An update to @peplin's work on https://gist.github.com/peplin/470321 that makes this gist compatible with the more modern AWS-SDK gem and new APIs, and updates for Chef 11.x (still works with 10.x too).

s3-file.rb

#
# Author:: Christopher Peplin (<[email protected]>)
# Copyright:: Copyright (c) 2010 Bueda, Inc.
# License:: Apache License, Version 2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

class Chef
  class Provider
    class S3File < Chef::Provider::RemoteFile
      def action_create
        sources = @new_resource.source
        source = sources
        # Handle the Chef 10.x use case along with 11.x
        if sources.respond_to?(:shift)
          source = sources.shift
        end
        Chef::Log.debug("Checking #{@new_resource} for changes")

        if current_resource_matches_target_checksum?
          Chef::Log.debug("File #{@new_resource} checksum matches target checksum (#{@new_resource.checksum}), not updating")
        else
          Chef::Log.debug("File #{@current_resource} checksum didn't match target checksum (#{@new_resource.checksum}), updating")
          fetch_from_s3(source) do |raw_file|
            if matches_current_checksum?(raw_file)
              Chef::Log.debug "#{@new_resource}: Target and Source checksums are the same, taking no action"
            else
              backup_new_resource
              Chef::Log.debug "copying remote file from origin #{raw_file.path} to destination #{@new_resource.path}"
              FileUtils.cp raw_file.path, @new_resource.path
              @new_resource.updated_by_last_action(true)
            end
          end
        end
        enforce_ownership_and_permissions

        @new_resource.updated_by_last_action?
      end

      def fetch_from_s3(source)
        begin
          require  'aws-sdk'
          protocol, bucket, name = URI.split(source).compact
          name = name[1..-1]
          obj = AWS::S3.new(
              :access_key_id     => @new_resource.access_key_id,
              :secret_access_key => @new_resource.secret_access_key
          ).buckets[bucket].objects[name]
          Chef::Log.debug("Downloading #{name} from S3 bucket #{bucket}")
          file = Tempfile.new("chef-s3-file")
          file.write obj.read
          Chef::Log.debug("File #{name} is #{file.size} bytes on disk")
          begin
            yield file
          ensure
            file.close
          end
        rescue URI::InvalidURIError
          Chef::Log.warn("Expected an S3 URL but found #{source}")
          nil
        end
      end
    end
  end
end

class Chef
  class Resource
    class S3File < Chef::Resource::RemoteFile
      def initialize(name, run_context=nil)
        super
        @resource_name = :s3_file
      end

      def provider
        Chef::Provider::S3File
      end

      def access_key_id(args=nil)
        set_or_return(
          :access_key_id,
          args,
          :kind_of => String
        )
      end

      def secret_access_key(args=nil)
        set_or_return(
          :secret_access_key,
          args,
          :kind_of => String
        )
      end
    end
  end
end

Excellent work! This worked like a charm for me in linux but i ran into some issues on my windows boxes. It appears to download the files, but they come out corrupt. Any ideas why that may be happening?

Got it to work on Windows. Ruby 1.9 requires you to specify when writing binary. So I just needed to add file.binmode

Just put under libraries and is working fine, it looks like i had a problem with chef 11.4.4, thanks for the good work

I suggest adding the sample-usage as a comment into the library for future reference.

This does look very promising but it is NOT idempotent - basically, this will always be downloading the file from S3 regardless of whether it's already been downloaded. Quick look into list of updated resources after each run uncovers this very easily.

@milosgajdos83 It should work with Chef's not_if which you can use with ::File.exists? to have the stanza not run if a file exists already.