Bug 47500 – Need a way to pass HANDLEs between processes on Windows

• Component: WebKit2
• Status: RESOLVED DUPLICATE

[Adam Roben (:aroben)]

In order to implement WebKit2's SharedMemory class (bug 47499), we'll need a way to pass HANDLEs (specifically, those representing file-mapping objects) across processes.

[Adam Roben (:aroben)]

In order to pass a HANDLE between processes, we'll need to call ::DuplicateHandle to copy the handle into the target process. But doing this requires knowing what the target process is, which is not known at argument-encoding time.

Anders suggests that we use CoreIPC::Attachment for this. Specifically, we'd:

A1) Make CoreIPC::Connection perform a handshake that exchanges process HANDLEs between the two ends of the connection (on Vista and newer we could perhaps use ::GetNamedPipeClientProcessId/::GetNamedPipeServerProcessId to simplify this)
A2) Use the process HANDLE received in the handshake to call ::DuplicateHandle when sending the message

I think another option that wouldn't require the handshake is:

B1) Call ::DuplicateHandle to duplicate the HANDLE in the source process at argument-encoding time
B2) Send both the HANDLE and the source process's PID in the message to the target process
B3) When the message is received in the target process, call ::DuplicateHandle to copy the handle into the target process and pass DUPLICATE_CLOSE_SOURCE to close the HANDLE the source process made in (B1)

I'm not positive that the ::DuplicateHandle call in (B3) will actually succeed, however. Maybe Windows doesn't allow it to be used like this.

[Adam Roben (:aroben)]

<rdar://problem/8536804>

[Adam Roben (:aroben)]

*** This bug has been marked as a duplicate of bug 47499 ***