HTTP signatures (#4146)

* Add Request class with HTTP signature generator

Spec: https://tools.ietf.org/html/draft-cavage-http-signatures-06

* Add HTTP signature verification concern

* Add test for SignatureVerification concern

* Add basic test for Request class

* Make PuSH subscribe/unsubscribe requests use new Request class

Accidentally fix lease_seconds not being set and sent properly, and
change the new minimum subscription duration to 1 day

* Make all PuSH workers use new Request class

* Make Salmon sender use new Request class

* Make FetchLinkService use new Request class

* Make FetchAtomService use the new Request class

* Make Remotable use the new Request class

* Make ResolveRemoteAccountService use the new Request class

* Add more tests

* Allow +-30 seconds window for signed request to remain valid

* Disable time window validation for signed requests, restore 7 days
as PuSH subscription duration (which was previous default due to a bug)

18 files changed, 249 insertions, 75 deletions

diff --git a/app/controllers/accounts_controller.rb b/app/controllers/accounts_controller.rb
index 11402ab79..69b520df1 100644
--- a/app/controllers/accounts_controller.rb
+++ b/app/controllers/accounts_controller.rb
@@ -2,6 +2,7 @@
 
 class AccountsController < ApplicationController
   include AccountControllerConcern
+  include SignatureVerification
 
   def show
     respond_to do |format|
diff --git a/app/controllers/api/subscriptions_controller.rb b/app/controllers/api/subscriptions_controller.rb
index d3ea98676..89007f3d6 100644
--- a/app/controllers/api/subscriptions_controller.rb
+++ b/app/controllers/api/subscriptions_controller.rb
@@ -42,7 +42,7 @@ class Api::SubscriptionsController < Api::BaseController
   end
 
   def lease_seconds_or_default
-    (params['hub.lease_seconds'] || 86_400).to_i.seconds
+    (params['hub.lease_seconds'] || 1.day).to_i.seconds
   end
 
   def set_account
diff --git a/app/controllers/concerns/signature_verification.rb b/app/controllers/concerns/signature_verification.rb
new file mode 100644
index 000000000..abe845d93
--- /dev/null
+++ b/app/controllers/concerns/signature_verification.rb
@@ -0,0 +1,87 @@
+# frozen_string_literal: true
+
+# Implemented according to HTTP signatures (Draft 6)
+# <https://tools.ietf.org/html/draft-cavage-http-signatures-06>
+module SignatureVerification
+  extend ActiveSupport::Concern
+
+  def signed_request?
+    request.headers['Signature'].present?
+  end
+
+  def signed_request_account
+    return @signed_request_account if defined?(@signed_request_account)
+
+    unless signed_request?
+      @signed_request_account = nil
+      return
+    end
+
+    raw_signature    = request.headers['Signature']
+    signature_params = {}
+
+    raw_signature.split(',').each do |part|
+      parsed_parts = part.match(/([a-z]+)="([^"]+)"/i)
+      next if parsed_parts.nil? || parsed_parts.size != 3
+      signature_params[parsed_parts[1]] = parsed_parts[2]
+    end
+
+    if incompatible_signature?(signature_params)
+      @signed_request_account = nil
+      return
+    end
+
+    account = ResolveRemoteAccountService.new.call(signature_params['keyId'].gsub(/\Aacct:/, ''))
+
+    if account.nil?
+      @signed_request_account = nil
+      return
+    end
+
+    signature             = Base64.decode64(signature_params['signature'])
+    compare_signed_string = build_signed_string(signature_params['headers'])
+
+    if account.keypair.public_key.verify(OpenSSL::Digest::SHA256.new, signature, compare_signed_string)
+      @signed_request_account = account
+      @signed_request_account
+    else
+      @signed_request_account = nil
+    end
+  end
+
+  private
+
+  def build_signed_string(signed_headers)
+    signed_headers = 'date' if signed_headers.blank?
+
+    signed_headers.split(' ').map do |signed_header|
+      if signed_header == Request::REQUEST_TARGET
+        "#{Request::REQUEST_TARGET}: #{request.method.downcase} #{request.path}"
+      else
+        "#{signed_header}: #{request.headers[to_header_name(signed_header)]}"
+      end
+    end.join("\n")
+  end
+
+  def matches_time_window?
+    begin
+      time_sent = DateTime.httpdate(request.headers['Date'])
+    rescue ArgumentError
+      return false
+    end
+
+    (Time.now.utc - time_sent).abs <= 30
+  end
+
+  def to_header_name(name)
+    name.split(/-/).map(&:capitalize).join('-')
+  end
+
+  def incompatible_signature?(signature_params)
+    signature_params['keyId'].blank? ||
+      signature_params['signature'].blank? ||
+      signature_params['algorithm'].blank? ||
+      signature_params['algorithm'] != 'rsa-sha256' ||
+      !signature_params['keyId'].start_with?('acct:')
+  end
+end
diff --git a/app/controllers/stream_entries_controller.rb b/app/controllers/stream_entries_controller.rb
index 314d59619..54a435238 100644
--- a/app/controllers/stream_entries_controller.rb
+++ b/app/controllers/stream_entries_controller.rb
@@ -2,6 +2,7 @@
 
 class StreamEntriesController < ApplicationController
   include Authorization
+  include SignatureVerification
 
   layout 'public'
 
diff --git a/app/helpers/http_helper.rb b/app/helpers/http_helper.rb
deleted file mode 100644
index e39a52da0..000000000
--- a/app/helpers/http_helper.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-# frozen_string_literal: true
-
-module HttpHelper
-  def http_client(options = {})
-    timeout = { write: 10, connect: 10, read: 10 }.merge(options)
-
-    HTTP.headers(user_agent: user_agent)
-        .timeout(:per_operation, timeout)
-        .follow
-  end
-
-  private
-
-  def user_agent
-    @user_agent ||= "#{HTTP::Request::USER_AGENT} (Mastodon/#{Mastodon::Version}; +http://#{Rails.configuration.x.local_domain}/)"
-  end
-end
diff --git a/app/lib/provider_discovery.rb b/app/lib/provider_discovery.rb
index 6d48cae2f..5e02e6806 100644
--- a/app/lib/provider_discovery.rb
+++ b/app/lib/provider_discovery.rb
@@ -1,11 +1,9 @@
 # frozen_string_literal: true
 
 class ProviderDiscovery < OEmbed::ProviderDiscovery
-  extend HttpHelper
-
   class << self
     def discover_provider(url, options = {})
-      res    = http_client.get(url)
+      res    = Request.new(:get, url).perform
       format = options[:format]
 
       raise OEmbed::NotFound, url if res.code != 200 || res.mime_type != 'text/html'
diff --git a/app/lib/request.rb b/app/lib/request.rb
new file mode 100644
index 000000000..e73c5ac20
--- /dev/null
+++ b/app/lib/request.rb
@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+class Request
+  REQUEST_TARGET = '(request-target)'
+
+  include RoutingHelper
+
+  def initialize(verb, url, options = {})
+    @verb    = verb
+    @url     = Addressable::URI.parse(url).normalize
+    @options = options
+    @headers = {}
+
+    set_common_headers!
+  end
+
+  def on_behalf_of(account)
+    raise ArgumentError unless account.local?
+    @account = account
+  end
+
+  def add_headers(new_headers)
+    @headers.merge!(new_headers)
+  end
+
+  def perform
+    http_client.headers(headers).public_send(@verb, @url.to_s, @options)
+  end
+
+  def headers
+    (@account ? @headers.merge('Signature' => signature) : @headers).without(REQUEST_TARGET)
+  end
+
+  private
+
+  def set_common_headers!
+    @headers[REQUEST_TARGET] = "#{@verb} #{@url.path}"
+    @headers['User-Agent']   = user_agent
+    @headers['Host']         = @url.host
+    @headers['Date']         = Time.now.utc.httpdate
+  end
+
+  def signature
+    key_id    = @account.to_webfinger_s
+    algorithm = 'rsa-sha256'
+    signature = Base64.strict_encode64(@account.keypair.sign(OpenSSL::Digest::SHA256.new, signed_string))
+
+    "keyId=\"#{key_id}\",algorithm=\"#{algorithm}\",headers=\"#{signed_headers}\",signature=\"#{signature}\""
+  end
+
+  def signed_string
+    @headers.map { |key, value| "#{key.downcase}: #{value}" }.join("\n")
+  end
+
+  def signed_headers
+    @headers.keys.join(' ').downcase
+  end
+
+  def user_agent
+    @user_agent ||= "#{HTTP::Request::USER_AGENT} (Mastodon/#{Mastodon::Version}; +#{root_url})"
+  end
+
+  def timeout
+    { write: 10, connect: 10, read: 10 }
+  end
+
+  def http_client
+    HTTP.timeout(:per_operation, timeout).follow
+  end
+end
diff --git a/app/models/account.rb b/app/models/account.rb
index 7243cb1a5..58b0a1086 100644
--- a/app/models/account.rb
+++ b/app/models/account.rb
@@ -130,7 +130,7 @@ class Account < ApplicationRecord
   end
 
   def subscription(webhook_url)
-    OStatus2::Subscription.new(remote_url, secret: secret, lease_seconds: 86_400 * 30, webhook: webhook_url, hub: hub_url)
+    OStatus2::Subscription.new(remote_url, secret: secret, lease_seconds: 30.days.seconds, webhook: webhook_url, hub: hub_url)
   end
 
   def save_with_optional_media!
diff --git a/app/models/concerns/remotable.rb b/app/models/concerns/remotable.rb
index b4f169649..1bd87a642 100644
--- a/app/models/concerns/remotable.rb
+++ b/app/models/concerns/remotable.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 module Remotable
-  include HttpHelper
   extend ActiveSupport::Concern
 
   included do
@@ -20,7 +19,7 @@ module Remotable
         return if !%w(http https).include?(parsed_url.scheme) || parsed_url.host.empty? || self[attribute_name] == url
 
         begin
-          response = http_client.get(url)
+          response = Request.new(:get, url).perform
 
           return if response.code != 200
 
diff --git a/app/models/subscription.rb b/app/models/subscription.rb
index 35a228df0..d9d5024a9 100644
--- a/app/models/subscription.rb
+++ b/app/models/subscription.rb
@@ -16,8 +16,8 @@
 #
 
 class Subscription < ApplicationRecord
-  MIN_EXPIRATION = 7.days.seconds.to_i
-  MAX_EXPIRATION = 30.days.seconds.to_i
+  MIN_EXPIRATION = 1.day.to_i
+  MAX_EXPIRATION = 30.days.to_i
 
   belongs_to :account, required: true
 
diff --git a/app/services/fetch_atom_service.rb b/app/services/fetch_atom_service.rb
index d430b22e9..3ac441e3e 100644
--- a/app/services/fetch_atom_service.rb
+++ b/app/services/fetch_atom_service.rb
@@ -1,16 +1,14 @@
 # frozen_string_literal: true
 
 class FetchAtomService < BaseService
-  include HttpHelper
-
   def call(url)
     return if url.blank?
 
-    response = http_client.head(url)
+    response = Request.new(:head, url).perform
 
     Rails.logger.debug "Remote status HEAD request returned code #{response.code}"
 
-    response = http_client.get(url) if response.code == 405
+    response = Request.new(:get, url).perform if response.code == 405
 
     Rails.logger.debug "Remote status GET request returned code #{response.code}"
 
@@ -49,6 +47,6 @@ class FetchAtomService < BaseService
   end
 
   def fetch(url)
-    http_client.get(url).to_s
+    Request.new(:get, url).perform.to_s
   end
 end
diff --git a/app/services/fetch_link_card_service.rb b/app/services/fetch_link_card_service.rb
index 6ef3abb66..20c85e0ea 100644
--- a/app/services/fetch_link_card_service.rb
+++ b/app/services/fetch_link_card_service.rb
@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
 class FetchLinkCardService < BaseService
-  include HttpHelper
-
   URL_PATTERN = %r{https?://\S+}
 
   def call(status)
@@ -13,7 +11,7 @@ class FetchLinkCardService < BaseService
 
     url  = url.to_s
     card = PreviewCard.where(status: status).first_or_initialize(status: status, url: url)
-    res  = http_client.head(url)
+    res  = Request.new(:head, url).perform
 
     return if res.code != 200 || res.mime_type != 'text/html'
 
@@ -80,7 +78,7 @@ class FetchLinkCardService < BaseService
   end
 
   def attempt_opengraph(card, url)
-    response = http_client.get(url)
+    response = Request.new(:get, url).perform
 
     return if response.code != 200 || response.mime_type != 'text/html'
 
diff --git a/app/services/resolve_remote_account_service.rb b/app/services/resolve_remote_account_service.rb
index 362d0df98..d2dfda824 100644
--- a/app/services/resolve_remote_account_service.rb
+++ b/app/services/resolve_remote_account_service.rb
@@ -2,7 +2,6 @@
 
 class ResolveRemoteAccountService < BaseService
   include OStatus2::MagicKey
-  include HttpHelper
 
   DFRN_NS = 'http://purl.org/macgirvin/dfrn/1.0'
 
@@ -79,7 +78,7 @@ class ResolveRemoteAccountService < BaseService
   end
 
   def get_feed(url)
-    response = http_client(write: 20, connect: 20, read: 50).get(Addressable::URI.parse(url).normalize)
+    response = Request.new(:get, url).perform
     raise Goldfinger::Error, "Feed attempt failed for #{url}: HTTP #{response.code}" unless response.code == 200
     [response.to_s, Nokogiri::XML(response)]
   end
diff --git a/app/services/send_interaction_service.rb b/app/services/send_interaction_service.rb
index 34c8f9e34..ef38a748b 100644
--- a/app/services/send_interaction_service.rb
+++ b/app/services/send_interaction_service.rb
@@ -12,13 +12,23 @@ class SendInteractionService < BaseService
 
     return if block_notification?
 
-    envelope = salmon.pack(@xml, @source_account.keypair)
-    delivery = salmon.post(@target_account.salmon_url, envelope)
+    delivery = build_request.perform
+
     raise "Delivery failed for #{target_account.salmon_url}: HTTP #{delivery.code}" unless delivery.code > 199 && delivery.code < 300
   end
 
   private
 
+  def build_request
+    request = Request.new(:post, @target_account.salmon_url, body: envelope)
+    request.add_headers('Content-Type' => 'application/magic-envelope+xml')
+    request
+  end
+
+  def envelope
+    salmon.pack(@xml, @source_account.keypair)
+  end
+
   def block_notification?
     DomainBlock.blocked?(@target_account.domain)
   end
diff --git a/app/services/subscribe_service.rb b/app/services/subscribe_service.rb
index 1e7984a7f..f58067038 100644
--- a/app/services/subscribe_service.rb
+++ b/app/services/subscribe_service.rb
@@ -2,34 +2,54 @@
 
 class SubscribeService < BaseService
   def call(account)
-    account.secret = SecureRandom.hex
+    @account        = account
+    @account.secret = SecureRandom.hex
+    @response       = build_request.perform
 
-    subscription = account.subscription(api_subscription_url(account.id))
-    response     = subscription.subscribe
-
-    if response_failed_permanently?(response)
+    if response_failed_permanently?
       # We're not allowed to subscribe. Fail and move on.
-      account.secret = ''
-      account.save!
-    elsif response_successful?(response)
+      @account.secret = ''
+      @account.save!
+    elsif response_successful?
       # The subscription will be confirmed asynchronously.
-      account.save!
+      @account.save!
     else
       # The response was either a 429 rate limit, or a 5xx error.
       # We need to retry at a later time. Fail loudly!
-      raise "Subscription attempt failed for #{account.acct} (#{account.hub_url}): HTTP #{response.code}"
+      raise "Subscription attempt failed for #{@account.acct} (#{@account.hub_url}): HTTP #{@response.code}"
     end
   end
 
   private
 
+  def build_request
+    request = Request.new(:post, @account.hub_url, form: subscription_params)
+    request.on_behalf_of(some_local_account) if some_local_account
+    request
+  end
+
+  def subscription_params
+    {
+      'hub.topic': @account.remote_url,
+      'hub.mode': 'subscribe',
+      'hub.callback': api_subscription_url(@account.id),
+      'hub.verify': 'async',
+      'hub.secret': @account.secret,
+      'hub.lease_seconds': 7.days.seconds,
+    }
+  end
+
+  def some_local_account
+    @some_local_account ||= Account.local.first
+  end
+
   # Any response in the 3xx or 4xx range, except for 429 (rate limit)
-  def response_failed_permanently?(response)
-    (response.status.redirect? || response.status.client_error?) && !response.status.too_many_requests?
+  def response_failed_permanently?
+    (@response.status.redirect? || @response.status.client_error?) && !@response.status.too_many_requests?
   end
 
   # Any response in the 2xx range
-  def response_successful?(response)
-    response.status.success?
+  def response_successful?
+    @response.status.success?
   end
 end
diff --git a/app/services/unsubscribe_service.rb b/app/services/unsubscribe_service.rb
index 6db8dbdc4..c2f022d7d 100644
--- a/app/services/unsubscribe_service.rb
+++ b/app/services/unsubscribe_service.rb
@@ -2,17 +2,30 @@
 
 class UnsubscribeService < BaseService
   def call(account)
-    subscription = account.subscription(api_subscription_url(account.id))
-    response = subscription.unsubscribe
+    @account  = account
+    @response = build_request.perform
 
-    unless response.status.success?
-      Rails.logger.debug "PuSH unsubscribe for #{account.acct} failed: #{response.status}"
-    end
+    Rails.logger.debug "PuSH unsubscribe for #{@account.acct} failed: #{@response.status}" unless @response.status.success?
 
-    account.secret = ''
-    account.subscription_expires_at = nil
-    account.save!
+    @account.secret = ''
+    @account.subscription_expires_at = nil
+    @account.save!
   rescue HTTP::Error, OpenSSL::SSL::SSLError
-    Rails.logger.debug "PuSH subscription request for #{account.acct} could not be made due to HTTP or SSL error"
+    Rails.logger.debug "PuSH subscription request for #{@account.acct} could not be made due to HTTP or SSL error"
+  end
+
+  private
+
+  def build_request
+    Request.new(:post, @account.hub_url, form: subscription_params)
+  end
+
+  def subscription_params
+    {
+      'hub.topic': @account.remote_url,
+      'hub.mode': 'unsubscribe',
+      'hub.callback': api_subscription_url(@account.id),
+      'hub.verify': 'async',
+    }
   end
 end
diff --git a/app/workers/pubsubhubbub/confirmation_worker.rb b/app/workers/pubsubhubbub/confirmation_worker.rb
index 9186c5d7d..e1ccfb99c 100644
--- a/app/workers/pubsubhubbub/confirmation_worker.rb
+++ b/app/workers/pubsubhubbub/confirmation_worker.rb
@@ -60,9 +60,7 @@ class Pubsubhubbub::ConfirmationWorker
   end
 
   def callback_get_with_params
-    HTTP.headers(user_agent: 'Mastodon/PubSubHubbub')
-        .timeout(:per_operation, write: 20, connect: 20, read: 50)
-        .get(subscription.callback_url, params: callback_params)
+    Request.new(:get, subscription.callback_url, params: callback_params).perform
   end
 
   def callback_response_body
@@ -71,10 +69,10 @@ class Pubsubhubbub::ConfirmationWorker
 
   def callback_params
     {
-      'hub.topic' => account_url(subscription.account, format: :atom),
-      'hub.mode' => mode,
-      'hub.challenge' => challenge,
-      'hub.lease_seconds' => subscription.lease_seconds,
+      'hub.topic': account_url(subscription.account, format: :atom),
+      'hub.mode': mode,
+      'hub.challenge': challenge,
+      'hub.lease_seconds': subscription.lease_seconds,
     }
   end
 
diff --git a/app/workers/pubsubhubbub/delivery_worker.rb b/app/workers/pubsubhubbub/delivery_worker.rb
index 981838f33..05d160cf7 100644
--- a/app/workers/pubsubhubbub/delivery_worker.rb
+++ b/app/workers/pubsubhubbub/delivery_worker.rb
@@ -33,9 +33,9 @@ class Pubsubhubbub::DeliveryWorker
   end
 
   def callback_post_payload
-    HTTP.timeout(:per_operation, write: 50, connect: 20, read: 50)
-        .headers(headers)
-        .post(subscription.callback_url, body: payload)
+    request = Request.new(:post, subscription.callback_url, body: payload)
+    request.add_headers(headers)
+    request.perform
   end
 
   def blocked_domain?
@@ -48,13 +48,12 @@ class Pubsubhubbub::DeliveryWorker
 
   def headers
     {
-      'User-Agent' => 'Mastodon/PubSubHubbub',
       'Content-Type' => 'application/atom+xml',
-      'Link' => link_headers,
+      'Link' => link_header,
     }.merge(signature_headers.to_h)
   end
 
-  def link_headers
+  def link_header
     LinkHeader.new([hub_link_header, self_link_header]).to_s
   end