A test shim in testing that removes randomness

This means that added caveats will be deterministic, and thus testable, without
having to alter the underlying code.

Makefile.am

@@ -1,4 +1,4 @@
-# Copyright (c) 2014, Robert Escriva
+# Copyright (c) 2014-2016, Robert Escriva
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -65,9 +65,15 @@ EXTRA_DIST += test/python-hmac-sanity-check
 EXTRA_DIST += test/python-hmac-sanity-check.sh
 EXTRA_DIST += test/readme.sh
 
+check_LTLIBRARIES = libmacaroons-shim.la
+
+libmacaroons_shim_la_SOURCES = shim.c
+libmacaroons_shim_la_LIBADD =  $(SODIUM_LIBS)
+libmacaroons_shim_la_LDFLAGS = -module -avoid-version -rpath /evil/libtool/hack/to/force/shared/lib/creation
+
 TESTS  =
 TESTS += test/python-hmac-sanity-check.sh
-#TESTS += test/readme.sh
+TESTS += test/readme.sh
 
 #################################### Python ####################################
 

port.c

@@ -126,7 +126,7 @@ macaroon_secretbox_open(const unsigned char* enc_key,
 void
 macaroon_bin2hex(const unsigned char* bin, size_t bin_sz, char* hex)
 {
-    void* ptr = sodium_bin2hex(hex, bin_sz * 2, bin, bin_sz);
+    void* ptr = sodium_bin2hex(hex, bin_sz * 2 + 1, bin, bin_sz);
     assert(ptr == hex);
 }
 

shim.c

@@ -0,0 +1,43 @@
+/* Copyright (c) 2016, Robert Escriva
+ * 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.
+ *     * Neither the name of this project nor the names of its contributors may
+ *       be used to endorse or promote products derived from this software
+ *       without specific prior written permission.
+ *
+ * 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 OWNER 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.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+/* C */
+#include <stdlib.h>
+
+/* sodium */
+#include <sodium/utils.h>
+
+__attribute__ ((visibility ("default")))
+void randombytes_buf(void * const buf, const size_t size)
+{
+    sodium_memzero(buf, size);
+}

test/env.sh

@@ -2,4 +2,5 @@ export MACAROONS_SRCDIR="$1"
 export MACAROONS_BUILDDIR="$2"
 export MACAROONS_VERSION="$3"
 
+export LD_PRELOAD="${MACAROONS_BUILDDIR}/.libs/libmacaroons-shim.so"
 export PYTHONPATH="${MACAROONS_BUILDDIR}"/bindings/python/.libs:${PYTHONPATH}