How to enable TLS for Redis 6 on Sidekiq?

Problem

On my Ruby on Rails app, I keep getting the error below for the Heroku Redis Premium 0 add-on:

OpenSSL::SSL::SSLError: SSL_connect returned=1 errno=0 state=error: certificate verify failed (self signed certificate in certificate chain)

Heroku Redis documentation mentions that I need to enable TLS in my Redis client's configuration in order to connect to a Redis 6 database. To achive this, I have read SSL/TLS Support documentation on redis-rb. My understanding from it is; I need to assign ca_file, cert and key for Redis.new#ssl_params. The question is how to set these for Redis or through Sidekiq on Heroku?

Updates

Update 3: Heroku support provided an answer which solved the problem.

Update 2: Created Heroku support ticket and waiting response.

Update 1: Asked on Sidekiq's Github issues and was adviced go write Heroku support. Will update this question, when I do get an answer.

Related Info

I have verified the app does work when the add-on is either one of the below:

hobby-dev for Redis 6
premium 0 for Redis 5

Versions:

Ruby – 3.0.0p0
Ruby on Rails – 6.1.1
Redis – 6.0
redis-rb – 4.2.5
Sidekiq – 6.2.1
Heroku Stack – 20

Some links that helped me to narrow down the issue:

Solution

Use OpenSSL::SSL::VERIFY_NONE for your Redis client.

Sidekiq

# config/initializers/sidekiq.rb
Sidekiq.configure_server do |config|
  config.redis = { ssl_params: { verify_mode: OpenSSL::SSL::VERIFY_NONE } }
end

Sidekiq.configure_client do |config|
  config.redis = { ssl_params: { verify_mode: OpenSSL::SSL::VERIFY_NONE } }
end

Redis

Redis.new(url: 'url', driver: :ruby, ssl_params: { verify_mode: OpenSSL::SSL::VERIFY_NONE })

Reason

Redis 6 requires TLS to connect. However, Heroku support explained that they manage requests from the router level to the application level involving Self Signed Certs. Turns out, Heroku terminates SSL at the router level and requests are forwarded from there to the application via HTTP while everything is behind Heroku's Firewall and security measures.

Sources