Merge pull request from GHSA-3f39-6537-3cgc

This commit implements HTTP header and body validation to fix
[SIF-2023-002](https://advisory.silicon.moe/advisory/sif-2023-002/)

Signed-off-by: perillamint <perillamint@silicon.moe>
Co-authored-by: perillamint <perillamint@silicon.moe>
Co-authored-by: yunochi <yuno@yunochi.com>

2 files changed, 63 insertions, 3 deletions

diff --git a/packages/backend/src/server/ActivityPubServerService.ts b/packages/backend/src/server/ActivityPubServerService.ts
index 2e64d41c91..17c503ef8e 100644
--- a/packages/backend/src/server/ActivityPubServerService.ts
+++ b/packages/backend/src/server/ActivityPubServerService.ts
@@ -3,6 +3,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
+import * as crypto from 'node:crypto';
 import { IncomingMessage } from 'node:http';
 import { Inject, Injectable } from '@nestjs/common';
 import fastifyAccepts from '@fastify/accepts';
@@ -108,7 +109,58 @@ export class ActivityPubServerService {
 			return;
 		}
 
-		// TODO: request.bodyのバリデーション？
+		if (signature.params.headers.indexOf('host') === -1
+			|| request.headers.host !== this.config.host) {
+			// Host not specified or not match.
+			reply.code(401);
+			return;
+		}
+
+		if (signature.params.headers.indexOf('digest') === -1) {
+			// Digest not found.
+			reply.code(401);
+		} else {
+			const digest = request.headers.digest;
+
+			if (typeof digest !== 'string') {
+				// Huh?
+				reply.code(401);
+				return;
+			}
+
+			const re = /^([a-zA-Z0-9\-]+)=(.+)$/;
+			const match = digest.match(re);
+
+			if (match == null) {
+				// Invalid digest
+				reply.code(401);
+				return;
+			}
+
+			const algo = match[1];
+			const digestValue = match[2];
+
+			if (algo !== 'SHA-256') {
+				// Unsupported digest algorithm
+				reply.code(401);
+				return;
+			}
+
+			if (request.rawBody == null) {
+				// Bad request
+				reply.code(400);
+				return;
+			}
+
+			const hash = crypto.createHash('sha256').update(request.rawBody).digest('base64');
+
+			if (hash !== digestValue) {
+				// Invalid digest
+				reply.code(401);
+				return;
+			}
+		}
+
 		this.queueService.inbox(request.body as IActivity, signature);
 
 		reply.code(202);
@@ -474,8 +526,8 @@ export class ActivityPubServerService {
 
 		//#region Routing
 		// inbox (limit: 64kb)
-		fastify.post('/inbox', { bodyLimit: 1024 * 64 }, async (request, reply) => await this.inbox(request, reply));
-		fastify.post('/users/:user/inbox', { bodyLimit: 1024 * 64 }, async (request, reply) => await this.inbox(request, reply));
+		fastify.post('/inbox', { config: { rawBody: true }, bodyLimit: 1024 * 64 }, async (request, reply) => await this.inbox(request, reply));
+		fastify.post('/users/:user/inbox', { config: { rawBody: true }, bodyLimit: 1024 * 64 }, async (request, reply) => await this.inbox(request, reply));
 
 		// note
 		fastify.get<{ Params: { note: string; } }>('/notes/:note', { constraints: { apOrHtml: 'ap' } }, async (request, reply) => {
diff --git a/packages/backend/src/server/ServerService.ts b/packages/backend/src/server/ServerService.ts
index 757cf21615..6e1956cd1d 100644
--- a/packages/backend/src/server/ServerService.ts
+++ b/packages/backend/src/server/ServerService.ts
@@ -9,6 +9,7 @@ import { fileURLToPath } from 'node:url';
 import { Inject, Injectable, OnApplicationShutdown } from '@nestjs/common';
 import Fastify, { FastifyInstance } from 'fastify';
 import fastifyStatic from '@fastify/static';
+import fastifyRawBody from 'fastify-raw-body';
 import { IsNull } from 'typeorm';
 import { GlobalEventService } from '@/core/GlobalEventService.js';
 import type { Config } from '@/config.js';
@@ -86,6 +87,13 @@ export class ServerService implements OnApplicationShutdown {
 			});
 		}
 
+		// Register raw-body parser for ActivityPub HTTP signature validation.
+		fastify.register(fastifyRawBody, {
+			global: false,
+			encoding: 'utf-8',
+			runFirst: true,
+		});
+
 		// Register non-serving static server so that the child services can use reply.sendFile.
 		// `root` here is just a placeholder and each call must use its own `rootPath`.
 		fastify.register(fastifyStatic, {