Fix IP address rate limit (#8758)

* Fix IP address rate limit

* CHANGELOG

* Tune getIpHash

4 files changed, 15 insertions, 10 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9b086ddba9..cfcf52ce92 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,7 +26,7 @@ You should also include the user name that made the change.
   Your own theme color may be unset if it was in an invalid format.
   Admins should check their instance settings if in doubt.
 - Perform port diagnosis at startup only when Listen fails @mei23
-- Rate limiting is now also usable for non-authenticated users. @Johann150
+- Rate limiting is now also usable for non-authenticated users. @Johann150 @mei23
   Admins should make sure the reverse proxy sets the `X-Forwarded-For` header to the original address.
 
 ### Bugfixes
diff --git a/packages/backend/src/misc/get-ip-hash.ts b/packages/backend/src/misc/get-ip-hash.ts
new file mode 100644
index 0000000000..379325bb13
--- /dev/null
+++ b/packages/backend/src/misc/get-ip-hash.ts
@@ -0,0 +1,9 @@
+import IPCIDR from 'ip-cidr';
+
+export function getIpHash(ip: string) {
+	// because a single person may control many IPv6 addresses,
+	// only a /64 subnet prefix of any IP will be taken into account.
+	// (this means for IPv4 the entire address is used)
+	const prefix = IPCIDR.createAddress(ip).mask(64);
+	return 'ip-' + BigInt('0b' + prefix).toString(36);
+}
diff --git a/packages/backend/src/server/api/call.ts b/packages/backend/src/server/api/call.ts
index fbe25e1732..cd3e0abc06 100644
--- a/packages/backend/src/server/api/call.ts
+++ b/packages/backend/src/server/api/call.ts
@@ -6,7 +6,7 @@ import endpoints, { IEndpointMeta } from './endpoints.js';
 import { ApiError } from './error.js';
 import { apiLogger } from './logger.js';
 import { AccessToken } from '@/models/entities/access-token.js';
-import IPCIDR from 'ip-cidr';
+import { getIpHash } from '@/misc/get-ip-hash.js';
 
 const accessDenied = {
 	message: 'Access denied.',
@@ -33,18 +33,13 @@ export default async (endpoint: string, user: CacheableLocalUser | null | undefi
 		throw new ApiError(accessDenied);
 	}
 
-	if (ep.meta.requireCredential && ep.meta.limit && !isModerator) {
+	if (ep.meta.limit && !isModerator) {
 		// koa will automatically load the `X-Forwarded-For` header if `proxy: true` is configured in the app.
 		let limitActor: string;
 		if (user) {
 			limitActor = user.id;
 		} else {
-			// because a single person may control many IPv6 addresses,
-			// only a /64 subnet prefix of any IP will be taken into account.
-			// (this means for IPv4 the entire address is used)
-			const ip = IPCIDR.createAddress(ctx.ip).mask(64);
-
-			limitActor = 'ip-' + parseInt(ip, 2).toString(36);
+			limitActor = getIpHash(ctx!.ip);
 		}
 
 		const limit = Object.assign({}, ep.meta.limit);
diff --git a/packages/backend/src/server/api/private/signin.ts b/packages/backend/src/server/api/private/signin.ts
index b304550e29..79b31764fd 100644
--- a/packages/backend/src/server/api/private/signin.ts
+++ b/packages/backend/src/server/api/private/signin.ts
@@ -10,6 +10,7 @@ import { verifyLogin, hash } from '../2fa.js';
 import { randomBytes } from 'node:crypto';
 import { IsNull } from 'typeorm';
 import { limiter } from '../limiter.js';
+import { getIpHash } from '@/misc/get-ip-hash.js';
 
 export default async (ctx: Koa.Context) => {
 	ctx.set('Access-Control-Allow-Origin', config.url);
@@ -27,7 +28,7 @@ export default async (ctx: Koa.Context) => {
 
 	try {
 		// not more than 1 attempt per second and not more than 10 attempts per hour
-		await limiter({ key: 'signin', duration: 60 * 60 * 1000, max: 10, minInterval: 1000 }, ctx.ip);
+		await limiter({ key: 'signin', duration: 60 * 60 * 1000, max: 10, minInterval: 1000 }, getIpHash(ctx.ip));
 	} catch (err) {
 		ctx.status = 429;
 		ctx.body = {