From 09cca9813d14b15f13722fe2b02dab08bd910e44 Mon Sep 17 00:00:00 2001 From: Daniel Stenberg Date: Tue, 29 Mar 2016 08:53:40 +0200 Subject: docs/HTTP-COOKIES: converted to markdown --- docs/HTTP-COOKIES.md | 104 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 104 insertions(+) create mode 100644 docs/HTTP-COOKIES.md (limited to 'docs/HTTP-COOKIES.md') diff --git a/docs/HTTP-COOKIES.md b/docs/HTTP-COOKIES.md new file mode 100644 index 000000000..a1b283454 --- /dev/null +++ b/docs/HTTP-COOKIES.md @@ -0,0 +1,104 @@ +# HTTP Cookies + +## Cookie overview + + Cookies are `name=contents` pairs that a HTTP server tells the client to + hold and then the client sends back those to the server on subsequent + requests to the same domains and paths for which the cookies were set. + + Cookies are either "session cookies" which typically are forgotten when the + session is over which is often translated to equal when browser quits, or + the cookies aren't session cookies they have expiration dates after which + the client will throw them away. + + Cookies are set to the client with the Set-Cookie: header and are sent to + servers with the Cookie: header. + + For a very long time, the only spec explaining how to use cookies was the + original [Netscape spec from 1994](https://curl.haxx.se/rfc/cookie_spec.html). + + In 2011, [RFC6265](https://www.ietf.org/rfc/rfc6265.txt) was finally + published and details how cookies work within HTTP. + +## Cookies saved to disk + + Netscape once created a file format for storing cookies on disk so that they + would survive browser restarts. curl adopted that file format to allow + sharing the cookies with browsers, only to see browsers move away from that + format. Modern browsers no longer use it, while curl still does. + + The netscape cookie file format stores one cookie per physical line in the + file with a bunch of associated meta data, each field separated with + TAB. That file is called the cookiejar in curl terminology. + + When libcurl saves a cookiejar, it creates a file header of its own in which + there is a URL mention that will link to the web version of this document. + +## Cookies with curl the command line tool + + curl has a full cookie "engine" built in. If you just activate it, you can + have curl receive and send cookies exactly as mandated in the specs. + + Command line options: + + `-b, --cookie` + + tell curl a file to read cookies from and start the cookie engine, or if it + isn't a file it will pass on the given string. -b name=var works and so does + -b cookiefile. + + `-j, --junk-session-cookies` + + when used in combination with -b, it will skip all "session cookies" on load + so as to appear to start a new cookie session. + + `-c, --cookie-jar` + + tell curl to start the cookie engine and write cookies to the given file + after the request(s) + +## Cookies with libcurl + + libcurl offers several ways to enable and interface the cookie engine. These + options are the ones provided by the native API. libcurl bindings may offer + access to them using other means. + + `CURLOPT_COOKIE` + + Is used when you want to specify the exact contents of a cookie header to + send to the server. + + `CURLOPT_COOKIEFILE` + + Tell libcurl to activate the cookie engine, and to read the initial set of + cookies from the given file. Read-only. + + `CURLOPT_COOKIEJAR` + + Tell libcurl to activate the cookie engine, and when the easy handle is + closed save all known cookies to the given cookiejar file. Write-only. + + `CURLOPT_COOKIELIST` + + Provide detailed information about a single cookie to add to the internal + storage of cookies. Pass in the cookie as a HTTP header with all the details + set, or pass in a line from a netscape cookie file. This option can also be + used to flush the cookies etc. + + `CURLINFO_COOKIELIST` + + Extract cookie information from the internal cookie storage as a linked + list. + +## Cookies with javascript + + These days a lot of the web is built up by javascript. The webbrowser loads + complete programs that render the page you see. These javascript programs + can also set and access cookies. + + Since curl and libcurl are plain HTTP clients without any knowledge of or + capability to handle javascript, such cookies will not be detected or used. + + Often, if you want to mimic what a browser does on such web sites, you can + record web browser HTTP traffic when using such a site and then repeat the + cookie operations using curl or libcurl. -- cgit v1.2.3