From ad058011b6b75b15c674be46a3ae9b3cc5228175 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Michal=20=C5=BDidek?= <mzidek@redhat.com>

Date: Wed, 17 Oct 2018 16:57:20 +0200

Subject: [PATCH] GPO: Add option ad_gpo_ignore_unreadable

Add option to ignore group policy containers in AD

with unreadable or missing attributes. This is

for the case when server contains GPOs that

have very strict permissions on their attributes

in AD but are unrelated to access control.

Rather then using this option it is better to

change the permissions on the AD objects but

that may not be always possible (company policy,

not access to server etc.).

Resolves:

https://pagure.io/SSSD/sssd/issue/3867

CVE-2018-16838

Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

(cherry picked from commit 2f27dd9f05c2d3ed1c190ba387bc97738988efb0)

---

 src/config/cfg_rules.ini     |  1 +

 src/man/sssd-ad.5.xml        | 19 ++++++++++

 src/providers/ad/ad_common.h |  1 +

 src/providers/ad/ad_gpo.c    | 67 +++++++++++++++++++++++++++++++++---

 src/providers/ad/ad_opts.c   |  1 +

 5 files changed, 85 insertions(+), 4 deletions(-)

diff --git a/src/config/cfg_rules.ini b/src/config/cfg_rules.ini

index 887428437..603211711 100644

--- a/src/config/cfg_rules.ini

+++ b/src/config/cfg_rules.ini

@@ -439,6 +439,7 @@ option = ad_enabled_domains

 option = ad_enable_gc

 option = ad_gpo_access_control

 option = ad_gpo_implicit_deny

+option = ad_gpo_ignore_unreadable

 option = ad_gpo_cache_timeout

 option = ad_gpo_default_right

 option = ad_gpo_map_batch

diff --git a/src/man/sssd-ad.5.xml b/src/man/sssd-ad.5.xml

index f9b7f7667..b14f07f7f 100644

--- a/src/man/sssd-ad.5.xml

+++ b/src/man/sssd-ad.5.xml

@@ -437,6 +437,25 @@ DOM:dom1:(memberOf:1.2.840.113556.1.4.1941:=cn=nestedgroup,ou=groups,dc=example,

                     </listitem>

                 </varlistentry>

+                <varlistentry>

+                    <term>ad_gpo_ignore_unreadable (boolean)</term>

+                    <listitem>

+                        <para>

+                            Normally when some group policy containers (AD

+                            object) of applicable group policy objects are

+                            not readable by SSSD then users are denied access.

+                            This option allows to ignore group policy

+                            containers and with them associated policies

+                            if their attributes in group policy containers

+                            are not readable for SSSD.

+                        </para>

+                        <para>

+                            Default: False

+                        </para>

+                    </listitem>

+                </varlistentry>

+

+

                 <varlistentry>

                     <term>ad_gpo_cache_timeout (integer)</term>

diff --git a/src/providers/ad/ad_common.h b/src/providers/ad/ad_common.h

index 2c52c997a..529753a8a 100644

--- a/src/providers/ad/ad_common.h

+++ b/src/providers/ad/ad_common.h

@@ -53,6 +53,7 @@ enum ad_basic_opt {

     AD_ENABLE_GC,

     AD_GPO_ACCESS_CONTROL,

     AD_GPO_IMPLICIT_DENY,

+    AD_GPO_IGNORE_UNREADABLE,

     AD_GPO_CACHE_TIMEOUT,

     AD_GPO_MAP_INTERACTIVE,

     AD_GPO_MAP_REMOTE_INTERACTIVE,

diff --git a/src/providers/ad/ad_gpo.c b/src/providers/ad/ad_gpo.c

index 3b472e0e9..5f85910a9 100644

--- a/src/providers/ad/ad_gpo.c

+++ b/src/providers/ad/ad_gpo.c

@@ -3603,6 +3603,7 @@ struct ad_gpo_process_gpo_state {

     struct ad_access_ctx *access_ctx;

     struct tevent_context *ev;

     struct sdap_id_op *sdap_op;

+    struct dp_option *ad_options;

     struct sdap_options *opts;

     char *server_hostname;

     struct sss_domain_info *host_domain;

@@ -3647,6 +3648,7 @@ ad_gpo_process_gpo_send(TALLOC_CTX *mem_ctx,

     state->ev = ev;

     state->sdap_op = sdap_op;

+    state->ad_options = access_ctx->ad_options;

     state->opts = opts;

     state->server_hostname = server_hostname;

     state->host_domain = host_domain;

@@ -3871,6 +3873,54 @@ static bool machine_ext_names_is_blank(char *attr_value)

     return true;

 }

+static errno_t

+ad_gpo_missing_or_unreadable_attr(struct ad_gpo_process_gpo_state *state,

+                                  struct tevent_req *req)

+{

+    bool ignore_unreadable = dp_opt_get_bool(state->ad_options,

+                                             AD_GPO_IGNORE_UNREADABLE);

+

+    if (ignore_unreadable) {

+        /* If admins decided to skip GPOs with unreadable

+         * attributes just log the SID of skipped GPO */

+        DEBUG(SSSDBG_TRACE_FUNC,

+              "Group Policy Container with DN [%s] has unreadable or missing "

+              "attributes -> skipping this GPO "

+              "(ad_gpo_ignore_unreadable = True)\n",

+              state->candidate_gpos[state->gpo_index]->gpo_dn);

+        state->gpo_index++;

+        return ad_gpo_get_gpo_attrs_step(req);

+    } else {

+        /* Inform in logs and syslog that this GPO can

+         * not be processed due to unreadable or missing

+         * attributes and point to possible server side

+         * and client side solutions. */

+        DEBUG(SSSDBG_CRIT_FAILURE,

+              "Group Policy Container with DN [%s] is unreadable or has "

+              "unreadable or missing attributes. In order to fix this "

+              "make sure that this AD object has following attributes "

+              "readable: nTSecurityDescriptor, cn, gPCFileSysPath, "

+              "gPCMachineExtensionNames, gPCFunctionalityVersion, flags. "

+              "Alternatively if you do not have access to the server or can "

+              "not change permissions on this object, you can use option "

+              "ad_gpo_ignore_unreadable = True which will skip this GPO."

+              "See 'man ad_gpo_ignore_unreadable for details.'\n",

+              state->candidate_gpos[state->gpo_index]->gpo_dn);

+        sss_log(SSSDBG_CRIT_FAILURE,

+                "Group Policy Container with DN [%s] is unreadable or has "

+                "unreadable or missing attributes. In order to fix this "

+                "make sure that this AD object has following attributes "

+                "readable: nTSecurityDescriptor, cn, gPCFileSysPath, "

+                "gPCMachineExtensionNames, gPCFunctionalityVersion, flags. "

+                "Alternatively if you do not have access to the server or can "

+                "not change permissions on this object, you can use option "

+                "ad_gpo_ignore_unreadable = True which will skip this GPO."

+                "See 'man ad_gpo_ignore_unreadable for details.'\n",

+                state->candidate_gpos[state->gpo_index]->gpo_dn);

+        return EFAULT;

+    }

+}

+

 static errno_t

 ad_gpo_sd_process_attrs(struct tevent_req *req,

                         char *smb_host,

@@ -3890,7 +3940,10 @@ ad_gpo_sd_process_attrs(struct tevent_req *req,

     /* retrieve AD_AT_CN */

     ret = sysdb_attrs_get_string(result, AD_AT_CN, &gpo_guid);

-    if (ret != EOK) {

+    if (ret == ENOENT) {

+        ret = ad_gpo_missing_or_unreadable_attr(state, req);

+        goto done;

+    } else if (ret != EOK) {

         DEBUG(SSSDBG_OP_FAILURE,

               "sysdb_attrs_get_string failed: [%d](%s)\n",

               ret, sss_strerror(ret));

@@ -3911,7 +3964,10 @@ ad_gpo_sd_process_attrs(struct tevent_req *req,

                                  AD_AT_FILE_SYS_PATH,

                                  &raw_file_sys_path);

-    if (ret != EOK) {

+    if (ret == ENOENT) {

+        ret = ad_gpo_missing_or_unreadable_attr(state, req);

+        goto done;

+    } else if (ret != EOK) {

         DEBUG(SSSDBG_OP_FAILURE,

               "sysdb_attrs_get_string failed: [%d](%s)\n",

               ret, sss_strerror(ret));

@@ -3959,7 +4015,10 @@ ad_gpo_sd_process_attrs(struct tevent_req *req,

     /* retrieve AD_AT_FLAGS */

     ret = sysdb_attrs_get_int32_t(result, AD_AT_FLAGS,

                                   &gp_gpo->gpo_flags);

-    if (ret != EOK) {

+    if (ret == ENOENT) {

+        ret = ad_gpo_missing_or_unreadable_attr(state, req);

+        goto done;

+    } else if (ret != EOK) {

         DEBUG(SSSDBG_OP_FAILURE,

               "sysdb_attrs_get_int32_t failed: [%d](%s)\n",

               ret, sss_strerror(ret));

@@ -3977,7 +4036,7 @@ ad_gpo_sd_process_attrs(struct tevent_req *req,

     if ((ret == ENOENT) || (el->num_values == 0)) {

         DEBUG(SSSDBG_OP_FAILURE,

               "nt_sec_desc attribute not found or has no value\n");

-        ret = ENOENT;

+        ret = ad_gpo_missing_or_unreadable_attr(state, req);

         goto done;

     }

diff --git a/src/providers/ad/ad_opts.c b/src/providers/ad/ad_opts.c

index b274ba9b3..c408295f3 100644

--- a/src/providers/ad/ad_opts.c

+++ b/src/providers/ad/ad_opts.c

@@ -39,6 +39,7 @@ struct dp_option ad_basic_opts[] = {

     { "ad_enable_gc", DP_OPT_BOOL, BOOL_TRUE, BOOL_TRUE },

     { "ad_gpo_access_control", DP_OPT_STRING, { AD_GPO_ACCESS_MODE_DEFAULT }, NULL_STRING },

     { "ad_gpo_implicit_deny", DP_OPT_BOOL, BOOL_FALSE, BOOL_FALSE },

+    { "ad_gpo_ignore_unreadable", DP_OPT_BOOL, BOOL_FALSE, BOOL_FALSE },

     { "ad_gpo_cache_timeout", DP_OPT_NUMBER, { .number = 5 }, NULL_NUMBER },

     { "ad_gpo_map_interactive", DP_OPT_STRING, NULL_STRING, NULL_STRING },

     { "ad_gpo_map_remote_interactive", DP_OPT_STRING, NULL_STRING, NULL_STRING },

-- 

2.19.1