The value of a standard is that two parties who have never spoken can interoperate. The cost is that neither of them can fix the other's interpretation of it.
This piece walks through how we think about it at Paycux, what we have changed our minds about, and where the sharp edges are.
What is SCIM?
What is SCIM? deserves its own treatment. 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.
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.
What is a SCIM attribute?
What is a SCIM attribute? deserves its own treatment. 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
SCIM attributes: A breakdown
SCIM attributes: A breakdown 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.
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.
Common attributes to each group/user
That brings us to common attributes to each group/user. 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.
Treat anything the other side sends as untrusted input until it has been through validation you wrote.
Default attributes
That brings us to default attributes. 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.
Enterprise users
Enterprise users deserves its own treatment. 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.
Extending SCIM with custom attributes
Extending SCIM with custom attributes deserves its own treatment. 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.
Where this leaves us
The pattern repeats across every system we have looked at: the hard part is not the mechanism, it is keeping the mechanism honest as the surrounding assumptions change.
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.
Everything here, already built
Sign-in, enterprise SSO, directory provisioning, roles and an audit trail behind one API.