MITKRB5-SA-2010-002 CVE-2010-0628 denial of service in SPNEGO

The SPNEGO implementation in krb5-1.7 and later could crash due to
assertion failure when receiving some sorts of invalid GSS-API tokens.

ticket: 6690
target_version: 1.8.1
tags: pullup

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@23832 dc483132-0cff-0310-8789-dd5450dbe970

diff --git a/src/lib/gssapi/spnego/spnego_mech.c b/src/lib/gssapi/spnego/spnego_mech.c
index 95e450979c0d06ef5d17851b36ba6972f2ae287e..86ba89a399ddbe9ccf9e364add3e2d588826bc7a 100644 (file)
--- a/src/lib/gssapi/spnego/spnego_mech.c
+++ b/src/lib/gssapi/spnego/spnego_mech.c
@@ -1593,7 +1593,7 @@ spnego_gss_accept_sec_context(
        spnego_gss_ctx_id_t sc = NULL;
        spnego_gss_cred_id_t spcred = NULL;
        OM_uint32 mechstat = GSS_S_FAILURE;
-       int sendTokenInit = 0;
+       int sendTokenInit = 0, tmpret;
 
        mechtok_in = mic_in = mic_out = GSS_C_NO_BUFFER;
 
@@ -1651,7 +1651,6 @@ spnego_gss_accept_sec_context(
                if (delegated_cred_handle != NULL)
                        *delegated_cred_handle = GSS_C_NO_CREDENTIAL;
                if (input_token->length == 0) {
-                       sendTokenInit = 1;
                        ret = acc_ctx_hints(minor_status,
                                            context_handle, spcred,
                                            &mic_out,
@@ -1659,6 +1658,7 @@ spnego_gss_accept_sec_context(
                                            &return_token);
                        if (ret != GSS_S_COMPLETE)
                                goto cleanup;
+                       sendTokenInit = 1;
                        ret = GSS_S_CONTINUE_NEEDED;
                } else {
                        /* Can set negState to REQUEST_MIC */
@@ -1713,27 +1713,21 @@ spnego_gss_accept_sec_context(
                                 &negState, &return_token);
        }
 cleanup:
-       if (return_token != NO_TOKEN_SEND && return_token != CHECK_MIC) {
-               /* For acceptor-sends-first send a tokenInit */
-               int tmpret;
-
+       if (return_token == INIT_TOKEN_SEND && sendTokenInit) {
                assert(sc != NULL);
-
-               if (sendTokenInit) {
-                       tmpret = make_spnego_tokenInit_msg(sc,
-                                                          1,
-                                                          mic_out,
-                                                          0,
-                                                          GSS_C_NO_BUFFER,
-                                                          return_token,
-                                                          output_token);
-               } else {
-                       tmpret = make_spnego_tokenTarg_msg(negState,
-                                                          sc ? sc->internal_mech : GSS_C_NO_OID,
-                                                          &mechtok_out, mic_out,
-                                                          return_token,
-                                                          output_token);
-               }
+               tmpret = make_spnego_tokenInit_msg(sc, 1, mic_out, 0,
+                                                  GSS_C_NO_BUFFER,
+                                                  return_token, output_token);
+               if (tmpret < 0)
+                       ret = GSS_S_FAILURE;
+       } else if (return_token != NO_TOKEN_SEND &&
+                  return_token != CHECK_MIC) {
+               tmpret = make_spnego_tokenTarg_msg(negState,
+                                                  sc ? sc->internal_mech :
+                                                  GSS_C_NO_OID,
+                                                  &mechtok_out, mic_out,
+                                                  return_token,
+                                                  output_token);
                if (tmpret < 0)
                        ret = GSS_S_FAILURE;
        }