. You only want to issue refresh tokens to a client you can trust to keep these tokens secure. Typically, this means only issue refresh tokens to confidential clients, i.e. web applications that run on a web server. These clients can also have their own (client) credentials to authenticate themselves with when using the refresh token.
For public (non-confidential) clients, like Single Page Applications, some OAuth2 libraries use an hidden IFRAME and a cookie session with the authorization server to issue new access tokens.
So, the answer to your question depends on what kind of clients you will be using.
I know following are the ways to maintain or session tracking in java but looking for a good one
URL rewritting
Hidden form fields
cookies
Session object like setAttribitute() and session.getAttribute()
If the client browser has blocked accepting and storing cookies then last 2 ways are not valid.In hidden form fields I need to pass the hidden values in each and every page inside form.So suppose If I am just using response.sendRedirect() Then hidden form field is of not use.The remaining is URL rewriting in which I will pass JsessionID in the URl.So My question by knowing the sessionID isnt the unauthorized persons can able to access the pages.
For example There are 3 pages login,register,send.So after login user can register and/or send.So if any one knows the sessionID cant he/she go direct to register/send page.If yes Please tell me how to prohibit this
As of Servlet 3.0 (Apache Tomcat 7 onwards) if you use SSL then you can configure your application to track sessions based on the SSL session ID. The downside is that everything has to be over SSL. The advantages are that the session is strongly tied to the SSL connection. Only the user that created the connection to the server that has the correct SSL session has access to the session. Even if an attacker knows the session ID, they can't access the session.
One word of caution, this form of session tracking is the least widely used so it may not have been as heavily tested as the more usual cookie and URL re-writing mechanisms.
Have a look at this link which outlines Best practices for using HTTP sessions
Including
javax.servlet.http.HttpSession.invalidate()
Use HTTPS
With standard solutions you can't.
You can add some measure of security by adding request originator IP address verification, but that's also fooled easily. (to clarify some here means very tiny itsy bitsy little bit of)
So the secure route is to not use URL Rewriting to maintain session in secure application.
However you may be able to get some security by keeping the JSessionID as a separate encrypted attribute that which will be decrypted by a middle-ware or a load balancing server sitting between the client and your application servers. This of course is just a thought, I haven't, fortunately ever had to try something like that out :-)
Session tracking & authentication are two diff things don't club them.
Understanding your requirement I see you want to secure the sessionid of the user.
Evasdroping: If someone is listing to the request & response in the middle he can take the sessionid and use it. The best way would be to use a SSL. This ensures no one is listening in the middle.
Sessionid stolen from Client side: Normally this should be taken care by the browser and OS. So your user is as secure as the system he has.
What is the value of using a authentication token when using a REST webservice instead of sending a username, password over HTTPS/Encryption each time you make a request?
I understand that for instance OAUTH has some benefits cause you don't need to give away your password to 3rd parties, you can pass a token to trusted 3rd parties whom you dont want to share the username/password..etc
But other than this special benefits above which I certainly dont need in my case, why would I use tokens instead of sending username/password everytime.
This might be to make life easy for client, and it does not have to send the username/password everytime. Well ok but then now client has to remember my token and send me the token on every request. So instead of remembering/sending username/password now it will do the same for tokens! So client implementation code does not get any less.
So what is the real value here?
It really depends on the scenario - it's hard to tell without knowing more about the API - but usage of "authentication tokens" is far from universal, you're right that many APIs don't need (and don't use) them. Many APIs simply require an API key to be sent with every request (often via HTTPS to prevent it from being intercepted), or require an API key to identify the user and also a digital signature with a "secret key" to prove the user's identity (see When working with most APIs, why do they require two types of authentication, namely a key and a secret? ).
Usernames/passwords are not often used in public APIs because they're not flexible enough and do not provide enough "separation" between the user identity and the application identity. E.g. you register as a developer to use the Flickr API and create an iPhone app that uses that API - would you really want your developer username/password to be built into the app? What if you change your password later? What if you want to develop 5 apps and track usage for them separately and be able to shut off any app at any time without affecting the others?
However, for cases where you truly want to identify a human user only, not an appplication (e.g. a private API back-end that will only serve your own applications, not a public API), in most scenarios I don't see anything wrong with what you suggested, i.e. username/password over HTTPS with every request. Oh, by the way, auth tokens have the added advantage of being "restrictable" (can expire at a certain time, can be restricted to certain actions only, etc), but obviously this is only useful in very specific scenarios.
ALSO: As user "Dan" pointed out above, when designing an API that requires sending the username/password with every request (or with any request really, even if it's just the login request), be careful how you do it. If you're using a technique which browsers support by default (e.g. HTTP Basic Auth), you're preventing yourself from ever exposing the API safely to cross-domain users (i.e. most likely your API can never be safely called directly from the browser, i.e. from AJAX / Flash / Silverlight code).
This is a complex topic which can't be explained fully here, but just remember that if your API is relying on any security credentials that the browser can remember and then "silently" inject in every request (e.g. HTTP Basic Auth, cookies), then it's NOT safe to enable cross-domain access to that API using any cross-domain technique (CORS, JSONP, crossdomain.xml, etc).
The best way I can answer this is to point you to this page describing REST security. It belongs to the restlet wiki, not to Jersey, but it can be applied to Jersey as well as they are both REST implementations.
This is extracted from the link I provided:
"For the most resistance, the server can present the client with an application level authorization token, an opaque value that the server can verify belongs to the right authenticated user.
Such a token should be be difficult for a third party to calculate, e.g. a server-salted MD5 or SHA1 hash of the user's identification credential.
To defeat XSRF, this application-level token needs to be transmitted by means that the user-agent does not automatically return with each request. For example, it can be sent in the HTML of a form as a hidden field, and returned via POST in the encoded form entity."
My company is building a RESTful API that will return moderately sensitive information (i.e. financial information, but not account numbers). I have control over the RESTful API code/server and also am building the Android app. I've setup the API to use OAuth 2 with authorization code grant flow (with client ID and secret), and I auto-approve users without them having to approve the client since we own both client and provider. We use CAS for SSO and I am using this for the Authorization server as part of the OAuth 2 process when the user logs in to retrieve the token.
I am contemplating various ways to secure the data on the Android app. I've concluded that storing the client id and secret on the device is definitely not going to happen, but am thinking that storing the auth token might work, since it is only risk to the individual user (and really only if they happen to have a rooted phone).
Here are two options I have thought of. They both require me to have a sort of proxy server that is CAS protected, does the dance with the API server, and returns the auth token. This gets rid of the need for storing the client id and secret in the app code.
Here are what I've come up with:
1) Require the user to enter their password to access data each time they startup the App. This is definitely the most foolproof method. If this were done, I'd probably want to save the userID for convenience, but in that case couldn't use the CAS login (since it's web-based). I might be able to use a headless browser on the backend to log the user into CAS and retrieve the token based on what they enter in the Android form, but this seems hacky. Saving the userID is similar to what the Chase app does (if you happen to use this one) - it saves the userID but not your password between sessions.
2) Store the auth token on the Android device. This is a little less secure, but almost foolproof. When the user starts the app for the first time, open the webpage to the CAS login of the proxy server that returns the token (similar to https://developers.google.com/accounts/docs/MobileApps). After the user logs in and the token is returned to the app, encrypt it and store it private to the application. Also, use ProGuard to obfuscate the code, making the encryption algorithm more difficult to reverse engineer. I could also work in a token refresh, but I think this would be more of a false sense of security.
3) Don't use CAS but come up with another way to get an auth token for the service.
Any advice of how others have implemented similar scenarios (if it's been done)?
Thanks.
Well the reason why standards like OAuth are developed is that not everyone has to rethink the same attack vectors again and again. So most often it is your best choice to stick to something already available instead of baking your own thing.
The first problem with clients that are not capable of secretly storing data is that the user's data could be accessed by some attacker. As it is technically not possible to prevent this (code obfuscation won't help you against an expert attacker), the access token in OAuth 2 typically expires after short time and doesn't give an attacker full access (bounded by scope). Certainly you shouldn't store any refresh token on such a device.
The second problem is client impersonation. An attacker could steal your client secret and access your API in his own (maybe malicious) app. The user would still have to login there himself. The OAuth draft there requires the server to do everything it can to prevent this, but it is really hard.
The authorization server MUST authenticate the client whenever possible. If the authorization server cannot authenticate the client due to the client's nature, the authorization server MUST require the registration of any redirection URI used for receiving authorization responses, and SHOULD utilize other means to protect resource owners from such potentially malicious clients. For example, the authorization server can engage the resource owner to assist in identifying the client and its origin.
I think Google are the first to try another approach to authenticate a client on such devices, by checking the signature of the application, but they are not yet ready for prime time. If you want more insight into that approach, see my answer here.
For now, your best bet is to stay on the OAuth way, i.e. having the access token, client ID and client secrect (when using the authorization code grant flow) on the device, and configure your server to do additional checks. If you feel more secure obfuscating these, just do it, but always think of it as if these values were publicly available.
I'm developing a server component that will serve requests for a embedded client, which is also under my control.
Right now everything is beta and the security works like this:
client sends username / password over https.
server returns access token.
client makes further requests over http with the access token in a custom header.
This is fine for a demo, but it has some problems that need to be fixed before releasing it:
Anyone can copy a login request, re-send it and get an access token back. As some users replied this is not an issue since it goes over https. My mistake.
Anyone can listen and get an access key just by inspecting the request headers.
I can think of a symmetric key encryption, with a timestamp so I can reject duplicate requests, but I was wondering if there are some well known good practices for this scenario (that seems a pretty common).
Thanks a lot for the insight.
PS: I'm using Java for the server and the client is coded in C++, just in case.
I don't get the first part, If the login request is https, how can anyone just copy it?
Regarding the second part, t This is a pretty standard session hijacking scenario. See this question. Of course you don't have the built-in browser options here, but the basic idea is the same - either send the token only over a secure connection when it matters, or in some way associate the token with the sending device.
In a browser, basically all you have is IP address (which isn't very good), but in your case you may be able to express something specific about your device that you validate against the request to ensure the same token isn't being used from somewhere else.
Edit: You could just be lucky here and be able to rule out the IP address changing behind proxies, and actually use it for this purpose.
But at the end of the day, it is much more secure to use https from a well-known and reviewed library rather than trying to roll your own here. I realize that https is an overhead, but rolling your own has big risks around missing obvious things that an attacker can exploit.
First question, just to get it out there: if you're concerned enough about nefarious client-impersonator accesses, why not carry out the entire conversation over HTTPS? Is the minimal performance hit significant enough for this application that it's not worth the added layer of security?
Second, how can someone replay the login request? If I'm not mistaken, that's taking place over HTTPS; if the connection is set up correctly, HTTPS prevents replay attacks using one-time nonces (see here).
One of the common recommendations is - use https
https man in the middle attack aside using https for the entire session should be reliable enough. You do not even need to worry about access tokens - https takes care of this for you.
Using http for further requests seems to introduce some vulnerabilities. Now anybody with a network sniffer can intercept your traffic steal the token and spoof your requests. you can build protection to prevent it - token encryption, use once tokens, etc. but in doing so you will be re-creating https.
Going back to the https man in the middle attack - it is based on somebody's ability to insert himself between your server and your client and funnel your requests through their code. It is all doable i.e. in case the attacker has access to the physical network. The problem such attacker will face is that he will not be able to give you a proper digital certificat - he does not have the private key you used to sign it. When https is accessed through a browser, the browser gives you a warning but still can let you through to the page.
In your case it is your client who will communicate with the server. And you can make sure that all proper validations of the certificate are in place. If you do that you should be fine
Edit
Seconding Yishai - yes some overhead is involved, primarily CPU, but if this additional overhead pushes your server over board, you have bigger problems with your app