Re: LOCAL_CREDS and unix domain sockets


On Tue, 5 Feb 2008, Zane C.B. wrote:

On Tue, 5 Feb 2008 13:21:10 -0200 Fernando Schapachnik <fschapachnik@xxxxxxxxxxxx> wrote:

En un mensaje anterior, Zane C.B. escribió:
With unix domain sockets, unix(4), are LOCAL_CREDS actually supported or not?

I've been trying to fetch this from within a Perl script using 'my $local_creds=$some_connection->sockopt(LOCAL_CREDS)', but all I keep getting is a undefined variable in return, as if fetching it is not supported.

Maybe LOCAL_CREDS is not defined. Maybe LOCAL_CREDS() (perl notation for constants) works?

Hmm, that turns out to be the point. I've checked and it is not in '/usr/local/lib/perl5/5.8.8/mach/Socket.pm'.

I think my understanding if when I originally posted the email was wrong as well. I need to set the socket option LOCAL_CREDS and fetch them using recvmsg.

Can some one please verify my understanding of this is right?

Yes, that's correct -- you use setsockopt() to request that an SCM_CREDS control message be attached to either every message coming in on the socket (SOCK_DGRAM) or the first message arriving on accepted sockets (listen SOCK_STREAM). You can then use recvmsg to get the credential information.

Alternatively, LOCAL_PEERCRED allows you to query the credential at any time using a socket option for a stream socket (keep in mind that the credential is cached when the connection is made, and might not reflect the credential of a process sending on the socket if it's been inherited/passed).

Robert N M Watson
Computer Laboratory
University of Cambridge_______________________________________________
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