Ruby script to use as a hook for the letsencrypt.sh client

lets-encrypt-route53.rb

#!/usr/bin/env ruby

require 'aws-sdk'

#
# This script requires you to have the following environment variables set:
#   AWS_REGION="us-west-2"
#   AWS_ACCESS_KEY_ID="<YOUR_KEY>"
#   AWS_SECRET_ACCESS_KEY="<YOUR_SECRET_KEY>"
#
# Based on https://gist.github.com/asimihsan/d8d8f0f10bdc85fc6f8a
#

def find_hosted_zone(route53, domain)
  route53 = Aws::Route53::Client.new
  hosted_zones = route53.list_hosted_zones_by_name.hosted_zones

  index = hosted_zones.index { |zone| domain.end_with?(zone.name.chop) }
  if index.nil?
    puts 'Unable to find matching zone.'
    exit 1
  end

  hosted_zones[index]
end

def wait_for_change(route53, change_id)
  status = ''
  until status == 'INSYNC'
    resp = route53.get_change(id: change_id)
    status = resp.change_info.status
    if status != 'INSYNC'
      puts 'Waiting for dns change to complete'
      sleep 5
    end
  end
end

def setup_dns(domain, txt_challenge)
  route53 = Aws::Route53::Client.new
  hosted_zone = find_hosted_zone(route53, domain)

  changes = []
  changes << {
    action: 'UPSERT',
    resource_record_set: {
      name: "_acme-challenge.#{domain}.",
      type: 'TXT',
      ttl: 60,
      resource_records: [
        value: "\"#{txt_challenge}\""
      ]
    }
  }
  resp = route53.change_resource_record_sets(
    hosted_zone_id: hosted_zone.id,
    change_batch: {
      changes: changes
    }
  )
  wait_for_change(route53, resp.change_info.id)
end

def delete_dns(domain, txt_challenge)
  route53 = Aws::Route53::Client.new
  hosted_zone = find_hosted_zone(route53, domain)
  changes = []
  changes << {
    action: 'DELETE',
    resource_record_set: {
      name: "_acme-challenge.#{domain}.",
      type: 'TXT',
      ttl: 60,
      resource_records: [
        value: "\"#{txt_challenge}\""
      ]
    }
  }
  resp = route53.change_resource_record_sets(
    hosted_zone_id: hosted_zone.id,
    change_batch: {
      changes: changes
    }
  )
  wait_for_change(route53, resp.change_info.id)
end

if __FILE__ == $PROGRAM_NAME
  hook_stage = ARGV[0]
  domain = ARGV[1]
  txt_challenge = ARGV[3]

  puts "stage: #{hook_stage} domain: #{domain} txt_challenge: #{txt_challenge}"

  if hook_stage == 'deploy_challenge'
    setup_dns(domain, txt_challenge)
  elsif hook_stage == 'clean_challenge'
    delete_dns(domain, txt_challenge)
  end
end

AWS::Route53 methods list_hosted_zones and list_hosted_zones_by_name paginate zone results with a max of 100.

AWS::Route53 list_hosted_zones* method documentation

So the find_hosted_zone function can fail if you have 100+ zones and the one you're looking for is not in the first page of results. I added another function to recursively build a list of all zones, and use that as the hosted_zones list within the find_hosted_zone function.

Here is an example of the function I'm using:

def get_hosted_zones(options={})
  route53 = Aws::Route53::Client.new

  response = route53.list_hosted_zones(options)

  result = response.hosted_zones

  if response.is_truncated
    result.concat(get_hosted_zones({ marker: response.next_marker }))
  end

  return result
end

def find_hosted_zone(route53, domain)
  hosted_zones = get_hosted_zones
  
  # . . .

end

Disclaimer: I'm still new to Ruby so there might be a better way to achieve this, but it works :)

How I fixed it for me:
index = hosted_zones.rindex { |zone| domain.end_with?(zone.name.chop) }
This works because list_hosted_zones_by_name result is ordered like this:
com.example.
com.example.test.
com.example.testing.
so hosted_zones.index will give you example.com and hosted_zones.rindex will give test.example.com for name "cert.test.example.com"
(edit: not sure if this will work with > 100 zones though)

it seems that this does not work with wildcard certificates I tried to create a cert containing 'test.example.com' and '.test.example.com'. That does not work. If I use 'test2.example.com' and '.test.example.com' it works. The ACMEv2 Documentation states that there should be two TXT secrets in test.example.com when validating. One for the wildcard and one for the normal validation. I suspect that the script overrides the first with the second and then fails to validate.
Could that be?

@cbergmann have a look at my fork: https://gist.github.com/oveaurs/68c32500c0f5a2a4507f051adf439673

I found that this script has problems when you have sub domain zones in AWS. Eg.

• example.com
• sub.example.com

index = hosted_zones.index { |zone| domain.end_with?(zone.name.chop) }

This will cause the script to create the challenge TXT record in the example.com zone but a DNS query will try to find it in the subdomain zone. To work around this I changed the comparison to the other way around. Instead of checking if the domain ends with the zone name I check if the zone name ends with the domain latter part:

index = hosted_zones.index { |zone| zone.name.chop.end_with?(domain.split(".",2)[1]) }

Something to consider!

@reinhard-brandstaedter what I did to fix the same issue:
index = hosted_zones.rindex { |zone| domain.end_with?(zone.name.chop) }
It will then use the "earliest match"