I'm developing the restful web app that using some popular web framework on the backend, say (rails, sinatra, flask, express.js). Ideally, I want to develop client side with Backbone.js. How do I let only my javascript client side interact with those API calls? I don't want those API calls to be public and be called by curl or simply by entering the link on browser.
As a first principle, if your API is consumed by your JS client, you have to assume, that it is public: A simple JS debugger puts an attacker into a position, where he can send a byte-for-byte identical request from a tool of his choice.
That said, if I read your question correctly, this is not, what you want to avoid: What you really don't want to happen is, that your API is consumed (on a regular basis) without your JS client being involved. Here are some ideas on how to if not enforce, then at least encourage using your client:
I am sure, your API has some sort of authentication field (e.g. Hash computed on the client). If not, take a look at This SO question. Make sure you use a salt (or even API key) that is given to your JS client on a session basis (a.o.t. hardcoded). This way, an unauthorized consumer of your API is forced into much more work.
On loading the JS client, remember some HTTP headers (user agent comes to mind) and the IP address and ask for reauthentication if they change, employing blacklists for the usual suspects. This forces an attacker to do his homework more thoroughly again.
On the server side, remember the last few API calls, and before allowing another one, check if business logic allows for the new one right now: This denies an attacker the ability to concentrate many of his sessions into one session with your server: In combination with the other measures, this will make an abuser easy detectable.
I might not have said that with the necessary clarity: I consider it impossible to make it completely impossible for an abuser to consume your service, but you can make it so hard, it might not be worth the hassle.
You should implement some sort of authentication system. One good way to handle this is to define some expected header variables. For example, you can have an auth/login API call that returns a session token. Subsequent calls to your API will expect a session token to be set in an HTTP header variable with a specific name like 'your-api-token'.
Alternatively many systems create access tokens or keys that are expected (like youtube, facebook or twitter) using some sort of api account system. In those cases, your client would have to store these in some manner in the client.
Then it's simply a matter of adding a check for the session into your REST framework and throwing an exception. If at all possible the status code (to be restful) would be a 401 error.
There's an open standard now called "JSON Web Token",
see https://jwt.io/ & https://en.wikipedia.org/wiki/JSON_Web_Token
JSON Web Token (JWT) is a JSON-based open standard (RFC 7519) for
creating tokens that assert some number of claims. For example, a
server could generate a token that has the claim "logged in as admin"
and provide that to a client. The client could then use that token to
prove that they are logged in as admin. The tokens are signed by the
server's key, so the server is able to verify that the token is
legitimate. The tokens are designed to be compact, URL-safe and usable
especially in web browser single sign-on (SSO) context. JWT claims can
be typically used to pass identity of authenticated users between an
identity provider and a service provider, or any other type of claims
as required by business processes.[1][2] The tokens can also be
authenticated and encrypted.[3][4]
Set a SESSION var on the server when the client first loads your index.html (or backbone.js etc.)
Check this var on the server-side on every API call.
P.S. this is not a "security" solution!!! This is just to ease the load on your server so people don't abuse it or "hotlink" your API from other websites and apps.
Excuse me #MarkAmery and Eugene, but that is incorrect.
Your js+html (client) app running in the browser CAN be set up to exclude unauthorized direct calls to the API as follows:
First step: Set up the API to require authentication. The client must first authenticate itself via the server (or some other security server) for example asking the human user to provide the correct password.
Before authentication the calls to the API are not accepted.
During authentication a "token" is returned.
After authentication only API calls with the authentication "token" will be accepted.
Of course at this stage only authorized users who have the password can access the API, although if they are programmers debugging the app, they can access it directly for testing purposes.
Second step: Now set up an extra security API, that is to be called within a short limit of time after the client js+html app was initially requested from the server. This "callback" will tell the server that the client was downloaded successfully. Restrict your REST API calls to work only if the client was requested recently and successfully.
Now in order to use your API they must first download the client and actually run it in a browser. Only after successfully receiving the callback, and then user entry within a short frame of time, will the API accept calls.
So you do not have to worry that this may be an unauthorized user without credentials.
(The title of the question, 'How do I secure REST API calls', and from most of what you say, that is your major concern, and not the literal question of HOW your API is called, but rather BY WHOM, correct?)
Here's what I do:
Secure the API with an HTTP Header with calls such as X-APITOKEN:
Use session variables in PHP. Have a login system in place and save the user token in session variables.
Call JS code with Ajax to PHP and use the session variable with curl to call the API. That way, if the session variable is not set, it won't call and the PHP code contains the Access Token to the API.
I'm a back-end developer who has to create the front-end too in the current project!
I'm using reactJs and I know that for authorizing users I should get an api_token from my back-end API then use the api_token in the next requests! so I should store the api_token (actually somewhere into the client's browser)! but where should I store it to be secure?
the first answer came to my mind was 'Local Storage' ! but I've read this article: Don't store tokens in local storage
I've searched and found #auth0/auth0-spa-js, but I don't know can I trust this package (and similar) or not?
these are the way's which I've found! but what's the correct way to store sensitive data like this?
The Auth Flow should be on the Web should be
Send User/Password Details to server
Server validates and returns encrypted token with some details inside and that's stored as a HTTP Cookie
Setup Protected endpoints so only users with token can access them
Security : HTTP Cookie only means that the browser doesn't have access to it on the client, only the server. But someone can simply just Copy Paste it into their cookies which if you're worried about or working on sensitive stuff, you will need to implement additional security measures such as the ones mentioned.
Generally, Device Management is not a web concern but you can also some validation on the token for things like make the token expire in 5 minutes, or expire on session end, DeviceId, Browser Id, IP address, send them an email that a new unknown IP has logged in, etc.
Never store private tokens in your frontend code
You should create a server that can only be accessed from a particular url (the url of your app). This server can have the secret tokens that you need to make calls. The that server can forward requests to the services you will use that need private tokens.
I would like to use Squid as a proxy for a Google App Engine based application (as we need to have a static outgoing ip, and GAE does not support that).
Also, I want to keep using urlfetch, so as not to do too much changes in the existing code.
The solution I want to implement is to install a Squid proxy, and direct all the urlfetch requests to this proxy by using the proxy url in the fetch request, and add some custom http header that will contain the final destination url.
Then, I want to configure Squid to take this custom header parameter from the request, and use it as the request url.
How do I configure this last part on Squid ?
(There may be many different urls, so configuring a separate port for each destination url is not an option).
I'd like to use the URL fetch service for app engine (java). I'm just sending a POST to one of my own servers from a servlet.
AppEngine -> post-to: https://www.myotherserver.com/scripts/log.php
I'm reading the url fetch doc:
Secure Connections and HTTPS
An app can fetch a URL with the HTTPS method to connect to secure servers. Request and response data are transmitted over the network in encrypted form.
The proxy the URL Fetch service uses cannot authenticate the host it is contacting. Because there is no certificate trust chain, the proxy accepts all certificates, including self-signed certificates. The proxy server cannot detect "man in the middle" attacks between App Engine and the remote host when using HTTPS.
I don't understand - the first paragraph makesit sound like everything that goes from the servlet on app engine, to my php script is going to be secure if I use https. The second paragraph makes it sound like the opposite, that it won't actually be secure. Which is it?
Thanks
There are two things HTTPS does for you. One is to encrypt your data so that as it travels over the internet, through various routers and switches, no one can peek at it. The second thing HTTPS does is authenticate that you are actually talking to a certain server. This is the part App Engine can't do. If you were trying to connect to www.myotherserver.com, it is possible that some bad guy named bob could intercept your connection, and pretend to be www.myotherserver.com. Everything you sent to bob would be encrypted on it's way to bob, but bob himself would be able to get the unencrypted data.
In your case, it sounds like you control both the sending server and the destination server, so you could encrypt your data with a shared secret to protect against this possibility.
The UrlFetch through https has been fixed allowing certificate server validation.
validate_certificate
A value of True instructs the application to send a request to the
server only if the certificate is
valid and signed by a trusted CA, and
also includes a hostname that matches
the certificate. A value of False
instructs the application to perform
no certificate validation. A value of
None defaults to the underlying
implementation of URL Fetch. The
underlying implementation currently
defaults to False, but will default to
True in the near future.
As you may well know, it is required to host an access policy
(clientaccesspolicy.xml) on your web server if you want SL apps
to perform HTTP requests, or you need to host an access server
on port 943 for socket connections.
My app makes many short requests and latency is important. I want
to know if this access policy file is accessed once for every
new HTTP request or is it accessed for the first request and have
its result cached on the client. It would be quite costly for me
to have two web requests (one for the policy, one for the HTTP GET)
for each HTTP request I create.
One easy way to test this is to use Fiddler and watch for requests to the policy file. The documentation also specifies that the cross-domain policy file is requested only once per application session. This means that the runtime will only request it once and store the result in memory for the silverlight session.