refactor(federation): ♻️ Correctly handle bridge requests and instance signatures in user inboxes

api/users/:uuid/inbox/index.ts

@@ -2,7 +2,7 @@ import { apiRoute, applyConfig } from "@/api";
 import { createRoute } from "@hono/zod-openapi";
 import { getLogger } from "@logtape/logtape";
 import type { Entity } from "@versia/federation/types";
-import { User } from "@versia/kit/db";
+import { Instance, User } from "@versia/kit/db";
 import { z } from "zod";
 import { InboxProcessor } from "~/classes/inbox/processor";
 import { ErrorSchema } from "~/types/api";
@@ -23,9 +23,9 @@ export const schemas = {
         uuid: z.string().uuid(),
     }),
     header: z.object({
-        "x-signature": z.string(),
-        "x-nonce": z.string(),
-        "x-signed-by": z.string().url().or(z.literal("instance")),
+        "x-signature": z.string().optional(),
+        "x-nonce": z.string().optional(),
+        "x-signed-by": z.string().url().or(z.string().startsWith("instance ")),
         authorization: z.string().optional(),
     }),
     body: z.any(),
@@ -113,24 +113,37 @@ export default apiRoute((app) =>
 
         const sender = await User.resolve(signedBy);
 
-        if (!sender) {
+        if (!(sender || signedBy.startsWith("instance "))) {
             return context.json(
-                { error: `Couldn't resolve sender ${signedBy}` },
+                { error: `Couldn't resolve sender URI ${signedBy}` },
                 404,
             );
         }
 
         if (sender?.isLocal()) {
             return context.json(
-                { error: "Cannot send federation requests to local users" },
+                {
+                    error: "Cannot process federation requests from local users",
+                },
                 400,
             );
         }
 
+        const remoteInstance = sender
+            ? await Instance.fromUser(sender)
+            : await Instance.resolveFromHost(signedBy.split(" ")[1]);
+
+        if (!remoteInstance) {
+            return context.json(
+                { error: "Could not resolve the remote instance." },
+                500,
+            );
+        }
+
         const processor = new InboxProcessor(
             context,
             body,
-            sender,
+            remoteInstance,
             {
                 signature,
                 nonce,

classes/database/instance.ts

@@ -319,6 +319,18 @@ export class Instance extends BaseInterface<typeof Instances> {
         }
     }
 
+    public static resolveFromHost(host: string): Promise<Instance> {
+        if (host.startsWith("http")) {
+            const url = new URL(host).host;
+
+            return Instance.resolve(url);
+        }
+
+        const url = new URL(`https://${host}`);
+
+        return Instance.resolve(url.origin);
+    }
+
     public static async resolve(url: string): Promise<Instance> {
         const logger = getLogger("federation");
         const host = new URL(url).host;
@@ -346,6 +358,7 @@ export class Instance extends BaseInterface<typeof Instances> {
             version: metadata.software.version,
             logo: metadata.logo,
             protocol,
+            publicKey: metadata.public_key,
         });
     }
 

classes/inbox/processor.test.ts

@@ -1,7 +1,13 @@
 import { beforeEach, describe, expect, jest, mock, test } from "bun:test";
 import { SignatureValidator } from "@versia/federation";
 import type { Entity, Note as VersiaNote } from "@versia/federation/types";
-import { Note, Notification, Relationship, User } from "@versia/kit/db";
+import {
+    type Instance,
+    Note,
+    Notification,
+    Relationship,
+    User,
+} from "@versia/kit/db";
 import type { Context } from "hono";
 import { ValidationError } from "zod-validation-error";
 import { config } from "~/packages/config-manager/index.ts";
@@ -71,7 +77,7 @@ mock.module("~/packages/config-manager/index.ts", () => ({
 describe("InboxProcessor", () => {
     let mockContext: Context;
     let mockBody: Entity;
-    let mockSender: User;
+    let mockSenderInstance: Instance;
     let mockHeaders: {
         signature: string;
         nonce: string;
@@ -98,12 +104,14 @@ describe("InboxProcessor", () => {
         } as unknown as Context;
 
         // Setup basic mock sender
-        mockSender = {
+        mockSenderInstance = {
             id: "test-id",
             data: {
-                publicKey: "test-key",
+                publicKey: {
+                    key: "test-key",
+                },
             },
-        } as unknown as User;
+        } as unknown as Instance;
 
         // Setup basic mock headers
         mockHeaders = {
@@ -118,7 +126,7 @@ describe("InboxProcessor", () => {
         processor = new InboxProcessor(
             mockContext,
             mockBody,
-            mockSender,
+            mockSenderInstance,
             mockHeaders,
         );
     });

classes/inbox/processor.ts

@@ -16,7 +16,7 @@ import type {
     User as VersiaUser,
 } from "@versia/federation/types";
 import {
-    Instance,
+    type Instance,
     Like,
     Note,
     Notification,
@@ -70,7 +70,7 @@ export class InboxProcessor {
      *
      * @param context Hono request context.
      * @param body Entity JSON body.
-     * @param sender Sender of the request (from X-Signed-By header).
+     * @param senderInstance Sender of the request's instance (from X-Signed-By header).
      * @param headers Various request headers.
      * @param logger LogTape logger instance.
      * @param requestIp Request IP address. Grabs it from the Hono context if not provided.
@@ -78,10 +78,10 @@ export class InboxProcessor {
     public constructor(
         private context: Context,
         private body: Entity,
-        private sender: User,
+        private senderInstance: Instance,
         private headers: {
-            signature: string;
-            nonce: string;
+            signature?: string;
+            nonce?: string;
             authorization?: string;
         },
         private logger: Logger = getLogger(["federation", "inbox"]),
@@ -94,14 +94,25 @@ export class InboxProcessor {
      * @returns {Promise<boolean>} - Whether the signature is valid.
      */
     private async isSignatureValid(): Promise<boolean> {
+        if (!this.senderInstance.data.publicKey?.key) {
+            throw new Error(
+                `Instance ${this.senderInstance.data.baseUrl} has no public key stored in database`,
+            );
+        }
+
         if (config.debug.federation) {
-            this.logger.debug`Sender public key: ${this.sender.data.publicKey}`;
+            this.logger
+                .debug`Sender public key: ${this.senderInstance.data.publicKey.key}`;
         }
 
         const validator = await SignatureValidator.fromStringKey(
-            this.sender.data.publicKey,
+            this.senderInstance.data.publicKey.key,
         );
 
+        if (!(this.headers.signature && this.headers.nonce)) {
+            throw new Error("Missing signature or nonce");
+        }
+
         // HACK: Making a fake Request object instead of passing the values directly is necessary because otherwise the validation breaks for some unknown reason
         const isValid = await validator.validate(
             new Request(this.context.req.url, {
@@ -185,16 +196,7 @@ export class InboxProcessor {
     public async process(): Promise<
         (Response & TypedResponse<{ error: string }, 500, "json">) | Response
     > {
-        const remoteInstance = await Instance.fromUser(this.sender);
-
-        if (!remoteInstance) {
-            return this.context.json(
-                { error: "Could not resolve the remote instance." },
-                500,
-            );
-        }
-
-        if (isDefederated(remoteInstance.data.baseUrl)) {
+        if (isDefederated(this.senderInstance.data.baseUrl)) {
             // Return 201 to avoid
             // 1. Leaking defederated instance information
             // 2. Preventing the sender from thinking the message was not delivered and retrying
@@ -439,11 +441,15 @@ export class InboxProcessor {
         const delete_ = this.body as unknown as VersiaDelete;
         const toDelete = delete_.deleted;
 
+        const author = delete_.author
+            ? await User.resolve(delete_.author)
+            : null;
+
         switch (delete_.deleted_type) {
             case "Note": {
                 const note = await Note.fromSql(
                     eq(Notes.uri, toDelete),
-                    eq(Notes.authorId, this.sender.id),
+                    author ? eq(Notes.authorId, author.id) : undefined,
                 );
 
                 if (!note) {
@@ -468,8 +474,8 @@ export class InboxProcessor {
                     );
                 }
 
-                if (userToDelete.id === this.sender.id) {
-                    await this.sender.delete();
+                if (!author || userToDelete.id === author.id) {
+                    await userToDelete.delete();
                     return this.context.text(
                         "Account deleted, goodbye 👋",
                         200,
@@ -486,7 +492,7 @@ export class InboxProcessor {
             case "pub.versia:likes/Like": {
                 const like = await Like.fromSql(
                     eq(Likes.uri, toDelete),
-                    eq(Likes.likerId, this.sender.id),
+                    author ? eq(Likes.likerId, author.id) : undefined,
                 );
 
                 if (!like) {

drizzle/migrations/0035_pretty_whiplash.sql

@@ -0,0 +1 @@
+ALTER TABLE "Instances" ADD COLUMN "public_key" jsonb;

drizzle/migrations/meta/_journal.json

@@ -246,6 +246,13 @@
             "when": 1729789587213,
             "tag": "0034_jittery_proemial_gods",
             "breakpoints": true
+        },
+        {
+            "idx": 35,
+            "version": "7",
+            "when": 1732398961365,
+            "tag": "0035_pretty_whiplash",
+            "breakpoints": true
         }
     ]
 }

drizzle/schema.ts

@@ -1,5 +1,5 @@
 import type { Source as ApiSource } from "@versia/client/types";
-import type { ContentFormat } from "@versia/federation/types";
+import type { ContentFormat, InstanceMetadata } from "@versia/federation/types";
 import type { Challenge } from "altcha-lib/types";
 import { relations, sql } from "drizzle-orm";
 import {
@@ -351,6 +351,7 @@ export const Instances = pgTable("Instances", {
         .notNull()
         .$type<"versia" | "activitypub">()
         .default("versia"),
+    publicKey: jsonb("public_key").$type<InstanceMetadata["public_key"]>(),
 });
 
 export const OpenIdAccounts = pgTable("OpenIdAccounts", {