Is there a "REST-way" by which a client of a REST-API can indicate whether it is interested in getting a resource representation of the created resource in the POST response or whether it is just interested in HTTP response code (i.e. 201 on success) and location header?
I was thinking on using the Accept header. If the client adds a media type to this header that is supported by the API, the representation will be returned. Otherwise, it will just get a HTTP Created and the location header.
Context: The API will have to types of clients. A Web-UI client, that wants the representation in the response to save a network round-trip. And backend-service clients that will create resources at high rate in fire-and-forget manner. They're only interested in response code and resource URI.
There is a HTTP header:
Prefer: return=representation
The server can signal that it respected the header by returning:
Preference-Applied: return=representation
https://www.rfc-editor.org/rfc/rfc7240
The problem i am facing is that clicking on F12 on Chrome Browser , i could see all the Rest Calls which are made to fetch the data
For example , one of the REST API call is
(When clicked on the above link , it fetches the data )
This is my front code consists of Jquery
function displaymarketupdates() {
var updatedon = "";
var html = '';
var t = "",
$.ajax({
type: "GET",
url: e,
crossDomain: !0,
dataType: "json",
timeout: 17e3,
async: !0,
cacheResults: !1,
cache: !1,
contentType: "application/json",
charset: "utf-8",
beforeSend: function() {
$(".loadingWrapformarketupdates").show()
},
complete: function() {
$(".loadingWrapformarketupdates").hide()
},
success: function(response) {
},
error: function(t, e, a) {
$(".loadingWrapformarketupdates").hide()
}
}).done(function() {
})
}
And this is my service
#Path("/fetchallvalues")
public class FetchAllValues {
public FetchAllValues() {}
private final static Logger logger = Logger.getLogger(FetchAllValues.class);
#GET#Produces("text/plain")
public Response Fetch_all_values() {
PreparedStatement fetch_all_pstmt = null;
ResultSet fetch_all_Rset = null;
Connection dbConnection = null;
ResponseBuilder builder = Response.status(Status.NOT_FOUND);
final JSONArray fetch_array = new JSONArray();
final String inputsql = "select * from all_values";
try {
dbConnection = DBConnection.getDBConnection();
fetch_all_pstmt = dbConnection.prepareStatement(inputsql);
fetch_all_Rset = fetch_all_pstmt.executeQuery();
while (fetch_all_Rset.next()) {
====
}
Response.status(Status.OK);
builder = Response.ok(fetch_array.toString());
} catch (Exception e) {
e.printStackTrace();
logger.error("Error description", e);
} finally {
try {
DBConnection.close(fetch_all_pstmt, fetch_all_Rset);
} catch (Exception e) {
logger.error("Error description", e);
}
try {
DBConnection.close(dbConnection);
} catch (Exception e) {
logger.error("Error description", e);
}
}
return builder.build();
}
}
Could you please let me know how to secure the REST CALL in this case
You cannot hide an URL from a Browser's network monitoring. It is meant to be displayed so that it can be inferred that what is happening when you hit a button or click something.
Securing a REST Jersey call is a totally different thing. That means you do not want people to see your data that you are going to pass. As correctly mentioned by Martingreber that if you call this URL on HTTPS that may help you encrypt data that you send across the servers. Or securing a REST call actually means you provide some kind of authentication to it . Like Basic , Hashing like MD5, Token based Authentication like JWT.
The only thing that you can do to hide explicit details from your browser that runs your JavaScript is minify your script . But still your URL remains exposed as many times as it is called by someone who fiddles with the F12 key on Chrome to see what's going on. One more thing can be if you are concerned about your main service call, and don't want to expose that , then just PROXY it using some service, which you are already doing . But by no means, you can avoid your URL being getting displayed, when someone calls it.
In your case fetchAllValues service is fetching the data and exposing it to anybody on the web who clicks it, but that can be prevented if you authenticate the service, like the minute i click that URL, it asks me for a password! Then i cannot access it. A very simple way to authenticate this service would to call a Filter or an Interceptor just before the request to ask for username and password like credentials.
I hope you got the point. Hope this helps :)
You will always be able to see the URL that is being processed. Still, you could obfuscate the Service Endpoint to hide the purpose of the service itself, e.g. #Path("/XYZ")instead of #Path("fetchallvalues")
If you want to hide the data that is being transmitted between the client and the server, so noone can read it, simply use https. Depending on your webserver (Jetty, Tomcat) you will have to configure it differently, still you will need a ssl certificate for your domain, which you can get here for example: https://letsencrypt.org
If you want to secure your webservice, so it can't be used by anyone, but only by specific users, you might want to give Spring Security a try: User authentication on a Jersey REST service
This is a problem that needs some smart hacks to fix it.
In the hyperlinked stackoverflow page, you will get an example of how to make a SOAP request from client side JavaScript.
SOAP request from JavaScript
Now here's the plan:
In the server side, we have a random number generator, which generates a random number in short intervals, say 5 minutes.
The random number generator will be exposed as a SOAP service and it will produce the random number generated.
From the client side, we will invoke the SOAP random generator service (refering to the stackoverflow page mentioned above) and get the generated random number as the response. We will invoke the service from a JS function which will be fired when your page is loaded (onLoad). So, now we have the random number at the client side.
Then, we pass the random number as a path param in the GET request URL of the REST call and fire the GET request.
In the server side, once the Rest GET request is received, we check if the number received as path param is the same number that is generated in the server side.
If the numbers match, then we give the required response, else do not send the response.
Here we are trying to introduce an unique key, which is the random number generated at the server side. This unique key, when passed as the path param of the Rest GET request URL, serves as an identity of the origin of the Rest GET call. For someone who wants to invoke the Rest Api by referring to the Network Tab of the Chrome Dev console, will not get the unique key for a long time ( as it is refreshed/regenerated after every 5 minutes). Thus the hacker will not be able to use the Rest Api for a long duration. Also, since we are transporting the unique key (the random number) from the server to client side using SOAP, it is not possible for the hacker to get it from the Chrome's developer console.
Hope this approach helps!
Unfortunately, there is nothing you can do to prevent the client from inspecting the requested URL. But you always can require credentials to access your API endpoints.
Authentication in REST APIs
In REST applications, each request from the client to the server must contain all the necessary information to be understood by the server. With it, you are not depending on any session context stored on the server and you do not break the REST stateless constraint, defined by Roy Thomas Fielding in his dissertation:
5.1.3 Stateless
[...] communication must be stateless in nature [...], such that each request from client to server must contain all of the information necessary to understand the request, and cannot take advantage of any stored context on the server. Session state is therefore kept entirely on the client. [...]
When accessing protected resources (endpoints that require authentication), every request must contain all necessary data to be properly authenticated/authorized. And authentication data should belong to the standard HTTP Authorization header. From the RFC 7235:
4.2. Authorization
The Authorization header field allows a user agent to authenticate
itself with an origin server -- usually, but not necessarily, after
receiving a 401 (Unauthorized) response. Its value consists of
credentials containing the authentication information of the user
agent for the realm of the resource being requested. [...]
In other words, the authentication will be performed for each request.
Basic authentication
The Basic Authentication scheme, defined in the RFC 7617, is a good start for securing a REST API:
2. The 'Basic' Authentication Scheme
The Basic authentication scheme is based on the model that the client
needs to authenticate itself with a user-id and a password for each
protection space ("realm"). [...] The server will service the request only if it can validate
the user-id and password for the protection space applying to the
requested resource.
[...]
To receive authorization, the client
obtains the user-id and password from the user,
constructs the user-pass by concatenating the user-id, a single
colon (":") character, and the password,
encodes the user-pass into an octet sequence,
and obtains the basic-credentials by encoding this octet sequence
using Base64 into a sequence of US-ASCII
characters.
[...]
If the user agent wishes to send the user-id "Aladdin" and password
"open sesame", it would use the following header field:
Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==
[...]
Token-based authentication
If you don't want to send the username and the password over the wire for every request, you could consider using a token-based authentication. In this approach, you exchange your hard credentials (username and password) for a token which the client must send to the server in each request:
The client sends their credentials (username and password) to the server.
The server authenticates the credentials and generates a token.
The server stores the previously generated token in some storage along with the user identifier and an expiration date.
The server sends the generated token to the client.
In every request, the client sends the token to the server.
The server, in each request, extracts the token from the incoming request. With the token, the server looks up the user details to perform authentication and authorization.
If the token is valid, the server accepts the request.
If the token is invalid, the server refuses the request.
The server can provide an endpoint to refresh tokens.
Again, the authentication must be performed for every request.
The token can be opaque (which reveals no details other than the value itself, like a random string) or can be self-contained (like JSON Web Token).
Random String: A token can be issued by generating a random string and persisting it to a database with an expiration date and with a user identifier associated to it.
JSON Web Token (JWT): Defined by the RFC 7519, it's a standard method for representing claims securely between two parties. JWT is a self-contained token and enables you to store a user identifier, an expiration date and whatever you want (but don't store passwords) in a payload, which is a JSON encoded as Base64. The payload can be read by the client and the integrity of the token can be easily checked by verifying its signature on the server. You won't need to persist JWT tokens if you don't need to track them. Althought, by persisting the tokens, you will have the possibility of invalidating and revoking the access of them. To find some great resources to work with JWT, have a look at http://jwt.io.
In a token-based authentication, tokens are your credentials. So the tokens should be sent to the server in the standard HTTP Authorization header as described above.
Once you are using Jersey, you could have a look at this answer for more details on how to implement a token-based authentication in Jersey.
HTTPS
When sending sensitive data over the wire, your best friend is HTTPS and it protects your application against the man-in-the-middle attack.
To use HTTPS, you need a certificate issued by a certificate authority such as Let’s Encrypt, that claims to be a free, automated, and open certificate authority.
What is the correct fallback if Content-Negotiation does not find a reasonable result due to a non 2xx status code? For example:
A client wants to download a PDF and sends following header Accept: application/pdf. Due to insufficient privileges the server would return a 403 Forbidden. You might want to explain the reason in more detail but it does not make much sense to return a PDF. How would you deal with that?
Should the server return an empty body? Should he ignore the Accept header and send some other representation like text/plain. Or is it the job of the client to provide alternatives per Accept: application/pdf, text/plain, */*.
Obviously if the user does not have permission to access the resource, there is no real alternative what a server can do. The server can however respond with content (even in an error case) which describes the error in more detail, if that response can be made using a media-type accepted by the client. The client should provide an Accept: header that describes all the media-types it can parse. So an automatic client would be able to do:
Accept: application/pdf, application/vnd.myapi.error
If content-negotiation fails, the returned code should be 406 Not Acceptable. The server can produce this if it can not provide any answer which would be acceptable to the client.
However, the specification states that the server may actually return an answer not explicitly acceptable by the client if it wants to, it is up to the client, to inspect the response headers to see what media-type the answer is.
Source: https://www.rfc-editor.org/rfc/rfc7231#section-3.4.1
If I want to return a status code of 303 See Other when a client POSTs data that already exists, am I allowed to return that data in the content (body) of the response (in addition to setting Location), or must the client then GET the Location?
I would like to avoid requiring the client HTTP to make two HTTP calls if at all possible.
Idiomatically, the client should retrieve the data with a GET request.
Ok, I'm confused. I'm trying to send back the magic headers from my server that will prevent a client from hitting the server again until a resource is stale.
I understand how ETag or Last-Modified works (Validation) - the client will ALWAYS still hit the server, and the server needs to validate the date or etag against the current value to know whether to bother serving up a new one.
Cache-Control and Expires, however, I don't think I understand. I've set the following:
Cache-Control: max-age=86400, must-revalidate
No matter what I do, my client (my browser, curl, NSURLConnection) always hits the server again on the second request. Is this a client thing? What headers should I send back to get the client to use it's private cache for a certain length of time?
As Nathan hints at in his answer, clients can issue a subsequent request with an If-Modified-Since header to determine whether or not their cache is stale. If the client receives a 304 Not Modified response, it will serve the content out of the local cache.
According to RFC 2616 (the HTTP 1.1 specification), the presence of must-revalidate within the Cache-control header forces clients to re-check their cache's status with the originating server prior to serving out of the cache.
For future reference - Mark Nottingham has written a great guide to HTTP caching:
http://www.mnot.net/cache_docs/#CACHE-CONTROL
The server needs to check the If-Modified-Since header and return a 304 not modified header if it wants the browser to keep caching.