Add Service Provider test cases for Microsoft Entra ID SAML Responses

[OscarVanL]

It would be good to have some additional test cases covering Microsoft Entra ID (Microsoft 365) SAML SSO.

In #605 I encountered the v0.5.0 release caused some regressions parsing these responses, but these were in my company's private test cases that unfortunately cannot be shared. This meant that the #580 change had to be reverted in v0.5.1.

It would be helpful if someone could contribute some Microsoft 365 SAML response test cases to add to the existing cases, such as testdata/TestSPCanHandleEntraIDResponse, this way it would be possible to try #580 again with more confidence it doesn't cause regressions.

[alexkoolschijn]

not sure if this wht you are looking for:

func SamlMiddleware() (*samlsp.Middleware, error) {
spUrl, err := url.Parse("https://babbage.abdaal.nl/")
//spUrl, err := url.Parse("http://localhost:3000/")
if err != nil {
log.Fatalf("Failed to parse SP URL: %v", err)
}

idpMetadataURL, err := url.Parse("https://login.microsoftonline.com/<tenent-ID>/federationmetadata/2007-06/federationmetadata.xml?appid=APP-ID") 

// this is found under "SAML-based Sign-on" > "SAML Certificates" > "App Federation Metadata Url"
if err != nil {
log.Fatalf("Failed to parse IDP Metadata URL: %v", err)
}

idpMetadata, err := samlsp.FetchMetadata(context.Background(), http.DefaultClient, *idpMetadataURL)
if err != nil {
	log.Fatalf("Failed to fetch IDP Metadata: %#v", err)
}

// Load your SP X.509 certificate and private key.
keyPair, err := tls.LoadX509KeyPair("service.cert", "service.key")
if err != nil {
	log.Fatalf("failed to load key pair: %v", err)
}

keyPair.Leaf, err = x509.ParseCertificate(keyPair.Certificate[0])
// Configure the SAML SP with the parsed URL
samlMiddleware, err := samlsp.New(samlsp.Options{
	URL:               *spUrl,
	Key:               keyPair.PrivateKey.(*rsa.PrivateKey),
	Certificate:       keyPair.Leaf,
	IDPMetadata:       idpMetadata,
	SignRequest:       false,
	AllowIDPInitiated: false,
	ForceAuthn:        false,
})

return samlMiddleware, err

}

giving you the option to use the claims e.g

// Get user attribute from SAML session
email := samlsp.AttributeFromContext(r.Context(), "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress")
givenName := samlsp.AttributeFromContext(r.Context(), "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/givenname")
surname := samlsp.AttributeFromContext(r.Context(), "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/surname")
memberOf := samlsp.AttributeFromContext(r.Context(), "http://schemas.xmlsoap.org/claims/Group")