Merge pull request #4752 from nelhage/fuzz-config

Add a fuzzer for config files

fuzzers/config_file_fuzzer.c

+/*
+ * libgit2 config file parser fuzz target.
+ *
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include <git2.h>
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <limits.h>
+#include <errno.h>
+
+#define UNUSED(x) (void)(x)
+
+int foreach_cb(const git_config_entry *entry, void *payload)
+{
+	UNUSED(entry);
+	UNUSED(payload);
+
+	return 0;
+}
+
+static char path[] = "/tmp/git.XXXXXX";
+static int fd = -1;
+
+int LLVMFuzzerInitialize(int *argc, char ***argv)
+{
+	UNUSED(argc);
+	UNUSED(argv);
+
+	if (git_libgit2_init() < 0)
+		abort();
+	fd = mkstemp(path);
+	if (fd < 0) {
+		abort();
+	}
+
+	return 0;
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
+{
+	git_config *cfg = NULL;
+	int err = 0;
+	size_t total = 0;
+
+	if (ftruncate(fd, 0) !=0 ) {
+		abort();
+	}
+	if (lseek(fd, 0, SEEK_SET) != 0) {
+		abort();
+	}
+
+	while (total < size) {
+		ssize_t written = write(fd, data, size);
+		if (written < 0 && errno != EINTR)
+			abort();
+		if (written < 0)
+			continue;
+		total += written;
+	}
+
+	err = git_config_open_ondisk(&cfg, path);
+	if (err == 0) {
+		git_config_foreach(cfg, foreach_cb, NULL);
+		git_config_free(cfg);
+	}
+
+	return 0;
+}

fuzzers/corpora/config_file/git2.dat

+[core]
+	repositoryformatversion = 0
+	filemode = true
+	bare = false
+	logallrefupdates = true
+[remote "origin"]
+	url = git@github.com:libgit2/libgit2
+	fetch = +refs/heads/*:refs/remotes/origin/*
+[branch "master"]
+	remote = origin
+	merge = refs/heads/master