System.Security.Cryptography.Xml feature requests

[krwq]

This is an issue to collect all the feature requests after we finish stabilizing.
Some of them might be already implemented on Mono and might need a port.
cc: @anthonylangsworth @tintoy @peterwurzinger

Feature requests:

• Add support for adding algorithms

Features resulting from failing tests: (there is no compat break between Desktop so marking as future) - they can be possibly Mono bugs

• SignedXmlTest.DataReferenceToNonDataObject (There is an existing test with this - currently this is also not working on Desktop but likely is on Mono)
• SignedXmlTest.GetIdElement_Null (throws ArgumentNullException on Desktop, seems to be valid on Mono)
• SignedXmlTest.HmacMustBeMultipleOfEightBits (Desktop does not throw, Mono throws CryptographicException)
• SignedXmlTest.VerifyHMAC_ZeroLength (Desktop does not throw, Mono throws CryptographicException)
• SignedXmlTest.VerifyHMAC_SmallerThanMinimumLength (Mono has it with category "NotWorking") - verify if should be fixed
• SignedXmlTest.VerifyHMAC_MinimumLength (Failing also on Desktop - seems to be passing on Mono)
• SignedXmlTest.VerifyHMAC_SmallerHalfLength (Failing also on Desktop - seems to be passing on Mono)
• SignedXmlTest.VerifyHMAC_HalfLength (Failing also on Desktop - seems to be passing on Mono)
• SignedXmlTest.VerifyHMAC_HMACOutputLength_Signature_Mismatch (Failing also on Desktop - seems to be passing on Mono)
• SignedXmlTest.VerifyHMAC_HMACOutputLength_Invalid (Failing also on Desktop - seems to be passing on Mono)
• XmlDsigExcC14NWithCommentsTransformTest.LoadInputAsXmlNodeList, LoadInputAsXmlNodeList2 (Failing also on Desktop - seems to be working on Mono)
• EncryptedXmlTest.GetDecryptionIV_StringNull (Failing also on Desktop - seems to be working on Mono) - Fix EncryptedXmlTest.GetDecryptionIV_StringNull and expand ExcryptedXmlTest corefx#17221
• SignedInfoTest.GetXmlWithSetProperty (Failing also on Desktop - seems to be working on Mono)

[karelz]

@krwq can you please triage the issue right away? (issue type, milestone) Thanks!

[karelz]

See details in https://github.com/dotnet/corefx/issues/16594#issuecomment-298421865 on limitations of adding APIs into SignedXml/EncryptedXml - if we want to reboot the API surface and make it truly modern, we will have to create new package, which does not exchange types with .NET Framework inbox SignedXml/EncryptedXml. It may still compile from same source code though.

[bartonjs]

It's been 7 years since this TODO list made progress. It's apparently about as done as it's ever going to get.