Add support for fuzzing with AFL

Reviewed-by: Ben Laurie <ben@links.org>

MR: #2740

12 files changed, 118 insertions, 35 deletions

diff --git a/fuzz/README.md b/fuzz/README.md
index 9b6d7d7980..e9ec88b8c6 100644
--- a/fuzz/README.md
+++ b/fuzz/README.md
@@ -1,5 +1,8 @@
 # I Can Haz Fuzz?
 
+LibFuzzer
+=========
+
 Or, how to fuzz OpenSSL with [libfuzzer](llvm.org/docs/LibFuzzer.html).
 
 Starting from a vanilla+OpenSSH server Ubuntu install.
@@ -32,7 +35,10 @@ https://github.com/llvm-mirror/llvm/tree/master/lib/Fuzzer if you prefer):
 
 Configure for fuzzing:
 
-    $ CC=clang ./config enable-fuzz enable-asan enable-ubsan no-shared
+    $ CC=clang ./config enable-fuzz-libfuzzer \
+            --with-fuzzer-include=../../svn-work/Fuzzer \
+            --with-fuzzer-lib=../../svn-work/Fuzzer/libFuzzer \
+            enable-asan enable-ubsan no-shared
     $ sudo apt-get install make
     $ LDCMD=clang++ make -j
     $ fuzz/helper.py <fuzzer> <arguments>
@@ -45,3 +51,20 @@ If you get a crash, you should find a corresponding input file in
 `fuzz/corpora/<fuzzer>-crash/`. You can reproduce the crash with
 
     $ fuzz/<fuzzer> <crashfile>
+
+AFL
+===
+
+Configure for fuzzing:
+
+    $ sudo apt-get install afl-clang
+    $ CC=afl-clang-fast ./config enable-fuzz-afl no-shared
+    $ make
+
+Run one of the fuzzers:
+
+    $ afl-fuzz fuzz/<fuzzer> -i fuzz/corpora/<fuzzer> -o fuzz/corpora/<fuzzer>/out <fuzzer> <arguments>
+
+Where `<fuzzer>` is one of the executables in `fuzz/`. Most fuzzers do not
+need any command line arguments, but, for example, `asn1` needs the name of a
+data type.
diff --git a/fuzz/asn1.c b/fuzz/asn1.c
index fdf4c5ee29..66825f1b2c 100644
--- a/fuzz/asn1.c
+++ b/fuzz/asn1.c
@@ -60,7 +60,7 @@ static const ASN1_ITEM *item_type[] = {
     NULL
 };
 
-int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len) {
+int FuzzerTestOneInput(const uint8_t *buf, size_t len) {
     for (int n = 0; item_type[n] != NULL; ++n) {
         const uint8_t *b = buf;
         ASN1_VALUE *o = ASN1_item_d2i(NULL, &b, len, item_type[n]);
diff --git a/fuzz/asn1parse.c b/fuzz/asn1parse.c
index 63104fb7d0..2fe420b140 100644
--- a/fuzz/asn1parse.c
+++ b/fuzz/asn1parse.c
@@ -18,7 +18,7 @@
 #include <openssl/x509v3.h>
 #include "fuzzer.h"
 
-int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len) {
+int FuzzerTestOneInput(const uint8_t *buf, size_t len) {
     static BIO *bio_out;
 
     if (bio_out == NULL)
diff --git a/fuzz/bignum.c b/fuzz/bignum.c
index 28a439e7d7..643e6e7c65 100644
--- a/fuzz/bignum.c
+++ b/fuzz/bignum.c
@@ -17,7 +17,7 @@
 #include <openssl/bn.h>
 #include "fuzzer.h"
 
-int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len) {
+int FuzzerTestOneInput(const uint8_t *buf, size_t len) {
     int success = 0;
     static BN_CTX *ctx;
     static BN_MONT_CTX *mont;
diff --git a/fuzz/bndiv.c b/fuzz/bndiv.c
index c897de99b5..521281109b 100644
--- a/fuzz/bndiv.c
+++ b/fuzz/bndiv.c
@@ -17,7 +17,7 @@
 #include <openssl/bn.h>
 #include "fuzzer.h"
 
-int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len) {
+int FuzzerTestOneInput(const uint8_t *buf, size_t len) {
     int success = 0;
     static BN_CTX *ctx;
     static BIGNUM *b1;
diff --git a/fuzz/build.info b/fuzz/build.info
index 3569418c0d..762ddf83a5 100644
--- a/fuzz/build.info
+++ b/fuzz/build.info
@@ -1,33 +1,42 @@
+{- use File::Spec::Functions;
+   our $ex_inc = $withargs{fuzzer_include} &&
+       (file_name_is_absolute($withargs{fuzzer_include}) ?
+        $withargs{fuzzer_include} : catdir(updir(), $withargs{fuzzer_include}));
+   our $ex_lib = $withargs{fuzzer_lib} &&
+       (file_name_is_absolute($withargs{fuzzer_lib}) ?
+        $withargs{fuzzer_lib} : catfile(updir(), $withargs{fuzzer_lib}));
+   ""
+-}
 PROGRAMS=asn1 asn1parse bignum bndiv cms conf ct server
 
-SOURCE[asn1]=asn1.c
-INCLUDE[asn1]=../include ../../../svn-work/Fuzzer
-DEPEND[asn1]=../libcrypto ../../../svn-work/Fuzzer/libFuzzer
+SOURCE[asn1]=asn1.c driver.c
+INCLUDE[asn1]=../include {- $ex_inc -}
+DEPEND[asn1]=../libcrypto {- $ex_lib -}
 
-SOURCE[asn1parse]=asn1parse.c
-INCLUDE[asn1parse]=../include ../../../svn-work/Fuzzer
-DEPEND[asn1parse]=../libcrypto ../../../svn-work/Fuzzer/libFuzzer
+SOURCE[asn1parse]=asn1parse.c driver.c
+INCLUDE[asn1parse]=../include {- $ex_inc -}
+DEPEND[asn1parse]=../libcrypto {- $ex_lib -}
 
-SOURCE[bignum]=bignum.c
-INCLUDE[bignum]=../include ../../../svn-work/Fuzzer
-DEPEND[bignum]=../libcrypto ../../../svn-work/Fuzzer/libFuzzer
+SOURCE[bignum]=bignum.c driver.c
+INCLUDE[bignum]=../include {- $ex_inc -}
+DEPEND[bignum]=../libcrypto {- $ex_lib -}
 
-SOURCE[bndiv]=bndiv.c
-INCLUDE[bndiv]=../include ../../../svn-work/Fuzzer
-DEPEND[bndiv]=../libcrypto ../../../svn-work/Fuzzer/libFuzzer
+SOURCE[bndiv]=bndiv.c driver.c
+INCLUDE[bndiv]=../include {- $ex_inc -}
+DEPEND[bndiv]=../libcrypto {- $ex_lib -}
 
-SOURCE[cms]=cms.c
-INCLUDE[cms]=../include ../../../svn-work/Fuzzer
-DEPEND[cms]=../libcrypto ../../../svn-work/Fuzzer/libFuzzer
+SOURCE[cms]=cms.c driver.c
+INCLUDE[cms]=../include {- $ex_inc -}
+DEPEND[cms]=../libcrypto {- $ex_lib -}
 
-SOURCE[conf]=conf.c
-INCLUDE[conf]=../include ../../../svn-work/Fuzzer
-DEPEND[conf]=../libcrypto ../../../svn-work/Fuzzer/libFuzzer
+SOURCE[conf]=conf.c driver.c
+INCLUDE[conf]=../include {- $ex_inc -}
+DEPEND[conf]=../libcrypto {- $ex_lib -}
 
-SOURCE[ct]=ct.c
-INCLUDE[ct]=../include ../../../svn-work/Fuzzer
-DEPEND[ct]=../libcrypto ../../../svn-work/Fuzzer/libFuzzer
+SOURCE[ct]=ct.c driver.c
+INCLUDE[ct]=../include {- $ex_inc -}
+DEPEND[ct]=../libcrypto {- $ex_lib -}
 
-SOURCE[server]=server.c
-INCLUDE[server]=../include ../../../svn-work/Fuzzer
-DEPEND[server]=../libcrypto ../libssl ../../../svn-work/Fuzzer/libFuzzer
+SOURCE[server]=server.c driver.c
+INCLUDE[server]=../include {- $ex_inc -}
+DEPEND[server]=../libcrypto ../libssl {- $ex_lib -}
diff --git a/fuzz/cms.c b/fuzz/cms.c
index 7b4fc3d319..71f691f61b 100644
--- a/fuzz/cms.c
+++ b/fuzz/cms.c
@@ -16,7 +16,7 @@
 #include <openssl/cms.h>
 #include "fuzzer.h"
 
-int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len) {
+int FuzzerTestOneInput(const uint8_t *buf, size_t len) {
     BIO *in = BIO_new(BIO_s_mem());
     OPENSSL_assert((size_t)BIO_write(in, buf, len) == len);
     CMS_ContentInfo *i = d2i_CMS_bio(in, NULL);
diff --git a/fuzz/conf.c b/fuzz/conf.c
index 3e3f7f184b..d10d6c7f33 100644
--- a/fuzz/conf.c
+++ b/fuzz/conf.c
@@ -15,7 +15,7 @@
 #include <openssl/conf.h>
 #include "fuzzer.h"
 
-int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len) {
+int FuzzerTestOneInput(const uint8_t *buf, size_t len) {
     CONF *conf = NCONF_new(NULL);
     BIO *in = BIO_new(BIO_s_mem());
     long eline;
diff --git a/fuzz/ct.c b/fuzz/ct.c
index 7050461142..dbb7ab4872 100644
--- a/fuzz/ct.c
+++ b/fuzz/ct.c
@@ -16,7 +16,7 @@
 #include <openssl/ct.h>
 #include "fuzzer.h"
 
-int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len) {
+int FuzzerTestOneInput(const uint8_t *buf, size_t len) {
     const uint8_t **pp = &buf;
     STACK_OF(SCT) *scts = d2i_SCT_LIST(NULL, pp, len);
     SCT_LIST_free(scts);
diff --git a/fuzz/driver.c b/fuzz/driver.c
new file mode 100644
index 0000000000..de515748ce
--- /dev/null
+++ b/fuzz/driver.c
@@ -0,0 +1,51 @@
+/*
+ * Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the OpenSSL licenses, (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * https://www.openssl.org/source/license.html
+ * or in the file LICENSE in the source distribution.
+ */
+#include <stdint.h>
+#include <unistd.h>
+#include <openssl/opensslconf.h>
+#include "fuzzer.h"
+
+#ifndef OPENSSL_NO_FUZZ_LIBFUZZER
+
+int LLVMFuzzerInitialize(int *argc, char ***argv)
+{
+    if (FuzzerInitialize)
+        return FuzzerInitialize(argc, argv);
+    return 0;
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len) {
+    return FuzzerTestOneInput(buf, len);
+}
+
+#elif !defined(OPENSSL_NO_FUZZ_AFL)
+
+#define BUF_SIZE 65536
+
+int main(int argc, char** argv)
+{
+    if (FuzzerInitialize)
+        FuzzerInitialize(&argc, &argv);
+
+    while (__AFL_LOOP(10000)) {
+        uint8_t *buf = malloc(BUF_SIZE);
+        size_t size = read(0, buf, BUF_SIZE);
+
+        FuzzerTestOneInput(buf, size);
+        free(buf);
+    }
+    return 0;
+}
+
+#else
+
+#error "Unsupported fuzzer"
+
+#endif
diff --git a/fuzz/fuzzer.h b/fuzz/fuzzer.h
index b3c3428c9b..289aee2f60 100644
--- a/fuzz/fuzzer.h
+++ b/fuzz/fuzzer.h
@@ -8,5 +8,5 @@
  * or in the file LICENSE in the source distribution.
  */
 
-int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len);
-int LLVMFuzzerInitialize(int *argc, char ***argv);
+int FuzzerTestOneInput(const uint8_t *buf, size_t len);
+__attribute__((weak)) int FuzzerInitialize(int *argc, char ***argv);
diff --git a/fuzz/server.c b/fuzz/server.c
index d3ed1adfe0..7b376c1abb 100644
--- a/fuzz/server.c
+++ b/fuzz/server.c
@@ -208,7 +208,7 @@ static void Init() {
     X509_free(cert);
   }
 
-int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len) {
+int FuzzerTestOneInput(const uint8_t *buf, size_t len) {
     if (ctx == NULL)
         Init();
     // TODO: make this work for OpenSSL. There's a PREDICT define that may do