Why Mastercard Doesn't Use OAuth 2.0

https://developer.mastercard.com/blog/why-mastercard-doesnt-use-oauth-20

by hitr • 8 years ago

144 34 8 years ago

developer.mastercard.com

simonw• 8 years ago

It looks like they are concerned that OAuth 2.0 doesn't include a cryptographic signature of the request body, as seen in OAuth 1.0.

My understanding is that OAuth 2.0 dropped that signature in favour of requiring TLS to protect against tampering. I'd be interested to know why Mastercard doesn't consider this to be as good as the request body signatures in OAuth 1.0.

lwf• 8 years ago

From a technical PoV, it feels like it is easier to argue after the fact "look, you sent this message, you signed it", v.s. "trust us, all comms were over TLS, we promise our logs are accurate and your token was not leaked".

ars• 8 years ago

It's quite common for companies to MITM https requests (and install their personal certificate on all company owned machines so the browser raises no errors).

Some countries do so as well, for example Kazakhstan and China.

gsich5• 8 years ago

And people from that country have those certificates installed? Voluntarily?

badrabbit• 8 years ago

It's common to mitm TLS in banking sector in the US

alangpierce2• 8 years ago

An argument I've heard against TLS is that it's easy for clients to get wrong. In some cases, client code needs to directly check that the certificate matches the intended domain, and forgetting to do so makes TLS worthless because an attacker can just use any valid certificate. In other cases, certificate checking runs into some problem, and an inexperienced developer finds a "solution" on StackOverflow to just disable certificate checking, which, again, makes TLS worthless. In other cases, a client might make a valid TLS request to the wrong server (either by mistake or due to some other attack).

With OAuth 2, any of these problems will leak your bearer token, meaning than an attacker can act as you until the token expires.

With OAuth 1, you're typically going over TLS anyway, but even if an attacker knows the contents of all requests, they won't be able to act as you because they still won't be able to sign any future requests.

Edit: I just dug up the blog post I've read that describes most of the points I made above: https://hueniverse.com/oauth-bearer-tokens-are-a-terrible-id...

tomohawk• 8 years ago

Having developed apps that use TLS in many languages, this is very true for most of them. I was pleasantly surprised by the Go TLS library - it gets all of this correct by default.

narsil• 8 years ago

I'm not sure I understand the concern with integrity of OAuth 2.0 payloads. Sending the request over HTTPS already ensures that the request is not tampered with, and also guards against replay attacks.

bootloop• 8 years ago

Wouldn't this be a reasonable reason if you consider that they might use additional equipment to terminate HTTPS connection in an early layer of their network?

gsich5• 8 years ago

no. You don't know where the TLS terminates.

geocar• 8 years ago

Breaking IP (e.g. MITM the server) means you get a TLS certificate anyway. This might be easier done than said[1].

Breaking IP might not even be necessary because programmers are dumb[2].

[1] https://www.bleepingcomputer.com/news/security/dns-poisoning...

[2] http://web.archive.org/web/20120317165131/http://forum.devel...

dogma1138• 8 years ago

No it can potentially ensure integrity between the a client and the first TLS hop that’s about it.

You don’t know which client it actually came from and you can’t ensure integrity within the transaction flow of your app.

Say the request terminated at a LB proxy then passed through and API gateway into an MQ then goes through multiple servers you need some form of integrity checking for the request and OAUTH 2.0 doesn’t provide it.

gsich5• 8 years ago

Using TLS makes it acceptable to send cleartext passwords. I don't know why, seems lazy.

So, I understand why Mastercard doesn't rely on that.

viraptor3• 8 years ago

TLS makes it acceptable to send cleartext passwords

What do you mean? There exists a NULL cipher, but it needs to be agreed on by both sides. If mastercard doesn't allow NULL, you can't send anything in cleartext. Or did you think of something else?

ge0rg• 8 years ago

The problems are before and after the TLS tunnel.

I've seen a BigCorp load balancer / web firewall log the first 1KB of each HTTP POST body into a permanent archive. A typical login submission is much smaller than that. Also in some networks the TLS connection is terminated by a frontend server and backend communication is plaintext HTTP.

While these examples are obviously bad practice, having your requests signed and not leak user passwords would easily nullify their impact.

gsich5• 8 years ago

What do you mean?

Login with user/password. Now the receiving end knows your plaintext password. It might get hashed, but you don't know when. Twitter I think had the latest failure with that, logging the password.

TLS is just that no MITM can see the data and that you can somewhat verify who you are connecting too.

smooc• 8 years ago

Any app that takes security seriously will need to take a layered approach. So while Oauth 2, which is just a framework contrary to oauth 1.0a, seems to outsource its integrity protection to TLS this isnt enough: others have already pointed out that many companies hijack TLS at their edge proxies. Banks do this bu requirement of the regulator.

So you would need additional defenses against tampering such as OpenID Connect. In the banking apps that I have been working with we implemented additional symmetric encryption on top of the protocol (yes obfuscating the keys) and all other kinds of small things.

I’m glad mastercard does not rely solely on TLS.

ploxiln• 8 years ago

So I guess the alternative would be to tunnel TLS inside TLS. So they can set up fake CAs to intercept the outer TLS, but not the inner TLS, satisfying both bank regulators and actual security. Until regulators catch on and we have to go around in circles again ...

alangpierce2• 8 years ago

Related: here's a write-up from one of the OAuth 2 authors on the problems he sees in OAuth 2 and why he thinks OAuth 1 is better:

https://hueniverse.com/oauth-2-0-and-the-road-to-hell-8eec45...

EGreg• 8 years ago

I once asked a related question on StackOverflow

https://security.stackexchange.com/questions/161734/why-does...

jacksmith21006• 8 years ago

Curious how many have moved from LDAP to using OAuth?

Would seem the future for enterprise will be OAuth.

Noumenon72• 8 years ago

I think https://aaronparecki.com/oauth-2-simplified/ explains that the cryptographic signature approach (if that's what they mean by "client secret") was discarded because mobile apps and single-page Javascript apps can't maintain the confidentiality of a secret anyway.

So maybe OAuth 1.0 is only better for apps running on a server?

dwaite• 8 years ago

They did this to provide message-level integrity. OAuth 2 switched to Transport-level confidentiality/Integrity.

It's worth noting that message-level integrity was not a design goal of OAuth 1; it is was a consequence of being based on OpenID 1/2, which were explicitly meant to run on HTTP without TLS so that they could be adopted by blogs. This was pre SNI, and pre cheap certs, so requiring HTTPS increased the hosting cost of a blog by an order of magnitude.

When the constraints changed such that requiring HTTPS was feasible, it greatly simplified OAuth. Some of these simplified proposals for OAuth became the input for OAuth 2 (where complexity was subsequently added back in the form of variants to support new use cases).

Relying on message level integrity in a protocol where such a thing was basically a side-effect of avoiding hosting costs would make me very nervous.

The clearest issue I can point to is that there is no response message integrity in MasterCard's system - an intermediary can block requests to MasterCard and give back fraudulent responses (yes, of course that payment went through!). This throws a ton of application-dependent security considerations into the system.

starptech• 8 years ago

The problems reminds me of https://github.com/hueniverse/oz/ it's from one of the former oauth guys.

woranl• 8 years ago

It’s unfortunate that Big companies are pushing for OAuth 2.0 and trying to blindsided developers as if OAuth 2.0 is an upgrade to OAuth 1.0a. It is not! OAuth 1.0a provides authenticity, integrity, and non-repudiation. Something that OAuth 2.0 cannot match.

Why Mastercard Doesn't Use OAuth 2.0

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