How to make sure that my AJAX requests are origina

Question

I have already asked a question about IP Authentication here: TastyPie Authentication from the same server

However, I need something more! An IP address could be very easily spoofed.

Scenario: My API (TastyPie) and Client App (in javascript) are on the same server/site/domain. My users don't login. I want to consume my API in my javascript client side.

Question: How can I make sure (authentication) that my AJAX requests are originating from the same server?

I'm using Tatypie. I need to authentication that the requests from the client are being made on the same server/domain etc. I cannot use 'logged in sessions' as my users don't login.

I have looked at private keys and generating a signature but they can viewed in the javascript making that method insecure. If I do it in a way to request a signature form the server (hiding the private key in some python code) anyone can make the same http request to get_signature that my javascript makes, thus defeating the point.

I also tried to have the Django view put the signature in the view eliminating the need to make the get_signature call. This is safe, but means that I have to now refresh the page every time to get a new signature. From a users point of view only the first call to the API would work, after which they need to refresh, again pointless.

I cannot believe I'm the only person with this requirement. This is a common scenario I'm sure. Please help :) An example using custom authentication in Tastypie would be welcome too.

Thanks

Added:

Answer 1

Short answer: It is not possible to prevent a dedicated attacker.

You have no method of identifying a client other than with the information that they give you. For instance, username/password authentication works under the assumption that only a valid client would be able to provide valid credentials. When someone logs in, all you know is that some person provided those credentials -- you assume that this means that this means that they are a legitimate user.

Let's take a look at your scenario here, as I understand it. The only method you have of authenticating a client is IP Address, a very weak form of authentication. As you stated, this can be easily spoofed, and in with some effort your server's response can be received back to the attacker's original IP address. If this happens, you can't do anything about it. The fact is, if you assume someone from a valid IP address is a valid user, then spoofers and legitimate users are indistinguishable. This is just like if someone steals your password and tries to log in to StackOverflow. To StackOverflow, the attacker and you are indistinguishable, since all they have to go on is the username and password.

You can do fancy things with the client as mentioned in other answers, such as tokens, time limits, etc., but an dedicated attacker would be able to mimic the actions of a legitimate client, and you wouldn't be able to tell them apart because they would both appear to be from valid IP addresses. For instance, in your last example, if I was an attacker looking to make API calls, I would spoof a legitimate IP address, get the signature, and use it to make an API call, just as a legitimate client would.

If your application is critical enough to deem this level of thought into security, you should at least think of implementing something like API tokens, public key encryption, or other authentication methods that are more secure than IP addresses to tell your clients apart from any attackers. Authentication by IP address (or other easily forged tokens like hostname or headers) simply won't cut it.

Answer 2

may be you could achieve this by using Same-origin policy

refer http://en.wikipedia.org/wiki/Same_origin_policy

Answer 3

If it's purely the same server, you can verify requests against 127.0.0.1 or localhost.

Otherwise the solution is probably at the network level, to have a separate private subnet that you can check against. It should be difficult for an attacker to spoof your subnet without being on your subnet.

Answer 4

Depending on your infrastructure @dragonx's answer might interest you most.

my 2c

You want to make sure that only if a client visits your website can use the api? Hmm does the bot, robot, crawler fall in the same category with the client then? Or am I wrong? This can be easily exploited in case you really want to secure it really.

I cannot believe I'm the only person with this requirement.

Maybe not, but as you can see you are prone to several attacks to your API and that can be a reason for someone not sharing your design and making security stricter with auth.

EDIT

Since we are talking about AJAX requests what does the IP part has to do with this? The IP will always be the Client's IP! So probably, you want a public API...

• I would Go with the tokens/session/cookie part.

• I 'd go with a generated token that lasts a little while and a flow described below.

• I'd go with a limiter per some time, like Github does. Eg 60 requests per hour per ip or more for registered users

To overcome the problem with the refreshing token I would just do this:

1. Client visits the site

   -> server generates API TOKEN INIT

   -> Client gets API TOKEN INIT which is valid only for starting 1 request.

2. Client makes AJAX Request to API

   -> Client uses API TOKEN INIT

   -> Server checks against API TOKEN INIT and limits

   -> Server accepts request

   -> Server passes back API TOKEN

   -> Client consumes response data and stores API TOKEN for further usage (Will be stored in browser memory via JS)

3. Client Starts Comm with the API for a limited amount of time or requests. Notice that you know also the init token date so you can use it to check against the 1st visit on the page.

The 1st token is generated via the server when the client visits. Then the client uses that token in order to obtain a real one, that lasts for some time or something else as of limitation. This makes someone actually visit the webpage and then he can access the API for a limit amount of time, requests perhaps etc.

This way you don't need refreshing.

Of course the above scenario could be simplified with only one token and a time limit as mentioned above.

Of course the above scenario is prone to advanced crawlers, etc since you have no authentication.

Of course a clever attacker can grab tokens from server and repeat the steps but, then you already had that that problem from start.

Some extra points

• As the comments provided please close writes to the API. You don't want to be a victim of DOS attacks with writes if you have doubts about your implementation(if not use auth) or for extra security
• The token scenario as described above can also become more complicated eg by constantly exchanging tokens

Just for reference GAE Cloud storage uses signed_urls for kind of the same purpose.

Hope it helps.

PS. regarding IP spoofing and Defense against spoofing attacks wikipedia says so packet's won't be returned to the attacker:

Some upper layer protocols provide their own defense against IP spoofing attacks. For example, Transmission Control Protocol (TCP) uses sequence numbers negotiated with the remote machine to ensure that arriving packets are part of an established connection. Since the attacker normally can't see any reply packets, the sequence number must be guessed in order to hijack the connection. The poor implementation in many older operating systems and network devices, however, means that TCP sequence numbers can be predicted.

Answer 5

As suggested by Venkatesh Bachu, Same Origin Policy and http://en.wikipedia.org/wiki/Cross-Origin_Resource_Sharing (CORS) could be used as a solution. In your API, you can check Origin header and respond accordingly. Need to check if Origin header can be modified by using extensions like tamper data. A determined hacker can still snoop by pointing browser to a local proxy server.

Answer 6

I guess you're a bit confused (or I am, please correct me). That your JS code is published on the same server as your API does not mean AJAX requests will come from your server. The clients download the JS from your server and execute it, which results in requests to your API sent from the clients, not from the same server.

Now if the above scenario correctly describes your case, what you are probably trying to do is to protect your API from bot scraping. The easiest protection is CAPTCHA, and you can find some more ideas on the Wiki page.

If you are concerned that other sites may make AJAX calls to your API to copy your site functionality, you shouldn't be--AJAX requests can only be sent to the same server as the page the JS is running on, unless it is JSONP.