Overriding IdP Metadata Parser

An implementation of the ISamlMetadataParser interface parses the partner identity provider's metadata document when using the Automatic Metadata Lookup feature.

The common use cases for overriding the parser include:

• Selecting a different endpoint. The default parser prefers HTTP-POST binding over other binding types. This is because this binding type offers increased security over HTTP-Redirect.
• The metadata parser contains multiple entity descriptors. Our default implementation does not support multiple descriptors.

public class CustomSamlMetadataParser : ISamlMetadataParser
{
    private readonly ISamlMetadataParser defaultParser;

    public CustomSamlMetadataParser(ISamlMetadataParser defaultParser)
    {
        this.defaultParser = defaultParser ?? throw new ArgumentNullException(nameof(defaultParser));
    }

    public async Task<IdpOptions> Parse(string metadataXml, bool requireValidMetadataSignature)
    {
        /* If you want to edit metadataXml before parsing, please be aware that if the document is signed,
           editing the metadata will invalidate the signature. */

        var idpOptions = await defaultParser.Parse(metadataXml, requireValidMetadataSignature);

        // Edit parsed options

        return idpOptions;
    }
}

Lastly, you need to register your custom implementation in the DI container after the call to AddSaml2p.

services.AddSingleton<SamlMetadataParser>();
// Decorate SamlMetadataParser
services.AddSingleton<ISamlMetadataParser, CustomSamlMetadataParser>(serviceProvider => new CustomSamlMetadataParser(serviceProvider.GetService<SamlMetadataParser>()));