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Protocols18 December 2023·3 min read

OAuth and JWT: How To Use Together + Best Practices

Protocol work looks tedious from the outside and turns out to be where the interesting failures live.

Paycux engineering

Protocol work looks tedious from the outside and turns out to be where the interesting failures live. The specification is short; the space of things implementers actually ship is not.

This piece walks through how we think about it at Paycux, what we have changed our minds about, and where the sharp edges are.

Comparing OAuth with JWT

Comparing OAuth with JWT is where this gets concrete. Version the assumption, not just the code. Write down what you expect from the peer, and make the failure loud when it stops being true, because the alternative is a connection that half works for six weeks.

Normalization is the whole job. Two providers can be perfectly compliant and still disagree about what a group membership is, whether a logout is meaningful, and which attribute carries the email address.

What is OAuth?

Consider what is oauth?. Normalization is the whole job. Two providers can be perfectly compliant and still disagree about what a group membership is, whether a logout is meaningful, and which attribute carries the email address.

Normalization is the whole job. Two providers can be perfectly compliant and still disagree about what a group membership is, whether a logout is meaningful, and which attribute carries the email address.

  • Validate signature, issuer, audience and expiry as four separate checks
  • Normalize provider attributes into one internal shape
  • Fail loudly when a peer stops meeting a documented assumption
  • Keep a fixture per provider so regressions surface in CI

What is JWT?

What is JWT? is where this gets concrete. Treat anything the other side sends as untrusted input until it has been through validation you wrote. Signature checks, issuer checks, audience checks and expiry checks are four separate decisions, and skipping any one of them is a real vulnerability rather than a theoretical one.

Version the assumption, not just the code. Write down what you expect from the peer, and make the failure loud when it stops being true, because the alternative is a connection that half works for six weeks.

Which one should you use?

Which one should you use? is where this gets concrete. Normalization is the whole job. Two providers can be perfectly compliant and still disagree about what a group membership is, whether a logout is meaningful, and which attribute carries the email address.

Treat anything the other side sends as untrusted input until it has been through validation you wrote. Signature checks, issuer checks, audience checks and expiry checks are four separate decisions, and skipping any one of them is a real vulnerability rather than a theoretical one.

Normalization is the whole job.

How to use JWT With OAuth 2 for Secure SSO

How to use JWT With OAuth 2 for Secure SSO deserves its own treatment. Treat anything the other side sends as untrusted input until it has been through validation you wrote. Signature checks, issuer checks, audience checks and expiry checks are four separate decisions, and skipping any one of them is a real vulnerability rather than a theoretical one.

Normalization is the whole job. Two providers can be perfectly compliant and still disagree about what a group membership is, whether a logout is meaningful, and which attribute carries the email address.

How It Works

That brings us to how it works. Treat anything the other side sends as untrusted input until it has been through validation you wrote. Signature checks, issuer checks, audience checks and expiry checks are four separate decisions, and skipping any one of them is a real vulnerability rather than a theoretical one.

Version the assumption, not just the code. Write down what you expect from the peer, and make the failure loud when it stops being true, because the alternative is a connection that half works for six weeks.

Benefits:

Consider benefits:. Version the assumption, not just the code. Write down what you expect from the peer, and make the failure loud when it stops being true, because the alternative is a connection that half works for six weeks.

Version the assumption, not just the code. Write down what you expect from the peer, and make the failure loud when it stops being true, because the alternative is a connection that half works for six weeks.

Where this leaves us

None of this is exotic. It is the ordinary discipline of deciding what you own, writing down what you assume, and making the failures loud enough to notice.

If you are working through the same problem and want to compare notes, the docs cover the mechanics and the console shows the behaviour on your own data.

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