fix: accept the release .sig when installing a plugin from a file

src/backend/database/routes/plugins.ts

@@ -2706,6 +2706,10 @@ router.put(
  *     summary: Upload a .tmxplug to install from a file
  *     description: >
  *       Developer mode only. The body is the raw .tmxplug (at most 50 MB).
+       The release's .sig may come base64 encoded in the
+       X-Termix-Plugin-Signature header; an official one makes the file
+       install as an official plugin, and it may then fill in a plugin
+       whose download failed.
  *       The file is checked (archive, manifest, plugin API) and held for 30
  *       minutes, but nothing is loaded. The answer lists what it asks for so
  *       the admin can agree, then POST /plugins/upload/{token}/install
@@ -2751,7 +2755,13 @@ router.post(
     }
     try {
       const { stageUpload } = await import("../../plugins/manage.js");
-      res.json(await stageUpload(req.body));
+      // The release's .sig, base64 encoded, so an official file installs as
+      // official (and may write the tables its 2.8 version left).
+      const header = req.get("x-termix-plugin-signature");
+      const signature = header
+        ? Buffer.from(header, "base64").toString("utf8")
+        : null;
+      res.json(await stageUpload(req.body, signature));
     } catch (error) {
       sendManageError(
         res,

src/backend/plugins/manage.ts

@@ -73,7 +73,7 @@ import {
   pluginFeatures,
   type PluginManifest,
 } from "./manifest.js";
-import { requireSignedPlugins } from "./trust.js";
+import { requireSignedPlugins, verifyAnyTrusted } from "./trust.js";
 import {
   parseChangelog,
   parseReleaseNotes,
@@ -1525,6 +1525,8 @@ interface StagedUpload {
   file: string;
   manifest: PluginManifest;
   expiresAt: number;
+  /** Set when the upload came with a .sig an official key made. */
+  official: boolean;
 }
 
 const uploads = new Map<string, StagedUpload>();
@@ -1548,6 +1550,29 @@ export interface UploadPreview {
   capabilities: string[];
   /** The version of an earlier upload this one replaces. */
   replaces: string | null;
+  /** The .sig sent with it was made by the official Termix key. */
+  official: boolean;
+}
+
+/**
+ * Checks a .sig sent with an upload. An official signature makes the file
+ * the same as a registry download, so it may stand in for one that could not
+ * be fetched (an offline install). Anything else is refused.
+ */
+function checkUploadSignature(
+  buffer: Buffer,
+  signature: string,
+): { official: boolean } {
+  const sha256 = crypto.createHash("sha256").update(buffer).digest("hex");
+  const result = verifyAnyTrusted(buffer, sha256, signature);
+  if (result.ok === false) {
+    throw new PluginManageError(
+      `The signature does not match this file: ${result.reason}`,
+      400,
+      "INVALID_SIGNATURE",
+    );
+  }
+  return { official: result.tier === "official" };
 }
 
 async function assertUploadsAllowed(): Promise<void> {
@@ -1604,9 +1629,17 @@ function validateUpload(buffer: Buffer): PluginManifest {
   return manifest;
 }
 
-/** Only another upload of the same id can be replaced from a file. */
-async function assertReplaceable(pluginId: string): Promise<string | null> {
+/**
+ * Only another upload of the same id can be replaced from a file. An
+ * officially signed file may also fill in a plugin whose code is missing, like
+ * one that was on but could not be downloaded.
+ */
+async function assertReplaceable(
+  pluginId: string,
+  official = false,
+): Promise<string | null> {
   const { loader } = getPluginRuntime();
+  if (official && !loader.get(pluginId)) return null;
   if (loader.bundledIds().has(pluginId)) {
     throw new PluginManageError(
       `${pluginId} ships with Termix and can only be replaced by a signed release`,
@@ -1631,21 +1664,30 @@ async function assertReplaceable(pluginId: string): Promise<string | null> {
  * Checks an uploaded .tmxplug and holds it until the admin agrees to what
  * it asks for. Nothing is loaded yet.
  */
-export async function stageUpload(buffer: Buffer): Promise<UploadPreview> {
+export async function stageUpload(
+  buffer: Buffer,
+  signature: string | null = null,
+): Promise<UploadPreview> {
   await assertUploadsAllowed();
   await clearUploads(Date.now());
   const manifest = validateUpload(buffer);
-  const replaces = await assertReplaceable(manifest.id);
+  const { official } = signature
+    ? checkUploadSignature(buffer, signature)
+    : { official: false };
+  const replaces = await assertReplaceable(manifest.id, official);
 
   const token = crypto.randomBytes(16).toString("hex");
   const dir = getDownloadsDir();
   await fs.promises.mkdir(dir, { recursive: true });
   const file = path.join(dir, `upload-${token}.tmxplug`);
   await fs.promises.writeFile(file, buffer);
+  // Next to the file, where the loader looks for it.
+  if (signature) await fs.promises.writeFile(`${file}.sig`, signature);
   uploads.set(token, {
     file,
     manifest,
     expiresAt: Date.now() + UPLOAD_TTL_MS,
+    official,
   });
 
   return {
@@ -1658,6 +1700,7 @@ export async function stageUpload(buffer: Buffer): Promise<UploadPreview> {
     features: pluginFeatures(manifest.features),
     capabilities: [...manifest.capabilities],
     replaces,
+    official,
   };
 }
 
@@ -1687,7 +1730,7 @@ export function installUpload(
       );
     }
     assertConsent(options.capabilities, manifest.capabilities);
-    await assertReplaceable(pluginId);
+    await assertReplaceable(pluginId, upload.official);
 
     const { createCurrentPluginRepository } = await repos();
     const repository = createCurrentPluginRepository();
@@ -1700,6 +1743,7 @@ export function installUpload(
       plugin = await swapIn(pluginId, { upload: upload.file });
     } catch (error) {
       await fs.promises.rm(upload.file, { force: true });
+      await fs.promises.rm(`${upload.file}.sig`, { force: true });
       const { loader } = getPluginRuntime();
       if (before && wasEnabled && loader.get(pluginId)) {
         await startAndRecord(pluginId);
@@ -1712,7 +1756,7 @@ export function installUpload(
     }
 
     await repository.update(pluginId, {
-      tier: UNVERIFIED_TIER,
+      tier: upload.official ? "official" : UNVERIFIED_TIER,
       registryId: null,
       pinnedVersion: null,
       autoUpdate: false,
@@ -1736,7 +1780,7 @@ export function installUpload(
     }
     const state = await startAndRecord(pluginId);
     pluginLogger.warn(
-      `Installed unverified plugin ${pluginId}@${manifest.version} from a file`,
+      `Installed ${upload.official ? "officially signed" : "unverified"} plugin ${pluginId}@${manifest.version} from a file`,
       { operation: "plugin_install" },
     );
     return { id: pluginId, version: manifest.version, state };

src/backend/tests/plugins/manage.test.ts

@@ -902,6 +902,57 @@ describe("installing from a file", () => {
     expect(db.rows.get("notes")?.tier).toBe(manage.UNVERIFIED_TIER);
   });
 
+  it("refuses a signature that does not match the file", async () => {
+    await boot();
+    await manage.setDeveloperMode(true);
+    await expect(
+      manage.stageUpload(await artifactBuffer("notes"), "bm90IGEgc2ln"),
+    ).rejects.toMatchObject({ code: "INVALID_SIGNATURE" });
+  });
+
+  it("keeps a signature from a non official key unverified", async () => {
+    const { setCustomPluginKeys } = await import("../../plugins/trust.js");
+    const { publicKey, privateKey } = crypto.generateKeyPairSync("ed25519");
+    setCustomPluginKeys([
+      {
+        id: "mine",
+        publicKey: publicKey
+          .export({ format: "der", type: "spki" })
+          .subarray(12)
+          .toString("base64"),
+        addedIn: "26.10.6",
+      },
+    ]);
+    try {
+      await boot();
+      await manage.setDeveloperMode(true);
+      setCustomPluginKeys([
+        {
+          id: "mine",
+          publicKey: publicKey
+            .export({ format: "der", type: "spki" })
+            .subarray(12)
+            .toString("base64"),
+          addedIn: "26.10.6",
+        },
+      ]);
+      const buffer = await artifactBuffer("notes");
+      const digest = crypto.createHash("sha256").update(buffer).digest();
+      const signature = crypto
+        .sign(null, digest, privateKey)
+        .toString("base64");
+      const preview = await manage.stageUpload(buffer, signature);
+      expect(preview.official).toBe(false);
+      await manage.installUpload(preview.token, {
+        userId: "admin",
+        capabilities: preview.capabilities,
+      });
+      expect(db.rows.get("notes")?.tier).toBe(manage.UNVERIFIED_TIER);
+    } finally {
+      setCustomPluginKeys([]);
+    }
+  });
+
   it("refuses a file that is not a plugin archive", async () => {
     await boot();
     await manage.setDeveloperMode(true);

src/ui/api/plugins-api.ts

@@ -643,11 +643,24 @@ export interface PluginUploadPreview {
   features?: string[];
   capabilities: string[];
   replaces: string | null;
+  official?: boolean;
 }
 
-export async function uploadPlugin(file: Blob): Promise<PluginUploadPreview> {
+export async function uploadPlugin(
+  file: Blob,
+  signature?: string,
+): Promise<PluginUploadPreview> {
   const response = await rbacApi.post("/plugins/upload", file, {
-    headers: { "Content-Type": "application/octet-stream" },
+    headers: {
+      "Content-Type": "application/octet-stream",
+      ...(signature
+        ? {
+            "X-Termix-Plugin-Signature": btoa(
+              String.fromCharCode(...new TextEncoder().encode(signature)),
+            ),
+          }
+        : {}),
+    },
   });
   return response.data;
 }

src/ui/plugins/PluginsTab.tsx

@@ -983,12 +983,16 @@ function UploadButton({ manager }: { manager: PluginsManager }) {
       <input
         ref={input}
         type="file"
-        accept=".tmxplug"
+        accept=".tmxplug,.sig"
+        multiple
         className="hidden"
         onChange={(e) => {
-          const file = e.target.files?.[0];
+          // A release's .sig can be picked with it, so it installs as official.
+          const files = [...(e.target.files ?? [])];
           e.target.value = "";
-          if (file) void manager.requestUpload(file);
+          const file = files.find((f) => f.name.endsWith(".tmxplug"));
+          const signature = files.find((f) => f.name.endsWith(".sig"));
+          if (file) void manager.requestUpload(file, signature);
         }}
       />
       <Button

src/ui/plugins/use-plugins-manager.ts

@@ -333,11 +333,17 @@ export function usePluginsManager() {
     [run, t, failToast],
   );
 
-  /** Reads a picked .tmxplug and asks for consent before anything loads. */
+  /**
+   * Reads a picked .tmxplug, with its .sig when one was picked too, and asks
+   * for consent before anything loads.
+   */
   const requestUpload = useCallback(
-    async (file: File) => {
+    async (file: File, signatureFile?: File) => {
       try {
-        const preview = await uploadPlugin(file);
+        const preview = await uploadPlugin(
+          file,
+          signatureFile ? await signatureFile.text() : undefined,
+        );
         setConsent({
           plugin: uploadEntry(preview),
           mode: "upload",