feat: sender favicon avatars

app/api/favicon/route.ts

@@ -0,0 +1,99 @@
+import { NextRequest, NextResponse } from 'next/server';
+
+// In-memory LRU cache: domain -> { data, contentType, fetchedAt }
+const CACHE_MAX_SIZE = 1000;
+const CACHE_TTL_MS = 14 * 24 * 60 * 60 * 1000; // 2 weeks
+
+interface CacheEntry {
+  data: ArrayBuffer;
+  contentType: string;
+  fetchedAt: number;
+}
+
+const cache = new Map<string, CacheEntry>();
+
+// Strict domain validation to prevent SSRF
+const DOMAIN_RE = /^[a-z0-9]([a-z0-9-]*[a-z0-9])?(\.[a-z0-9]([a-z0-9-]*[a-z0-9])?)+$/i;
+
+function isValidDomain(domain: string): boolean {
+  if (domain.length > 253) return false;
+  if (!DOMAIN_RE.test(domain)) return false;
+  // Block internal/private hostnames
+  const lower = domain.toLowerCase();
+  if (
+    lower === 'localhost' ||
+    lower.endsWith('.local') ||
+    lower.endsWith('.internal') ||
+    lower.endsWith('.arpa')
+  ) {
+    return false;
+  }
+  return true;
+}
+
+function evictOldest() {
+  if (cache.size < CACHE_MAX_SIZE) return;
+  // Evict the oldest entry
+  let oldestKey: string | null = null;
+  let oldestTime = Infinity;
+  for (const [key, entry] of cache) {
+    if (entry.fetchedAt < oldestTime) {
+      oldestTime = entry.fetchedAt;
+      oldestKey = key;
+    }
+  }
+  if (oldestKey) cache.delete(oldestKey);
+}
+
+export async function GET(request: NextRequest) {
+  const domain = request.nextUrl.searchParams.get('domain');
+
+  if (!domain || !isValidDomain(domain)) {
+    return new NextResponse(null, { status: 400 });
+  }
+
+  const normalizedDomain = domain.toLowerCase();
+
+  // Check cache
+  const cached = cache.get(normalizedDomain);
+  if (cached && Date.now() - cached.fetchedAt < CACHE_TTL_MS) {
+    return new NextResponse(cached.data, {
+      headers: {
+        'Content-Type': cached.contentType,
+        'Cache-Control': 'public, max-age=1209600', // 2 weeks
+      },
+    });
+  }
+
+  try {
+    const upstream = await fetch(
+      `https://icons.duckduckgo.com/ip3/${encodeURIComponent(normalizedDomain)}.ico`,
+      { signal: AbortSignal.timeout(5000) }
+    );
+
+    if (!upstream.ok) {
+      return new NextResponse(null, { status: 404 });
+    }
+
+    const contentType = upstream.headers.get('content-type') || 'image/x-icon';
+    const data = await upstream.arrayBuffer();
+
+    // Don't cache empty/tiny responses (likely no real favicon)
+    if (data.byteLength < 10) {
+      return new NextResponse(null, { status: 404 });
+    }
+
+    // Cache the result
+    evictOldest();
+    cache.set(normalizedDomain, { data, contentType, fetchedAt: Date.now() });
+
+    return new NextResponse(data, {
+      headers: {
+        'Content-Type': contentType,
+        'Cache-Control': 'public, max-age=1209600',
+      },
+    });
+  } catch {
+    return new NextResponse(null, { status: 502 });
+  }
+}