dumpelf: add libFuzzer support

Now you can build dumpelf with libFuzzer and beat the hell out of it.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

2 files changed, 35 insertions, 10 deletions

diff --git a/Makefile b/Makefile
index 8e7b183..9a2c07c 100644
--- a/Makefile
+++ b/Makefile
@@ -115,7 +115,7 @@ afl-fuzz: clean
 		"afl-fuzz -t 100 -i tests/fuzz/small/ -o findings/ ./scanelf -s '*' -axetrnibSDIYZB @@"
 
 # Not all objects support libfuzzer.
-LIBFUZZER_TARGETS =
+LIBFUZZER_TARGETS = dumpelf
 LIBFUZZER_FLAGS = \
 	-fsanitize=fuzzer \
 	-fsanitize-coverage=edge
diff --git a/dumpelf.c b/dumpelf.c
index bc634f0..342251f 100644
--- a/dumpelf.c
+++ b/dumpelf.c
@@ -11,7 +11,6 @@ const char argv0[] = "dumpelf";
 #include "paxinc.h"
 
 /* prototypes */
-static void dumpelf(const char *filename, size_t file_cnt);
 static void dump_ehdr(elfobj *elf, const void *ehdr);
 static void dump_phdr(elfobj *elf, const void *phdr, size_t phdr_cnt);
 static void dump_shdr(elfobj *elf, const void *shdr, size_t shdr_cnt, const char *section_name);
@@ -31,15 +30,10 @@ static char be_verbose = 0;
 static const void *phdr_dynamic_void;
 
 /* dump all internal elf info */
-static void dumpelf(const char *filename, size_t file_cnt)
+static void dumpelf(elfobj *elf, size_t file_cnt)
 {
-	elfobj *elf;
 	size_t i, b;
 
-	/* verify this is real ELF */
-	if ((elf = readelf(filename)) == NULL)
-		return;
-
 	phdr_dynamic_void = NULL;
 
 	printf("#include <elf.h>\n");
@@ -50,7 +44,7 @@ static void dumpelf(const char *filename, size_t file_cnt)
 		" * ELF dump of '%s'\n"
 		" *     %ji (0x%jX) bytes\n"
 		" */\n\n",
-		filename, elf->len, elf->len);
+		elf->filename, elf->len, elf->len);
 
 	/* setup the struct to namespace this elf */
 #define MAKE_STRUCT(B) \
@@ -148,6 +142,17 @@ static void dumpelf(const char *filename, size_t file_cnt)
 		printf(" /* no dynamic tags ! */ ");
 	}
 	printf("};\n");
+}
+
+static void dumpelf_file(const char *filename, size_t file_cnt)
+{
+	elfobj *elf = readelf(filename);
+
+	/* verify this is real ELF */
+	if (elf == NULL)
+		return;
+
+	dumpelf(elf, file_cnt);
 
 	/* get out of here */
 	unreadelf(elf);
@@ -570,10 +575,29 @@ static void parseargs(int argc, char *argv[])
 	size_t file_cnt = 0;
 
 	while (optind < argc)
-		dumpelf(argv[optind++], file_cnt++);
+		dumpelf_file(argv[optind++], file_cnt++);
 	}
 }
 
+#if PAX_UTILS_LIBFUZZ
+int LLVMFuzzerInitialize(int *argc, char ***argv)
+{
+	(void)argc;
+	(void)argv;
+	(void)parseargs;
+	security_init(false);
+	return 0;
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
+{
+	elfobj *elf = readelf_buffer("libFuzzer", data, size);
+	if (elf == NULL)
+		return 0;
+	dumpelf(elf, 0);
+	return 0;
+}
+#else
 int main(int argc, char *argv[])
 {
 	security_init(false);
@@ -582,3 +606,4 @@ int main(int argc, char *argv[])
 	parseargs(argc, argv);
 	return EXIT_SUCCESS;
 }
+#endif