Add fuzzing!

Reviewed-by: Emilia Käsper <emilia@openssl.org>
diff --git a/fuzz/asn1.c b/fuzz/asn1.c
new file mode 100644
index 0000000..fc129a8
--- /dev/null
+++ b/fuzz/asn1.c
@@ -0,0 +1,86 @@
+/*
+ * 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.
+ */
+
+/*
+ * Fuzz ASN.1 parsing for various data structures. Specify which on the
+ * command line:
+ *
+ * asn1 <data structure>
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <openssl/asn1.h>
+#include <openssl/asn1t.h>
+#include <openssl/ec.h>
+#include <openssl/ocsp.h>
+#include <openssl/pkcs12.h>
+#include <openssl/ts.h>
+#include <openssl/x509v3.h>
+#include "fuzzer.h"
+
+static const ASN1_ITEM *item_type;
+
+int LLVMFuzzerInitialize(int *argc, char ***argv) {
+    const char *cmd;
+    OPENSSL_assert(*argc > 1);
+
+    cmd = (*argv)[1];
+    (*argv)[1] = (*argv)[0];
+    ++*argv;
+    --*argc;
+
+    // TODO: make this work like d2i_test.c does, once its decided what the
+    // common scheme is!
+#define Y(t)  if (!strcmp(cmd, #t)) item_type = ASN1_ITEM_rptr(t)
+#define X(t)  else Y(t)
+
+    Y(ASN1_SEQUENCE);
+    X(AUTHORITY_INFO_ACCESS);
+    X(BIGNUM);
+    X(ECPARAMETERS);
+    X(ECPKPARAMETERS);
+    X(GENERAL_NAME);
+    X(GENERAL_SUBTREE);
+    X(NAME_CONSTRAINTS);
+    X(OCSP_BASICRESP);
+    X(OCSP_RESPONSE);
+    X(PKCS12);
+    X(PKCS12_AUTHSAFES);
+    X(PKCS12_SAFEBAGS);
+    X(PKCS7);
+    X(PKCS7_ATTR_SIGN);
+    X(PKCS7_ATTR_VERIFY);
+    X(PKCS7_DIGEST);
+    X(PKCS7_ENC_CONTENT);
+    X(PKCS7_ENCRYPT);
+    X(PKCS7_ENVELOPE);
+    X(PKCS7_RECIP_INFO);
+    X(PKCS7_SIGN_ENVELOPE);
+    X(PKCS7_SIGNED);
+    X(PKCS7_SIGNER_INFO);
+    X(POLICY_CONSTRAINTS);
+    X(POLICY_MAPPINGS);
+    X(SXNET);
+    //X(TS_RESP);  want to do this, but type is hidden, however d2i exists...
+    X(X509);
+    X(X509_CRL);
+    else
+        OPENSSL_assert(!"Bad type");
+
+    return 0;
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len) {
+    const uint8_t *b = buf;
+    ASN1_VALUE *o = ASN1_item_d2i(NULL, &b, len, item_type);
+    ASN1_item_free(o, item_type);
+    return 0;
+}