Unverified Commit 6ff67be0 authored by Eugen Rochko's avatar Eugen Rochko Committed by GitHub

Add a spam check (#11217)

* Add a spam check

* Use Nilsimsa to generate locality-sensitive hashes and compare using Levenshtein distance

* Add more tests

* Add exemption when the message is a reply to something that mentions the sender

* Use Nilsimsa Compare Value instead of Levenshtein distance

* Use MD5 for messages shorter than 10 characters

* Add message to automated report, do not add non-public statuses to
automated report, add trust level to accounts and make unsilencing
raise the trust level to prevent repeated spam checks on that account

* Expire spam check data after 3 months

* Add support for local statuses, reduce expiration to 1 week, always create a report

* Add content warnings to the spam check and exempt empty statuses

* Change Nilsimsa threshold to 95 and make sure removed statuses are removed from the spam check

* Add all matched statuses into automatic report
parent 40230277
......@@ -58,6 +58,7 @@ gem 'idn-ruby', require: 'idn'
gem 'kaminari', '~> 1.1'
gem 'link_header', '~> 0.0'
gem 'mime-types', '~> 3.2', require: 'mime/types/columnar'
gem 'nilsimsa', git: 'https://github.com/witgo/nilsimsa', ref: 'fd184883048b922b176939f851338d0a4971a532'
gem 'nokogiri', '~> 1.10'
gem 'nsa', '~> 0.2'
gem 'oj', '~> 3.7'
......
......@@ -12,6 +12,13 @@ GIT
specs:
http_parser.rb (0.6.1)
GIT
remote: https://github.com/witgo/nilsimsa
revision: fd184883048b922b176939f851338d0a4971a532
ref: fd184883048b922b176939f851338d0a4971a532
specs:
nilsimsa (1.1.2)
GEM
remote: https://rubygems.org/
specs:
......@@ -704,6 +711,7 @@ DEPENDENCIES
microformats (~> 4.1)
mime-types (~> 3.2)
net-ldap (~> 0.10)
nilsimsa!
nokogiri (~> 1.10)
nsa (~> 0.2)
oj (~> 3.7)
......
......@@ -41,6 +41,7 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
resolve_thread(@status)
fetch_replies(@status)
check_for_spam
distribute(@status)
forward_for_reply if @status.distributable?
end
......@@ -406,6 +407,18 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
Account.local.where(username: local_usernames).exists?
end
def check_for_spam
spam_check = SpamCheck.new(@status)
return if spam_check.skip?
if spam_check.spam?
spam_check.flag!
else
spam_check.remember!
end
end
def forward_for_reply
return unless @json['signature'].present? && reply_to_local?
ActivityPub::RawDistributionWorker.perform_async(Oj.dump(@json), replied_to_status.account_id, [@account.preferred_inbox_url])
......
# frozen_string_literal: true
class SpamCheck
include Redisable
include ActionView::Helpers::TextHelper
NILSIMSA_COMPARE_THRESHOLD = 95
NILSIMSA_MIN_SIZE = 10
EXPIRE_SET_AFTER = 1.week.seconds
def initialize(status)
@account = status.account
@status = status
end
def skip?
already_flagged? || trusted? || no_unsolicited_mentions? || solicited_reply?
end
def spam?
if insufficient_data?
false
elsif nilsimsa?
any_other_digest?('nilsimsa') { |_, other_digest| nilsimsa_compare_value(digest, other_digest) >= NILSIMSA_COMPARE_THRESHOLD }
else
any_other_digest?('md5') { |_, other_digest| other_digest == digest }
end
end
def flag!
auto_silence_account!
auto_report_status!
end
def remember!
# The scores in sorted sets don't actually have enough bits to hold an exact
# value of our snowflake IDs, so we use it only for its ordering property. To
# get the correct status ID back, we have to save it in the string value
redis.zadd(redis_key, @status.id, digest_with_algorithm)
redis.zremrangebyrank(redis_key, '0', '-10')
redis.expire(redis_key, EXPIRE_SET_AFTER)
end
def reset!
redis.del(redis_key)
end
def hashable_text
return @hashable_text if defined?(@hashable_text)
@hashable_text = @status.text
@hashable_text = remove_mentions(@hashable_text)
@hashable_text = strip_tags(@hashable_text) unless @status.local?
@hashable_text = normalize_unicode(@status.spoiler_text + ' ' + @hashable_text)
@hashable_text = remove_whitespace(@hashable_text)
end
def insufficient_data?
hashable_text.blank?
end
def digest
@digest ||= begin
if nilsimsa?
Nilsimsa.new(hashable_text).hexdigest
else
Digest::MD5.hexdigest(hashable_text)
end
end
end
def digest_with_algorithm
if nilsimsa?
['nilsimsa', digest, @status.id].join(':')
else
['md5', digest, @status.id].join(':')
end
end
private
def remove_mentions(text)
return text.gsub(Account::MENTION_RE, '') if @status.local?
Nokogiri::HTML.fragment(text).tap do |html|
mentions = @status.mentions.map { |mention| ActivityPub::TagManager.instance.url_for(mention.account) }
html.traverse do |element|
element.unlink if element.name == 'a' && mentions.include?(element['href'])
end
end.to_s
end
def normalize_unicode(text)
text.unicode_normalize(:nfkc).downcase
end
def remove_whitespace(text)
text.gsub(/\s+/, ' ').strip
end
def auto_silence_account!
@account.silence!
end
def auto_report_status!
status_ids = Status.where(visibility: %i(public unlisted)).where(id: matching_status_ids).pluck(:id) + [@status.id] if @status.distributable?
ReportService.new.call(Account.representative, @account, status_ids: status_ids, comment: I18n.t('spam_check.spam_detected_and_silenced'))
end
def already_flagged?
@account.silenced?
end
def trusted?
@account.trust_level > Account::TRUST_LEVELS[:untrusted]
end
def no_unsolicited_mentions?
@status.mentions.all? { |mention| mention.silent? || (!@account.local? && !mention.account.local?) || mention.account.following?(@account) }
end
def solicited_reply?
!@status.thread.nil? && @status.thread.mentions.where(account: @account).exists?
end
def nilsimsa_compare_value(first, second)
first = [first].pack('H*')
second = [second].pack('H*')
bits = 0
0.upto(31) do |i|
bits += Nilsimsa::POPC[255 & (first[i].ord ^ second[i].ord)].ord
end
128 - bits # -128 <= Nilsimsa Compare Value <= 128
end
def nilsimsa?
hashable_text.size > NILSIMSA_MIN_SIZE
end
def other_digests
redis.zrange(redis_key, 0, -1)
end
def any_other_digest?(filter_algorithm)
other_digests.any? do |record|
algorithm, other_digest, status_id = record.split(':')
next unless algorithm == filter_algorithm
yield algorithm, other_digest, status_id
end
end
def matching_status_ids
if nilsimsa?
other_digests.select { |record| record.start_with?('nilsimsa') && nilsimsa_compare_value(digest, record.split(':')[1]) >= NILSIMSA_COMPARE_THRESHOLD }.map { |record| record.split(':')[2] }.compact
else
other_digests.select { |record| record.start_with?('md5') && record.split(':')[1] == digest }.map { |record| record.split(':')[2] }.compact
end
end
def redis_key
@redis_key ||= "spam_check:#{@account.id}"
end
end
......@@ -45,6 +45,7 @@
# also_known_as :string is an Array
# silenced_at :datetime
# suspended_at :datetime
# trust_level :integer
#
class Account < ApplicationRecord
......@@ -62,6 +63,11 @@ class Account < ApplicationRecord
include AccountCounters
include DomainNormalizable
TRUST_LEVELS = {
untrusted: 0,
trusted: 1,
}.freeze
enum protocol: [:ostatus, :activitypub]
validates :username, presence: true
......@@ -163,6 +169,10 @@ class Account < ApplicationRecord
last_webfingered_at.nil? || last_webfingered_at <= 1.day.ago
end
def trust_level
self[:trust_level] || 0
end
def refresh!
ResolveAccountService.new.call(acct) unless local?
end
......@@ -171,21 +181,19 @@ class Account < ApplicationRecord
silenced_at.present?
end
def silence!(date = nil)
date ||= Time.now.utc
def silence!(date = Time.now.utc)
update!(silenced_at: date)
end
def unsilence!
update!(silenced_at: nil)
update!(silenced_at: nil, trust_level: trust_level == TRUST_LEVELS[:untrusted] ? TRUST_LEVELS[:trusted] : trust_level)
end
def suspended?
suspended_at.present?
end
def suspend!(date = nil)
date ||= Time.now.utc
def suspend!(date = Time.now.utc)
transaction do
user&.disable! if local?
update!(suspended_at: date)
......
......@@ -23,6 +23,7 @@ class RemoveStatusService < BaseService
remove_from_hashtags
remove_from_public
remove_from_media if status.media_attachments.any?
remove_from_spam_check
@status.destroy!
else
......@@ -142,6 +143,10 @@ class RemoveStatusService < BaseService
redis.publish('timeline:public:local:media', @payload) if @status.local?
end
def remove_from_spam_check
redis.zremrangebyscore("spam_check:#{@status.account_id}", @status.id, @status.id)
end
def lock_options
{ redis: Redis.current, key: "distribute:#{@status.id}" }
end
......
......@@ -875,6 +875,8 @@ en:
profile: Profile
relationships: Follows and followers
two_factor_authentication: Two-factor Auth
spam_check:
spam_detected_and_silenced: This is an automated report. Spam has been detected and the sender has been silenced automatically. If this is a mistake, please unsilence the account.
statuses:
attached:
description: 'Attached: %{attached}'
......
class AddTrustLevelToAccounts < ActiveRecord::Migration[5.2]
def change
add_column :accounts, :trust_level, :integer
end
end
......@@ -148,6 +148,7 @@ ActiveRecord::Schema.define(version: 2019_07_06_233204) do
t.string "also_known_as", array: true
t.datetime "silenced_at"
t.datetime "suspended_at"
t.integer "trust_level"
t.index "(((setweight(to_tsvector('simple'::regconfig, (display_name)::text), 'A'::\"char\") || setweight(to_tsvector('simple'::regconfig, (username)::text), 'B'::\"char\")) || setweight(to_tsvector('simple'::regconfig, (COALESCE(domain, ''::character varying))::text), 'C'::\"char\")))", name: "search_index", using: :gin
t.index "lower((username)::text), lower((domain)::text)", name: "index_accounts_on_username_and_domain_lower", unique: true
t.index ["moved_to_account_id"], name: "index_accounts_on_moved_to_account_id"
......
require 'rails_helper'
RSpec.describe SpamCheck do
let!(:sender) { Fabricate(:account) }
let!(:alice) { Fabricate(:account, username: 'alice') }
let!(:bob) { Fabricate(:account, username: 'bob') }
def status_with_html(text, options = {})
status = PostStatusService.new.call(sender, { text: text }.merge(options))
status.update_columns(text: Formatter.instance.format(status), local: false)
status
end
describe '#hashable_text' do
it 'removes mentions from HTML for remote statuses' do
status = status_with_html('@alice Hello')
expect(described_class.new(status).hashable_text).to eq 'hello'
end
it 'removes mentions from text for local statuses' do
status = PostStatusService.new.call(alice, text: "Hey @#{sender.username}, how are you?")
expect(described_class.new(status).hashable_text).to eq 'hey , how are you?'
end
end
describe '#insufficient_data?' do
it 'returns true when there is no text' do
status = status_with_html('@alice')
expect(described_class.new(status).insufficient_data?).to be true
end
it 'returns false when there is text' do
status = status_with_html('@alice h')
expect(described_class.new(status).insufficient_data?).to be false
end
end
describe '#digest' do
it 'returns a string' do
status = status_with_html('@alice Hello world')
expect(described_class.new(status).digest).to be_a String
end
end
describe '#spam?' do
it 'returns false for a unique status' do
status = status_with_html('@alice Hello')
expect(described_class.new(status).spam?).to be false
end
it 'returns false for different statuses to the same recipient' do
status1 = status_with_html('@alice Hello')
described_class.new(status1).remember!
status2 = status_with_html('@alice Are you available to talk?')
expect(described_class.new(status2).spam?).to be false
end
it 'returns false for statuses with different content warnings' do
status1 = status_with_html('@alice Are you available to talk?')
described_class.new(status1).remember!
status2 = status_with_html('@alice Are you available to talk?', spoiler_text: 'This is a completely different matter than what I was talking about previously, I swear!')
expect(described_class.new(status2).spam?).to be false
end
it 'returns false for different statuses to different recipients' do
status1 = status_with_html('@alice How is it going?')
described_class.new(status1).remember!
status2 = status_with_html('@bob Are you okay?')
expect(described_class.new(status2).spam?).to be false
end
it 'returns false for very short different statuses to different recipients' do
status1 = status_with_html('@alice 🙄')
described_class.new(status1).remember!
status2 = status_with_html('@bob Huh?')
expect(described_class.new(status2).spam?).to be false
end
it 'returns false for statuses with no text' do
status1 = status_with_html('@alice')
described_class.new(status1).remember!
status2 = status_with_html('@bob')
expect(described_class.new(status2).spam?).to be false
end
it 'returns true for duplicate statuses to the same recipient' do
status1 = status_with_html('@alice Hello')
described_class.new(status1).remember!
status2 = status_with_html('@alice Hello')
expect(described_class.new(status2).spam?).to be true
end
it 'returns true for duplicate statuses to different recipients' do
status1 = status_with_html('@alice Hello')
described_class.new(status1).remember!
status2 = status_with_html('@bob Hello')
expect(described_class.new(status2).spam?).to be true
end
it 'returns true for nearly identical statuses with random numbers' do
source_text = 'Sodium, atomic number 11, was first isolated by Humphry Davy in 1807. A chemical component of salt, he named it Na in honor of the saltiest region on earth, North America.'
status1 = status_with_html('@alice ' + source_text + ' 1234')
described_class.new(status1).remember!
status2 = status_with_html('@bob ' + source_text + ' 9568')
expect(described_class.new(status2).spam?).to be true
end
end
describe '#skip?' do
it 'returns true when the sender is already silenced' do
status = status_with_html('@alice Hello')
sender.silence!
expect(described_class.new(status).skip?).to be true
end
it 'returns true when the mentioned person follows the sender' do
status = status_with_html('@alice Hello')
alice.follow!(sender)
expect(described_class.new(status).skip?).to be true
end
it 'returns false when even one mentioned person doesn\'t follow the sender' do
status = status_with_html('@alice @bob Hello')
alice.follow!(sender)
expect(described_class.new(status).skip?).to be false
end
it 'returns true when the sender is replying to a status that mentions the sender' do
parent = PostStatusService.new.call(alice, text: "Hey @#{sender.username}, how are you?")
status = status_with_html('@alice @bob Hello', thread: parent)
expect(described_class.new(status).skip?).to be true
end
end
describe '#remember!' do
pending
end
describe '#flag!' do
let!(:status1) { status_with_html('@alice General Kenobi you are a bold one') }
let!(:status2) { status_with_html('@alice @bob General Kenobi, you are a bold one') }
before do
described_class.new(status1).remember!
described_class.new(status2).flag!
end
it 'silences the account' do
expect(sender.silenced?).to be true
end
it 'creates a report about the account' do
expect(sender.targeted_reports.unresolved.count).to eq 1
end
it 'attaches both matching statuses to the report' do
expect(sender.targeted_reports.first.status_ids).to include(status1.id, status2.id)
end
end
end
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