Produits Entr'ouvert » Lasso

I use Lasso in an IDP implementation (LemonLDAP::NG), and some SP are sometimes incorrectly configured to omit signatures.

When that happens, lasso_login_process_authn_request_msg returns LASSO_DS_ERROR_INVALID_SIGALG (Invalid signature algorithm) which is confusing: our users generally try to change signature algorithms and don't realize that the signature is just not there at all.

In my humble opinion, Lasso should return LASSO_DS_ERROR_SIGNATURE_NOT_FOUND (Signature element not found) in this situation.

The code that causes this is https://dev.entrouvert.org/projects/lasso/repository/33/revisions/main/entry/lasso/xml/tools.c#L1031

I think the missing "Signature" parameter should be checked before the missing "SigAlg" parameter, so that if both are missing, "Signature element not found" is returned to the user as a hint that the signature is missing, and not just using the wrong algorithm.

When using POST binding, this issue is not present: "Signature element not found" is returned when the signature is missing.

Trivial patch attached