[refactor] Extract the platform-specific TrustStore instantiations and

net/cert/internal/system_trust_store.cc

+// Copyright 2017 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.
+
+#include "net/cert/internal/system_trust_store.h"
+
+#if defined(USE_NSS_CERTS)
+#include <cert.h>
+#include <pk11pub.h>
+#elif defined(OS_MACOSX) && !defined(OS_IOS)
+#include <Security/Security.h>
+#endif
+
+#include "base/memory/ptr_util.h"
+#include "net/cert/internal/trust_store_collection.h"
+#include "net/cert/internal/trust_store_in_memory.h"
+
+#if defined(USE_NSS_CERTS)
+#include "crypto/nss_util.h"
+#include "net/cert/internal/cert_issuer_source_nss.h"
+#include "net/cert/internal/trust_store_nss.h"
+#include "net/cert/scoped_nss_types.h"
+#elif defined(OS_MACOSX) && !defined(OS_IOS)
+#include "net/cert/internal/trust_store_mac.h"
+#endif
+
+namespace net {
+
+namespace {
+
+// Abstract implementation of SystemTrustStore to be used as a base class.
+// Handles the addition of additional trust anchors.
+class BaseSystemTrustStore : public SystemTrustStore {
+ public:
+  BaseSystemTrustStore() {
+    trust_store_.AddTrustStore(&additional_trust_store_);
+  }
+
+  void AddTrustAnchor(const scoped_refptr<TrustAnchor>& trust_anchor) override {
+    additional_trust_store_.AddTrustAnchor(trust_anchor);
+  }
+
+  TrustStore* GetTrustStore() override { return &trust_store_; }
+
+  CertIssuerSource* GetCertIssuerSource() override { return nullptr; }
+
+  bool IsAdditionalTrustAnchor(
+      const scoped_refptr<TrustAnchor>& trust_anchor) const override {
+    return additional_trust_store_.Contains(trust_anchor.get());
+  }
+
+ protected:
+  TrustStoreCollection trust_store_;
+  TrustStoreInMemory additional_trust_store_;
+};
+
+}  // namespace
+
+#if defined(USE_NSS_CERTS)
+namespace {
+
+class SystemTrustStoreNSS : public BaseSystemTrustStore {
+ public:
+  explicit SystemTrustStoreNSS() : trust_store_nss_(trustSSL) {
+    trust_store_.AddTrustStore(&trust_store_nss_);
+  }
+
+  CertIssuerSource* GetCertIssuerSource() override {
+    return &cert_issuer_source_nss_;
+  }
+
+  bool UsesSystemTrustStore() const override { return true; }
+
+  // IsKnownRoot returns true if the given trust anchor is a standard one (as
+  // opposed to a user-installed root)
+  bool IsKnownRoot(
+      const scoped_refptr<TrustAnchor>& trust_anchor) const override {
+    // TODO(eroman): Based on how the TrustAnchors are created by this
+    // integration, there will always be an associated certificate. However this
+    // contradicts the API for TrustAnchor that states it is optional.
+    DCHECK(trust_anchor->cert());
+
+    // TODO(eroman): The overall approach of IsKnownRoot() is inefficient -- it
+    // requires searching for the trust anchor by DER in NSS, however path
+    // building already had a handle to it.
+    SECItem der_cert;
+    der_cert.data =
+        const_cast<uint8_t*>(trust_anchor->cert()->der_cert().UnsafeData());
+    der_cert.len = trust_anchor->cert()->der_cert().Length();
+    der_cert.type = siDERCertBuffer;
+    ScopedCERTCertificate nss_cert(
+        CERT_FindCertByDERCert(CERT_GetDefaultCertDB(), &der_cert));
+    if (!nss_cert)
+      return false;
+
+    return IsKnownRoot(nss_cert.get());
+  }
+
+ private:
+  // TODO(eroman): This function was copied verbatim from
+  // cert_verify_proc_nss.cc
+  //
+  // IsKnownRoot returns true if the given certificate is one that we believe
+  // is a standard (as opposed to user-installed) root.
+  bool IsKnownRoot(CERTCertificate* root) const {
+    if (!root || !root->slot)
+      return false;
+
+    // This magic name is taken from
+    // http://bonsai.mozilla.org/cvsblame.cgi?file=mozilla/security/nss/lib/ckfw/builtins/constants.c&rev=1.13&mark=86,89#79
+    return 0 == strcmp(PK11_GetSlotName(root->slot), "NSS Builtin Objects");
+  }
+
+  TrustStoreNSS trust_store_nss_;
+  CertIssuerSourceNSS cert_issuer_source_nss_;
+};
+
+}  // namespace
+
+std::unique_ptr<SystemTrustStore> CreateSslSystemTrustStore() {
+  return base::MakeUnique<SystemTrustStoreNSS>();
+}
+
+#elif defined(OS_MACOSX) && !defined(OS_IOS)
+
+class SystemTrustStoreMac : public BaseSystemTrustStore {
+ public:
+  explicit SystemTrustStoreMac() : trust_store_mac_(kSecPolicyAppleSSL) {
+    trust_store_.AddTrustStore(&trust_store_mac_);
+  }
+
+  CertIssuerSource* GetCertIssuerSource() override {
+    // TODO(eroman): Should this return something?

[mattm, 2017/04/19 20:26:04]

yeah, I just didn't implement the CertIssuerSourceMac yet..

I'm not entirely happy with the way that works on the NSS impl (having two
separate classes that do almost the same thing).  Not sure if we should change
the interfaces, or just merge the implementations (either having both classes
use some common helper, or having a single class that implements both
interfaces.)

[eroman, 2017/04/19 21:10:41]

Agreed.

I will circle back and re-visit the TrustStore interface separately (there are
TODOs for this).

Some things to address are:
  * Need to be able to indicate distrust
  * Expose intermediates

One possible API is to have an all in-one "LookupCertAndIssuer(cert, ....)"
which returns:
  * matching trust anchors
  * matching (indeterminate trust) intermediates
  * whether |cert| itself is distrusted

This would allow for a more efficient NSS implementation, however would need
some modifications to the path builder.

Where this gets a bit uglier is for composing TrustStores. Right now
TrustStoreCollection is simple since it is clear what it means to combine
TrustAnchor results. In the case of distrustedness, we would need a policy for
precedence of trustedness/distrustedness (I am thinking a blacklisted cert takes
precedence).

Are you OK with handling this as a separate change?

[mattm, 2017/04/19 21:36:00]

Yeah, certainly do that separately.

+    return nullptr;
+  }
+
+  bool UsesSystemTrustStore() const override { return true; }
+
+  // IsKnownRoot returns true if the given trust anchor is a standard one (as
+  // opposed to a user-installed root)
+  bool IsKnownRoot(
+      const scoped_refptr<TrustAnchor>& trust_anchor) const override {
+    // TODO(eroman): Implement.
+    return false;
+  }
+
+ private:
+  TrustStoreMac trust_store_mac_;
+};
+
+std::unique_ptr<SystemTrustStore> CreateSslSystemTrustStore() {
+  return base::MakeUnique<SystemTrustStoreMac>();
+}
+#else
+
+class DummySystemTrustStore : public BaseSystemTrustStore {
+ public:
+  bool UsesSystemTrustStore() const override { return false; }
+
+  bool IsKnownRoot(
+      const scoped_refptr<TrustAnchor>& trust_anchor) const override {
+    return false;
+  }
+};
+
+std::unique_ptr<SystemTrustStore> CreateSslSystemTrustStore() {
+  return base::MakeUnique<DummySystemTrustStore>();
+}
+#endif
+
+}  // namespace net