ruby-on-rails - 如何使用云端的 s3 对象 URL？

Question

我目前正在 S3 上私下存储文件。在我的 Rails 应用程序中，在 attachment.rb 模型中，我可以获得私有(private)文件的公共(public) URL，如下所示:

def cdn_url ( style='original' )
  attachment.s3_object(style).url_for( :read, secure: true, response_content_type: self.meta['file_content_type'], expires: 1.hour ).to_s
end

问题是这是向 S3 提供 URL 并重写 URL 以使用我的 Cloudfront 原始 url 错误:

The request signature we calculated does not match the signature you provided. Check your key and signing method.

如何获取如下所示的公共(public) URL Assets ，但通过 Cloudfront 提供该 Assets ？

Answer 1

第一种方法(简单)

只需使用 aws_cf_signer gem 。把它放在你的 bundler 中。

有了这个你可以做类似的事情

def cdn_url (options = {})
  style = options[:style] || 'original'
  cloudfront_domain =  options[:cloudfront_domain] || 'example.cloudfront.net'
  cloudfront_pem_key_path = options[:cloudfront_pem_key_path]
  cloudfront_key_paid_id = options[:cloundfrount_key_paid_id] 
  path = attachment.path(style)  #path of the file
  # you can get this values from your aws a/c , most probably by going int 
  # https://console.aws.amazon.com/iam/home?#security_credential      
  signer = AwsCfSigner.new(cloudfront_pem_key_path, cloudfront_key_paid_id)
  # this configuration may vary. 
  # visit https://github.com/dylanvaughn/aws_cf_signer 
  # and check all available settings/options   
  url = signer.sign(path, :ending => Time.now + 3600)
  cloudfront_domain + url
end 

有了这个，你可以像这样访问 url

  cdn_url(cloudfront_pem_key_path: '/users/downloads/pri.pem' , cloudfront_key_paid_id: '33243424XXX')

第二种方式

# A simple function to return a signed, expiring url for Amazon Cloudfront. 
# This will require openssl, digest/sha1, base64 and maybe other libraries. 
 
module CloudFront
  def get_signed_expiring_url(domain,path, expires_in, private_key_filename, key_pair_id)
 
    # AWS works on UTC, so make sure you are not using local time
    expires = (Time.now.getutc + expires_in).to_i.to_s
 
    private_key = OpenSSL::PKey::RSA.new(File.read(private_key_filename))
 
    # path should be your S3 path without a leading slash and without a file extension.
    # e.g. files/private/52
    policy = %Q[{"Statement":[{"Resource":"#{path}","Condition":{"DateLessThan":{"AWS:EpochTime":#{expires}}}}]}]
    signature = Base64.strict_encode64(private_key.sign(OpenSSL::Digest::SHA1.new, policy))
 
    # I'm not sure exactly why this is required, but it's in Amazon's perl script and seems necessary
    # Different base64 implementations maybe? 
    signature.tr!("+=/", "-_~")
    
    "#{domain}#{path}?Expires=#{expires}&Signature=#{signature}&Key-Pair-Id=#{key_pair_id}"
  end
end
 

有了这个你可以做类似的事情

def cdn_url ( style='original',cloudfront_pem_key_path,key_pair_id)
  path = attachment.path(style)  #path of the file
  # you can get this values from your aws a/c , most probably by going int 
  CloudFront.get_signed_expiring_url 'example.cloudfront.net', path, 45.seconds ,'/users/downloads/pri.pem', 'as12XXXXX')
end
 

试一试，也许它会奏效。请务必正确设置存储桶访问策略。如果您看到 accessDenied 错误，请检查一下 http://www.jppinto.com/2011/12/access-denied-to-file-amazon-s3-bucket/