[SSSD] [PATCH] IPA: Ignore dns_discovery_domain in server mode

Jakub Hrozek jhrozek at redhat.com
Wed Sep 25 10:57:01 UTC 2013


On Wed, Sep 25, 2013 at 11:53:36AM +0200, Sumit Bose wrote:
> On Wed, Sep 25, 2013 at 11:12:02AM +0200, Jakub Hrozek wrote:
> > Hi,
> > 
> > the attached patch fixes
> > https://fedorahosted.org/sssd/ticket/2079
> > 
> > 
> > I also opened https://fedorahosted.org/freeipa/ticket/3947 to stop
> > setting the dns_discovery_domain parameter from the IPA installer
> > completely.
> 
> > From e714f3ef180934fa92ca805384ddbf1a510051c8 Mon Sep 17 00:00:00 2001
> > From: Jakub Hrozek <jhrozek at redhat.com>
> > Date: Wed, 25 Sep 2013 11:03:16 +0200
> > Subject: [PATCH] IPA: Ignore dns_discovery_domain in server mode
> > 
> > https://fedorahosted.org/sssd/ticket/2079
> > ---
> >  src/providers/ipa/ipa_init.c | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> > 
> > diff --git a/src/providers/ipa/ipa_init.c b/src/providers/ipa/ipa_init.c
> > index a5ab881821c3d169285cb1dca7605a221b4cf604..f5e482344f405abd453bf54ed24110cebc65fb65 100644
> > --- a/src/providers/ipa/ipa_init.c
> > +++ b/src/providers/ipa/ipa_init.c
> > @@ -256,6 +256,18 @@ int sssm_ipa_id_init(struct be_ctx *bectx,
> >          be_fo_set_srv_lookup_plugin(bectx, ipa_srv_plugin_send,
> >                                      ipa_srv_plugin_recv, srv_ctx, "IPA");
> >      } else if (server_mode == true) {
> > +        /* In server mode we need to ignore the dns_discovery_domain if set
> > +         * and only discover servers based on AD domains
> > +         */
> > +        ret = dp_opt_set_string(bectx->be_res->opts, DP_RES_OPT_DNS_DOMAIN,
> > +                                NULL);
> 
> In general I agree with the patch mainly because it looks there is no
> easy way to only let the AD SRV plugin in ipa_server_mode know to ignore
> the option.
> 
> But I would suggest to add some extra checks.
> 
> The dns_discovery_domain option is only set by ipa-client-install if the
> host where ipa-client-install is running is not from the IPA domain.
> Because in this case it might not be possible to find IPA server with
> DNS SRV lookups where the domain name of the host is used. But since we
> are running on a server (server_mode == true) ipa-client-install will by
> default not configure any SRV lookups for the IPA server, i.e. there
> will be no _srv_ in the ipa_server option.
> 
> So with the default everything would work well with the patch. But if
> someone modifies sssd.conf manually it might break. I would suggest to
> check if the DNS domain of the host is the same as the IPA domain. If
> not and ipa_server only contains _srv_ I would not set
> DP_RES_OPT_DNS_DOMAIN to NULL but send a log message even to syslog
> telling the admin that AD lookups will not work in this setup and
> ipa_server should only contain the local hostname.

OK, you're right we should add more checks, see the attached patch.

But I think we should warn anytime the dns_discovery_domain is used. Because
the current failover code would blindly use it for AD discovery, the setup
could only ever work if dns_discovery_domain was set to the AD domain. Then
the SSSD could fail over from SRV to local hostname and AD would use the
DNS domain.
-------------- next part --------------
>From 4886f8b19ef99968ebf575a5dd7e265c12bb4a52 Mon Sep 17 00:00:00 2001
From: Jakub Hrozek <jhrozek at redhat.com>
Date: Wed, 25 Sep 2013 11:03:16 +0200
Subject: [PATCH] IPA: Ignore dns_discovery_domain in server mode

https://fedorahosted.org/sssd/ticket/2079

If the dns_discovery_domain is set in the server mode, then the current
failover code will use it to discover the AD servers as well. This patch
resets the discovery domain unless the admin configured SRV resolution
for IPA servers manually. In the case he did, we try to warn him that
service discovery of AD servers will most likely fail.
---
 src/providers/ipa/ipa_init.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/src/providers/ipa/ipa_init.c b/src/providers/ipa/ipa_init.c
index a5ab881821c3d169285cb1dca7605a221b4cf604..4eab1e2ab0f6013bb97f10fe0aadcefc4a8b7c57 100644
--- a/src/providers/ipa/ipa_init.c
+++ b/src/providers/ipa/ipa_init.c
@@ -261,12 +261,45 @@ int sssm_ipa_id_init(struct be_ctx *bectx,
             DEBUG(SSSDBG_MINOR_FAILURE, ("SRV resolution enabled on the IPA server. "
                   "Site discovery of trusted AD servers might not work\n"));
 
+            /* If SRV discovery is enabled on the server and
+             * dns_discovery_domain is set explicitly, then
+             * the current failover code would use the dns_discovery
+             * domain to try to find AD servers and fail
+             */
+            if (dp_opt_get_string(bectx->be_res->opts,
+                                  DP_RES_OPT_DNS_DOMAIN)) {
+                sss_log(SSS_LOG_ERR, ("SRV discovery is enabled on the IPA "
+                        "server while using custom dns_discovery_domain. "
+                        "DNS discovery of trusted AD domain will likely fail. "
+                        "It is recommended not to use SRV discovery or the "
+                        "dns_discovery_domain option for the IPA domain while "
+                        "running on the server itself\n"));
+                DEBUG(SSSDBG_CRIT_FAILURE, ("SRV discovery is enabled on IPA "
+                      "server while using custom dns_discovery_domain. "
+                      "DNS discovery of trusted AD domain will likely fail. "
+                      "It is recommended not to use SRV discovery or the "
+                      "dns_discovery_domain option for the IPA domain while "
+                      "running on the server itself\n"));
+            }
+
             ret = be_fo_set_dns_srv_lookup_plugin(bectx, hostname);
             if (ret != EOK) {
                 DEBUG(SSSDBG_CRIT_FAILURE, ("Unable to set SRV lookup plugin "
                                             "[%d]: %s\n", ret, strerror(ret)));
                 goto done;
             }
+        } else {
+            /* In server mode we need to ignore the dns_discovery_domain if set
+             * and only discover servers based on AD domains
+             */
+            ret = dp_opt_set_string(bectx->be_res->opts, DP_RES_OPT_DNS_DOMAIN,
+                                    NULL);
+            if (ret != EOK) {
+                DEBUG(SSSDBG_MINOR_FAILURE, ("Could not reset the "
+                    "dns_discovery_domain, trusted AD domains discovery "
+                    "might fail. Please remove dns_discovery_domain "
+                    "from the config file and restart the SSSD\n"));
+            }
         }
     } else {
         /* fall back to standard plugin on clients. */
-- 
1.8.3.1



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