Re: PHP processing steps to apply to a URL to make it safe

From	James Harris <james.harris.1@gmail.com>
Newsgroups	comp.lang.php
Subject	Re: PHP processing steps to apply to a URL to make it safe
Date	2016-02-20 21:37 +0000
Organization	A noiseless patient Spider
Message-ID	<naam5p$2g0$1@dont-email.me> (permalink)
References	(1 earlier) <56C445F6.1090008@arnowelzel.de> <na220i$27e$1@dont-email.me> <56C56CA2.6060601@arnowelzel.de> <naaekp$56c$1@dont-email.me> <2794285.GF34IQqVtz@PointedEars.de>

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On 20/02/2016 20:37, Thomas 'PointedEars' Lahn wrote:
> James Harris wrote:
>
>> Well, as was pointed out to me, after passing the request_uri through
>> (raw)urldecode the resulting string might not have ASCII coding and so
>
> ASCII _encoding_, and it *certainly* is not encoded using US-ASCII.
> AISB, US-ASCII is a *7*-bit encoding.

I know. As with a previous post of yours that I haven't got round to 
replying to yet I was referring to the report from mb_detect_encoding(). 
It reports ASCII or UTF-8 in my tests. I can choose to permit only ASCII 
strings.

>> would not be suitable for byte-wise processing. That is a bit of a gotcha.
>
> <http://php.net/manual/en/ref.mbstring.php>

Thanks. I have a lot to read.

...

>> 3. add a leading slash if there is not one
>
> To what end?

I thought that I got a response from one test where the result did not 
have a leading slash. I didn't make a note of the details so am not so 
sure now but it does not matter much. Forcing there to be a leading 
slash costs next to nothing, guards against the possibility of that 
happening, and makes later processing (including certain misbehaving PHP 
functions) simpler.

>> 4. split by slash characters
>
> That would leave an empty first element of the resulting array, …
>
>> 5. check that each part is nonblank and has a suitable form for a key
>
> … so this test would fail.

Yes. I was not as precise in my description as I was in the code.

> I still think that your approach is wrong, but unless you state your use-
> case in more detail, I cannot be certain.
>
>> I might add a check that all letters are lower case. That would help
>> generate a consistent response irrespective of the OS the script were to
>> run on.
>
> So you are mapping URI paths to files.  Know then that it is not so much a
> matter of the operating system, but of the *file* system how filenames
> are handled.  Also, it is inherently unsafe.  Why are you doing this?

Not exactly. Let me take a small step backwards to try to explain better.

The idea is, first, that the entire URL is a globally unique key for the 
data being addressed. Except as defined by certain rules which 
complicate this a bit but are not relevant here there should not be 
multiple URLs which map to the same data. I therefore vet the URLs that 
my PHP script sees to make sure that they do not contain any redundant 
information, and I do not allow directory manipulations such as are 
often allowed for filesystem access (especially dot and double-dot entries).

Second, the elements of the URL are not filesystem locations. They are 
keys. My current code maps those keys to directories but it could just 
as well map them to something else like a database.

Third, the URLs are to be permanent or as long-lasting as is feasible. A 
given URL should remain valid even if the underlying storage system is 
changed. Basically, the unique URLs and the keys they contain are 
intended to outlive the implementation method.

IMO it is best initially to require that the keys (which are presented 
to the PHP script by means of the URL) be simple. Restrictions can then 
be relaxed without breaking existing URLs.

Do you still think that the approach is unsafe?

James

Thread

PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-17 09:37 +0000
  Re: PHP processing steps to apply to a URL to make it safe Arno Welzel <usenet@arnowelzel.de> - 2016-02-17 11:05 +0100
    Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-17 15:04 +0000
      Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-17 10:54 -0500
        Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-18 01:09 +0000
          Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-17 21:12 -0500
            Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-20 19:07 +0000
              Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-20 21:07 +0100
                Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-20 20:35 +0000
                Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-20 21:40 +0100
                Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-20 21:02 +0000
              Re: PHP processing steps to apply to a URL to make it safe gordonb.lkcah@burditt.org (Gordon Burditt) - 2016-02-29 21:29 -0600
      Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-17 23:33 +0100
        Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-18 01:12 +0000
          Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-18 21:48 +0100
        Re: PHP processing steps to apply to a URL to make it safe Arno Welzel <usenet@arnowelzel.de> - 2016-02-18 08:05 +0100
          Re: PHP processing steps to apply to a URL to make it safe Tim Streater <timstreater@greenbee.net> - 2016-02-18 09:59 +0000
            Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-18 10:29 +0000
              Re: PHP processing steps to apply to a URL to make it safe Tim Streater <timstreater@greenbee.net> - 2016-02-18 11:36 +0000
            Re: PHP processing steps to apply to a URL to make it safe Arno Welzel <usenet@arnowelzel.de> - 2016-02-18 15:44 +0100
          Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-18 21:47 +0100
      Re: PHP processing steps to apply to a URL to make it safe Arno Welzel <usenet@arnowelzel.de> - 2016-02-18 08:02 +0100
        Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-20 19:29 +0000
          Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-20 21:37 +0100
            Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-20 21:37 +0000
              Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-21 15:02 +0100
                Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-21 15:02 +0000
  Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-17 08:19 -0500
    Re: PHP processing steps to apply to a URL to make it safe "R.Wieser" <address@not.available> - 2016-02-17 14:43 +0100
      Re: PHP processing steps to apply to a URL to make it safe Arno Welzel <usenet@arnowelzel.de> - 2016-02-17 15:04 +0100
        Re: PHP processing steps to apply to a URL to make it safe "R.Wieser" <address@not.available> - 2016-02-17 15:17 +0100
          Re: PHP processing steps to apply to a URL to make it safe Arno Welzel <usenet@arnowelzel.de> - 2016-02-17 15:47 +0100
            Re: PHP processing steps to apply to a URL to make it safe "R.Wieser" <address@not.available> - 2016-02-17 15:57 +0100
              Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-17 10:57 -0500
                Re: PHP processing steps to apply to a URL to make it safe "R.Wieser" <address@not.available> - 2016-02-17 17:10 +0100
                Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-17 12:11 -0500
                Re: PHP processing steps to apply to a URL to make it safe "R.Wieser" <address@not.available> - 2016-02-17 18:51 +0100
                Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-17 12:55 -0500
              Re: PHP processing steps to apply to a URL to make it safe Arno Welzel <usenet@arnowelzel.de> - 2016-02-17 19:06 +0100
                Re: PHP processing steps to apply to a URL to make it safe "R.Wieser" <address@not.available> - 2016-02-17 20:19 +0100
                Re: PHP processing steps to apply to a URL to make it safe Arno Welzel <usenet@arnowelzel.de> - 2016-02-18 08:18 +0100
                Re: PHP processing steps to apply to a URL to make it safe "R.Wieser" <address@not.available> - 2016-02-18 09:20 +0100
                Re: PHP processing steps to apply to a URL to make it safe Arno Welzel <usenet@arnowelzel.de> - 2016-02-18 15:48 +0100
                Re: PHP processing steps to apply to a URL to make it safe "R.Wieser" <address@not.available> - 2016-02-18 16:25 +0100
                Re: PHP processing steps to apply to a URL to make it safe Arno Welzel <usenet@arnowelzel.de> - 2016-02-18 17:00 +0100
                Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-18 22:26 +0100
                Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-18 10:48 -0500
            Re: PHP processing steps to apply to a URL to make it safe "Christoph M. Becker" <cmbecker69@arcor.de> - 2016-02-17 16:38 +0100
              Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-17 10:56 -0500
              Re: PHP processing steps to apply to a URL to make it safe Arno Welzel <usenet@arnowelzel.de> - 2016-02-17 19:08 +0100
              Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-17 23:35 +0100
          Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-17 09:56 -0500
            Re: PHP processing steps to apply to a URL to make it safe "R.Wieser" <address@not.available> - 2016-02-17 16:44 +0100
              Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-17 12:12 -0500
                Re: PHP processing steps to apply to a URL to make it safe "R.Wieser" <address@not.available> - 2016-02-17 19:04 +0100
      Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-17 09:55 -0500
        Re: PHP processing steps to apply to a URL to make it safe "R.Wieser" <address@not.available> - 2016-02-17 16:39 +0100
          Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-17 11:00 -0500
    Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-17 15:15 +0000
      Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-17 11:05 -0500
        Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-18 01:18 +0000
      Re: PHP processing steps to apply to a URL to make it safe Arno Welzel <usenet@arnowelzel.de> - 2016-02-17 19:14 +0100
        Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-18 00:19 +0000
      Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-17 23:36 +0100
  Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-17 23:26 +0100
    Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-18 00:36 +0000
      Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-18 22:03 +0100
        Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-20 19:38 +0000
          Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-20 21:17 +0100
            Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-20 20:56 +0000
              Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-20 23:48 +0100
                Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-21 09:37 +0000
                Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-21 14:42 +0100
                Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-21 15:03 +0000
                Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-21 14:09 -0500
                Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-21 19:34 +0000
                Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-21 14:49 -0500
                Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-21 19:56 +0000
                Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-21 20:29 -0500
                Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-22 07:30 +0000
                Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-22 08:13 -0500
                Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-22 15:01 +0000
                Re: PHP processing steps to apply to a URL to make it safe Jerry Stuckle <jstucklex@attglobal.net> - 2016-02-22 10:31 -0500
                Re: PHP processing steps to apply to a URL to make it safe Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-22 00:10 +0100
                Re: PHP processing steps to apply to a URL to make it safe James Harris <james.harris.1@gmail.com> - 2016-02-21 23:45 +0000
  Re: PHP processing steps to apply to a URL to make it safe pittendrigh <Sandy.Pittendrigh@gmail.com> - 2016-03-22 05:23 -0700

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