[FeaturePolicy] Initial implementation of Feature Policy

third_party/WebKit/Source/platform/feature_policy/FeaturePolicy.h

+// 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 FeaturePolicy_h
+#define FeaturePolicy_h
+
+#include "platform/PlatformExport.h"
+#include "platform/weborigin/SecurityOrigin.h"
+#include "wtf/RefPtr.h"
+#include "wtf/Vector.h"
+#include "wtf/text/WTFString.h"
+
+#include <memory>
+
+namespace blink {
+
+// Feature Policy is a mechanism for controlling the availability of web
+// platform features in a frame, including all embedded frames. It can be used
+// to remove features, automatically refuse API permission requests, or modify
+// the behaviour of features. (The specific changes which are made depend on the
+// feature; see the specification for details).
+//
+// Policies can be defined in the HTTP header stream, with the |Feature-Policy|
+// HTTP header, or can be set by |enable| and |disable| attributes on the iframe
+// element which embeds the document.
+//
+// See https://wicg.github.io/FeaturePolicy/
+//
+// Key concepts:
+//
+// Features
+// --------
+// Features which can be controlled by policy are defined as instances of the
+// FeaturePoliicy::Feature struct. The features are referenced by pointer, so
+// only a single instance of each feature should be defined. The features which
+// are declared in the feature policy specification are all defined in
+// |FeaturePolicy.cpp|.
+//
+// Whitelists
+// ----------
+// Policies are defined as a mapping of feaure names to whitelists. Whitelists
+// are collections of origins, although two special terms can be used when
+// declaring them:
+//   "self" refers to the orgin of the frame which is declaring the policy.
+//   "*" refers to all origins; any origin will match a whitelist which contains
+//     it.
+//
+// Defaults
+// --------
+// Each defined feature has a default policy, which determines whether the
+// feature is available when no policy has been declared, ans determines how the

[raymes, 2016/10/24 06:51:45]

nit: and

+// feature is inherited across origin boundaries.
+//
+// If the default policy  is in effect for a frame, then it controls how the

[raymes, 2016/10/24 06:51:45]

nit: double space

+// feature is inherited by any cross-origin iframes embedded by the frame. (See
+// the comments below in FeaturePolicy::DefaultPolicy for specifics)
+//
+// Policy Inheritance
+// ------------------
+// Policies in effect for a frame are inherited by any child frames it embeds.
+// Unless another policy is declared in the child, all same-origin children will
+// receive the same set of enables features as the parent frame. Whether or not
+// features are inherited by cross-origin iframes without an explicit policy is
+// determined by the feature's default policy. (Again, see the comments in
+// FeaturePolicy::DefaultPolicy for details)

[raymes, 2016/10/24 06:51:45]

I find this section a bit confusing, because inheritance makes me think that the
whitelists are actually inherited. Perhaps the key points are:
-Frames can control what features are enabled in themselves or in child frames
-If a feature is disabled in a child frame, it cannot be re-enabled by that
child frame or any of its descendants.
-If no policy is explicitly specified for a frame, the default policy is used
(although this might be redundant with the above).

+
+class PLATFORM_EXPORT FeaturePolicy final {
+ public:
+  // Represents a collection of origins which make up a whitelist in a feature
+  // policy. This collection may be set to match every origin (corresponding to
+  // the "*" syntax in the policy string, in which case the contains() method
+  // will always return true.
+  class Whitelist final {
+   public:
+    Whitelist();
+
+    // Adds a single origin to the whitelist.
+    void add(RefPtr<SecurityOrigin>);
+
+    // Adds all origins to the whitelist.
+    void addAll();
+
+    // Returns true if the given origin has been added to the whitelist.
+    bool contains(const SecurityOrigin&) const;
+    String toString();
+
+   private:
+    bool m_matchesAllOrigins;
+    Vector<RefPtr<SecurityOrigin>> m_origins;
+  };
+
+  // The FeaturePolicy::FeatureDefault enum defines the default enable state for
+  // a feature when neither it nor any parent frame have declared an explicit
+  // policy. The three possibilities map directly to Feature Policy Whitelist
+  // semantics.
+  enum class FeatureDefault {
+    // Equivalent to []. If this default policy is in effect for a frame, then
+    // the feature will not be enabled for that frame or any of its children.
+    DisableForAll,
+
+    // Equivalent to ["self"]. If this default policy is in effect for a frame,
+    // then the feature will be enabled for that frame, and any same-origin
+    // child frames, but not for any cross-origin child frames.
+    EnableForSelf,
+
+    // Equivalent to ["*"]. If in effect for a frame, then the feature is
+    // enabled for that frame and all of its children.
+    EnableForAll
+  };
+
+  // The FeaturePolicy::Feature struct is used to define all features under
+  // control of Feature Policy. There should only be one instance of this struct
+  // for any given feature (declared below).
+  struct Feature {
+    // The name of the feature, as it should appear in a policy string
+    const char* featureName;
+
+    // Controls whether the feature should be available in the platform by
+    // default, in the absence of any declared policy.
+    FeatureDefault defaultPolicy;
+  };
+
+  using FeatureList = const Vector<const FeaturePolicy::Feature*>;
+
+  static FeaturePolicy* createFromParentPolicy(const FeaturePolicy* parent,
+                                               RefPtr<SecurityOrigin>);
+
+  // Sets the declared policy from the Feature-Policy HTTP header. If the header
+  // cannot be parsed, errors will be appended to the |messages| vector.
+  void setHeaderPolicy(const String&, Vector<String>& messages);
+
+  // Returns whether or not the given feature is enabled by this policy.
+  bool isFeatureEnabledForOrigin(const Feature*, const SecurityOrigin&) const;
+
+  // Returns whether or not the given feature is enabled for the frame that owns
+  // the policy.
+  bool isFeatureEnabled(const Feature*) const;
+
+  // Returns the list of features which can be controlled by Feature Policy.
+  static FeatureList& getDefaultFeatureList();
+
+  String toString();
+
+ private:
+  friend class FeaturePolicyTest;
+
+  FeaturePolicy(RefPtr<SecurityOrigin>, FeatureList& features);
+
+  static FeaturePolicy* createFromParentPolicy(const FeaturePolicy* parent,
+                                               RefPtr<SecurityOrigin>,
+                                               FeatureList& features);
+
+  // Parses a policy string into a set of whitelists for features.
+  HashMap<const Feature*, std::unique_ptr<Whitelist>> parse(const String&);
+
+  RefPtr<SecurityOrigin> m_origin;
+
+  // Records whether or not each feature was enabled for this frame by its
+  // parent frame.
+  // TODO(iclelland): Generate, instead of this map, a set of bool flags, one
+  // for each feature, as all features are supposed to be represented here.
+  HashMap<const Feature*, bool> m_inheritedFeatures;
+
+  // Map of feature names to declared whitelists. Any feature which is missing
+  // from this map should use the inherited policy.
+  HashMap<const Feature*, std::unique_ptr<Whitelist>> m_headerWhitelists;
+
+  // Contains the set of all features which can be controlled by this policy.
+  FeatureList& m_features;
+
+  DISALLOW_COPY_AND_ASSIGN(FeaturePolicy);
+};
+
+// Declarations for all features currently under control of the Feature Policy
+// mechanism should be placed here.
+extern const PLATFORM_EXPORT FeaturePolicy::Feature kDocumentCookie;
+extern const PLATFORM_EXPORT FeaturePolicy::Feature kDocumentDomain;
+extern const PLATFORM_EXPORT FeaturePolicy::Feature kDocumentWrite;
+extern const PLATFORM_EXPORT FeaturePolicy::Feature kGeolocationFeature;
+extern const PLATFORM_EXPORT FeaturePolicy::Feature kMidiFeature;
+extern const PLATFORM_EXPORT FeaturePolicy::Feature kNotificationsFeature;
+extern const PLATFORM_EXPORT FeaturePolicy::Feature kPaymentFeature;
+extern const PLATFORM_EXPORT FeaturePolicy::Feature kPushFeature;
+extern const PLATFORM_EXPORT FeaturePolicy::Feature kSyncScript;
+extern const PLATFORM_EXPORT FeaturePolicy::Feature kSyncXHR;
+extern const PLATFORM_EXPORT FeaturePolicy::Feature kUsermedia;
+extern const PLATFORM_EXPORT FeaturePolicy::Feature kVibrateFeature;
+extern const PLATFORM_EXPORT FeaturePolicy::Feature kWebRTC;
+
+}  // namespace blink
+
+#endif  // FeaturePolicy_h