TYPO3 v15 dev-main snapshot ()

Classes/Error/AbstractExceptionHandler.php

@@ -0,0 +1,246 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error;
+
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Log\LoggerAwareInterface;
+use Psr\Log\LoggerAwareTrait;
+use TYPO3\CMS\Core\Authentication\BackendUserAuthentication;
+use TYPO3\CMS\Core\Database\ConnectionPool;
+use TYPO3\CMS\Core\Error\Http\StatusException;
+use TYPO3\CMS\Core\Http\ApplicationType;
+use TYPO3\CMS\Core\Http\NormalizedParams;
+use TYPO3\CMS\Core\SingletonInterface;
+use TYPO3\CMS\Core\SysLog\Action as SystemLogGenericAction;
+use TYPO3\CMS\Core\SysLog\Error as SystemLogErrorClassification;
+use TYPO3\CMS\Core\SysLog\Type as SystemLogType;
+use TYPO3\CMS\Core\Utility\GeneralUtility;
+use TYPO3\CMS\Core\Utility\HttpUtility;
+
+/**
+ * An abstract exception handler
+ *
+ * This file is a backport from TYPO3 Flow
+ */
+abstract class AbstractExceptionHandler implements ExceptionHandlerInterface, SingletonInterface, LoggerAwareInterface
+{
+    use LoggerAwareTrait;
+
+    public const CONTEXT_WEB = 'WEB';
+    public const CONTEXT_CLI = 'CLI';
+
+    protected const IGNORED_EXCEPTION_CODES = [
+        1396795884, // Current host header value does not match the configured trusted hosts pattern
+        1616175867, // Backend login request is rate limited
+        1616175847, // Frontend login request is rate limited
+        1436717275, // Request with unsupported HTTP method
+        1699604555, // Outdated __trustedProperties format in extbase property mapping
+        1517949792, // The IP address of your client does not match the list of allowed IP addresses
+        1517949793, // Backend access by browser is locked for maintenance
+        1517949794, // Backend and Install Tool are locked for maintenance
+        1436717270, // Client sends a header with an invalid name
+        1436717269, // Client sends a header with an invalid value
+    ];
+
+    public const IGNORED_HMAC_EXCEPTION_CODES = [
+        1581862822, // Failed HMAC validation due to modified __trustedProperties in extbase property mapping
+        1581862823, // Failed HMAC validation due to modified form state in ext:forms
+        1320830018, // Failed HMAC validation due to modified HMAC string in Extbase HashService
+        1320830276, // Failed HMAC validation due to too short HMAC string in Extbase HashService
+        1704454157, // Failed HMAC validation due to modified HMAC string in Core HashService
+        1704454152, // Failed HMAC validation due to too short HMAC string in Core HashService
+    ];
+
+    protected bool $logExceptionStackTrace = false;
+
+    /**
+     * Displays the given exception
+     *
+     * @param \Throwable $exception The throwable object.
+     *
+     * @throws \Exception
+     */
+    public function handleException(\Throwable $exception)
+    {
+        switch (PHP_SAPI) {
+            case 'cli':
+                $this->echoExceptionCLI($exception);
+                break;
+            default:
+                $this->echoExceptionWeb($exception);
+        }
+    }
+
+    /**
+     * Writes exception to different logs
+     *
+     * @param \Throwable $exception The throwable object.
+     * @param string $mode The context where the exception was thrown.
+     *     Either self::CONTEXT_WEB or self::CONTEXT_CLI.
+     */
+    protected function writeLogEntries(\Throwable $exception, string $mode): void
+    {
+        // Do not write any logs for some messages to avoid filling up tables or files with illegal requests
+        $ignoredCodes = array_merge(self::IGNORED_EXCEPTION_CODES, self::IGNORED_HMAC_EXCEPTION_CODES);
+        if (in_array($exception->getCode(), $ignoredCodes, true)) {
+            return;
+        }
+
+        // PSR-3 logging framework.
+        try {
+            if ($this->logger) {
+                // 'FE' if in FrontendApplication, else 'BE' (also in CLI without request object)
+                // @todo: We could reconsider this construct with PHP 8.5: It might be possible to register
+                //        the exception handler early during bootstrap. Then, later, when a request is available,
+                //        get it, and reconfigure exception handler to its final state. This would avoid the runtime
+                //        dependency to request including the funny PHP_SAPI fork in handleException().
+                $applicationMode = ($GLOBALS['TYPO3_REQUEST'] ?? null) instanceof ServerRequestInterface
+                    && ApplicationType::fromRequest($GLOBALS['TYPO3_REQUEST'])->isFrontend()
+                    ? 'FE'
+                    : 'BE';
+                $requestUrl = $this->anonymizeToken(NormalizedParams::createFromServerParams($_SERVER)->getRequestUrl());
+                $this->logger->critical('Core: Exception handler ({mode}: {application_mode}): {exception_class}, code #{exception_code}, file {file}, line {line}: {message}', [
+                    'mode' => $mode,
+                    'application_mode' => $applicationMode,
+                    'exception_class' => get_class($exception),
+                    'exception_code' => $exception->getCode(),
+                    'file' => $exception->getFile(),
+                    'line' => $exception->getLine(),
+                    'message' => $exception->getMessage(),
+                    'request_url' => $requestUrl,
+                    'exception' => $this->logExceptionStackTrace ? $exception : null,
+                ]);
+            }
+        } catch (\Exception $exception) {
+            // A nested exception here was probably caused by a database failure, which means there's little
+            // else that can be done other than moving on and letting the system hard-fail.
+        }
+
+        // Legacy logger.  Remove this section eventually.
+        $filePathAndName = $exception->getFile();
+        $exceptionCodeNumber = $exception->getCode() > 0 ? '#' . $exception->getCode() . ': ' : '';
+        $logTitle = 'Core: Exception handler (' . $mode . ')';
+        $logMessage = 'Uncaught TYPO3 Exception: ' . $exceptionCodeNumber . $exception->getMessage() . ' | '
+            . get_class($exception) . ' thrown in file ' . $filePathAndName . ' in line ' . $exception->getLine();
+        if ($mode === self::CONTEXT_WEB) {
+            $logMessage .= '. Requested URL: ' . $this->anonymizeToken(NormalizedParams::createFromServerParams($_SERVER)->getRequestUrl());
+        }
+        // When database credentials are wrong, the exception is probably
+        // caused by this. Therefore we cannot do any database operation,
+        // otherwise this will lead into recurring exceptions.
+        try {
+            // Write error message to sys_log table
+            $this->writeLog($logTitle . ': ' . $logMessage);
+        } catch (\Throwable $exception) {
+        }
+    }
+
+    /**
+     * Writes an exception in the sys_log table
+     *
+     * @param string $logMessage Default text that follows the message.
+     */
+    protected function writeLog(string $logMessage)
+    {
+        $connection = GeneralUtility::makeInstance(ConnectionPool::class)
+            ->getConnectionForTable('sys_log');
+
+        if (!$connection->isConnected()) {
+            return;
+        }
+        $userId = 0;
+        $workspace = 0;
+        $data = [];
+        $backendUser = $this->getBackendUser();
+        if ($backendUser !== null) {
+            if (isset($backendUser->user['uid'])) {
+                $userId = $backendUser->user['uid'];
+            }
+            $workspace = $backendUser->workspace;
+            if ($backUserId = $backendUser->getOriginalUserIdWhenInSwitchUserMode()) {
+                $data['originalUser'] = $backUserId;
+            }
+        }
+
+        $connection->insert(
+            'sys_log',
+            [
+                'userid' => $userId,
+                'type' => SystemLogType::ERROR,
+                'channel' => SystemLogType::toChannel(SystemLogType::ERROR),
+                'action' => SystemLogGenericAction::UNDEFINED,
+                'error' => SystemLogErrorClassification::SYSTEM_ERROR,
+                'level' => SystemLogType::toLevel(SystemLogType::ERROR),
+                'details' => str_replace('%', '%%', $logMessage),
+                'log_data' => empty($data) ? '' : json_encode($data),
+                'IP' => NormalizedParams::createFromServerParams($_SERVER)->getRemoteAddress(),
+                'tstamp' => $GLOBALS['EXEC_TIME'],
+                'workspace' => $workspace,
+            ]
+        );
+    }
+
+    /**
+     * Sends the HTTP Status 500 code, if $exception is *not* a
+     * TYPO3\CMS\Core\Error\Http\StatusException and headers are not sent, yet.
+     *
+     * @param \Throwable $exception The throwable object.
+     */
+    protected function sendStatusHeaders(\Throwable $exception)
+    {
+        $headers = $exception instanceof StatusException
+            ? $exception->getStatusHeaders()
+            : [HttpUtility::HTTP_STATUS_500];
+        if (!headers_sent()) {
+            foreach ($headers as $header) {
+                header($header);
+            }
+        }
+    }
+
+    /**
+     * Derives the numeric HTTP status code from the exception.
+     *
+     * Mirrors the logic of {@see sendStatusHeaders()}: returns the status code
+     * from the HTTP status line of a StatusException, or 500 for any other exception.
+     */
+    protected function getHttpStatusCodeFromException(\Throwable $exception): int
+    {
+        if (!($exception instanceof StatusException)) {
+            return 500;
+        }
+        foreach ($exception->getStatusHeaders() ?? [] as $header) {
+            if (preg_match('/^HTTP\/[\d.]+\s+(\d{3})/', $header, $matches)) {
+                return (int)$matches[1];
+            }
+        }
+        return 500;
+    }
+
+    protected function getBackendUser(): ?BackendUserAuthentication
+    {
+        return $GLOBALS['BE_USER'] ?? null;
+    }
+
+    /**
+     * Replaces the generated token with a generic equivalent
+     */
+    protected function anonymizeToken(string $requestedUrl): string
+    {
+        $pattern = '/(?:(?<=[tT]oken=)|(?<=[tT]oken%3D))[0-9a-fA-F]{40}/';
+        return preg_replace($pattern, '--AnonymizedToken--', $requestedUrl);
+    }
+}

Classes/Error/DebugExceptionHandler.php

@@ -0,0 +1,668 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error;
+
+use TYPO3\CMS\Core\Core\Environment;
+use TYPO3\CMS\Core\Information\Typo3Information;
+
+/**
+ * A basic but solid exception handler which catches everything which
+ * falls through the other exception handlers and provides useful debugging
+ * information.
+ */
+class DebugExceptionHandler extends AbstractExceptionHandler
+{
+    protected bool $logExceptionStackTrace = true;
+
+    /**
+     * Constructs this exception handler - registers itself as the default exception handler.
+     */
+    public function __construct()
+    {
+        set_exception_handler($this->handleException(...));
+    }
+
+    /**
+     * Formats and echoes the exception as XHTML.
+     *
+     * @param \Throwable $exception The throwable object.
+     */
+    public function echoExceptionWeb(\Throwable $exception)
+    {
+        $this->sendStatusHeaders($exception);
+        $this->writeLogEntries($exception, self::CONTEXT_WEB);
+
+        $content = $this->getContent($exception);
+        $css = $this->getStylesheet();
+        $js = $this->getJavascript();
+
+        echo <<<HTML
+<!DOCTYPE html>
+<html>
+    <head>
+        <meta charset="UTF-8" />
+        <title>TYPO3 Exception</title>
+        <meta name="robots" content="noindex,nofollow" />
+        <style>$css</style>
+        <script>$js</script>
+    </head>
+    <body>
+        $content
+    </body>
+</html>
+HTML;
+    }
+
+    /**
+     * Formats and echoes the exception for the command line
+     *
+     * @param \Throwable $exception The throwable object.
+     */
+    public function echoExceptionCLI(\Throwable $exception)
+    {
+        $filePathAndName = $exception->getFile();
+        $exceptionCodeNumber = $exception->getCode() > 0 ? '#' . $exception->getCode() . ': ' : '';
+        $this->writeLogEntries($exception, self::CONTEXT_CLI);
+        echo LF . 'Uncaught TYPO3 Exception ' . $exceptionCodeNumber . $exception->getMessage() . LF;
+        echo 'thrown in file ' . $filePathAndName . LF;
+        echo 'in line ' . $exception->getLine() . LF . LF;
+        die(1);
+    }
+
+    /**
+     * Generates the HTML for the error output.
+     */
+    protected function getContent(\Throwable $throwable): string
+    {
+        $content = '';
+
+        // exceptions can be chained
+        // for easier debugging, all exceptions are displayed to the developer
+        $throwables = $this->getAllThrowables($throwable);
+        $count = count($throwables);
+        foreach ($throwables as $position => $e) {
+            $content .= $this->getSingleThrowableContent($e, $position + 1, $count);
+        }
+
+        $exceptionInfo = '';
+        if ($throwable->getCode() > 0) {
+            $documentationLink = Typo3Information::URL_EXCEPTION . 'debug/' . $throwable->getCode();
+            $exceptionInfo = <<<INFO
+            <div class="container">
+                <div class="callout">
+                    <div class="callout-content">
+                        <div class="callout-title">Get help in the TYPO3 Documentation</div>
+                        <div class="callout-body">
+                            <p>
+                                If you need help solving this exception, you can have a look at the TYPO3 Documentation.
+                                There you can find solutions provided by the TYPO3 community.
+                                Once you have found a solution to the problem, help others by contributing to the
+                                documentation page.
+                            </p>
+                            <p>
+                                <a href="$documentationLink" target="_blank" rel="noreferrer">Find a solution for this exception in the TYPO3 Documentation.</a>
+                                <span id="stacktrace-action-buttons"></span>
+                            </p>
+                        </div>
+                    </div>
+                </div>
+            </div>
+INFO;
+        }
+
+        $typo3Logo = $this->getTypo3LogoAsSvg();
+
+        try {
+            // This outside dependency class is always loaded before the exception handler is setup.
+            // So it is safe to access without affecting the output of this handler.
+            $projectPath = Environment::getProjectPath() . DIRECTORY_SEPARATOR;
+        } catch (\Throwable) {
+            // just in case something goes wrong.
+            $projectPath = '';
+        }
+
+        $projectPathEscaped = $this->escapeHtml($projectPath);
+
+        return <<<HTML
+            <div class="exception-page" data-project-path="$projectPathEscaped">
+                <div class="exception-summary">
+                    <div class="container">
+                        <div class="exception-message-wrapper">
+                            <div class="exception-illustration hidden-xs-down">$typo3Logo</div>
+                            <h1 class="exception-message break-long-words">
+                                Whoops, looks like something went wrong.
+                                <span id="stacktrace-action-buttons"></span>
+                            </h1>
+                        </div>
+                    </div>
+                </div>
+
+                $exceptionInfo
+
+                <div class="container">
+                    $content
+                </div>
+            </div>
+HTML;
+    }
+
+    /**
+     * Renders the HTML for a single throwable.
+     */
+    protected function getSingleThrowableContent(\Throwable $throwable, int $index, int $total): string
+    {
+        $exceptionTitle = get_class($throwable);
+        $exceptionCode = $throwable->getCode() ? '#' . $throwable->getCode() . ' ' : '';
+        $exceptionMessage = $this->escapeHtml($throwable->getMessage());
+
+        // The trace does not contain the step where the exception is thrown.
+        // To display it as well it is added manually to the trace.
+        $trace = $throwable->getTrace();
+        array_unshift($trace, [
+            'file' => $throwable->getFile(),
+            'line' => $throwable->getLine(),
+            'args' => [],
+        ]);
+
+        $backtraceCode = $this->getBacktraceCode($trace);
+
+        return <<<HTML
+            <div class="trace">
+                <div class="trace-head">
+                    <h3 class="trace-class">
+                        <span class="text-variant">({$index}/{$total})</span>
+                        <span class="exception-title">{$exceptionCode}{$exceptionTitle}</span>
+                    </h3>
+                    <p class="trace-message break-long-words">{$exceptionMessage}</p>
+                </div>
+                <div class="trace-body">
+                    {$backtraceCode}
+                </div>
+            </div>
+HTML;
+    }
+
+    /**
+     * Generates the stylesheet needed to display the error page.
+     */
+    protected function getStylesheet(): string
+    {
+        return <<<STYLESHEET
+            html {
+                -webkit-text-size-adjust: 100%;
+                -ms-text-size-adjust: 100%;
+                -ms-overflow-style: scrollbar;
+                -webkit-tap-highlight-color: transparent;
+            }
+
+            body {
+                margin: 0;
+            }
+
+            .exception-page {
+                background-color: #eaeaea;
+                color: #212121;
+                font-family: -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol","Noto Color Emoji";
+                font-weight: 400;
+                height: 100dvh;
+                line-height: 1.5;
+                overflow-x: hidden;
+                overflow-y: scroll;
+                text-align: left;
+                top: 0;
+            }
+
+            .panel-collapse .exception-page {
+                height: 100%;
+            }
+
+            .exception-page a {
+                color: #ff8700;
+                text-decoration: underline;
+            }
+
+            .exception-page a:hover {
+                text-decoration: none;
+            }
+
+            .exception-page abbr[title] {
+                border-bottom: none;
+                cursor: help;
+                text-decoration: none;
+            }
+
+            .exception-page code,
+            .exception-page kbd,
+            .exception-page pre,
+            .exception-page samp {
+                font-family: SFMono-Regular,Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace;
+                font-size: 1em;
+            }
+
+            .exception-page pre {
+                background-color: #ffffff;
+                overflow-x: auto;
+                border: 1px solid rgba(0,0,0,0.125);
+            }
+
+            .exception-page pre span {
+                display: block;
+                line-height: 1.3em;
+            }
+
+            .exception-page pre span:before {
+                display: inline-block;
+                content: attr(data-line);
+                border-right: 1px solid #b9b9b9;
+                margin-right: 0.5em;
+                padding-right: 0.5em;
+                background-color: #f4f4f4;
+                width: 4em;
+                text-align: right;
+                color: #515151;
+            }
+
+            .exception-page pre span.highlight {
+                background-color: #cce5ff;
+            }
+
+            .exception-page .break-long-words {
+                -ms-word-break: break-all;
+                word-break: break-all;
+                word-break: break-word;
+                -webkit-hyphens: auto;
+                -moz-hyphens: auto;
+                hyphens: auto;
+            }
+
+            .exception-page .callout {
+                padding: 1.5rem;
+                background-color: #fff;
+                margin-bottom: 2em;
+                box-shadow: 0 2px 1px rgba(0,0,0,.15);
+                border-left: 3px solid #8c8c8c;
+            }
+
+            .exception-page .callout-title {
+                margin: 0;
+            }
+
+            .exception-page .callout-body p:last-child {
+                margin-bottom: 0;
+            }
+
+            .exception-page .container {
+                max-width: 1140px;
+                margin: 0 auto;
+                padding: 0 30px;
+            }
+
+            .panel-collapse .exception-page .container {
+                width: 100%;
+            }
+
+            .exception-page .exception-illustration {
+                width: 3em;
+                height: 3em;
+                float: left;
+                margin-right: 1rem;
+            }
+
+            .exception-page .exception-illustration svg {
+                width: 100%;
+            }
+
+            .exception-page .exception-illustration svg path {
+                fill: #ff8700;
+            }
+
+            .exception-page .exception-summary {
+                background: #000000;
+                color: #fff;
+                padding: 1.5rem 0;
+                margin-bottom: 2rem;
+            }
+
+            .exception-page .exception-summary h1 {
+                margin: 0;
+            }
+
+            .exception-page .text-variant {
+                opacity: 0.5;
+            }
+
+            .exception-page .trace {
+                background-color: #fff;
+                margin-bottom: 2rem;
+                box-shadow: 0 2px 1px rgba(0,0,0,.15);
+            }
+
+            .exception-page .trace-arguments {
+                color: #8c8c8c;
+            }
+
+            .exception-page .trace-hint {
+                margin: 0 0 0.5rem 0;
+                text-align: center;
+            }
+
+            .exception-page .trace-body {
+            }
+
+            .exception-page .trace-call {
+                margin-bottom: 1rem;
+            }
+
+            .exception-page .trace-class {
+                margin: 0;
+            }
+
+            .exception-page .trace-file pre {
+                margin-top: 1.5rem;
+                margin-bottom: 0;
+            }
+
+            .exception-page .trace-head {
+                color: #721c24;
+                background-color: #f8d7da;
+                padding: 1.5rem;
+            }
+
+            .exception-page .trace-file-path {
+                word-break: break-all;
+            }
+
+            .exception-page .trace-message {
+                margin-bottom: 0;
+            }
+
+            .exception-page .trace-step {
+                padding: 1.5rem;
+                border-bottom: 1px solid #b9b9b9;
+            }
+
+            .exception-page .trace-step > *:first-child {
+                margin-top: 0;
+            }
+
+            .exception-page .trace-step > *:last-child {
+                margin-bottom: 0;
+            }
+
+            .exception-page .trace-step:nth-child(even)
+            {
+                background-color: #fafafa;
+            }
+
+            .exception-page .trace-step:last-child {
+                border-bottom: none;
+            }
+
+            .exception-page .copy-button {
+                cursor: pointer;
+                border: 0.1rem solid transparent;
+                background-color: transparent;
+                padding: 0;
+                margin-left: 1rem;
+            }
+
+            .exception-page .copy-button:hover {
+                border: 0.1rem solid #b9b9b9;
+            }
+
+            .exception-page #stacktrace-action-buttons {
+                display: inline-flex;
+                justify-content: center;
+                gap: 0.5rem;
+                margin-top: 1rem;
+            }
+
+            .exception-page .stacktrace-action-button {
+                cursor: pointer;
+                padding: 0.5rem;
+                -webkit-text-size-adjust: 100%;
+                -webkit-tap-highlight-color: rgba(0,0,0,0);
+                box-sizing: border-box;
+                background-color: color(srgb 0.97 0.97 0.97);
+                border: 1px solid color(srgb 0.75 0.75 0.75);
+                border-radius: .75em;
+                color: color(srgb 0.1 0.1 0.1);
+                display: inline-flex;
+                font-weight: 400;
+                gap: .35em;
+                justify-content: center;
+                outline-offset: 0;
+                text-decoration: none;
+                --typo3-transition-color: color .15s ease-in-out,background-color .15s ease-in-out,border-color .15s ease-in-out,box-shadow .15s ease-in-out,opacity .15s ease-in-out;
+                transition: var(--typo3-transition-color);
+                user-select: none;
+                vertical-align: middle;
+                white-space: nowrap;
+                margin-bottom: 0;
+                margin-top: 0;
+            }
+
+            pre.plaintextFallback {
+                margin: 2rem auto;
+                border: 1px solid black;
+                max-height: 250px;
+                font-size: 0.8em;
+                padding: 1rem;
+            }
+
+STYLESHEET;
+    }
+
+    /**
+     * Returns JavaScript functionality. Loaded from a TypeScript build.
+     * It is loaded inline, to not need to load additional URIs or build routes to assets.
+     * Also, it does not use ES6 module loading to be light-weight and dependency free.
+     */
+    protected function getJavascript(): string
+    {
+        return file_get_contents(__DIR__ . '/../../Resources/Public/JavaScript/utility/debug-exception-handler-service.js');
+    }
+
+    /**
+     * Renders the backtrace as HTML.
+     */
+    protected function getBacktraceCode(array $trace): string
+    {
+        $content = '';
+
+        foreach ($trace as $step) {
+            $content .= '<div class="trace-step">';
+            $args = $this->flattenArgs($step['args'] ?? []);
+
+            if (isset($step['function'])) {
+                $content .= '<div class="trace-call">' . sprintf(
+                    'at <span class="trace-class">%s</span><span class="trace-type">%s</span><span class="trace-method">%s</span>(<span class="trace-arguments">%s</span>)',
+                    $step['class'] ?? '',
+                    $step['type'] ?? '',
+                    $step['function'],
+                    $this->formatArgs($args)
+                ) . '</div>';
+            }
+
+            if (isset($step['file']) && isset($step['line'])) {
+                $content .= $this->getCodeSnippet($step['file'], $step['line']);
+            }
+
+            $content .= '</div>';
+        }
+
+        return $content;
+    }
+
+    /**
+     * Returns a code snippet from the specified file.
+     *
+     * @param string $filePathAndName Absolute path and file name of the PHP file
+     * @param int $lineNumber Line number defining the center of the code snippet
+     * @return string The code snippet
+     */
+    protected function getCodeSnippet(string $filePathAndName, int $lineNumber): string
+    {
+        $showLinesAround = 4;
+
+        $content = '<div class="trace-file">';
+        $content .= '<div class="trace-file-head">' . $this->formatPath($filePathAndName, $lineNumber) . '</div>';
+
+        if (@file_exists($filePathAndName)) {
+            $phpFile = @file($filePathAndName);
+            if (is_array($phpFile)) {
+                $startLine = $lineNumber > $showLinesAround ? $lineNumber - $showLinesAround : 1;
+                $phpFileCount = count($phpFile);
+                $endLine = $lineNumber < $phpFileCount - $showLinesAround ? $lineNumber + $showLinesAround + 1 : $phpFileCount + 1;
+                if ($endLine > $startLine) {
+                    $content .= '<div class="trace-file-content">';
+                    $content .= '<pre>';
+
+                    for ($line = $startLine; $line < $endLine; $line++) {
+                        $codeLine = str_replace("\t", ' ', $phpFile[$line - 1]);
+                        $spanClass = '';
+                        if ($line === $lineNumber) {
+                            $spanClass = 'highlight';
+                        }
+
+                        $content .= '<span class="' . $spanClass . '" data-line="' . $line . '">' . $this->escapeHtml($codeLine) . '</span>';
+                    }
+
+                    $content .= '</pre>';
+                    $content .= '</div>';
+                }
+            }
+        }
+
+        $content .= '</div>';
+
+        return $content;
+    }
+
+    /**
+     * Formats a path adding a line number.
+     *
+     * @param string $path The full path of the file.
+     * @param int $line The line number.
+     */
+    protected function formatPath(string $path, int $line): string
+    {
+        // "data-lineno" is evaluated by debug-exception-handler-service.js
+        return sprintf(
+            '<span class="block trace-file-path">in <strong data-lineno="%s">%s</strong>%s</span>',
+            $line > 0 ? $line : 1,
+            $this->escapeHtml($path),
+            $line > 0 ? ' line ' . $line : ''
+        );
+    }
+
+    /**
+     * Formats the arguments of a method call.
+     *
+     * @param array $args The flattened args of method/function call
+     */
+    protected function formatArgs(array $args): string
+    {
+        $result = [];
+        foreach ($args as $key => $item) {
+            if ($item[0] === 'object') {
+                $formattedValue = sprintf('<em>object</em>(%s)', $item[1]);
+            } elseif ($item[0] === 'array') {
+                $formattedValue = sprintf('<em>array</em>(%s)', is_array($item[1]) ? $this->formatArgs($item[1]) : $item[1]);
+            } elseif ($item[0] === 'null') {
+                $formattedValue = '<em>null</em>';
+            } elseif ($item[0] === 'boolean') {
+                $formattedValue = '<em>' . strtolower(var_export($item[1], true)) . '</em>';
+            } elseif ($item[0] === 'resource') {
+                $formattedValue = '<em>resource</em>';
+            } else {
+                $formattedValue = str_replace("\n", '', $this->escapeHtml(var_export($item[1], true)));
+            }
+
+            $result[] = is_int($key) ? $formattedValue : sprintf("'%s' => %s", $this->escapeHtml($key), $formattedValue);
+        }
+
+        return implode(', ', $result);
+    }
+
+    protected function flattenArgs(array $args, int $level = 0, int &$count = 0): array
+    {
+        $result = [];
+        foreach ($args as $key => $value) {
+            if (++$count > 1e4) {
+                return ['array', '*SKIPPED over 10000 entries*'];
+            }
+            if ($value instanceof \__PHP_Incomplete_Class) {
+                // is_object() returns false on PHP<=7.1
+                $result[$key] = ['incomplete-object', $this->getClassNameFromIncomplete($value)];
+            } elseif (is_object($value)) {
+                $result[$key] = ['object', get_class($value)];
+            } elseif (is_array($value)) {
+                if ($level > 10) {
+                    $result[$key] = ['array', '*DEEP NESTED ARRAY*'];
+                } else {
+                    $result[$key] = ['array', $this->flattenArgs($value, $level + 1, $count)];
+                }
+            } elseif ($value === null) {
+                $result[$key] = ['null', null];
+            } elseif (is_bool($value)) {
+                $result[$key] = ['boolean', $value];
+            } elseif (is_int($value)) {
+                $result[$key] = ['integer', $value];
+            } elseif (is_float($value)) {
+                $result[$key] = ['float', $value];
+            } elseif (is_resource($value)) {
+                $result[$key] = ['resource', get_resource_type($value)];
+            } else {
+                $result[$key] = ['string', (string)$value];
+            }
+        }
+
+        return $result;
+    }
+
+    protected function getClassNameFromIncomplete(\__PHP_Incomplete_Class $value): string
+    {
+        $array = new \ArrayObject($value);
+
+        return $array['__PHP_Incomplete_Class_Name'];
+    }
+
+    protected function escapeHtml(string $str): string
+    {
+        return htmlspecialchars($str, ENT_COMPAT | ENT_SUBSTITUTE);
+    }
+
+    protected function getTypo3LogoAsSvg(): string
+    {
+        return <<<SVG
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16"><path d="M11.1 10.3c-.2 0-.3.1-.5.1C9 10.4 6.8 5 6.8 3.2c0-.7.2-.9.4-1.1-2 .2-4.2.9-4.9 1.8-.2.2-.3.6-.3 1 0 2.8 3 9.2 5.1 9.2 1 0 2.6-1.6 4-3.8m-1-8.4c1.9 0 3.9.3 3.9 1.4 0 2.2-1.4 4.9-2.1 4.9C10.6 8.3 9 4.7 9 2.9c0-.8.3-1 1.1-1"></path></svg>
+SVG;
+    }
+
+    protected function getAllThrowables(\Throwable $throwable): array
+    {
+        $all = [$throwable];
+
+        while ($throwable = $throwable->getPrevious()) {
+            $all[] = $throwable;
+        }
+
+        return $all;
+    }
+}

Classes/Error/ErrorHandler.php

@@ -0,0 +1,290 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error;
+
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Log\LoggerAwareInterface;
+use Psr\Log\LoggerAwareTrait;
+use Psr\Log\LogLevel;
+use TYPO3\CMS\Core\Authentication\BackendUserAuthentication;
+use TYPO3\CMS\Core\Database\ConnectionPool;
+use TYPO3\CMS\Core\Http\ApplicationType;
+use TYPO3\CMS\Core\Http\NormalizedParams;
+use TYPO3\CMS\Core\Log\LogManager;
+use TYPO3\CMS\Core\Messaging\FlashMessage;
+use TYPO3\CMS\Core\Messaging\FlashMessageService;
+use TYPO3\CMS\Core\SysLog\Action as SystemLogGenericAction;
+use TYPO3\CMS\Core\SysLog\Error as SystemLogErrorClassification;
+use TYPO3\CMS\Core\SysLog\Type as SystemLogType;
+use TYPO3\CMS\Core\TimeTracker\TimeTracker;
+use TYPO3\CMS\Core\Type\ContextualFeedbackSeverity;
+use TYPO3\CMS\Core\Utility\GeneralUtility;
+
+/**
+ * Global error handler for TYPO3
+ *
+ * This file is a backport from TYPO3 Flow
+ */
+class ErrorHandler implements ErrorHandlerInterface, LoggerAwareInterface
+{
+    use LoggerAwareTrait;
+
+    protected const ERROR_LEVEL_LABELS = [
+        E_WARNING => 'PHP Warning',
+        E_NOTICE => 'PHP Notice',
+        E_USER_ERROR => 'PHP User Error',
+        E_USER_WARNING => 'PHP User Warning',
+        E_USER_NOTICE => 'PHP User Notice',
+        E_RECOVERABLE_ERROR => 'PHP Catchable Fatal Error',
+        E_USER_DEPRECATED => 'TYPO3 Deprecation Notice',
+        E_DEPRECATED => 'PHP Runtime Deprecation Notice',
+        // @todo: Remove 2048 (deprecated E_STRICT) in v14, as this value is no longer used by PHP itself
+        //        and only kept here here because possible custom PHP extensions may still use it.
+        //        See https://wiki.php.net/rfc/deprecations_php_8_4#remove_e_strict_error_level_and_deprecate_e_strict_constant
+        2048 /* deprecated E_STRICT */ => 'PHP Runtime Notice',
+    ];
+
+    /**
+     * Error levels which should result in an exception thrown.
+     */
+    protected int $exceptionalErrors = 0;
+
+    /**
+     * Error levels which should be handled.
+     */
+    protected int $errorHandlerErrors = 0;
+
+    /**
+     * Whether to write a flash message in case of an error
+     */
+    protected bool $debugMode = false;
+
+    /**
+     * Registers this class as default error handler
+     *
+     * @param int $errorHandlerErrors The integer representing the E_* error level which should be
+     */
+    public function __construct($errorHandlerErrors)
+    {
+        $excludedErrors = E_COMPILE_WARNING | E_COMPILE_ERROR | E_CORE_WARNING | E_CORE_ERROR | E_PARSE | E_ERROR;
+        // reduces error types to those a custom error handler can process
+        $this->errorHandlerErrors = (int)$errorHandlerErrors & ~$excludedErrors;
+    }
+
+    /**
+     * Defines which error levels should result in an exception thrown.
+     *
+     * @param int $exceptionalErrors The integer representing the E_* error level to handle as exceptions
+     */
+    public function setExceptionalErrors($exceptionalErrors)
+    {
+        $exceptionalErrors = (int)$exceptionalErrors;
+        // We always disallow E_USER_DEPRECATED to generate exceptions as this may cause
+        // bad user experience specifically during upgrades.
+        $this->exceptionalErrors = $exceptionalErrors & ~E_USER_DEPRECATED;
+    }
+
+    /**
+     * @param bool $debugMode
+     */
+    public function setDebugMode($debugMode)
+    {
+        $this->debugMode = (bool)$debugMode;
+    }
+
+    public function registerErrorHandler()
+    {
+        set_error_handler([$this, 'handleError']);
+    }
+
+    /**
+     * Handles an error.
+     * If the error is registered as exceptionalError it will by converted into an exception, to be handled
+     * by the configured exceptionhandler. Additionally the error message is written to the configured logs.
+     * If application is backend, the error message is also added to the flashMessageQueue, in frontend the
+     * error message is displayed in the admin panel (as TsLog message).
+     *
+     * @param int $errorLevel The error level - one of the E_* constants
+     * @param string $errorMessage The error message
+     * @param string $errorFile Name of the file the error occurred in
+     * @param int $errorLine Line number where the error occurred
+     * @return bool
+     * @throws Exception with the data passed to this method if the error is registered as exceptionalError
+     */
+    public function handleError($errorLevel, $errorMessage, $errorFile, $errorLine)
+    {
+        // Filter all errors, that should not be reported/ handled from current error reporting
+        $reportingLevel = $this->errorHandlerErrors & error_reporting();
+        // Since symfony does this:
+        // @trigger_error('...', E_USER_DEPRECATED), and we DO want to log these,
+        // we always enforce deprecation messages to be handled, even when they are silenced
+        $reportingLevel |= E_USER_DEPRECATED;
+        $shouldHandleError = (bool)($reportingLevel & $errorLevel);
+        if (!$shouldHandleError) {
+            return self::ERROR_HANDLED;
+        }
+
+        $message = self::ERROR_LEVEL_LABELS[$errorLevel] . ': ' . $errorMessage . ' in ' . $errorFile . ' line ' . $errorLine;
+        if ($errorLevel & $this->exceptionalErrors) {
+            throw new Exception($message, 1476107295);
+        }
+
+        $message = $this->getFormattedLogMessage($message);
+
+        if ($errorLevel === E_USER_DEPRECATED || $errorLevel === E_DEPRECATED) {
+            $logger = GeneralUtility::makeInstance(LogManager::class)->getLogger('TYPO3.CMS.deprecations');
+            $logger->notice($message);
+            return self::ERROR_HANDLED;
+        }
+
+        switch ($errorLevel) {
+            case E_USER_ERROR:
+            case E_RECOVERABLE_ERROR:
+                $logLevel = LogLevel::ERROR;
+                break;
+            case E_USER_WARNING:
+            case E_WARNING:
+                $logLevel = LogLevel::WARNING;
+                break;
+            default:
+                $logLevel = LogLevel::NOTICE;
+        }
+
+        if ($this->logger) {
+            $this->logger->log($logLevel, $message);
+        }
+
+        try {
+            // Write error message to TSlog (admin panel)
+            $this->getTimeTracker()->setTSlogMessage($message, $logLevel);
+        } catch (\Throwable $e) {
+            // Silently catch in case an error occurs before the DI container is in place
+        }
+        // Write error message to sys_log table (ext: belog, Tools->Log)
+        if ($errorLevel & ($GLOBALS['TYPO3_CONF_VARS']['SYS']['belogErrorReporting'] ?? 0)) {
+            // Silently catch in case an error occurs before a database connection exists.
+            try {
+                $this->writeLog($message, $logLevel);
+            } catch (\Exception $e) {
+            }
+        }
+        if ($logLevel === LogLevel::ERROR) {
+            // Let the internal handler continue. This will stop the script
+            return self::PROPAGATE_ERROR;
+        }
+        if ($this->debugMode) {
+            $this->createAndEnqueueFlashMessage($message, $errorLevel);
+        }
+        // Don't execute PHP internal error handler
+        return self::ERROR_HANDLED;
+    }
+
+    protected function createAndEnqueueFlashMessage(string $message, int $errorLevel): void
+    {
+        switch ($errorLevel) {
+            case E_USER_WARNING:
+            case E_WARNING:
+                $flashMessageSeverity = ContextualFeedbackSeverity::WARNING;
+                break;
+            default:
+                $flashMessageSeverity = ContextualFeedbackSeverity::NOTICE;
+        }
+        $flashMessage = new FlashMessage(
+            $message,
+            self::ERROR_LEVEL_LABELS[$errorLevel],
+            $flashMessageSeverity
+        );
+        $flashMessageService = GeneralUtility::makeInstance(FlashMessageService::class);
+        $defaultFlashMessageQueue = $flashMessageService->getMessageQueueByIdentifier();
+        $defaultFlashMessageQueue->enqueue($flashMessage);
+    }
+
+    /**
+     * Writes an error in the sys_log table
+     *
+     * @param string $logMessage Default text that follows the message (in english!).
+     * @param string $logLevel The error level, see LogLevel::* constants
+     */
+    protected function writeLog($logMessage, string $logLevel)
+    {
+        // Avoid ConnectionPool usage prior boot completion (see #96291).
+        if (!GeneralUtility::getContainer()->get('boot.state')->complete) {
+            if ($this->logger) {
+                // Log via debug(), the original message has already been logged with the original serverity in handleError().
+                // This log entry is targeted for users that try to debug why a log record is missing in sys_log
+                // while it has been logged to the logging framework.
+                $this->logger->debug(
+                    'An error could not be logged to database as it appeared during early bootstrap (TCA or ext_localconf.php loading).',
+                    ['original_message' => $logMessage, 'original_loglevel' => $logLevel]
+                );
+            }
+            return;
+        }
+        $connection = GeneralUtility::makeInstance(ConnectionPool::class)
+            ->getConnectionForTable('sys_log');
+        if ($connection->isConnected()) {
+            $userId = 0;
+            $workspace = 0;
+            $data = [];
+            $backendUser = $this->getBackendUser();
+            if (is_object($backendUser)) {
+                if (isset($backendUser->user['uid'])) {
+                    $userId = $backendUser->user['uid'];
+                }
+                $workspace = $backendUser->workspace;
+                if ($backUserId = $backendUser->getOriginalUserIdWhenInSwitchUserMode()) {
+                    $data['originalUser'] = $backUserId;
+                }
+            }
+
+            $connection->insert(
+                'sys_log',
+                [
+                    'userid' => $userId,
+                    'type' => SystemLogType::ERROR,
+                    'channel' => SystemLogType::toChannel(SystemLogType::ERROR),
+                    'action' => SystemLogGenericAction::UNDEFINED,
+                    'error' => SystemLogErrorClassification::SYSTEM_ERROR,
+                    'level' => $logLevel,
+                    'details' => str_replace('%', '%%', $logMessage),
+                    'log_data' => empty($data) ? '' : json_encode($data),
+                    'IP' => NormalizedParams::createFromServerParams($_SERVER)->getRemoteAddress(),
+                    'tstamp' => $GLOBALS['EXEC_TIME'],
+                    'workspace' => $workspace,
+                ]
+            );
+        }
+    }
+
+    protected function getFormattedLogMessage(string $message): string
+    {
+        // String 'FE' if in FrontendApplication, else 'BE' (also in CLI without request object)
+        $applicationType = ($GLOBALS['TYPO3_REQUEST'] ?? null) instanceof ServerRequestInterface
+        && ApplicationType::fromRequest($GLOBALS['TYPO3_REQUEST'])->isFrontend() ? 'FE' : 'BE';
+        $logPrefix = 'Core: Error handler (' . $applicationType . ')';
+        return $logPrefix . ': ' . $message;
+    }
+
+    protected function getTimeTracker(): TimeTracker
+    {
+        return GeneralUtility::makeInstance(TimeTracker::class);
+    }
+
+    protected function getBackendUser(): ?BackendUserAuthentication
+    {
+        return $GLOBALS['BE_USER'] ?? null;
+    }
+}

Classes/Error/ErrorHandlerInterface.php

@@ -0,0 +1,61 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error;
+
+/**
+ * Error handler interface for TYPO3
+ *
+ * This file is a backport from TYPO3 Flow
+ */
+interface ErrorHandlerInterface
+{
+    // Constants to make the implications of the PHP error handling API a bit more obvious.
+    public const ERROR_HANDLED = true;
+    public const PROPAGATE_ERROR = false;
+
+    /**
+     * Registers this class as default error handler
+     *
+     * If dependencies need to be added using injector methods, the error handler may
+     * also be registered later on, within the optional registerErrorHandler() method.
+     *
+     * @param int $errorHandlerErrors The integer representing the E_* error level which should be
+     */
+    public function __construct($errorHandlerErrors);
+
+    /**
+     * Defines which error levels should result in an exception thrown.
+     *
+     * @param int $exceptionalErrors The integer representing the E_* error level to handle as exceptions
+     */
+    public function setExceptionalErrors($exceptionalErrors);
+
+    /**
+     * Handles an error.
+     * If the error is registered as exceptionalError it will by converted into an exception, to be handled
+     * by the configured exceptionhandler. Additionally the error message is written to the configured logs.
+     * If application is backend, the error message is also added to the flashMessageQueue, in frontend the
+     * error message is displayed in the admin panel (as TsLog message).
+     *
+     * @param int $errorLevel The error level - one of the E_* constants
+     * @param string $errorMessage The error message
+     * @param string $errorFile Name of the file the error occurred in
+     * @param int $errorLine Line number where the error occurred
+     * @return bool
+     * @throws \TYPO3\CMS\Core\Error\Exception with the data passed to this method if the error is registered as exceptionalError
+     */
+    public function handleError($errorLevel, $errorMessage, $errorFile, $errorLine);
+}

Classes/Error/Exception.php

@@ -0,0 +1,21 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error;
+
+/**
+ * An exception which represents a PHP error.
+ */
+class Exception extends \TYPO3\CMS\Core\Exception {}

Classes/Error/ExceptionHandlerInterface.php

@@ -0,0 +1,50 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error;
+
+/**
+ * Contract for an exception handler
+ *
+ * This file is a backport from TYPO3 Flow
+ */
+interface ExceptionHandlerInterface
+{
+    /**
+     * Constructs this exception handler - registers itself as the default exception handler.
+     */
+    public function __construct();
+
+    /**
+     * Handles the given exception
+     *
+     * @param \Throwable $exception The throwable object.
+     */
+    public function handleException(\Throwable $exception);
+
+    /**
+     * Formats and echoes the exception as XHTML.
+     *
+     * @param \Throwable $exception The throwable object.
+     */
+    public function echoExceptionWeb(\Throwable $exception);
+
+    /**
+     * Formats and echoes the exception for the command line
+     *
+     * @param \Throwable $exception The throwable object.
+     */
+    public function echoExceptionCLI(\Throwable $exception);
+}

Classes/Error/Http/AbstractClientErrorException.php

@@ -0,0 +1,21 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\Http;
+
+/**
+ * HTTP Client Error Exception (Error 4xx)
+ */
+abstract class AbstractClientErrorException extends StatusException {}

Classes/Error/Http/AbstractServerErrorException.php

@@ -0,0 +1,21 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\Http;
+
+/**
+ * HTTP Server Error Exception (Error 5xx)
+ */
+abstract class AbstractServerErrorException extends StatusException {}

Classes/Error/Http/BadRequestException.php

@@ -0,0 +1,53 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\Http;
+
+use TYPO3\CMS\Core\Utility\HttpUtility;
+
+/**
+ * Exception for Error 400 - Bad Request
+ */
+class BadRequestException extends AbstractClientErrorException
+{
+    /**
+     * @var array HTTP Status Header lines
+     */
+    protected $statusHeaders = [HttpUtility::HTTP_STATUS_400];
+
+    /**
+     * @var string Title of the message
+     */
+    protected $title = 'Bad Request (400)';
+
+    /**
+     * @var string Error Message
+     */
+    protected $message = 'The request cannot be fulfilled due to bad syntax.';
+
+    /**
+     * Constructor for this Status Exception
+     *
+     * @param string $message Error Message
+     * @param int $code Exception Code
+     */
+    public function __construct($message = null, $code = 0)
+    {
+        if (!empty($message)) {
+            $this->message = $message;
+        }
+        parent::__construct($this->statusHeaders, $this->message, $this->title, $code);
+    }
+}

Classes/Error/Http/ForbiddenException.php

@@ -0,0 +1,53 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\Http;
+
+use TYPO3\CMS\Core\Utility\HttpUtility;
+
+/**
+ * Exception for Error 403 - Forbidden
+ */
+class ForbiddenException extends AbstractClientErrorException
+{
+    /**
+     * @var array HTTP Status Header lines
+     */
+    protected $statusHeaders = [HttpUtility::HTTP_STATUS_403];
+
+    /**
+     * @var string Title of the message
+     */
+    protected $title = 'Forbidden (403)';
+
+    /**
+     * @var string Error Message
+     */
+    protected $message = 'You are not allowed to access this page.';
+
+    /**
+     * Constructor for this Status Exception
+     *
+     * @param string $message Error Message
+     * @param int $code Exception Code
+     */
+    public function __construct($message = null, $code = 0)
+    {
+        if (!empty($message)) {
+            $this->message = $message;
+        }
+        parent::__construct($this->statusHeaders, $this->message, $this->title, $code);
+    }
+}

Classes/Error/Http/InternalServerErrorException.php

@@ -0,0 +1,53 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\Http;
+
+use TYPO3\CMS\Core\Utility\HttpUtility;
+
+/**
+ * Exception for Error 500 - Internal Server Error
+ */
+class InternalServerErrorException extends AbstractServerErrorException
+{
+    /**
+     * @var array HTTP Status Header lines
+     */
+    protected $statusHeaders = [HttpUtility::HTTP_STATUS_500];
+
+    /**
+     * @var string Title of the message
+     */
+    protected $title = 'Internal Server Error (500)';
+
+    /**
+     * @var string Error Message
+     */
+    protected $message = 'This page is currently not available due to server errors.';
+
+    /**
+     * Constructor for this Status Exception
+     *
+     * @param string $message Error Message
+     * @param int $code Exception Code
+     */
+    public function __construct($message = null, $code = 0)
+    {
+        if (!empty($message)) {
+            $this->message = $message;
+        }
+        parent::__construct($this->statusHeaders, $this->message, $this->title, $code);
+    }
+}

Classes/Error/Http/LinkedPageNotResolvableException.php

@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\Http;
+
+/**
+ * Excepts if typolink could not be resolved for link pages.
+ */
+class LinkedPageNotResolvableException extends PageNotFoundException {}

Classes/Error/Http/PageNotFoundException.php

@@ -0,0 +1,53 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\Http;
+
+use TYPO3\CMS\Core\Utility\HttpUtility;
+
+/**
+ * Exception for Error 404 - Page Not Found
+ */
+class PageNotFoundException extends AbstractClientErrorException
+{
+    /**
+     * @var array HTTP Status Header lines
+     */
+    protected $statusHeaders = [HttpUtility::HTTP_STATUS_404];
+
+    /**
+     * @var string Title of the message
+     */
+    protected $title = 'Page Not Found (404)';
+
+    /**
+     * @var string Error Message
+     */
+    protected $message = 'The page you tried to access was not found.';
+
+    /**
+     * Constructor for this Status Exception
+     *
+     * @param string $message Error Message
+     * @param int $code Exception Code
+     */
+    public function __construct($message = null, $code = 0)
+    {
+        if (!empty($message)) {
+            $this->message = $message;
+        }
+        parent::__construct($this->statusHeaders, $this->message, $this->title, $code);
+    }
+}

Classes/Error/Http/ServiceUnavailableException.php

@@ -0,0 +1,53 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\Http;
+
+use TYPO3\CMS\Core\Utility\HttpUtility;
+
+/**
+ * Exception for Error 503 - Service Unavailable
+ */
+class ServiceUnavailableException extends AbstractServerErrorException
+{
+    /**
+     * @var array HTTP Status Header lines
+     */
+    protected $statusHeaders = [HttpUtility::HTTP_STATUS_503];
+
+    /**
+     * @var string Title of the message
+     */
+    protected $title = 'Service Unavailable (503)';
+
+    /**
+     * @var string Error Message
+     */
+    protected $message = 'This page is currently not available.';
+
+    /**
+     * Constructor for this Status Exception
+     *
+     * @param string $message Error Message
+     * @param int $code Exception Code
+     */
+    public function __construct($message = null, $code = 0)
+    {
+        if (!empty($message)) {
+            $this->message = $message;
+        }
+        parent::__construct($this->statusHeaders, $this->message, $this->title, $code);
+    }
+}

Classes/Error/Http/ShortcutTargetPageNotFoundException.php

@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\Http;
+
+/**
+ * Exception when a shortcut target page could not be resolved
+ */
+class ShortcutTargetPageNotFoundException extends PageNotFoundException {}

Classes/Error/Http/StatusException.php

@@ -0,0 +1,85 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\Http;
+
+use TYPO3\CMS\Core\Error\Exception;
+
+/**
+ * HTTP Status Exception
+ *
+ * @todo: Rename to AbstractStatusException and declare abstract
+ */
+class StatusException extends Exception
+{
+    /**
+     * @var array HTTP Status Header lines
+     */
+    protected $statusHeaders;
+
+    /**
+     * @var string Title of the message
+     */
+    protected $title = 'Oops, an error occurred!';
+
+    /**
+     * Constructor for this Status Exception
+     *
+     * @param string|array $statusHeaders HTTP Status header line(s)
+     * @param string $title Title of the error message
+     * @param string $message Error Message
+     * @param int $code Exception Code
+     */
+    public function __construct($statusHeaders, $message, $title = '', $code = 0)
+    {
+        if (is_array($statusHeaders)) {
+            $this->statusHeaders = $statusHeaders;
+        } else {
+            $this->statusHeaders = [$statusHeaders];
+        }
+        $this->title = $title ?: $this->title;
+        parent::__construct($message, $code);
+    }
+
+    /**
+     * Setter for the title.
+     *
+     * @param string $title
+     */
+    public function setTitle($title)
+    {
+        $this->title = $title;
+    }
+
+    /**
+     * Getter for the title.
+     *
+     * @return string
+     */
+    public function getTitle()
+    {
+        return $this->title;
+    }
+
+    /**
+     * Getter for the Status Header.
+     *
+     * @return array
+     */
+    public function getStatusHeaders()
+    {
+        return $this->statusHeaders;
+    }
+}

Classes/Error/Http/UnauthorizedException.php

@@ -0,0 +1,53 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\Http;
+
+use TYPO3\CMS\Core\Utility\HttpUtility;
+
+/**
+ * Exception for Error 401 - Unauthorized
+ */
+class UnauthorizedException extends AbstractClientErrorException
+{
+    /**
+     * @var array HTTP Status Header lines
+     */
+    protected $statusHeaders = [HttpUtility::HTTP_STATUS_401];
+
+    /**
+     * @var string Title of the message
+     */
+    protected $title = 'Unauthorized (401)';
+
+    /**
+     * @var string Error Message
+     */
+    protected $message = 'Accessing this page requires authorization.';
+
+    /**
+     * Constructor for this Status Exception
+     *
+     * @param string $message Error Message
+     * @param int $code Exception Code
+     */
+    public function __construct($message = null, $code = 0)
+    {
+        if (!empty($message)) {
+            $this->message = $message;
+        }
+        parent::__construct($this->statusHeaders, $this->message, $this->title, $code);
+    }
+}

Classes/Error/PageErrorHandler/FluidPageErrorHandler.php

@@ -0,0 +1,80 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\PageErrorHandler;
+
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use TYPO3\CMS\Core\Http\HtmlResponse;
+use TYPO3\CMS\Core\Utility\GeneralUtility;
+use TYPO3\CMS\Core\View\ViewFactoryData;
+use TYPO3\CMS\Core\View\ViewFactoryInterface;
+
+/**
+ * An error handler that renders a fluid template.
+ * This is typically configured via the "Sites configuration" module in the backend.
+ */
+class FluidPageErrorHandler implements PageErrorHandlerInterface
+{
+    /**
+     * @todo: Change this "API" to not pollute __construct() anymore
+     */
+    public function __construct(
+        protected int $statusCode,
+        protected array $configuration
+    ) {}
+
+    public function handlePageError(ServerRequestInterface $request, string $message, array $reasons = []): ResponseInterface
+    {
+        $configuration = $this->configuration;
+        $templateRootPaths = null;
+        if (is_string($configuration['errorFluidTemplatesRootPath'] ?? false) && $configuration['errorFluidTemplatesRootPath'] !== '') {
+            $templateRootPaths = [$configuration['errorFluidTemplatesRootPath']];
+        }
+        $layoutRootPaths = null;
+        if (is_string($configuration['errorFluidLayoutsRootPath'] ?? false) && $configuration['errorFluidLayoutsRootPath'] !== '') {
+            $layoutRootPaths = [$configuration['errorFluidLayoutsRootPath']];
+        }
+        $partialRootPaths = null;
+        if (is_string($configuration['errorFluidPartialsRootPath'] ?? false) && $configuration['errorFluidPartialsRootPath'] !== '') {
+            $partialRootPaths = [$configuration['errorFluidPartialsRootPath']];
+        }
+        $templatePathAndFilename = null;
+        if (is_string($configuration['errorFluidTemplate'] ?? false) && $configuration['errorFluidTemplate'] !== '') {
+            $templatePathAndFilename = GeneralUtility::getFileAbsFileName($configuration['errorFluidTemplate']);
+        }
+        if ($templatePathAndFilename === null || !is_file($templatePathAndFilename)) {
+            throw new \RuntimeException('FluidPageErrorHandler: Configured Fluid template file not found.', 1764510148);
+        }
+
+        $viewFactoryDate = new ViewFactoryData(
+            templateRootPaths: $templateRootPaths,
+            partialRootPaths: $partialRootPaths,
+            layoutRootPaths: $layoutRootPaths,
+            templatePathAndFilename: $templatePathAndFilename,
+            request: $request,
+        );
+        $viewFactory = GeneralUtility::makeInstance(ViewFactoryInterface::class);
+        $view = $viewFactory->create($viewFactoryDate);
+        $view->assignMultiple([
+            'request' => $request,
+            'message' => $message,
+            'reasons' => $reasons,
+        ]);
+        return new HtmlResponse($view->render(), $this->statusCode);
+    }
+}

Classes/Error/PageErrorHandler/InvalidPageErrorHandlerException.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\PageErrorHandler;
+
+use TYPO3\CMS\Core\Error\Exception;
+
+/**
+ * Is typically used, when a site configuration has a page-error handler configured but this does not implement
+ * the PageErrorHandlerInterface
+ */
+class InvalidPageErrorHandlerException extends Exception {}

Classes/Error/PageErrorHandler/PageContentErrorHandler.php

@@ -0,0 +1,241 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\PageErrorHandler;
+
+use GuzzleHttp\Exception\GuzzleException;
+use Psr\Http\Message\RequestFactoryInterface;
+use Psr\Http\Message\ResponseFactoryInterface;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use TYPO3\CMS\Core\Exception\SiteNotFoundException;
+use TYPO3\CMS\Core\Http\Client\GuzzleClientFactory;
+use TYPO3\CMS\Core\Http\HtmlResponse;
+use TYPO3\CMS\Core\Http\Uri;
+use TYPO3\CMS\Core\LinkHandling\LinkService;
+use TYPO3\CMS\Core\Routing\InvalidRouteArgumentsException;
+use TYPO3\CMS\Core\Site\Entity\Site;
+use TYPO3\CMS\Core\Site\Entity\SiteLanguage;
+use TYPO3\CMS\Core\Site\SiteFinder;
+use TYPO3\CMS\Core\Utility\GeneralUtility;
+use TYPO3\CMS\Frontend\Http\Application;
+
+/**
+ * Renders the content of a page to be displayed (also in relation to language etc)
+ * This is typically configured via the "Sites configuration" module in the backend.
+ */
+class PageContentErrorHandler implements PageErrorHandlerInterface
+{
+    protected int $statusCode;
+    protected array $errorHandlerConfiguration;
+    protected int $pageUid = 0;
+    protected Application $application;
+    protected ResponseFactoryInterface $responseFactory;
+    protected SiteFinder $siteFinder;
+    protected LinkService $link;
+    protected RequestFactoryInterface $requestFactory;
+    protected GuzzleClientFactory $guzzleClientFactory;
+
+    /**
+     * PageContentErrorHandler constructor.
+     * @throws \InvalidArgumentException
+     */
+    public function __construct(int $statusCode, array $configuration)
+    {
+        $this->statusCode = $statusCode;
+        if (empty($configuration['errorContentSource'])) {
+            throw new \InvalidArgumentException('PageContentErrorHandler needs to have a proper link set.', 1522826413);
+        }
+        $this->errorHandlerConfiguration = $configuration;
+
+        // @todo Convert this to DI once this class can be injected properly.
+        $container = GeneralUtility::getContainer();
+        $this->application = $container->get(Application::class);
+        $this->responseFactory = $container->get(ResponseFactoryInterface::class);
+        $this->siteFinder = GeneralUtility::makeInstance(SiteFinder::class);
+        $this->link = $container->get(LinkService::class);
+        $this->requestFactory = $container->get(RequestFactoryInterface::class);
+        $this->guzzleClientFactory = $container->get(GuzzleClientFactory::class);
+    }
+
+    public function handlePageError(ServerRequestInterface $request, string $message, array $reasons = []): ResponseInterface
+    {
+        try {
+            $urlParams = $this->link->resolve($this->errorHandlerConfiguration['errorContentSource']);
+            $urlParams['pageuid'] = (int)($urlParams['pageuid'] ?? 0);
+            $urlType = $urlParams['type'] ?? LinkService::TYPE_UNKNOWN;
+            $resolvedUrl = $this->resolveUrl($request, $urlParams);
+
+            // avoid denial-of-service amplification scenario
+            if ($resolvedUrl === (string)$request->getUri()) {
+                return new HtmlResponse(
+                    'The error page could not be resolved, as the error page itself is not accessible',
+                    $this->statusCode
+                );
+            }
+            // External URL most likely pointing to additional hosts or pages not contained in the current instance,
+            // and using internal sub requests would never receive a valid page. Send an external request instead.
+            if ($urlType === LinkService::TYPE_URL) {
+                return $this->sendExternalRequest($resolvedUrl, $request);
+            }
+            // Create a sub-request and do not take any special query parameters into account
+            $subRequest = $request->withQueryParams([])->withUri(new Uri($resolvedUrl))->withMethod('GET');
+            $subResponse = $this->sendSubRequest($subRequest, $urlParams['pageuid'], $request);
+
+            if ($subResponse->getStatusCode() >= 300) {
+                throw new \RuntimeException(sprintf('Error handler could not fetch error page "%s", status code: %s', $resolvedUrl, $subResponse->getStatusCode()), 1544172839);
+            }
+
+            $response = $this->responseFactory->createResponse($this->statusCode)
+                ->withHeader('content-type', $subResponse->getHeader('content-type'))
+                ->withBody($subResponse->getBody());
+
+            foreach (['Content-Security-Policy', 'Content-Security-Policy-Report-Only'] as $header) {
+                if ($subResponse->hasHeader($header)) {
+                    $response = $response->withHeader($header, $subResponse->getHeader($header));
+                }
+            }
+            return $response;
+        } catch (InvalidRouteArgumentsException|SiteNotFoundException $e) {
+            return new HtmlResponse('Invalid error handler configuration: ' . $this->errorHandlerConfiguration['errorContentSource']);
+        }
+    }
+
+    /**
+     * Sends an in-process subrequest.
+     *
+     * The $pageId is used to ensure the correct site is accessed.
+     */
+    protected function sendSubRequest(ServerRequestInterface $request, int $pageId, ServerRequestInterface $originalRequest): ResponseInterface
+    {
+        $site = $request->getAttribute('site');
+        if (!$site instanceof Site) {
+            $site = $this->siteFinder->getSiteByPageId($pageId);
+            $request = $request->withAttribute('site', $site);
+        }
+
+        $request = $request->withAttribute('originalRequest', $originalRequest);
+
+        return $this->application->handle($request);
+    }
+
+    /**
+     * Sends an external request to fetch the error page from a remote resource.
+     *
+     * A custom header is added and checked to mitigate request loops, which
+     * indicates additional configuration error in the error handler config.
+     */
+    protected function sendExternalRequest(string $url, ServerRequestInterface $originalRequest): ResponseInterface
+    {
+        if ($originalRequest->hasHeader('Requested-By')
+            && in_array('TYPO3 Error Handler', $originalRequest->getHeader('Requested-By'), true)
+        ) {
+            // If the header is set here, it is a recursive call within the same instance where an
+            // outer error handler called a page that results in another error handler call. To break
+            // the loop, we except here.
+            return new HtmlResponse(
+                'The error page could not be resolved, the error page itself is not accessible',
+                $this->statusCode
+            );
+        }
+        try {
+            $request = $this->requestFactory->createRequest('GET', $url)
+                ->withHeader('Content-Type', 'text/html')
+                ->withHeader('Requested-By', 'TYPO3 Error Handler');
+            $response = $this->guzzleClientFactory->getClient()->send($request);
+            // In case global guzzle configuration has been changed to not throw an exception
+            // for error status codes, the response status code is checked here.
+            if ($response->getStatusCode() >= 300) {
+                return new HtmlResponse(
+                    'The error page could not be resolved, as the error page itself is not accessible',
+                    $this->statusCode
+                );
+            }
+            return $this->responseFactory
+                ->createResponse($this->statusCode)
+                ->withHeader('Content-Type', $response->getHeader('Content-Type'))
+                ->withBody($response->getBody());
+        } catch (GuzzleException) {
+            return new HtmlResponse(
+                'The error page could not be resolved, the error page itself is not accessible',
+                $this->statusCode
+            );
+        }
+    }
+
+    /**
+     * Resolve the URL (currently only page and external URL are supported)
+     */
+    protected function resolveUrl(ServerRequestInterface $request, array $urlParams): string
+    {
+        if (!in_array($urlParams['type'], ['page', 'url'])) {
+            throw new \InvalidArgumentException('PageContentErrorHandler can only handle TYPO3 URLs of types "page" or "url"', 1522826609);
+        }
+        if ($urlParams['type'] === 'url') {
+            return $urlParams['url'];
+        }
+
+        // Get the site related to the configured error page
+        $site = $this->siteFinder->getSiteByPageId($urlParams['pageuid']);
+        $requestLanguage = $request->getAttribute('language');
+        // Try to get the current request language from the site that was found above
+        if ($requestLanguage instanceof SiteLanguage && $requestLanguage->isEnabled()) {
+            try {
+                $language = $site->getLanguageById($requestLanguage->getLanguageId());
+            } catch (\InvalidArgumentException $e) {
+                $language = $site->getDefaultLanguage();
+            }
+        } else {
+            $language = $site->getDefaultLanguage();
+        }
+
+        // Requested language or default language is disabled in current site => Fetch first "enabled" language
+        if (!$language->isEnabled()) {
+            $enabledLanguages = $site->getLanguages();
+            if ($enabledLanguages === []) {
+                throw new \RuntimeException(
+                    'Site ' . $site->getIdentifier() . ' does not define any enabled language.',
+                    1674487171
+                );
+            }
+            $language = reset($enabledLanguages);
+        }
+
+        // Build Url
+        $uri = $site->getRouter()->generateUri(
+            (int)$urlParams['pageuid'],
+            ['_language' => $language]
+        );
+
+        // Fallback to the current URL if the site is not having a proper scheme and host
+        $currentUri = $request->getUri();
+        if (empty($uri->getScheme())) {
+            $uri = $uri->withScheme($currentUri->getScheme());
+        }
+        if (empty($uri->getUserInfo())) {
+            $uri = $uri->withUserInfo($currentUri->getUserInfo());
+        }
+        if (empty($uri->getHost())) {
+            $uri = $uri->withHost($currentUri->getHost());
+        }
+        if ($uri->getPort() === null) {
+            $uri = $uri->withPort($currentUri->getPort());
+        }
+
+        return (string)$uri;
+    }
+}

Classes/Error/PageErrorHandler/PageErrorHandlerInterface.php

@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\PageErrorHandler;
+
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+
+/**
+ * Page error handler interface, used to jump in for Frontend-related calls
+ *
+ * Needs to be implemented by all custom PHP-related Page Error Handlers.
+ */
+interface PageErrorHandlerInterface
+{
+    /**
+     * @param array<string, mixed> $reasons
+     */
+    public function handlePageError(ServerRequestInterface $request, string $message, array $reasons = []): ResponseInterface;
+}

Classes/Error/PageErrorHandler/PageErrorHandlerNotConfiguredException.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\PageErrorHandler;
+
+use TYPO3\CMS\Core\Error\Exception;
+
+/**
+ * Is typically used, when a site configuration has no page-error handler configured
+ * for a specific HTTP Status type that is requested.
+ */
+class PageErrorHandlerNotConfiguredException extends Exception {}

Classes/Error/PageErrorHandler/RedirectLoginErrorHandler.php

@@ -0,0 +1,140 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error\PageErrorHandler;
+
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use TYPO3\CMS\Core\Context\Context;
+use TYPO3\CMS\Core\Controller\ErrorPageController;
+use TYPO3\CMS\Core\Http\HtmlResponse;
+use TYPO3\CMS\Core\Http\RedirectResponse;
+use TYPO3\CMS\Core\LinkHandling\LinkService;
+use TYPO3\CMS\Core\Site\Entity\Site;
+use TYPO3\CMS\Core\Utility\GeneralUtility;
+use TYPO3\CMS\Frontend\Page\PageAccessFailureReasons;
+
+/**
+ * An error handler that redirects to a configured page, where the login process is handled. Passes a configurable
+ * url parameter (`return_url` or `redirect_url`) to the target page.
+ */
+class RedirectLoginErrorHandler implements PageErrorHandlerInterface
+{
+    protected int $loginRedirectPid = 0;
+    protected int $statusCode = 0;
+    protected string $loginRedirectParameter = '';
+    protected Context $context;
+    protected LinkService $linkService;
+
+    public function __construct(int $statusCode, array $configuration)
+    {
+        $this->statusCode = $statusCode;
+        $this->context = GeneralUtility::makeInstance(Context::class);
+        $this->linkService = GeneralUtility::makeInstance(LinkService::class);
+
+        $urlParams = $this->linkService->resolve($configuration['loginRedirectTarget'] ?? '');
+        $this->loginRedirectPid = (int)($urlParams['pageuid'] ?? 0);
+        $this->loginRedirectParameter = $configuration['loginRedirectParameter'] ?? 'return_url';
+    }
+
+    public function handlePageError(
+        ServerRequestInterface $request,
+        string $message,
+        array $reasons = []
+    ): ResponseInterface {
+        $this->checkHandlerConfiguration();
+
+        if ($this->shouldHandleRequest($reasons)) {
+            return $this->handleLoginRedirect($request);
+        }
+
+        // Show general error message with a 403 HTTP statuscode
+        return $this->getGenericAccessDeniedResponse($message);
+    }
+
+    private function getGenericAccessDeniedResponse(string $reason): ResponseInterface
+    {
+        $content = GeneralUtility::makeInstance(ErrorPageController::class)->errorAction(
+            'Page Not Found',
+            'The page did not exist or was inaccessible.' . ($reason ? ' Reason: ' . $reason : ''),
+            0,
+            $this->statusCode,
+        );
+        return new HtmlResponse($content, $this->statusCode);
+    }
+
+    private function handleLoginRedirect(ServerRequestInterface $request): ResponseInterface
+    {
+        if ($this->isLoggedIn()) {
+            return $this->getGenericAccessDeniedResponse(
+                'The requested page was not accessible with the provided credentials'
+            );
+        }
+
+        /** @var Site $site */
+        $site = $request->getAttribute('site');
+        $language = $request->getAttribute('language');
+
+        $loginUrl = $site->getRouter()->generateUri(
+            $this->loginRedirectPid,
+            [
+                '_language' => $language,
+                $this->loginRedirectParameter => (string)$request->getUri(),
+            ]
+        );
+
+        return new RedirectResponse($loginUrl);
+    }
+
+    private function shouldHandleRequest(array $reasons): bool
+    {
+        if (!isset($reasons['code'])) {
+            return false;
+        }
+
+        $accessDeniedReasons = [
+            PageAccessFailureReasons::ACCESS_DENIED_PAGE_NOT_RESOLVED,
+            PageAccessFailureReasons::ACCESS_DENIED_SUBSECTION_NOT_RESOLVED,
+        ];
+        $isAccessDenied = in_array($reasons['code'], $accessDeniedReasons, true);
+
+        return $isAccessDenied || $this->isSimulatedBackendGroup();
+    }
+
+    private function isLoggedIn(): bool
+    {
+        return $this->context->getPropertyFromAspect('frontend.user', 'isLoggedIn') || $this->isSimulatedBackendGroup();
+    }
+
+    protected function isSimulatedBackendGroup(): bool
+    {
+        // look for special "any group"
+        return $this->context->getPropertyFromAspect('backend.user', 'isLoggedIn')
+            && $this->context->getPropertyFromAspect('frontend.user', 'groupIds')[1] === -2;
+    }
+
+    private function checkHandlerConfiguration(): void
+    {
+        if ($this->loginRedirectPid === 0) {
+            throw new \RuntimeException('No loginRedirectTarget configured for LoginRedirect errorhandler', 1700813537);
+        }
+
+        if ($this->statusCode !== 403) {
+            throw new \RuntimeException('Invalid HTTP statuscode ' . $this->statusCode . ' for LoginRedirect errorhandler', 1700813545);
+        }
+    }
+}

Classes/Error/ProductionExceptionHandler.php

@@ -0,0 +1,139 @@
+<?php
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+namespace TYPO3\CMS\Core\Error;
+
+use TYPO3\CMS\Core\Controller\ErrorPageController;
+use TYPO3\CMS\Core\Error\Http\AbstractClientErrorException;
+use TYPO3\CMS\Core\Error\Http\StatusException;
+use TYPO3\CMS\Core\Utility\GeneralUtility;
+
+/**
+ * An exception handler which catches any exception and
+ * renders an error page without backtrace (Web) or a slim
+ * message on CLI.
+ */
+class ProductionExceptionHandler extends AbstractExceptionHandler
+{
+    /**
+     * Default title for error messages
+     *
+     * @var string
+     */
+    protected $defaultTitle = 'Oops, an error occurred!';
+
+    /**
+     * Default message for error messages
+     *
+     * @var string
+     */
+    protected $defaultMessage = '';
+
+    /**
+     * Constructs this exception handler - registers itself as the default exception handler.
+     */
+    public function __construct()
+    {
+        set_exception_handler($this->handleException(...));
+    }
+
+    /**
+     * Echoes an exception for the web.
+     *
+     * @param \Throwable $exception The throwable object.
+     */
+    public function echoExceptionWeb(\Throwable $exception)
+    {
+        $this->sendStatusHeaders($exception);
+        $this->writeLogEntries($exception, self::CONTEXT_WEB);
+        echo GeneralUtility::makeInstance(ErrorPageController::class)->errorAction(
+            $this->getTitle($exception),
+            $this->getMessage($exception),
+            $this->discloseExceptionInformation($exception) ? $exception->getCode() : 0,
+            $this->getHttpStatusCodeFromException($exception)
+        );
+    }
+
+    /**
+     * Echoes an exception for the command line.
+     *
+     * @param \Throwable $exception The throwable object.
+     */
+    public function echoExceptionCLI(\Throwable $exception)
+    {
+        $filePathAndName = $exception->getFile();
+        $exceptionCodeNumber = $exception->getCode() > 0 ? '#' . $exception->getCode() . ': ' : '';
+        $this->writeLogEntries($exception, self::CONTEXT_CLI);
+        echo LF . 'Uncaught TYPO3 Exception ' . $exceptionCodeNumber . $exception->getMessage() . LF;
+        echo 'thrown in file ' . $filePathAndName . LF;
+        echo 'in line ' . $exception->getLine() . LF . LF;
+        die(1);
+    }
+
+    /**
+     * Determines, whether Exception details should be outputted
+     *
+     * @param \Throwable $exception The throwable object.
+     * @return bool
+     */
+    protected function discloseExceptionInformation(\Throwable $exception)
+    {
+        // Allow message to be shown in production mode if the exception is about
+        // trusted host configuration.  By doing so we do not disclose
+        // any valuable information to an attacker but avoid confusions among TYPO3 admins
+        // in production context.
+        if ($exception->getCode() === 1396795884) {
+            return true;
+        }
+        // Show client error messages 40x in every case
+        if ($exception instanceof AbstractClientErrorException) {
+            return true;
+        }
+        // Only show errors if a BE user is authenticated
+        $backendUser = $this->getBackendUser();
+        if ($backendUser === null) {
+            return false;
+        }
+        return ($backendUser->user['uid'] ?? 0) > 0;
+    }
+
+    /**
+     * Returns the title for the error message
+     *
+     * @param \Throwable $exception The throwable object.
+     * @return string
+     */
+    protected function getTitle(\Throwable $exception)
+    {
+        if ($this->discloseExceptionInformation($exception) && $exception instanceof StatusException && $exception->getTitle() !== '') {
+            return $exception->getTitle();
+        }
+        return $this->defaultTitle;
+    }
+
+    /**
+     * Returns the message for the error message
+     *
+     * @param \Throwable $exception The throwable object.
+     * @return string
+     */
+    protected function getMessage(\Throwable $exception)
+    {
+        if ($this->discloseExceptionInformation($exception)) {
+            return $exception->getMessage();
+        }
+        return $this->defaultMessage;
+    }
+}