Do mech fallback for first SPNEGO context token

When producing the first SPNEGO security context token, if the first
mechanism's init_sec_context fails, fall back to a later mechanism.

This fixes a regression in 1.10 for SPNEGO initiators using non-krb5
credentials.  The identity selection work causes errors to be deferred
from krb5's acquire_cred in some cases, which means SPNEGO doesn't see
an error until it tries the krb5 init_sec_context.

ticket: 6936
target_version: 1.10
tags: pullup

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@25591 dc483132-0cff-0310-8789-dd5450dbe970

diff --git a/src/lib/gssapi/spnego/spnego_mech.c b/src/lib/gssapi/spnego/spnego_mech.c
index ca23b2248e5512a667338f4c0ae74f2a4d8955e8..dfb9bada48691e269edc1a8ea447cec304c3f5b4 100644 (file)
--- a/src/lib/gssapi/spnego/spnego_mech.c
+++ b/src/lib/gssapi/spnego/spnego_mech.c
@@ -821,7 +821,7 @@ init_ctx_call_init(OM_uint32 *minor_status,
                   OM_uint32 *negState,
                   send_token_flag *send_token)
 {
-       OM_uint32 ret;
+       OM_uint32 ret, tmpret, tmpmin;
        gss_cred_id_t mcred;
 
        mcred = (spcred == NULL) ? GSS_C_NO_CREDENTIAL : spcred->mcred;
@@ -862,15 +862,44 @@ init_ctx_call_init(OM_uint32 *minor_status,
                        *negState = ACCEPT_INCOMPLETE;
                        ret = GSS_S_CONTINUE_NEEDED;
                }
-       } else if (ret != GSS_S_CONTINUE_NEEDED) {
-               if (*send_token == INIT_TOKEN_SEND) {
-                       /* Don't output token on error if first call. */
-                       *send_token = NO_TOKEN_SEND;
-               } else {
-                       *send_token = ERROR_TOKEN_SEND;
-               }
+               return ret;
+       }
+
+       if (ret == GSS_S_CONTINUE_NEEDED)
+               return ret;
+
+       if (*send_token != INIT_TOKEN_SEND) {
+               *send_token = ERROR_TOKEN_SEND;
                *negState = REJECT;
+               return ret;
        }
+
+       /*
+        * Since this is the first token, we can fall back to later mechanisms
+        * in the list.  Since the mechanism list is expected to be short, we
+        * can do this with recursion.  If all mechanisms produce errors, the
+        * caller should get the error from the first mech in the list.
+        */
+       memmove(sc->mech_set->elements, sc->mech_set->elements + 1,
+               --sc->mech_set->count * sizeof(*sc->mech_set->elements));
+       if (sc->mech_set->count == 0)
+               goto fail;
+       gss_release_buffer(&tmpmin, &sc->DER_mechTypes);
+       if (put_mech_set(sc->mech_set, &sc->DER_mechTypes) < 0)
+               goto fail;
+       tmpret = init_ctx_call_init(&tmpmin, sc, spcred, target_name,
+                                   req_flags, time_req, mechtok_in,
+                                   actual_mech, mechtok_out, ret_flags,
+                                   time_rec, negState, send_token);
+       if (HARD_ERROR(tmpret))
+               goto fail;
+       *minor_status = tmpmin;
+       return tmpret;
+
+fail:
+       /* Don't output token on error from first call. */
+       *send_token = NO_TOKEN_SEND;
+       *negState = REJECT;
        return ret;
 }