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> Use this file to discover all available pages before exploring further.
# Auth0 Ruby On Rails SDK Quickstarts: Troubleshooting
##### By David Patrick
Troubleshooting tips for using Rails with Auth0.We recommend that you log in to follow this quickstart with examples configured for your account.
# Troubleshooting
The following are troubleshooting topics that you might run into when using the Rails quickstart.
## Using a reverse proxy
The `redirect_uri` parameter that OmniAuth generates when redirecting to login is based on the `Host` header that is passed to Rails. This can cause incorrect callback URLs to be passed when using this strategy (and OmniAuth in general) with a reverse proxy. You can adjust the host used by OmniAuth with the following snippet:
```
OmniAuth.config.full_host = lambda do |env|
scheme = env['rack.url_scheme']
local_host = env['HTTP_HOST']
forwarded_host = env['HTTP_X_FORWARDED_HOST']
forwarded_host.blank? ? "#{scheme}://#{local_host}" : "#{scheme}://#{forwarded_host}"
end
```
[See this StackOverflow thread for more information](https://stackoverflow.com/a/7135029/728480).
## ActionController::InvalidAuthenticityToken
This is likely caused by a missing CSRF token needed to POST the login request. If you inspect the login button in your browser, you should see something like this:
```erb lines theme={null}
Login
```
... and in the `` element for the page, you should have CSRF meta tags like these:
```erb lines theme={null}
```
With those elements in place, Rails will convert the login link to POST the CSRF token to the backend to verify it before redirecting to login.
## ActionDispatch::Cookies::CookieOverflow
This error means that a cookie session is being used and because the whole profile is being stored, it overflows the max-size of 4 kb. If you are unable to access the user profile, or you get an error similar to `NoMethodError`, `undefined method '[]' for nil:NilClass`, try using In-Memory store for development.
Go to `/config/initializers/session_store.rb` (or create it if it does not exist) and add the following:
```
Rails.application.config.session_store :cache_store
```
Go to `/config/environments/development.rb` and add the following:
```
config.cache_store = :memory_store
```
Restart your Rails server for these changes to take effect.
It is recommended that a memory store, such as MemCached, is being used for production applications.
## SSL Issues
Under some configurations, Ruby may not be able to find certification authority certificates (CA certs).
Download the CA certs bundle to the project directory:
```bash lines theme={null}
curl -L -o lib/ca-bundle.crt http://curl.haxx.se/ca/ca-bundle.crt
```
Add this initializer to `config/initializers/fix_ssl.rb`:
```rb lines theme={null}
# config/initializers/fix_ssl.rb
require 'open-uri'
require 'net/https'
module Net
class HTTP
alias_method :original_use_ssl=, :use_ssl=
def use_ssl=(flag)
path = ( Rails.env == "development") ? "lib/ca-bundle.crt" : "/usr/lib/ssl/certs/ca-certificates.crt"
self.ca_file = Rails.root.join(path).to_s
self.verify_mode = OpenSSL::SSL::VERIFY_PEER
self.original_use_ssl = flag
end
end
end
```
## "failure message=invalid\_credentials"
This issue doesn't occur when working locally but may happen in a staging or production environment. The error message may be displayed as:
```
omniauth: (auth0) Authentication failure! invalid_credentials: OAuth2::Error, server_error: The redirect URI is wrong. You send [wrong url], and we expected [callback url set in your app settings]
```
To solve this, add the following to `config/environments/staging.rb` or `production.rb`:
```
OmniAuth.config.full_host = "http://www.example.com"
```
Substitute `http://www.example.com` with the actual URL you'll be using in your application.
[Edit on GitHub](https://github.com/auth0/docs/edit/master/articles/quickstart/webapp/rails/02-troubleshooting.md)