Using mod_rewrite to control access

Available Languages: en | diff --git a/docs/manual/rewrite/rewrite_guide.xml b/docs/manual/rewrite/rewrite_guide.xml index 7f996fc1ab..9df0686046 100644 --- a/docs/manual/rewrite/rewrite_guide.xml +++ b/docs/manual/rewrite/rewrite_guide.xml @@ -822,5 +822,1234 @@ while (<>) { +

+ + Web Cluster with Consistent URL Space + +

Description:

We want to create a homogeneous and consistent URL + layout across all WWW servers on an Intranet web cluster, i.e., + all URLs (by definition server-local and thus + server-dependent!) become server independent! + What we want is to give the WWW namespace a single consistent + layout: no URL should refer to + any particular target server. The cluster itself + should connect users automatically to a physical target + host as needed, invisibly.

Solution:

First, the knowledge of the target servers comes from + (distributed) external maps which contain information on + where our users, groups, and entities reside. They have the + form:

+ +

+user1  server_of_user1
+user2  server_of_user2
+:      :
+

+ +

We put them into files map.xxx-to-host. + Second we need to instruct all servers to redirect URLs + of the forms:

+ +

+/u/user/anypath
+/g/group/anypath
+/e/entity/anypath
+

+ +

+http://physical-host/u/user/anypath
+http://physical-host/g/group/anypath
+http://physical-host/e/entity/anypath
+

+ +

when any URL path need not be valid on every server. The + following ruleset does this for us with the help of the map + files (assuming that server0 is a default server which + will be used if a user has no entry in the map):

+ +

+RewriteEngine on
+
+RewriteMap      user-to-host   txt:/path/to/map.user-to-host
+RewriteMap     group-to-host   txt:/path/to/map.group-to-host
+RewriteMap    entity-to-host   txt:/path/to/map.entity-to-host
+
+RewriteRule   ^/u/([^/]+)/?(.*)   http://${user-to-host:$1|server0}/u/$1/$2
+RewriteRule   ^/g/([^/]+)/?(.*)  http://${group-to-host:$1|server0}/g/$1/$2
+RewriteRule   ^/e/([^/]+)/?(.*) http://${entity-to-host:$1|server0}/e/$1/$2
+
+RewriteRule   ^/([uge])/([^/]+)/?$          /$1/$2/.www/
+RewriteRule   ^/([uge])/([^/]+)/([^.]+.+)   /$1/$2/.www/$3\
+

+ +

+ + Structured Homedirs + +

Description:

Some sites with thousands of users use a + structured homedir layout, i.e. each homedir is in a + subdirectory which begins (for instance) with the first + character of the username. So, /~foo/anypath + is /home/f/foo/.www/anypath + while /~bar/anypath is + /home/b/bar/.www/anypath.

Solution:

We use the following ruleset to expand the tilde URLs + into the above layout.

+ +

+RewriteEngine on
+RewriteRule   ^/~(([a-z])[a-z0-9]+)(.*)  /home/$2/$1/.www$3
+

+ +

+ + Filesystem Reorganization + +

Description:

This really is a hardcore example: a killer application + which heavily uses per-directory + RewriteRules to get a smooth look and feel + on the Web while its data structure is never touched or + adjusted. Background: net.sw is + my archive of freely available Unix software packages, + which I started to collect in 1992. It is both my hobby + and job to do this, because while I'm studying computer + science I have also worked for many years as a system and + network administrator in my spare time. Every week I need + some sort of software so I created a deep hierarchy of + directories where I stored the packages:

+ +

+drwxrwxr-x   2 netsw  users    512 Aug  3 18:39 Audio/
+drwxrwxr-x   2 netsw  users    512 Jul  9 14:37 Benchmark/
+drwxrwxr-x  12 netsw  users    512 Jul  9 00:34 Crypto/
+drwxrwxr-x   5 netsw  users    512 Jul  9 00:41 Database/
+drwxrwxr-x   4 netsw  users    512 Jul 30 19:25 Dicts/
+drwxrwxr-x  10 netsw  users    512 Jul  9 01:54 Graphic/
+drwxrwxr-x   5 netsw  users    512 Jul  9 01:58 Hackers/
+drwxrwxr-x   8 netsw  users    512 Jul  9 03:19 InfoSys/
+drwxrwxr-x   3 netsw  users    512 Jul  9 03:21 Math/
+drwxrwxr-x   3 netsw  users    512 Jul  9 03:24 Misc/
+drwxrwxr-x   9 netsw  users    512 Aug  1 16:33 Network/
+drwxrwxr-x   2 netsw  users    512 Jul  9 05:53 Office/
+drwxrwxr-x   7 netsw  users    512 Jul  9 09:24 SoftEng/
+drwxrwxr-x   7 netsw  users    512 Jul  9 12:17 System/
+drwxrwxr-x  12 netsw  users    512 Aug  3 20:15 Typesetting/
+drwxrwxr-x  10 netsw  users    512 Jul  9 14:08 X11/
+

+ +

In July 1996 I decided to make this archive public to + the world via a nice Web interface. "Nice" means that I + wanted to offer an interface where you can browse + directly through the archive hierarchy. And "nice" means + that I didn't want to change anything inside this + hierarchy - not even by putting some CGI scripts at the + top of it. Why? Because the above structure should later be + accessible via FTP as well, and I didn't want any + Web or CGI stuff mixed in there.

Solution:

The solution has two parts: The first is a set of CGI + scripts which create all the pages at all directory + levels on-the-fly. I put them under + /e/netsw/.www/ as follows:

+ +

+-rw-r--r--   1 netsw  users    1318 Aug  1 18:10 .wwwacl
+drwxr-xr-x  18 netsw  users     512 Aug  5 15:51 DATA/
+-rw-rw-rw-   1 netsw  users  372982 Aug  5 16:35 LOGFILE
+-rw-r--r--   1 netsw  users     659 Aug  4 09:27 TODO
+-rw-r--r--   1 netsw  users    5697 Aug  1 18:01 netsw-about.html
+-rwxr-xr-x   1 netsw  users     579 Aug  2 10:33 netsw-access.pl
+-rwxr-xr-x   1 netsw  users    1532 Aug  1 17:35 netsw-changes.cgi
+-rwxr-xr-x   1 netsw  users    2866 Aug  5 14:49 netsw-home.cgi
+drwxr-xr-x   2 netsw  users     512 Jul  8 23:47 netsw-img/
+-rwxr-xr-x   1 netsw  users   24050 Aug  5 15:49 netsw-lsdir.cgi
+-rwxr-xr-x   1 netsw  users    1589 Aug  3 18:43 netsw-search.cgi
+-rwxr-xr-x   1 netsw  users    1885 Aug  1 17:41 netsw-tree.cgi
+-rw-r--r--   1 netsw  users     234 Jul 30 16:35 netsw-unlimit.lst
+

+ +

The DATA/ subdirectory holds the above + directory structure, i.e. the real + net.sw stuff, and gets + automatically updated via rdist from time to + time. The second part of the problem remains: how to link + these two structures together into one smooth-looking URL + tree? We want to hide the DATA/ directory + from the user while running the appropriate CGI scripts + for the various URLs. Here is the solution: first I put + the following into the per-directory configuration file + in the DocumentRoot + of the server to rewrite the public URL path + /net.sw/ to the internal path + /e/netsw:

+ +

+RewriteRule  ^net.sw$       net.sw/        [R]
+RewriteRule  ^net.sw/(.*)$  e/netsw/$1
+

+ +

The first rule is for requests which miss the trailing + slash! The second rule does the real thing. And then + comes the killer configuration which stays in the + per-directory config file + /e/netsw/.www/.wwwacl:

+ +

+Options       ExecCGI FollowSymLinks Includes MultiViews
+
+RewriteEngine on
+
+#  we are reached via /net.sw/ prefix
+RewriteBase   /net.sw/
+
+#  first we rewrite the root dir to
+#  the handling cgi script
+RewriteRule   ^$                       netsw-home.cgi     [L]
+RewriteRule   ^index\.html$            netsw-home.cgi     [L]
+
+#  strip out the subdirs when
+#  the browser requests us from perdir pages
+RewriteRule   ^.+/(netsw-[^/]+/.+)$    $1                 [L]
+
+#  and now break the rewriting for local files
+RewriteRule   ^netsw-home\.cgi.*       -                  [L]
+RewriteRule   ^netsw-changes\.cgi.*    -                  [L]
+RewriteRule   ^netsw-search\.cgi.*     -                  [L]
+RewriteRule   ^netsw-tree\.cgi$        -                  [L]
+RewriteRule   ^netsw-about\.html$      -                  [L]
+RewriteRule   ^netsw-img/.*$           -                  [L]
+
+#  anything else is a subdir which gets handled
+#  by another cgi script
+RewriteRule   !^netsw-lsdir\.cgi.*     -                  [C]
+RewriteRule   (.*)                     netsw-lsdir.cgi/$1
+

+ +

Some hints for interpretation:

+ +

Notice the L (last) flag and no + substitution field ('-') in the fourth part
Notice the ! (not) character and + the C (chain) flag at the first rule + in the last part
Notice the catch-all pattern in the last rule

+ +

+ + Redirect Failing URLs to Another Web Server + +

Description:

A typical FAQ about URL rewriting is how to redirect + failing requests on webserver A to webserver B. Usually + this is done via ErrorDocument CGI scripts in Perl, but + there is also a mod_rewrite solution. + But note that this performs more poorly than using an + ErrorDocument + CGI script!

Solution:

The first solution has the best performance but less + flexibility, and is less safe:

+ +

+RewriteEngine on
+RewriteCond   %{DOCUMENT_ROOT/%{REQUEST_URI} !-f
+RewriteRule   ^(.+)                             http://webserverB.dom/$1
+

+ +

The problem here is that this will only work for pages + inside the DocumentRoot. While you can add more + Conditions (for instance to also handle homedirs, etc.) + there is a better variant:

+ +

+RewriteEngine on
+RewriteCond   %{REQUEST_URI} !-U
+RewriteRule   ^(.+)          http://webserverB.dom/$1
+

+ +

This uses the URL look-ahead feature of mod_rewrite. + The result is that this will work for all types of URLs + and is safe. But it does have a performance impact on + the web server, because for every request there is one + more internal subrequest. So, if your web server runs on a + powerful CPU, use this one. If it is a slow machine, use + the first approach or better an ErrorDocument CGI script.

+ +

+ + Archive Access Multiplexer + +

Description:

Do you know the great CPAN (Comprehensive Perl Archive + Network) under http://www.perl.com/CPAN? + CPAN automatically redirects browsers to one of many FTP + servers around the world (generally one near the requesting + client); each server carries a full CPAN mirror. This is + effectively an FTP access multiplexing service. + CPAN runs via CGI scripts, but how could a similar approach + be implemented via mod_rewrite?

Solution:

First we notice that as of version 3.0.0, + mod_rewrite can + also use the "ftp:" scheme on redirects. + And second, the location approximation can be done by a + RewriteMap + over the top-level domain of the client. + With a tricky chained ruleset we can use this top-level + domain as a key to our multiplexing map.

+ +

+RewriteEngine on
+RewriteMap    multiplex                txt:/path/to/map.cxan
+RewriteRule   ^/CxAN/(.*)              %{REMOTE_HOST}::$1                 [C]
+RewriteRule   ^.+\.([a-zA-Z]+)::(.*)$  ${multiplex:$1|ftp.default.dom}$2  [R,L]
+

+ +

+##
+##  map.cxan -- Multiplexing Map for CxAN
+##
+
+de        ftp://ftp.cxan.de/CxAN/
+uk        ftp://ftp.cxan.uk/CxAN/
+com       ftp://ftp.cxan.com/CxAN/
+ :
+##EOF##
+

+ +

+ + Browser Dependent Content + +

Description:

At least for important top-level pages it is sometimes + necessary to provide the optimum of browser dependent + content, i.e., one has to provide one version for + current browsers, a different version for the Lynx and text-mode + browsers, and another for other browsers.

Solution:

We cannot use content negotiation because the browsers do + not provide their type in that form. Instead we have to + act on the HTTP header "User-Agent". The following config + does the following: If the HTTP header "User-Agent" + begins with "Mozilla/3", the page foo.html + is rewritten to foo.NS.html and the + rewriting stops. If the browser is "Lynx" or "Mozilla" of + version 1 or 2, the URL becomes foo.20.html. + All other browsers receive page foo.32.html. + This is done with the following ruleset:

+ +

+RewriteCond %{HTTP_USER_AGENT}  ^Mozilla/3.*
+RewriteRule ^foo\.html$         foo.NS.html          [L]
+
+RewriteCond %{HTTP_USER_AGENT}  ^Lynx/.*         [OR]
+RewriteCond %{HTTP_USER_AGENT}  ^Mozilla/[12].*
+RewriteRule ^foo\.html$         foo.20.html          [L]
+
+RewriteRule ^foo\.html$         foo.32.html          [L]
+

+ +

+ + Dynamic Mirror + +

Description:

Assume there are nice web pages on remote hosts we want + to bring into our namespace. For FTP servers we would use + the mirror program which actually maintains an + explicit up-to-date copy of the remote data on the local + machine. For a web server we could use the program + webcopy which runs via HTTP. But both + techniques have a major drawback: The local copy is + always only as up-to-date as the last time we ran the program. It + would be much better if the mirror was not a static one we + have to establish explicitly. Instead we want a dynamic + mirror with data which gets updated automatically + as needed on the remote host(s).

Solution:

To provide this feature we map the remote web page or even + the complete remote web area to our namespace by the use + of the Proxy Throughput feature + (flag [P]):

+ +

+RewriteEngine  on
+RewriteBase    /~quux/
+RewriteRule    ^hotsheet/(.*)$  http://www.tstimpreso.com/hotsheet/$1  [P]
+

+ +

+RewriteEngine  on
+RewriteBase    /~quux/
+RewriteRule    ^usa-news\.html$   http://www.quux-corp.com/news/index.html  [P]
+

+ +

+ + Reverse Dynamic Mirror + +

Description:

...

Solution:

+RewriteEngine on
+RewriteCond   /mirror/of/remotesite/$1           -U
+RewriteRule   ^http://www\.remotesite\.com/(.*)$ /mirror/of/remotesite/$1
+

+ +

+ + Retrieve Missing Data from Intranet + +

Description:

This is a tricky way of virtually running a corporate + (external) Internet web server + (www.quux-corp.dom), while actually keeping + and maintaining its data on an (internal) Intranet web server + (www2.quux-corp.dom) which is protected by a + firewall. The trick is that the external web server retrieves + the requested data on-the-fly from the internal + one.

Solution:

First, we must make sure that our firewall still + protects the internal web server and only the + external web server is allowed to retrieve data from it. + On a packet-filtering firewall, for instance, we could + configure a firewall ruleset like the following:

+ +

+ALLOW Host www.quux-corp.dom Port >1024 --> Host www2.quux-corp.dom Port 80
+DENY  Host *                 Port *     --> Host www2.quux-corp.dom Port 80
+

+ +

Just adjust it to your actual configuration syntax. + Now we can establish the mod_rewrite + rules which request the missing data in the background + through the proxy throughput feature:

+ +

+RewriteRule ^/~([^/]+)/?(.*)          /home/$1/.www/$2 [C]
+# REQUEST_FILENAME usage below is correct in this per-server context example 
+# because the rule that references REQUEST_FILENAME is chained to a rule that
+# sets REQUEST_FILENAME. 
+RewriteCond %{REQUEST_FILENAME}       !-f
+RewriteCond %{REQUEST_FILENAME}       !-d
+RewriteRule ^/home/([^/]+)/.www/?(.*) http://www2.quux-corp.dom/~$1/pub/$2 [P]
+

+ +

+ + Load Balancing + +

Description:

Suppose we want to load balance the traffic to + www.example.com over www[0-5].example.com + (a total of 6 servers). How can this be done?

Solution:

There are many possible solutions for this problem. + We will first discuss a common DNS-based method, + and then one based on mod_rewrite:

+ +

+ DNS Round-Robin + +
The simplest method for load-balancing is to use + DNS round-robin. + Here you just configure www[0-9].example.com + as usual in your DNS with A (address) records, e.g.,
+ +
```
+www0   IN  A       1.2.3.1
+www1   IN  A       1.2.3.2
+www2   IN  A       1.2.3.3
+www3   IN  A       1.2.3.4
+www4   IN  A       1.2.3.5
+www5   IN  A       1.2.3.6
+
```
+ +
Then you additionally add the following entries:
+ +
```
+www   IN  A       1.2.3.1
+www   IN  A       1.2.3.2
+www   IN  A       1.2.3.3
+www   IN  A       1.2.3.4
+www   IN  A       1.2.3.5
+
```
+ +
Now when www.example.com gets + resolved, BIND gives out www0-www5 + - but in a permutated (rotated) order every time. + This way the clients are spread over the various + servers. But notice that this is not a perfect load + balancing scheme, because DNS resolutions are + cached by clients and other nameservers, so + once a client has resolved www.example.com + to a particular wwwN.example.com, all its + subsequent requests will continue to go to the same + IP (and thus a single server), rather than being + distributed across the other available servers. But the + overall result is + okay because the requests are collectively + spread over the various web servers.
+
+ DNS Load-Balancing + +
A sophisticated DNS-based method for + load-balancing is to use the program + lbnamed which can be found at + http://www.stanford.edu/~riepel/lbnamed/. + It is a Perl 5 program which, in conjunction with auxiliary + tools, provides real load-balancing via + DNS.
+
+ Proxy Throughput Round-Robin + +
In this variant we use mod_rewrite + and its proxy throughput feature. First we dedicate + www0.example.com to be actually + www.example.com by using a single
+ +
```
+www    IN  CNAME   www0.example.com.
+
```
+ +
entry in the DNS. Then we convert + www0.example.com to a proxy-only server, + i.e., we configure this machine so all arriving URLs + are simply passed through its internal proxy to one of + the 5 other servers (www1-www5). To + accomplish this we first establish a ruleset which + contacts a load balancing script lb.pl + for all URLs.
+ +
```
+RewriteEngine on
+RewriteMap    lb      prg:/path/to/lb.pl
+RewriteRule   ^/(.+)$ ${lb:$1}           [P,L]
+
```
+ +
Then we write lb.pl:
+ +
```
+#!/path/to/perl
+##
+##  lb.pl -- load balancing script
+##
+
+$| = 1;
+
+$name   = "www";     # the hostname base
+$first  = 1;         # the first server (not 0 here, because 0 is myself)
+$last   = 5;         # the last server in the round-robin
+$domain = "foo.dom"; # the domainname
+
+$cnt = 0;
+while (<STDIN>) {
+    $cnt = (($cnt+1) % ($last+1-$first));
+    $server = sprintf("%s%d.%s", $name, $cnt+$first, $domain);
+    print "http://$server/$_";
+}
+
+##EOF##
+
```
+ + A last notice: Why is this useful? Seems like + www0.example.com still is overloaded? The + answer is yes, it is overloaded, but with plain proxy + throughput requests, only! All SSI, CGI, ePerl, etc. + processing is handled done on the other machines. + For a complicated site, this may work well. The biggest + risk here is that www0 is now a single point of failure -- + if it crashes, the other servers are inaccessible. +
+ Dedicated Load Balancers + +
There are more sophisticated solutions, as well. Cisco, + F5, and several other companies sell hardware load + balancers (typically used in pairs for redundancy), which + offer sophisticated load balancing and auto-failover + features. There are software packages which offer similar + features on commodity hardware, as well. If you have + enough money or need, check these out. The lb-l mailing list is a + good place to research.
+

+ +

+ + New MIME-type, New Service + +

Description:

On the net there are many nifty CGI programs. But + their usage is usually boring, so a lot of webmasters + don't use them. Even Apache's Action handler feature for + MIME-types is only appropriate when the CGI programs + don't need special URLs (actually PATH_INFO + and QUERY_STRINGS) as their input. First, + let us configure a new file type with extension + .scgi (for secure CGI) which will be processed + by the popular cgiwrap program. The problem + here is that for instance if we use a Homogeneous URL Layout + (see above) a file inside the user homedirs might have a URL + like /u/user/foo/bar.scgi, but + cgiwrap needs URLs in the form + /~user/foo/bar.scgi/. The following rule + solves the problem:

+ +

+RewriteRule ^/[uge]/([^/]+)/\.www/(.+)\.scgi(.*) ...
+... /internal/cgi/user/cgiwrap/~$1/$2.scgi$3  [NS,T=application/x-http-cgi]
+

+ +

Or assume we have some more nifty programs: + wwwlog (which displays the + access.log for a URL subtree) and + wwwidx (which runs Glimpse on a URL + subtree). We have to provide the URL area to these + programs so they know which area they are really working with. + But usually this is complicated, because they may still be + requested by the alternate URL form, i.e., typically we would + run the swwidx program from within + /u/user/foo/ via hyperlink to

+ +

+/internal/cgi/user/swwidx?i=/u/user/foo/
+

+ +

which is ugly, because we have to hard-code + both the location of the area + and the location of the CGI inside the + hyperlink. When we have to reorganize, we spend a + lot of time changing the various hyperlinks.

Solution:

The solution here is to provide a special new URL format + which automatically leads to the proper CGI invocation. + We configure the following:

+ +

+RewriteRule   ^/([uge])/([^/]+)(/?.*)/\*  /internal/cgi/user/wwwidx?i=/$1/$2$3/
+RewriteRule   ^/([uge])/([^/]+)(/?.*):log /internal/cgi/user/wwwlog?f=/$1/$2$3
+

+ +

Now the hyperlink to search at + /u/user/foo/ reads only

+ +

+HREF="*"
+

+ +

which internally gets automatically transformed to

+ +

+/internal/cgi/user/wwwidx?i=/u/user/foo/
+

+ +

The same approach leads to an invocation for the + access log CGI program when the hyperlink + :log gets used.

+ +

+ + On-the-fly Content-Regeneration + +

Description:

Here comes a really esoteric feature: Dynamically + generated but statically served pages, i.e., pages should be + delivered as pure static pages (read from the filesystem + and just passed through), but they have to be generated + dynamically by the web server if missing. This way you can + have CGI-generated pages which are statically served unless an + admin (or a cron job) removes the static contents. Then the + contents gets refreshed.

Solution:

+ This is done via the following ruleset: + +

+# This example is valid in per-directory context only
+RewriteCond %{REQUEST_FILENAME}   !-s
+RewriteRule ^page\.html$          page.cgi   [T=application/x-httpd-cgi,L]
+

+ +

Here a request for page.html leads to an + internal run of a corresponding page.cgi if + page.html is missing or has filesize + null. The trick here is that page.cgi is a + CGI script which (additionally to its STDOUT) + writes its output to the file page.html. + Once it has completed, the server sends out + page.html. When the webmaster wants to force + a refresh of the contents, he just removes + page.html (typically from cron).

+ +

+ + Document With Autorefresh + +

Description:

Wouldn't it be nice, while creating a complex web page, if + the web browser would automatically refresh the page every + time we save a new version from within our editor? + Impossible?

Solution:

No! We just combine the MIME multipart feature, the + web server NPH feature, and the URL manipulation power of + mod_rewrite. First, we establish a new + URL feature: Adding just :refresh to any + URL causes the 'page' to be refreshed every time it is + updated on the filesystem.

+ +

+RewriteRule   ^(/[uge]/[^/]+/?.*):refresh  /internal/cgi/apache/nph-refresh?f=$1
+

+ +

Now when we reference the URL

+ +

+/u/foo/bar/page.html:refresh
+

+ +

this leads to the internal invocation of the URL

+ +

+/internal/cgi/apache/nph-refresh?f=/u/foo/bar/page.html
+

+ +

The only missing part is the NPH-CGI script. Although + one would usually say "left as an exercise to the reader" + ;-) I will provide this, too.

+ +

+#!/sw/bin/perl
+##
+##  nph-refresh -- NPH/CGI script for auto refreshing pages
+##  Copyright (c) 1997 Ralf S. Engelschall, All Rights Reserved.
+##
+$| = 1;
+
+#   split the QUERY_STRING variable
+@pairs = split(/&/, $ENV{'QUERY_STRING'});
+foreach $pair (@pairs) {
+    ($name, $value) = split(/=/, $pair);
+    $name =~ tr/A-Z/a-z/;
+    $name = 'QS_' . $name;
+    $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
+    eval "\$$name = \"$value\"";
+}
+$QS_s = 1 if ($QS_s eq '');
+$QS_n = 3600 if ($QS_n eq '');
+if ($QS_f eq '') {
+    print "HTTP/1.0 200 OK\n";
+    print "Content-type: text/html\n\n";
+    print "&lt;b&gt;ERROR&lt;/b&gt;: No file given\n";
+    exit(0);
+}
+if (! -f $QS_f) {
+    print "HTTP/1.0 200 OK\n";
+    print "Content-type: text/html\n\n";
+    print "&lt;b&gt;ERROR&lt;/b&gt;: File $QS_f not found\n";
+    exit(0);
+}
+
+sub print_http_headers_multipart_begin {
+    print "HTTP/1.0 200 OK\n";
+    $bound = "ThisRandomString12345";
+    print "Content-type: multipart/x-mixed-replace;boundary=$bound\n";
+    &print_http_headers_multipart_next;
+}
+
+sub print_http_headers_multipart_next {
+    print "\n--$bound\n";
+}
+
+sub print_http_headers_multipart_end {
+    print "\n--$bound--\n";
+}
+
+sub displayhtml {
+    local($buffer) = @_;
+    $len = length($buffer);
+    print "Content-type: text/html\n";
+    print "Content-length: $len\n\n";
+    print $buffer;
+}
+
+sub readfile {
+    local($file) = @_;
+    local(*FP, $size, $buffer, $bytes);
+    ($x, $x, $x, $x, $x, $x, $x, $size) = stat($file);
+    $size = sprintf("%d", $size);
+    open(FP, "&lt;$file");
+    $bytes = sysread(FP, $buffer, $size);
+    close(FP);
+    return $buffer;
+}
+
+$buffer = &readfile($QS_f);
+&print_http_headers_multipart_begin;
+&displayhtml($buffer);
+
+sub mystat {
+    local($file) = $_[0];
+    local($time);
+
+    ($x, $x, $x, $x, $x, $x, $x, $x, $x, $mtime) = stat($file);
+    return $mtime;
+}
+
+$mtimeL = &mystat($QS_f);
+$mtime = $mtime;
+for ($n = 0; $n &lt; $QS_n; $n++) {
+    while (1) {
+        $mtime = &mystat($QS_f);
+        if ($mtime ne $mtimeL) {
+            $mtimeL = $mtime;
+            sleep(2);
+            $buffer = &readfile($QS_f);
+            &print_http_headers_multipart_next;
+            &displayhtml($buffer);
+            sleep(5);
+            $mtimeL = &mystat($QS_f);
+            last;
+        }
+        sleep($QS_s);
+    }
+}
+
+&print_http_headers_multipart_end;
+
+exit(0);
+
+##EOF##
+

+ +

+ + Mass Virtual Hosting + +

Description:

The VirtualHost feature of Apache is nice + and works great when you just have a few dozen + virtual hosts. But when you are an ISP and have hundreds of + virtual hosts, this feature is suboptimal.

Solution:

To provide this feature we map the remote web page or even + the complete remote web area to our namespace using the + Proxy Throughput feature (flag [P]):

+ +

+##
+##  vhost.map
+##
+www.vhost1.dom:80  /path/to/docroot/vhost1
+www.vhost2.dom:80  /path/to/docroot/vhost2
+     :
+www.vhostN.dom:80  /path/to/docroot/vhostN
+

+ +

+##
+##  httpd.conf
+##
+    :
+#   use the canonical hostname on redirects, etc.
+UseCanonicalName on
+
+    :
+#   add the virtual host in front of the CLF-format
+CustomLog  /path/to/access_log  "%{VHOST}e %h %l %u %t \"%r\" %>s %b"
+    :
+
+#   enable the rewriting engine in the main server
+RewriteEngine on
+
+#   define two maps: one for fixing the URL and one which defines
+#   the available virtual hosts with their corresponding
+#   DocumentRoot.
+RewriteMap    lowercase    int:tolower
+RewriteMap    vhost        txt:/path/to/vhost.map
+
+#   Now do the actual virtual host mapping
+#   via a huge and complicated single rule:
+#
+#   1. make sure we don't map for common locations
+RewriteCond   %{REQUEST_URI}  !^/commonurl1/.*
+RewriteCond   %{REQUEST_URI}  !^/commonurl2/.*
+    :
+RewriteCond   %{REQUEST_URI}  !^/commonurlN/.*
+#
+#   2. make sure we have a Host header, because
+#      currently our approach only supports
+#      virtual hosting through this header
+RewriteCond   %{HTTP_HOST}  !^$
+#
+#   3. lowercase the hostname
+RewriteCond   ${lowercase:%{HTTP_HOST}|NONE}  ^(.+)$
+#
+#   4. lookup this hostname in vhost.map and
+#      remember it only when it is a path
+#      (and not "NONE" from above)
+RewriteCond   ${vhost:%1}  ^(/.*)$
+#
+#   5. finally we can map the URL to its docroot location
+#      and remember the virtual host for logging purposes
+RewriteRule   ^/(.*)$   %1/$1  [E=VHOST:${lowercase:%{HTTP_HOST}}]
+    :
+

+ +

+ + Host Deny + +

Description:

How can we forbid a list of externally configured hosts + from using our server?

Solution:

For Apache >= 1.3b6:

+ +

+RewriteEngine on
+RewriteMap    hosts-deny  txt:/path/to/hosts.deny
+RewriteCond   ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND} !=NOT-FOUND [OR]
+RewriteCond   ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND} !=NOT-FOUND
+RewriteRule   ^/.*  -  [F]
+

+ +

For Apache <= 1.3b6:

+ +

+RewriteEngine on
+RewriteMap    hosts-deny  txt:/path/to/hosts.deny
+RewriteRule   ^/(.*)$ ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND}/$1
+RewriteRule   !^NOT-FOUND/.* - [F]
+RewriteRule   ^NOT-FOUND/(.*)$ ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND}/$1
+RewriteRule   !^NOT-FOUND/.* - [F]
+RewriteRule   ^NOT-FOUND/(.*)$ /$1
+

+ +

+##
+##  hosts.deny
+##
+##  ATTENTION! This is a map, not a list, even when we treat it as such.
+##             mod_rewrite parses it for key/value pairs, so at least a
+##             dummy value "-" must be present for each entry.
+##
+
+193.102.180.41 -
+bsdti1.sdm.de  -
+192.76.162.40  -
+

+ +

+ + Proxy Deny + +

Description:

How can we forbid a certain host or even a user of a + special host from using the Apache proxy?

Solution:

We first have to make sure mod_rewrite + is below(!) mod_proxy in the Configuration + file when compiling the Apache web server. This way it gets + called before mod_proxy. Then we + configure the following for a host-dependent deny...

+ +

+RewriteCond %{REMOTE_HOST} ^badhost\.mydomain\.com$
+RewriteRule !^http://[^/.]\.mydomain.com.*  - [F]
+

+ +

...and this one for a user@host-dependent deny:

+ +

+RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST}  ^badguy@badhost\.mydomain\.com$
+RewriteRule !^http://[^/.]\.mydomain.com.*  - [F]
+

+ +

+ + Special Authentication Variant + +

Description:

Sometimes very special authentication is needed, for + instance authentication which checks for a set of + explicitly configured users. Only these should receive + access and without explicit prompting (which would occur + when using Basic Auth via mod_auth_basic).

Solution:

We use a list of rewrite conditions to exclude all except + our friends:

+ +

+RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} !^friend1@client1.quux-corp\.com$
+RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} !^friend2@client2.quux-corp\.com$
+RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} !^friend3@client3.quux-corp\.com$
+RewriteRule ^/~quux/only-for-friends/      -                                 [F]
+

+ +

+ + Referer-based Deflector + +

Description:

How can we program a flexible URL Deflector which acts + on the "Referer" HTTP header and can be configured with as + many referring pages as we like?

Solution:

Use the following really tricky ruleset...

+ +

+RewriteMap  deflector txt:/path/to/deflector.map
+
+RewriteCond %{HTTP_REFERER} !=""
+RewriteCond ${deflector:%{HTTP_REFERER}} ^-$
+RewriteRule ^.* %{HTTP_REFERER} [R,L]
+
+RewriteCond %{HTTP_REFERER} !=""
+RewriteCond ${deflector:%{HTTP_REFERER}|NOT-FOUND} !=NOT-FOUND
+RewriteRule ^.* ${deflector:%{HTTP_REFERER}} [R,L]
+

+ +

... in conjunction with a corresponding rewrite + map:

+ +

+##
+##  deflector.map
+##
+
+http://www.badguys.com/bad/index.html    -
+http://www.badguys.com/bad/index2.html   -
+http://www.badguys.com/bad/index3.html   http://somewhere.com/
+

+ +

This automatically redirects the request back to the + referring page (when "-" is used as the value + in the map) or to a specific URL (when an URL is specified + in the map as the second argument).

+ +

+ + diff --git a/docs/manual/rewrite/rewrite_guide_advanced.html.en b/docs/manual/rewrite/rewrite_guide_advanced.html.en index 71cf5da423..76a102eb22 100644 --- a/docs/manual/rewrite/rewrite_guide_advanced.html.en +++ b/docs/manual/rewrite/rewrite_guide_advanced.html.en @@ -41,1251 +41,11 @@ avoids many problems.

Web Cluster with Consistent URL Space
Structured Homedirs
Filesystem Reorganization
Redirect Failing URLs to Another Web Server
Archive Access Multiplexer
Browser Dependent Content
Dynamic Mirror
Reverse Dynamic Mirror
Retrieve Missing Data from Intranet
Load Balancing
New MIME-type, New Service
On-the-fly Content-Regeneration
Document With Autorefresh
Mass Virtual Hosting
Host Deny
Proxy Deny
Special Authentication Variant
Referer-based Deflector

Module +
See also
-
-
-
Web Cluster with Consistent URL Space
- - - -
-
Description:
- -
-
We want to create a homogeneous and consistent URL - layout across all WWW servers on an Intranet web cluster, i.e., - all URLs (by definition server-local and thus - server-dependent!) become server independent! - What we want is to give the WWW namespace a single consistent - layout: no URL should refer to - any particular target server. The cluster itself - should connect users automatically to a physical target - host as needed, invisibly.
-
- -
Solution:
- -
-
First, the knowledge of the target servers comes from - (distributed) external maps which contain information on - where our users, groups, and entities reside. They have the - form:
- -
-user1 server_of_user1 -user2 server_of_user2 -: : -
- -
We put them into files map.xxx-to-host. - Second we need to instruct all servers to redirect URLs - of the forms:
- -
-/u/user/anypath -/g/group/anypath -/e/entity/anypath -
- -
to
- -
-http://physical-host/u/user/anypath -http://physical-host/g/group/anypath -http://physical-host/e/entity/anypath -
- -
when any URL path need not be valid on every server. The - following ruleset does this for us with the help of the map - files (assuming that server0 is a default server which - will be used if a user has no entry in the map):
- -
-RewriteEngine on - -RewriteMap user-to-host txt:/path/to/map.user-to-host -RewriteMap group-to-host txt:/path/to/map.group-to-host -RewriteMap entity-to-host txt:/path/to/map.entity-to-host - -RewriteRule ^/u/([^/]+)/?(.*) http://${user-to-host:$1|server0}/u/$1/$2 -RewriteRule ^/g/([^/]+)/?(.*) http://${group-to-host:$1|server0}/g/$1/$2 -RewriteRule ^/e/([^/]+)/?(.*) http://${entity-to-host:$1|server0}/e/$1/$2 - -RewriteRule ^/([uge])/([^/]+)/?$ /$1/$2/.www/ -RewriteRule ^/([uge])/([^/]+)/([^.]+.+) /$1/$2/.www/$3\ -
-
-
- -
-
-
Structured Homedirs
- - - -
-
Description:
- -
-
Some sites with thousands of users use a - structured homedir layout, i.e. each homedir is in a - subdirectory which begins (for instance) with the first - character of the username. So, /~foo/anypath - is /home/f/foo/.www/anypath - while /~bar/anypath is - /home/b/bar/.www/anypath.
-
- -
Solution:
- -
-
We use the following ruleset to expand the tilde URLs - into the above layout.
- -
-RewriteEngine on -RewriteRule ^/~(([a-z])[a-z0-9]+)(.*) /home/$2/$1/.www$3 -
-
-
- -
-
-
Filesystem Reorganization
- - - -
-
Description:
- -
-
This really is a hardcore example: a killer application - which heavily uses per-directory - RewriteRules to get a smooth look and feel - on the Web while its data structure is never touched or - adjusted. Background: net.sw is - my archive of freely available Unix software packages, - which I started to collect in 1992. It is both my hobby - and job to do this, because while I'm studying computer - science I have also worked for many years as a system and - network administrator in my spare time. Every week I need - some sort of software so I created a deep hierarchy of - directories where I stored the packages:
- -
-drwxrwxr-x 2 netsw users 512 Aug 3 18:39 Audio/ -drwxrwxr-x 2 netsw users 512 Jul 9 14:37 Benchmark/ -drwxrwxr-x 12 netsw users 512 Jul 9 00:34 Crypto/ -drwxrwxr-x 5 netsw users 512 Jul 9 00:41 Database/ -drwxrwxr-x 4 netsw users 512 Jul 30 19:25 Dicts/ -drwxrwxr-x 10 netsw users 512 Jul 9 01:54 Graphic/ -drwxrwxr-x 5 netsw users 512 Jul 9 01:58 Hackers/ -drwxrwxr-x 8 netsw users 512 Jul 9 03:19 InfoSys/ -drwxrwxr-x 3 netsw users 512 Jul 9 03:21 Math/ -drwxrwxr-x 3 netsw users 512 Jul 9 03:24 Misc/ -drwxrwxr-x 9 netsw users 512 Aug 1 16:33 Network/ -drwxrwxr-x 2 netsw users 512 Jul 9 05:53 Office/ -drwxrwxr-x 7 netsw users 512 Jul 9 09:24 SoftEng/ -drwxrwxr-x 7 netsw users 512 Jul 9 12:17 System/ -drwxrwxr-x 12 netsw users 512 Aug 3 20:15 Typesetting/ -drwxrwxr-x 10 netsw users 512 Jul 9 14:08 X11/ -
- -
In July 1996 I decided to make this archive public to - the world via a nice Web interface. "Nice" means that I - wanted to offer an interface where you can browse - directly through the archive hierarchy. And "nice" means - that I didn't want to change anything inside this - hierarchy - not even by putting some CGI scripts at the - top of it. Why? Because the above structure should later be - accessible via FTP as well, and I didn't want any - Web or CGI stuff mixed in there.
-
- -
Solution:
- -
-
The solution has two parts: The first is a set of CGI - scripts which create all the pages at all directory - levels on-the-fly. I put them under - /e/netsw/.www/ as follows:
- -
--rw-r--r-- 1 netsw users 1318 Aug 1 18:10 .wwwacl -drwxr-xr-x 18 netsw users 512 Aug 5 15:51 DATA/ --rw-rw-rw- 1 netsw users 372982 Aug 5 16:35 LOGFILE --rw-r--r-- 1 netsw users 659 Aug 4 09:27 TODO --rw-r--r-- 1 netsw users 5697 Aug 1 18:01 netsw-about.html --rwxr-xr-x 1 netsw users 579 Aug 2 10:33 netsw-access.pl --rwxr-xr-x 1 netsw users 1532 Aug 1 17:35 netsw-changes.cgi --rwxr-xr-x 1 netsw users 2866 Aug 5 14:49 netsw-home.cgi -drwxr-xr-x 2 netsw users 512 Jul 8 23:47 netsw-img/ --rwxr-xr-x 1 netsw users 24050 Aug 5 15:49 netsw-lsdir.cgi --rwxr-xr-x 1 netsw users 1589 Aug 3 18:43 netsw-search.cgi --rwxr-xr-x 1 netsw users 1885 Aug 1 17:41 netsw-tree.cgi --rw-r--r-- 1 netsw users 234 Jul 30 16:35 netsw-unlimit.lst -
- -
The DATA/ subdirectory holds the above - directory structure, i.e. the real - net.sw stuff, and gets - automatically updated via rdist from time to - time. The second part of the problem remains: how to link - these two structures together into one smooth-looking URL - tree? We want to hide the DATA/ directory - from the user while running the appropriate CGI scripts - for the various URLs. Here is the solution: first I put - the following into the per-directory configuration file - in the DocumentRoot - of the server to rewrite the public URL path - /net.sw/ to the internal path - /e/netsw:
- -
-RewriteRule ^net.sw$ net.sw/ [R] -RewriteRule ^net.sw/(.*)$ e/netsw/$1 -
- -
The first rule is for requests which miss the trailing - slash! The second rule does the real thing. And then - comes the killer configuration which stays in the - per-directory config file - /e/netsw/.www/.wwwacl:
- -
-Options ExecCGI FollowSymLinks Includes MultiViews - -RewriteEngine on - -# we are reached via /net.sw/ prefix -RewriteBase /net.sw/ - -# first we rewrite the root dir to -# the handling cgi script -RewriteRule ^$ netsw-home.cgi [L] -RewriteRule ^index\.html$ netsw-home.cgi [L] - -# strip out the subdirs when -# the browser requests us from perdir pages -RewriteRule ^.+/(netsw-[^/]+/.+)$ $1 [L] - -# and now break the rewriting for local files -RewriteRule ^netsw-home\.cgi.* - [L] -RewriteRule ^netsw-changes\.cgi.* - [L] -RewriteRule ^netsw-search\.cgi.* - [L] -RewriteRule ^netsw-tree\.cgi$ - [L] -RewriteRule ^netsw-about\.html$ - [L] -RewriteRule ^netsw-img/.*$ - [L] - -# anything else is a subdir which gets handled -# by another cgi script -RewriteRule !^netsw-lsdir\.cgi.* - [C] -RewriteRule (.*) netsw-lsdir.cgi/$1 -
- -
Some hints for interpretation:
- -
1. Notice the L (last) flag and no - substitution field ('-') in the fourth part
2. Notice the ! (not) character and - the C (chain) flag at the first rule - in the last part
3. Notice the catch-all pattern in the last rule
-
-
- -
-
-
Redirect Failing URLs to Another Web Server
- - - -
-
Description:
- -
-
A typical FAQ about URL rewriting is how to redirect - failing requests on webserver A to webserver B. Usually - this is done via ErrorDocument CGI scripts in Perl, but - there is also a mod_rewrite solution. - But note that this performs more poorly than using an - ErrorDocument - CGI script!
-
- -
Solution:
- -
-
The first solution has the best performance but less - flexibility, and is less safe:
- -
-RewriteEngine on -RewriteCond %{DOCUMENT_ROOT/%{REQUEST_URI} !-f -RewriteRule ^(.+) http://webserverB.dom/$1 -
- -
The problem here is that this will only work for pages - inside the DocumentRoot. While you can add more - Conditions (for instance to also handle homedirs, etc.) - there is a better variant:
- -
-RewriteEngine on -RewriteCond %{REQUEST_URI} !-U -RewriteRule ^(.+) http://webserverB.dom/$1 -
- -
This uses the URL look-ahead feature of mod_rewrite. - The result is that this will work for all types of URLs - and is safe. But it does have a performance impact on - the web server, because for every request there is one - more internal subrequest. So, if your web server runs on a - powerful CPU, use this one. If it is a slow machine, use - the first approach or better an ErrorDocument CGI script.
-
-
- -
-
-
Archive Access Multiplexer
- - - -
-
Description:
- -
-
Do you know the great CPAN (Comprehensive Perl Archive - Network) under http://www.perl.com/CPAN? - CPAN automatically redirects browsers to one of many FTP - servers around the world (generally one near the requesting - client); each server carries a full CPAN mirror. This is - effectively an FTP access multiplexing service. - CPAN runs via CGI scripts, but how could a similar approach - be implemented via mod_rewrite?
-
- -
Solution:
- -
-
First we notice that as of version 3.0.0, - mod_rewrite can - also use the "ftp:" scheme on redirects. - And second, the location approximation can be done by a - RewriteMap - over the top-level domain of the client. - With a tricky chained ruleset we can use this top-level - domain as a key to our multiplexing map.
- -
-RewriteEngine on -RewriteMap multiplex txt:/path/to/map.cxan -RewriteRule ^/CxAN/(.*) %{REMOTE_HOST}::$1 [C] -RewriteRule ^.+\.([a-zA-Z]+)::(.*)$ ${multiplex:$1|ftp.default.dom}$2 [R,L] -
- -
-## -## map.cxan -- Multiplexing Map for CxAN -## - -de ftp://ftp.cxan.de/CxAN/ -uk ftp://ftp.cxan.uk/CxAN/ -com ftp://ftp.cxan.com/CxAN/ - : -##EOF## -
-
-
- -
-
-
Browser Dependent Content
- - - -
-
Description:
- -
-
At least for important top-level pages it is sometimes - necessary to provide the optimum of browser dependent - content, i.e., one has to provide one version for - current browsers, a different version for the Lynx and text-mode - browsers, and another for other browsers.
-
- -
Solution:
- -
-
We cannot use content negotiation because the browsers do - not provide their type in that form. Instead we have to - act on the HTTP header "User-Agent". The following config - does the following: If the HTTP header "User-Agent" - begins with "Mozilla/3", the page foo.html - is rewritten to foo.NS.html and the - rewriting stops. If the browser is "Lynx" or "Mozilla" of - version 1 or 2, the URL becomes foo.20.html. - All other browsers receive page foo.32.html. - This is done with the following ruleset:
- -
-RewriteCond %{HTTP_USER_AGENT} ^Mozilla/3.* -RewriteRule ^foo\.html$ foo.NS.html [L] - -RewriteCond %{HTTP_USER_AGENT} ^Lynx/.* [OR] -RewriteCond %{HTTP_USER_AGENT} ^Mozilla/[12].* -RewriteRule ^foo\.html$ foo.20.html [L] - -RewriteRule ^foo\.html$ foo.32.html [L] -
-
-
- -
-
-
Dynamic Mirror
- - - -
-
Description:
- -
-
Assume there are nice web pages on remote hosts we want - to bring into our namespace. For FTP servers we would use - the mirror program which actually maintains an - explicit up-to-date copy of the remote data on the local - machine. For a web server we could use the program - webcopy which runs via HTTP. But both - techniques have a major drawback: The local copy is - always only as up-to-date as the last time we ran the program. It - would be much better if the mirror was not a static one we - have to establish explicitly. Instead we want a dynamic - mirror with data which gets updated automatically - as needed on the remote host(s).
-
- -
Solution:
- -
-
To provide this feature we map the remote web page or even - the complete remote web area to our namespace by the use - of the Proxy Throughput feature - (flag [P]):
- -
-RewriteEngine on -RewriteBase /~quux/ -RewriteRule ^hotsheet/(.*)$ http://www.tstimpreso.com/hotsheet/$1 [P] -
- -
-RewriteEngine on -RewriteBase /~quux/ -RewriteRule ^usa-news\.html$ http://www.quux-corp.com/news/index.html [P] -
-
-
- -
-
-
Reverse Dynamic Mirror
- - - -
-
Description:
- -
...
- -
Solution:
- -
-
-RewriteEngine on -RewriteCond /mirror/of/remotesite/$1 -U -RewriteRule ^http://www\.remotesite\.com/(.*)$ /mirror/of/remotesite/$1 -
-
-
- -
-
-
Retrieve Missing Data from Intranet
- - - -
-
Description:
- -
-
This is a tricky way of virtually running a corporate - (external) Internet web server - (www.quux-corp.dom), while actually keeping - and maintaining its data on an (internal) Intranet web server - (www2.quux-corp.dom) which is protected by a - firewall. The trick is that the external web server retrieves - the requested data on-the-fly from the internal - one.
-
- -
Solution:
- -
-
First, we must make sure that our firewall still - protects the internal web server and only the - external web server is allowed to retrieve data from it. - On a packet-filtering firewall, for instance, we could - configure a firewall ruleset like the following:
- -
-ALLOW Host www.quux-corp.dom Port >1024 --> Host www2.quux-corp.dom Port 80 -DENY Host * Port * --> Host www2.quux-corp.dom Port 80 -
- -
Just adjust it to your actual configuration syntax. - Now we can establish the mod_rewrite - rules which request the missing data in the background - through the proxy throughput feature:
- -
-RewriteRule ^/~([^/]+)/?(.*) /home/$1/.www/$2 [C] -# REQUEST_FILENAME usage below is correct in this per-server context example -# because the rule that references REQUEST_FILENAME is chained to a rule that -# sets REQUEST_FILENAME. -RewriteCond %{REQUEST_FILENAME} !-f -RewriteCond %{REQUEST_FILENAME} !-d -RewriteRule ^/home/([^/]+)/.www/?(.*) http://www2.quux-corp.dom/~$1/pub/$2 [P] -
-
-
- -
-
-
Load Balancing
- - - -
-
Description:
- -
-
Suppose we want to load balance the traffic to - www.example.com over www[0-5].example.com - (a total of 6 servers). How can this be done?
-
- -
Solution:
- -
-
There are many possible solutions for this problem. - We will first discuss a common DNS-based method, - and then one based on mod_rewrite:
- -
1. - DNS Round-Robin - -
  The simplest method for load-balancing is to use - DNS round-robin. - Here you just configure www[0-9].example.com - as usual in your DNS with A (address) records, e.g.,
  - -
  -www0 IN A 1.2.3.1 -www1 IN A 1.2.3.2 -www2 IN A 1.2.3.3 -www3 IN A 1.2.3.4 -www4 IN A 1.2.3.5 -www5 IN A 1.2.3.6 -
  - -
  Then you additionally add the following entries:
  - -
  -www IN A 1.2.3.1 -www IN A 1.2.3.2 -www IN A 1.2.3.3 -www IN A 1.2.3.4 -www IN A 1.2.3.5 -
  - -
  Now when www.example.com gets - resolved, BIND gives out www0-www5 - - but in a permutated (rotated) order every time. - This way the clients are spread over the various - servers. But notice that this is not a perfect load - balancing scheme, because DNS resolutions are - cached by clients and other nameservers, so - once a client has resolved www.example.com - to a particular wwwN.example.com, all its - subsequent requests will continue to go to the same - IP (and thus a single server), rather than being - distributed across the other available servers. But the - overall result is - okay because the requests are collectively - spread over the various web servers.
  -
2. - DNS Load-Balancing - -
  A sophisticated DNS-based method for - load-balancing is to use the program - lbnamed which can be found at - http://www.stanford.edu/~riepel/lbnamed/. - It is a Perl 5 program which, in conjunction with auxiliary - tools, provides real load-balancing via - DNS.
  -
3. - Proxy Throughput Round-Robin - -
  In this variant we use mod_rewrite - and its proxy throughput feature. First we dedicate - www0.example.com to be actually - www.example.com by using a single
  - -
  -www IN CNAME www0.example.com. -
  - -
  entry in the DNS. Then we convert - www0.example.com to a proxy-only server, - i.e., we configure this machine so all arriving URLs - are simply passed through its internal proxy to one of - the 5 other servers (www1-www5). To - accomplish this we first establish a ruleset which - contacts a load balancing script lb.pl - for all URLs.
  - -
  -RewriteEngine on -RewriteMap lb prg:/path/to/lb.pl -RewriteRule ^/(.+)$ ${lb:$1} [P,L] -
  - -
  Then we write lb.pl:
  - -
  -#!/path/to/perl -## -## lb.pl -- load balancing script -## - -$| = 1; - -$name = "www"; # the hostname base -$first = 1; # the first server (not 0 here, because 0 is myself) -$last = 5; # the last server in the round-robin -$domain = "foo.dom"; # the domainname - -$cnt = 0; -while (<STDIN>) { - $cnt = (($cnt+1) % ($last+1-$first)); - $server = sprintf("%s%d.%s", $name, $cnt+$first, $domain); - print "http://$server/$_"; -} - -##EOF## -
  - -
  A last notice: Why is this useful? Seems like - www0.example.com still is overloaded? The - answer is yes, it is overloaded, but with plain proxy - throughput requests, only! All SSI, CGI, ePerl, etc. - processing is handled done on the other machines. - For a complicated site, this may work well. The biggest - risk here is that www0 is now a single point of failure -- - if it crashes, the other servers are inaccessible.
  -
4. - Dedicated Load Balancers - -
  There are more sophisticated solutions, as well. Cisco, - F5, and several other companies sell hardware load - balancers (typically used in pairs for redundancy), which - offer sophisticated load balancing and auto-failover - features. There are software packages which offer similar - features on commodity hardware, as well. If you have - enough money or need, check these out. The lb-l mailing list is a - good place to research.
  -
-
-
- -
-
-
New MIME-type, New Service
- - - -
-
Description:
- -
-
On the net there are many nifty CGI programs. But - their usage is usually boring, so a lot of webmasters - don't use them. Even Apache's Action handler feature for - MIME-types is only appropriate when the CGI programs - don't need special URLs (actually PATH_INFO - and QUERY_STRINGS) as their input. First, - let us configure a new file type with extension - .scgi (for secure CGI) which will be processed - by the popular cgiwrap program. The problem - here is that for instance if we use a Homogeneous URL Layout - (see above) a file inside the user homedirs might have a URL - like /u/user/foo/bar.scgi, but - cgiwrap needs URLs in the form - /~user/foo/bar.scgi/. The following rule - solves the problem:
- -
-RewriteRule ^/[uge]/([^/]+)/\.www/(.+)\.scgi(.*) ... -... /internal/cgi/user/cgiwrap/~$1/$2.scgi$3 [NS,T=application/x-http-cgi] -
- -
Or assume we have some more nifty programs: - wwwlog (which displays the - access.log for a URL subtree) and - wwwidx (which runs Glimpse on a URL - subtree). We have to provide the URL area to these - programs so they know which area they are really working with. - But usually this is complicated, because they may still be - requested by the alternate URL form, i.e., typically we would - run the swwidx program from within - /u/user/foo/ via hyperlink to
- -
-/internal/cgi/user/swwidx?i=/u/user/foo/ -
- -
which is ugly, because we have to hard-code - both the location of the area - and the location of the CGI inside the - hyperlink. When we have to reorganize, we spend a - lot of time changing the various hyperlinks.
-
- -
Solution:
- -
-
The solution here is to provide a special new URL format - which automatically leads to the proper CGI invocation. - We configure the following:
- -
-RewriteRule ^/([uge])/([^/]+)(/?.*)/\* /internal/cgi/user/wwwidx?i=/$1/$2$3/ -RewriteRule ^/([uge])/([^/]+)(/?.*):log /internal/cgi/user/wwwlog?f=/$1/$2$3 -
- -
Now the hyperlink to search at - /u/user/foo/ reads only
- -
-HREF="*" -
- -
which internally gets automatically transformed to
- -
-/internal/cgi/user/wwwidx?i=/u/user/foo/ -
- -
The same approach leads to an invocation for the - access log CGI program when the hyperlink - :log gets used.
-
-
- -
-
-
On-the-fly Content-Regeneration
- - - -
-
Description:
- -
-
Here comes a really esoteric feature: Dynamically - generated but statically served pages, i.e., pages should be - delivered as pure static pages (read from the filesystem - and just passed through), but they have to be generated - dynamically by the web server if missing. This way you can - have CGI-generated pages which are statically served unless an - admin (or a cron job) removes the static contents. Then the - contents gets refreshed.
-
- -
Solution:
- -
- This is done via the following ruleset: - -
-# This example is valid in per-directory context only -RewriteCond %{REQUEST_FILENAME} !-s -RewriteRule ^page\.html$ page.cgi [T=application/x-httpd-cgi,L] -
- -
Here a request for page.html leads to an - internal run of a corresponding page.cgi if - page.html is missing or has filesize - null. The trick here is that page.cgi is a - CGI script which (additionally to its STDOUT) - writes its output to the file page.html. - Once it has completed, the server sends out - page.html. When the webmaster wants to force - a refresh of the contents, he just removes - page.html (typically from cron).
-
-
- -
-
-
Document With Autorefresh
- - - -
-
Description:
- -
-
Wouldn't it be nice, while creating a complex web page, if - the web browser would automatically refresh the page every - time we save a new version from within our editor? - Impossible?
-
- -
Solution:
- -
-
No! We just combine the MIME multipart feature, the - web server NPH feature, and the URL manipulation power of - mod_rewrite. First, we establish a new - URL feature: Adding just :refresh to any - URL causes the 'page' to be refreshed every time it is - updated on the filesystem.
- -
-RewriteRule ^(/[uge]/[^/]+/?.*):refresh /internal/cgi/apache/nph-refresh?f=$1 -
- -
Now when we reference the URL
- -
-/u/foo/bar/page.html:refresh -
- -
this leads to the internal invocation of the URL
- -
-/internal/cgi/apache/nph-refresh?f=/u/foo/bar/page.html -
- -
The only missing part is the NPH-CGI script. Although - one would usually say "left as an exercise to the reader" - ;-) I will provide this, too.
- -
-#!/sw/bin/perl -## -## nph-refresh -- NPH/CGI script for auto refreshing pages -## Copyright (c) 1997 Ralf S. Engelschall, All Rights Reserved. -## -$| = 1; - -# split the QUERY_STRING variable -@pairs = split(/&/, $ENV{'QUERY_STRING'}); -foreach $pair (@pairs) { - ($name, $value) = split(/=/, $pair); - $name =~ tr/A-Z/a-z/; - $name = 'QS_' . $name; - $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg; - eval "\$$name = \"$value\""; -} -$QS_s = 1 if ($QS_s eq ''); -$QS_n = 3600 if ($QS_n eq ''); -if ($QS_f eq '') { - print "HTTP/1.0 200 OK\n"; - print "Content-type: text/html\n\n"; - print "<b>ERROR</b>: No file given\n"; - exit(0); -} -if (! -f $QS_f) { - print "HTTP/1.0 200 OK\n"; - print "Content-type: text/html\n\n"; - print "<b>ERROR</b>: File $QS_f not found\n"; - exit(0); -} - -sub print_http_headers_multipart_begin { - print "HTTP/1.0 200 OK\n"; - $bound = "ThisRandomString12345"; - print "Content-type: multipart/x-mixed-replace;boundary=$bound\n"; - &print_http_headers_multipart_next; -} - -sub print_http_headers_multipart_next { - print "\n--$bound\n"; -} - -sub print_http_headers_multipart_end { - print "\n--$bound--\n"; -} - -sub displayhtml { - local($buffer) = @_; - $len = length($buffer); - print "Content-type: text/html\n"; - print "Content-length: $len\n\n"; - print $buffer; -} - -sub readfile { - local($file) = @_; - local(*FP, $size, $buffer, $bytes); - ($x, $x, $x, $x, $x, $x, $x, $size) = stat($file); - $size = sprintf("%d", $size); - open(FP, "<$file"); - $bytes = sysread(FP, $buffer, $size); - close(FP); - return $buffer; -} - -$buffer = &readfile($QS_f); -&print_http_headers_multipart_begin; -&displayhtml($buffer); - -sub mystat { - local($file) = $_[0]; - local($time); - - ($x, $x, $x, $x, $x, $x, $x, $x, $x, $mtime) = stat($file); - return $mtime; -} - -$mtimeL = &mystat($QS_f); -$mtime = $mtime; -for ($n = 0; $n < $QS_n; $n++) { - while (1) { - $mtime = &mystat($QS_f); - if ($mtime ne $mtimeL) { - $mtimeL = $mtime; - sleep(2); - $buffer = &readfile($QS_f); - &print_http_headers_multipart_next; - &displayhtml($buffer); - sleep(5); - $mtimeL = &mystat($QS_f); - last; - } - sleep($QS_s); - } -} - -&print_http_headers_multipart_end; - -exit(0); - -##EOF## -
-
-
- -
-
-
Mass Virtual Hosting
- - - -
-
Description:
- -
-
The <VirtualHost> feature of Apache is nice - and works great when you just have a few dozen - virtual hosts. But when you are an ISP and have hundreds of - virtual hosts, this feature is suboptimal.
-
- -
Solution:
- -
-
To provide this feature we map the remote web page or even - the complete remote web area to our namespace using the - Proxy Throughput feature (flag [P]):
- -
-## -## vhost.map -## -www.vhost1.dom:80 /path/to/docroot/vhost1 -www.vhost2.dom:80 /path/to/docroot/vhost2 - : -www.vhostN.dom:80 /path/to/docroot/vhostN -
- -
-## -## httpd.conf -## - : -# use the canonical hostname on redirects, etc. -UseCanonicalName on - - : -# add the virtual host in front of the CLF-format -CustomLog /path/to/access_log "%{VHOST}e %h %l %u %t \"%r\" %>s %b" - : - -# enable the rewriting engine in the main server -RewriteEngine on - -# define two maps: one for fixing the URL and one which defines -# the available virtual hosts with their corresponding -# DocumentRoot. -RewriteMap lowercase int:tolower -RewriteMap vhost txt:/path/to/vhost.map - -# Now do the actual virtual host mapping -# via a huge and complicated single rule: -# -# 1. make sure we don't map for common locations -RewriteCond %{REQUEST_URI} !^/commonurl1/.* -RewriteCond %{REQUEST_URI} !^/commonurl2/.* - : -RewriteCond %{REQUEST_URI} !^/commonurlN/.* -# -# 2. make sure we have a Host header, because -# currently our approach only supports -# virtual hosting through this header -RewriteCond %{HTTP_HOST} !^$ -# -# 3. lowercase the hostname -RewriteCond ${lowercase:%{HTTP_HOST}|NONE} ^(.+)$ -# -# 4. lookup this hostname in vhost.map and -# remember it only when it is a path -# (and not "NONE" from above) -RewriteCond ${vhost:%1} ^(/.*)$ -# -# 5. finally we can map the URL to its docroot location -# and remember the virtual host for logging purposes -RewriteRule ^/(.*)$ %1/$1 [E=VHOST:${lowercase:%{HTTP_HOST}}] - : -
-
-
- -
-
-
Host Deny
- - - -
-
Description:
- -
-
How can we forbid a list of externally configured hosts - from using our server?
-
- -
Solution:
- -
-
For Apache >= 1.3b6:
- -
-RewriteEngine on -RewriteMap hosts-deny txt:/path/to/hosts.deny -RewriteCond ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND} !=NOT-FOUND [OR] -RewriteCond ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND} !=NOT-FOUND -RewriteRule ^/.* - [F] -
- -
For Apache <= 1.3b6:
- -
-RewriteEngine on -RewriteMap hosts-deny txt:/path/to/hosts.deny -RewriteRule ^/(.*)$ ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND}/$1 -RewriteRule !^NOT-FOUND/.* - [F] -RewriteRule ^NOT-FOUND/(.*)$ ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND}/$1 -RewriteRule !^NOT-FOUND/.* - [F] -RewriteRule ^NOT-FOUND/(.*)$ /$1 -
- -
-## -## hosts.deny -## -## ATTENTION! This is a map, not a list, even when we treat it as such. -## mod_rewrite parses it for key/value pairs, so at least a -## dummy value "-" must be present for each entry. -## - -193.102.180.41 - -bsdti1.sdm.de - -192.76.162.40 - -
-
-
- -
-
-
Proxy Deny
- - - -
-
Description:
- -
-
How can we forbid a certain host or even a user of a - special host from using the Apache proxy?
-
- -
Solution:
- -
-
We first have to make sure mod_rewrite - is below(!) mod_proxy in the Configuration - file when compiling the Apache web server. This way it gets - called before mod_proxy. Then we - configure the following for a host-dependent deny...
- -
-RewriteCond %{REMOTE_HOST} ^badhost\.mydomain\.com$ -RewriteRule !^http://[^/.]\.mydomain.com.* - [F] -
- -
...and this one for a user@host-dependent deny:
- -
-RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} ^badguy@badhost\.mydomain\.com$ -RewriteRule !^http://[^/.]\.mydomain.com.* - [F] -
-
-
- -
-
-
Special Authentication Variant
- - - -
-
Description:
- -
-
Sometimes very special authentication is needed, for - instance authentication which checks for a set of - explicitly configured users. Only these should receive - access and without explicit prompting (which would occur - when using Basic Auth via mod_auth_basic).
-
- -
Solution:
- -
-
We use a list of rewrite conditions to exclude all except - our friends:
- -
-RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} !^friend1@client1.quux-corp\.com$ -RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} !^friend2@client2.quux-corp\.com$ -RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} !^friend3@client3.quux-corp\.com$ -RewriteRule ^/~quux/only-for-friends/ - [F] -
-
-
- -
-
-
Referer-based Deflector
- - - -
-
Description:
- -
-
How can we program a flexible URL Deflector which acts - on the "Referer" HTTP header and can be configured with as - many referring pages as we like?
-
- -
Solution:
- -
-
Use the following really tricky ruleset...
- -
-RewriteMap deflector txt:/path/to/deflector.map - -RewriteCond %{HTTP_REFERER} !="" -RewriteCond ${deflector:%{HTTP_REFERER}} ^-$ -RewriteRule ^.* %{HTTP_REFERER} [R,L] - -RewriteCond %{HTTP_REFERER} !="" -RewriteCond ${deflector:%{HTTP_REFERER}|NOT-FOUND} !=NOT-FOUND -RewriteRule ^.* ${deflector:%{HTTP_REFERER}} [R,L] -
- -
... in conjunction with a corresponding rewrite - map:
- -
-## -## deflector.map -## - -http://www.badguys.com/bad/index.html - -http://www.badguys.com/bad/index2.html - -http://www.badguys.com/bad/index3.html http://somewhere.com/ -
- -
This automatically redirects the request back to the - referring page (when "-" is used as the value - in the map) or to a specific URL (when an URL is specified - in the map as the second argument).
-
-
- -

Available Languages: en | fr

diff --git a/docs/manual/rewrite/rewrite_guide_advanced.xml b/docs/manual/rewrite/rewrite_guide_advanced.xml index 1071479b1c..07aeefd9d4 100644 --- a/docs/manual/rewrite/rewrite_guide_advanced.xml +++ b/docs/manual/rewrite/rewrite_guide_advanced.xml @@ -54,1233 +54,5 @@ examples Technical details -

- - Web Cluster with Consistent URL Space - -

Description:

We want to create a homogeneous and consistent URL - layout across all WWW servers on an Intranet web cluster, i.e., - all URLs (by definition server-local and thus - server-dependent!) become server independent! - What we want is to give the WWW namespace a single consistent - layout: no URL should refer to - any particular target server. The cluster itself - should connect users automatically to a physical target - host as needed, invisibly.

Solution:

First, the knowledge of the target servers comes from - (distributed) external maps which contain information on - where our users, groups, and entities reside. They have the - form:

- -

-user1  server_of_user1
-user2  server_of_user2
-:      :
-

- -

We put them into files map.xxx-to-host. - Second we need to instruct all servers to redirect URLs - of the forms:

- -

-/u/user/anypath
-/g/group/anypath
-/e/entity/anypath
-

- -

-http://physical-host/u/user/anypath
-http://physical-host/g/group/anypath
-http://physical-host/e/entity/anypath
-

- -

when any URL path need not be valid on every server. The - following ruleset does this for us with the help of the map - files (assuming that server0 is a default server which - will be used if a user has no entry in the map):

- -

-RewriteEngine on
-
-RewriteMap      user-to-host   txt:/path/to/map.user-to-host
-RewriteMap     group-to-host   txt:/path/to/map.group-to-host
-RewriteMap    entity-to-host   txt:/path/to/map.entity-to-host
-
-RewriteRule   ^/u/([^/]+)/?(.*)   http://${user-to-host:$1|server0}/u/$1/$2
-RewriteRule   ^/g/([^/]+)/?(.*)  http://${group-to-host:$1|server0}/g/$1/$2
-RewriteRule   ^/e/([^/]+)/?(.*) http://${entity-to-host:$1|server0}/e/$1/$2
-
-RewriteRule   ^/([uge])/([^/]+)/?$          /$1/$2/.www/
-RewriteRule   ^/([uge])/([^/]+)/([^.]+.+)   /$1/$2/.www/$3\
-

- -

- - Structured Homedirs - -

Description:

Some sites with thousands of users use a - structured homedir layout, i.e. each homedir is in a - subdirectory which begins (for instance) with the first - character of the username. So, /~foo/anypath - is /home/f/foo/.www/anypath - while /~bar/anypath is - /home/b/bar/.www/anypath.

Solution:

We use the following ruleset to expand the tilde URLs - into the above layout.

- -

-RewriteEngine on
-RewriteRule   ^/~(([a-z])[a-z0-9]+)(.*)  /home/$2/$1/.www$3
-

- -

- - Filesystem Reorganization - -

Description:

This really is a hardcore example: a killer application - which heavily uses per-directory - RewriteRules to get a smooth look and feel - on the Web while its data structure is never touched or - adjusted. Background: net.sw is - my archive of freely available Unix software packages, - which I started to collect in 1992. It is both my hobby - and job to do this, because while I'm studying computer - science I have also worked for many years as a system and - network administrator in my spare time. Every week I need - some sort of software so I created a deep hierarchy of - directories where I stored the packages:

- -

-drwxrwxr-x   2 netsw  users    512 Aug  3 18:39 Audio/
-drwxrwxr-x   2 netsw  users    512 Jul  9 14:37 Benchmark/
-drwxrwxr-x  12 netsw  users    512 Jul  9 00:34 Crypto/
-drwxrwxr-x   5 netsw  users    512 Jul  9 00:41 Database/
-drwxrwxr-x   4 netsw  users    512 Jul 30 19:25 Dicts/
-drwxrwxr-x  10 netsw  users    512 Jul  9 01:54 Graphic/
-drwxrwxr-x   5 netsw  users    512 Jul  9 01:58 Hackers/
-drwxrwxr-x   8 netsw  users    512 Jul  9 03:19 InfoSys/
-drwxrwxr-x   3 netsw  users    512 Jul  9 03:21 Math/
-drwxrwxr-x   3 netsw  users    512 Jul  9 03:24 Misc/
-drwxrwxr-x   9 netsw  users    512 Aug  1 16:33 Network/
-drwxrwxr-x   2 netsw  users    512 Jul  9 05:53 Office/
-drwxrwxr-x   7 netsw  users    512 Jul  9 09:24 SoftEng/
-drwxrwxr-x   7 netsw  users    512 Jul  9 12:17 System/
-drwxrwxr-x  12 netsw  users    512 Aug  3 20:15 Typesetting/
-drwxrwxr-x  10 netsw  users    512 Jul  9 14:08 X11/
-

- -

In July 1996 I decided to make this archive public to - the world via a nice Web interface. "Nice" means that I - wanted to offer an interface where you can browse - directly through the archive hierarchy. And "nice" means - that I didn't want to change anything inside this - hierarchy - not even by putting some CGI scripts at the - top of it. Why? Because the above structure should later be - accessible via FTP as well, and I didn't want any - Web or CGI stuff mixed in there.

Solution:

The solution has two parts: The first is a set of CGI - scripts which create all the pages at all directory - levels on-the-fly. I put them under - /e/netsw/.www/ as follows:

- -

--rw-r--r--   1 netsw  users    1318 Aug  1 18:10 .wwwacl
-drwxr-xr-x  18 netsw  users     512 Aug  5 15:51 DATA/
--rw-rw-rw-   1 netsw  users  372982 Aug  5 16:35 LOGFILE
--rw-r--r--   1 netsw  users     659 Aug  4 09:27 TODO
--rw-r--r--   1 netsw  users    5697 Aug  1 18:01 netsw-about.html
--rwxr-xr-x   1 netsw  users     579 Aug  2 10:33 netsw-access.pl
--rwxr-xr-x   1 netsw  users    1532 Aug  1 17:35 netsw-changes.cgi
--rwxr-xr-x   1 netsw  users    2866 Aug  5 14:49 netsw-home.cgi
-drwxr-xr-x   2 netsw  users     512 Jul  8 23:47 netsw-img/
--rwxr-xr-x   1 netsw  users   24050 Aug  5 15:49 netsw-lsdir.cgi
--rwxr-xr-x   1 netsw  users    1589 Aug  3 18:43 netsw-search.cgi
--rwxr-xr-x   1 netsw  users    1885 Aug  1 17:41 netsw-tree.cgi
--rw-r--r--   1 netsw  users     234 Jul 30 16:35 netsw-unlimit.lst
-

- -

The DATA/ subdirectory holds the above - directory structure, i.e. the real - net.sw stuff, and gets - automatically updated via rdist from time to - time. The second part of the problem remains: how to link - these two structures together into one smooth-looking URL - tree? We want to hide the DATA/ directory - from the user while running the appropriate CGI scripts - for the various URLs. Here is the solution: first I put - the following into the per-directory configuration file - in the DocumentRoot - of the server to rewrite the public URL path - /net.sw/ to the internal path - /e/netsw:

- -

-RewriteRule  ^net.sw$       net.sw/        [R]
-RewriteRule  ^net.sw/(.*)$  e/netsw/$1
-

- -

The first rule is for requests which miss the trailing - slash! The second rule does the real thing. And then - comes the killer configuration which stays in the - per-directory config file - /e/netsw/.www/.wwwacl:

- -

-Options       ExecCGI FollowSymLinks Includes MultiViews
-
-RewriteEngine on
-
-#  we are reached via /net.sw/ prefix
-RewriteBase   /net.sw/
-
-#  first we rewrite the root dir to
-#  the handling cgi script
-RewriteRule   ^$                       netsw-home.cgi     [L]
-RewriteRule   ^index\.html$            netsw-home.cgi     [L]
-
-#  strip out the subdirs when
-#  the browser requests us from perdir pages
-RewriteRule   ^.+/(netsw-[^/]+/.+)$    $1                 [L]
-
-#  and now break the rewriting for local files
-RewriteRule   ^netsw-home\.cgi.*       -                  [L]
-RewriteRule   ^netsw-changes\.cgi.*    -                  [L]
-RewriteRule   ^netsw-search\.cgi.*     -                  [L]
-RewriteRule   ^netsw-tree\.cgi$        -                  [L]
-RewriteRule   ^netsw-about\.html$      -                  [L]
-RewriteRule   ^netsw-img/.*$           -                  [L]
-
-#  anything else is a subdir which gets handled
-#  by another cgi script
-RewriteRule   !^netsw-lsdir\.cgi.*     -                  [C]
-RewriteRule   (.*)                     netsw-lsdir.cgi/$1
-

- -

Some hints for interpretation:

- -

Notice the L (last) flag and no - substitution field ('-') in the fourth part
Notice the ! (not) character and - the C (chain) flag at the first rule - in the last part
Notice the catch-all pattern in the last rule

- -

- - Redirect Failing URLs to Another Web Server - -

Description:

A typical FAQ about URL rewriting is how to redirect - failing requests on webserver A to webserver B. Usually - this is done via ErrorDocument CGI scripts in Perl, but - there is also a mod_rewrite solution. - But note that this performs more poorly than using an - ErrorDocument - CGI script!

Solution:

The first solution has the best performance but less - flexibility, and is less safe:

- -

-RewriteEngine on
-RewriteCond   %{DOCUMENT_ROOT/%{REQUEST_URI} !-f
-RewriteRule   ^(.+)                             http://webserverB.dom/$1
-

- -

The problem here is that this will only work for pages - inside the DocumentRoot. While you can add more - Conditions (for instance to also handle homedirs, etc.) - there is a better variant:

- -

-RewriteEngine on
-RewriteCond   %{REQUEST_URI} !-U
-RewriteRule   ^(.+)          http://webserverB.dom/$1
-

- -

This uses the URL look-ahead feature of mod_rewrite. - The result is that this will work for all types of URLs - and is safe. But it does have a performance impact on - the web server, because for every request there is one - more internal subrequest. So, if your web server runs on a - powerful CPU, use this one. If it is a slow machine, use - the first approach or better an ErrorDocument CGI script.

- -

- - Archive Access Multiplexer - -

Description:

Do you know the great CPAN (Comprehensive Perl Archive - Network) under http://www.perl.com/CPAN? - CPAN automatically redirects browsers to one of many FTP - servers around the world (generally one near the requesting - client); each server carries a full CPAN mirror. This is - effectively an FTP access multiplexing service. - CPAN runs via CGI scripts, but how could a similar approach - be implemented via mod_rewrite?

Solution:

First we notice that as of version 3.0.0, - mod_rewrite can - also use the "ftp:" scheme on redirects. - And second, the location approximation can be done by a - RewriteMap - over the top-level domain of the client. - With a tricky chained ruleset we can use this top-level - domain as a key to our multiplexing map.

- -

-RewriteEngine on
-RewriteMap    multiplex                txt:/path/to/map.cxan
-RewriteRule   ^/CxAN/(.*)              %{REMOTE_HOST}::$1                 [C]
-RewriteRule   ^.+\.([a-zA-Z]+)::(.*)$  ${multiplex:$1|ftp.default.dom}$2  [R,L]
-

- -

-##
-##  map.cxan -- Multiplexing Map for CxAN
-##
-
-de        ftp://ftp.cxan.de/CxAN/
-uk        ftp://ftp.cxan.uk/CxAN/
-com       ftp://ftp.cxan.com/CxAN/
- :
-##EOF##
-

- -

- - Browser Dependent Content - -

Description:

At least for important top-level pages it is sometimes - necessary to provide the optimum of browser dependent - content, i.e., one has to provide one version for - current browsers, a different version for the Lynx and text-mode - browsers, and another for other browsers.

Solution:

We cannot use content negotiation because the browsers do - not provide their type in that form. Instead we have to - act on the HTTP header "User-Agent". The following config - does the following: If the HTTP header "User-Agent" - begins with "Mozilla/3", the page foo.html - is rewritten to foo.NS.html and the - rewriting stops. If the browser is "Lynx" or "Mozilla" of - version 1 or 2, the URL becomes foo.20.html. - All other browsers receive page foo.32.html. - This is done with the following ruleset:

- -

-RewriteCond %{HTTP_USER_AGENT}  ^Mozilla/3.*
-RewriteRule ^foo\.html$         foo.NS.html          [L]
-
-RewriteCond %{HTTP_USER_AGENT}  ^Lynx/.*         [OR]
-RewriteCond %{HTTP_USER_AGENT}  ^Mozilla/[12].*
-RewriteRule ^foo\.html$         foo.20.html          [L]
-
-RewriteRule ^foo\.html$         foo.32.html          [L]
-

- -

- - Dynamic Mirror - -

Description:

Assume there are nice web pages on remote hosts we want - to bring into our namespace. For FTP servers we would use - the mirror program which actually maintains an - explicit up-to-date copy of the remote data on the local - machine. For a web server we could use the program - webcopy which runs via HTTP. But both - techniques have a major drawback: The local copy is - always only as up-to-date as the last time we ran the program. It - would be much better if the mirror was not a static one we - have to establish explicitly. Instead we want a dynamic - mirror with data which gets updated automatically - as needed on the remote host(s).

Solution:

To provide this feature we map the remote web page or even - the complete remote web area to our namespace by the use - of the Proxy Throughput feature - (flag [P]):

- -

-RewriteEngine  on
-RewriteBase    /~quux/
-RewriteRule    ^hotsheet/(.*)$  http://www.tstimpreso.com/hotsheet/$1  [P]
-

- -

-RewriteEngine  on
-RewriteBase    /~quux/
-RewriteRule    ^usa-news\.html$   http://www.quux-corp.com/news/index.html  [P]
-

- -

- - Reverse Dynamic Mirror - -

Description:

...

Solution:

-RewriteEngine on
-RewriteCond   /mirror/of/remotesite/$1           -U
-RewriteRule   ^http://www\.remotesite\.com/(.*)$ /mirror/of/remotesite/$1
-

- -

- - Retrieve Missing Data from Intranet - -

Description:

This is a tricky way of virtually running a corporate - (external) Internet web server - (www.quux-corp.dom), while actually keeping - and maintaining its data on an (internal) Intranet web server - (www2.quux-corp.dom) which is protected by a - firewall. The trick is that the external web server retrieves - the requested data on-the-fly from the internal - one.

Solution:

First, we must make sure that our firewall still - protects the internal web server and only the - external web server is allowed to retrieve data from it. - On a packet-filtering firewall, for instance, we could - configure a firewall ruleset like the following:

- -

-ALLOW Host www.quux-corp.dom Port >1024 --> Host www2.quux-corp.dom Port 80
-DENY  Host *                 Port *     --> Host www2.quux-corp.dom Port 80
-

- -

Just adjust it to your actual configuration syntax. - Now we can establish the mod_rewrite - rules which request the missing data in the background - through the proxy throughput feature:

- -

-RewriteRule ^/~([^/]+)/?(.*)          /home/$1/.www/$2 [C]
-# REQUEST_FILENAME usage below is correct in this per-server context example 
-# because the rule that references REQUEST_FILENAME is chained to a rule that
-# sets REQUEST_FILENAME. 
-RewriteCond %{REQUEST_FILENAME}       !-f
-RewriteCond %{REQUEST_FILENAME}       !-d
-RewriteRule ^/home/([^/]+)/.www/?(.*) http://www2.quux-corp.dom/~$1/pub/$2 [P]
-

- -

- - Load Balancing - -

Description:

Suppose we want to load balance the traffic to - www.example.com over www[0-5].example.com - (a total of 6 servers). How can this be done?

Solution:

There are many possible solutions for this problem. - We will first discuss a common DNS-based method, - and then one based on mod_rewrite:

- -

- DNS Round-Robin - -
The simplest method for load-balancing is to use - DNS round-robin. - Here you just configure www[0-9].example.com - as usual in your DNS with A (address) records, e.g.,
- -
```
-www0   IN  A       1.2.3.1
-www1   IN  A       1.2.3.2
-www2   IN  A       1.2.3.3
-www3   IN  A       1.2.3.4
-www4   IN  A       1.2.3.5
-www5   IN  A       1.2.3.6
-
```
- -
Then you additionally add the following entries:
- -
```
-www   IN  A       1.2.3.1
-www   IN  A       1.2.3.2
-www   IN  A       1.2.3.3
-www   IN  A       1.2.3.4
-www   IN  A       1.2.3.5
-
```
- -
Now when www.example.com gets - resolved, BIND gives out www0-www5 - - but in a permutated (rotated) order every time. - This way the clients are spread over the various - servers. But notice that this is not a perfect load - balancing scheme, because DNS resolutions are - cached by clients and other nameservers, so - once a client has resolved www.example.com - to a particular wwwN.example.com, all its - subsequent requests will continue to go to the same - IP (and thus a single server), rather than being - distributed across the other available servers. But the - overall result is - okay because the requests are collectively - spread over the various web servers.
-
- DNS Load-Balancing - -
A sophisticated DNS-based method for - load-balancing is to use the program - lbnamed which can be found at - http://www.stanford.edu/~riepel/lbnamed/. - It is a Perl 5 program which, in conjunction with auxiliary - tools, provides real load-balancing via - DNS.
-
- Proxy Throughput Round-Robin - -
In this variant we use mod_rewrite - and its proxy throughput feature. First we dedicate - www0.example.com to be actually - www.example.com by using a single
- -
```
-www    IN  CNAME   www0.example.com.
-
```
- -
entry in the DNS. Then we convert - www0.example.com to a proxy-only server, - i.e., we configure this machine so all arriving URLs - are simply passed through its internal proxy to one of - the 5 other servers (www1-www5). To - accomplish this we first establish a ruleset which - contacts a load balancing script lb.pl - for all URLs.
- -
```
-RewriteEngine on
-RewriteMap    lb      prg:/path/to/lb.pl
-RewriteRule   ^/(.+)$ ${lb:$1}           [P,L]
-
```
- -
Then we write lb.pl:
- -
```
-#!/path/to/perl
-##
-##  lb.pl -- load balancing script
-##
-
-$| = 1;
-
-$name   = "www";     # the hostname base
-$first  = 1;         # the first server (not 0 here, because 0 is myself)
-$last   = 5;         # the last server in the round-robin
-$domain = "foo.dom"; # the domainname
-
-$cnt = 0;
-while (<STDIN>) {
-    $cnt = (($cnt+1) % ($last+1-$first));
-    $server = sprintf("%s%d.%s", $name, $cnt+$first, $domain);
-    print "http://$server/$_";
-}
-
-##EOF##
-
```
- - A last notice: Why is this useful? Seems like - www0.example.com still is overloaded? The - answer is yes, it is overloaded, but with plain proxy - throughput requests, only! All SSI, CGI, ePerl, etc. - processing is handled done on the other machines. - For a complicated site, this may work well. The biggest - risk here is that www0 is now a single point of failure -- - if it crashes, the other servers are inaccessible. -
- Dedicated Load Balancers - -
There are more sophisticated solutions, as well. Cisco, - F5, and several other companies sell hardware load - balancers (typically used in pairs for redundancy), which - offer sophisticated load balancing and auto-failover - features. There are software packages which offer similar - features on commodity hardware, as well. If you have - enough money or need, check these out. The lb-l mailing list is a - good place to research.
-

- -

- - New MIME-type, New Service - -

Description:

On the net there are many nifty CGI programs. But - their usage is usually boring, so a lot of webmasters - don't use them. Even Apache's Action handler feature for - MIME-types is only appropriate when the CGI programs - don't need special URLs (actually PATH_INFO - and QUERY_STRINGS) as their input. First, - let us configure a new file type with extension - .scgi (for secure CGI) which will be processed - by the popular cgiwrap program. The problem - here is that for instance if we use a Homogeneous URL Layout - (see above) a file inside the user homedirs might have a URL - like /u/user/foo/bar.scgi, but - cgiwrap needs URLs in the form - /~user/foo/bar.scgi/. The following rule - solves the problem:

- -

-RewriteRule ^/[uge]/([^/]+)/\.www/(.+)\.scgi(.*) ...
-... /internal/cgi/user/cgiwrap/~$1/$2.scgi$3  [NS,T=application/x-http-cgi]
-

- -

Or assume we have some more nifty programs: - wwwlog (which displays the - access.log for a URL subtree) and - wwwidx (which runs Glimpse on a URL - subtree). We have to provide the URL area to these - programs so they know which area they are really working with. - But usually this is complicated, because they may still be - requested by the alternate URL form, i.e., typically we would - run the swwidx program from within - /u/user/foo/ via hyperlink to

- -

-/internal/cgi/user/swwidx?i=/u/user/foo/
-

- -

which is ugly, because we have to hard-code - both the location of the area - and the location of the CGI inside the - hyperlink. When we have to reorganize, we spend a - lot of time changing the various hyperlinks.

Solution:

The solution here is to provide a special new URL format - which automatically leads to the proper CGI invocation. - We configure the following:

- -

-RewriteRule   ^/([uge])/([^/]+)(/?.*)/\*  /internal/cgi/user/wwwidx?i=/$1/$2$3/
-RewriteRule   ^/([uge])/([^/]+)(/?.*):log /internal/cgi/user/wwwlog?f=/$1/$2$3
-

- -

Now the hyperlink to search at - /u/user/foo/ reads only

- -

-HREF="*"
-

- -

which internally gets automatically transformed to

- -

-/internal/cgi/user/wwwidx?i=/u/user/foo/
-

- -

The same approach leads to an invocation for the - access log CGI program when the hyperlink - :log gets used.

- -

- - On-the-fly Content-Regeneration - -

Description:

Here comes a really esoteric feature: Dynamically - generated but statically served pages, i.e., pages should be - delivered as pure static pages (read from the filesystem - and just passed through), but they have to be generated - dynamically by the web server if missing. This way you can - have CGI-generated pages which are statically served unless an - admin (or a cron job) removes the static contents. Then the - contents gets refreshed.

Solution:

- This is done via the following ruleset: - -

-# This example is valid in per-directory context only
-RewriteCond %{REQUEST_FILENAME}   !-s
-RewriteRule ^page\.html$          page.cgi   [T=application/x-httpd-cgi,L]
-

- -

Here a request for page.html leads to an - internal run of a corresponding page.cgi if - page.html is missing or has filesize - null. The trick here is that page.cgi is a - CGI script which (additionally to its STDOUT) - writes its output to the file page.html. - Once it has completed, the server sends out - page.html. When the webmaster wants to force - a refresh of the contents, he just removes - page.html (typically from cron).

- -

- - Document With Autorefresh - -

Description:

Wouldn't it be nice, while creating a complex web page, if - the web browser would automatically refresh the page every - time we save a new version from within our editor? - Impossible?

Solution:

No! We just combine the MIME multipart feature, the - web server NPH feature, and the URL manipulation power of - mod_rewrite. First, we establish a new - URL feature: Adding just :refresh to any - URL causes the 'page' to be refreshed every time it is - updated on the filesystem.

- -

-RewriteRule   ^(/[uge]/[^/]+/?.*):refresh  /internal/cgi/apache/nph-refresh?f=$1
-

- -

Now when we reference the URL

- -

-/u/foo/bar/page.html:refresh
-

- -

this leads to the internal invocation of the URL

- -

-/internal/cgi/apache/nph-refresh?f=/u/foo/bar/page.html
-

- -

The only missing part is the NPH-CGI script. Although - one would usually say "left as an exercise to the reader" - ;-) I will provide this, too.

- -

-#!/sw/bin/perl
-##
-##  nph-refresh -- NPH/CGI script for auto refreshing pages
-##  Copyright (c) 1997 Ralf S. Engelschall, All Rights Reserved.
-##
-$| = 1;
-
-#   split the QUERY_STRING variable
-@pairs = split(/&/, $ENV{'QUERY_STRING'});
-foreach $pair (@pairs) {
-    ($name, $value) = split(/=/, $pair);
-    $name =~ tr/A-Z/a-z/;
-    $name = 'QS_' . $name;
-    $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
-    eval "\$$name = \"$value\"";
-}
-$QS_s = 1 if ($QS_s eq '');
-$QS_n = 3600 if ($QS_n eq '');
-if ($QS_f eq '') {
-    print "HTTP/1.0 200 OK\n";
-    print "Content-type: text/html\n\n";
-    print "&lt;b&gt;ERROR&lt;/b&gt;: No file given\n";
-    exit(0);
-}
-if (! -f $QS_f) {
-    print "HTTP/1.0 200 OK\n";
-    print "Content-type: text/html\n\n";
-    print "&lt;b&gt;ERROR&lt;/b&gt;: File $QS_f not found\n";
-    exit(0);
-}
-
-sub print_http_headers_multipart_begin {
-    print "HTTP/1.0 200 OK\n";
-    $bound = "ThisRandomString12345";
-    print "Content-type: multipart/x-mixed-replace;boundary=$bound\n";
-    &print_http_headers_multipart_next;
-}
-
-sub print_http_headers_multipart_next {
-    print "\n--$bound\n";
-}
-
-sub print_http_headers_multipart_end {
-    print "\n--$bound--\n";
-}
-
-sub displayhtml {
-    local($buffer) = @_;
-    $len = length($buffer);
-    print "Content-type: text/html\n";
-    print "Content-length: $len\n\n";
-    print $buffer;
-}
-
-sub readfile {
-    local($file) = @_;
-    local(*FP, $size, $buffer, $bytes);
-    ($x, $x, $x, $x, $x, $x, $x, $size) = stat($file);
-    $size = sprintf("%d", $size);
-    open(FP, "&lt;$file");
-    $bytes = sysread(FP, $buffer, $size);
-    close(FP);
-    return $buffer;
-}
-
-$buffer = &readfile($QS_f);
-&print_http_headers_multipart_begin;
-&displayhtml($buffer);
-
-sub mystat {
-    local($file) = $_[0];
-    local($time);
-
-    ($x, $x, $x, $x, $x, $x, $x, $x, $x, $mtime) = stat($file);
-    return $mtime;
-}
-
-$mtimeL = &mystat($QS_f);
-$mtime = $mtime;
-for ($n = 0; $n &lt; $QS_n; $n++) {
-    while (1) {
-        $mtime = &mystat($QS_f);
-        if ($mtime ne $mtimeL) {
-            $mtimeL = $mtime;
-            sleep(2);
-            $buffer = &readfile($QS_f);
-            &print_http_headers_multipart_next;
-            &displayhtml($buffer);
-            sleep(5);
-            $mtimeL = &mystat($QS_f);
-            last;
-        }
-        sleep($QS_s);
-    }
-}
-
-&print_http_headers_multipart_end;
-
-exit(0);
-
-##EOF##
-

- -

- - Mass Virtual Hosting - -

Description:

The VirtualHost feature of Apache is nice - and works great when you just have a few dozen - virtual hosts. But when you are an ISP and have hundreds of - virtual hosts, this feature is suboptimal.

Solution:

To provide this feature we map the remote web page or even - the complete remote web area to our namespace using the - Proxy Throughput feature (flag [P]):

- -

-##
-##  vhost.map
-##
-www.vhost1.dom:80  /path/to/docroot/vhost1
-www.vhost2.dom:80  /path/to/docroot/vhost2
-     :
-www.vhostN.dom:80  /path/to/docroot/vhostN
-

- -

-##
-##  httpd.conf
-##
-    :
-#   use the canonical hostname on redirects, etc.
-UseCanonicalName on
-
-    :
-#   add the virtual host in front of the CLF-format
-CustomLog  /path/to/access_log  "%{VHOST}e %h %l %u %t \"%r\" %>s %b"
-    :
-
-#   enable the rewriting engine in the main server
-RewriteEngine on
-
-#   define two maps: one for fixing the URL and one which defines
-#   the available virtual hosts with their corresponding
-#   DocumentRoot.
-RewriteMap    lowercase    int:tolower
-RewriteMap    vhost        txt:/path/to/vhost.map
-
-#   Now do the actual virtual host mapping
-#   via a huge and complicated single rule:
-#
-#   1. make sure we don't map for common locations
-RewriteCond   %{REQUEST_URI}  !^/commonurl1/.*
-RewriteCond   %{REQUEST_URI}  !^/commonurl2/.*
-    :
-RewriteCond   %{REQUEST_URI}  !^/commonurlN/.*
-#
-#   2. make sure we have a Host header, because
-#      currently our approach only supports
-#      virtual hosting through this header
-RewriteCond   %{HTTP_HOST}  !^$
-#
-#   3. lowercase the hostname
-RewriteCond   ${lowercase:%{HTTP_HOST}|NONE}  ^(.+)$
-#
-#   4. lookup this hostname in vhost.map and
-#      remember it only when it is a path
-#      (and not "NONE" from above)
-RewriteCond   ${vhost:%1}  ^(/.*)$
-#
-#   5. finally we can map the URL to its docroot location
-#      and remember the virtual host for logging purposes
-RewriteRule   ^/(.*)$   %1/$1  [E=VHOST:${lowercase:%{HTTP_HOST}}]
-    :
-

- -

- - Host Deny - -

Description:

How can we forbid a list of externally configured hosts - from using our server?

Solution:

For Apache >= 1.3b6:

- -

-RewriteEngine on
-RewriteMap    hosts-deny  txt:/path/to/hosts.deny
-RewriteCond   ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND} !=NOT-FOUND [OR]
-RewriteCond   ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND} !=NOT-FOUND
-RewriteRule   ^/.*  -  [F]
-

- -

For Apache <= 1.3b6:

- -

-RewriteEngine on
-RewriteMap    hosts-deny  txt:/path/to/hosts.deny
-RewriteRule   ^/(.*)$ ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND}/$1
-RewriteRule   !^NOT-FOUND/.* - [F]
-RewriteRule   ^NOT-FOUND/(.*)$ ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND}/$1
-RewriteRule   !^NOT-FOUND/.* - [F]
-RewriteRule   ^NOT-FOUND/(.*)$ /$1
-

- -

-##
-##  hosts.deny
-##
-##  ATTENTION! This is a map, not a list, even when we treat it as such.
-##             mod_rewrite parses it for key/value pairs, so at least a
-##             dummy value "-" must be present for each entry.
-##
-
-193.102.180.41 -
-bsdti1.sdm.de  -
-192.76.162.40  -
-

- -

- - Proxy Deny - -

Description:

How can we forbid a certain host or even a user of a - special host from using the Apache proxy?

Solution:

We first have to make sure mod_rewrite - is below(!) mod_proxy in the Configuration - file when compiling the Apache web server. This way it gets - called before mod_proxy. Then we - configure the following for a host-dependent deny...

- -

-RewriteCond %{REMOTE_HOST} ^badhost\.mydomain\.com$
-RewriteRule !^http://[^/.]\.mydomain.com.*  - [F]
-

- -

...and this one for a user@host-dependent deny:

- -

-RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST}  ^badguy@badhost\.mydomain\.com$
-RewriteRule !^http://[^/.]\.mydomain.com.*  - [F]
-

- -

- - Special Authentication Variant - -

Description:

Sometimes very special authentication is needed, for - instance authentication which checks for a set of - explicitly configured users. Only these should receive - access and without explicit prompting (which would occur - when using Basic Auth via mod_auth_basic).

Solution:

We use a list of rewrite conditions to exclude all except - our friends:

- -

-RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} !^friend1@client1.quux-corp\.com$
-RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} !^friend2@client2.quux-corp\.com$
-RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} !^friend3@client3.quux-corp\.com$
-RewriteRule ^/~quux/only-for-friends/      -                                 [F]
-

- -

- - Referer-based Deflector - -

Description:

How can we program a flexible URL Deflector which acts - on the "Referer" HTTP header and can be configured with as - many referring pages as we like?

Solution:

Use the following really tricky ruleset...

- -

-RewriteMap  deflector txt:/path/to/deflector.map
-
-RewriteCond %{HTTP_REFERER} !=""
-RewriteCond ${deflector:%{HTTP_REFERER}} ^-$
-RewriteRule ^.* %{HTTP_REFERER} [R,L]
-
-RewriteCond %{HTTP_REFERER} !=""
-RewriteCond ${deflector:%{HTTP_REFERER}|NOT-FOUND} !=NOT-FOUND
-RewriteRule ^.* ${deflector:%{HTTP_REFERER}} [R,L]
-

- -

... in conjunction with a corresponding rewrite - map:

- -

-##
-##  deflector.map
-##
-
-http://www.badguys.com/bad/index.html    -
-http://www.badguys.com/bad/index2.html   -
-http://www.badguys.com/bad/index3.html   http://somewhere.com/
-

- -

This automatically redirects the request back to the - referring page (when "-" is used as the value - in the map) or to a specific URL (when an URL is specified - in the map as the second argument).

- -

- -- 2.40.0

Using mod_rewrite to control access

See also

When not to use mod_rewrite

See also

Redirecting and Remapping with mod_rewrite

See also

See also

See also

See also