Preserving case in HTTP headers with Ruby's Net:HTTP

Question

Although the HTTP spec says that headers are case insensitive; Paypal, with their new adaptive payments API require their headers to be case-sensitive.

Using the paypal adaptive payments extension for ActiveMerchant (http://github.com/lamp/paypal_adaptive_gateway) it seems that although the headers are set in all caps, they are sent in mixed case.

Here is the code that sends the HTTP request:

headers = {
  "X-PAYPAL-REQUEST-DATA-FORMAT" => "XML",
  "X-PAYPAL-RESPONSE-DATA-FORMAT" => "JSON",
  "X-PAYPAL-SECURITY-USERID" => @config[:login],
  "X-PAYPAL-SECURITY-PASSWORD" => @config[:password],
  "X-PAYPAL-SECURITY-SIGNATURE" => @config[:signature],
  "X-PAYPAL-APPLICATION-ID" => @config[:appid]
}
build_url action

request = Net::HTTP::Post.new(@url.path)

request.body = @xml
headers.each_pair { |k,v| request[k] = v }
request.content_type = 'text/xml'

proxy = Net::HTTP::Proxy("127.0.0.1", "60723")

server = proxy.new(@url.host, 443)
server.use_ssl = true

server.start { |http| http.request(request) }.body

(i added the proxy line so i could see what was going on with Charles - http://www.charlesproxy.com/)

When I look at the request headers in charles, this is what i see:

X-Paypal-Application-Id ...
X-Paypal-Security-Password...
X-Paypal-Security-Signature ...
X-Paypal-Security-Userid ...
X-Paypal-Request-Data-Format XML
X-Paypal-Response-Data-Format JSON
Accept */*
Content-Type text/xml
Content-Length 522
Host svcs.sandbox.paypal.com

I verified that it is not Charles doing the case conversion by running a similar request using curl. In that test the case was preserved.

Answer 1

The RFC does specify that header keys are case-insensitive, so unfortunately you seem to have hit an annoying requirement with the PayPal API.

Net::HTTP is what is changing the case, although I'm surprised they're not all getting downcased:

# File net/http.rb, line 1160
    def []=(key, val)
      unless val
        @header.delete key.downcase
        return val
      end
      @header[key.downcase] = [val]
    end

"Sets the header field corresponding to the case-insensitive key."

As the above is a simple class it could be monkey-patched. I will think further for a nicer solution.