app/src/main/java/com/stoutner/privacybrowser/dialogs/SslCertificateErrorDialog.java

   1 /*
   2  * Copyright © 2016-2020 Soren Stoutner <soren@stoutner.com>.
   3  *
   4  * This file is part of Privacy Browser <https://www.stoutner.com/privacy-browser>.
   5  *
   6  * Privacy Browser is free software: you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation, either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * Privacy Browser is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with Privacy Browser.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 package com.stoutner.privacybrowser.dialogs;
  21
  22 import android.annotation.SuppressLint;
  23 import android.app.Activity;
  24 import android.app.Dialog;
  25 import android.content.DialogInterface;
  26 import android.content.SharedPreferences;
  27 import android.content.res.Configuration;
  28 import android.net.Uri;
  29 import android.net.http.SslCertificate;
  30 import android.net.http.SslError;
  31 import android.os.AsyncTask;
  32 import android.os.Bundle;
  33 import android.preference.PreferenceManager;
  34 import android.text.SpannableStringBuilder;
  35 import android.text.Spanned;
  36 import android.text.style.ForegroundColorSpan;
  37 import android.view.LayoutInflater;
  38 import android.view.View;
  39 import android.view.WindowManager;
  40 import android.webkit.SslErrorHandler;
  41 import android.widget.TextView;
  42
  43 import androidx.annotation.NonNull;
  44 import androidx.appcompat.app.AlertDialog;
  45 import androidx.fragment.app.DialogFragment;
  46
  47 import com.stoutner.privacybrowser.R;
  48 import com.stoutner.privacybrowser.activities.MainWebViewActivity;
  49 import com.stoutner.privacybrowser.fragments.WebViewTabFragment;
  50 import com.stoutner.privacybrowser.views.NestedScrollWebView;
  51
  52 import java.lang.ref.WeakReference;
  53 import java.net.InetAddress;
  54 import java.net.UnknownHostException;
  55 import java.text.DateFormat;
  56 import java.util.Date;
  57
  58 public class SslCertificateErrorDialog extends DialogFragment {
  59     public static SslCertificateErrorDialog displayDialog(SslError error, long webViewFragmentId) {
  60         // Get the various components of the SSL error message.
  61         int primaryErrorIntForBundle = error.getPrimaryError();
  62         String urlWithErrorForBundle = error.getUrl();
  63         SslCertificate sslCertificate = error.getCertificate();
  64         String issuedToCNameForBundle = sslCertificate.getIssuedTo().getCName();
  65         String issuedToONameForBundle = sslCertificate.getIssuedTo().getOName();
  66         String issuedToUNameForBundle = sslCertificate.getIssuedTo().getUName();
  67         String issuedByCNameForBundle = sslCertificate.getIssuedBy().getCName();
  68         String issuedByONameForBundle = sslCertificate.getIssuedBy().getOName();
  69         String issuedByUNameForBundle = sslCertificate.getIssuedBy().getUName();
  70         Date startDateForBundle = sslCertificate.getValidNotBeforeDate();
  71         Date endDateForBundle = sslCertificate.getValidNotAfterDate();
  72
  73         // Create an arguments bundle.
  74         Bundle argumentsBundle = new Bundle();
  75
  76         // Store the SSL error message components in a `Bundle`.
  77         argumentsBundle.putInt("primary_error_int", primaryErrorIntForBundle);
  78         argumentsBundle.putString("url_with_error", urlWithErrorForBundle);
  79         argumentsBundle.putString("issued_to_cname", issuedToCNameForBundle);
  80         argumentsBundle.putString("issued_to_oname", issuedToONameForBundle);
  81         argumentsBundle.putString("issued_to_uname", issuedToUNameForBundle);
  82         argumentsBundle.putString("issued_by_cname", issuedByCNameForBundle);
  83         argumentsBundle.putString("issued_by_oname", issuedByONameForBundle);
  84         argumentsBundle.putString("issued_by_uname", issuedByUNameForBundle);
  85         argumentsBundle.putString("start_date", DateFormat.getDateTimeInstance(DateFormat.MEDIUM, DateFormat.LONG).format(startDateForBundle));
  86         argumentsBundle.putString("end_date", DateFormat.getDateTimeInstance(DateFormat.MEDIUM, DateFormat.LONG).format(endDateForBundle));
  87         argumentsBundle.putLong("webview_fragment_id", webViewFragmentId);
  88
  89         // Create a new instance of the SSL certificate error dialog.
  90         SslCertificateErrorDialog thisSslCertificateErrorDialog = new SslCertificateErrorDialog();
  91
  92         // Add the arguments bundle to the new dialog.
  93         thisSslCertificateErrorDialog.setArguments(argumentsBundle);
  94
  95         // Return the new dialog.
  96         return thisSslCertificateErrorDialog;
  97     }
  98
  99     // `@SuppressLing("InflateParams")` removes the warning about using `null` as the parent view group when inflating the `AlertDialog`.
 100     @SuppressLint("InflateParams")
 101     @Override
 102     @NonNull
 103     public Dialog onCreateDialog(Bundle savedInstanceState) {
 104         // Get a handle for the arguments.
 105         Bundle arguments = getArguments();
 106
 107         // Remove the incorrect lint warning that the arguments might be null.
 108         assert arguments != null;
 109
 110         // Get the variables from the bundle.
 111         int primaryErrorInt = arguments.getInt("primary_error_int");
 112         String urlWithErrors = arguments.getString("url_with_error");
 113         String issuedToCName = arguments.getString("issued_to_cname");
 114         String issuedToOName = arguments.getString("issued_to_oname");
 115         String issuedToUName = arguments.getString("issued_to_uname");
 116         String issuedByCName = arguments.getString("issued_by_cname");
 117         String issuedByOName = arguments.getString("issued_by_oname");
 118         String issuedByUName = arguments.getString("issued_by_uname");
 119         String startDate = arguments.getString("start_date");
 120         String endDate = arguments.getString("end_date");
 121         long webViewFragmentId = arguments.getLong("webview_fragment_id");
 122
 123         // Get the current position of this WebView fragment.
 124         int webViewPosition = MainWebViewActivity.webViewPagerAdapter.getPositionForId(webViewFragmentId);
 125
 126         // Get the WebView tab fragment.
 127         WebViewTabFragment webViewTabFragment = MainWebViewActivity.webViewPagerAdapter.getPageFragment(webViewPosition);
 128
 129         // Get the fragment view.
 130         View fragmentView = webViewTabFragment.getView();
 131
 132         // Remove the incorrect lint warning below that the fragment view might be null.
 133         assert fragmentView != null;
 134
 135         // Get a handle for the current WebView.
 136         NestedScrollWebView nestedScrollWebView = fragmentView.findViewById(R.id.nestedscroll_webview);
 137
 138         // Get a handle for the SSL error handler.
 139         SslErrorHandler sslErrorHandler = nestedScrollWebView.getSslErrorHandler();
 140
 141         // Get the activity's layout inflater.
 142         LayoutInflater layoutInflater = requireActivity().getLayoutInflater();
 143
 144         // Use an alert dialog builder to create the alert dialog.
 145         AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(requireContext(), R.style.PrivacyBrowserAlertDialog);
 146
 147         // Get the current theme status.
 148         int currentThemeStatus = getResources().getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK;
 149
 150         // Set the icon according to the theme.
 151         if (currentThemeStatus == Configuration.UI_MODE_NIGHT_YES) {
 152             dialogBuilder.setIcon(R.drawable.ssl_certificate_enabled_night);
 153         } else {
 154             dialogBuilder.setIcon(R.drawable.ssl_certificate_enabled_day);
 155         }
 156
 157         // Set the title.
 158         dialogBuilder.setTitle(R.string.ssl_certificate_error);
 159
 160         // Set the view.  The parent view is `null` because it will be assigned by `AlertDialog`.
 161         dialogBuilder.setView(layoutInflater.inflate(R.layout.ssl_certificate_error, null));
 162
 163         // Set a listener on the cancel button.
 164         dialogBuilder.setNegativeButton(R.string.cancel, (DialogInterface dialog, int which) -> {
 165             // Check to make sure the SSL error handler is not null.  This might happen if multiple dialogs are displayed at once.
 166             if (sslErrorHandler != null) {
 167                 // Cancel the request.
 168                 sslErrorHandler.cancel();
 169
 170                 // Reset the SSL error handler.
 171                 nestedScrollWebView.resetSslErrorHandler();
 172             }
 173         });
 174
 175         // Set a listener on the proceed button.
 176         dialogBuilder.setPositiveButton(R.string.proceed, (DialogInterface dialog, int which) -> {
 177             // Check to make sure the SSL error handler is not null.  This might happen if multiple dialogs are displayed at once.
 178             if (sslErrorHandler != null) {
 179                 // Cancel the request.
 180                 sslErrorHandler.proceed();
 181
 182                 // Reset the SSL error handler.
 183                 nestedScrollWebView.resetSslErrorHandler();
 184             }
 185         });
 186
 187
 188         // Create an alert dialog from the alert dialog builder.
 189         AlertDialog alertDialog = dialogBuilder.create();
 190
 191         // Get a handle for the shared preferences.
 192         SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getContext());
 193
 194         // Get the screenshot preference.
 195         boolean allowScreenshots = sharedPreferences.getBoolean("allow_screenshots", false);
 196
 197         // Disable screenshots if not allowed.
 198         if (!allowScreenshots) {
 199             // Remove the warning below that `getWindow()` might be null.
 200             assert alertDialog.getWindow() != null;
 201
 202             // Disable screenshots.
 203             alertDialog.getWindow().addFlags(WindowManager.LayoutParams.FLAG_SECURE);
 204         }
 205
 206         // Get a URI for the URL with errors.
 207         Uri uriWithErrors = Uri.parse(urlWithErrors);
 208
 209         // Get the IP addresses for the URI.
 210         new GetIpAddresses(getActivity(), alertDialog).execute(uriWithErrors.getHost());
 211
 212         // The alert dialog must be shown before the contents can be modified.
 213         alertDialog.show();
 214
 215         // Get handles for the `TextViews`
 216         TextView primaryErrorTextView = alertDialog.findViewById(R.id.primary_error);
 217         TextView urlTextView = alertDialog.findViewById(R.id.url);
 218         TextView issuedToCNameTextView = alertDialog.findViewById(R.id.issued_to_cname);
 219         TextView issuedToONameTextView = alertDialog.findViewById(R.id.issued_to_oname);
 220         TextView issuedToUNameTextView = alertDialog.findViewById(R.id.issued_to_uname);
 221         TextView issuedByTextView = alertDialog.findViewById(R.id.issued_by_textview);
 222         TextView issuedByCNameTextView = alertDialog.findViewById(R.id.issued_by_cname);
 223         TextView issuedByONameTextView = alertDialog.findViewById(R.id.issued_by_oname);
 224         TextView issuedByUNameTextView = alertDialog.findViewById(R.id.issued_by_uname);
 225         TextView validDatesTextView = alertDialog.findViewById(R.id.valid_dates_textview);
 226         TextView startDateTextView = alertDialog.findViewById(R.id.start_date);
 227         TextView endDateTextView = alertDialog.findViewById(R.id.end_date);
 228
 229         // Remove the incorrect lint warnings below that the views might be null.
 230         assert primaryErrorTextView != null;
 231         assert urlTextView != null;
 232         assert issuedToCNameTextView != null;
 233         assert issuedToONameTextView != null;
 234         assert issuedToUNameTextView != null;
 235         assert issuedByTextView != null;
 236         assert issuedByCNameTextView != null;
 237         assert issuedByONameTextView != null;
 238         assert issuedByUNameTextView != null;
 239         assert validDatesTextView != null;
 240         assert startDateTextView != null;
 241         assert endDateTextView != null;
 242
 243         // Setup the common strings.
 244         String urlLabel = getString(R.string.url_label) + "  ";
 245         String cNameLabel = getString(R.string.common_name) + "  ";
 246         String oNameLabel = getString(R.string.organization) + "  ";
 247         String uNameLabel = getString(R.string.organizational_unit) + "  ";
 248         String startDateLabel = getString(R.string.start_date) + "  ";
 249         String endDateLabel = getString(R.string.end_date) + "  ";
 250
 251         // Create a spannable string builder for each text view that needs multiple colors of text.
 252         SpannableStringBuilder urlStringBuilder = new SpannableStringBuilder(urlLabel + urlWithErrors);
 253         SpannableStringBuilder issuedToCNameStringBuilder = new SpannableStringBuilder(cNameLabel + issuedToCName);
 254         SpannableStringBuilder issuedToONameStringBuilder = new SpannableStringBuilder(oNameLabel + issuedToOName);
 255         SpannableStringBuilder issuedToUNameStringBuilder = new SpannableStringBuilder(uNameLabel + issuedToUName);
 256         SpannableStringBuilder issuedByCNameStringBuilder = new SpannableStringBuilder(cNameLabel + issuedByCName);
 257         SpannableStringBuilder issuedByONameStringBuilder = new SpannableStringBuilder(oNameLabel + issuedByOName);
 258         SpannableStringBuilder issuedByUNameStringBuilder = new SpannableStringBuilder(uNameLabel + issuedByUName);
 259         SpannableStringBuilder startDateStringBuilder = new SpannableStringBuilder(startDateLabel + startDate);
 260         SpannableStringBuilder endDateStringBuilder = new SpannableStringBuilder((endDateLabel + endDate));
 261
 262         // Define the color spans.
 263         ForegroundColorSpan blueColorSpan;
 264         ForegroundColorSpan redColorSpan;
 265
 266         // Set the color spans according to the theme.  The deprecated `getResources()` must be used until the minimum API >= 23.
 267         if (currentThemeStatus == Configuration.UI_MODE_NIGHT_NO) {
 268             blueColorSpan = new ForegroundColorSpan(getResources().getColor(R.color.blue_700));
 269             redColorSpan = new ForegroundColorSpan(getResources().getColor(R.color.red_a700));
 270         } else {
 271             blueColorSpan = new ForegroundColorSpan(getResources().getColor(R.color.violet_500));
 272             redColorSpan = new ForegroundColorSpan(getResources().getColor(R.color.red_900));
 273         }
 274
 275         // Setup the spans to display the certificate information in blue.  `SPAN_INCLUSIVE_INCLUSIVE` allows the span to grow in either direction.
 276         urlStringBuilder.setSpan(blueColorSpan, urlLabel.length(), urlStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 277         issuedToCNameStringBuilder.setSpan(blueColorSpan, cNameLabel.length(), issuedToCNameStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 278         issuedToONameStringBuilder.setSpan(blueColorSpan, oNameLabel.length(), issuedToONameStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 279         issuedToUNameStringBuilder.setSpan(blueColorSpan, uNameLabel.length(), issuedToUNameStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 280         issuedByCNameStringBuilder.setSpan(blueColorSpan, cNameLabel.length(), issuedByCNameStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 281         issuedByONameStringBuilder.setSpan(blueColorSpan, oNameLabel.length(), issuedByONameStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 282         issuedByUNameStringBuilder.setSpan(blueColorSpan, uNameLabel.length(), issuedByUNameStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 283         startDateStringBuilder.setSpan(blueColorSpan, startDateLabel.length(), startDateStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 284         endDateStringBuilder.setSpan(blueColorSpan, endDateLabel.length(), endDateStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 285
 286         // Initialize `primaryErrorString`.
 287         String primaryErrorString = "";
 288
 289         // Highlight the primary error in red and store the primary error string in `primaryErrorString`.
 290         switch (primaryErrorInt) {
 291             case SslError.SSL_IDMISMATCH:
 292                 // Change the URL span colors to red.
 293                 urlStringBuilder.setSpan(redColorSpan, urlLabel.length(), urlStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 294                 issuedToCNameStringBuilder.setSpan(redColorSpan, cNameLabel.length(), issuedToCNameStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 295
 296                 // Store the primary error string.
 297                 primaryErrorString = getString(R.string.cn_mismatch);
 298                 break;
 299
 300             case SslError.SSL_UNTRUSTED:
 301                 // Change the issued by text view text to red.  The deprecated `getResources().getColor` must be used until the minimum API >= 23.
 302                 if (currentThemeStatus == Configuration.UI_MODE_NIGHT_YES) {
 303                     issuedByTextView.setTextColor(getResources().getColor(R.color.red_900));
 304                 } else {
 305                     issuedByTextView.setTextColor(getResources().getColor(R.color.red_a700));
 306                 }
 307
 308                 // Change the issued by span color to red.
 309                 issuedByCNameStringBuilder.setSpan(redColorSpan, cNameLabel.length(), issuedByCNameStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 310                 issuedByONameStringBuilder.setSpan(redColorSpan, oNameLabel.length(), issuedByONameStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 311                 issuedByUNameStringBuilder.setSpan(redColorSpan, uNameLabel.length(), issuedByUNameStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 312
 313                 // Store the primary error string.
 314                 primaryErrorString = getString(R.string.untrusted);
 315                 break;
 316
 317             case SslError.SSL_DATE_INVALID:
 318                 // Change the valid dates text view text to red.  The deprecated `getResources().getColor` must be used until the minimum API >= 23.
 319                 if (currentThemeStatus == Configuration.UI_MODE_NIGHT_YES) {
 320                     validDatesTextView.setTextColor(getResources().getColor(R.color.red_900));
 321                 } else {
 322                     validDatesTextView.setTextColor(getResources().getColor(R.color.red_a700));
 323                 }
 324
 325                 // Change the date span colors to red.
 326                 startDateStringBuilder.setSpan(redColorSpan, startDateLabel.length(), startDateStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 327                 endDateStringBuilder.setSpan(redColorSpan, endDateLabel.length(), endDateStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 328
 329                 // Store the primary error string.
 330                 primaryErrorString = getString(R.string.invalid_date);
 331                 break;
 332
 333             case SslError.SSL_NOTYETVALID:
 334                 // Change the start date span color to red.
 335                 startDateStringBuilder.setSpan(redColorSpan, startDateLabel.length(), startDateStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 336
 337                 // Store the primary error string.
 338                 primaryErrorString = getString(R.string.future_certificate);
 339                 break;
 340
 341             case SslError.SSL_EXPIRED:
 342                 // Change the end date span color to red.
 343                 endDateStringBuilder.setSpan(redColorSpan, endDateLabel.length(), endDateStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 344
 345                 // Store the primary error string.
 346                 primaryErrorString = getString(R.string.expired_certificate);
 347                 break;
 348
 349             case SslError.SSL_INVALID:
 350                 // Store the primary error string.
 351                 primaryErrorString = getString(R.string.invalid_certificate);
 352                 break;
 353         }
 354
 355
 356         // Display the strings.
 357         primaryErrorTextView.setText(primaryErrorString);
 358         urlTextView.setText(urlStringBuilder);
 359         issuedToCNameTextView.setText(issuedToCNameStringBuilder);
 360         issuedToONameTextView.setText(issuedToONameStringBuilder);
 361         issuedToUNameTextView.setText(issuedToUNameStringBuilder);
 362         issuedByCNameTextView.setText(issuedByCNameStringBuilder);
 363         issuedByONameTextView.setText(issuedByONameStringBuilder);
 364         issuedByUNameTextView.setText(issuedByUNameStringBuilder);
 365         startDateTextView.setText(startDateStringBuilder);
 366         endDateTextView.setText(endDateStringBuilder);
 367
 368         // `onCreateDialog` requires the return of an alert dialog.
 369         return alertDialog;
 370     }
 371
 372
 373     // This must run asynchronously because it involves a network request.  `String` declares the parameters.  `Void` does not declare progress units.  `SpannableStringBuilder` contains the results.
 374     private static class GetIpAddresses extends AsyncTask<String, Void, SpannableStringBuilder> {
 375         // The weak references are used to determine if the activity or the alert dialog have disappeared while the AsyncTask is running.
 376         private WeakReference<Activity> activityWeakReference;
 377         private WeakReference<AlertDialog> alertDialogWeakReference;
 378
 379         GetIpAddresses(Activity activity, AlertDialog alertDialog) {
 380             // Populate the weak references.
 381             activityWeakReference = new WeakReference<>(activity);
 382             alertDialogWeakReference = new WeakReference<>(alertDialog);
 383         }
 384
 385         @Override
 386         protected SpannableStringBuilder doInBackground(String... domainName) {
 387             // Get handles for the activity and the alert dialog.
 388             Activity activity = activityWeakReference.get();
 389             AlertDialog alertDialog = alertDialogWeakReference.get();
 390
 391             // Abort if the activity or the dialog is gone.
 392             if ((activity == null) || (activity.isFinishing()) || (alertDialog == null)) {
 393                 return new SpannableStringBuilder();
 394             }
 395
 396             // Initialize an IP address string builder.
 397             StringBuilder ipAddresses = new StringBuilder();
 398
 399             // Get an array with the IP addresses for the host.
 400             try {
 401                 // Get an array with all the IP addresses for the domain.
 402                 InetAddress[] inetAddressesArray = InetAddress.getAllByName(domainName[0]);
 403
 404                 // Add each IP address to the string builder.
 405                 for (InetAddress inetAddress : inetAddressesArray) {
 406                     // Check to see if this is not the first IP address.
 407                     if (ipAddresses.length() > 0) {
 408                         // Add a line break to the string builder first.
 409                         ipAddresses.append("\n");
 410                     }
 411
 412                     // Add the IP Address to the string builder.
 413                     ipAddresses.append(inetAddress.getHostAddress());
 414                 }
 415             } catch (UnknownHostException exception) {
 416                 // Do nothing.
 417             }
 418
 419             // Set the label.
 420             String ipAddressesLabel = activity.getString(R.string.ip_addresses) + "  ";
 421
 422             // Create a spannable string builder.
 423             SpannableStringBuilder ipAddressesStringBuilder = new SpannableStringBuilder(ipAddressesLabel + ipAddresses);
 424
 425             // Create a blue foreground color span.
 426             ForegroundColorSpan blueColorSpan;
 427
 428             // Get the current theme status.
 429             int currentThemeStatus = activity.getResources().getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK;
 430
 431             // Set the blue color span according to the theme.  The deprecated `getColor()` must be used until the minimum API >= 23.
 432             if (currentThemeStatus == Configuration.UI_MODE_NIGHT_YES) {
 433                 blueColorSpan = new ForegroundColorSpan(activity.getResources().getColor(R.color.violet_500));
 434             } else {
 435                 blueColorSpan = new ForegroundColorSpan(activity.getResources().getColor(R.color.blue_700));
 436             }
 437
 438             // Set the string builder to display the certificate information in blue.  `SPAN_INCLUSIVE_INCLUSIVE` allows the span to grow in either direction.
 439             ipAddressesStringBuilder.setSpan(blueColorSpan, ipAddressesLabel.length(), ipAddressesStringBuilder.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE);
 440
 441             // Return the formatted string.
 442             return ipAddressesStringBuilder;
 443         }
 444
 445         // `onPostExecute()` operates on the UI thread.
 446         @Override
 447         protected void onPostExecute(SpannableStringBuilder ipAddresses) {
 448             // Get handles for the activity and the alert dialog.
 449             Activity activity = activityWeakReference.get();
 450             AlertDialog alertDialog = alertDialogWeakReference.get();
 451
 452             // Abort if the activity or the alert dialog is gone.
 453             if ((activity == null) || (activity.isFinishing()) || (alertDialog == null)) {
 454                 return;
 455             }
 456
 457             // Get a handle for the IP addresses text view.
 458             TextView ipAddressesTextView = alertDialog.findViewById(R.id.ip_addresses);
 459
 460             // Remove the incorrect lint warning below that the view might be null.
 461             assert ipAddressesTextView != null;
 462
 463             // Populate the IP addresses text view.
 464             ipAddressesTextView.setText(ipAddresses);
 465         }
 466     }
 467 }