[apparmor] [PATCH 20/31] parser: Remove prints and exits from features code

[Tyler Hicks]

On 2015-02-27 11:08:28, Tyler Hicks wrote:
> On 2015-01-27 10:11:48, John Johansen wrote:
> > On 01/23/2015 11:39 AM, Tyler Hicks wrote:
> > > On 2015-01-23 19:44:27, Christian Boltz wrote:
> > >> Hello,
> > >>
> > >> Am Donnerstag, 22. Januar 2015 schrieb Steve Beattie:
> > >>> On Thu, Jan 22, 2015 at 04:23:00PM -0600, Tyler Hicks wrote:
> > >>>> We don't know what a program linking to libapparmor will do with
> > >>>> stdout/stderr so I don't know if debug logging to those streams is
> > >>>> helpful.
> > >>
> > >> stderr doesn't sound too bad, but might be lost in some situations (like 
> > >> starting a program via its desktop icon)
> > >>
> > >>>> Maybe in the near future we could add a debug build option to
> > >>>> libapparmor and have it support an env variable that specifies a
> > >>>> file
> > >>>> path to open and log debug messages to?
> > >>>
> > >>> That would be a very nice improvement indeed.
> > >>
> > >> Would it also be a secure improvement? ;-)
> > >>
> > >> Basically that feature would allow to overwrite any file if an attacker 
> > >> is able to inject an environment variable...
> > > 
> > > Debug builds of programs/libraries aren't intended to be installed on
> > > production systems. Debug output from libapparmor would only be built
> > > and enabled in debug builds of libapparmor.
> > > 
> > 
> > So I like the idea of an environment variable, but I think the debug
> > output should (if built) dump to stderr.
> > 
> > I'd also like to see a better integration of DEBUG build controls,
> > or at least documentation of the different controls and build options.
> > But of course that can come in some separate patches.
> > 
> > For now I'd just like to not lose the limited debug that is in the code.
> 
> I wanted to give you a quick update on what my plans are here. The code
> that is being moved from the parser to libapparmor has calls to PERROR()
> and PDEBUG(). Here's my thoughts on how to handle them in libapparmor:
> 
> 
>  * PDEBUG()
>    - Compiled out unless libapparmor is built with --enable-debug
>    - Prints to stderr if libapparmor is built with --enable-debug and
>      the LIBAPPARMOR_DEBUG environment variable is set

One correction. To match the current PDEBUG() implementation in the
parser, the libapparmor PDEBUG() would need to print to stdout instead
of stderr.

Tyler

>  * PERROR()
>    - Always built and uses syslog(LOG_ERR, ...) by default
>    - Uses syslog(LOG_PERROR, ...) if libapparmor is built with
>      --enable-debug and the LIBAPPARMOR_DEBUG environment variable is
>      set
> 
> Tyler



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