Use COM marshalling to exchange handles

[OneBlue]

Summary of the Pull Request

This change switches our HANDLE exchange logic to use COM marshalling instead of duplicating handles from / to the calling process.

This allows us to support exchanging handles with calling processes that have a higher privilege than the WSLASession.exe process, which allows for instance an elevated instance of wslc.exe to interact with a non-elevated session

PR Checklist

• Closes: Link to issue #xxx
• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated if needed and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated if needed
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

[Copilot]

Pull request overview

This PR aims to switch image load/import APIs from passing raw handle values (ULONG) to using COM/RPC handle marshalling, by introducing a WSLCHandle discriminated union and updating call sites to pass marshalled handles.

Changes:

• Introduces WSLCHandle / WSLCHandleType in the IDL and updates IWSLCSession::LoadImage / ImportImage to accept it.
• Updates session-side implementation and several test/CLI call sites to pass handles via the new helper(s).
• Adds ToCOMInputHandle / FromCOMInputHandle helpers intended to translate between HANDLE and WSLCHandle.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
test/windows/WSLCTests.cpp	Updates tests to call LoadImage/ImportImage with ToCOMInputHandle and adds a broad using namespace ...wslutil.
src/windows/wslcsession/WSLCSession.h	Updates WSLCSession method signatures to match the new handle type.
src/windows/wslcsession/WSLCSession.cpp	Updates image load/import implementation to use FromCOMInputHandle and pass the handle to relay IO.
src/windows/WslcSDK/wslcsdk.cpp	Currently stubs out SDK image load/import wrappers (returns S_OK without performing work).
src/windows/wslc/services/ImageService.cpp	Updates CLI/service-side image load to build a WSLCHandle and call LoadImage.
src/windows/service/inc/wslc.idl	Adds WSLCHandle types and changes IWSLCSession method signatures to accept them.
src/windows/common/wslutil.h / .cpp	Adds ToCOMInputHandle and FromCOMInputHandle helper APIs for the new handle path.

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated 3 comments.

Comments suppressed due to low confidence (1)

src/windows/service/inc/wslc.idl:504

• Changing WSLCBuildImageOptions.DockerfileHandle from ULONG to WSLCHandle changes the struct layout on the wire/ABI. Existing callers passing the old struct will break at runtime even if they don’t call the updated methods. Consider versioning this options struct (e.g., WSLCBuildImageOptions2) and adding a new BuildImage entry point/interface that consumes it, while keeping the original struct/method for compatibility.

typedef struct _WSLCBuildImageOptions
{
    LPCWSTR ContextPath;
    WSLCHandle DockerfileHandle;
    WSLCStringArray Tags;
    WSLCStringArray BuildArgs; // KEY=VALUE pairs passed as --build-arg to docker.
    BOOL Verbose; // Show all build progress including internal steps and all statuses.
} WSLCBuildImageOptions;

[benhillis]

Couple questions. Can we also add a test that launches a session as non-admin, then tries to attach to reuse the session as admin? I think we already have one that verifies the other way does not work (and should not).

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated 5 comments.

[Copilot]

Pull request overview

Copilot reviewed 16 out of 16 changed files in this pull request and generated 5 comments.

Comments suppressed due to low confidence (1)

src/windows/service/inc/wslc.idl:504

• Changing WSLCBuildImageOptions.DockerfileHandle from ULONG to WSLCHandle changes the struct layout/wire format used by the existing IWSLCSession::BuildImage method, which is also an ABI-breaking change for existing clients. Prefer versioning the options struct (e.g., WSLCBuildImageOptions2) and/or adding a new BuildImage2 method on a versioned session interface, keeping the original struct unchanged.

typedef struct _WSLCBuildImageOptions
{
    LPCWSTR ContextPath;
    WSLCHandle DockerfileHandle;
    WSLCStringArray Tags;
    WSLCStringArray BuildArgs; // KEY=VALUE pairs passed as --build-arg to docker.
    BOOL Verbose; // Show all build progress including internal steps and all statuses.
} WSLCBuildImageOptions;

[Copilot]

Pull request overview

Copilot reviewed 16 out of 16 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

src/windows/service/inc/wslc.idl:504

• WSLCBuildImageOptions.DockerfileHandle changed from ULONG to WSLCHandle. If this struct is part of the COM/SDK contract, changing the field type is also an ABI break for already-built clients. Consider introducing a new options struct (e.g., WSLCBuildImageOptions2) and a new BuildImage2 method on a versioned interface, rather than changing the existing struct layout in-place.

typedef struct _WSLCBuildImageOptions
{
    LPCWSTR ContextPath;
    WSLCHandle DockerfileHandle;
    WSLCStringArray Tags;
    WSLCStringArray BuildArgs; // KEY=VALUE pairs passed as --build-arg to docker.
    BOOL Verbose; // Show all build progress including internal steps and all statuses.
} WSLCBuildImageOptions;

[Copilot]

IWSLCSession's LoadImage/ImportImage/SaveImage parameter types changed from ULONG to WSLCHandle without versioning the interface UUID. This is a binary breaking change for any client compiled against the previous IDL. Please introduce a versioned interface (e.g., IWSLCSession2) for the WSLCHandle-based methods and keep the existing IWSLCSession contract stable.