Need advice re: checking permissions !?

[William Case]

Hi Rick and thanks;

On Fri, 2009-05-15 at 11:24 -0700, Rick Stevens wrote:
> William Case wrote:
> > Hi;
> > 
> > Don't waste time on explaining how permissions work.  I have got that
> > right down to the kernel level.
> > 
> > I have a program that I suspect has a permissions bug.  I have checked
> > dmesg and nothing is said about a permissions problem.  Can I count on
> > dmesg ALWAYS being right. Or, is there another way to double check if a
> > program is getting hung up on an incorrect permission for a process and
> > what process it might be.
> 
> First off, any given program may not report errors.  Error reporting is
> up to the programmer (I'd sack any programmer working for me that
> didn't do error reporting, but that's just me).  Example:
> 
> 	int fd;
> 	fd = open("/etc/fradleybard.conf", O_RDONLY);
> 	if (fd < 0)
> 	    fprintf(stderr, "Can't open fradleybard.conf\n");
> 	exit(1);
> 
> The "if (fd < 0)" and such is completely up to me.  If I didn't include 
> it, you'd have no idea what went wrong and it wouldn't be in dmesg or
> /var/log/messages.  If it were an SELinux constraint violation, it might
> show up in an SELinux audit log.  Did you check audit.log for SELinux
> issues?  Also note that running in SELinux permissive mode is NOT the
> same as running in SELinux disabled mode--there are some things that are
> still blocked even in permissive mode.  Not a lot, but some.
> 
> You might want to see if the program in question has a debug mode or
> debug level you can set to make it more verbose about what it's doing.
> 
> If the process is hung up, try using "lsof" to get a list of the files
> that process is opening and accessing.
> 
> 	lsof -p <process-id-of-program>   OR
> 	lsof -c /regular-expresssion-matching-command-name/
> 
> (e.g. "lsof -c /gnome.*/" would list all files opened by all commands
> starting with "gnome").  Tack on a "-r n" to repeat the list every "n"
> seconds until you CTRL-C the lsof process.
> 
> "strace"ing the program in question may also give you a clue as to what
> the problem is.

You have given me a lot to work with not the least of which is the
proper terminology to dig deeper if I have to.

-- 
Regards Bill
Fedora 10, Gnome 2.24.3
Evo.2.24.5, Emacs 22.3.1