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I am trying to construct a rewrite condition and rule to rewrite URLs with & in the query string, rather than just &. This has occurred because of some invalid encoding when the URL is transmitted to a client in XML. Long term that will be fixed, but short term if I can put a rewrite rule in place it will stop 404 errors.

An example URL is

https://myserver.com/getpdf/download?md5=53d64aee8107d8f8af0c&id=163464591&tz=GMT

So far I have got this

RewriteCond %{REQUEST_URI} ^/getpdf/download* RewriteRule ^/([^&]+)(&)(.*)$ /$1&$2 [N]

based on other posts on serverfault (eg mod-rewrite: Replacing some characters in a url)

I turned on the rewrite log and this is what I see

10.0.0.64 - - [12/Mar/2016:06:42:52 +0000] [myserver.com/sid#7f24e32103e8][rid#7f24e3379870/initial] (2) init rewrite engine with requested uri /getpdf/download 10.0.0.64 - - [12/Mar/2016:06:42:52 +0000] [myserver.com/sid#7f24e32103e8][rid#7f24e3379870/initial] (3) applying pattern '^(md5)([^&]+)(&)(.*)$' to uri '/getpdf/download' 10.0.0.64 - - [12/Mar/2016:06:42:52 +0000] [myserver.com/sid#7f24e32103e8][rid#7f24e3379870/initial] (1) pass through /getpdf/download

Any guidance on how to correctly form the rewriterule would be great.

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2 Answers 2

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Apache documentation states that if you want to rewrite query string part of the URI, then you need to use RewriteCond %{QUERY_STRING}.

So, you should try this:

RewriteCond %{QUERY_STRING} md5=([0-9a-f]{20}(&)(id=[0-9]+)(&)(.*) RewriteRule ^md5=([0-9a-f]{20}(&)id=([0-9]+)(&)(.*)$ md5=$1&id=$2&$3 [N]
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  • Tero, thanks for your pointers. The answer needed some more tweaking, I'm going to post the solution now. Commented Mar 14, 2016 at 13:47
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With the help of Teros answer pointing me in the right direction I solved my rewrite rule.

First step was to match against %{QUERY_STRING}.

RewriteCond %{QUERY_STRING} ^md5=([0-9a-f])(&)id=([0-9])(&)(.*)$

And the second step was to rewrite the entire URL. My mistake was in thinking that I could modify only the query string. 

RewriteRule ^(.*)$ https://myserver.com/getpdf/download?md5=%1&id=%3&%5 [N]

Some tips

  • %1 in the RewriteRule uses groups from the RewriteCond
  • $1 would use groups from the regex in the RewriteRule instead
  • Rewrite uses Perl Compatible Regular Expressions (PCRE). I used this tester to check my regex - https://regex101.com/#pcre
  • Google "Learn Apache mod_rewrite: 13 Real-world Examples"
  • The apache intro to rewrite, and the image showing the basics, helps - https://httpd.apache.org/docs/2.4/en/rewrite/intro.html (essentially a case of RTFM :) )

Hope this helps others lost in the world of rewrite.

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