nonce = $nonce ?: Str::random(24); } /** * Get the nonce value for CSP. */ public function getNonce(): string { return $this->nonce; } /** * Get the CSP headers for the application. */ public function getCspHeader(): string { $headers = [ $this->getFrameAncestors(), $this->getFrameSrc(), $this->getScriptSrc(), $this->getObjectSrc(), $this->getBaseUri(), ]; return implode('; ', array_filter($headers)); } /** * Get the CSP rules for the application for a HTML meta tag. */ public function getCspMetaTagValue(): string { $headers = [ $this->getFrameSrc(), $this->getScriptSrc(), $this->getObjectSrc(), $this->getBaseUri(), ]; return implode('; ', array_filter($headers)); } /** * Check if the user has configured some allowed iframe hosts. */ public function allowedIFrameHostsConfigured(): bool { return count($this->getAllowedIframeHosts()) > 0; } /** * Create CSP 'script-src' rule to restrict the forms of script that can run on the page. */ protected function getScriptSrc(): string { if (config('app.allow_content_scripts')) { return ''; } $parts = [ 'http:', 'https:', '\'nonce-' . $this->nonce . '\'', '\'strict-dynamic\'', ]; return 'script-src ' . implode(' ', $parts); } /** * Create CSP "frame-ancestors" rule to restrict the hosts that BookStack can be iframed within. */ protected function getFrameAncestors(): string { $iframeHosts = $this->getAllowedIframeHosts(); array_unshift($iframeHosts, "'self'"); return 'frame-ancestors ' . implode(' ', $iframeHosts); } /** * Creates CSP "frame-src" rule to restrict what hosts/sources can be loaded * within iframes to provide an allow-list-style approach to iframe content. */ protected function getFrameSrc(): string { $iframeHosts = $this->getAllowedIframeSources(); array_unshift($iframeHosts, "'self'"); return 'frame-src ' . implode(' ', $iframeHosts); } /** * Creates CSP 'object-src' rule to restrict the types of dynamic content * that can be embedded on the page. */ protected function getObjectSrc(): string { if (config('app.allow_content_scripts')) { return ''; } return "object-src 'self'"; } /** * Creates CSP 'base-uri' rule to restrict what base tags can be set on * the page to prevent manipulation of relative links. */ protected function getBaseUri(): string { return "base-uri 'self'"; } protected function getAllowedIframeHosts(): array { $hosts = config('app.iframe_hosts', ''); return array_filter(explode(' ', $hosts)); } protected function getAllowedIframeSources(): array { $sources = config('app.iframe_sources', ''); $hosts = array_filter(explode(' ', $sources)); // Extract drawing service url to allow embedding if active $drawioConfigValue = config('services.drawio'); if ($drawioConfigValue) { $drawioSource = is_string($drawioConfigValue) ? $drawioConfigValue : 'https://embed.diagrams.net/'; $drawioSourceParsed = parse_url($drawioSource); $drawioHost = $drawioSourceParsed['scheme'] . '://' . $drawioSourceParsed['host']; $hosts[] = $drawioHost; } return $hosts; } }