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ios/web/web_state/js/crw_js_window_id_manager.mm

Index: ios/web/web_state/js/crw_js_window_id_manager.mm
diff --git a/ios/web/web_state/js/crw_js_window_id_manager.mm b/ios/web/web_state/js/crw_js_window_id_manager.mm
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+// Copyright 2014 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.
+
+#import "ios/web/web_state/js/crw_js_window_id_manager.h"
+
+#import "base/mac/scoped_nsobject.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/sys_string_conversions.h"
+#include "crypto/random.h"
+
+namespace {
+// Number of random bytes in unique key for window ID. The length of the
+// window ID will be twice this number, as it is hexadecimal encoded.
+const NSInteger kUniqueKeyLength = 16;
+}  // namespace
+
+@interface CRWJSWindowIdManager () {
+  base::scoped_nsobject<NSString> _windowId;
+}
+
+// Returns a string of randomized ASCII characters.
+- (NSString*)generateUniqueKey;
+
+@end
+
+@implementation CRWJSWindowIdManager
+
+- (id)initWithReceiver:(CRWJSInjectionReceiver*)receiver {
+  self = [super initWithReceiver:receiver];
+  if (self) {
+    _windowId.reset([[self generateUniqueKey] retain]);
+  }
+  return self;
+}
+
+- (NSString*)windowId {
+  return _windowId;
+}
+
+- (void)setWindowId:(NSString*)value {
+  _windowId.reset([value copy]);
+}
+
+#pragma mark ProtectedMethods
+
+- (NSString*)scriptPath {
+  return @"window_id";
+}
+
+- (NSString*)presenceBeacon {
+  return @"__gCrWeb.windowIdObject";
+}
+
+// It is important to recreate the injection content on every injection, because
+// it cotains the randomly-generated page ID used for security checks.
+- (NSString*)injectionContent {
+  _windowId.reset([[self generateUniqueKey] retain]);
+  NSString* script = [super injectionContent];
+  return [script stringByReplacingOccurrencesOfString:@"$(WINDOW_ID)"
+                                           withString:_windowId];
+}
+
+#pragma mark - Private
+
+- (NSString*)generateUniqueKey {
+  char randomBytes[kUniqueKeyLength];
+  crypto::RandBytes(randomBytes, kUniqueKeyLength);
+  return
+      base::SysUTF8ToNSString(base::HexEncode(randomBytes, kUniqueKeyLength));
+}
+
+@end