From 0b9da247534f735fa96141e9285fd22e0f2bb442 Mon Sep 17 00:00:00 2001 From: Douglas Bagnall Date: Wed, 22 May 2019 12:58:01 +1200 Subject: [PATCH] CVE-2019-12435 rpc/dns: avoid NULL deference if zone not found in DnssrvOperation We still want to return DOES_NOT_EXIST when request_filter is not 0. BUG: https://bugzilla.samba.org/show_bug.cgi?id=13922 Signed-off-by: Douglas Bagnall Reviewed-by: Andrew Bartlett --- python/samba/tests/dcerpc/dnsserver.py | 25 +++++++++++++++++++ .../rpc_server/dnsserver/dcerpc_dnsserver.c | 7 +++++- 2 files changed, 31 insertions(+), 1 deletion(-) diff --git a/python/samba/tests/dcerpc/dnsserver.py b/python/samba/tests/dcerpc/dnsserver.py index 8e485c540dd..bfe86323e0c 100644 --- a/python/samba/tests/dcerpc/dnsserver.py +++ b/python/samba/tests/dcerpc/dnsserver.py @@ -28,6 +28,7 @@ from samba.dcerpc import dnsp, dnsserver, security from samba.tests import RpcInterfaceTestCase, env_get_var_value from samba.netcmd.dns import ARecord, AAAARecord, PTRRecord, CNameRecord, NSRecord, MXRecord, SRVRecord, TXTRecord from samba import sd_utils, descriptor +from samba import WERRORError, werror class DnsserverTests(RpcInterfaceTestCase): @@ -707,6 +708,30 @@ class DnsserverTests(RpcInterfaceTestCase): 'ServerInfo') self.assertEquals(dnsserver.DNSSRV_TYPEID_SERVER_INFO, typeid) + + # This test is to confirm that we do not support multizone operations, + # which are designated by a non-zero dwContext value (the 3rd argument + # to DnssrvOperation). + def test_operation_invalid(self): + non_zone = 'a-zone-that-does-not-exist' + typeid = dnsserver.DNSSRV_TYPEID_NAME_AND_PARAM + name_and_param = dnsserver.DNS_RPC_NAME_AND_PARAM() + name_and_param.pszNodeName = 'AllowUpdate' + name_and_param.dwParam = dnsp.DNS_ZONE_UPDATE_SECURE + try: + res = self.conn.DnssrvOperation(self.server, + non_zone, + 1, + 'ResetDwordProperty', + typeid, + name_and_param) + except WERRORError as e: + if e.args[0] == werror.WERR_DNS_ERROR_ZONE_DOES_NOT_EXIST: + return + + # We should always encounter a DOES_NOT_EXIST error. + self.fail() + def test_operation2(self): client_version = dnsserver.DNS_CLIENT_VERSION_LONGHORN rev_zone = '1.168.192.in-addr.arpa' diff --git a/source4/rpc_server/dnsserver/dcerpc_dnsserver.c b/source4/rpc_server/dnsserver/dcerpc_dnsserver.c index 841557814a0..bdf894634ce 100644 --- a/source4/rpc_server/dnsserver/dcerpc_dnsserver.c +++ b/source4/rpc_server/dnsserver/dcerpc_dnsserver.c @@ -2018,7 +2018,12 @@ static WERROR dcesrv_DnssrvOperation(struct dcesrv_call_state *dce_call, TALLOC_ &r->in.pData); } else { z = dnsserver_find_zone(dsstate->zones, r->in.pszZone); - if (z == NULL && request_filter == 0) { + /* + * In the case that request_filter is not 0 and z is NULL, + * the request is for a multizone operation, which we do not + * yet support, so just error on NULL zone name. + */ + if (z == NULL) { return WERR_DNS_ERROR_ZONE_DOES_NOT_EXIST; }