Re: [PATCH 00/10] [RFC] Simple IPC Mechanism

"Jeff Hostetler via GitGitGadget" [off-list ref] writes:

This series introduces a multi-threaded IPC mechanism called "Simple IPC".
This is a library-layer feature to make it easy to create very long running
daemon/service applications and for unrelated Git commands to communicate
with them. Communication uses pkt-line messaging over a Windows named pipe
or Unix domain socket.

On the server side, Simple IPC implements a (platform-specific) connection
listener and worker thread-pool to accept and handle a series of client
connections. The server functionality is completely hidden behind the
ipc_server_run() and ipc_server_run_async() APIs. The daemon/service
application only needs to define an application-specific callback to handle
client requests.

Note that Simple IPC is completely unrelated to the long running process
feature (described in sub-process.h) where the lifetime of a "sub-process"
child is bound to that of the invoking parent process and communication
occurs over the child's stdin/stdout.

Simple IPC will serve as a basis for a future builtin FSMonitor daemon
feature.

What kind of security implications does this bring into the system?

Can a Simple IPC daemon be connected by any client?  How does the
daemon know that the other side is authorized to make requests?
When a git binary acting as client connect to whatever happens to be
listening to the well-known location, how does it know if the other
side is the daemon it wanted to talk to and not a malicious MITM or
other impersonator?

Or is this to be only used for "this is meant to be used to give
read-only access to data that is public anyway" kind of daemon,
e.g. "git://" transport that serves clones and fetches?

Or is this meant to be used on client machines where all the
processes are assumed to be working for the end user, so it is OK to
declare that anything will go (good old DOS mental model?)

I know at the Mechanism level we do not yet know how it will be
used, but we cannot retrofit sufficient security, so it would be
necessary to know answers to these questions.

Thanks.