helper-fuzzer-demarshallers: Add an helper for fuzzy testing demarshallers code

See usage with AFL in the source file initial comment.

Signed-off-by: Frediano Ziglio <fziglio@redhat.com>

tests/Makefile.am

@@ -93,6 +93,22 @@ test_utils_LDADD =					\
 	$(NULL)
 
 
+noinst_PROGRAMS += helper_fuzzer_demarshallers
+helper_fuzzer_demarshallers_SOURCES =	\
+	helper-fuzzer-demarshallers.c	\
+	$(NULL)
+helper_fuzzer_demarshallers_CFLAGS =	\
+	-I$(top_srcdir)			\
+	$(GLIB2_CFLAGS)			\
+	$(PROTOCOL_CFLAGS)		\
+	$(NULL)
+helper_fuzzer_demarshallers_LDADD =				\
+	$(top_builddir)/common/libspice-common.la	        \
+	$(top_builddir)/common/libspice-common-server.la	\
+	$(top_builddir)/common/libspice-common-client.la	\
+	$(NULL)
+
+
 # Avoid need for python(pyparsing) by end users
 TEST_MARSHALLERS =				\
 	generated_test_marshallers.c		\

tests/helper-fuzzer-demarshallers.c

@@ -0,0 +1,104 @@
+/*
+   Copyright (C) 2020 Red Hat, Inc.
+
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, see <http://www.gnu.org/licenses/>.
+*/
+/* Helper to test messages demarshalling using AFL (American Fuzzy Lop) fuzzer.
+ *
+ * To use you should:
+ * 1- build enabling AFL. The usage of ElectricFence is to detect some
+ *    additional possible buffer overflow, AFL required the program to crash
+ *    in case of errors
+ * $ make clean
+ * $ make CC=afl-gcc CFLAGS='-O2 -fno-omit-frame-pointer' LDFLAGS='/usr/lib64/libefence.a'
+ * 2- create a starting testcase, I used a simple file, you can create with
+ * $ mkdir afl_testcases
+ * $ perl -e 'print "\x02\x01\x00"' > afl_testcases/one
+ * 3- run AFL, the export is to allow malloc(0), not an issue nowadays
+ * $ export EF_ALLOW_MALLOC_0=1
+ * $ mkdir afl_findings
+ * $ afl-fuzz -i afl_testcases -o afl_findings -- ./tests/helper_fuzzer_demarshallers @@
+ */
+#undef NDEBUG
+#include <config.h>
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <common/demarshallers.h>
+
+typedef uint8_t *
+spice_parse_t(uint8_t *message_start, uint8_t *message_end,
+              uint32_t channel, uint16_t message_type, SPICE_GNUC_UNUSED int minor,
+              size_t *size_out, message_destructor_t *free_message);
+
+spice_parse_t spice_parse_msg, spice_parse_reply;
+
+int main(int argc, char **argv)
+{
+    // First argument filename of the testcase to handle
+    if (argc < 2) {
+        return 1;
+    }
+
+    FILE *f = fopen(argv[1], "rb");
+    if (!f) {
+        return 1;
+    }
+
+    fseek(f, 0L, SEEK_END);
+    off_t sz = ftello(f);
+    assert(sz >= 0);
+    rewind(f);
+
+    // Testcase must have at least 3 bytes, 1 for channel, 2 for message type
+    if (sz < 3) {
+        fclose(f);
+        return 1;
+    }
+
+#define READ(x) assert(fread(&x, 1, sizeof(x), f) == sizeof(x))
+
+    uint8_t channel;
+    READ(channel);
+
+    // Low bit select client or server
+    spice_parse_t *parse_func = channel & 1 ? spice_parse_reply : spice_parse_msg;
+    channel >>= 1;
+
+    uint16_t type;
+    READ(type);
+
+    sz -= 3;
+
+    // Read the rest of the file into a malloced buffer
+    // Don't use GLib function, normal libc functions will be overwritten by
+    // ElectricFence if you are using it
+    uint8_t *p = malloc(sz);
+    assert(fread(p, 1, sz, f) == (size_t) sz);
+    fclose(f);
+    f = NULL;
+
+    // Parse the buffer as a SPICE message
+    message_destructor_t release = NULL;
+    size_t out_size;
+    uint8_t *msg = parse_func(p, p + sz, channel, type, 0, &out_size, &release);
+    if (msg && release) {
+        release(msg);
+    }
+
+    free(p);
+
+    return 0;
+}

tests/meson.build

@@ -53,3 +53,12 @@ if gdk_pixbuf_dep.found()
                   dependencies : [spice_common_dep, gdk_pixbuf_dep],
                   install : false), timeout : 120)
 endif
+
+#
+# helper_fuzzer_demarshallers
+#
+if spice_common_generate_client_code and spice_common_generate_server_code
+  executable('helper_fuzzer_demarshallers', 'helper-fuzzer-demarshallers.c',
+             dependencies : [tests_deps, spice_common_server_dep, spice_common_client_dep],
+             install : false)
+endif