AesGcm support is missing

[trampster]

Steps to Reproduce

1. Try and construct a AesGcm instance
2. Notice you get a PlatformNotSupportedException

Current Behavior

AesGcm is not supported

Expected Behavior

AesGcm is part of dotnet standard 2.1 which is officially supported, so I would except this to work.

On which platforms did you notice this

Xamarin.Android

Version Used:
Xamarin.Android 10.1.4.0

[trampster]

I can confirm that the .dotnet core code for this work great on linux, I'm not sure at what level the mono project can reuse code from dotnet core, but just taking there implementation would seem like a good idea.

[trampster]

As far as I'm aware there is no platform reason this should be missing, openssl has support for AesGcm and that is what dotnet core uses successfully on linux.

[ngarside]

I ran into this issue while trying to port a .net core app to android. It's been pretty straightforward so far with the lack of aesgcm support being the only major pain point.

[trampster]

As a temporary work around I've created a OpenSSL wrapper for AesGcm, which you can find here: https://www.nuget.org/packages/Ropu.AesGcm/

However I would much rather this was implemented in mono as part of .net Standard 2.1

[ognamala]

I can confirm that this issue with also happens on iOS

at System.Security.Cryptography.AesGcm..ctor (System.Byte[] key) [0x00006] in /Library/Frameworks/Xamarin.iOS.framework/Versions/Current/src/Xamarin.iOS/mcs/class/corlib/corefx/AesGcm.cs:9

[DanGould]

I'm running into this issue too, after assuming 2.1 was supported and writing a bunch of crypto code for iOS and testing on MacOS where it fails with No usable version of libssl was found. Considering the viability of wrapping AesGcm from the browser to get it cross platform 🥴 I will consider the iOS workaround, but I'd really love and dream for this to work on android too, so mono support is ideal

[Liam2349]

Just ran into the same issue when testing a project on Android - PlatformNotSupported Exception when trying to use the AesGcm class. For example, attempting to access the AesGcm.NonceByteSizes.MaxSize property throws this exception.

I am using Xamarin.Android SDK 11.4.0.5 with Visual Studio Community 16.11.2.

I selected this class because according to the docs, Xamarin.Android 10 is .NET Standard 2.1 compliant, which I believe requires AesGcm compatibility, so I was under the impression it would work.

To anyone looking for an alternative, there is a detailed CBC-HMAC example here: https://docs.microsoft.com/en-us/dotnet/standard/security/vulnerabilities-cbc-mode

[shaiArn]

I also ran into this issue when trying to use the AesGcm class in a Unity project. I was using jose-jwt library and got a PlatformNotSupportedException when trying to use AesGcm.

I would really appreciate it if you could look into supporting AesGcm.