From 2a9e5a9a226a4628546dbaaea59ff78fe32a2352 Mon Sep 17 00:00:00 2001
From: Stefan Metzmacher <metze@samba.org>
Date: Thu, 1 Sep 2016 08:08:23 +0200
Subject: [PATCH] gensec/spnego: work around missing server mechListMIC in SMB
servers
BUG: https://bugzilla.samba.org/show_bug.cgi?id=11994
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Christian Ambach <ambi@samba.org>
Autobuild-User(master): Christian Ambach <ambi@samba.org>
Autobuild-Date(master): Fri Sep 2 18:10:44 CEST 2016 on sn-devel-144
(cherry picked from commit 9b45ba5cd53bd513eb777590815a0b8408af64e2)
---
auth/gensec/spnego.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 68 insertions(+), 1 deletion(-)
diff --git a/auth/gensec/spnego.c b/auth/gensec/spnego.c
index ef30ab7..5f5047a 100644
--- a/auth/gensec/spnego.c
+++ b/auth/gensec/spnego.c
@@ -55,9 +55,11 @@ struct spnego_state {
DATA_BLOB mech_types;
size_t num_targs;
+ bool downgraded;
bool mic_requested;
bool needs_mic_sign;
bool needs_mic_check;
+ bool may_skip_mic_check;
bool done_mic_check;
bool simulate_w2k;
@@ -434,6 +436,7 @@ static NTSTATUS gensec_spnego_parse_negTokenInit(struct gensec_security *gensec_
* Indicate the downgrade and request a
* mic.
*/
+ spnego_state->downgraded = true;
spnego_state->mic_requested = true;
break;
}
@@ -1078,7 +1081,7 @@ static NTSTATUS gensec_spnego_update(struct gensec_security *gensec_security, TA
DEBUG(3,("GENSEC SPNEGO: client preferred mech (%s) not accepted, server wants: %s\n",
gensec_get_name_by_oid(gensec_security, spnego_state->neg_oid),
gensec_get_name_by_oid(gensec_security, spnego.negTokenTarg.supportedMech)));
-
+ spnego_state->downgraded = true;
spnego_state->no_response_expected = false;
talloc_free(spnego_state->sub_sec_security);
nt_status = gensec_subcontext_start(spnego_state,
@@ -1135,6 +1138,23 @@ static NTSTATUS gensec_spnego_update(struct gensec_security *gensec_security, TA
return NT_STATUS_INVALID_PARAMETER;
}
+ if (spnego.negTokenTarg.mechListMIC.length == 0
+ && spnego_state->may_skip_mic_check) {
+ /*
+ * In this case we don't require
+ * a mechListMIC from the server.
+ *
+ * This works around bugs in the Azure
+ * and Apple spnego implementations.
+ *
+ * See
+ * https://bugzilla.samba.org/show_bug.cgi?id=11994
+ */
+ spnego_state->needs_mic_check = false;
+ nt_status = NT_STATUS_OK;
+ goto client_response;
+ }
+
nt_status = gensec_check_packet(spnego_state->sub_sec_security,
spnego_state->mech_types.data,
spnego_state->mech_types.length,
@@ -1190,9 +1210,56 @@ static NTSTATUS gensec_spnego_update(struct gensec_security *gensec_security, TA
*/
new_spnego = false;
}
+
break;
case SPNEGO_ACCEPT_INCOMPLETE:
+ if (spnego.negTokenTarg.mechListMIC.length > 0) {
+ new_spnego = true;
+ break;
+ }
+
+ if (spnego_state->downgraded) {
+ /*
+ * A downgrade should be protected if
+ * supported
+ */
+ break;
+ }
+
+ /*
+ * The caller may just asked for
+ * GENSEC_FEATURE_SESSION_KEY, this
+ * is only reflected in the want_features.
+ *
+ * As it will imply
+ * gensec_have_features(GENSEC_FEATURE_SIGN)
+ * to return true.
+ */
+ if (gensec_security->want_features & GENSEC_FEATURE_SIGN) {
+ break;
+ }
+ if (gensec_security->want_features & GENSEC_FEATURE_SEAL) {
+ break;
+ }
+ /*
+ * Here we're sure our preferred mech was
+ * selected by the server and our caller doesn't
+ * need GENSEC_FEATURE_SIGN nor
+ * GENSEC_FEATURE_SEAL support.
+ *
+ * In this case we don't require
+ * a mechListMIC from the server.
+ *
+ * This works around bugs in the Azure
+ * and Apple spnego implementations.
+ *
+ * See
+ * https://bugzilla.samba.org/show_bug.cgi?id=11994
+ */
+ spnego_state->may_skip_mic_check = true;
+ break;
+
case SPNEGO_REQUEST_MIC:
if (spnego.negTokenTarg.mechListMIC.length > 0) {
new_spnego = true;
--
2.8.0.rc3.226.g39d4020