krb5 commit: Add SPNEGO special case for NTLMSSP+MechListMIC

[Greg Hudson]

https://github.com/krb5/krb5/commit/cb96ca52a3354e5a0ea52e12495ff375de54f9b7
commit cb96ca52a3354e5a0ea52e12495ff375de54f9b7
Author: Simo Sorce <simo at redhat.com>
Date:   Wed Mar 30 13:00:19 2016 -0400

    Add SPNEGO special case for NTLMSSP+MechListMIC
    
    MS-SPNG section 3.3.5.1 documents an odd behavior the SPNEGO layer
    needs to implement specifically for the NTLMSSP mechanism.  This is
    required for compatibility with Windows services.
    
    ticket: 8423 (new)

 src/lib/gssapi/spnego/spnego_mech.c |   48 +++++++++++++++++++++++++++++++---
 1 files changed, 43 insertions(+), 5 deletions(-)

diff --git a/src/lib/gssapi/spnego/spnego_mech.c b/src/lib/gssapi/spnego/spnego_mech.c
index bcebba8..7862d98 100644
--- a/src/lib/gssapi/spnego/spnego_mech.c
+++ b/src/lib/gssapi/spnego/spnego_mech.c
@@ -507,6 +507,45 @@ mech_requires_mechlistMIC(spnego_gss_ctx_id_t sc)
 	return result;
 }
 
+/* iso(1) org(3) dod(6) internet(1) private(4) enterprises(1) Microsoft(311)
+ * security(2) mechanisms(2) NTLM(10) */
+static const gss_OID_desc gss_mech_ntlmssp_oid =
+	{ 10, "\x2b\x06\x01\x04\x01\x82\x37\x02\x02\x0a" };
+
+/* iso(1) org(3) dod(6) internet(1) private(4) enterprises(1) samba(7165)
+ * gssntlmssp(655) controls(1) ntlmssp_reset_crypto(3) */
+static const gss_OID_desc ntlmssp_reset_crypto_oid =
+	{ 11, "\x2B\x06\x01\x04\x01\xB7\x7D\x85\x0F\x01\x03" };
+
+/*
+ * MS-SPNG section 3.3.5.1 warns that the NTLM mechanism requires special
+ * handling of the crypto state to interop with Windows.  If the mechanism for
+ * sc is SPNEGO, invoke a mechanism-specific operation on the context to reset
+ * the RC4 state after producing or verifying a MIC.  Ignore a result of
+ * GSS_S_UNAVAILABLE for compatibility with older versions of the mechanism
+ * that do not support this functionality.
+ */
+static OM_uint32
+ntlmssp_reset_crypto_state(OM_uint32 *minor_status, spnego_gss_ctx_id_t sc,
+			   OM_uint32 verify)
+{
+	OM_uint32 major, minor;
+	gss_buffer_desc value;
+
+	if (!g_OID_equal(sc->internal_mech, &gss_mech_ntlmssp_oid))
+		return GSS_S_COMPLETE;
+
+	value.length = sizeof(verify);
+	value.value = &verify;
+	major = gss_set_sec_context_option(&minor, &sc->ctx_handle,
+					   (gss_OID)&ntlmssp_reset_crypto_oid,
+					   &value);
+	if (major == GSS_S_UNAVAILABLE)
+		return GSS_S_COMPLETE;
+	*minor_status = minor;
+	return major;
+}
+
 /*
  * Both initiator and acceptor call here to verify and/or create mechListMIC,
  * and to consistency-check the MIC state.  handle_mic is invoked only if the
@@ -588,6 +627,8 @@ process_mic(OM_uint32 *minor_status, gss_buffer_t mic_in,
 		ret = gss_verify_mic(minor_status, sc->ctx_handle,
 				     &sc->DER_mechTypes,
 				     mic_in, &qop_state);
+		if (ret == GSS_S_COMPLETE)
+			ret = ntlmssp_reset_crypto_state(minor_status, sc, 1);
 		if (ret != GSS_S_COMPLETE) {
 			*negState = REJECT;
 			*tokflag = ERROR_TOKEN_SEND;
@@ -602,6 +643,8 @@ process_mic(OM_uint32 *minor_status, gss_buffer_t mic_in,
 				  GSS_C_QOP_DEFAULT,
 				  &sc->DER_mechTypes,
 				  &tmpmic);
+		if (ret == GSS_S_COMPLETE)
+			ret = ntlmssp_reset_crypto_state(minor_status, sc, 0);
 		if (ret != GSS_S_COMPLETE) {
 			gss_release_buffer(&tmpmin, &tmpmic);
 			*tokflag = NO_TOKEN_SEND;
@@ -804,11 +847,6 @@ init_ctx_nego(OM_uint32 *minor_status, spnego_gss_ctx_id_t sc,
 	return ret;
 }
 
-/* iso(1) org(3) dod(6) internet(1) private(4) enterprise(1) Microsoft(311)
- * security(2) mechanisms(2) NTLM(10) */
-static const gss_OID_desc gss_mech_ntlmssp_oid =
-	{ 10, "\x2b\x06\x01\x04\x01\x82\x37\x02\x02\x0a" };
-
 /*
  * Handle acceptor's counter-proposal of an alternative mechanism.
  */