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Re: $referrer = $_SERVER['HTTP_REFERER'] echo

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Christoph Michael Becker wrote:

> Thomas 'PointedEars' Lahn wrote:
>> Christoph Michael Becker wrote:
>>> Thomas 'PointedEars' Lahn wrote:
>>> Anyway, it seems the regular expression given in Appendix B of RFC 2396
>>> *seems* to be more permissive than the actual syntax given in Appendix
>>> A. 
>> Appendixes are not normative.  Assuming relevance, in which way does it
>> seem more permissive?
> 
> The following example passes the regular expression in Appendix B of RFC
> 2396, but it is not allowed according to Appendix A (if I'm not mistaken):
> 
>   http://http://example.com

You are mistaken.  The relevant productions are:

  URI-reference = [ absoluteURI | relativeURI ] [ "#" fragment ]
  absoluteURI   = scheme ":" ( hier_part | opaque_part )
  scheme        = alpha *( alpha | digit | "+" | "-" | "." )
  hier_part     = ( net_path | abs_path ) [ "?" query ]
  abs_path      = "/"  path_segments
  path_segments = segment *( "/" segment )
  segment       = *pchar *( ";" param )
  pchar         = unreserved | escaped |
                  ":" | "@" | "&" | "=" | "+" | "$" | ","
  unreserved    = alphanum | mark
  mark          = "-" | "_" | "." | "!" | "~" | "*" | "'" |
                  "(" | ")"
  alphanum      = alpha | digit
  alpha         = lowalpha | upalpha
  lowalpha      = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" | "i" |
                  "j" | "k" | "l" | "m" | "n" | "o" | "p" | "q" | "r" |
                  "s" | "t" | "u" | "v" | "w" | "x" | "y" | "z"

Applied:

     URI-reference
  => [ absoluteURI | relativeURI ] [ "#" fragment ]
  => absoluteURI
  => scheme ":" ( hier_part | opaque_part )
  => scheme ":" hier_part
  => scheme ":" ( net_path | abs_path ) [ "?" query ]
  => scheme ":" abs_path
  => scheme ":" "/" path_segments
  => scheme ":" "/" segment *( "/" segment )
  => scheme ":" "/" segment "/" segment "/" segment "/" segment
  => scheme ":" "/" *pchar *( ";" param ) "/" *pchar *( ";" param ) "/" 
*pchar *( ";" param ) "/" *pchar *( ";" param )
  => scheme ":" "/" *pchar "/" *pchar "/" *pchar "/" *pchar
  => scheme ":" "/" "" "/" pchar pchar pchar pchar pchar "/" "" "/" pchar 
pchar pchar pchar pchar pchar pchar pchar pchar pchar pchar
  => scheme ":" "/" "" "/" unreserved unreserved unreserved unreserved ":" 
"/" "" "/" unreserved unreserved unreserved unreserved unreserved unreserved 
unreserved unreserved unreserved unreserved unreserved
  => scheme ":" "/" "" "/" alphanum alphanum alphanum alphanum ":" "/" "" 
"/" alphanum alphanum alphanum alphanum alphanum alphanum alphanum mark 
alphanum alphanum alphanum
  => scheme ":" "/" "" "/" alpha alpha alpha alpha ":" "/" "" "/" alpha 
alpha alpha alpha alpha alpha alpha mark alpha alpha alpha
  => scheme ":" "/" "" "/" lowalpha lowalpha lowalpha lowalpha ":" "/" "" 
"/" lowalpha lowalpha lowalpha lowalpha lowalpha lowalpha lowalpha mark 
lowalpha lowalpha lowalpha
  => scheme ":" "/" "" "/" "h" "t" "t" "p" ":" "/" "" "/" "e" "x" "a" "m" 
"p" "l" "e" "." "c" "o" "m"
  => alpha *( alpha | digit | "+" | "-" | "." ) ":" "/" "" "/" "h" "t" "t" 
"p" ":" "/" "" "/" "e" "x" "a" "m" "p" "l" "e" "." "c" "o" "m"
  => alpha alpha alpha alpha ":" "/" "" "/" "h" "t" "t" "p" ":" "/" "" "/" 
"e" "x" "a" "m" "p" "l" "e" "." "c" "o" "m"
  => lowalpha lowalpha lowalpha lowalpha ":" "/" "" "/" "h" "t" "t" "p" ":" 
"/" "e" "x" "a" "m" "p" "l" "e" "." "c" "o" "m"
  => "h" "t" "t" "p" ":" "/" "" "/" "h" "t" "t" "p" ":" "/" "" "/" "e" "x" 
"a" "m" "p" "l" "e" "." "c" "o" "m"
  => "http://http:/example.com"

[Some day I'll write an automatic grammar resolver.  And I should let prove 
other people their unfounded statements instead of going to lengths 
disproving them.]
  
These productions were probably not intended.  But note that the section is 
titled “*Parsing* a URI Reference with a Regular Expression”, _not_ 
“*Validating* a URI Reference”, and that URI References also include things 
like “javascript:window.alert("42");”.
 
>>> I have not checked RFC 3986 regarding this issue yet.
>>>
>>>> But I would never check against the HTTP-Referer [sic!] in the first
>>>> place. There are much more reliable solutions, like session variables.
>>>> See also <https://owasp.org/>.
>>>
>>> ACK.  OTOH I have some concerns regarding cookies (I do not "like" to
>>> propagate session IDs as a GET parameter) due to the European cookie
>>> law(s).
>> 
>> Directive 95/46/EC does not apply here.
> 
> I was referring to directive 2009/136/EC, which *might* apply.

How?


PointedEars 
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(This won't prevent people from viewing your source, but no one
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$referrer = $_SERVER['HTTP_REFERER'] echo Twayne <nobody@spamcop.net> - 2013-06-27 17:23 -0400
  RESOLVED Re: $referrer = $_SERVER['HTTP_REFERER'] echo Twayne <nobody@spamcop.net> - 2013-06-27 17:34 -0400
  Re: $referrer = $_SERVER['HTTP_REFERER'] echo Christoph Michael Becker <cmbecker69@arcor.de> - 2013-06-27 23:40 +0200
    Re: $referrer = $_SERVER['HTTP_REFERER'] echo Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-06-28 00:19 +0200
      Re: $referrer = $_SERVER['HTTP_REFERER'] echo Christoph Michael Becker <cmbecker69@arcor.de> - 2013-06-28 02:16 +0200
        Re: $referrer = $_SERVER['HTTP_REFERER'] echo Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-06-28 10:56 +0200
          Re: $referrer = $_SERVER['HTTP_REFERER'] echo Christoph Michael Becker <cmbecker69@arcor.de> - 2013-06-28 20:03 +0200
            Re: $referrer = $_SERVER['HTTP_REFERER'] echo Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-06-28 21:49 +0200
              Re: $referrer = $_SERVER['HTTP_REFERER'] echo Christoph Michael Becker <cmbecker69@arcor.de> - 2013-06-28 22:37 +0200
                Re: $referrer = $_SERVER['HTTP_REFERER'] echo Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-06-28 23:55 +0200
      Re: $referrer = $_SERVER['HTTP_REFERER'] echo Twayne <nobody@spamcop.net> - 2013-06-28 13:49 -0400
        Re: $referrer = $_SERVER['HTTP_REFERER'] echo Christoph Michael Becker <cmbecker69@arcor.de> - 2013-06-28 20:13 +0200
    Re: $referrer = $_SERVER['HTTP_REFERER'] echo Twayne <nobody@spamcop.net> - 2013-06-28 13:33 -0400
  Re: $referrer = $_SERVER['HTTP_REFERER'] echo Jerry Stuckle <jstucklex@attglobal.net> - 2013-06-27 17:52 -0400
    Re: $referrer = $_SERVER['HTTP_REFERER'] echo Twayne <nobody@spamcop.net> - 2013-06-28 14:07 -0400
      Re: $referrer = $_SERVER['HTTP_REFERER'] echo Jerry Stuckle <jstucklex@attglobal.net> - 2013-06-28 15:26 -0400
        Re: $referrer = $_SERVER['HTTP_REFERER'] echo Twayne <nobody@spamcop.net> - 2013-06-28 16:03 -0400
          Re: $referrer = $_SERVER['HTTP_REFERER'] echo Jerry Stuckle <jstucklex@attglobal.net> - 2013-06-28 16:07 -0400
            Re: $referrer = $_SERVER['HTTP_REFERER'] echo Christoph Michael Becker <cmbecker69@arcor.de> - 2013-06-28 22:46 +0200
              Re: $referrer = $_SERVER['HTTP_REFERER'] echo Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-06-28 23:58 +0200

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