Add a do-nothing CTVerifier to //net

net/cert/do_nothing_ct_verifier.h

Index: net/cert/do_nothing_ct_verifier.h
diff --git a/net/cert/do_nothing_ct_verifier.h b/net/cert/do_nothing_ct_verifier.h
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+++ b/net/cert/do_nothing_ct_verifier.h
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+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NET_CERT_DO_NOTHING_CT_VERIFIER_H_
+#define NET_CERT_DO_NOTHING_CT_VERIFIER_H_
+
+#include "base/macros.h"
+#include "net/base/net_export.h"
+#include "net/cert/ct_verifier.h"
+
+namespace net {
+
+// An implementation of CTVerifier that does not validate SCTs.
+//
+// SECURITY NOTE:
+// As Certificate Transparency is an essential part in safeguarding TLS
+// connections, disabling Certificate Transparency enforcement is a decision
+// that should not be taken lightly, and it should be made an explicit
+// decision rather than a potentially accidental decision (such as allowing
+// for a nullptr instance). By checking Certificate Transparency information,
+// typically via a net::MultiLogCTVerifier, and enforcing policies related
+// to Certificate Transparency provided by a net::CTPolicyEnforcer, developers
+// can help protect their users by ensuring that misissued TLS certificates
+// are detected.
+//
+// However, not every consumer of TLS certificates is using the Web PKI. For
+// example, they may be using connections authenticated out of band, or may
+// be using private or local PKIs for which Certificate Transparency is not
+// relevant. Alternatively, much like how a robust and secure TLS client
+// requires a regularly updated root certificate store, a robust and secure
+// Certificate Transparency client requires regular updates. However, since
+// some clients may not support regular updates, it may be intentional to
+// disable Certificate Transparency and choose a less-secure default
+// behavior.
+//
+// Consumers of this class should generally try to get a security or design
+// to discuss the type of net::X509Certificates they will be validating,
+// and determine whether or not Certificate Transparency is right for the
+// particular use case.
+//
+// Because of the complex nuances related to security tradeoffs, it is
+// expected that classes which expect a CTVerifier will require one to be
+// supplied, forcing the caller to make an intentional and explicit decision
+// about the appropriate security policy, rather than leaving it ambiguous,
+// such as via a nullptr. This class is intended to indicate an intentional
+// consideration of CT, and a decision to not support it.
+class NET_EXPORT DoNothingCTVerifier : public CTVerifier {
+ public:
+  DoNothingCTVerifier();
+  ~DoNothingCTVerifier() override;
+
+  int Verify(X509Certificate* cert,
+             const std::string& stapled_ocsp_response,
+             const std::string& sct_list_from_tls_extension,
+             SignedCertificateTimestampAndStatusList* output_scts,
+             const NetLogWithSource& net_log) override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DoNothingCTVerifier);
+};
+
+}  // namespace net
+
+#endif  // NET_CERT_DO_NOTHING_CT_VERIFIER_H_