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1.1       misho       1: # HTTP Cookies
                      2: 
                      3: ## Cookie overview
                      4: 
                      5:   Cookies are `name=contents` pairs that a HTTP server tells the client to
                      6:   hold and then the client sends back those to the server on subsequent
                      7:   requests to the same domains and paths for which the cookies were set.
                      8: 
                      9:   Cookies are either "session cookies" which typically are forgotten when the
                     10:   session is over which is often translated to equal when browser quits, or
                     11:   the cookies aren't session cookies they have expiration dates after which
                     12:   the client will throw them away.
                     13: 
                     14:   Cookies are set to the client with the Set-Cookie: header and are sent to
                     15:   servers with the Cookie: header.
                     16: 
                     17:   For a very long time, the only spec explaining how to use cookies was the
                     18:   original [Netscape spec from 1994](https://curl.haxx.se/rfc/cookie_spec.html).
                     19: 
                     20:   In 2011, [RFC6265](https://www.ietf.org/rfc/rfc6265.txt) was finally
                     21:   published and details how cookies work within HTTP. In 2016, an update which
                     22:   added support for prefixes was
                     23:   [proposed](https://tools.ietf.org/html/draft-ietf-httpbis-cookie-prefixes-00),
                     24:   and in 2017, another update was
                     25:   [drafted](https://tools.ietf.org/html/draft-ietf-httpbis-cookie-alone-01)
                     26:   to deprecate modification of 'secure' cookies from non-secure origins. Both
                     27:   of these drafts have been incorporated into a proposal to
                     28:   [replace](https://tools.ietf.org/html/draft-ietf-httpbis-rfc6265bis-02)
                     29:   RFC6265. Cookie prefixes and secure cookie modification protection has been
                     30:   implemented by curl.
                     31: 
                     32: ## Cookies saved to disk
                     33: 
                     34:   Netscape once created a file format for storing cookies on disk so that they
                     35:   would survive browser restarts. curl adopted that file format to allow
                     36:   sharing the cookies with browsers, only to see browsers move away from that
                     37:   format. Modern browsers no longer use it, while curl still does.
                     38: 
                     39:   The netscape cookie file format stores one cookie per physical line in the
                     40:   file with a bunch of associated meta data, each field separated with
                     41:   TAB. That file is called the cookiejar in curl terminology.
                     42: 
                     43:   When libcurl saves a cookiejar, it creates a file header of its own in which
                     44:   there is a URL mention that will link to the web version of this document.
                     45: 
                     46: ## Cookie file format
                     47: 
                     48:   The cookie file format is text based and stores one cookie per line. Lines
                     49:   that start with `#` are treated as comments.
                     50: 
                     51:   Each line that each specifies a single cookie consists of seven text fields
                     52:   separated with TAB characters. A valid line must end with a newline
                     53:   character.
                     54: 
                     55: ### Fields in the file
                     56: 
                     57:   Field number, what type and example data and the meaning of it:
                     58: 
                     59:   0. string `example.com` - the domain name
                     60:   1. boolean `FALSE` - include subdomains
                     61:   2. string `/foobar/` - path
                     62:   3. boolean `TRUE` - send/receive over HTTPS only
                     63:   4. number `1462299217` - expires at - seconds since Jan 1st 1970, or 0
                     64:   5. string `person` - name of the cookie
                     65:   6. string `daniel` - value of the cookie
                     66: 
                     67: ## Cookies with curl the command line tool
                     68: 
                     69:   curl has a full cookie "engine" built in. If you just activate it, you can
                     70:   have curl receive and send cookies exactly as mandated in the specs.
                     71: 
                     72:   Command line options:
                     73: 
                     74:   `-b, --cookie`
                     75: 
                     76:   tell curl a file to read cookies from and start the cookie engine, or if it
                     77:   isn't a file it will pass on the given string. -b name=var works and so does
                     78:   -b cookiefile.
                     79: 
                     80:   `-j, --junk-session-cookies`
                     81: 
                     82:   when used in combination with -b, it will skip all "session cookies" on load
                     83:   so as to appear to start a new cookie session.
                     84: 
                     85:   `-c, --cookie-jar`
                     86: 
                     87:   tell curl to start the cookie engine and write cookies to the given file
                     88:   after the request(s)
                     89: 
                     90: ## Cookies with libcurl
                     91: 
                     92:   libcurl offers several ways to enable and interface the cookie engine. These
                     93:   options are the ones provided by the native API. libcurl bindings may offer
                     94:   access to them using other means.
                     95: 
                     96:   `CURLOPT_COOKIE`
                     97: 
                     98:   Is used when you want to specify the exact contents of a cookie header to
                     99:   send to the server.
                    100: 
                    101:   `CURLOPT_COOKIEFILE`
                    102: 
                    103:   Tell libcurl to activate the cookie engine, and to read the initial set of
                    104:   cookies from the given file. Read-only.
                    105: 
                    106:   `CURLOPT_COOKIEJAR`
                    107: 
                    108:   Tell libcurl to activate the cookie engine, and when the easy handle is
                    109:   closed save all known cookies to the given cookiejar file. Write-only.
                    110: 
                    111:   `CURLOPT_COOKIELIST`
                    112: 
                    113:   Provide detailed information about a single cookie to add to the internal
                    114:   storage of cookies. Pass in the cookie as a HTTP header with all the details
                    115:   set, or pass in a line from a netscape cookie file. This option can also be
                    116:   used to flush the cookies etc.
                    117: 
                    118:   `CURLINFO_COOKIELIST`
                    119: 
                    120:   Extract cookie information from the internal cookie storage as a linked
                    121:   list.
                    122: 
                    123: ## Cookies with javascript
                    124: 
                    125:   These days a lot of the web is built up by javascript. The webbrowser loads
                    126:   complete programs that render the page you see. These javascript programs
                    127:   can also set and access cookies.
                    128: 
                    129:   Since curl and libcurl are plain HTTP clients without any knowledge of or
                    130:   capability to handle javascript, such cookies will not be detected or used.
                    131: 
                    132:   Often, if you want to mimic what a browser does on such web sites, you can
                    133:   record web browser HTTP traffic when using such a site and then repeat the
                    134:   cookie operations using curl or libcurl.