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Enable opt-in R8 JNI name obfuscation for CoreCLR and NativeAOT #12575

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Enable opt-in R8 JNI name obfuscation for CoreCLR and NativeAOT #12575

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5452258
Prototype rewriting JNI names from R8 mappings
simonrozsival Aug 28, 2026
f442d93
Prototype two-pass R8 JNI rewriting
simonrozsival Aug 31, 2026
ff9752f
Preserve final R8 shrinking and ACW entry points
simonrozsival Aug 31, 2026
eacacea
Preserve NativeAOT runtime JNI names
simonrozsival Aug 31, 2026
e7213d3
Rewrite trimmable typemap JNI metadata
simonrozsival Aug 31, 2026
3fe7c22
Validate final R8 JNI mappings
simonrozsival Aug 31, 2026
4496455
Validate final R8 JNI reachability
simonrozsival Aug 31, 2026
4064908
Scan linked assemblies for JNI reachability
simonrozsival Aug 31, 2026
569adaa
Fix Proguard configuration test line endings
simonrozsival Aug 31, 2026
fa5b793
Harden R8 JNI rewrite incrementality
simonrozsival Aug 31, 2026
0a517c7
Harden R8 JNI name obfuscation
simonrozsival Sep 1, 2026
23fd224
Fix R8 JNI review findings
simonrozsival Sep 1, 2026
5f55071
Honor R8 JNI opt-in with NativeAOT defaults
simonrozsival Sep 1, 2026
ac2b305
Avoid R8 reachability name collisions
simonrozsival Sep 1, 2026
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11 changes: 11 additions & 0 deletions Documentation/docs-mobile/building-apps/build-properties.md
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Expand Up @@ -465,6 +465,17 @@ removing the existing one(s) and adding your own AOT profiles.

This property is `False` by default.

## AndroidEnableR8JniNameObfuscation

A boolean property that enables R8 obfuscation of Java type, method, and field names
referenced by managed JNI metadata. The build uses an R8-generated mapping to rewrite
managed assemblies before trimming or NativeAOT compilation, then applies the same
mapping during the final R8 invocation.

This property requires `AndroidLinkTool=r8`,
`AndroidTypeMapImplementation=trimmable`, and either NativeAOT or CoreCLR with
`PublishTrimmed=true`.
The default value is `False`.

## AndroidEnableRestrictToAttributes

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67 changes: 63 additions & 4 deletions ...sks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.CoreCLR.targets
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Expand Up @@ -5,10 +5,11 @@

<PropertyGroup>
<_TrimmableRuntimeProviderJavaName Condition=" '$(_TrimmableRuntimeProviderJavaName)' == '' ">mono.MonoRuntimeProvider</_TrimmableRuntimeProviderJavaName>
<_CompileToDalvikDependsOnTargets>$(_CompileToDalvikDependsOnTargets);_GenerateProguardConfiguration</_CompileToDalvikDependsOnTargets>
</PropertyGroup>

<PropertyGroup>
<_GenerateProguardAfterTargets Condition=" '$(_GenerateProguardAfterTargets)' == '' ">ILLink</_GenerateProguardAfterTargets>
<_GenerateProguardAfterTargets Condition=" '$(_GenerateProguardAfterTargets)' == '' ">_RunILLink</_GenerateProguardAfterTargets>
</PropertyGroup>

<!-- Add TypeMap DLLs to ILLink input. ILLink natively understands TypeMapAttribute<T>. -->
Expand All @@ -23,6 +24,57 @@
</ItemGroup>
</Target>

<Target Name="_AndroidRewriteJniNamesBeforeILLinkInputs"
Condition=" '$(_AndroidEnableR8JniNameRewriting)' == 'true' "
DependsOnTargets="_AddTrimmableTypeMapToLinker;_AndroidGenerateR8JniSeedMapping">
<PropertyGroup>
<_AndroidR8JniRewrittenAssemblyDirectory>$(IntermediateOutputPath)r8-jni-rewritten/</_AndroidR8JniRewrittenAssemblyDirectory>
<_AndroidR8JniRewriteStamp>$(_AndroidStampDirectory)_AndroidRewriteJniNamesBeforeILLink.stamp</_AndroidR8JniRewriteStamp>
</PropertyGroup>
<ItemGroup>
<_AndroidR8JniOriginalManagedAssembly Remove="@(_AndroidR8JniOriginalManagedAssembly)" />
<_AndroidR8JniHashedManagedAssembly Remove="@(_AndroidR8JniHashedManagedAssembly)" />
<_AndroidR8JniRewrittenManagedAssembly Remove="@(_AndroidR8JniRewrittenManagedAssembly)" />
<_AndroidR8JniExpectedRewriteOutput Remove="@(_AndroidR8JniExpectedRewriteOutput)" />
<_AndroidR8JniMissingRewriteOutput Remove="@(_AndroidR8JniMissingRewriteOutput)" />
<_AndroidR8JniOriginalManagedAssembly Include="@(ManagedAssemblyToLink)" />
</ItemGroup>
<ComputeHash Source="@(_AndroidR8JniOriginalManagedAssembly)">
<Output TaskParameter="Output" ItemName="_AndroidR8JniHashedManagedAssembly" />
</ComputeHash>
<ItemGroup>
<_AndroidR8JniRewrittenManagedAssembly Include="@(_AndroidR8JniHashedManagedAssembly->'$(_AndroidR8JniRewrittenAssemblyDirectory)%(Hash)/%(Filename)%(Extension)')" />
<_AndroidR8JniExpectedRewriteOutput Include="@(_AndroidR8JniRewrittenManagedAssembly);$(_AndroidR8JniRewriteManifest)" />
<_AndroidR8JniMissingRewriteOutput Include="@(_AndroidR8JniExpectedRewriteOutput)" Condition="!Exists('%(Identity)')" />
</ItemGroup>
<Delete Files="$(_AndroidR8JniRewriteStamp)" Condition=" '@(_AndroidR8JniMissingRewriteOutput->Count())' != '0' " />
</Target>

<Target Name="_AndroidRewriteJniNamesBeforeILLink"
Condition=" '$(_AndroidEnableR8JniNameRewriting)' == 'true' "
AfterTargets="PrepareForILLink"
BeforeTargets="_RunILLink"
DependsOnTargets="_AndroidRewriteJniNamesBeforeILLinkInputs"
Inputs="@(_AndroidR8JniHashedManagedAssembly);$(_AndroidR8JniSeedMapping)"
Outputs="$(_AndroidR8JniRewriteStamp)">
<RewriteJniNamesForR8
SourceFiles="@(_AndroidR8JniHashedManagedAssembly)"
DestinationFiles="@(_AndroidR8JniRewrittenManagedAssembly)"
MappingFile="$(_AndroidR8JniSeedMapping)"
RewriteManifestFile="$(_AndroidR8JniRewriteManifest)" />
<Touch Files="$(_AndroidR8JniRewriteStamp)" AlwaysCreate="true" />
<ItemGroup>
<ResolvedFileToPublish Remove="@(_AndroidR8JniHashedManagedAssembly)" />
<ResolvedFileToPublish Include="@(_AndroidR8JniRewrittenManagedAssembly)" />
<ManagedAssemblyToLink Remove="@(ManagedAssemblyToLink)" />
<ManagedAssemblyToLink Include="@(_AndroidR8JniRewrittenManagedAssembly)" />
<FileWrites Include="@(_AndroidR8JniRewrittenManagedAssembly)" />
<FileWrites Include="$(_AndroidR8JniRewriteStamp)" />
<_AndroidR8JniExpectedRewriteOutput Remove="@(_AndroidR8JniExpectedRewriteOutput)" />
<_AndroidR8JniMissingRewriteOutput Remove="@(_AndroidR8JniMissingRewriteOutput)" />
</ItemGroup>
</Target>

<!-- Pass TypeMap entry assembly name to ILLink -->
<Target Name="_ConfigureTrimmableTypeMapForLinker"
BeforeTargets="PrepareForILLink;_RunILLink"
Expand All @@ -42,12 +94,19 @@

<Target Name="_GenerateProguardConfiguration"
AfterTargets="_PrepareLinkedAssembliesForProguard"
DependsOnTargets="_PrepareLinkedAssembliesForProguard"
Condition=" '$(PublishTrimmed)' == 'true' and '$(_ProguardProjectConfiguration)' != '' "
Inputs="@(_LinkedAssemblyForProguard)"
Outputs="$(_ProguardProjectConfiguration)">
Inputs="@(_LinkedAssemblyForProguard);$(_AndroidR8JniSeedMapping);$(_AndroidR8JniRewriteManifest)"
Outputs="$(_ProguardProjectConfiguration);$(_AndroidR8JniReachabilityManifest)">
<GenerateProguardConfiguration
LinkedAssemblies="@(_LinkedAssemblyForProguard)"
OutputFile="$(_ProguardProjectConfiguration)" />
OutputFile="$(_ProguardProjectConfiguration)"
R8MappingFile="$(_AndroidR8JniSeedMapping)"
R8RewriteManifestFile="$(_AndroidR8JniRewriteManifest)"
R8ReachabilityManifestFile="$(_AndroidR8JniReachabilityManifest)" />
<ItemGroup>
<FileWrites Include="$(_AndroidR8JniReachabilityManifest)" Condition=" '$(_AndroidR8JniReachabilityManifest)' != '' " />
</ItemGroup>
</Target>

<Target Name="_ComputePostTrimTrimmableTypeMapInputs"
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68 changes: 64 additions & 4 deletions ...s/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.NativeAOT.targets
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Expand Up @@ -19,7 +19,6 @@
<_AndroidBuildRuntimeIdentifiersInParallel
Condition=" ('$(_AndroidTrimmableTypemapTrimJavaCode)' == 'true' or '$(IlcGenerateDgmlFile)' == 'true') and '$(_AndroidBuildRuntimeIdentifiersInParallel)' == '' ">false</_AndroidBuildRuntimeIdentifiersInParallel>
<_TrimmableRuntimeProviderJavaName Condition=" '$(_TrimmableRuntimeProviderJavaName)' == '' ">net.dot.jni.nativeaot.NativeAotRuntimeProvider</_TrimmableRuntimeProviderJavaName>
<AndroidLinkTool Condition=" '$(AndroidLinkTool)' == '' ">r8</AndroidLinkTool>
<AndroidDexTool Condition=" '$(AndroidLinkTool)' == 'r8' ">d8</AndroidDexTool>
<AndroidEnableProguard Condition=" '$(AndroidLinkTool)' != '' ">True</AndroidEnableProguard>
<AndroidCreateProguardMappingFile Condition=" '$(AndroidCreateProguardMappingFile)' == '' and '$(AndroidLinkTool)' == 'r8' ">True</AndroidCreateProguardMappingFile>
Expand Down Expand Up @@ -73,6 +72,64 @@
</ItemGroup>
</Target>

<Target Name="_AndroidRewriteJniNamesBeforeIlcInputs"
Condition=" '$(_AndroidEnableR8JniNameRewriting)' == 'true' "
DependsOnTargets="_AndroidGenerateR8JniSeedMapping">
<PropertyGroup>
<_AndroidR8JniRewrittenAssemblyDirectory>$(IntermediateOutputPath)r8-jni-rewritten/</_AndroidR8JniRewrittenAssemblyDirectory>
<_AndroidR8JniRewriteStamp>$(_AndroidStampDirectory)_AndroidRewriteJniNamesBeforeIlc.stamp</_AndroidR8JniRewriteStamp>
</PropertyGroup>
<ItemGroup>
<_AndroidR8JniIlcAssembly Remove="@(_AndroidR8JniIlcAssembly)" />
<_AndroidR8JniHashedIlcAssembly Remove="@(_AndroidR8JniHashedIlcAssembly)" />
<_AndroidR8JniRewrittenIlcAssembly Remove="@(_AndroidR8JniRewrittenIlcAssembly)" />
<_AndroidR8JniExpectedRewriteOutput Remove="@(_AndroidR8JniExpectedRewriteOutput)" />
<_AndroidR8JniMissingRewriteOutput Remove="@(_AndroidR8JniMissingRewriteOutput)" />
<_AndroidR8JniIlcAssembly Include="@(ManagedBinary)">
<R8JniInputKind>ManagedBinary</R8JniInputKind>
</_AndroidR8JniIlcAssembly>
<_AndroidR8JniIlcAssembly Include="@(IlcReference)">
<R8JniInputKind>IlcReference</R8JniInputKind>
</_AndroidR8JniIlcAssembly>
<_AndroidR8JniIlcAssembly Remove="@(_AndroidR8JniIlcAssembly)" Condition=" '%(Extension)' != '.dll' " />
</ItemGroup>
<ComputeHash Source="@(_AndroidR8JniIlcAssembly)">
<Output TaskParameter="Output" ItemName="_AndroidR8JniHashedIlcAssembly" />
</ComputeHash>
<ItemGroup>
<_AndroidR8JniRewrittenIlcAssembly Include="@(_AndroidR8JniHashedIlcAssembly->'$(_AndroidR8JniRewrittenAssemblyDirectory)%(Hash)/%(Filename)%(Extension)')" />
<_AndroidR8JniExpectedRewriteOutput Include="@(_AndroidR8JniRewrittenIlcAssembly);$(_AndroidR8JniRewriteManifest)" />
<_AndroidR8JniMissingRewriteOutput Include="@(_AndroidR8JniExpectedRewriteOutput)" Condition="!Exists('%(Identity)')" />
</ItemGroup>
<Delete Files="$(_AndroidR8JniRewriteStamp)" Condition=" '@(_AndroidR8JniMissingRewriteOutput->Count())' != '0' " />
</Target>

<Target Name="_AndroidRewriteJniNamesBeforeIlc"
Condition=" '$(_AndroidEnableR8JniNameRewriting)' == 'true' "
BeforeTargets="WriteIlcRspFileForCompilation"
DependsOnTargets="_AndroidRewriteJniNamesBeforeIlcInputs"
Inputs="@(_AndroidR8JniHashedIlcAssembly);$(_AndroidR8JniSeedMapping)"
Outputs="$(_AndroidR8JniRewriteStamp)">
<RewriteJniNamesForR8
SourceFiles="@(_AndroidR8JniHashedIlcAssembly)"
DestinationFiles="@(_AndroidR8JniRewrittenIlcAssembly)"
MappingFile="$(_AndroidR8JniSeedMapping)"
RewriteManifestFile="$(_AndroidR8JniRewriteManifest)" />
<Touch Files="$(_AndroidR8JniRewriteStamp)" AlwaysCreate="true" />
<ItemGroup>
<ManagedBinary Remove="@(ManagedBinary)" />
<ManagedBinary Include="@(_AndroidR8JniRewrittenIlcAssembly)" Condition=" '%(R8JniInputKind)' == 'ManagedBinary' " />
<IlcCompileInput Remove="@(IlcCompileInput)" />
<IlcCompileInput Include="@(ManagedBinary)" />
<IlcReference Remove="@(IlcReference)" />
<IlcReference Include="@(_AndroidR8JniRewrittenIlcAssembly)" Condition=" '%(R8JniInputKind)' == 'IlcReference' " />
<FileWrites Include="@(_AndroidR8JniRewrittenIlcAssembly)" />
<FileWrites Include="$(_AndroidR8JniRewriteStamp)" />
<_AndroidR8JniExpectedRewriteOutput Remove="@(_AndroidR8JniExpectedRewriteOutput)" />
<_AndroidR8JniMissingRewriteOutput Remove="@(_AndroidR8JniMissingRewriteOutput)" />
</ItemGroup>
</Target>

<!--
Force the typemap to be generated in the OUTER build (the build that is not an inner
per-RID build, i.e. '$(_OuterIntermediateOutputPath)' == '') before _ResolveAssemblies
Expand Down Expand Up @@ -231,15 +288,18 @@
<Target Name="_GenerateTrimmableTypeMapProguardConfiguration"
DependsOnTargets="_WriteTrimmableNativeAotProguardConfigurationInputs;_CollectTrimmableNativeAotDgmlFiles"
Condition=" '$(PublishTrimmed)' == 'true' and '$(_ProguardProjectConfiguration)' != '' "
Inputs="$(_TrimmableNativeAotProguardConfigurationInputsStamp);@(_TrimmableNativeAotDgmlFiles);$(IntermediateOutputPath)acw-map.txt"
Outputs="$(_ProguardProjectConfiguration)">
Inputs="$(_TrimmableNativeAotProguardConfigurationInputsStamp);@(_TrimmableNativeAotDgmlFiles);$(IntermediateOutputPath)acw-map.txt;$(_AndroidR8JniSeedMapping)"
Outputs="$(_ProguardProjectConfiguration);$(_AndroidR8JniReachabilityManifest)">
<GenerateNativeAotProguardConfiguration
NativeAotDgmlFiles="@(_TrimmableNativeAotDgmlFiles)"
AcwMapFile="$(IntermediateOutputPath)acw-map.txt"
TrimJavaCallableWrappers="$(_AndroidTrimmableTypemapTrimJavaCode)"
OutputFile="$(_ProguardProjectConfiguration)" />
OutputFile="$(_ProguardProjectConfiguration)"
R8MappingFile="$(_AndroidR8JniSeedMapping)"
R8ReachabilityManifestFile="$(_AndroidR8JniReachabilityManifest)" />
<ItemGroup>
<FileWrites Include="$(_ProguardProjectConfiguration)" />
<FileWrites Include="$(_AndroidR8JniReachabilityManifest)" Condition=" '$(_AndroidR8JniReachabilityManifest)' != '' " />
</ItemGroup>
</Target>

Expand Down
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