From 8bd69574bdfba221a365c3d40713e6d13463ae79 Mon Sep 17 00:00:00 2001
From: Edward Thomson <ethomson@edwardthomson.com>
Date: Fri, 17 Nov 2023 10:29:08 +0000
Subject: [PATCH] fuzzers: provide util functions like repo init

Many fuzzers will need to operate with a repository; extract the
repository initialization from downloads_refs_fuzzer.c into its own
utility area.
---
 fuzzers/CMakeLists.txt         |  5 +++-
 fuzzers/download_refs_fuzzer.c | 35 +++--------------------
 fuzzers/fuzzer_utils.c         | 51 ++++++++++++++++++++++++++++++++++
 fuzzers/fuzzer_utils.h         | 14 ++++++++++
 4 files changed, 73 insertions(+), 32 deletions(-)
 create mode 100644 fuzzers/fuzzer_utils.c
 create mode 100644 fuzzers/fuzzer_utils.h

diff --git a/fuzzers/CMakeLists.txt b/fuzzers/CMakeLists.txt
index a2c19ed40..01f0f5199 100644
--- a/fuzzers/CMakeLists.txt
+++ b/fuzzers/CMakeLists.txt
@@ -12,10 +12,13 @@ foreach(fuzz_target_src ${SRC_FUZZERS})
 	string(REPLACE ".c" "" fuzz_target_name ${fuzz_target_src})
 	string(REPLACE "_fuzzer" "" fuzz_name ${fuzz_target_name})
 
-	set(${fuzz_target_name}_SOURCES ${fuzz_target_src} ${LIBGIT2_OBJECTS})
+	set(${fuzz_target_name}_SOURCES
+		${fuzz_target_src} "fuzzer_utils.c" ${LIBGIT2_OBJECTS})
+
 	if(USE_STANDALONE_FUZZERS)
 		list(APPEND ${fuzz_target_name}_SOURCES "standalone_driver.c")
 	endif()
+
 	add_executable(${fuzz_target_name} ${${fuzz_target_name}_SOURCES})
 	set_target_properties(${fuzz_target_name} PROPERTIES C_STANDARD 90)
 
diff --git a/fuzzers/download_refs_fuzzer.c b/fuzzers/download_refs_fuzzer.c
index ff95cd107..c2b80ccb1 100644
--- a/fuzzers/download_refs_fuzzer.c
+++ b/fuzzers/download_refs_fuzzer.c
@@ -16,6 +16,7 @@
 #include "futils.h"
 
 #include "standalone_driver.h"
+#include "fuzzer_utils.h"
 
 #define UNUSED(x) (void)(x)
 
@@ -157,33 +158,10 @@ static int fuzzer_transport_cb(git_transport **out, git_remote *owner, void *par
 	return git_transport_smart(out, owner, &def);
 }
 
-static void fuzzer_git_abort(const char *op)
-{
-	const git_error *err = git_error_last();
-	fprintf(stderr, "unexpected libgit error: %s: %s\n",
-		op, err ? err->message : "<none>");
-	abort();
-}
-
 int LLVMFuzzerInitialize(int *argc, char ***argv)
 {
-#if defined(_WIN32)
-	char tmpdir[MAX_PATH], path[MAX_PATH];
-
-	if (GetTempPath((DWORD)sizeof(tmpdir), tmpdir) == 0)
-		abort();
-
-	if (GetTempFileName(tmpdir, "lg2", 1, path) == 0)
-		abort();
-
-	if (git_futils_mkdir(path, 0700, 0) < 0)
-		abort();
-#else
-	char path[] = "/tmp/git2.XXXXXX";
-
-	if (mkdtemp(path) != path)
-		abort();
-#endif
+	UNUSED(argc);
+	UNUSED(argv);
 
 	if (git_libgit2_init() < 0)
 		abort();
@@ -191,12 +169,7 @@ int LLVMFuzzerInitialize(int *argc, char ***argv)
 	if (git_libgit2_opts(GIT_OPT_SET_PACK_MAX_OBJECTS, 10000000) < 0)
 		abort();
 
-	UNUSED(argc);
-	UNUSED(argv);
-
-	if (git_repository_init(&repo, path, 1) < 0)
-		fuzzer_git_abort("git_repository_init");
-
+	repo = fuzzer_repo_init();
 	return 0;
 }
 
diff --git a/fuzzers/fuzzer_utils.c b/fuzzers/fuzzer_utils.c
new file mode 100644
index 000000000..cde5065da
--- /dev/null
+++ b/fuzzers/fuzzer_utils.c
@@ -0,0 +1,51 @@
+/*
+ * 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 <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "git2.h"
+#include "futils.h"
+
+#include "fuzzer_utils.h"
+
+void fuzzer_git_abort(const char *op)
+{
+	const git_error *err = git_error_last();
+	fprintf(stderr, "unexpected libgit error: %s: %s\n",
+		op, err ? err->message : "<none>");
+	abort();
+}
+
+git_repository *fuzzer_repo_init(void)
+{
+	git_repository *repo;
+
+#if defined(_WIN32)
+	char tmpdir[MAX_PATH], path[MAX_PATH];
+
+	if (GetTempPath((DWORD)sizeof(tmpdir), tmpdir) == 0)
+		abort();
+
+	if (GetTempFileName(tmpdir, "lg2", 1, path) == 0)
+		abort();
+
+	if (git_futils_mkdir(path, 0700, 0) < 0)
+		abort();
+#else
+	char path[] = "/tmp/git2.XXXXXX";
+
+	if (mkdtemp(path) != path)
+		abort();
+#endif
+
+	if (git_repository_init(&repo, path, 1) < 0)
+		fuzzer_git_abort("git_repository_init");
+
+	return repo;
+}
diff --git a/fuzzers/fuzzer_utils.h b/fuzzers/fuzzer_utils.h
new file mode 100644
index 000000000..6b67c9a61
--- /dev/null
+++ b/fuzzers/fuzzer_utils.h
@@ -0,0 +1,14 @@
+/*
+ * 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.
+ */
+
+#ifndef INCLUDE_fuzzer_utils_h__
+#define INCLUDE_fuzzer_utils_h__
+
+extern void fuzzer_git_abort(const char *op);
+extern git_repository *fuzzer_repo_init(void);
+
+#endif