Fix SPNEGO one-hop interop against old IIS

IIS 6.0 and similar return a zero length reponse buffer in the last
SPNEGO packet when context initiation is performed without mutual
authentication.  In this case the underlying Kerberos mechanism has
already completed successfully on the first invocation, and SPNEGO
does not expect a mech response token in the answer.  If we get an
empty mech response token when the mech is complete during
negotiation, ignore it.

[ghudson@mit.edu: small code style and commit message changes]

(cherry picked from commit 37af638b742dbd642eb70092e4f7781c3f69d86d)

ticket: 7842 (new)
version_fixed: 1.10.8
status: resolved

diff --git a/src/lib/gssapi/spnego/spnego_mech.c b/src/lib/gssapi/spnego/spnego_mech.c
index fe931408f5fda9b2d974002a2808f9542259484e..f26db635a8494d104c5662ae431b9d00955a5c75 100644 (file)
--- a/src/lib/gssapi/spnego/spnego_mech.c
+++ b/src/lib/gssapi/spnego/spnego_mech.c
@@ -749,6 +749,12 @@ init_ctx_nego(OM_uint32 *minor_status, spnego_gss_ctx_id_t sc,
                        map_errcode(minor_status);
                        ret = GSS_S_DEFECTIVE_TOKEN;
                }
+       } else if ((*responseToken)->length == 0 && sc->mech_complete) {
+               /* Handle old IIS servers returning empty token instead of
+                * null tokens in the non-mutual auth case. */
+               *negState = ACCEPT_COMPLETE;
+               *tokflag = NO_TOKEN_SEND;
+               ret = GSS_S_COMPLETE;
        } else if (sc->mech_complete) {
                /* Reject spurious mech token. */
                ret = GSS_S_DEFECTIVE_TOKEN;