Public Sessions - prompt the user for pageCapture requests

chrome/browser/chromeos/extensions/public_session_permission_helper.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 "chrome/browser/chromeos/extensions/public_session_permission_helper.h"
+
+#include <algorithm>
+#include <map>
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/lazy_instance.h"
+#include "base/macros.h"
+#include "base/memory/ptr_util.h"
+#include "chrome/browser/extensions/extension_install_prompt.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/web_contents.h"
+#include "extensions/common/extension.h"
+#include "extensions/common/extension_id.h"
+#include "extensions/common/permissions/manifest_permission_set.h"
+#include "extensions/common/permissions/permission_set.h"
+#include "extensions/common/url_pattern_set.h"
+
+namespace extensions {
+namespace permission_helper {
+
+namespace {
+
+std::unique_ptr<ExtensionInstallPrompt> CreateExtensionInstallPrompt(
+    content::WebContents* web_contents,
+    PromptFactory* prompt_factory) {
+  if (prompt_factory) {

[Andrew T Wilson (Slow), 2017/02/10 17:17:21]

This is OK, but the other way to do this is to have the check for a null
callback happen in HandlePermissionRequest, and store a reference to this method
as a callback instead. That way HandlePermissionRequestImpl() can just invoke
the callback with no further checks.

[Ivan Šandrk, 2017/02/10 18:46:25]

Done.

+    return prompt_factory->Run();
+  }
+  return base::MakeUnique<ExtensionInstallPrompt>(web_contents);
+}
+
+// This class is the internal implementation of HandlePermissionRequest(). It
+// contains the actual prompt showing and resolving logic, and it caches the
+// user choices.
+class PublicSessionPermissionHelper {
+ public:
+  PublicSessionPermissionHelper();
+  PublicSessionPermissionHelper(PublicSessionPermissionHelper&& other);
+  ~PublicSessionPermissionHelper();
+
+  void HandlePermissionRequestImpl(const Extension& extension,
+                                   const PermissionIDSet& requested_permissions,
+                                   content::WebContents* web_contents,
+                                   const RequestResolvedCallback& callback,
+                                   PromptFactory* prompt_factory);
+
+ private:
+  void ResolvePermissionPrompt(
+      const ExtensionInstallPrompt* prompt,
+      const PermissionIDSet& unprompted_permissions,
+      ExtensionInstallPrompt::Result prompt_result);
+
+  PermissionIDSet FilterAllowedPermissions(
+      const PermissionIDSet& permissions);
+
+  struct RequestCallback {
+    RequestCallback(const RequestResolvedCallback& callback,
+                    const PermissionIDSet& permission_list);
+    RequestCallback(const RequestCallback& other);
+    ~RequestCallback();
+    RequestResolvedCallback callback;
+    PermissionIDSet permission_list;
+  };
+  using RequestCallbackList = std::vector<RequestCallback>;
+
+  std::set<std::unique_ptr<ExtensionInstallPrompt>> prompts_;
+  PermissionIDSet prompted_permission_set_;
+  PermissionIDSet allowed_permission_set_;
+  PermissionIDSet denied_permission_set_;
+  RequestCallbackList callbacks_;
+
+  DISALLOW_COPY_AND_ASSIGN(PublicSessionPermissionHelper);
+};
+
+PublicSessionPermissionHelper::PublicSessionPermissionHelper() {}
+
+PublicSessionPermissionHelper::PublicSessionPermissionHelper(
+    PublicSessionPermissionHelper&& other) = default;
+
+PublicSessionPermissionHelper::~PublicSessionPermissionHelper() {}
+
+void PublicSessionPermissionHelper::HandlePermissionRequestImpl(
+    const Extension& extension,
+    const PermissionIDSet& requested_permissions,
+    content::WebContents* web_contents,
+    const RequestResolvedCallback& callback,
+    PromptFactory* prompt_factory) {
+  CHECK(web_contents);
+
+  PermissionIDSet unresolved_permissions = PermissionIDSet::Difference(
+      requested_permissions, allowed_permission_set_);
+  unresolved_permissions = PermissionIDSet::Difference(
+      unresolved_permissions, denied_permission_set_);
+  if (unresolved_permissions.empty()) {
+    // All requested permissions are already resolved.
+    callback.Run(FilterAllowedPermissions(requested_permissions));
+    return;
+  }
+
+  // Since not all permissions are resolved yet, queue the callback to be called
+  // when all of them are resolved.
+  callbacks_.push_back(RequestCallback(callback, requested_permissions));
+
+  PermissionIDSet unprompted_permissions = PermissionIDSet::Difference(
+      unresolved_permissions, prompted_permission_set_);
+  if (unprompted_permissions.empty()) {
+    // Some permissions aren't resolved yet, but they are currently being
+    // prompted for, so no need to show a prompt.
+    return;
+  }
+
+  // Some permissions need prompting, setup the prompt and show it.
+  APIPermissionSet new_apis;
+  for (const auto& permission : unprompted_permissions) {
+    prompted_permission_set_.insert(permission.id());
+    new_apis.insert(permission.id());
+  }
+  auto permission_set = base::MakeUnique<PermissionSet>(
+      new_apis, ManifestPermissionSet(), URLPatternSet(), URLPatternSet());
+  auto prompt = CreateExtensionInstallPrompt(web_contents, prompt_factory);
+  // This Unretained is safe because the lifetime of this object is until
+  // process exit.
+  prompt->ShowDialog(
+      base::Bind(&PublicSessionPermissionHelper::ResolvePermissionPrompt,
+                 base::Unretained(this), prompt.get(),
+                 std::move(unprompted_permissions)),
+      &extension,
+      nullptr,  // Use the extension icon.
+      base::MakeUnique<ExtensionInstallPrompt::Prompt>(
+          ExtensionInstallPrompt::PERMISSIONS_PROMPT),
+      std::move(permission_set),
+      ExtensionInstallPrompt::GetDefaultShowDialogCallback());
+  prompts_.insert(std::move(prompt));
+}
+
+void PublicSessionPermissionHelper::ResolvePermissionPrompt(
+    const ExtensionInstallPrompt* prompt,
+    const PermissionIDSet& unprompted_permissions,
+    ExtensionInstallPrompt::Result prompt_result) {
+  const bool allowed =
+      prompt_result == ExtensionInstallPrompt::Result::ACCEPTED;
+  for (const auto& permission : unprompted_permissions) {
+    prompted_permission_set_.erase(permission.id());
+    if (allowed)

[Devlin, 2017/02/10 19:54:46]

Optional: for fanciness,
PermissionIdSet& add_to_set =
    prompt_result == ExtensionInstallPrompt::Result::ACCEPTED ?
        allowed_permission_set_ : denied_permission_set_;
for (const auto& permission : unprompted_permissions) {
  prompted_permission_set_.erase(permission.id());
  add_to_set.insert(permission.id());
}

I think it's marginally simpler, but mostly just a matter of preference, so up
to you.

[Ivan Šandrk, 2017/02/13 13:18:20]

Seems nice. Done.

+      allowed_permission_set_.insert(permission.id());
+    else
+      denied_permission_set_.insert(permission.id());
+  }
+
+  // Here a list of callbacks to be invoked is created first from callbacks_,
+  // then those callbacks are invoked later because a callback can change
+  // callbacks_ while we're traversing them.
+  RequestCallbackList callbacks_to_invoke;
+  for (auto callback = callbacks_.begin(); callback != callbacks_.end(); ) {
+    if (prompted_permission_set_.ContainsAnyID(callback->permission_list)) {
+      // The request is still waiting on other permissions to be resolved - wait
+      // until all of them are resolved before calling the callback.
+      callback++;
+      continue;
+    }
+    callbacks_to_invoke.push_back(std::move(*callback));
+    callback = callbacks_.erase(callback);
+  }
+  for (auto callback = callbacks_to_invoke.begin();
+       callback != callbacks_to_invoke.end(); callback++) {
+    callback->callback.Run(FilterAllowedPermissions(callback->permission_list));
+  }
+
+  // Dispose of the prompt as it's not needed anymore.
+  auto iter = std::find_if(
+      prompts_.begin(), prompts_.end(),
+      [prompt](const std::unique_ptr<ExtensionInstallPrompt>& check) {
+        return check.get() == prompt;
+      });
+  DCHECK(iter != prompts_.end());
+  prompts_.erase(iter);
+}
+
+PermissionIDSet PublicSessionPermissionHelper::FilterAllowedPermissions(
+    const PermissionIDSet& permissions) {
+  PermissionIDSet allowed_permissions;
+  for (auto iter = permissions.begin(); iter != permissions.end(); iter++) {
+    if (allowed_permission_set_.ContainsID(*iter)) {
+      allowed_permissions.insert(iter->id());
+    }
+  }
+  return allowed_permissions;
+}
+
+PublicSessionPermissionHelper::RequestCallback::RequestCallback(
+    const RequestResolvedCallback& callback,
+    const PermissionIDSet& permission_list)
+    : callback(callback),
+      permission_list(permission_list) {}
+
+PublicSessionPermissionHelper::RequestCallback::RequestCallback(
+    const RequestCallback& other) = default;
+
+PublicSessionPermissionHelper::RequestCallback::~RequestCallback() {}
+
+base::LazyInstance<std::map<ExtensionId, PublicSessionPermissionHelper>>::Leaky
+    g_helpers = LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
+
+void HandlePermissionRequest(const Extension& extension,
+                             const PermissionIDSet& requested_permissions,
+                             content::WebContents* web_contents,
+                             const RequestResolvedCallback& callback,
+                             PromptFactory* prompt_factory) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  return g_helpers.Get()[extension.id()].HandlePermissionRequestImpl(
+      extension, requested_permissions, web_contents, callback, prompt_factory);
+}
+
+void ResetPermissionsForTesting() {
+  g_helpers = LAZY_INSTANCE_INITIALIZER;
+}
+
+}  // namespace permission_helper
+}  // namespace extensions