From ec1bb5db87a40d74203a09ca401d0f70d0ad962d Mon Sep 17 00:00:00 2001
From: Samantaz Fox <coding@samantaz.fr>
Date: Thu, 1 Aug 2024 23:28:30 +0200
Subject: [PATCH] SigHelper: Add support for PLAYER_UPDATE_TIMESTAMP opcode

---
 config/config.example.yml           | 15 ++++++++++++++-
 src/invidious/helpers/sig_helper.cr |  9 +++++++++
 src/invidious/helpers/signatures.cr | 17 +++++++++++++----
 3 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/config/config.example.yml b/config/config.example.yml
index 142fdfb7..2f5228a6 100644
--- a/config/config.example.yml
+++ b/config/config.example.yml
@@ -1,6 +1,6 @@
 #########################################
 #
-#  Database configuration
+#  Database and other external servers
 #
 #########################################
 
@@ -41,6 +41,19 @@ db:
 #check_tables: false
 
 
+##
+## Path to an external signature resolver, used to emulate
+## the Youtube client's Javascript. If no such server is
+## available, some videos will not be playable.
+##
+## When this setting is commented out, no external
+## resolver will be used.
+##
+## Accepted values: a path to a UNIX socket or "<IP>:<Port>"
+## Default: <none>
+##
+#signature_server:
+
 
 #########################################
 #
diff --git a/src/invidious/helpers/sig_helper.cr b/src/invidious/helpers/sig_helper.cr
index 108587ce..2239858b 100644
--- a/src/invidious/helpers/sig_helper.cr
+++ b/src/invidious/helpers/sig_helper.cr
@@ -61,6 +61,7 @@ module Invidious::SigHelper
     DECRYPT_SIGNATURE       = 2
     GET_SIGNATURE_TIMESTAMP = 3
     GET_PLAYER_STATUS       = 4
+    PLAYER_UPDATE_TIMESTAMP = 5
   end
 
   private record Request,
@@ -135,7 +136,15 @@ module Invidious::SigHelper
         player_version = IO::ByteFormat::NetworkEndian.decode(UInt32, bytes[1..4])
         has_player ? player_version : nil
       end
+    end
 
+    # Return when the player was last updated
+    def get_player_timestamp : UInt64?
+      request = Request.new(Opcode::GET_SIGNATURE_TIMESTAMP, nil)
+
+      return self.send_request(request) do |bytes|
+        IO::ByteFormat::NetworkEndian.decode(UInt64, bytes)
+      end
     end
 
     private def send_request(request : Request, &)
diff --git a/src/invidious/helpers/signatures.cr b/src/invidious/helpers/signatures.cr
index 8fbfaac0..cf170668 100644
--- a/src/invidious/helpers/signatures.cr
+++ b/src/invidious/helpers/signatures.cr
@@ -2,18 +2,27 @@ require "http/params"
 require "./sig_helper"
 
 struct Invidious::DecryptFunction
-  @last_update = Time.monotonic - 42.days
+  @last_update : Time = Time.utc - 42.days
 
   def initialize
     self.check_update
   end
 
   def check_update
-    now = Time.monotonic
-    if (now - @last_update) > 60.seconds
+    now = Time.utc
+
+    # If we have updated in the last 5 minutes, do nothing
+    return if (now - @last_update) > 5.minutes
+
+    # Get the time when the player was updated, in the event where
+    # multiple invidious processes are run in parallel.
+    player_ts = Invidious::SigHelper::Client.get_player_timestamp
+    player_time = Time.unix(player_ts || 0)
+
+    if (now - player_time) > 5.minutes
       LOGGER.debug("Signature: Player might be outdated, updating")
       Invidious::SigHelper::Client.force_update
-      @last_update = Time.monotonic
+      @last_update = Time.utc
     end
   end