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