Enable serving static objects from an external storage

It consists of two parts:

1. Redirecting users to the configured external storage
1. Allowing the external storage to request the static object(s)
   on behalf of the user by means of specific tokens

Part of https://gitlab.com/gitlab-com/gl-infra/infrastructure/issues/6829

app/controllers/concerns/sessionless_authentication.rb

@@ -2,10 +2,10 @@
 
 # == SessionlessAuthentication
 #
-# Controller concern to handle PAT and RSS token authentication methods
+# Controller concern to handle PAT, RSS, and static objects token authentication methods
 #
 module SessionlessAuthentication
-  # This filter handles personal access tokens, and atom requests with rss tokens
+  # This filter handles personal access tokens, atom requests with rss tokens, and static object tokens
   def authenticate_sessionless_user!(request_format)
     user = Gitlab::Auth::RequestAuthenticator.new(request).find_sessionless_user(request_format)
 

app/controllers/concerns/static_object_external_storage.rb

+# frozen_string_literal: true
+
+module StaticObjectExternalStorage
+  extend ActiveSupport::Concern
+
+  included do
+    include ApplicationHelper
+  end
+
+  def redirect_to_external_storage
+    return if external_storage_request?
+
+    redirect_to external_storage_url_or_path(request.fullpath, project)
+  end
+
+  def external_storage_request?
+    header_token = request.headers['X-Gitlab-External-Storage-Token']
+    return false unless header_token.present?
+
+    external_storage_token = Gitlab::CurrentSettings.static_objects_external_storage_auth_token
+    ActiveSupport::SecurityUtils.secure_compare(header_token, external_storage_token) ||
+      raise(Gitlab::Access::AccessDeniedError)
+  end
+end

app/controllers/profiles_controller.rb

@@ -46,6 +46,15 @@ class ProfilesController < Profiles::ApplicationController
     redirect_to profile_personal_access_tokens_path
   end
 
+  def reset_static_object_token
+    Users::UpdateService.new(current_user, user: @user).execute! do |user|
+      user.reset_static_object_token!
+    end
+
+    redirect_to profile_personal_access_tokens_path,
+      notice: s_('Profiles|Static object token was successfully reset')
+  end
+
   # rubocop: disable CodeReuse/ActiveRecord
   def audit_log
     @events = AuditEvent.where(entity_type: "User", entity_id: current_user.id)

app/controllers/projects/repositories_controller.rb

@@ -2,6 +2,9 @@
 
 class Projects::RepositoriesController < Projects::ApplicationController
   include ExtractsPath
+  include StaticObjectExternalStorage
+
+  prepend_before_action(only: [:archive]) { authenticate_sessionless_user!(:archive) }
 
   # Authorize
   before_action :require_non_empty_project, except: :create
@@ -9,6 +12,7 @@ class Projects::RepositoriesController < Projects::ApplicationController
   before_action :assign_append_sha, only: :archive
   before_action :authorize_download_code!
   before_action :authorize_admin_project!, only: :create
+  before_action :redirect_to_external_storage, only: :archive, if: :static_objects_external_storage_enabled?
 
   def create
     @project.create_repository

app/helpers/application_helper.rb

@@ -169,6 +169,25 @@ module ApplicationHelper
     Gitlab::CurrentSettings.current_application_settings.help_page_support_url.presence || promo_url + '/getting-help/'
   end
 
+  def static_objects_external_storage_enabled?
+    Gitlab::CurrentSettings.static_objects_external_storage_enabled?
+  end
+
+  def external_storage_url_or_path(path, project = @project)
+    return path unless static_objects_external_storage_enabled?
+
+    uri = URI(Gitlab::CurrentSettings.static_objects_external_storage_url)
+    path = URI(path) # `path` could have query parameters, so we need to split query and path apart
+
+    query = Rack::Utils.parse_nested_query(path.query)
+    query['token'] = current_user.static_object_token unless project.public?
+
+    uri.path = path.path
+    uri.query = query.to_query unless query.empty?
+
+    uri.to_s
+  end
+
   def page_filter_path(options = {})
     without = options.delete(:without)
 

app/helpers/application_settings_helper.rb

@@ -168,6 +168,8 @@ module ApplicationSettingsHelper
       :asset_proxy_secret_key,
       :asset_proxy_url,
       :asset_proxy_whitelist,
+      :static_objects_external_storage_auth_token,
+      :static_objects_external_storage_url,
       :authorized_keys_enabled,
       :auto_devops_enabled,
       :auto_devops_domain,

app/models/application_setting.rb

@@ -8,6 +8,7 @@ class ApplicationSetting < ApplicationRecord
 
   add_authentication_token_field :runners_registration_token, encrypted: -> { Feature.enabled?(:application_settings_tokens_optional_encryption, default_enabled: true) ? :optional : :required }
   add_authentication_token_field :health_check_access_token
+  add_authentication_token_field :static_objects_external_storage_auth_token
 
   belongs_to :instance_administration_project, class_name: "Project"
 
@@ -211,6 +212,13 @@ class ApplicationSetting < ApplicationRecord
             allow_blank: false,
             if: :asset_proxy_enabled?
 
+  validates :static_objects_external_storage_url,
+            addressable_url: true, allow_blank: true
+
+  validates :static_objects_external_storage_auth_token,
+            presence: true,
+            if: :static_objects_external_storage_url?
+
   SUPPORTED_KEY_TYPES.each do |type|
     validates :"#{type}_key_restriction", presence: true, key_restriction: { type: type }
   end

app/models/application_setting_implementation.rb

@@ -306,6 +306,10 @@ module ApplicationSettingImplementation
     archive_builds_in_seconds.seconds.ago if archive_builds_in_seconds
   end
 
+  def static_objects_external_storage_enabled?
+    static_objects_external_storage_url.present?
+  end
+
   private
 
   def array_to_string(arr)

app/models/user.rb

@@ -31,6 +31,7 @@ class User < ApplicationRecord
 
   add_authentication_token_field :incoming_email_token, token_generator: -> { SecureRandom.hex.to_i(16).to_s(36) }
   add_authentication_token_field :feed_token
+  add_authentication_token_field :static_object_token
 
   default_value_for :admin, false
   default_value_for(:external) { Gitlab::CurrentSettings.user_default_external }
@@ -1437,6 +1438,13 @@ class User < ApplicationRecord
     ensure_feed_token!
   end
 
+  # Each existing user needs to have a `static_object_token`.
+  # We do this on read since migrating all existing users is not a feasible
+  # solution.
+  def static_object_token
+    ensure_static_object_token!
+  end
+
   def sync_attribute?(attribute)
     return true if ldap_user? && attribute == :email
 

app/views/admin/application_settings/_repository_static_objects.html.haml

+= form_for @application_setting, url: repository_admin_application_settings_path(anchor: 'js-repository-static-objects-settings'), html: { class: 'fieldset-form' } do |f|
+  = form_errors(@application_setting)
+
+  %fieldset
+    .form-group
+      = f.label :static_objects_external_storage_url, class: 'label-bold' do
+        = _('External storage URL')
+      = f.text_field :static_objects_external_storage_url, class: 'form-control'
+      %span.form-text.text-muted#static_objects_external_storage_url_help_block
+        = _('URL of the external storage that will serve the repository static objects (e.g. archives, blobs, ...).')
+    .form-group
+      = f.label :static_objects_external_storage_auth_token, class: 'label-bold' do
+        = _('External storage authentication token')
+      = f.text_field :static_objects_external_storage_auth_token, class: 'form-control'
+      %span.form-text.text-muted#static_objects_external_storage_auth_token_help_block
+        = _('A secure token that identifies an external storage request.')
+
+  = f.submit _('Save changes'), class: "btn btn-success"

app/views/admin/application_settings/repository.html.haml

@@ -34,3 +34,14 @@
       = _('Configure automatic git checks and housekeeping on repositories.')
   .settings-content
     = render 'repository_check'
+
+%section.settings.as-repository-static-objects.no-animate#js-repository-static-objects-settings{ class: ('expanded' if expanded_by_default?) }
+  .settings-header
+    %h4
+      = _('Repository static objects')
+    %button.btn.btn-default.js-settings-toggle{ type: 'button' }
+      = expanded_by_default? ? _('Collapse') : _('Expand')
+    %p
+      = _('Serve repository static objects (e.g. archives, blobs, ...) from an external storage (e.g. a CDN).')
+  .settings-content
+    = render 'repository_static_objects'

app/views/profiles/personal_access_tokens/index.html.haml

@@ -54,3 +54,23 @@
         - reset_link = link_to s_('AccessTokens|reset it'), [:reset, :incoming_email_token, :profile], method: :put, data: { confirm: s_('AccessTokens|Are you sure? Any issue email addresses currently in use will stop working.') }
         - reset_message = s_('AccessTokens|Keep this token secret. Anyone who gets ahold of it can create issues as if they were you. You should %{link_reset_it} if that ever happens.') % { link_reset_it: reset_link }
         = reset_message.html_safe
+
+- if static_objects_external_storage_enabled?
+  %hr
+  .row.prepend-top-default
+    .col-lg-4
+      %h4.prepend-top-0
+        = s_('AccessTokens|Static object token')
+      %p
+        = s_('AccessTokens|Your static object token is used to authenticate you when repository static objects (e.g. archives, blobs, ...) are being served from an external storage.')
+      %p
+        = s_('AccessTokens|It cannot be used to access any other data.')
+    .col-lg-8
+      = label_tag :static_object_token, s_('AccessTokens|Static object token'), class: "label-bold"
+      = text_field_tag :static_object_token, current_user.static_object_token, class: 'form-control', readonly: true, onclick: 'this.select()'
+      %p.form-text.text-muted
+        - reset_link = url_for [:reset, :static_object_token, :profile]
+        - reset_link_start = '<a data-confirm="%{confirm}" rel="nofollow" data-method="put" href="%{url}">'.html_safe % { confirm: s_('AccessTokens|Are you sure?'), url: reset_link }
+        - reset_link_end = '</a>'.html_safe
+        - reset_message = s_('AccessTokens|Keep this token secret. Anyone who gets ahold of it can access repository static objects as if they were you. You should %{reset_link_start}reset it%{reset_link_end} if that ever happens.') % { reset_link_start: reset_link_start, reset_link_end: reset_link_end }
+        = reset_message.html_safe

app/views/projects/buttons/_download_links.html.haml

@@ -2,4 +2,5 @@
 
 .btn-group.ml-0.w-100
   - formats.each do |(fmt, extra_class)|
-    = link_to fmt, project_archive_path(project, id: tree_join(ref, archive_prefix), path: path, format: fmt), rel: 'nofollow', download: '', class: "btn btn-xs #{extra_class}"
+    - archive_path = project_archive_path(project, id: tree_join(ref, archive_prefix), path: path, format: fmt)
+    = link_to fmt, external_storage_url_or_path(archive_path), rel: 'nofollow', download: '', class: "btn btn-xs #{extra_class}"

changelogs/unreleased/static-objects-external-storage.yml

+---
+title: Enable serving static objects from an external storage
+merge_request: 31025
+author:
+type: added

config/routes/profile.rb

@@ -8,6 +8,7 @@ resource :profile, only: [:show, :update] do
 
     put :reset_incoming_email_token
     put :reset_feed_token
+    put :reset_static_object_token
     put :update_username
   end
 

db/migrate/20190722104947_add_static_object_token_to_users.rb

+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddStaticObjectTokenToUsers < ActiveRecord::Migration[5.2]
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_column :users, :static_object_token, :string, limit: 255
+  end
+
+  def down
+    remove_column :users, :static_object_token
+  end
+end

db/migrate/20190722132830_add_static_objects_external_storage_columns_to_application_settings.rb

+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddStaticObjectsExternalStorageColumnsToApplicationSettings < ActiveRecord::Migration[5.2]
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  def change
+    add_column :application_settings, :static_objects_external_storage_url, :string, limit: 255
+    add_column :application_settings, :static_objects_external_storage_auth_token, :string, limit: 255
+  end
+end

db/migrate/20190725183432_add_index_to_index_on_static_object_token.rb

+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddIndexToIndexOnStaticObjectToken < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index :users, :static_object_token, unique: true
+  end
+
+  def down
+    remove_concurrent_index :users, :static_object_token
+  end
+end

db/schema.rb

@@ -284,6 +284,8 @@ ActiveRecord::Schema.define(version: 2019_09_05_223900) do
     t.text "asset_proxy_whitelist"
     t.text "encrypted_asset_proxy_secret_key"
     t.string "encrypted_asset_proxy_secret_key_iv"
+    t.string "static_objects_external_storage_url", limit: 255
+    t.string "static_objects_external_storage_auth_token", limit: 255
     t.index ["custom_project_templates_group_id"], name: "index_application_settings_on_custom_project_templates_group_id"
     t.index ["file_template_project_id"], name: "index_application_settings_on_file_template_project_id"
     t.index ["instance_administration_project_id"], name: "index_applicationsettings_on_instance_administration_project_id"
@@ -3548,6 +3550,7 @@ ActiveRecord::Schema.define(version: 2019_09_05_223900) do
     t.integer "bot_type", limit: 2
     t.string "first_name", limit: 255
     t.string "last_name", limit: 255
+    t.string "static_object_token", limit: 255
     t.index ["accepted_term_id"], name: "index_users_on_accepted_term_id"
     t.index ["admin"], name: "index_users_on_admin"
     t.index ["bot_type"], name: "index_users_on_bot_type"
@@ -3567,6 +3570,7 @@ ActiveRecord::Schema.define(version: 2019_09_05_223900) do
     t.index ["state"], name: "index_users_on_state"
     t.index ["state"], name: "index_users_on_state_and_internal", where: "(ghost IS NOT TRUE)"
     t.index ["state"], name: "index_users_on_state_and_internal_ee", where: "((ghost IS NOT TRUE) AND (bot_type IS NULL))"
+    t.index ["static_object_token"], name: "index_users_on_static_object_token", unique: true
     t.index ["unconfirmed_email"], name: "index_users_on_unconfirmed_email", where: "(unconfirmed_email IS NOT NULL)"
     t.index ["username"], name: "index_users_on_username"
     t.index ["username"], name: "index_users_on_username_trigram", opclass: :gin_trgm_ops, using: :gin

doc/administration/index.md

@@ -142,6 +142,7 @@ Learn how to install, configure, update, and maintain your GitLab instance.
 - [Repository storage types](repository_storage_types.md): Information about the different repository storage types.
 - [Repository storage rake tasks](raketasks/storage.md): A collection of rake tasks to list and migrate existing projects and attachments associated with it from Legacy storage to Hashed storage.
 - [Limit repository size](../user/admin_area/settings/account_and_limit_settings.md): Set a hard limit for your repositories' size. **(STARTER ONLY)**
+- [Static objects external storage](static_objects_external_storage.md): Set external storage for static objects in a repository.
 
 ## Continuous Integration settings
 

doc/administration/static_objects_external_storage.md

+# Static objects external storage
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/31025) in GitLab 12.3.
+
+GitLab can be configured to serve repository static objects (for example, archives) from an external
+storage, such as a CDN.
+
+## Configuring
+
+To configure external storage for static objects:
+
+1. Navigate to **Admin Area > Settings > Repository**.
+1. Expand the **Repository static objects** section.
+1. Enter the base URL and an arbitrary token.
+
+The token is required to distinguish requests coming from the external storage, so users don't
+circumvent the external storage and go for the application directly. The token is expected to be
+set in the `X-Gitlab-External-Storage-Token` header in requests originating from the external
+storage.
+
+## Serving private static objects
+
+GitLab will append a user-specific token for static object URLs that belong to private projects,
+so an external storage can be authenticated on behalf of the user. When processing requests originating
+from the external storage, GitLab will look for the token in the `token` query parameter or in
+the `X-Gitlab-Static-Object-Token` header to check the user's ability to access the requested object.
+
+## Requests flow example
+
+The following example shows a sequence of requests and responses between the user,
+GitLab, and the CDN:
+
+```mermaid
+sequenceDiagram
+    User->>GitLab: GET /project/-/archive/master.zip
+    GitLab->>User: 302 Found
+    Note over User,GitLab: Location: https://cdn.com/project/-/archive/master.zip?token=secure-user-token
+    User->>CDN: GET /project/-/archive/master.zip?token=secure-user-token
+    alt object not in cache
+      CDN->>GitLab: GET /project/-/archive/master.zip
+      Note over CDN,GitLab: X-Gitlab-External-Storage-Token: secure-cdn-token<br/>X-Gitlab-Static-Object-Token: secure-user-token
+      GitLab->>CDN: 200 OK
+      CDN->>User: master.zip
+    else object in cache
+      CDN->>GitLab: GET /project/-/archive/master.zip
+      Note over CDN,GitLab: X-Gitlab-External-Storage-Token: secure-cdn-token<br/>X-Gitlab-Static-Object-Token: secure-user-token<br/>If-None-Match: etag-value
+      GitLab->>CDN: 304 Not Modified
+      CDN->>User: master.zip
+    end
+```

lib/gitlab/auth/request_authenticator.rb

@@ -24,7 +24,9 @@ module Gitlab
       end
 
       def find_sessionless_user(request_format)
-        find_user_from_web_access_token(request_format) || find_user_from_feed_token(request_format)
+        find_user_from_web_access_token(request_format) ||
+          find_user_from_feed_token(request_format) ||
+          find_user_from_static_object_token(request_format)
       rescue Gitlab::Auth::AuthenticationError
         nil
       end

lib/gitlab/auth/user_auth_finders.rb

@@ -28,6 +28,15 @@ module Gitlab
         current_request.env['warden']&.authenticate if verified_request?
       end
 
+      def find_user_from_static_object_token(request_format)
+        return unless valid_static_objects_format?(request_format)
+
+        token = current_request.params[:token].presence || current_request.headers['X-Gitlab-Static-Object-Token'].presence
+        return unless token
+
+        User.find_by_static_object_token(token) || raise(UnauthorizedError)
+      end
+
       def find_user_from_feed_token(request_format)
         return unless valid_rss_format?(request_format)
 
@@ -154,6 +163,15 @@ module Gitlab
         end
       end
 
+      def valid_static_objects_format?(request_format)
+        case request_format
+        when :archive
+          archive_request?
+        else
+          false
+        end
+      end
+
       def rss_request?
         current_request.path.ends_with?('.atom') || current_request.format.atom?
       end
@@ -165,6 +183,10 @@ module Gitlab
       def api_request?
         current_request.path.starts_with?("/api/")
       end
+
+      def archive_request?
+        current_request.path.include?('/-/archive/')
+      end
     end
   end
 end

locale/gitlab.pot

@@ -517,6 +517,9 @@ msgstr ""
 msgid "A regular expression that will be used to find the test coverage output in the job trace. Leave blank to disable"
 msgstr ""
 
+msgid "A secure token that identifies an external storage request."
+msgstr ""
+
 msgid "A user with write access to the source branch selected this option"
 msgstr ""
 
@@ -568,6 +571,9 @@ msgstr ""
 msgid "AccessTokens|Access Tokens"
 msgstr ""
 
+msgid "AccessTokens|Are you sure?"
+msgstr ""
+
 msgid "AccessTokens|Are you sure? Any RSS or calendar URLs currently in use will stop working."
 msgstr ""
 
@@ -586,6 +592,9 @@ msgstr ""
 msgid "AccessTokens|It cannot be used to access any other data."
 msgstr ""
 
+msgid "AccessTokens|Keep this token secret. Anyone who gets ahold of it can access repository static objects as if they were you. You should %{reset_link_start}reset it%{reset_link_end} if that ever happens."
+msgstr ""
+
 msgid "AccessTokens|Keep this token secret. Anyone who gets ahold of it can create issues as if they were you. You should %{link_reset_it} if that ever happens."
 msgstr ""
 
@@ -595,6 +604,9 @@ msgstr ""
 msgid "AccessTokens|Personal Access Tokens"
 msgstr ""
 
+msgid "AccessTokens|Static object token"
+msgstr ""
+
 msgid "AccessTokens|They are the only accepted password when you have Two-Factor Authentication (2FA) enabled."
 msgstr ""
 
@@ -610,6 +622,9 @@ msgstr ""
 msgid "AccessTokens|Your incoming email token is used to authenticate you when you create a new issue by email, and is included in your personal project-specific email addresses."
 msgstr ""
 
+msgid "AccessTokens|Your static object token is used to authenticate you when repository static objects (e.g. archives, blobs, ...) are being served from an external storage."
+msgstr ""
+
 msgid "AccessTokens|reset it"
 msgstr ""
 
@@ -4852,6 +4867,12 @@ msgstr ""
 msgid "External authorization request timeout"
 msgstr ""
 
+msgid "External storage URL"
+msgstr ""
+
+msgid "External storage authentication token"
+msgstr ""
+
 msgid "ExternalAuthorizationService|Classification label"
 msgstr ""
 
@@ -8668,6 +8689,9 @@ msgstr ""
 msgid "Profiles|Some options are unavailable for LDAP accounts"
 msgstr ""
 
+msgid "Profiles|Static object token was successfully reset"
+msgstr ""
+
 msgid "Profiles|Tell us about yourself in fewer than 250 characters"
 msgstr ""
 
@@ -9693,6 +9717,9 @@ msgstr ""
 msgid "Repository mirror"
 msgstr ""
 
+msgid "Repository static objects"
+msgstr ""
+
 msgid "Repository storage"
 msgstr ""
 
@@ -10244,6 +10271,9 @@ msgstr ""
 msgid "September"
 msgstr ""
 
+msgid "Serve repository static objects (e.g. archives, blobs, ...) from an external storage (e.g. a CDN)."
+msgstr ""
+
 msgid "Server supports batch API only, please update your Git LFS client to version 1.0.1 and up."
 msgstr ""
 
@@ -12421,6 +12451,9 @@ msgstr ""
 msgid "U2F only works with HTTPS-enabled websites. Contact your administrator for more details."
 msgstr ""
 
+msgid "URL of the external storage that will serve the repository static objects (e.g. archives, blobs, ...)."
+msgstr ""
+
 msgid "Unable to apply suggestions to a deleted line."
 msgstr ""
 

spec/controllers/concerns/static_object_external_storage_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe StaticObjectExternalStorage do
+  controller(Projects::ApplicationController) do
+    include StaticObjectExternalStorage # rubocop:disable RSpec/DescribedClass
+
+    before_action :redirect_to_external_storage, if: :static_objects_external_storage_enabled?
+
+    def show
+      head :ok
+    end
+  end
+
+  let(:project) { create(:project, :public) }
+  let(:user) { create(:user, static_object_token: 'hunter1') }
+
+  before do
+    project.add_developer(user)
+    sign_in(user)
+  end
+
+  context 'when external storage is not configured' do
+    it 'calls the action normally' do
+      expect(Gitlab::CurrentSettings.static_objects_external_storage_url).to be_blank
+
+      do_request
+
+      expect(response).to have_gitlab_http_status(200)
+    end
+  end
+
+  context 'when external storage is configured' do
+    before do
+      allow_any_instance_of(ApplicationSetting).to receive(:static_objects_external_storage_url).and_return('https://cdn.gitlab.com')
+      allow_any_instance_of(ApplicationSetting).to receive(:static_objects_external_storage_auth_token).and_return('letmein')
+
+      routes.draw { get '/:namespace_id/:id' => 'projects/application#show' }
+    end
+
+    context 'when external storage token is empty' do
+      let(:base_redirect_url) { "https://cdn.gitlab.com/#{project.namespace.to_param}/#{project.to_param}" }
+
+      context 'when project is public' do
+        it 'redirects to external storage URL without adding a token parameter' do
+          do_request
+
+          expect(response).to redirect_to(base_redirect_url)
+        end
+      end
+
+      context 'when project is not public' do
+        let(:project) { create(:project, :private) }
+
+        it 'redirects to external storage URL a token parameter added' do
+          do_request
+
+          expect(response).to redirect_to("#{base_redirect_url}?token=#{user.static_object_token}")
+        end
+
+        context 'when path includes extra parameters' do
+          it 'includes the parameters in the redirect URL' do
+            do_request(foo: 'bar')
+
+            expect(response.location).to eq("#{base_redirect_url}?foo=bar&token=#{user.static_object_token}")
+          end
+        end
+      end
+    end
+
+    context 'when external storage token is present' do
+      context 'when token is correct' do
+        it 'calls the action normally' do
+          request.headers['X-Gitlab-External-Storage-Token'] = 'letmein'
+          do_request
+
+          expect(response).to have_gitlab_http_status(200)
+        end
+      end
+
+      context 'when token is incorrect' do
+        it 'return 403' do
+          request.headers['X-Gitlab-External-Storage-Token'] = 'donotletmein'
+          do_request
+
+          expect(response).to have_gitlab_http_status(403)
+        end
+      end
+    end
+  end
+
+  def do_request(extra_params = {})
+    get :show, params: { namespace_id: project.namespace, id: project }.merge(extra_params)
+  end
+end

spec/controllers/projects/repositories_controller_spec.rb

@@ -125,5 +125,59 @@ describe Projects::RepositoriesController do
         end
       end
     end
+
+    context 'as a sessionless user' do
+      let(:user) { create(:user) }
+
+      before do
+        project.add_developer(user)
+      end
+
+      context 'when no token is provided' do
+        it 'redirects to sign in page' do
+          get :archive, params: { namespace_id: project.namespace, project_id: project, id: 'master' }, format: 'zip'
+
+          expect(response).to have_gitlab_http_status(302)
+        end
+      end
+
+      context 'when a token param is present' do
+        context 'when token is correct' do
+          it 'calls the action normally' do
+            get :archive, params: { namespace_id: project.namespace, project_id: project, id: 'master', token: user.static_object_token }, format: 'zip'
+
+            expect(response).to have_gitlab_http_status(200)
+          end
+        end
+
+        context 'when token is incorrect' do
+          it 'redirects to sign in page' do
+            get :archive, params: { namespace_id: project.namespace, project_id: project, id: 'master', token: 'foobar' }, format: 'zip'
+
+            expect(response).to have_gitlab_http_status(302)
+          end
+        end
+      end
+
+      context 'when a token header is present' do
+        context 'when token is correct' do
+          it 'calls the action normally' do
+            request.headers['X-Gitlab-Static-Object-Token'] = user.static_object_token
+            get :archive, params: { namespace_id: project.namespace, project_id: project, id: 'master' }, format: 'zip'
+
+            expect(response).to have_gitlab_http_status(200)
+          end
+        end
+
+        context 'when token is incorrect' do
+          it 'redirects to sign in page' do
+            request.headers['X-Gitlab-Static-Object-Token'] = 'foobar'
+            get :archive, params: { namespace_id: project.namespace, project_id: project, id: 'master' }, format: 'zip'
+
+            expect(response).to have_gitlab_http_status(302)
+          end
+        end
+      end
+    end
   end
 end

spec/features/projects/branches/download_buttons_spec.rb

@@ -29,6 +29,11 @@ describe 'Download buttons in branches page' do
   end
 
   describe 'when checking branches' do
+    it_behaves_like 'archive download buttons' do
+      let(:ref) { 'binary-encoding' }
+      let(:path_to_visit) { project_branches_filtered_path(project, state: 'all', search: ref) }
+    end
+
     context 'with artifacts' do
       before do
         visit project_branches_filtered_path(project, state: 'all', search: 'binary-encoding')

spec/features/projects/files/download_buttons_spec.rb

@@ -24,11 +24,17 @@ describe 'Projects > Files > Download buttons in files tree' do
   before do
     sign_in(user)
     project.add_developer(user)
+  end
 
-    visit project_tree_path(project, project.default_branch)
+  it_behaves_like 'archive download buttons' do
+    let(:path_to_visit) { project_tree_path(project, project.default_branch) }
   end
 
   context 'with artifacts' do
+    before do
+      visit project_tree_path(project, project.default_branch)
+    end
+
     it 'shows download artifacts button' do
       href = latest_succeeded_project_artifacts_path(project, "#{project.default_branch}/download", job: 'build')
 

spec/features/projects/show/download_buttons_spec.rb

@@ -29,6 +29,8 @@ describe 'Projects > Show > Download buttons' do
   end
 
   describe 'when checking project main page' do
+    it_behaves_like 'archive download buttons'
+
     context 'with artifacts' do
       before do
         visit project_path(project)

spec/features/projects/tags/download_buttons_spec.rb

@@ -30,6 +30,11 @@ describe 'Download buttons in tags page' do
   end
 
   describe 'when checking tags' do
+    it_behaves_like 'archive download buttons' do
+      let(:path_to_visit) { project_tags_path(project) }
+      let(:ref) { tag }
+    end
+
     context 'with artifacts' do
       before do
         visit project_tags_path(project)

spec/helpers/application_helper_spec.rb

@@ -195,4 +195,41 @@ describe ApplicationHelper do
       end
     end
   end
+
+  describe '#external_storage_url_or_path' do
+    let(:project) { create(:project) }
+
+    context 'when external storage is disabled' do
+      it 'returns the passed path' do
+        expect(helper.external_storage_url_or_path('/foo/bar', project)).to eq('/foo/bar')
+      end
+    end
+
+    context 'when external storage is enabled' do
+      let(:user) { create(:user, static_object_token: 'hunter1') }
+
+      before do
+        allow_any_instance_of(ApplicationSetting).to receive(:static_objects_external_storage_url).and_return('https://cdn.gitlab.com')
+        allow(helper).to receive(:current_user).and_return(user)
+      end
+
+      it 'returns the external storage URL prepended to the path' do
+        expect(helper.external_storage_url_or_path('/foo/bar', project)).to eq("https://cdn.gitlab.com/foo/bar?token=#{user.static_object_token}")
+      end
+
+      it 'preserves the path query parameters' do
+        url = helper.external_storage_url_or_path('/foo/bar?unicode=1', project)
+
+        expect(url).to eq("https://cdn.gitlab.com/foo/bar?token=#{user.static_object_token}&unicode=1")
+      end
+
+      context 'when project is public' do
+        let(:project) { create(:project, :public) }
+
+        it 'returns does not append a token parameter' do
+          expect(helper.external_storage_url_or_path('/foo/bar', project)).to eq('https://cdn.gitlab.com/foo/bar')
+        end
+      end
+    end
+  end
 end

spec/lib/gitlab/auth/user_auth_finders_spec.rb

@@ -115,6 +115,60 @@ describe Gitlab::Auth::UserAuthFinders do
     end
   end
 
+  describe '#find_user_from_static_object_token' do
+    context 'when request format is archive' do
+      before do
+        env['SCRIPT_NAME'] = 'project/-/archive/master.zip'
+      end
+
+      context 'when token header param is present' do
+        context 'when token is correct' do
+          it 'returns the user' do
+            request.headers['X-Gitlab-Static-Object-Token'] = user.static_object_token
+
+            expect(find_user_from_static_object_token(:archive)).to eq(user)
+          end
+        end
+
+        context 'when token is incorrect' do
+          it 'returns the user' do
+            request.headers['X-Gitlab-Static-Object-Token'] = 'foobar'
+
+            expect { find_user_from_static_object_token(:archive) }.to raise_error(Gitlab::Auth::UnauthorizedError)
+          end
+        end
+      end
+
+      context 'when token query param is present' do
+        context 'when token is correct' do
+          it 'returns the user' do
+            set_param(:token, user.static_object_token)
+
+            expect(find_user_from_static_object_token(:archive)).to eq(user)
+          end
+        end
+
+        context 'when token is incorrect' do
+          it 'returns the user' do
+            set_param(:token, 'foobar')
+
+            expect { find_user_from_static_object_token(:archive) }.to raise_error(Gitlab::Auth::UnauthorizedError)
+          end
+        end
+      end
+    end
+
+    context 'when request format is not archive' do
+      before do
+        env['script_name'] = 'url'
+      end
+
+      it 'returns nil' do
+        expect(find_user_from_static_object_token(:foo)).to be_nil
+      end
+    end
+  end
+
   describe '#find_user_from_access_token' do
     let(:personal_access_token) { create(:personal_access_token, user: user) }
 

spec/models/application_setting_spec.rb

@@ -48,6 +48,10 @@ describe ApplicationSetting do
     it { is_expected.not_to allow_value(nil).for(:outbound_local_requests_whitelist) }
     it { is_expected.to allow_value([]).for(:outbound_local_requests_whitelist) }
 
+    it { is_expected.to allow_value(nil).for(:static_objects_external_storage_url) }
+    it { is_expected.to allow_value(http).for(:static_objects_external_storage_url) }
+    it { is_expected.to allow_value(https).for(:static_objects_external_storage_url) }
+
     context "when user accepted let's encrypt terms of service" do
       before do
         setting.update(lets_encrypt_terms_of_service_accepted: true)
@@ -420,6 +424,16 @@ describe ApplicationSetting do
         end
       end
     end
+
+    context 'static objects external storage' do
+      context 'when URL is set' do
+        before do
+          subject.static_objects_external_storage_url = http
+        end
+
+        it { is_expected.not_to allow_value(nil).for(:static_objects_external_storage_auth_token) }
+      end
+    end
   end
 
   context 'restrict creating duplicates' do

spec/models/user_spec.rb

@@ -945,6 +945,16 @@ describe User do
     end
   end
 
+  describe 'static object token' do
+    it 'ensures a static object token on read' do
+      user = create(:user, static_object_token: nil)
+      static_object_token = user.static_object_token
+
+      expect(static_object_token).not_to be_blank
+      expect(user.reload.static_object_token).to eq static_object_token
+    end
+  end
+
   describe '#recently_sent_password_reset?' do
     it 'is false when reset_password_sent_at is nil' do
       user = build_stubbed(:user, reset_password_sent_at: nil)

spec/support/shared_examples/features/archive_download_buttons_shared_examples.rb

+# frozen_string_literal: true
+
+shared_examples 'archive download buttons' do
+  let(:formats) { %w(zip tar.gz tar.bz2 tar) }
+  let(:path_to_visit) { project_path(project) }
+  let(:ref) { project.default_branch }
+
+  context 'when static objects external storage is enabled' do
+    before do
+      allow_any_instance_of(ApplicationSetting).to receive(:static_objects_external_storage_url).and_return('https://cdn.gitlab.com')
+      visit path_to_visit
+    end
+
+    context 'private project' do
+      it 'shows archive download buttons with external storage URL prepended and user token appended to their href' do
+        formats.each do |format|
+          path = archive_path(project, ref, format)
+          uri = URI('https://cdn.gitlab.com')
+          uri.path = path
+          uri.query = "token=#{user.static_object_token}"
+
+          expect(page).to have_link format, href: uri.to_s
+        end
+      end
+    end
+
+    context 'public project' do
+      let(:project) { create(:project, :repository, :public) }
+
+      it 'shows archive download buttons with external storage URL prepended to their href' do
+        formats.each do |format|
+          path = archive_path(project, ref, format)
+          uri = URI('https://cdn.gitlab.com')
+          uri.path = path
+
+          expect(page).to have_link format, href: uri.to_s
+        end
+      end
+    end
+  end
+
+  context 'when static objects external storage is disabled' do
+    before do
+      visit path_to_visit
+    end
+
+    it 'shows default archive download buttons' do
+      formats.each do |format|
+        path = archive_path(project, ref, format)
+
+        expect(page).to have_link format, href: path
+      end
+    end
+  end
+
+  def archive_path(project, ref, format)
+    project_archive_path(project, id: "#{ref}/#{project.path}-#{ref}", path: nil, format: format)
+  end
+end