fix(previews): no genuine preview card for a site a deceptive link only pretends to be (#286)

Previews are built from the plain body, clicks follow formatted_body's
hrefs, and a sender controls both: text "https://paypal.com" linked to
evil.example showed a real PayPal card. Drop body URLs whose site is
only claimed by the visible text of a mismatched link (linkSafety).

Fixes #286

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/components/CallEmbedProvider.tsx

@@ -89,9 +89,6 @@ import { zIndices } from '../styles/zIndex';
 
 const PIP_MIN_W = 200;
 const PIP_MIN_H = 112;
-/** [Gitea #323] Minimised PiP bar size. */
-const PIP_MINI_W = 220;
-const PIP_MINI_H = 40;
 
 type Corner = 'se' | 'sw' | 'ne' | 'nw';
 
@@ -984,28 +981,6 @@ export function CallEmbedProvider({ children }: CallEmbedProviderProps) {
   );
 
   const [pipIsFullscreen, setPipIsFullscreen] = useState(false);
-  // [Gitea #323] Minimised PiP: a small draggable bar (room name + expand)
-  // instead of the video. Remembered; phones start minimised.
-  const [pipMinimized, setPipMinimized] = useState<boolean>(() => {
-    try {
-      const v = localStorage.getItem('pip-minimized');
-      if (v !== null) return v === '1';
-    } catch {
-      /* storage unavailable */
-    }
-    return window.innerWidth < 600;
-  });
-  const pipFullSizeRef = React.useRef({ width: 280, height: 158 });
-  const togglePipMinimized = useCallback(() => {
-    setPipMinimized((m) => {
-      try {
-        localStorage.setItem('pip-minimized', m ? '0' : '1');
-      } catch {
-        /* storage unavailable */
-      }
-      return !m;
-    });
-  }, []);
   useEffect(() => {
     const onFsChange = () => setPipIsFullscreen(!!document.fullscreenElement);
     document.addEventListener('fullscreenchange', onFsChange);
@@ -1103,26 +1078,6 @@ export function CallEmbedProvider({ children }: CallEmbedProviderProps) {
     }
   }, [pipMode, callVisible]);
 
-  // [Gitea #323] Apply the minimised / full PiP size (after the entry effect
-  // below has positioned and sized it). Keeps the bar on screen.
-  React.useEffect(() => {
-    const el = callEmbedRef.current;
-    if (!el || !pipMode) return;
-    if (pipMinimized) {
-      if (el.offsetHeight > PIP_MINI_H) {
-        pipFullSizeRef.current = { width: el.offsetWidth, height: el.offsetHeight };
-      }
-      el.style.width = `${PIP_MINI_W}px`;
-      el.style.height = `${PIP_MINI_H}px`;
-    } else {
-      el.style.width = `${pipFullSizeRef.current.width}px`;
-      el.style.height = `${pipFullSizeRef.current.height}px`;
-    }
-    const rect = el.getBoundingClientRect();
-    el.style.left = `${Math.max(0, Math.min(rect.left, window.innerWidth - el.offsetWidth))}px`;
-    el.style.top = `${Math.max(0, Math.min(rect.top, window.innerHeight - el.offsetHeight))}px`;
-  }, [pipMode, pipMinimized, callEmbedRef]);
-
   React.useEffect(() => {
     if (!pipMode) return;
     const onPipWindowResize = (): void => {
@@ -1441,50 +1396,19 @@ export function CallEmbedProvider({ children }: CallEmbedProviderProps) {
                 position: 'absolute',
                 inset: 0,
                 zIndex: 1,
-                // Minimised: cover the frame so only the bar shows.
-                background: pipMinimized ? color.Surface.Container : 'transparent',
+                background: 'transparent',
                 cursor: 'grab',
                 // [Gitea #43] The call's "Share your screen?" prompt is drawn
                 // inside the frame: let the click reach its Share button.
                 pointerEvents: pipPromptOpen ? 'none' : undefined,
                 display: 'flex',
+                alignItems: 'flex-start',
                 justifyContent: 'flex-end',
-                alignItems: pipMinimized ? 'center' : 'flex-start',
                 padding: '6px',
               }}
             >
-              <div
-                style={{
-                  display: 'flex',
-                  gap: config.space.S100,
-                  alignItems: 'center',
-                  ...(pipMinimized ? { width: '100%' } : {}),
-                }}
-              >
-                {/* Leftmost: the top-right corner is a resize handle. */}
-                <IconButton
-                  type="button"
-                  size="300"
-                  radii="300"
-                  variant="Surface"
-                  fill="None"
-                  aria-label={pipMinimized ? 'Expand call' : 'Minimise call'}
-                  aria-pressed={pipMinimized}
-                  onClick={(e) => {
-                    e.stopPropagation();
-                    togglePipMinimized();
-                  }}
-                  onMouseDown={(e) => e.stopPropagation()}
-                  onTouchStart={(e) => e.stopPropagation()}
-                  style={{
-                    background: 'rgba(0,0,0,0.65)',
-                    backdropFilter: 'blur(4px)',
-                    color: '#fff',
-                  }}
-                >
-                  <Icon size="100" src={pipMinimized ? Icons.ChevronTop : Icons.Minus} />
-                </IconButton>
-                {!pipMinimized && document.fullscreenEnabled && (
+              <div style={{ display: 'flex', gap: config.space.S100, alignItems: 'center' }}>
+                {document.fullscreenEnabled && (
                   <IconButton
                     type="button"
                     size="300"
@@ -1516,23 +1440,14 @@ export function CallEmbedProvider({ children }: CallEmbedProviderProps) {
                     fontSize: '11px',
                     fontWeight: 600,
                     pointerEvents: 'none',
-                    ...(pipMinimized
-                      ? {
-                          flexGrow: 1,
-                          minWidth: 0,
-                          overflow: 'hidden',
-                          textOverflow: 'ellipsis',
-                          whiteSpace: 'nowrap',
-                        }
-                      : {}),
                   }}
                 >
-                  {pipMinimized ? `↗ ${callEmbed.room.name ?? 'Call'}` : '↗ Return to call'}
+                  ↗ Return to call
                 </div>
               </div>
             </div>
-            {!pipMinimized && <PipMuteOverlay callEmbed={callEmbed} />}
-            {(pipMinimized ? [] : (['se', 'sw', 'ne', 'nw'] as Corner[])).map((corner) => {
+            <PipMuteOverlay callEmbed={callEmbed} />
+            {(['se', 'sw', 'ne', 'nw'] as Corner[]).map((corner) => {
               const s = corner.includes('s');
               const e2 = corner.includes('e');
               const dots = [

src/app/components/message/MsgTypeRenderers.tsx

@@ -40,6 +40,7 @@ import { parseGeoUri, scaleYDimension } from '../../utils/common';
 import { formatAccuracy } from '../../utils/geoShare';
 import { Attachment, AttachmentBox, AttachmentContent, AttachmentHeader } from './attachment';
 import { FileHeader, FileDownloadButton } from './FileHeader';
+import { previewUrlsFor } from '../../utils/linkSafety';
 
 // ≈ 20 lines; in rem so a larger font setting doesn't show fewer lines (Gitea #343).
 const COLLAPSE_MAX_HEIGHT_REM = 20;
@@ -343,7 +344,13 @@ export function MText({
   if (typeof body !== 'string') return <BrokenContent />;
   const trimmedBody = trimReplyFromBody(body);
   const urlsMatch = renderUrlsPreview && trimmedBody.match(URL_REG);
-  const urls = urlsMatch ? [...new Set(urlsMatch)] : undefined;
+  // [Gitea #286] no genuine card for a site a deceptive link only pretends to be
+  const urls = urlsMatch
+    ? previewUrlsFor(
+        [...new Set(urlsMatch)],
+        typeof customBody === 'string' ? customBody : undefined,
+      )
+    : undefined;
 
   return (
     <>
@@ -401,7 +408,13 @@ export function MEmote({
   if (typeof body !== 'string') return <BrokenContent />;
   const trimmedBody = trimReplyFromBody(body);
   const urlsMatch = renderUrlsPreview && trimmedBody.match(URL_REG);
-  const urls = urlsMatch ? [...new Set(urlsMatch)] : undefined;
+  // [Gitea #286] no genuine card for a site a deceptive link only pretends to be
+  const urls = urlsMatch
+    ? previewUrlsFor(
+        [...new Set(urlsMatch)],
+        typeof customBody === 'string' ? customBody : undefined,
+      )
+    : undefined;
 
   return (
     <>
@@ -458,7 +471,13 @@ export function MNotice({
   if (typeof body !== 'string') return <BrokenContent />;
   const trimmedBody = trimReplyFromBody(body);
   const urlsMatch = renderUrlsPreview && trimmedBody.match(URL_REG);
-  const urls = urlsMatch ? [...new Set(urlsMatch)] : undefined;
+  // [Gitea #286] no genuine card for a site a deceptive link only pretends to be
+  const urls = urlsMatch
+    ? previewUrlsFor(
+        [...new Set(urlsMatch)],
+        typeof customBody === 'string' ? customBody : undefined,
+      )
+    : undefined;
 
   return (
     <>

src/app/utils/linkSafety.test.ts

@@ -1,6 +1,6 @@
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
-import { analyzeLink, hostFromText, registrableDomain } from './linkSafety';
+import { analyzeLink, hostFromText, previewUrlsFor, registrableDomain } from './linkSafety';
 
 test('visible text that names another site is a mismatch', () => {
   const r = analyzeLink('https://matrix.lotusguild.org/login', 'https://evil.example/login');
@@ -73,3 +73,25 @@ test('shared hosting suffixes are separate sites (#335)', () => {
   );
   assert.equal(registrableDomain('news.bbc.co.uk'), 'bbc.co.uk');
 });
+
+test('previewUrlsFor: no preview for a site a deceptive link only claims (#286)', () => {
+  const urls = ['https://paypal.com'];
+  assert.deepEqual(
+    previewUrlsFor(urls, '<a href="https://evil.example/login">https://paypal.com</a>'),
+    [],
+  );
+  // An honest link keeps its preview.
+  assert.deepEqual(
+    previewUrlsFor(urls, '<a href="https://www.paypal.com/x">https://paypal.com</a>'),
+    urls,
+  );
+  assert.deepEqual(previewUrlsFor(urls, undefined), urls);
+  // Other links in the message keep theirs.
+  assert.deepEqual(
+    previewUrlsFor(
+      ['https://paypal.com', 'https://lotusguild.org'],
+      'see <a href="https://evil.example">paypal.com</a> and https://lotusguild.org',
+    ),
+    ['https://lotusguild.org'],
+  );
+});

src/app/utils/linkSafety.ts

@@ -221,3 +221,37 @@ export const analyzeLink = (text: string, href: string): LinkSafety | null => {
   const other = shown.find((h) => registrableDomain(h) !== realSite);
   return { mismatch: other !== undefined, shownHost: other ?? shown[0], realHost, punycode };
 };
+
+const ANCHOR_REG = /<a\s[^>]*href\s*=\s*(["'])(.*?)\1[^>]*>([\s\S]*?)<\/a>/gi;
+const decodeEntities = (s: string): string =>
+  s
+    .replace(/<[^>]+>/g, '')
+    .replace(/&quot;/g, '"')
+    .replace(/&#39;/g, "'")
+    .replace(/&lt;/g, '<')
+    .replace(/&gt;/g, '>')
+    .replace(/&amp;/g, '&');
+
+/**
+ * [Gitea #286] The URLs to build link previews for. Previews come from the
+ * plain `body`, but clicks follow `formatted_body`'s hrefs, and a sender
+ * controls both: text reading "https://paypal.com" linked to evil.example got
+ * a genuine PayPal card. Drop any body URL whose site is only *claimed* by a
+ * deceptive link's text.
+ */
+export const previewUrlsFor = (urls: string[], formattedBody: string | undefined): string[] => {
+  if (!formattedBody || urls.length === 0) return urls;
+  const claimed = new Set<string>();
+  Array.from(formattedBody.matchAll(ANCHOR_REG)).forEach((m) => {
+    const safety = analyzeLink(decodeEntities(m[3]), decodeEntities(m[2]));
+    if (safety?.mismatch && safety.shownHost) claimed.add(registrableDomain(safety.shownHost));
+  });
+  if (claimed.size === 0) return urls;
+  return urls.filter((u) => {
+    try {
+      return !claimed.has(registrableDomain(new URL(u).hostname));
+    } catch {
+      return true;
+    }
+  });
+};