Upstream ticket https://pagure.io/389-ds-base/issue/49291

upstream slapi-nis ticket https://pagure.io/slapi-nis/issue/16 (improve robustness of slapi-nis)

upstream slapi-nis ticket https://pagure.io/slapi-nis/issue/17 (format_add_sdn_list was called with empty sdn)

As a follow up of investigations of https://pagure.io/slapi-nis/issue/17 


    - Because base_sdn_list and base_sdn_list2 contains the same SDN with NULL DN
      we know the NULL DN was added by calling format_add_sdn_list.

    - The NULL DN SDN was the last SDN of base_sdn_list, so it was append to the list

    - format_add_sdn_list is call in several places
      backend_shr_update_references_cb
      backend_shr_note_entry_sdn_cb
      format_referred_r_entry_cb
      format_maybe_add_sdn_list
      format_deref_rx
      format_referred_r


    - In backend_shr_update_references_cb:
      backend_shr_update_references_cb was not called with an entry with NULL dn
      In fact, 'cn=groups' maps contains a 'ignore_subtree' array.
      In such condition the entry DN is tested and if it is NULL,
      backend_shr_update_references_cb exits before calling format_add_sdn_list.
(gdb) print *(struct backend_shr_set_data *) backend_data
$2 = {state = 0x7fa57b585a30, group = 0x7fa521a75df0 "cn=compat,<suffix>", set = 0x7fa5238e28a0 "cn=groups", 
  bases = 0x7fa5238ea0c0, entry_filter = 0x7fa520008220 "(objectclass=posixGroup)", rel_attrs = 0x7fa523eae650, 
  rel_attr_list = 0x7fa528007860 "cn,ipaanchoruuid,gidNumber,memberUid,ipauniqueid,member,uid", rel_attrs_list = 0x7fa523eae650, 
  ref_attrs = 0x0, inref_attrs = 0x0, ref_attr_list = 0x7fa510582480, inref_attr_list = 0x0, skip_uninteresting_updates = 1, 
(gdb) print *((struct backend_shr_set_data *) backend_data)->ignore_subtrees[0]
$5 = {flag = 7 '\a', udn = 0x0, dn = 0x7fa521a53330 "cn=tasks,cn=config", ndn = 0x7fa510f8b240 "cn=tasks,cn=config", ndn_len = 18}
(gdb) print *((struct backend_shr_set_data *) backend_data)->ignore_subtrees[1]
Cannot access memory at address 0x0
      
      So the NULL DN SDN was not added by backend_shr_update_references_cb


    -  In backend_shr_note_entry_sdn_cb
      backend_shr_note_entry_sdn_cb is a callback of a search function.
      A NULL dn entry does not exist. An internal search would not call backend_shr_note_entry_sdn_cb with an NULL DN entry

    - In format_referred_r_entry_cb
      Idem as above

    - In format_maybe_add_sdn_list
      It does not call format_add_sdn_list on NULL dn entry

    - format_deref_rx
      This is possible when looping over parents entries

    - format_referred_r
      This is possible 
            if backend_get_set_config can return NULL DN SDN
            if it is call with an entry containing NULL DN


    In conclusion:
        The most probable place to introduce NULL DN SDN in the list are
            format_deref_rx (while looping other parents)
            format_referred_r (backend_get_set_config / called with NULL DN entry)

Hi Viktor,

Unfortunately I think the easiest way to reproduce is to use/configure slapi-nis.
We need to have a plugin that triggers an internal search with a base search that is SDN containing a NULL DN.

I do not know if using slapi-nis is an acceptable option to test that bug. If it is you can use the test case described in https://pagure.io/slapi-nis/issue/17 (having a group with members (member attribute) with one of the 'member' value being empty).

If it is not acceptable I will need to dig in our standard plugins to check if one of them is doing an internal search without checking the base search SDN.

Builds tested:
389-ds-base-1.3.7.5-10.el7.x86_64
slapi-nis-0.56.0-7.el7.x86_64

[1] To verify I configured slapi-nis plugin: 
# ldapadd -D "cn=Directory Manager" -w Secret123
dn: cn=NIS Server,cn=plugins,cn=config
objectClass: top
objectClass: nsSlapdPlugin
objectClass: extensibleObject
cn: NIS Server
nsslapd-pluginPath: /usr/lib64/dirsrv/plugins/nisserver-plugin.so
nsslapd-pluginInitfunc: nis_plugin_init
nsslapd-pluginType: postoperation
nsslapd-pluginEnabled: on
nsslapd-pluginDescription: NIS Server Plugin
nsslapd-pluginVendor: redhat.com
nsslapd-pluginVersion: 0.56 (betxn support available and enabled by default)
nsslapd-pluginId: nis-plugin
nis-tcp-wrappers-name: ypserv
nsslapd-pluginarg0: 541

dn: nis-domain=example.com+nis-map=groups,cn=NIS Server,cn=plugins,cn=config
objectClass: extensibleObject
objectClass: top
nis-domain: example.com
nis-map: groups
nis-base: ou=Groups, dc=example, dc=com
nis-filter: (objectClass=groupOfNames)
nis-key-format: %{cn}
nis-value-format: %merge(" ","%deref_f(\"member\",\"(objectclass=ipanisNetgroup)\",\"cn\")","(%link(\"%ifeq(\\\"hostCategory\\\",\\\"all\\\",\\\"\\\",\\\"%collect(\\\\\\\"%{externalHost}\\\\\\\",\\\\\\\"%deref(\\\\\\\\\\\\\\\"memberHost\\\\\\\\\\\\\\\",\\\\\\\\\\\\\\\"fqdn\\\\\\\\\\\\\\\")\\\\\\\",\\\\\\\"%deref_r(\\\\\\\\\\\\\\\"member\\\\\\\\\\\\\\\",\\\\\\\\\\\\\\\"fqdn\\\\\\\\\\\\\\\")\\\\\\\",\\\\\\\"%deref_r(\\\\\\\\\\\\\\\"memberHost\\\\\\\\\\\\\\\",\\\\\\\\\\\\\\\"member\\\\\\\\\\\\\\\",\\\\\\\\\\\\\\\"fqdn\\\\\\\\\\\\\\\")\\\\\\\")\\\")\",\"%ifeq(\\\"hostCategory\\\",\\\"all\\\",\\\"\\\",\\\"-\\\")\",\",\",\"%ifeq(\\\"userCategory\\\",\\\"all\\\",\\\"\\\",\\\"%collect(\\\\\\\"%deref(\\\\\\\\\\\\\\\"memberUser\\\\\\\\\\\\\\\",\\\\\\\\\\\\\\\"uid\\\\\\\\\\\\\\\")\\\\\\\",\\\\\\\"%deref_r(\\\\\\\\\\\\\\\"member\\\\\\\\\\\\\\\",\\\\\\\\\\\\\\\"uid\\\\\\\\\\\\\\\")\\\\\\\",\\\\\\\"%deref_r(\\\\\\\\\\\\\\\"memberUser\\\\\\\\\\\\\\\",\\\\\\\\\\\\\\\"member\\\\\\\\\\\\\\\",\\\\\\\\\\\\\\\"uid\\\\\\\\\\\\\\\")\\\\\\\")\\\")\",\"%ifeq(\\\"userCategory\\\",\\\"all\\\",\\\"\\\",\\\"-\\\")\"),%{nisDomainName:-})")

adding new entry "cn=NIS Server,cn=plugins,cn=config"

adding new entry "nis-domain=example.com+nis-map=groups,cn=NIS Server,cn=plugins,cn=config"

[2] Added test entries:

# ldapadd -D "cn=Directory Manager" -w Secret123
dn: cn=tuser,ou=People,dc=example,dc=com
objectClass: inetOrgPerson
objectClass: posixAccount
objectClass: organizationalPerson
objectClass: top
objectClass: person
cn: tuser
sn: tuser
uid: tuser
gidNumber: 2000
homeDirectory: /home/tuser
uidNumber: 2000

dn: cn=tgroup,ou=Groups,dc=example,dc=com
objectClass: groupofnames
objectClass: top
cn: tgroup
member:
member: cn=tuser,ou=People,dc=example,dc=com

adding new entry "cn=tuser,ou=People,dc=example,dc=com"

adding new entry "cn=tgroup,ou=Groups,dc=example,dc=com"


[3] Removed empty member attribute without server crashing:

# ldapmodify -D "cn=Directory Manager" -w Secret123
dn: cn=tgroup,ou=Groups,dc=example,dc=com
changetype: modify
replace: member
member: cn=tuser,ou=People,dc=example,dc=com

modifying entry "cn=tgroup,ou=Groups,dc=example,dc=com"

Marking as VERIFIED.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2018:0811