[SSSD] [PATCH] sss_client: Return a different error when sssd is not running

Lukas Slebodnik lslebodn at redhat.com
Fri Dec 5 15:48:47 UTC 2014


On (05/12/14 16:22), Jakub Hrozek wrote:
>On Mon, Nov 24, 2014 at 02:14:27PM +0100, Lukas Slebodnik wrote:
>> On (24/11/14 10:47), Jakub Hrozek wrote:
>> >On Mon, Nov 24, 2014 at 09:51:58AM +0100, Lukas Slebodnik wrote:
>> >> On (22/11/14 17:25), Jakub Hrozek wrote:
>> >> >On Sat, Nov 22, 2014 at 05:12:09PM +0100, Jakub Hrozek wrote:
>> >> >> On Tue, Nov 18, 2014 at 12:25:40PM +0100, Lukas Slebodnik wrote:
>> >> >> > On (18/11/14 12:22), Lukas Slebodnik wrote:
>> >> >> > >On (13/11/14 10:08), Simo Sorce wrote:
>> >> >> > >>On Thu, 13 Nov 2014 10:44:45 +0100
>> >> >> > >>Jakub Hrozek <jhrozek at redhat.com> wrote:
>> >> >> > >>
>> >> >> > >>> On Wed, Nov 12, 2014 at 08:04:46PM -0500, Simo Sorce wrote:
>> >> >> > >>> > On Wed, 12 Nov 2014 16:36:00 +0100
>> >> >> > >>> > Lukas Slebodnik <lslebodn at redhat.com> wrote:
>> >> >> > >>> > 
>> >> >> > >>> > > On (12/11/14 10:00), Simo Sorce wrote:
>> >> >> > >>> > > >I would create a helper function to be called on return that
>> >> >> > >>> > > >transforms the error accordingly. This will allow to write the
>> >> >> > >>> > > >code _and_ the comment once.
>> >> >> > >>> > > >
>> >> >> > >>> > > In this case, Stephan's patch is better
>> >> >> > >>> > > https://bugzilla.redhat.com/attachment.cgi?id=788567
>> >> >> > >>> > 
>> >> >> > >>> > Yes, this is a valid alternative.
>> >> >> > >>> > 
>> >> >> > >>> > > >The comment should be changed to something like this in either
>> >> >> > >>> > > >case: /* When sssd is stopped return a safe error code as if sss
>> >> >> > >>> > > >was not configured at all in nsswitch. This prevents bogus
>> >> >> > >>> > > >errors from causing issues in applications, before sssd starts
>> >> >> > >>> > > >or if it fails to respond. */
>> >> >> > >>> > > >
>> >> >> > >>> > > >No need to mention that sss is by default in nsswitch, as it is
>> >> >> > >>> > > >not in all distributions and it really is inconsequential, the
>> >> >> > >>> > > >same behaviour change hleps when sss is not the default but is
>> >> >> > >>> > > >has been manually added and sssd is stopped or not started yet
>> >> >> > >>> > > >(for example during boot).
>> >> >> > >>> > > nss-pam-ldapd has the same behaviour in the same situation.
>> >> >> > >>> > > Will we patch it as well? It's very likely we won't.
>> >> >> > >>> > 
>> >> >> > >>> > Sorry, I do not see how that matters :)
>> >> >> > >>> > 
>> >> >> > >>> > > The biggest problem is that sss is by default in nsswitch on
>> >> >> > >>> > > fedora/rhel>=7 due to glibc caching and problem with GNOME,
>> >> >> > >>> > > a) sssd-client is installed by default on this platforms.
>> >> >> > >>> > > b) sssd need't be configured by default and in most cases won't be
>> >> >> > >>> > >     => sssd cannot run
>> >> >> > >>> > > c) glibc developers don't want to adjust the error return code in
>> >> >> > >>> > > glibc
>> >> >> > >>> > > 
>> >> >> > >>> > > As a result of this, we need to patch sssd.
>> >> >> > >>> > > I would say we should patch sssd just in downstream and
>> >> >> > >>> > > Stephan's patch works well. I tested it.
>> >> >> > >>> > 
>> >> >> > >>> > Ok, then let's go with Stephen's patch.
>> >> >> > >>> > 
>> >> >> > >>> > Simo.
>> >> >> > >>> > 
>> >> >> > >>> 
>> >> >> > >>> I don't personally mind whether we use Lukas' or Stephen's patch but I
>> >> >> > >>> would /strongly/ prefer the patch to be pushed upstream.
>> >> >> > >>> 
>> >> >> > >>> Non-upstream patches should be considered valid only as a temporary
>> >> >> > >>> workarounds..
>> >> >> > >>
>> >> >> > >>I was not aware the patch was not proposed for upstream. I strongly
>> >> >> > >>disagree on this kind of patches being platform specific too.
>> >> >> > >>
>> >> >> > >New version of patch is attached.
>> >> >> > >
>> >> >> > Ups, one more time.
>> >> >> > 
>> >> >> > LS
>> >> >> 
>> >> >> > From eb617a980d50c7081ecb6eda0d489fc0eb8963f7 Mon Sep 17 00:00:00 2001
>> >> >> > From: Lukas Slebodnik <lslebodn at redhat.com>
>> >> >> > Date: Tue, 18 Nov 2014 12:02:10 +0100
>> >> >> > Subject: [PATCH] sss_client: Work around glibc bug
>> >> >> > 
>> >> >> > glibc is inconsistent with how it treats and returns NSS_STATUS_UNAVAIL.
>> >> >> > 
>> >> >> > The sss nss plugin is present in nsswitch by default on some platforms
>> >> >> > due to glibc caching and problem with long living applications (e.g. GNOME).
>> >> >> > The SSSD nss plugin should behave as if it was functioning but had no data even
>> >> >> > thought sssd is not running. The errors have to be passed from nss plugin up to
>> >> >> > the user with minimal moidiffication.
>> >> >> > 
>> >> >> > Thanks to Stephen Gallagher for initial patch.
>> >> >> > 
>> >> >> > Resolves:
>> >> >> > https://fedorahosted.org/sssd/ticket/2439
>> >> >> > ---
>> >> >> >  src/conf_macros.m4      | 13 +++++++++++++
>> >> >> >  src/sss_client/common.c | 10 ++++++++++
>> >> >> >  2 files changed, 23 insertions(+)
>> >> >> > 
>> >> >> > diff --git a/src/conf_macros.m4 b/src/conf_macros.m4
>> >> >> > index fbee81f56e484b618379f7c987ecee50ae48917e..bb283ef248ee017fd608bd85cc68666db0300fd9 100644
>> >> >> > --- a/src/conf_macros.m4
>> >> >> > +++ b/src/conf_macros.m4
>> >> >> > @@ -708,6 +708,19 @@ AC_ARG_ENABLE([dbus-tests],
>> >> >> >                [build_dbus_tests=yes])
>> >> >> >  AM_CONDITIONAL([BUILD_DBUS_TESTS], [test x$build_dbus_tests = xyes])
>> >> >> >  
>> >> >> > +AC_ARG_ENABLE([sss-default-nss-plugin],
>> >> >> > +              [AS_HELP_STRING([--enable-sss-default-nss-plugin],
>> >> >> > +                              [This option change standard behaviour of sss nss
>> >> >> > +                               plugin. If this option is enabled the sss nss
>> >> >> > +                               plugin will behave as it was not in
>> >> >> > +                               nsswitch.conf when sssd is not running.
>> >> >> > +                               [default=no]])],
>> >> >> > +              [],
>> >> >> 
>> >> >> Didn't you mean to add:
>> >> >>     enable_sss-default-nss-plugin=$enablevar
>> >> >> 
>> >> >> here?
>> >> >> 
>> >> >> Additionally, it would be nice to explain in the commit message why the
>> >> >> feature is disabled -- explain the effect enabling by default would have
>> >> >> on searches that don't find anything.
>> >> >
>> >> >Actually, you also need to convert dashes to underscores in the variable
>> >> >name. As the autoconf docs say:
>> >> >    The option's argument is available to the shell commands
>> >> >    action-if-given in the shell variable enableval, which is actually
>> >> >    just the value of the shell variable named enable_feature, with any
>> >> >    non-alphanumeric characters in feature changed into ‘_’.
>> >> >
>> >> >This change did the trick for me and I was able to test the return value
>> >> >in gdb.
>> >> In gdb? really
>> >> Could you ellaborate?
>> >
>> >Once I fixed the config option so the build-time switch actually worked:
>> >
>> I thought you was able to see value of bash variable
>> enable_sss-default-nss-plugin :-)
>> 
>> New version is attached.
>> 
>> LS
>
>Thank you, the code looks good. Were you able to reproduce the exact
>same error as the user saw, though?
>
>I tested with "files sss ldap" in nsswitch.conf and SSSD was off. Even
>without the patch, getent group $ipagroup was able to fall back to
>ldap..so I guess I must be missing something.

Current version of sssd nsswitch plugin return error codeas as it is specified
in glibc documentation. ldap nsswitch plugin does the same.
So if sssd(nslcd) is stopped then sssd(ldap) plugin will return
NSS_STATUS_UNAVAIL.

The problem is with some distributions where sss is by default in
/etc/nsswitch.conf and sssd is not configured thus cannot be running.
The purpose of this patch is that sss plugin should behave as it wasn't in
nsswitch.conf.

So you should not test with ldap plugin, because ldap is not by default in
nsswitch.conf

So the test shoudl be:
a)
    passwd:     files sss
    && sssd service should be stopped
b)
    passwd:     files

and behaviour should be the same.
The C reprodurer is in this thread, public BZ [1] an private BZ[2]

[1] https://bugzilla.redhat.com/show_bug.cgi?id=988068
[2] https://bugzilla.redhat.com/show_bug.cgi?id=1124320

HTH

LS



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