fuzz: add generic command argument fuzzer

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

src/fuzz/.gitignore

@@ -1,2 +1,4 @@
 config
 uapi
+stringlist
+cmd

src/fuzz/Makefile

@@ -2,10 +2,10 @@
 #
 # Copyright (C) 2018-2020 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
 
-all: config uapi stringlist
+all: config uapi stringlist cmd
 
 CFLAGS ?= -O3 -march=native -g
-CFLAGS += -fsanitize=fuzzer -fsanitize=address -std=gnu11 -idirafter ../uapi
+CFLAGS += -fsanitize=fuzzer -fsanitize=address -std=gnu11 -idirafter ../uapi -D_GNU_SOURCE
 CC := clang
 
 config: config.c ../config.c ../encoding.c
@@ -17,7 +17,10 @@ uapi: uapi.c ../ipc.c ../curve25519.c ../encoding.c
 stringlist: stringlist.c ../ipc.c ../curve25519.c ../encoding.c
 	$(CC) $(CFLAGS) -o $@ $<
 
+cmd: cmd.c $(wildcard ../*.c)
+	$(CC) $(CFLAGS) -D'RUNSTATEDIR="/var/empty"' -D'main(a,b)=wg_main(a,b)' -o $@ $^ -lmnl
+
 clean:
-	rm -f config uapi stringlist
+	rm -f config uapi stringlist cmd
 
 .PHONY: all clean

src/fuzz/cmd.c

@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018-2020 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <assert.h>
+
+const char *__asan_default_options()
+{
+	return "verbosity=1";
+}
+
+int wg_main(int argc, char *argv[]);
+
+static FILE *devnull;
+
+int LLVMFuzzerTestOneInput(const char *data, size_t data_len)
+{
+	char *argv[8192] = { 0 }, *args;
+	size_t argc = 0;
+	FILE *fake_stdin = NULL;
+
+	if (!devnull) {
+		assert((devnull = fopen("/dev/null", "r+")));
+		stdin = stdout = stderr = devnull;
+	}
+
+	assert((args = malloc(data_len)));
+	memcpy(args, data, data_len);
+	if (data_len)
+		args[data_len - 1] = '\0';
+
+	for (const char *arg = args; argc < 8192 && arg - args < data_len; arg += strlen(arg) + 1) {
+		if (arg[0])
+			assert((argv[argc++] = strdup(arg)));
+	}
+	if (!argc)
+		assert((argv[argc++] = strdup("no argv[0]!")));
+	if (argc > 2 && (!strcmp(argv[1], "show") || !strcmp(argv[1], "showconf") || !strcmp(argv[1], "set") || !strcmp(argv[1], "setconf") || !strcmp(argv[1], "addconf") || !strcmp(argv[1], "syncconf"))) {
+		free(argv[2]);
+		assert((argv[2] = strdup("wg0")));
+	}
+	if (argc >= 2 && !strcmp(argv[1], "pubkey")) {
+		char *arg;
+		size_t len;
+
+		for (size_t i = 2; i < argc; ++i)
+			free(argv[i]);
+		argc = 2;
+		arg = args;
+		for (; !arg[0]; ++arg);
+		arg += strlen(arg) + 1;
+		for (; !arg[0]; ++arg);
+		arg += strlen(arg) + 1;
+		len = data_len - (arg - args);
+		if (len <= 1)
+			goto done;
+		assert((fake_stdin = fmemopen(arg, len - 1, "r")));
+		stdin = fake_stdin;
+	}
+	wg_main(argc, argv);
+done:
+	for (size_t i = 0; i < argc; ++i)
+		free(argv[i]);
+	free(args);
+	if (fake_stdin)
+		fclose(fake_stdin);
+	return 0;
+}

src/fuzz/stringlist.c

@@ -4,9 +4,9 @@
  */
 
 #define RUNSTATEDIR "/var/empty"
+#include "../curve25519.c"
 #undef __linux__
 #include "../ipc.c"
-#include "../curve25519.c"
 #include "../encoding.c"
 
 #include <stdint.h>

src/fuzz/uapi.c

@@ -8,9 +8,9 @@
 static FILE *hacked_userspace_interface_file(const char *iface);
 #define stat(a, b) ({ return hacked_userspace_interface_file(iface); 0; })
 #define RUNSTATEDIR "/var/empty"
+#include "../curve25519.c"
 #undef __linux__
 #include "../ipc.c"
-#include "../curve25519.c"
 #include "../encoding.c"
 
 #include <stdint.h>