fix(backend): check visibility of following/followers of remote users / feat: moderators can see following/followers of all users (#14375)

* fix(backend): check visibility of following/followers of remote users

Resolves https://github.com/misskey-dev/misskey/issues/13362.

* test(backend): add tests for visibility of following/followers of remote users

* docs(changelog): update CHANGELOG.md

* feat: moderators can see following/followers of all users

* docs(changelog): update CHANGELOG.md

* refactor(backend): minor refactoring

`createPerson`と`if`の条件を統一するとともに、異常系の
処理をearly returnに追い出すための変更。

* feat(backend): moderators can see following/followers count of all users

As per https://github.com/misskey-dev/misskey/pull/14375#issuecomment-2275044908.

2 files changed, 38 insertions, 30 deletions

diff --git a/packages/backend/src/server/api/endpoints/users/followers.ts b/packages/backend/src/server/api/endpoints/users/followers.ts
index 7ce7734f53..a8b4319a61 100644
--- a/packages/backend/src/server/api/endpoints/users/followers.ts
+++ b/packages/backend/src/server/api/endpoints/users/followers.ts
@@ -11,6 +11,7 @@ import { QueryService } from '@/core/QueryService.js';
 import { FollowingEntityService } from '@/core/entities/FollowingEntityService.js';
 import { UtilityService } from '@/core/UtilityService.js';
 import { DI } from '@/di-symbols.js';
+import { RoleService } from '@/core/RoleService.js';
 import { ApiError } from '../../error.js';
 
 export const meta = {
@@ -81,6 +82,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private utilityService: UtilityService,
 		private followingEntityService: FollowingEntityService,
 		private queryService: QueryService,
+		private roleService: RoleService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
 			const user = await this.usersRepository.findOneBy(ps.userId != null
@@ -93,22 +95,24 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 
 			const profile = await this.userProfilesRepository.findOneByOrFail({ userId: user.id });
 
-			if (profile.followersVisibility === 'private') {
-				if (me == null || (me.id !== user.id)) {
-					throw new ApiError(meta.errors.forbidden);
-				}
-			} else if (profile.followersVisibility === 'followers') {
-				if (me == null) {
-					throw new ApiError(meta.errors.forbidden);
-				} else if (me.id !== user.id) {
-					const isFollowing = await this.followingsRepository.exists({
-						where: {
-							followeeId: user.id,
-							followerId: me.id,
-						},
-					});
-					if (!isFollowing) {
+			if (profile.followersVisibility !== 'public' && !await this.roleService.isModerator(me)) {
+				if (profile.followersVisibility === 'private') {
+					if (me == null || (me.id !== user.id)) {
+						throw new ApiError(meta.errors.forbidden);
+					}
+				} else if (profile.followersVisibility === 'followers') {
+					if (me == null) {
 						throw new ApiError(meta.errors.forbidden);
+					} else if (me.id !== user.id) {
+						const isFollowing = await this.followingsRepository.exists({
+							where: {
+								followeeId: user.id,
+								followerId: me.id,
+							},
+						});
+						if (!isFollowing) {
+							throw new ApiError(meta.errors.forbidden);
+						}
 					}
 				}
 			}
diff --git a/packages/backend/src/server/api/endpoints/users/following.ts b/packages/backend/src/server/api/endpoints/users/following.ts
index 6b3389f0b2..feda5bb353 100644
--- a/packages/backend/src/server/api/endpoints/users/following.ts
+++ b/packages/backend/src/server/api/endpoints/users/following.ts
@@ -12,6 +12,7 @@ import { QueryService } from '@/core/QueryService.js';
 import { FollowingEntityService } from '@/core/entities/FollowingEntityService.js';
 import { UtilityService } from '@/core/UtilityService.js';
 import { DI } from '@/di-symbols.js';
+import { RoleService } from '@/core/RoleService.js';
 import { ApiError } from '../../error.js';
 
 export const meta = {
@@ -90,6 +91,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private utilityService: UtilityService,
 		private followingEntityService: FollowingEntityService,
 		private queryService: QueryService,
+		private roleService: RoleService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
 			const user = await this.usersRepository.findOneBy(ps.userId != null
@@ -102,22 +104,24 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 
 			const profile = await this.userProfilesRepository.findOneByOrFail({ userId: user.id });
 
-			if (profile.followingVisibility === 'private') {
-				if (me == null || (me.id !== user.id)) {
-					throw new ApiError(meta.errors.forbidden);
-				}
-			} else if (profile.followingVisibility === 'followers') {
-				if (me == null) {
-					throw new ApiError(meta.errors.forbidden);
-				} else if (me.id !== user.id) {
-					const isFollowing = await this.followingsRepository.exists({
-						where: {
-							followeeId: user.id,
-							followerId: me.id,
-						},
-					});
-					if (!isFollowing) {
+			if (profile.followingVisibility !== 'public' && !await this.roleService.isModerator(me)) {
+				if (profile.followingVisibility === 'private') {
+					if (me == null || (me.id !== user.id)) {
+						throw new ApiError(meta.errors.forbidden);
+					}
+				} else if (profile.followingVisibility === 'followers') {
+					if (me == null) {
 						throw new ApiError(meta.errors.forbidden);
+					} else if (me.id !== user.id) {
+						const isFollowing = await this.followingsRepository.exists({
+							where: {
+								followeeId: user.id,
+								followerId: me.id,
+							},
+						});
+						if (!isFollowing) {
+							throw new ApiError(meta.errors.forbidden);
+						}
 					}
 				}
 			}