Add CLI task for rotating keys (#8466)

* If an Update is signed with known key, skip re-following procedure

Because it means the remote actor did *not* lose their database

* Add CLI method for rotating keys

    bin/tootctl accounts rotate [USERNAME]

Generates a new RSA key per account and sends out an Update activity
signed with the old key.

* Key rotation: Space out Update fan-outs every 5 minutes per 1000 accounts

* Skip suspended accounts in key rotation

3 files changed, 7 insertions, 5 deletions

diff --git a/app/lib/activitypub/activity/update.rb b/app/lib/activitypub/activity/update.rb
index aa5907f03..6eebc3b5c 100644
--- a/app/lib/activitypub/activity/update.rb
+++ b/app/lib/activitypub/activity/update.rb
@@ -11,6 +11,6 @@ class ActivityPub::Activity::Update < ActivityPub::Activity
 
   def update_account
     return if @account.uri != object_uri
-    ActivityPub::ProcessAccountService.new.call(@account.username, @account.domain, @object)
+    ActivityPub::ProcessAccountService.new.call(@account.username, @account.domain, @object, signed_with_known_key: true)
   end
 end
diff --git a/app/lib/activitypub/linked_data_signature.rb b/app/lib/activitypub/linked_data_signature.rb
index 16142a6ff..f52a8f406 100644
--- a/app/lib/activitypub/linked_data_signature.rb
+++ b/app/lib/activitypub/linked_data_signature.rb
@@ -32,7 +32,7 @@ class ActivityPub::LinkedDataSignature
     end
   end
 
-  def sign!(creator)
+  def sign!(creator, sign_with: nil)
     options = {
       'type'    => 'RsaSignature2017',
       'creator' => [ActivityPub::TagManager.instance.uri_for(creator), '#main-key'].join,
@@ -42,8 +42,9 @@ class ActivityPub::LinkedDataSignature
     options_hash  = hash(options.without('type', 'id', 'signatureValue').merge('@context' => CONTEXT))
     document_hash = hash(@json.without('signature'))
     to_be_signed  = options_hash + document_hash
+    keypair       = sign_with.present? ? OpenSSL::PKey::RSA.new(sign_with) : creator.keypair
 
-    signature = Base64.strict_encode64(creator.keypair.sign(OpenSSL::Digest::SHA256.new, to_be_signed))
+    signature = Base64.strict_encode64(keypair.sign(OpenSSL::Digest::SHA256.new, to_be_signed))
 
     @json.merge('signature' => options.merge('signatureValue' => signature))
   end
diff --git a/app/lib/request.rb b/app/lib/request.rb
index 576ed23ca..21bdaa700 100644
--- a/app/lib/request.rb
+++ b/app/lib/request.rb
@@ -22,10 +22,11 @@ class Request
     set_digest! if options.key?(:body)
   end
 
-  def on_behalf_of(account, key_id_format = :acct)
+  def on_behalf_of(account, key_id_format = :acct, sign_with: nil)
     raise ArgumentError unless account.local?
 
     @account       = account
+    @keypair       = sign_with.present? ? OpenSSL::PKey::RSA.new(sign_with) : @account.keypair
     @key_id_format = key_id_format
 
     self
@@ -70,7 +71,7 @@ class Request
 
   def signature
     algorithm = 'rsa-sha256'
-    signature = Base64.strict_encode64(@account.keypair.sign(OpenSSL::Digest::SHA256.new, signed_string))
+    signature = Base64.strict_encode64(@keypair.sign(OpenSSL::Digest::SHA256.new, signed_string))
 
     "keyId=\"#{key_id}\",algorithm=\"#{algorithm}\",headers=\"#{signed_headers}\",signature=\"#{signature}\""
   end