libfreerdp-core: fix possible crash on unauthorized TS Gateway error

diff --git a/libfreerdp/core/gateway/rpc.c b/libfreerdp/core/gateway/rpc.c
index ae024cd..5a3760f 100644 (file)
--- a/libfreerdp/core/gateway/rpc.c
+++ b/libfreerdp/core/gateway/rpc.c
@@ -360,6 +360,12 @@ int rpc_write(rdpRpc* rpc, BYTE* data, int length, UINT16 opnum)
 
        ntlm = rpc->ntlm;
 
+       if ((!ntlm) || (!ntlm->table))
+       {
+               fprintf(stderr, "rpc_write: invalid ntlm context\n");
+               return -1;
+       }
+
        if (ntlm->table->QueryContextAttributes(&ntlm->context, SECPKG_ATTR_SIZES, &ntlm->ContextSizes) != SEC_E_OK)
        {
                fprintf(stderr, "QueryContextAttributes SECPKG_ATTR_SIZES failure\n");