Add canonical e-mail blocks for suspended accounts (#16049)

Prevent new accounts from being created using the same underlying
e-mail as a suspended account using extensions and period
permutations. Stores e-mails as a SHA256 hash

spec/fabricators/canonical_email_block_fabricator.rb

@@ -0,0 +1,4 @@
+Fabricator(:canonical_email_block) do
+  email "test@example.com"
+  reference_account { Fabricate(:account) }
+end

spec/models/canonical_email_block_spec.rb

@@ -0,0 +1,47 @@
+require 'rails_helper'
+
+RSpec.describe CanonicalEmailBlock, type: :model do
+  describe '#email=' do
+    let(:target_hash) { '973dfe463ec85785f5f95af5ba3906eedb2d931c24e69824a89ea65dba4e813b' }
+
+    it 'sets canonical_email_hash' do
+      subject.email = 'test@example.com'
+      expect(subject.canonical_email_hash).to eq target_hash
+    end
+
+    it 'sets the same hash even with dot permutations' do
+      subject.email = 't.e.s.t@example.com'
+      expect(subject.canonical_email_hash).to eq target_hash
+    end
+
+    it 'sets the same hash even with extensions' do
+      subject.email = 'test+mastodon1@example.com'
+      expect(subject.canonical_email_hash).to eq target_hash
+    end
+
+    it 'sets the same hash with different casing' do
+      subject.email = 'Test@EXAMPLE.com'
+      expect(subject.canonical_email_hash).to eq target_hash
+    end
+  end
+
+  describe '.block?' do
+    let!(:canonical_email_block) { Fabricate(:canonical_email_block, email: 'foo@bar.com') }
+
+    it 'returns true for the same email' do
+      expect(described_class.block?('foo@bar.com')).to be true
+    end
+
+    it 'returns true for the same email with dots' do
+      expect(described_class.block?('f.oo@bar.com')).to be true
+    end
+
+    it 'returns true for the same email with extensions' do
+      expect(described_class.block?('foo+spam@bar.com')).to be true
+    end
+
+    it 'returns false for different email' do
+      expect(described_class.block?('hoge@bar.com')).to be false
+    end
+  end
+end

spec/validators/blacklisted_email_validator_spec.rb

@@ -9,23 +9,36 @@ RSpec.describe BlacklistedEmailValidator, type: :validator do
 
     before do
       allow(user).to receive(:valid_invitation?) { false }
-      allow_any_instance_of(described_class).to receive(:blocked_email?) { blocked_email }
-      described_class.new.validate(user)
+      allow_any_instance_of(described_class).to receive(:blocked_email_provider?) { blocked_email }
     end
 
-    context 'blocked_email?' do
+    subject { described_class.new.validate(user); errors }
+
+    context 'when e-mail provider is blocked' do
       let(:blocked_email) { true }
 
-      it 'calls errors.add' do
-        expect(errors).to have_received(:add).with(:email, :blocked)
+      it 'adds error' do
+        expect(subject).to have_received(:add).with(:email, :blocked)
       end
     end
 
-    context '!blocked_email?' do
+    context 'when e-mail provider is not blocked' do
       let(:blocked_email) { false }
 
-      it 'not calls errors.add' do
-        expect(errors).not_to have_received(:add).with(:email, :blocked)
+      it 'does not add errors' do
+        expect(subject).not_to have_received(:add).with(:email, :blocked)
+      end
+
+      context 'when canonical e-mail is blocked' do
+        let(:other_user) { Fabricate(:user, email: 'i.n.f.o@mail.com') }
+
+        before do
+          other_user.account.suspend!
+        end
+
+        it 'adds error' do
+          expect(subject).to have_received(:add).with(:email, :taken)
+        end
       end
     end
   end