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[Android] Allow using installed certificates for client authentication in SslStream #103337

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simonrozsival
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@simonrozsival simonrozsival commented Jun 12, 2024

Closes #99874

This PR adds the possibility to use certificates with non-exportable private keys installed on an Android device for client authentication in SslStream/SocketsHttpHandler.

The inspiration for these changes comes from AppleCertificatePal where we allow passing in either SecCertificate or SecIdentity via the IntPtr constructor. The Android IntPtr constructor will now accept not only handles of java.security.cert.X509Certificate, but also of java.security.KeyStore.PrivateKeyEntry. This will allow the developer to pass in certificates with non-exportable private keys and use them for client authentication (see the linked issue for an example usage with KeyChain.ChoosePrivateKeyAlias).

To implement this feature, it is necessary to introduce new Java class net.dot.android.crypto.DotnetX509KeyManager. This will require follow-up work in the .NET for Android SDK code to adjust the ProGuard configuration (https://github.com/xamarin/xamarin-android/blob/7e67d2c241e561b05065f2a57ddf59093f74de58/src/Xamarin.Android.Build.Tasks/Resources/proguard_xamarin.cfg#L29).

As a follow-up to this PR, we should introduce new APIs to the Android.Security.KeyChain class in the dotnet/android repository. This will allow the developers to avoid using this low level IntPtr constructor.

/cc @karelz @vitek-karas @grendello @filipnavara @dotMorten

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Tagging subscribers to this area: @dotnet/area-system-security, @bartonjs, @vcsjones
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/azp run runtime-extra-platforms

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@simonrozsival Thank you for working on this! Very exciting. What's the easiest way for me to test this with our various PKI tests on Android?

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@dotMorten I'm not sure if there's an easy way to do it, you'll need to jump through a few hoops:

  1. build the code in this branch, you can follow https://github.com/dotnet/runtime/blob/main/docs/workflow/building/mono/README.md (alternatively I could send you the prebuilt nupkgs directly if you're OK with that, you can reach out to me via email or discord)
  2. add the local nupkg source to your MAUI app via NuGet.config
  3. follow this guide to use your locally built dev version of the runtimepack: https://github.com/xamarin/xamarin-android/blob/main/Documentation/workflow/DevelopmentTips.md?plain=1#L432
  4. use the new ctor as it's shown in the issue or in the new unit test in this PR

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dotMorten commented Jun 14, 2024

I tried this change, and it indeed addresses the issue for us without our test server and certificates. Nice work @simonrozsival (and thanks for helping getting it running).
🚢 it

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/azp run runtime-extra-platforms

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The failing tests in runtime-extra-platforms are known and unrelated (#103472)

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LGTM, a couple comments but I'm fine if we address them in a follow-up PR

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/azp run runtime-extra-platforms

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jonathanpeppers pushed a commit to dotnet/android that referenced this pull request Jun 19, 2024
Context: dotnet/runtime#103016
Context: dotnet/runtime#103337

In dotnet/runtime we are adding a few more Java classes to assist with
.NET crypto. One was added in dotnet/runtime#103016, and another may
be added in dotnet/runtime#103337.

This PR changes ProGuard to keep all of the classes in this package
rather than individually adding them.

Co-authored-by: Alexander Köplinger <[email protected]>
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Failing runtime-extra-platforms tests are unrelated

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LGTM. Would X509Certificate2.HasPrivateKey return right value?

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Would X509Certificate2.HasPrivateKey return right value?

That is asserted here:

And the Android X.509 PAL changes look sensible.

public bool HasPrivateKey => _privateKey is not null || _keyStorePrivateKeyEntry is not null;

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@wfurt yes, the AndroidCertificatePal class will return the right value whether it's created the previously existing way or the new way with KeyStore.PrivateKeyEntry.

@simonrozsival simonrozsival merged commit 83031f1 into dotnet:main Jun 19, 2024
127 of 136 checks passed
@@ -32,6 +32,31 @@ internal static byte[] X509Encode(SafeX509Handle x)

return encoded;
}
[LibraryImport(Libraries.AndroidCryptoNative, EntryPoint = "AndroidCryptoNative_X509IsKeyStorePrivateKeyEntry")]
[return: MarshalAs(UnmanagedType.U1)]
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@simonrozsival the native code returns int32_t here so we should change this to UnmanagedType.Bool (4 bytes), or change the native code to use a C bool which is 1 byte. We seem to be using both variants in the Android crypto imports...

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At least in the Linux and MacOS Desktop PALs, we try to use int32_t and not a C bool since there is no guarantee by the C standard that it is exactly one byte.

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oh, thanks for pointing that out!

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@github-actions github-actions bot locked and limited conversation to collaborators Jul 23, 2024
@karelz karelz added this to the 9.0.0 milestone Jul 29, 2024
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Android: Installed X509 certificates can't be used with SSL authentication
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