How do I implement login in a RESTful web service? - web-services

I am building a web application with a services layer. The services layer is going to be built using a RESTful design. The thinking is that some time in the future we may build other applications (iPhone, Android, etc.) that use the same services layer as the web application. My question is this - how do I implement login? I think I am having trouble moving from a more traditional verb based design to a resource based design. If I was building this with SOAP I would probably have a method called Login. In REST I should have a resource. I am having difficulty understanding how I should construct my URI for a login. Should it be something like this:
http://myservice/{username}?p={password}
EDIT: The front end web application uses the traditional ASP.NET framework for authentication. However at some point in the authentication process I need to validate the supplied credentials. In a traditional web application I would do a database lookup. But in this scenario I am calling a service instead of doing a database lookup. So I need something in the service that will validate the supplied credentials. And in addition to validating the supplied credentials I probably also need some sort of information about the user after they have successfully authenticated - things like their full name, their ID, etc. I hope this makes the question clearer.
Or am I not thinking about this the right way? I feel like I am having difficulty describing my question correctly.
Corey

As S.Lott pointed out already, we have a two folded things here: Login and authentication
Authentication is out-of-scope here, as this is widely discussed and there is common agreement. However, what do we actually need for a client successfully authenticate itself against a RESTful web service? Right, some kind of token, let's call it access-token.
Client) So, all I need is an access-token, but how to get such RESTfully?
Server) Why not simply creating it?
Client) How comes?
Server) For me an access-token is nothing else than a resource. Thus, I'll create one for you in exchange for your username and password.
Thus, the server could offer the resource URL "/accesstokens", for POSTing the username and password to, returning the link to the newly created resource "/accesstokens/{accesstoken}".
Alternatively, you return a document containing the access-token and a href with the resource's link:
<access-token
id="{access token id goes here; e.g. GUID}"
href="/accesstokens/{id}"
/>
Most probably, you don't actually create the access-token as a subresource and thus, won't include its href in the response.
However, if you do so, the client could generate the link on its behalf or not? No!
Remember, truly RESTful web services link resources together in a way that the client can navigate itself without the need for generating any resource links.
The final question you probably have is if you should POST the username and password as a HTML form or as a document, e.g. XML or JSON - it depends... :-)

You don't "login". You "authenticate". World of difference.
You have lots of authentication alternatives.
HTTP Basic, Digest, NTLM and AWS S3 Authentication
HTTP Basic and Digest authentication. This uses the HTTP_AUTHORIZATION header. This is very nice, very simple. But can lead to a lot of traffic.
Username/Signature authentication. Sometimes called "ID and KEY" authentication. This can use a query string.
?username=this&signature=some-big-hex-digest
This is what places like Amazon use. The username is the "id". The "key" is a digest, similar to the one used for HTTP Digest authentication. Both sides have to agree on the digest to proceed.
Some kind of cookie-based authentication. OpenAM, for example, can be configured as an agent to authenticate and provide a cookie that your RESTful web server can then use. The client would authenticate first, and then provide the cookie with each RESTful request.

Great question, well posed. I really like Patrick's answer. I use something like
-/users/{username}/loginsession
With POST and GET being handled. So I post a new login session with credentials and I can then view the current session as a resource via the GET.
The resource is a login session, and that may have an access token or auth code, expiry, etc.
Oddly enough, my MVC caller must itself present a key/bearer token via a header to prove that it has the right to try and create new login sessions since the MVC site is a client of the API.
Edit
I think some other answers and comments here are solving the issue with an out-of-band shared secret and just authenticating with a header. That's fine in many situations or for service-to-service calls.
The other solution is to flow a token, OAuth or JWT or otherwise, which means the "login" has already taken place by another process, probably a normal login UI in a browser which is based around a form POST.
My answer is for the service that sits behind that UI, assuming you want login and auth and user management placed in a REST service and not in the site MVC code. It IS the user login service.
It also allows other services to "login" and get an expiring token, instead of using a pre-shared key, as well as test scripts in a CLI or Postman.

Since quite a bit has changed since 2011...
If you're open to using a 3rd party tool, and slightly deviating from REST slightly for the web UI, consider http://shiro.apache.org.
Shiro basically gives you a servlet filter purposed for authentication as well as authorization. You can utilize all of the login methods listed by #S.Lott, including a simple form based authentication.
Filter the rest URLs that require authentication, and Shiro will do the rest.
I'm currently using this in my own project and it has worked pretty well for me thus far.
Here's something else people may be interested in.
https://github.com/PE-INTERNATIONAL/shiro-jersey#readme

The first thing to understand about REST is that its a Token based resource access.Unlike traditional ways, access is granted based on token validation. In simple words if you have right token, you can access resources.Now there is lot of whole other stuff for token creation and manipulation.
For your first question, you can design a Restfull API. Credentials(Username and password) will be passed to your service layer.Service layer then validates these credentials and grant a token.Credentials can be either simple username/password or can be SSL certificates. SSL certificates uses the OAUTH protocol and are more secure.
You can design your URI like this-
URI for token request-> http://myservice/some-directory/token?
(You can pass Credentilals in this URI for Token)
To use this token for resource access you can add this [Authorization:Bearer (token)] to your http header.
This token can be utilized by the customer to access different component of your service layer. You can also change the expiry period of this token to prevent misuse.
For your second question one thing you can do is that you grant different token to access different resource components of your service layer. For this you can specify resource parameter in your token, and grand permission based on this field.
You can also follow these links for more information-
http://www.codeproject.com/Articles/687647/Detailed-Tutorial-for-Building-ASP-NET-WebAPI-REST
http://www.vinaysahni.com/best-practices-for-a-pragmatic-restful-api

I have faced the same problem before. Login does not translate nicely to resource based design.
The way I usually handle it is by having Login resource and passing username and password on the parameter string, basically doing
GET on http://myservice/login?u={username}&p={password}
The response is some kind of session or auth string that can then be passed to other APIs for validation.
An alternative to doing GET on the login resource is doing a POST, REST purists will probably not like me now :), and passing in the creds in the body. The response would be the same.

Related

Rest API authorization of signed and unencrypted JWT best practices

I just want to make sure I've got the overall idea down and don't create an implementation that violates basic security best practices. Can somebody please check my understanding?
As I understand it, a user can log in to my application and the authentication server REST API can return a JWT that is signed, but NOT encrypted. Inside that token I can have claims inside the payload that my client application can access, such as features the user can use on the application. That way my client side website can change functionality based on the user privileges and roles. The JWT claims in the payload are NOT sensitive. They will be strings representing categories for images or documents, things like that.
When the user wants to get additional content (like a document, image, or video) from other REST API endpoints, they submit the JWT along with the GET request. My API can then verify the signature of the JWT and grant API access if appropriate.
This last part is what I'm most unsure about. My intent is to use another authorization server API endpoint which takes the JWT in a POST request and returns a simple "valid/invalid" response. My thought is that my Content Delivery Network (CDN) can use this API to verify that the JWT in possession is validly signed. I believe (and maybe here is where I'm goofing up) that the authorization server API can be publicly accessible to ease use by my other microservices. This seems fine because I'm just giving a boolean pass/fail on the validity of the token so I don't see any need to hide or obfuscate the API. I question this because I know AWS has backend stuff to validate and authorize for API calls but I like the simplicity of just using REST APIs for everything for my first implementation; to maintain simplicity.
So in summary:
1.) Signed, unencrypted JWT with non-sensitive user roles/privileges.
2.) Unencrypted so client side webpage can selectively render content based on user.
3.) Public authorization API that anybody could technically use so that my CDN (and other microservices) can validate JWTs.
Any major issue with this approach? Have I committed any technical sins?
Thank you so much in advance for your time on this matter.
Okay, I think I've sorted this out myself after finding a great video tutorial on this stuff. Below is the video I watched:
https://www.youtube.com/watch?v=_XbXkVdoG_0
I had some misconceptions and this video sorted them out. It appears that what I described in my question is precisely how JWT should be used.

Security about a simple REST web service

Here is my little API with two URL :
/api/location/list -> GET
/api/location/detail -> GET
I'm looking for a process to secure this service with authentication. For now, it can be accessed by only one user (me).
I think oAuth is too complex in my case and I found this resource for designing a simple API.
I understand the principle of private/public key and HMAC but I have a big concern about this :
Say my webservice is consumed by an ajax request with GET verb. I have something like /api/location/list?apikkey=userid&hash=abcde.
A end user can easily sniffed the network during the request (via a simple chrome console), capture full url and access directly to the service multiple times (I think it's a case of replay attacks).
Differents resources talk about timestamp or nonce to make a request unique but I'm a bit lost with implementation.
Any ideas ?
You can try JWToken auth specs, simpler than Oauth, but avoid authorization data as url parameter if possible and use Header's request instead.
If needed consider also ssl encryption at tcp level.
Perhaps you could try to use a token-based approach for security, as described in this blog post:
Implementing authentication with tokens for RESTful applications - https://templth.wordpress.com/2015/01/05/implementing-authentication-with-tokens-for-restful-applications/
The idea is to authenticate to an authentication resource (that can be part of your application) to get temporary token that can be refreshed with a refresh token when expired.
With the use of HTTPS, it seems to be appropriate.
I think that it depends on the security level you expect. Signature-based authentication (the AWS approach) is great but is a bit complex to implement by hand.
Hope it helps you,
Thierry

Advice how to implement a simple user login and authenication

We are in the process of building a simple Android application together with a simple back-end web server to allow the user to get some information form the server.
We need to login the user, to make sure he is authorized to view the data, but apart form that I do not think we have particular security concerns.
I need some advice on how we can implement the server to keep things as simple as possible.
For example, we could use something like this to make sure the user is authorized to see the data:
http://ourwebservice/user/password/viewsuchandsuchdata
Is that a good way of doing things?
Do you have any suggestions or comments?
There are many ways to secure web-services.
The simplest is possible "Basic Auth" (http://en.wikipedia.org/wiki/Basic_access_authentication). On every request, you send the user credentials in the "Authorization" HTTP header concatenated with ":" and base 64 encoded. To keep it safe, you need to make sure the connection to your web-server is using SSL (HTTPS), otherwise the user password could be intercepted.
Another "newer" solution is OAuth2, and in your case the "Resource Owner Credentials" flow. Instead of passing the user credentials on every request, you use them once to "exchange" them for a short-lived access token issued by your server. Then on any request to the web-service you pass that access token in lieu of authentication. The server must then verify that the token is valid and find out for which user it was issued. For more info see this article: http://aaronparecki.com/articles/2012/07/29/1/oauth2-simplified.
There are potentially many more "custom" ways of doing authentication...
Going the OAuth2 flow is probably more difficult but there are lots of open-source libraries out there to help you build a OAuth2 provider (http://oauth.net/2/). The advantage is that you don't have to store the user password on the device, which is safer (the less you touch passwords, the better).

Microsoft sync framework Authentication

I'm very novice when it comes to web applications and ASP.
Recently, I've been experimenting with the Microsoft Sync Toolkit to synchronize databases over a OData web service.
The obvious question here is: Once the service is set up and published - so it is open for anyone knowing the URL - how to prevent unauthorized users from accessing this service.
Please note: Basic authentication of forms authentication - as far my little web development knowledge reaches - doesn't seem to be appropriate for this task, as it's not a web page that the client is trying to reach - where the page can display / or re-direct a logon request - it's a service that we are accessing here.
To make things more difficult, for the client-side syncing I'm using a 3rd party library/sync-provider that only accepts a URL for the service. So, there's no way (I think) I can experiment with incorporating login credentials inside a request header etc.
I assume the best bet would be embedding the login credentials inside the URL and use that for the 3rd party library.
Can somebody please direct me how to to set up such thing on the server? I would prefer to have somehow somewhere in the server-side code a place where I can check for the credentials and based upon it to proceed or abort (return 401) the service request.
I could not find any place where to hook such code into the sync service. Although somebody in MSDN suggested to handle the _OnBeginSyncRequest event, there is no way to access the web-request header from within that method.
Is there by-any-chance a global object accessible from everywhere from which I can access the request header? Could anyone please help with this?
And last, I would prefer a plain User / Password string pair. It should not necessarily (or rather not) have anything to do with windows or directory accounts. I would prefer in my code to simple check against plain strings, such if(userStr == "Authenticated user" && passwordStr == "Correct Password").
if you are using SOAP web service, you can use WS-Security usernametoken which adds your user name and password to the request header, otherwise you can add username and password as parameters in your webservice and then simply validate it on the server side. i.e.
instead of
bool SyncData(datatable)
it becomes
bool SyncData(datatable, username, password)
note for web service you will authenticate per call, if you want to do it per session, you need first login with username password, retrieves a token than on each subsequent call your service with the token.
You would also use SSL to secure the channel so username and password aren't transmitted as plain text.

Securing REST API without reinventing the wheel

When designing REST API is it common to authenticate a user first?
The typical use case I am looking for is:
User wants to get data. Sure cool we like to share! Get a public API key and read away!
User wants to store/update data... woah wait up! who are you, can you do this?
I would like to build it once and allow say a web-app, an android application or an iPhone application to use it.
A REST API appears to be a logical choice with requirements like this
To illustrate my question I'll use a simple example.
I have an item in a database, which has a rating attribute (integer 1 to 5).
If I understand REST correctly I would implement a GET request using the language of my choice that returns csv, xml or json like this:
http://example.com/product/getrating/{id}/
Say we pick JSON we return:
{
"id": "1",
"name": "widget1",
"attributes": { "rating": {"type":"int", "value":4} }
}
This is fine for public facing APIs. I get that part.
Where I have tons of question is how do I combine this with a security model? I'm used to web-app security where I have a session state identifying my user at all time so I can control what they can do no matter what they decide to send me. As I understand it this isn't RESTful so would be a bad solution in this case.
I'll try to use another example using the same item/rating.
If user "JOE" wants to add a rating to an item
This could be done using:
http://example.com/product/addrating/{id}/{givenRating}/
At this point I want to store the data saying that "JOE" gave product {id} a rating of {givenRating}.
Question: How do I know the request came from "JOE" and not "BOB".
Furthermore, what if it was for more sensible data like a user's phone number?
What I've got so far is:
1) Use the built-in feature of HTTP to authenticate at every request, either plain HTTP or HTTPS.
This means that every request now take the form of:
https://joe:joepassword#example.com/product/addrating/{id}/{givenRating}/
2) Use an approach like Amazon's S3 with private and public key: http://www.thebuzzmedia.com/designing-a-secure-rest-api-without-oauth-authentication/
3) Use a cookie anyway and break the stateless part of REST.
The second approach appears better to me, but I am left wondering do I really have to re-invent this whole thing? Hashing, storing, generating the keys, etc all by myself?
This sounds a lot like using session in a typical web application and rewriting the entire stack yourself, which usually to me mean "You're doing it wrong" especially when dealing with security.
EDIT: I guess I should have mentioned OAuth as well.
Edit 5 years later
Use OAuth2!
Previous version
No, there is absolutely no need to use a cookie. It's not half as secure as HTTP Digest, OAuth or Amazon's AWS (which is not hard to copy).
The way you should look at a cookie is that it's an authentication token as much as Basic/Digest/OAuth/whichever would be, but less appropriate.
However, I don't feel using a cookie goes against RESTful principles per se, as long as the contents of the session cookie does not influence the contents of the resource you're returning from the server.
Cookies are evil, stop using them.
Don't worry about being "RESTful", worry about security. Here's how I do it:
Step 1: User hits authentication service with credentials.
Step 2: If credentials check out, return a fingerprint, session id, etc..., and pop them into shared memory for quick retrieval later or use a database if you don't mind adding a few milliseconds to your web service turnaround time.
Step 3: Add an entry point call to the top of every web service script that validates the fingerprint and session id for every web service request.
Step 4: If the fingerprint and session id aren't valid or have timed out redirect to authentication.
READ THIS:
RESTful Authentication
Edit 3 years later
I completely agree with Evert, use OAuth2 with HTTPS, and don't reinvent the wheel! :-)
By simpler REST APIs - not meant for 3rd party clients - JSON Web Tokens can be good as well.
Previous version
Use a cookie anyway and break the stateless part of REST.
Don't use sessions, with sessions your REST service won't be well scalable... There are 2 states here: application state (or client state or session s) and resource state. Application state contains the session data and it is maintained by the REST client. Resource state contains the resource properties and relations and is maintained by the REST service. You can decide very easy whether a particular variable is part of the application state or the resource state. If the amount of data increases with the number of active sessions, then it belongs to the application state. So for example user identity by the current session belongs to the application state, but the list of the users or user permissions belongs to the resource state.
So the REST client should store the identification factors and send them with every request. Don't confuse the REST client with the HTTP client. They are not the same. REST client can be on the server side too if it uses curl, or it can create for example a server side http only cookie which it can share with the REST service via CORS. The only thing what matters that the REST service has to authenticate by every request, so you have to send the credentials (username, password) with every request.
If you write a client side REST client, then this can be done with SSL + HTTP auth. In that case you can create a credentials -> (identity, permissions) cache on the server to make authentication faster. Be aware of that if you clear that cache, and the users send the same request, they will get the same response, just it will take a bit longer. You can compare this with sessions: if you clear the session store, then users will get a status: 401 unauthorized response...
If you write a server side REST client and you send identification factors to the REST service via curl, then you have 2 choices. You can use http auth as well, or you can use a session manager in your REST client but not in the REST service.
If somebody untrusted writes your REST client, then you have to write an application to authenticate the users and to give them the availability to decide whether they want to grant permissions to different clients or not. Oauth is an already existing solution for that. Oauth1 is more secure, oauth2 is less secure but simpler, and I guess there are several other solution for this problem... You don't have to reinvent this. There are complete authentication and authorization solutions using oauth, for example: the wso identity server.
Cookies are not necessarily bad. You can use them in a RESTful way until they hold client state and the service holds resource state only. For example you can store the cart or the preferred pagination settings in cookies...