gss: SAnon - the Simple Anonymous GSS-API mechanism

Add support for SAnon, a simple key agreement protocol that provides no
authentication of initiator or acceptor using x25519 ECDH key exchange.
See doc/standardization/draft-howard-gss-sanon-xx.txt for a protocol
description.

lib/gssapi/sanon/export_sec_context.c

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2019-2020, AuriStor, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in
+ *   the documentation and/or other materials provided with the
+ *   distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "sanon_locl.h"
+
+OM_uint32 GSSAPI_CALLCONV
+_gss_sanon_export_sec_context(OM_uint32 *minor,
+			      gss_ctx_id_t *context_handle,
+			      gss_buffer_t interprocess_token)
+{
+    OM_uint32 major;
+    const sanon_ctx sc = (sanon_ctx)*context_handle;
+
+    if (sc->rfc4121 == GSS_C_NO_CONTEXT) {
+        _mg_buffer_zero(interprocess_token);
+	*minor = 0;
+	return GSS_S_UNAVAILABLE;
+    }
+
+    major = gss_export_sec_context(minor, &sc->rfc4121, interprocess_token);
+    if (major == GSS_S_COMPLETE) {
+	_gss_sanon_delete_sec_context(minor, context_handle,
+				      GSS_C_NO_BUFFER);
+    }
+    return major;
+}