Beefy Boxes and Bandwidth Generously Provided by pair Networks
Come for the quick hacks, stay for the epiphanies.
 
PerlMonks  

Re: CGI: newlines, write exactly "\r\n" to end the headers, then turn off binmode

by ikegami (Patriarch)
on Mar 09, 2018 at 17:39 UTC ( [id://1210583]=note: print w/replies, xml ) Need Help??


in reply to CGI: newlines, write exactly "\r\n" to end the headers, then turn off binmode

You're not sending an HTTP response, though. You're sending a CGI response. What server are you using? Apache accepts LF. (I think it also accepts CRLF.)

  • Comment on Re: CGI: newlines, write exactly "\r\n" to end the headers, then turn off binmode

Replies are listed 'Best First'.
Re: CGI: newlines, write exactly "\r\n" to end the headers, then turn off binmode
by 7stud (Deacon) on Mar 09, 2018 at 19:35 UTC

    You're not sending an HTTP response, though. You're sending a CGI response. What server are you using? Apache accepts LF.

    Interesting. I sent a curl request to my Apache server, and I sniffed the response using Wireshark, and Apache performs conversions on the characters that a cgi script uses to terminate the headers. Here are the conversions that I observed:

    1. "\n\n" => "\r\n\r\n"
    2. "\r\n\r\n" => "\r\n\r\n"
    3. "\r\r" => Internal sever error
    4. "\n\r\n\r" => "\r\n\r\n" plus a \r to start the body of the request

    I think Apache is following the dictum: "Be permissive in what you allow, but be strict in what you do." Likewise, I am going to be strict in what I do, and I'm not going to rely on a server to convert newlines to the HTTP 1.1 spec.

    (I think it also accepts CRLF.)

    It seems obvious to me that any http server would accept the header termination characters in the HTTP 1.1 spec? Why the hesitation? Were you speculating that "\r\n\r\n" might get converted to "\r\r\n\r\r\n"?

      Likewise, I am going to be strict in what I do, and I'm not going to rely on a server to convert newlines to the HTTP 1.1 spec.
      Why do you feel the need to output a response compliant to the HTTP spec when you are not returning an HTTP response? You're returning a CGI response, thus you should be concerned with following the CGI spec, not the HTTP spec. So what does the CGI spec say?
      6.2.  Response Types
      
         The response comprises a message-header and a message-body, separated
         by a blank line.  The message-header contains one or more header
         fields.  The body may be NULL.
      
            generic-response = 1*header-field NL [ response-body ]
      
      It says headers are ended by a blank line, as delimited with "NL". Hmm, NL. Obviously means "new line", but what ASCII character sequence might that be?
      6.3.4.  Protocol-Specific Header Fields
      
         The script MAY return any other header fields that relate to the
         response message defined by the specification for the SERVER_PROTOCOL
         (HTTP/1.0 [1] or HTTP/1.1 [4]).  The server MUST translate the header
         data from the CGI header syntax to the HTTP header syntax if these
         differ.  For example, the character sequence for newline (such as
         UNIX's US-ASCII LF) used by CGI scripts may not be the same as that
         used by HTTP (US-ASCII CR followed by LF).
      
      Apache isn't capriciously translating \n to \r\n just for the sake of being permissive, the CGI spec says that CGI-supporting web servers "MUST" do this and explicitly allows CGI scripts to use different line endings than those prescribed by the HTTP spec, even giving unix-style \n-only line ends as an example of a possible alternative.

      You can rely on servers to do this conversion because any server which doesn't is not compliant with the CGI spec.

        So awesome! And hence why I see all those cgi scripts just doing print "\n\n";. Thanks for the enlightenment!

      Please use the [reply] link to the right of the post you are replying to.

      I'm not going to rely on a server to convert newlines to the HTTP 1.1 spec.

      wut. Why would not rely on Apache sending a valid reponse?

      t seems obvious to me that any http server would accept the header termination characters in the HTTP 1.1 spec?

      Again, we're talking about a CGI response, not an HTTP response.

Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Node Status?
node history
Node Type: note [id://1210583]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this?Last hourOther CB clients
Other Users?
Others making s'mores by the fire in the courtyard of the Monastery: (4)
As of 2024-06-16 20:48 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found

    Notices?
    erzuuli‥ 🛈The London Perl and Raku Workshop takes place on 26th Oct 2024. If your company depends on Perl, please consider sponsoring and/or attending.