From: Sam Roberts <sroberts@...>
Date: 2006-07-25T04:40:02+09:00
Subject: Re: Patch for Unix socket peer credentials

On Sat, Jul 22, 2006 at 03:54:19PM +0900, Tanaka Akira wrote:
> > Are negative values allowed on Linux? AFAICT, if the credentials aren't 
> > available on Linux, say when I check a TCPServer socket's credentials
> > after accepting a connection from another host, the system call returns
> > 0 but sets the uid & gid to -1:

Whether allowed or not by the OS, returning -1 in the hash as :uid and
:gid seems reasonable, it makes the Socket method behave like the
underlying system call, so less surprising to users, and if they want to
know what -1 means, they can read the man page for their system.

At least some binutils don't seem to think a uid can be negative,

  GNU coreutils 5.93, id.c:print_user() ... printf ("%lu", (unsigned long int) uid)


Perhaps more interesting to this list, ruby's File::chown doesn't allow -1 as a
uid or gid, though it does allow other negative values:

    File.chown(owner_int, group_int, file_name,... ) -> integer
    ...
    A +nil+ or -1 owner or group id is ignored.
    ...

root:/tmp # ruby -e'File.chown(-2, -2, "neg2")'
root:/tmp # ls -l neg2
-rw-r--r-- 1 4294967294 4294967294 0 2006-07-24 12:15 neg2
root:/tmp # ruby -e'File.chown(-1, -3, "neg2")'
root:/tmp # ls -l neg2
-rw-r--r-- 1 4294967294 4294967293 0 2006-07-24 12:15 neg2
root:/tmp # ruby -e'File.chown(-3, -1, "neg2")'
root:/tmp # ls -l neg2
-rw-r--r-- 1 4294967293 4294967293 0 2006-07-24 12:15 neg2


Maybe only nil should be ignored?

Cheers,
Sam