extensions/browser/management_policy.h

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef EXTENSIONS_BROWSER_MANAGEMENT_POLICY_H_
   6 #define EXTENSIONS_BROWSER_MANAGEMENT_POLICY_H_
   7
   8 #include <set>
   9 #include <string>
  10 #include <vector>
  11
  12 #include "base/basictypes.h"
  13 #include "extensions/common/extension.h"
  14
  15 namespace extensions {
  16
  17 // This class registers providers that want to prohibit certain actions from
  18 // being applied to extensions. It must be called, via the ExtensionService,
  19 // before allowing a user or a user-level mechanism to perform the respective
  20 // action. (That is, installing or otherwise modifying an extension in order
  21 // to conform to enterprise administrator policy must be exempted from these
  22 // checks.)
  23 //
  24 // This "policy" and its providers should not be confused with administrator
  25 // policy, although admin policy is one of the sources ("Providers") of
  26 // restrictions registered with and exposed by the ManagementPolicy.
  27 class ManagementPolicy {
  28  public:
  29   // Each mechanism that wishes to limit users' ability to control extensions,
  30   // whether one individual extension or the whole system, should implement
  31   // the methods of this Provider interface that it needs. In each case, if the
  32   // provider does not need to control a certain action, that method does not
  33   // need to be implemented.
  34   //
  35   // It is not guaranteed that a particular Provider's methods will be called
  36   // each time a user tries to perform one of the controlled actions (the list
  37   // of providers is short-circuited as soon as a decision is possible), so
  38   // implementations of these methods must have no side effects.
  39   //
  40   // For all of the Provider methods below, if |error| is not NULL and the
  41   // method imposes a restriction on the desired action, |error| may be set
  42   // to an applicable error message, but this is not required.
  43   class Provider {
  44    public:
  45     Provider() {}
  46     virtual ~Provider() {}
  47
  48     // A human-readable name for this provider, for use in debug messages.
  49     // Implementers should return an empty string in non-debug builds, to save
  50     // executable size.
  51     virtual std::string GetDebugPolicyProviderName() const = 0;
  52
  53     // Providers should return false if a user may not install the |extension|,
  54     // or load or run it if it has already been installed.
  55     virtual bool UserMayLoad(const Extension* extension,
  56                              base::string16* error) const;
  57
  58     // Providers should return false if a user may not enable, disable, or
  59     // uninstall the |extension|, or change its usage options (incognito
  60     // permission, file access, etc.).
  61     virtual bool UserMayModifySettings(const Extension* extension,
  62                                        base::string16* error) const;
  63
  64     // Providers should return true if the |extension| must always remain
  65     // enabled. This is distinct from UserMayModifySettings() in that the latter
  66     // also prohibits enabling the extension if it is currently disabled.
  67     // Providers implementing this method should also implement the others
  68     // above, if they wish to completely lock in an extension.
  69     virtual bool MustRemainEnabled(const Extension* extension,
  70                                    base::string16* error) const;
  71
  72     // Similar to MustRemainEnabled, but for whether an extension must remain
  73     // disabled, and returns an error and/or reason if the caller needs it.
  74     virtual bool MustRemainDisabled(const Extension* extension,
  75                                     Extension::DisableReason* reason,
  76                                     base::string16* error) const;
  77
  78     // Similar to MustRemainEnabled, but for whether an extension must remain
  79     // installed, and returns an error and/or reason if the caller needs it.
  80     virtual bool MustRemainInstalled(const Extension* extension,
  81                                      base::string16* error) const;
  82
  83    private:
  84     DISALLOW_COPY_AND_ASSIGN(Provider);
  85   };
  86
  87   ManagementPolicy();
  88   ~ManagementPolicy();
  89
  90   // Registers or unregisters a provider, causing it to be added to or removed
  91   // from the list of providers queried. Ownership of the provider remains with
  92   // the caller. Providers do not need to be unregistered on shutdown.
  93   void RegisterProvider(Provider* provider);
  94   void UnregisterProvider(Provider* provider);
  95
  96   // Like RegisterProvider(), but registers multiple providers instead.
  97   void RegisterProviders(std::vector<Provider*> providers);
  98
  99   // Returns true if the user is permitted to install, load, and run the given
 100   // extension. If not, |error| may be set to an appropriate message.
 101   bool UserMayLoad(const Extension* extension, base::string16* error) const;
 102
 103   // Returns true if the user is permitted to enable, disable, or uninstall the
 104   // given extension, or change the extension's usage options (incognito mode,
 105   // file access, etc.). If not, |error| may be set to an appropriate message.
 106   bool UserMayModifySettings(const Extension* extension,
 107                              base::string16* error) const;
 108
 109   // Returns true if the extension must remain enabled at all times (e.g. a
 110   // compoment extension). In that case, |error| may be set to an appropriate
 111   // message.
 112   bool MustRemainEnabled(const Extension* extension,
 113                          base::string16* error) const;
 114
 115   // Returns true immediately if any registered provider's MustRemainDisabled
 116   // function returns true.
 117   bool MustRemainDisabled(const Extension* extension,
 118                           Extension::DisableReason* reason,
 119                           base::string16* error) const;
 120
 121   // Returns true immediately if any registered provider's MustRemainInstalled
 122   // function returns true.
 123   bool MustRemainInstalled(const Extension* extension,
 124                            base::string16* error) const;
 125
 126   // For use in testing.
 127   void UnregisterAllProviders();
 128   int GetNumProviders() const;
 129
 130  private:
 131   // This is a pointer to a function in the Provider interface, used in
 132   // ApplyToProviderList.
 133   typedef bool (Provider::*ProviderFunction)(const Extension*,
 134                                              base::string16*) const;
 135
 136   typedef std::set<Provider*> ProviderList;
 137
 138   // This is a helper to apply a method in the Provider interface to each of
 139   // the Provider objects in |providers_|. The return value of this function
 140   // will be |normal_result|, unless any of the Provider calls to |function|
 141   // return !normal_result, in which case this function will then early-return
 142   // !normal_result.
 143   bool ApplyToProviderList(ProviderFunction function,
 144                            const char* debug_operation_name,
 145                            bool normal_result,
 146                            const Extension* extension,
 147                            base::string16* error) const;
 148
 149   ProviderList providers_;
 150
 151   DISALLOW_COPY_AND_ASSIGN(ManagementPolicy);
 152 };
 153
 154 }  // namespace extensions
 155
 156 #endif  // EXTENSIONS_BROWSER_MANAGEMENT_POLICY_H_