fix(slack): scope download-file to channel and thread context

src/slack/actions.ts

@@ -280,6 +280,129 @@ export async function listSlackPins(
   return (result.items ?? []) as SlackPin[];
 }
 
+type SlackFileInfoSummary = {
+  id?: string;
+  name?: string;
+  mimetype?: string;
+  url_private?: string;
+  url_private_download?: string;
+  channels?: unknown;
+  groups?: unknown;
+  ims?: unknown;
+  shares?: unknown;
+};
+
+type SlackFileThreadShare = {
+  channelId: string;
+  ts?: string;
+  threadTs?: string;
+};
+
+function normalizeSlackScopeValue(value: string | undefined): string | undefined {
+  const trimmed = value?.trim();
+  return trimmed ? trimmed : undefined;
+}
+
+function collectSlackDirectShareChannelIds(file: SlackFileInfoSummary): Set<string> {
+  const ids = new Set<string>();
+  for (const group of [file.channels, file.groups, file.ims]) {
+    if (!Array.isArray(group)) {
+      continue;
+    }
+    for (const entry of group) {
+      if (typeof entry !== "string") {
+        continue;
+      }
+      const normalized = normalizeSlackScopeValue(entry);
+      if (normalized) {
+        ids.add(normalized);
+      }
+    }
+  }
+  return ids;
+}
+
+function collectSlackShareMaps(file: SlackFileInfoSummary): Array<Record<string, unknown>> {
+  if (!file.shares || typeof file.shares !== "object" || Array.isArray(file.shares)) {
+    return [];
+  }
+  const shares = file.shares as Record<string, unknown>;
+  return [shares.public, shares.private].filter(
+    (value): value is Record<string, unknown> =>
+      Boolean(value) && typeof value === "object" && !Array.isArray(value),
+  );
+}
+
+function collectSlackSharedChannelIds(file: SlackFileInfoSummary): Set<string> {
+  const ids = new Set<string>();
+  for (const shareMap of collectSlackShareMaps(file)) {
+    for (const channelId of Object.keys(shareMap)) {
+      const normalized = normalizeSlackScopeValue(channelId);
+      if (normalized) {
+        ids.add(normalized);
+      }
+    }
+  }
+  return ids;
+}
+
+function collectSlackThreadShares(
+  file: SlackFileInfoSummary,
+  channelId: string,
+): SlackFileThreadShare[] {
+  const matches: SlackFileThreadShare[] = [];
+  for (const shareMap of collectSlackShareMaps(file)) {
+    const rawEntries = shareMap[channelId];
+    if (!Array.isArray(rawEntries)) {
+      continue;
+    }
+    for (const rawEntry of rawEntries) {
+      if (!rawEntry || typeof rawEntry !== "object" || Array.isArray(rawEntry)) {
+        continue;
+      }
+      const entry = rawEntry as Record<string, unknown>;
+      const ts = typeof entry.ts === "string" ? normalizeSlackScopeValue(entry.ts) : undefined;
+      const threadTs =
+        typeof entry.thread_ts === "string" ? normalizeSlackScopeValue(entry.thread_ts) : undefined;
+      matches.push({ channelId, ts, threadTs });
+    }
+  }
+  return matches;
+}
+
+function hasSlackScopeMismatch(params: {
+  file: SlackFileInfoSummary;
+  channelId?: string;
+  threadId?: string;
+}): boolean {
+  const channelId = normalizeSlackScopeValue(params.channelId);
+  if (!channelId) {
+    return false;
+  }
+  const threadId = normalizeSlackScopeValue(params.threadId);
+
+  const directIds = collectSlackDirectShareChannelIds(params.file);
+  const sharedIds = collectSlackSharedChannelIds(params.file);
+  const hasChannelEvidence = directIds.size > 0 || sharedIds.size > 0;
+  const inChannel = directIds.has(channelId) || sharedIds.has(channelId);
+  if (hasChannelEvidence && !inChannel) {
+    return true;
+  }
+
+  if (!threadId) {
+    return false;
+  }
+  const threadShares = collectSlackThreadShares(params.file, channelId);
+  if (threadShares.length === 0) {
+    return false;
+  }
+  const threadEvidence = threadShares.filter((entry) => entry.threadTs || entry.ts);
+  if (threadEvidence.length === 0) {
+    return false;
+  }
+  return !threadEvidence.some((entry) => entry.threadTs === threadId || entry.ts === threadId);
+}
+
 /**
  * Downloads a Slack file by ID and saves it to the local media store.
  * Fetches a fresh download URL via files.info to avoid using stale private URLs.
@@ -287,26 +410,21 @@ export async function listSlackPins(
  */
 export async function downloadSlackFile(
   fileId: string,
-  opts: SlackActionClientOpts & { maxBytes: number },
+  opts: SlackActionClientOpts & { maxBytes: number; channelId?: string; threadId?: string },
 ): Promise<SlackMediaResult | null> {
   const token = resolveToken(opts.token, opts.accountId);
   const client = await getClient(opts);
 
   // Fetch fresh file metadata (includes a current url_private_download).
   const info = await client.files.info({ file: fileId });
-  const file = info.file as
-    | {
-        id?: string;
-        name?: string;
-        mimetype?: string;
-        url_private?: string;
-        url_private_download?: string;
-      }
-    | undefined;
+  const file = info.file as SlackFileInfoSummary | undefined;
 
   if (!file?.url_private_download && !file?.url_private) {
     return null;
   }
+  if (hasSlackScopeMismatch({ file, channelId: opts.channelId, threadId: opts.threadId })) {
+    return null;
+  }
 
   const results = await resolveSlackMedia({
     files: [