Rails 5.2 credentials:edit doesn't like secret_key_base - ruby-on-rails

Question

I've been trying to debug my credentials file in my staging server. Whenever I try to edit the credentials on my staging server, I get the following error:
/var/www/bundle/ruby/2.5.0/gems/railties-5.2.0/lib/rails/application.rb:583:in `validate_secret_key_base': `secret_key_base` for staging environment must be a type of String`
My database.yml file looks like the following:
---
default: &default
adapter: postgresql
development:
<<: *default
database: dev_db
host: <%= Rails.application.credentials.database.fetch(:development).fetch(:host) %>
username: <%= Rails.application.credentials.database.fetch(:development).fetch(:username) %>
password: <%= Rails.application.credentials.database.fetch(:development).fetch(:password) %>
secret_key_base: <%= Rails.application.credentials.secret_key_base.fetch(:development) %>
test:
<<: *default
database: test_db
host: <%= Rails.application.credentials.database.fetch(:development).fetch(:host) %>
username: <%= Rails.application.credentials.database.fetch(:development).fetch(:username) %>
password: <%= Rails.application.credentials.database.fetch(:development).fetch(:password) %>
secret_key_base: <%= Rails.application.credentials.secret_key_base.fetch(:development) %>
staging:
<<: *default
database: <%= Rails.application.credentials.database.fetch(:staging).fetch(:name) %>
host: <%= Rails.application.credentials.database.fetch(:staging).fetch(:host) %>
username: <%= Rails.application.credentials.database.fetch(:staging).fetch(:username) %>
password: <%= Rails.application.credentials.database.fetch(:staging).fetch(:password) %>
secret_key_base: <%= Rails.application.credentials.secret_key_base.fetch(:staging) %>
production:
<<: *default
database: <%= Rails.application.credentials.database.fetch(:production).fetch(:name) %>
host: <%= Rails.application.credentials.database.fetch(:production).fetch(:host) %>
username: <%= Rails.application.credentials.database.fetch(:production).fetch(:username) %>
password: <%= Rails.application.credentials.database.fetch(:production).fetch(:password) %>
secret_key_base: <%= Rails.application.credentials.secret_key_base.fetch(:production) %>
I think my staging's secret_key_base is of type String. I generated my secret_key_base using rails secret. Locally, when I bring up the rails console, I can view the secret_key_bases for my staging environment:
[1] pry(main)> Rails.application.credentials.secret_key_base.fetch(:staging)
\=> "generated_using_rails_secret"
It returns a string but I still get the error message above whenever I try to access credentials in my staging environment.

Answer 1

I ended up looking at the stack trace and digging into the railties-5.2.0 gem.
Abbreviated stack trace:
ArgumentError: `secret_key_base` for staging environment must be a type of String`
/var/www/bundle/ruby/2.5.0/gems/railties-5.2.0/lib/rails/application.rb:583:in `validate_secret_key_base'
/var/www/bundle/ruby/2.5.0/gems/railties-5.2.0/lib/rails/application.rb:432:in `secret_key_base'
/var/www/bundle/ruby/2.5.0/gems/railties-5.2.0/lib/rails/application.rb:176:in `key_generator'
/var/www/bundle/ruby/2.5.0/gems/railties-5.2.0/lib/rails/application.rb:205:in `message_verifier'
I ended up looking in railties-5.2.0/lib/rails/application.rb:432: and seeing the following bit of code:
# The secret_key_base is used as the input secret to the application's key generator, which in turn
# is used to create all MessageVerifiers/MessageEncryptors, including the ones that sign and encrypt cookies.
#
# In test and development, this is simply derived as a MD5 hash of the application's name.
#
# In all other environments, we look for it first in ENV["SECRET_KEY_BASE"],
# then credentials.secret_key_base, and finally secrets.secret_key_base. For most applications,
# the correct place to store it is in the encrypted credentials file.
def secret_key_base
if Rails.env.test? || Rails.env.development?
Digest::MD5.hexdigest self.class.name
else
validate_secret_key_base(
ENV["SECRET_KEY_BASE"] || credentials.secret_key_base || secrets.secret_key_base
)
end
end
I had mistakenly thought I could specify a SECRET_KEY_BASE for an individual environment. Instead, I could only specify one secret key base. The secret key base apparently has nothing to do with database.yml. I need to read up on it and what it actually does.

Answer 2

If you run rails credentials:edit from the command line it will decrypt the config/credentials.yml.enc file.
You can then edit this file to add environment based secret keys like you would have previously added to config/secrets.yml.
When you save this file it will be encrypted again with the new information included.
There is no reason to have the "secret_key_base" in your database.yml file as this will not have any impact.
Nice Article on the new Rails credentials
Additionally just because rails now longer generates a config/secrets.yml file for you, as of rails 5.2, adding one will still work appropriately as it has in previous releases.