How do I set different digest algorithm and signature algorithm for an idp in simplesamlphp

I am trying to set

DigestMethod Algorithm to

http://www.w3.org/2001/04/xmlenc#sha256

and SignatureMethod Algorithm to

http://www.w3.org/2000/09/xmldsig#rsa-sha1

I have set

'metadata.sign.algorithm' => 'http://www.w3.org/2001/04/xmldsig-more#rsa-sha256'

and

'signature.algorithm' => 'http://www.w3.org/2000/09/xmldsig#rsa-sha1'

I saw from a changelog that metadata.sign.algorithm was introduced as the digest algorithm. However both digest algorithm and signature algorithm seem to be taking from the value signature.algorithm. I am using SimpleSamlP v1.18.4.

Thanks in advance for your help.

Solution

It looks like SimpleSamlPHP does not allow this to be done. However I patched Utils.php inside SAML2 library to get this working

diff --git a/src/SAML2/Utils.php b/src/SAML2/Utils.php
index e894a3e..4894f84 100644
--- a/src/SAML2/Utils.php
+++ b/src/SAML2/Utils.php
@@ -339,6 +339,11 @@ class Utils
                 $type = XMLSecurityDSig::SHA1;
         }

+        // Patch to get SimpleSAMLPHP to return different
+        // algorithms for signature and digest
+        // to address Login.gov logout issue.
+        $type = XMLSecurityDSig::SHA256;
+
         $objXMLSecDSig->addReferenceList(
             [$root],
             $type,

I set the signature algorithm to SHA1 in the config and applied this patch via composer to have digest use the SHA256 algorithm.