dbchecker: Fixing up incorrect DNs wasn't working

dbcheck would fail to fix up attributes where the extended DN's GUID is
correct, but the DN itself is incorrect. The code failed attempting to
remove the old/incorrect DN, e.g.

 NOTE: old (due to rename or delete) DN string component for
 objectCategory in object CN=alice,CN=Users,DC=samba,DC=example,DC=com -
 <GUID=7bfdf9d8-62f9-420c-8a71-e3d3e931c91e>;
   CN=Person,CN=Schema,CN=Configuration,DC=samba,DC=bad,DC=com
 Change DN to <GUID=7bfdf9d8-62f9-420c-8a71-e3d3e931c91e>;
   CN=Person,CN=Schema,CN=Configuration,DC=samba,DC=example,DC=com?
 [y/N/all/none] y
 Failed to fix old DN string on attribute objectCategory : (16,
 "attribute 'objectCategory': no matching attribute value while deleting
 attribute on 'CN=alice,CN=Users,DC=samba,DC=example,DC=com'")

The problem was the LDB message specified the value to delete with its
full DN, including the GUID. The LDB code then helpfully corrected this
value on the way through, so that the DN got updated to reflect the
correct DN (i.e. 'DC=example,DC=com') of the object matching that GUID,
rather than the incorrect DN (i.e. 'DC=bad,DC=com') that we were trying
to remove. Because the requested value and the existing DB value didn't
match, the operation failed.

We can avoid this problem by passing down just the DN (not the extended
DN) of the value we want to delete. Without the GUID portion of the DN,
the LDB code will no longer try to correct it on the way through, and
the dbcheck operation will succeed.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13495

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Gary Lockyer <gary@catalyst.net.nz>
Pair-programmed-with: Andrew Bartlett <abartlet@samba.org>

7 files changed, 171 insertions, 5 deletions

diff --git a/python/samba/dbchecker.py b/python/samba/dbchecker.py
index 00194afffaf..c64fd4c1159 100644
--- a/python/samba/dbchecker.py
+++ b/python/samba/dbchecker.py
@@ -656,7 +656,8 @@ newSuperior: %s""" % (str(from_dn), str(to_rdn), str(to_base)))
         m.dn = dn
         m['old_value'] = ldb.MessageElement(val, ldb.FLAG_MOD_DELETE, attrname)
         m['new_value'] = ldb.MessageElement(str(dsdb_dn), ldb.FLAG_MOD_ADD, attrname)
-        if self.do_modify(m, ["show_recycled:1"],
+        if self.do_modify(m, ["show_recycled:1",
+                              "local_oid:%s:1" % dsdb.DSDB_CONTROL_DBCHECK_FIX_LINK_DN_NAME],
                           "Failed to fix old DN string on attribute %s" % (attrname)):
             self.report("Fixed old DN string on attribute %s" % (attrname))
 
@@ -1298,14 +1299,22 @@ newSuperior: %s""" % (str(from_dn), str(to_rdn), str(to_base)))
                                                       res[0].dn, "SID")
                 continue
 
+            # Only for non-links, not even forward-only links
+            # (otherwise this breaks repl_meta_data):
+            #
             # Now we have checked the GUID and SID, offer to fix old
-            # DN strings as a non-error (for forward links with no
+            # DN strings as a non-error (DNs, not links so no
             # backlink).  Samba does not maintain this string
             # otherwise, so we don't increment error_count.
             if reverse_link_name is None:
-                if str(res[0].dn) != str(dsdb_dn.dn):
-                    self.err_dn_string_component_old(obj.dn, attrname, val, dsdb_dn,
-                                                     res[0].dn)
+                if linkID == 0 and str(res[0].dn) != str(dsdb_dn.dn):
+                    # Pass in the old/bad DN without the <GUID=...> part,
+                    # otherwise the LDB code will correct it on the way through
+                    # (Note: we still want to preserve the DSDB DN prefix in the
+                    # case of binary DNs)
+                    bad_dn = dsdb_dn.prefix + dsdb_dn.dn.get_linearized()
+                    self.err_dn_string_component_old(obj.dn, attrname, bad_dn,
+                                                     dsdb_dn, res[0].dn)
                 continue
 
             # check the reverse_link is correct if there should be one
diff --git a/source4/dsdb/pydsdb.c b/source4/dsdb/pydsdb.c
index d10c7ec3b9d..a25f3411ae7 100644
--- a/source4/dsdb/pydsdb.c
+++ b/source4/dsdb/pydsdb.c
@@ -1582,6 +1582,7 @@ MODULE_INIT_FUNC(dsdb)
 	ADD_DSDB_STRING(DSDB_CONTROL_DBCHECK);
 	ADD_DSDB_STRING(DSDB_CONTROL_DBCHECK_MODIFY_RO_REPLICA);
 	ADD_DSDB_STRING(DSDB_CONTROL_DBCHECK_FIX_DUPLICATE_LINKS);
+	ADD_DSDB_STRING(DSDB_CONTROL_DBCHECK_FIX_LINK_DN_NAME);
 	ADD_DSDB_STRING(DSDB_CONTROL_REPLMD_VANISH_LINKS);
 	ADD_DSDB_STRING(DSDB_CONTROL_PERMIT_INTERDOMAIN_TRUST_UAC_OID);
 	ADD_DSDB_STRING(DSDB_CONTROL_SKIP_DUPLICATES_CHECK_OID);
diff --git a/source4/dsdb/samdb/ldb_modules/repl_meta_data.c b/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
index 7395f52524e..c4a41a28d04 100644
--- a/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
+++ b/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
@@ -3333,6 +3333,7 @@ static int replmd_modify(struct ldb_module *module, struct ldb_request *req)
 	const struct ldb_message_element *guid_el = NULL;
 	struct ldb_control *sd_propagation_control;
 	struct ldb_control *fix_links_control = NULL;
+	struct ldb_control *fix_dn_name_control = NULL;
 	struct replmd_private *replmd_private =
 		talloc_get_type(ldb_module_get_private(module), struct replmd_private);
 
@@ -3391,6 +3392,69 @@ static int replmd_modify(struct ldb_module *module, struct ldb_request *req)
 		return ldb_next_request(module, req);
 	}
 
+	fix_dn_name_control = ldb_request_get_control(req,
+					DSDB_CONTROL_DBCHECK_FIX_LINK_DN_NAME);
+	if (fix_dn_name_control != NULL) {
+		struct dsdb_schema *schema = NULL;
+		const struct dsdb_attribute *sa = NULL;
+
+		if (req->op.mod.message->num_elements != 2) {
+			return ldb_module_operr(module);
+		}
+
+		if (req->op.mod.message->elements[0].flags != LDB_FLAG_MOD_DELETE) {
+			return ldb_module_operr(module);
+		}
+
+		if (req->op.mod.message->elements[1].flags != LDB_FLAG_MOD_ADD) {
+			return ldb_module_operr(module);
+		}
+
+		if (req->op.mod.message->elements[0].num_values != 1) {
+			return ldb_module_operr(module);
+		}
+
+		if (req->op.mod.message->elements[1].num_values != 1) {
+			return ldb_module_operr(module);
+		}
+
+		schema = dsdb_get_schema(ldb, req);
+		if (schema == NULL) {
+			return ldb_module_operr(module);
+		}
+
+		if (ldb_attr_cmp(req->op.mod.message->elements[0].name,
+				 req->op.mod.message->elements[1].name) != 0) {
+			return ldb_module_operr(module);
+		}
+
+		sa = dsdb_attribute_by_lDAPDisplayName(schema,
+				req->op.mod.message->elements[0].name);
+		if (sa == NULL) {
+			return ldb_module_operr(module);
+		}
+
+		if (sa->dn_format == DSDB_INVALID_DN) {
+			return ldb_module_operr(module);
+		}
+
+		if (sa->linkID != 0) {
+			return ldb_module_operr(module);
+		}
+
+		/*
+		 * If we are run from dbcheck and we are not updating
+		 * a link (as these would need to be sorted and so
+		 * can't go via such a simple update, then do not
+		 * trigger replicated updates and a new USN from this
+		 * change, it wasn't a real change, just a new
+		 * (correct) string DN
+		 */
+
+		fix_dn_name_control->critical = false;
+		return ldb_next_request(module, req);
+	}
+
 	ldb_debug(ldb, LDB_DEBUG_TRACE, "replmd_modify\n");
 
 	guid_el = ldb_msg_find_element(req->op.mod.message, "objectGUID");
diff --git a/source4/dsdb/samdb/samdb.h b/source4/dsdb/samdb/samdb.h
index 28d1b5cb32f..805a1f65fa8 100644
--- a/source4/dsdb/samdb/samdb.h
+++ b/source4/dsdb/samdb/samdb.h
@@ -132,6 +132,9 @@ struct dsdb_control_password_change {
 /* passed by dbcheck to fix duplicate linked attributes (bug #13095) */
 #define DSDB_CONTROL_DBCHECK_FIX_DUPLICATE_LINKS "1.3.6.1.4.1.7165.4.3.19.2"
 
+/* passed by dbcheck to fix the DN strong of a one-way-link (bug #13495) */
+#define DSDB_CONTROL_DBCHECK_FIX_LINK_DN_NAME "1.3.6.1.4.1.7165.4.3.19.3"
+
 /* passed when importing plain text password on upgrades */
 #define DSDB_CONTROL_PASSWORD_BYPASS_LAST_SET_OID "1.3.6.1.4.1.7165.4.3.20"
 
diff --git a/source4/selftest/provisions/release-4-5-0-pre1/expected-after-dbcheck-oneway-link-corruption.ldif b/source4/selftest/provisions/release-4-5-0-pre1/expected-after-dbcheck-oneway-link-corruption.ldif
new file mode 100644
index 00000000000..b2142df7424
--- /dev/null
+++ b/source4/selftest/provisions/release-4-5-0-pre1/expected-after-dbcheck-oneway-link-corruption.ldif
@@ -0,0 +1,19 @@
+# record 1
+dn: OU=dangling-ou2,DC=release-4-5-0-pre1,DC=samba,DC=corp
+
+# record 2
+dn: OU=dangling-from,DC=release-4-5-0-pre1,DC=samba,DC=corp
+seeAlso: OU=dangling-ou2,DC=release-4-5-0-pre1,DC=samba,DC=corp
+
+# Referral
+ref: ldap:///CN=Configuration,DC=release-4-5-0-pre1,DC=samba,DC=corp
+
+# Referral
+ref: ldap:///DC=DomainDnsZones,DC=release-4-5-0-pre1,DC=samba,DC=corp
+
+# Referral
+ref: ldap:///DC=ForestDnsZones,DC=release-4-5-0-pre1,DC=samba,DC=corp
+
+# returned 5 records
+# 2 entries
+# 3 referrals
diff --git a/source4/selftest/provisions/release-4-5-0-pre1/expected-dbcheck-link-output-oneway-link-corruption.txt b/source4/selftest/provisions/release-4-5-0-pre1/expected-dbcheck-link-output-oneway-link-corruption.txt
new file mode 100644
index 00000000000..69d1e516d14
--- /dev/null
+++ b/source4/selftest/provisions/release-4-5-0-pre1/expected-dbcheck-link-output-oneway-link-corruption.txt
@@ -0,0 +1,5 @@
+Checking 228 objects
+NOTE: old (due to rename or delete) DN string component for seeAlso in object OU=dangling-from,DC=release-4-5-0-pre1,DC=samba,DC=corp - OU=dangling-ou,DC=release-4-5-0-pre1,DC=samba,DC=corp
+Change DN to <GUID=20600e7c-92bb-492e-9552-f3ed7f8a2cad>;OU=dangling-ou2,DC=release-4-5-0-pre1,DC=samba,DC=corp? [YES]
+Fixed old DN string on attribute seeAlso
+Checked 228 objects (0 errors)
diff --git a/testprogs/blackbox/dbcheck-links.sh b/testprogs/blackbox/dbcheck-links.sh
index 778edf002c9..13811ddb461 100755
--- a/testprogs/blackbox/dbcheck-links.sh
+++ b/testprogs/blackbox/dbcheck-links.sh
@@ -205,6 +205,67 @@ check_expected_after_dbcheck_forward_link_corruption() {
     fi
 }
 
+oneway_link_corruption() {
+    #
+    # Step1: add  OU "dangling-ou"
+    #
+    ldif=$PREFIX_ABS/${RELEASE}/oneway_link_corruption.ldif
+    cat > $ldif <<EOF
+dn: OU=dangling-ou,DC=release-4-5-0-pre1,DC=samba,DC=corp
+changetype: add
+objectclass: organizationalUnit
+objectGUID: 20600e7c-92bb-492e-9552-f3ed7f8a2cad
+EOF
+
+    out=$(TZ=UTC $ldbmodify -H tdb://$PREFIX_ABS/${RELEASE}/private/sam.ldb --relax $ldif)
+    if [ "$?" != "0" ]; then
+	echo "ldbmodify returned:\n$out"
+	return 1
+    fi
+
+    #
+    # Step2: add  msExchConfigurationContainer "dangling-msexch"
+    #
+    ldif=$PREFIX_ABS/${RELEASE}/oneway_link_corruption2.ldif
+    cat > $ldif <<EOF
+dn: OU=dangling-from,DC=release-4-5-0-pre1,DC=samba,DC=corp
+changetype: add
+objectclass: organizationalUnit
+seeAlso: OU=dangling-ou,DC=release-4-5-0-pre1,DC=samba,DC=corp
+EOF
+
+    out=$(TZ=UTC $ldbmodify -H tdb://$PREFIX_ABS/${RELEASE}/private/sam.ldb $ldif)
+    if [ "$?" != "0" ]; then
+	echo "ldbmodify returned:\n$out"
+	return 1
+    fi
+
+    #
+    # Step3: rename dangling-ou to dangling-ou2
+    #
+    # Because this is a one-way link we don't fix it at runtime
+    #
+    out=$(TZ=UTC $ldbrename -H tdb://$PREFIX_ABS/${RELEASE}/private/sam.ldb OU=dangling-ou,DC=release-4-5-0-pre1,DC=samba,DC=corp OU=dangling-ou2,DC=release-4-5-0-pre1,DC=samba,DC=corp)
+    if [ "$?" != "0" ]; then
+	echo "ldbmodify returned:\n$out"
+	return 1
+    fi
+}
+
+dbcheck_oneway_link_corruption() {
+    dbcheck "-oneway-link-corruption" "0" ""
+    return $?
+}
+
+check_expected_after_dbcheck_oneway_link_corruption() {
+    tmpldif=$PREFIX_ABS/$RELEASE/expected-after-dbcheck-oneway-link-corruption.ldif.tmp
+    TZ=UTC $ldbsearch -H tdb://$PREFIX_ABS/${RELEASE}/private/sam.ldb '(|(ou=dangling-ou)(ou=dangling-ou2)(ou=dangling-from))' -s sub -b DC=release-4-5-0-pre1,DC=samba,DC=corp --show-deleted --sorted seeAlso > $tmpldif
+    diff $tmpldif $release_dir/expected-after-dbcheck-oneway-link-corruption.ldif
+    if [ "$?" != "0" ]; then
+	return 1
+    fi
+}
+
 dbcheck_dangling_multi_valued() {
 
     $PYTHON $BINDIR/samba-tool dbcheck -H tdb://$PREFIX_ABS/${RELEASE}/private/sam.ldb --fix --yes
@@ -276,6 +337,10 @@ if [ -d $release_dir ]; then
     testit "dbcheck_forward_link_corruption" dbcheck_forward_link_corruption
     testit "check_expected_after_dbcheck_forward_link_corruption" check_expected_after_dbcheck_forward_link_corruption
     testit "forward_link_corruption_clean" dbcheck_clean
+    testit "oneway_link_corruption" oneway_link_corruption
+    testit "dbcheck_oneway_link_corruption" dbcheck_oneway_link_corruption
+    testit "check_expected_after_dbcheck_oneway_link_corruption" check_expected_after_dbcheck_oneway_link_corruption
+    testit "oneway_link_corruption_clean" dbcheck_clean
     testit "dangling_one_way_link" dangling_one_way_link
     testit "dbcheck_one_way" dbcheck_one_way
     testit "dbcheck_clean2" dbcheck_clean