Add subdomains finder 🕵️‍♀️

app/lookup/[domain]/subdomains/error.tsx

@@ -0,0 +1,25 @@
+'use client';
+
+import { type FC, useEffect } from 'react';
+
+type SubdomainsErrorProps = {
+  error: Error & { digest?: string };
+  reset: () => void;
+};
+
+const SubdomainsError: FC<SubdomainsErrorProps> = ({ error }) => {
+  useEffect(() => {
+    console.error(error);
+  }, [error]);
+
+  return (
+    <div className="mt-12 flex flex-col items-center gap-2">
+      <h2>Something went wrong!</h2>
+      <p className="mt-2 text-center text-sm text-muted-foreground">
+        Digest: {error.digest}
+      </p>
+    </div>
+  );
+};
+
+export default SubdomainsError;

app/lookup/[domain]/subdomains/loading.tsx

@@ -0,0 +1,9 @@
+import { Spinner } from '@/components/ui/spinner';
+
+const SubdomainsLoading = () => (
+  <div className="flex items-center justify-center">
+    <Spinner className="my-8" />
+  </div>
+);
+
+export default SubdomainsLoading;

app/lookup/[domain]/subdomains/page.tsx

@@ -0,0 +1,126 @@
+import { CheckIcon, XIcon } from 'lucide-react';
+import type { FC } from 'react';
+
+import {
+  Table,
+  TableBody,
+  TableCell,
+  TableHead,
+  TableHeader,
+  TableRow,
+} from '@/components/ui/table';
+
+import DomainLink from '@/components/DomainLink';
+import CloudflareDoHResolver from '@/lib/resolvers/CloudflareDoHResolver';
+
+type CertsData = {
+  issuer_ca_id: number;
+  issuer_name: string;
+  common_name: string;
+  name_value: string;
+  id: number;
+  entry_timestamp: string;
+  not_before: string;
+  not_after: string;
+  serial_number: string;
+}[];
+
+export const runtime = 'edge';
+// crt.sh located in GB, always use LHR1 for lowest latency
+export const preferredRegion = 'lhr1';
+
+const lookupCerts = async (domain: string): Promise<CertsData> => {
+  const response = await fetch(
+    'https://crt.sh?' +
+      new URLSearchParams({
+        Identity: domain,
+        output: 'json',
+      })
+  );
+
+  if (!response.ok) {
+    throw new Error('Failed to fetch certs');
+  }
+
+  return await response.json();
+};
+
+type SubdomainsResultsPageProps = {
+  params: {
+    domain: string;
+  };
+};
+
+const SubdomainsResultsPage: FC<SubdomainsResultsPageProps> = async ({
+  params: { domain },
+}) => {
+  const resolver = new CloudflareDoHResolver();
+
+  const certs = await lookupCerts(domain);
+
+  const issuedCerts = certs.map((cert) => ({
+    date: new Date(cert.entry_timestamp),
+    domains: [cert.common_name, ...cert.name_value.split(/\n/g)],
+  }));
+
+  const uniqueDomains = Array.from(
+    new Set<string>(issuedCerts.flatMap((r) => r.domains))
+  ).filter((d) => d.endsWith(`.${domain}`));
+
+  const results = await Promise.all(
+    uniqueDomains.map(async (domain, i) => {
+      const records = await resolver.resolveAllRecords(domain);
+      const hasRecords = Object.values(records).some((r) => r.length > 0);
+
+      return {
+        domain,
+        firstSeen: issuedCerts
+          .filter((c) => c.domains.includes(domain))
+          .sort((a, b) => a.date.getTime() - b.date.getTime())[0].date,
+        stillExists: hasRecords,
+      };
+    })
+  );
+  const sortedResults = results.sort(
+    (a, b) => b.firstSeen.getTime() - a.firstSeen.getTime()
+  );
+
+  if (!sortedResults.length) {
+    return (
+      <p className="mt-8 text-center text-muted-foreground">
+        Could not find any subdomains for this domain.
+      </p>
+    );
+  }
+
+  return (
+    <Table>
+      <TableHeader>
+        <TableRow className="hover:bg-transparent">
+          <TableHead className="pl-0">Domain Name</TableHead>
+          <TableHead>First seen</TableHead>
+          <TableHead className="pr-0">Still exists</TableHead>
+        </TableRow>
+      </TableHeader>
+      <TableBody>
+        {sortedResults.map((result) => (
+          <TableRow key={result.domain} className="hover:bg-transparent">
+            <TableCell className="pl-0">
+              <DomainLink domain={result.domain} />
+            </TableCell>
+            <TableCell>{result.firstSeen.toISOString()}</TableCell>
+            <TableCell className="pr-0">
+              {result.stillExists ? (
+                <CheckIcon size="1.25rem" />
+              ) : (
+                <XIcon size="1.25rem" />
+              )}
+            </TableCell>
+          </TableRow>
+        ))}
+      </TableBody>
+    </Table>
+  );
+};
+
+export default SubdomainsResultsPage;

components/ResultsTabs.tsx

@@ -54,6 +54,9 @@ const ResultsTabs: FC<ResultsTabsProps> = ({ domain }) => {
   useHotkeys('alt+2', () => router.push(`/lookup/${domain}/map`), [router]);
   useHotkeys('alt+3', () => router.push(`/lookup/${domain}/whois`), [router]);
   useHotkeys('alt+4', () => router.push(`/lookup/${domain}/certs`), [router]);
+  useHotkeys('alt+5', () => router.push(`/lookup/${domain}/subdomains`), [
+    router,
+  ]);
 
   return (
     <div className="group mb-6 mt-6 border-b border-gray-200 text-center text-sm font-medium text-gray-500 dark:border-gray-700 dark:text-gray-400">
@@ -82,6 +85,12 @@ const ResultsTabs: FC<ResultsTabsProps> = ({ domain }) => {
           selected={selectedSegment === 'certs'}
           shortcutNumber={4}
         />
+        <SingleTab
+          label="Subdomains"
+          href={`/lookup/${domain}/subdomains`}
+          selected={selectedSegment === 'subdomains'}
+          shortcutNumber={5}
+        />
       </ul>
     </div>
   );