There is a lot of information on the web about OAuth 2, its different types of flows and where/how to use them. I find that most of these resources discuss authenticating a user for an application, but I am struggling to understand what the best/correct approach would be when consuming third party APIs (i.e. when our own API is the "middleman" between a user and their data in a third party API).
With the help of an example scenario and some diagrams, I would be really grateful for advice/opinions on how I should properly implement integration with third party APIs and what the pros & cons of each approach are.
Starting point
As a starting point, suppose we have a web app, structured as follows:
Frontend - SPA (Angular), hosted with AWS S3 + Cloudfront
Backend - Node, running as stateless AWS lambda functions with AWS API Gateway
Auth0 for handling auth/signin etc. The frontend uses an Implicit OAuth2 flow to obtain access_tokens, which are stored in local storage and included as a header in all requests to the backend.
Potentially also native mobile app(s), consuming the same backend API.
Goal
Now suppose that we wish to add integration with Google Sheets. The new feature would allow users to use their own Google Sheets (i.e. stored in their own Google account) as a data source, with the app having read&write access to the sheet. There may be other integrations in the future, so I am assuming that other APIs would require a similar process.
Problem statement
In addition to the existing OAuth process (which allows users to sign in to the "MyApp" frontend and communicate with the "MyApp API"), there needs to be an additional OAuth process for users to connect MyApp to the third party Google Sheets API.
The documentation has two Quickstart examples, but neither seems to quite fit my needs:
Browser - https://developers.google.com/sheets/api/quickstart/js
Node.js (console app) - https://developers.google.com/sheets/api/quickstart/nodejs
The data from the third-party (Google) API is one of potentially several integration points, so intuitively it seems more logical (and more secure) that all communication with the Google Sheets API should happen in the MyApp API, and not on the frontend/client side. The MyApp API would fetch data, process/manipulate/format it in some way and then present it for display in the frontend or mobile apps.
We require access to each user's own data, so the Client Credentials flow is not suitable. I am focussing on the Implicit or Authorization Grant workflows.
Important note: The trickiness seems to come from the fact that the MyApp API is stateless, so there is no long-lived session in which to store tokens. On that basis, it seems like tokens need to be stored either in the frontend (e.g. local storage/cookies etc) or in a backend database.
Below is my interpretation of two possible approaches. I'd appreciate thoughts/corrections.
Option 1: Implicit flow - tokens stored FE, passed along to BE which then makes requests to Google
Pros:
Allows access to user's own data
Simpler flow, access_token retrieved immediately without needing the code step
Less steps to implement between initial sign-in process and actually obtaining data
No need for a backend database, can resend the token with each request
Cons:
Frontend (browser) has access to Google access_token which seems unnecessary and is a potential security concern
It seems like a strange process to pass the access_token from FE to BE, purely to allow BE to then use that token to make another request
I'm not sure how we would refresh/renew tokens since I understand that storing refresh_tokens on the client is bad practice. It would not be a good user experience if the user had to frequently sign in to reconnect their account
Option 2: Authorization Code Flow - all communication with Google via BE, tokens stored in BE database
Pros:
Allows access to user's own data
Other than the code-request / consent page, all communication with Google is implemented backend, so the tokens are not accessible on the client
Client secret can be used from the BE
Cons:
More complex flow, requires extra steps
Given that the BE is stateless, it's not clear how best to store the tokens. It seems like it would require storing them in a database which is extra complication and seems like it would have security implications - how would you properly secure / encrypt the access_token/refresh_tokens in said database?
Conclusion
Given that the data processing is to happen on the backend, option 2 seems slightly more suitable because the sensitive tokens can be hidden from the frontend app, and several clients (web frontend, mobile apps) have less obligation to be involved in the process with the exception of the initial sign in / user consent. However I’m not sure whether having a database full of user auth tokens is a good idea or how I could properly protect this database.
The good news is that both options are perfectly valid and equally secure. The concern about a short-lived Access Token being in the browser isn't an issue. Equally, if you only held the tokens on the BE, then you would need to implement your own client authentiation/session/JWT blah blah, which presents the same attack surface.
I've done both, and am currently migrating from BE to FE. In my case the reason is that everything I need to do, I can do on the FE, so I end up with no BE at all. This isn't strictly true since I do some onboarding/payment with the BE, but that's about all.
So the best approach depends on factors beyond those in your question, such as the nature of app, what the BE cost is and how important that is, what your devops skillsets look like for maintaining two environments, to what extent a BE is required anyway, vs being completely optional.
Related
I'm building some RESTful API for my project based on Play Framework 2.X.
My focus is on the authentication mechanism that I implemented.
Currently, I make use of SecureSocial.
The workflow is:
An anonymous user calls a secured API
Server grabs any cookie Id (kind of authentication token) and checks for matching in the Play 2 cache. (cache contains an association between cookie Id (randomly generated) and the user Id, accessible from database.
If any matched, user is authorized to process its expected service.
If none matched, user is redirected to a login page, and when filled with valid credentials (email/password), server stores its corresponding authentication data on Play 2 cache, and sends the newly created Cookie containing only a custom Id (authentication token) to user and of course, secured through SSL.
While the cookie/token doesn't expire, the user can call secured api (of course, if authorized)
The whole works great.
However, after some search, I came across this post, and ...I wonder if I'm in the right way.
Indeed, dealing with cookies ("sessions" in Play's term), would break the rule Restfulness.
Because an api really considered as stateless should be called with ALL the needed data at once (credentials/tokens etc..). The solution I implemented needs both calls: one to authenticate, the other to call the secured API.
I want to make things well, and I wonder some things:
What about the use of Api keys? Should I implement a solution using them instead of this SecureSocial workflow? Api Keys would be sent at EVERY API CALL, in order to keep restfulness.
I think about it since I want my APIs to be reached by some webapps, mobiles and other kind of clients. None of all are forced to manage cookies.
What about OAuth? Should I really need it? Would it replace totally the usage of simple api keys? Always with this objective of several clients, this known protocol would be a great way to manage authentication and authorization.
In one word, should I implement another mechanism in order to be Restful compliant?
this is quite an old Q, but still worth answering as it may interest others.
REST does mandate statelessness, but authorization is a common exception when implementing.
The solution you described requires a single authorization process, followed by numerous service calls based on authorized cookie. This is analog to api keys or OAuth. There's nothing wrong with cookies as long as the service isn't of high-security nature and that you expire then after a reasonable time.
Integrating OAuth into your service sounds a bit of an overkill and is recommended only if you expose the API to 3rd parties (outside your organization).
We have a large high traffic site with a lot of data on it (similar to Kickstarter), and we want to provide to our content/project creators a means of pulling their data from our site via an API.
Someone suggested I use OAuth, however my experience with OAuth is limited to setting up a twitter datasource.
What I want to do
Provide a user an Application ID and a 'secret'
Allow this user to connect to our application via an api endpoint, authorizing themselves using the api ID and secret
Once verified, allow this user to pull only their data from the application
The data that a user can pull: votes they have cast, pledges they have made, purchases they have made, projects/ideas they have launched, data about those projects/ideas (votes/purchases/orders/cancellations etc)
My question is:
Is OAuth overkill?
Is there a better way to handle a user/users website to connect to our API and pull/verify certain data by using the API we make available, while requiring each incoming request to be authorized for the user/site initiating that request.
Ideally, we will have an endpoint that is accessed as:
https://api.oursite.com/request/params
We want this to be as simple as possible for our users that wish to implement this interface. Thanks for your help!
Generally it's OAuth, in combination with SSL. That's the standard and is likely to stay. Before we saw also logins: username + password to access an API but that's becoming less and less.
So the suggested way is OAuth. There are no serious other solutions yet. To make it easier to adopt your API you could release some classes in some development languages so developers can have a quick start. You could start releasing those classes at for example GitHub to raise adoption of your API and get a quick access to developers. They might, if you do well, even start improving it.
Background: I am trying to create an SMS API service. The developers have a Dev ID, and an API secret key assigned to their developer account. The developers will be creating apps which will issue calls to my API. But the application issuing the call must be verified first.
Issue: The main issue i have is with authentication. I read up on OAuth and pretty much uderstood it. I read through this presentation (Slide 71-82). All OAuth articles talk about the OAuth 'dance' or the 'love triangle'. My problem seems to be, that i dont see a proper triangle in my case. Or, a better way to put it would be, the triangle doesn't seem to be complete.
What i mean by that is, in the case of lets say, LinkedIn, trying to make some app which helps users associate their LinkedIn acc with twitter, OAuth makes complete sense. Because LinkedIn needs to get resources from twitter ON THE USERS BEHALF (Cuz the user HAS A TWITTER ACCOUNT). In my case, only the consumer has a developer account registered with my service. The end-user doesn't have any credentials for the consumer to ask on behalf of. So how can i implement Oauth? So what will the consumer ask the provider? Will it only state that "watch out, here i come?". Cuz that seems pretty pointless unless its asking for a request token in exchange for an access token. But in this case since the end user doesnt even have an account, the steps seem useless.
So, i cant figure out how to go about this authentication issue. Ive tried thinking about using php sessions so it can help me associate a token with the particular client who is using the API. But the REST/OAUTH purists seem to disagree on the usage of sessions in authentication. They claim that OAuth is a standard which has proven itself and that is what I should use instead of coming up with my own obscure schemes.
From your description it seem that you're in a two party scenario only (developers write code which accesses your API on their own behalf, not on behalf of an end-user), so that means indeed that doing the full 3-legged oAuth scenario isn't needed.
You could use pretty much any authentication scheme and that would work (API Keys, other oAuth grant types [see below] or even ID/Secret combinations. In the oAuth world:
Look at the other oAuth 2.0 Grant types: especially resource owner PW grants - https://datatracker.ietf.org/doc/html/draft-ietf-oauth-v2-26#section-4.3. It's slightly better than username-password because the PW isn't passed across the channel all the time (it passes once though) and it assumes the developer writing the code is the owner of the credentials.
Look at oAuth v1.0: this different in various ways to v2.0 but one feature it does have which some people like is the way tokens are used - which is rather than being passed across the wire they are used to generate a hash in the client and then the hash is verified on the server side. It's more expensive and complex than checking a key but it's less prone to attack.
In the non-oAuth world, if it's primarily a server resource used by developers directly, an ID/Secret or API-Key pattern is probably more than sufficient and it's much easier to implement for your developers.
Re: oAuth - if you're doing any type of user auth then definitely stick with the standard - the stuff is complex and having libraries out there really helps. If it's developer-api you likely don't need to go that far.
If you want the API to be secure in an ideal world anything which requires the security token to pass across the gaps should be secured using SSL, especially if that client code could be running on a mobile device or laptop which might communicate over wireless. If this isn't the case, someone could jump in an copy a token from one of the devs.
The only one of the protocols above that avoids this is the oAuth 1.0 variation since the secret never leaves the client but is used to hash instead. But it's complex. Last one to look at is the Amazon AWS pattern which does hashing similar to oAuth 1.0 http://docs.amazonwebservices.com/AmazonS3/latest/dev/RESTAuthentication.html and people emulate quite a bit.
Which are the steps must I follow to implement a token authentication in my web page?
Any summary or links will be appreciated.
I want to implement similar to Facebook or Google, first time client loggin and receive token and then use it in next actions.
I read also about OAuth but I don't want to give access to my application from 3rd party.
Thanks for the long response and it seems clear to me I need to read more about this.
What I want is to know the "steps" to implement a basic web application that uses token authentication. That is user logging once and then can make some actions: add content, edit, etc.
I know what I'm saying is similar to a session, where server adds a SESSION_ID on the HTML header and later request are identified and associated with that session. I read sessions way isn't good to scale so I want to implement a similar system like gmail or facebook before they go to OAuth. Probably I'm talking about something similar to oauth (i don't read in much depth) but witj two-legged instead three-legged.
You should think about your requirements, pick an appropriate protocol and some decent piece of software that implements it.
It's really hard to say more without more details:
are you talking about authentication for one or for multiple web applications? do you need single sign on between different web applications?
should all user data be stored on your server or should user be able to login e.g. with the google account?
should the token contain informations about the user?
on what platform are your applications developed?
what authentication method should be used?
do you want to realize a portal?
There is a really wide range of protocols and tools which might or might not fit to your requirements:
http://en.wikipedia.org/wiki/Category:Authentication_methods
http://en.wikipedia.org/wiki/Category:Identity_management_systems
I personally like CAS ( http://www.jasig.org/cas) for token-base SSO between multiple web applications. It's Java based but also has some support for PHP and .Net.
OpenID is fine, if you want to allow users to login with their Google, Yahoo, whatever account (configurable...) and don't want to store user information by yourself.
Kerberos/SPNEGO is the way to go if you want to haven integrated windows-sso for your corporate intranet applications.
For university applications SAML/Shibboleth probably is best. Outside universities it's somewhat less popular, probably cause it's a fairly complex protocol.
Oh and I almost forget: Most of the web frameworks/standards have there own version of plain-old "form based authentication". Where a user goes to a login form enters its username and password. Both are with or without SSL transported to the web/application server. The server validates it against some kind of database and gives a cookie to the user, which is transmitted and validated every time the user sends a request. But beside all this shiny protocols this seems to be pretty boring :-)
And before doing anything with web authentication, you might think for a moment about web security in general ( http://journal.paul.querna.org/articles/2010/04/11/internet-security-is-a-failure/ http://www.eff.org/files/DefconSSLiverse.pdf) and what you can do to not make it even worse on your site ( http://www.codinghorror.com/blog/2008/08/protecting-your-cookies-httponly.html http://owasptop10.googlecode.com/files/OWASP%20Top%2010%20-%202010.pdf).
see your point.
On the protocol level a very simplistic token approach is HTTP Basic Authentication. But this often doesn't fit, as there is no logout function etc.
A custom, simple cookie based approach can for example look like this:
The server generates some kind of secret (a value that is hard to guess)
When a user tries to access a protected resource, he is redirected to a login form
after successful authentication he gets a cookie. This cookie contains three values: username, timestamp and a hash of {username server-secret timestamp}.
with every user request the server recalculates the hash values and compares it to the value which the client sends in its cookie
(needs more consideration of: httponly and secure flag, transport layer security, replay attacks etc)
Amazon S3 stores its authentication token in an HTTP Header and uses HMAC for calculating it. It's described here: http://docs.amazonwebservices.com/AmazonS3/latest/dev/index.html?S3_Authentication.html (Not necessarily recommended for using with a browser based web application)
If there is a book about REST anywhere near you, you may look if it has a chapter about authentication. Probably things are much nicer explained there than here :-)
There are some frameworks which are capable of doing this kind of authentication. For security reasons it would make sense to check them first before implementing your own stuff.
Overview
I'm looking to create a (REST) API for my application. The initial/primary purpose will be for consumption by mobile apps (iPhone, Android, Symbian, etc). I've been looking into different mechanisms for authentication and authorization for web-based APIs (by studying other implementations). I've got my head wrapped around most of the fundamental concepts but am still looking for guidance in a few areas. The last thing I want to do is reinvent the wheel, but I'm not finding any standard solutions that fits my criteria (however my criteria my be misguided so feel free to critique that as well). Additionally, I want the API to be the same for all platforms/applications consuming it.
oAuth
I'll go ahead and throw out my objection to oAuth since I know that will likely be the first solution offered. For mobile applications (or more specifically non-web applications), it just seems wrong to leave the application (to go to a web-browser) for the authentication. Additionally, there is no way (I am aware of) for the browser to return the callback to the application (especially cross-platform). I know a couple of apps that do that, but it just feels wrong and gives a break in the application UX.
Requirements
User enters username/password into application.
Every API call is identified by the calling application.
Overhead is kept to a minimum and the auth aspect is intuitive for developers.
The mechanism is secure for both the end user (their login credentials are not exposed) as well as the developer (their application credentials are not exposed).
If possible, not require https (by no means a hard requirement).
My Current Thoughts on Implementation
An external developer will request an API account. They will receive an apikey and apisecret. Every request will require at minimum three parameters.
apikey - given to developer at regisration
timestamp - doubles as a unique identifier for each message for a given apikey
hash - a hash of the timestamp + the apisecret
The apikey is required to identify the application issuing the request. The timestamp acts similarly to the oauth_nonce and avoids/mitigates replay attacks. The hash ensures that request was actually issued from the owner of the given apikey.
For authenticated requests (ones done on the behalf of a user), I'm still undecided between going with an access_token route or a username and password hash combo. Either way, at some point a username/password combo will be required. So when it does, a hash of several pieces of information (apikey, apisecret, timestamp) + the password would be used. I'd love feedback on this aspect. FYI, they would have to hash the password first, since I don't store the passwords in my system without hashing.
Conclusion
FYI, this isn't a request for how to build/structure the API in general only how to handle the authentication and authorization from solely within an application.
Random Thoughts/Bonus Questions
For APIs that only require an apikey as part of the request, how do you prevent someone other than the apikey owner from being able to see the apikey (since sent in the clear) and make excessive requests to push them over usage limits? Maybe I'm just over thinking this, but shouldn't there be something to authenticate that a request was verified to the apikey owner? In my case, that was the purpose of the apisecret, it is never shown/transmitted without being hashed.
Speaking of hashes, what about md5 vs hmac-sha1? Does it really matter when all of the values are hashed with with sufficiently long data (ie. apisecret)?
I had been previously considering adding a per user/row salt to my users password hash. If I were to do that, how could the application be able to create a matching hash without knowing the salt used?
The way I'm thinking about doing the login part of this in my projects is:
before login the user requests a login_token from the server. These are generated and stored on the server on request, and probably have a limited lifetime.
to login the application calculates the hash of the users password, then hashes the password with the login_token to get a value, they then return both the login_token and the combined hash.
The server checks the login_token is one that it has generated, removing it from its list of valid login_tokens. The server then combines its stored hash of the user's password with the login_token and ensures that it matches the submitted combined token. If it matches you have authenticated your user.
Advantages of this are that you never store the user's password on the server, the password is never passed in the clear, the password hash is only passed in the clear on account creation (though there may be ways around this), and it should be safe from replay attacks as the login_token is removed from the DB on use.
That's a whole lot of questions in one, I guess quite a few people didn't manage to read all the way to the end :)
My experience of web service authentication is that people usually overengineer it, and the problems are only the same as you would encounter on a web page. Possible very simple options would include https for the login step, return a token, require it to be included with future requests. You could also use http basic authentication, and just pass stuff in the header. For added security, rotate/expire the tokens frequently, check the requests are coming from the same IP block (this could get messy though as mobile users move between cells), combine with API key or similar. Alternatively, do the "request key" step of oauth (someone suggested this in a previous answer already and it's a good idea) before authenticating the user, and use that as a required key to generate the access token.
An alternative which I haven't used yet but I've heard a lot about as a device-friendly alternative to oAuth is xAuth. Have a look at it and if you use it then I'd be really interested to hear what your impressions are.
For hashing, sha1 is a bit better but don't get hung up about it - whatever the devices can easily (and quickly in a performance sense) implement is probably fine.
Hope that helps, good luck :)
So what you're after is some kind of server side authentication mechanism that will handle the authentication and authorisation aspects of a mobile application?
Assuming this is the case, then I would approach it as follows (but only 'cos I'm a Java developer so a C# guy would do it differently):
The RESTful authentication and authorisation service
This will work only over HTTPS to prevent eavesdropping.
It will be based on a combination of RESTEasy, Spring Security and CAS (for single sign on across multiple applications).
It will work with both browsers and web-enabled client applications
There will be a web-based account management interface to allow users to edit their details, and admins (for particular applications) to change authorisation levels
The client side security library/application
For each supported platform (e.g.
Symbian, Android, iOS etc) create a
suitable implementation of the
security library in the native
language of the platform (e.g. Java,
ObjectiveC, C etc)
The library
should manage the HTTPS request
formation using the available APIs
for the given platform (e.g. Java
uses URLConnection etc)
Consumers of the general authentication and
authorisation library ('cos that's
all it is) will code to a specific
interface and won't be happy if it
ever changes so make sure it's very
flexible. Follow existing design
choices such as Spring Security.
So now that the view from 30,000ft is complete how do you go about doing it? Well, it's not that hard to create an authentication and authorisation system based on the listed technologies on the server side with a browser client. In combination with HTTPS, the frameworks will provide a secure process based on a shared token (usually presented as a cookie) generated by the authentication process and used whenever the user wishes to do something. This token is presented by the client to the server whenever any request takes place.
In the case of the local mobile application, it seems that you're after a solution that does the following:
Client application has a defined Access Control List (ACL) controlling runtime access to method calls. For example, a given user can read a collection from a method, but their ACL only permits access to objects that have a Q in their name so some data in the collection is quiety pulled by the security interceptor. In Java this is straightforward, you just use the Spring Security annotations on the calling code and implement a suitable ACL response process. In other languages, you're on your own and will probably need to provide boilerplate security code that calls into your security library. If the language supports AOP (Aspect Oriented Programming) then use it to the fullest for this situation.
The security library caches the complete list of authorisations into it's private memory for the current application so that it doesn't have to remain connected. Depending on the length of the login session, this could be a one-off operation that never gets repeated.
Whatever you do, don't try to invent your own security protocol, or use security by obscurity. You'll never be able to write a better algorithm for this than those that are currently available and free. Also, people trust well known algorithms. So if you say that your security library provides authorisation and authentication for local mobile applications using a combination of SSL, HTTPS, SpringSecurity and AES encrypted tokens then you'll immediately have creditibility in the marketplace.
Hope this helps, and good luck with your venture. If you would like more info, let me know - I've written quite a few web applications based on Spring Security, ACLs and the like.
Twitter addressed the external application issue in oAuth by supporting a variant they call xAuth. Unfortunately there's already a plethora of other schemes with this name so it can be confusing to sort out.
The protocol is oAuth, except it skips the request token phase and simply immediately issues an access token pair upon receipt of a username and password. (Starting at step E here.) This initial request and response must be secured - it's sending the username and password in plaintext and receiving back the access token and secret token. Once the access token pair has been configured, whether the initial token exchange was via the oAuth model or the xAuth model is irrelevant to both the client and server for the rest of the session. This has the advantage that you can leverage existing oAuth infrastructure and have very nearly the same implementation for mobile/web/desktop applications. The main disadvantage is that the application is granted access to the client's user name and password, but it appears like your requirements mandate this approach.
In any case, I'd like to agree with your intuition and that of several other answerers here: don't try to build something new from scratch. Security protocols can be easy to start but are always hard to do well, and the more convoluted they become the less likely your third-party developers are to be able to implement against them. Your hypothetical protocol is very similar to o(x)Auth - api_key/api_secret, nonce, sha1 hashing - but instead of being able to use one of the many existing libraries your developers are going to need to roll their own.
Super late to the party but I wanted to throw in some additional points to consider for anyone interested in this issue. I work for a company doing mobile API security solutions (approov) so this whole area is definitely relevant to my interests.
To start with, the most important thing to consider when trying to secure a mobile API is how much it is worth to you. The right solution for a bank is different to the right solution for someone just doing things for fun.
In the proposed solution you mention that a minimum of three parameters will be required:
apikey - given to developer at registration
timestamp - doubles as a unique identifier for each message for a given apikey
hash - a hash of the timestamp + the apisecret
The implication of this is that for some API calls no username/password is required. This can be useful for applications where you don't want to force a login (browsing in online shops for example).
This is a slightly different problem to the one of user authentication and is more like authentication or attestation of the software. There is no user, but you still want to ensure that there is no malicious access to your API. So you use your API secret to sign the traffic and identify the code accessing the API as genuine. The potential problem with this solution is that you then have to give away the secret inside every version of the app. If someone can extract the secret they can use your API, impersonating your software but doing whatever they like.
To counter that threat there are a bunch of things you can do depending on how valuable the data is. Obfuscation is a simple way to make it harder to extract the secret. There are tools that will do that for you, more so for Android, but you still have to have code that generates your hash and a sufficiently skilled individual can always just call the function that does the hashing directly.
Another way to mitigate against excessive use of an API that doesn't require a login is to throttle the traffic and potentially identify and block suspect IP addresses. The amount of effort you want to go to will largely depend upon how valuble your data is.
Beyond that you can easily start getting into the domain of my day job. Anyway, it's another aspect of securing APIs that I think is important and wanted to flag up.