[DGD] Re: Bad plumbing leaks silver lining

[Shentino]

It seems that Dworkin has just changed things...please ignore any part
of the previous message that is no longer applicable.

On 8/3/06, Shentino <shentino at gmail.com> wrote:
> Ok, I tried to be oh so clever and thought it might be a nice secure
> way to have communications with an external process...
>
> By using a named pipe.
>
> My plan was to spawn a subshell in my DGD bootscript that would read
> from the pipe and execute shell commands.  The fifo would be in
> ~System/extern/fifo/sh.  Klib restrictions would forbid anyone from
> tampering with the shell's input and injecting a trojan, and plain old
> Unix style file permissions would protect the pipe from trojans
> outside the mudlib.
>
> Alas, DGD thinks it has to seek to zero on a file, and chokes because
> seeking on a pipe returns -ESPIPE (or something like that...confirmed
> with strace).  What's really weird is that it worked...ONCE.
>
> All was not lost, as the fifo was still OPENED, which had the nice
> side effect of signalling the process at the other end of the pipe,
> and even though DGD failed to actually write anything, the "open for
> write mode" was enough to unblock the other process, a waiting
> subshell, so that it could do its post-init stuff (like spawning
> utility daemons).  So while I couldn't use the fifo to transfer data,
> it still worked nicely as a semaphore.
>
> Just thought I'd post this, in case anyone finds a use for it.  It
> seems particularly clever.
>
> Obviously, this will only work on systems that support POSIX compliant
> named pipes, aka fifos.
>