Deny access to methods other than GET for readonly access tokens

app/controllers/application_controller.rb

@@ -41,7 +41,7 @@ def authenticate_using_access_tokens
     if request.headers["X-Api-Token"].present?
       token = request.headers["X-Api-Token"]
       @access_token = AccessToken.active.find_by_token_digest(Digest::SHA256.hexdigest(token))
-      if @access_token.present?
+      if @access_token.present? && AccessTokenPolicy.new(@access_token, request).request?
         @access_token.update!(last_accessed_at: Time.zone.now)
         true
       else
@@ -50,7 +50,9 @@ def authenticate_using_access_tokens
     else
       authenticate_with_http_token do |token|
         @access_token = AccessToken.active.find_by_token_digest(Digest::SHA256.hexdigest(token))
-        @access_token.update!(last_accessed_at: Time.zone.now) if @access_token.present?
+        return unless @access_token.present? && AccessTokenPolicy.new(@access_token, request).request?
+
+        @access_token.update!(last_accessed_at: Time.zone.now)
       end
     end
   end

app/policies/access_token_policy.rb

@@ -0,0 +1,12 @@
+class AccessTokenPolicy
+  attr_reader :access_token, :request
+
+  def initialize(access_token, request)
+    @access_token = access_token
+    @request = request
+  end
+
+  def request?
+    access_token.all_permissions? || request.get?
+  end
+end

spec/integration/access_tokens_spec.rb

@@ -47,5 +47,52 @@
 
       expect(response).to have_http_status(:unauthorized)
     end
+
+    context "when a user has a readonly token" do
+      let(:access) do
+        AccessToken.new(owner: :test, permissions: :readonly)
+      end
+
+      let(:headers) do
+        { Authorization: "Token #{token}" }
+      end
+
+      it "allows access to the API for GET requests" do
+        get(forms_path, headers:)
+
+        expect(response).to have_http_status(:ok)
+      end
+
+      it "denies access to the API for POST requests" do
+        post(forms_path, params: { form: { name: "test form" } }, headers:)
+
+        expect(response).to have_http_status(:unauthorized)
+        expect(Form.last).to be nil
+      end
+
+      it "denies access to the API for PUT requests" do
+        form = create :form, id: 1, name: "test form"
+
+        put(form_path(1), params: { form: { name: "edited test form" } }, headers:)
+
+        expect(response).to have_http_status(:unauthorized)
+        expect(form.name).to eq "test form"
+      end
+
+      it "denies access to the API for PATCH requests" do
+        form = create :form, id: 1, name: "test form"
+
+        patch(form_path(1), params: { form: { name: "edited test form" } }, headers:)
+
+        expect(response).to have_http_status(:unauthorized)
+        expect(form.name).to eq "test form"
+      end
+
+      it "does not allow creating other access tokens" do
+        post(access_tokens_path, params: { owner: "test" }, headers:)
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
   end
 end

spec/policies/access_token_policy_spec.rb

@@ -0,0 +1,53 @@
+require "rails_helper"
+
+RSpec.describe AccessTokenPolicy do
+  subject(:policy) { described_class.new(access, request) }
+
+  let(:access) do
+    build :access_token
+  end
+
+  let(:request) do
+    ActionDispatch::Request.empty
+  end
+
+  describe "#request?" do
+    before do
+      request.headers["REQUEST_METHOD"] = request_method
+    end
+
+    context "when request method is GET" do
+      let(:request_method) { "GET" }
+
+      it "grants access if access token has all permissions" do
+        access.permissions = :all
+
+        expect(policy.request?).to be true
+      end
+
+      it "grants access if access token has readonly permissions" do
+        access.permissions = :readonly
+
+        expect(policy.request?).to be true
+      end
+    end
+
+    (ActionDispatch::Request::HTTP_METHODS - %w[GET]).each do |request_method_|
+      context "when request method is #{request_method_}" do
+        let(:request_method) { request_method_ }
+
+        it "grants access if access token has all permissions" do
+          access.permissions = :all
+
+          expect(policy.request?).to be true
+        end
+
+        it "denies access if access token has readonly permissions" do
+          access.permissions = :readonly
+
+          expect(policy.request?).to be false
+        end
+      end
+    end
+  end
+end

spec/request/application_controller_spec.rb

@@ -156,6 +156,25 @@
           expect(json_body[:status]).to eq("unauthorised")
         end
       end
+
+      context "when token with readonly permissions is used for update method" do
+        let(:access_token) { AccessToken.new(owner: "test-owner", permissions: :readonly) }
+
+        before do
+          access_token
+          token
+          access_token.save!
+          post forms_path, params: { form: { name: "Test form" } }, headers: req_headers
+        end
+
+        it "returns 401" do
+          expect(response.status).to eq(401)
+        end
+
+        it "returns an error message" do
+          expect(json_body[:status]).to eq("unauthorised")
+        end
+      end
     end
   end
 end