Apache

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Virtual Hosting

touch /etc/httpd/conf.d/virtual.conf

Virtual Host Configuration File: 

/etc/httpd/conf.d/virtual.conf:

HTTP Virtual Host 

NameVirtualHost *:80

<VirtualHost *:80>
    ServerName t0e.org
    ServerAlias www.t0e.org

    DocumentRoot /www

    ServerAdmin admin@t0e.org
    ErrorLog logs/t0e.org-error_log
    CustomLog logs/t0e.org-access_log common
</VirtualHost>

<VirtualHost *:80>
    ServerName www2.t0e.org
    ...
</VirtualHost>

HTTPS Virtual Host: 

NameVirtualHost *:443

<VirtualHost *:443>
    ServerName t0e.org
    ServerAlias www.t0e.org

    # SSL Enabled:
    SSLEngine on
    SSLCertificateFile /etc/t0e.org.pem

    # If using a godaddy certificate chain:
    #SSLCertificateFile /etc/contractpal.net.pem
    #SSLCertificateKeyFile /etc/contractpal.net.pem
    #SSLCertificateChainFile /etc/contractpal.net.pem

    #Forwarding Traffic
    # RewriteEngine on
    # RewriteRule ^(/.*)  http://localhost:8080/$1   [P]

    DocumentRoot /www

    ServerAdmin admin@t0e.org
    ErrorLog logs/t0e.org-error_log
    CustomLog logs/t0e.org-access_log common
</VirtualHost>

References:

CentOS common configuration changes

Keep alives: 

# KeepAlive Off
KeepAlive On

Hide Apache version: 

# ServerTokens Full
ServerTokens Prod

# ServerSignature On
ServerSignature Off

# in /etc/php.ini
expose_php = Off

Forwarding / Rewriting / Proxying Traffic

NameVirtualHost *:80
<VirtualHost *:80>
    ServerName t0e.org
    ServerAlias www.t0e.org

    #Forwarding Traffic
    RewriteEngine on
    RewriteRule ^(/.*)  http://localhost:8080/$1   [P]

    ServerAdmin admin@t0e.org
    ErrorLog logs/t0e.org-error_log
    CustomLog logs/t0e.org-access_log common
</VirtualHost>

Apache module mod_rewrite - RewriteRule - http://httpd.apache.org/docs/1.3/mod/mod_rewrite.html#RewriteRule 

a2enmod rewrite

a2enmod proxy_http

Module mod_rewrite - URL Rewriting Engine:

  • RewriteEngine
  • RewriteCond
  • RewriteRule

Apache 1.3 - URL Rewriting Guide

Apache module mod_proxy:

  • ProxyPass

--- 

<VirtualHost *:80>
    ServerName home.burgenerfamily.com
    DocumentRoot /www/home
    <Directory /www/home>
        Options FollowSymLinks
        RewriteEngine On
        # allow existing files and directories to pass through
        RewriteCond %{REQUEST_FILENAME} !-f
        RewriteCond %{REQUEST_FILENAME} !-d
        #RewriteRule ^static - [L,NC] 
        #RewriteCond %{REQUEST_FILENAME} !^favicon.ico$
        #RewriteCond %{REQUEST_FILENAME} !^static/
        #RewriteRule ^(.+)$ /index.php?title=$1 [PT,L,QSA]
        RewriteRule ^(.*)$ /index.php/$1 [L,QSA]
    </Directory>
    ErrorLog logs/home.burgenerfamily.com-error_log
    CustomLog logs/home.burgenerfamily.com-access_log common
</VirtualHost>

Proxy Pass

Enable Proxy: [1] 

sudo a2enmod proxy
sudo a2enmod proxy_http
systemctl restart apache2

Similar to forwarding, but takes care of redirects: 

  ProxyPass         /mirror/foo/ http://foo.com/
  ProxyPassReverse  /mirror/foo/ http://foo.com/

Suppose the local server has address http://wibble.org/; then 

  ProxyPass         /mirror/foo/ http://foo.com/
  ProxyPassReverse  /mirror/foo/ http://foo.com/

will not only cause a local request for the <http://wibble.org/mirror/foo/bar> to be internally converted into a proxy request to <http://foo.com/bar> (the functionality ProxyPass provides here). It also takes care of redirects the server foo.com sends: when http://foo.com/bar is redirected by him to http://foo.com/quux Apache adjusts this to http://wibble.org/mirror/foo/quux before forwarding the HTTP redirect response to the client. 

<VirtualHost *:80>
    ServerName wiki.oeey.com

    # Reverse Proxy
    ProxyPass         / http://localhost:8080/
    ProxyPassReverse  / http://localhost:8080/

    ServerAdmin website@oeey.com
    ErrorLog logs/wiki-error_log
    CustomLog logs/wiki-access_log common
</VirtualHost>

Proxy Pass to Jenkins: [2] 

NameVirtualHost *:80
<VirtualHost *:80>
    ServerName jenkins.oeey.com

    #Forwarding Traffic
    #RewriteEngine on
    #RewriteRule ^(/.*)  http://localhost:8080/$1   [P]

    ProxyPass         /  http://localhost:8080/ nocanon
    ProxyPassReverse  /  http://localhost:8080/
    ProxyRequests     Off
    ProxyPreserveHost On
    AllowEncodedSlashes NoDecode

    # Local reverse proxy authorization override
    # Most unix distribution deny proxy by default (ie /etc/apache2/mods-enabled/proxy.conf in Ubuntu)
    <Proxy http://localhost:8080/*>
        Order deny,allow
        Allow from all
    </Proxy>

    ServerAdmin admin@oeey.com
    ErrorLog logs/jenkins.oeey.com-error_log
    CustomLog logs/jenkins.oeey.com-access_log common
</VirtualHost>

Proxy Pass HTTPS

Proxy Pass to Jenkins: 

NameVirtualHost *:443
<VirtualHost *:443>
    ServerName jenkins.oeey.com

    # Enable SSL Support
    SSLEngine on
    SSLCertificateFile /etc/pki/tls/certs/localhost.crt
    SSLCertificateKeyFile /etc/pki/tls/private/localhost.key

    #Forwarding Traffic
    #RewriteEngine on
    #RewriteRule ^(/.*)  http://localhost:8080/$1   [P]

    ProxyPass         /  http://localhost:8080/ nocanon
    ProxyPassReverse  /  http://localhost:8080/
    ProxyPassReverse  /  http://jenkins.oeey.com/
    ProxyRequests     Off
    ProxyPreserveHost On
    AllowEncodedSlashes NoDecode
    RequestHeader set X-Forwarded-Proto "http"

    # Local reverse proxy authorization override
    # Most unix distribution deny proxy by default (ie /etc/apache2/mods-enabled/proxy.conf in Ubuntu)
    <Proxy http://localhost:8080/jenkins*>
        Order deny,allow
        Allow from all
    </Proxy>

    ServerAdmin admin@oeey.com
    ErrorLog logs/jenkins.oeey.com-error_log
    CustomLog logs/jenkins.oeey.com-access_log common
</VirtualHost>

Redirect

Redirect with URI intact: 

NameVirtualHost *:80
<VirtualHost *:80>
    ServerName test.oeey.com
    Redirect permanent / http://www.oeey.com/
</VirtualHost>

Redirect users to HTTPS with URI intact: 

NameVirtualHost *:80
<VirtualHost *:80>
    ServerName test.oeey.com
    Redirect permanent / https://test.oeey.com/
</VirtualHost>

Can be wrapped in Location (if you want) 

<Location />
  Redirect permanent / https://test.oeey.com/
</Location>

Redirect with RewriteEngine with URI intact: 

NameVirtualHost *:80
<VirtualHost *:80>
    ServerName test.oeey.com

    # Redirect HTTP to HTTPS
    RewriteEngine On
    RewriteCond %{HTTPS} off
    RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}
</VirtualHost>

Redirect removing URI: 

NameVirtualHost *:80
<VirtualHost *:80>
    ServerName test.oeey.com
    RedirectMatch "(.*)" "http://www.oeey.com/"
</VirtualHost>

Apache Module mod_alias:

  • Alias
  • Redirect
  • RedirectPermanent

Default Directory Index

to set the default pages to try and load (e.g. index.html, index.php): 

DirectoryIndex index.html index.php

Directory Index

To show full file names: 

  <Directory />
    Options Indexes
    IndexOptions NameWidth=*
  </Directory>

Sample: 

<Directory "/www">
    Options Indexes FollowSymLinks
    IndexOptions FancyIndexing NameWidth=*
    AllowOverride None
    Require all granted
</Directory>

Hide Apache and PHP Banner

Hide PHP version (X-Powered-By) - Edit php.ini: [3] 

expose_php = Off

Hide Apache version: [4] 

# ServerSignature On
ServerSignature Off

# ServerTokens Full
ServerTokens Prod

References:

.htaccess

Override configuration settings on a per directory (and sub directories) level with: 

.htaccess

Allow override of all configuration options: 

<Directory />
  AllowOverride All
</Directory>

Example directory browsing in .htaccess: 

Options +indexes

Allow from networks

<Directory "...">
    Order Deny,Allow
    Deny from all
    Allow from 127.0.0.0/255.255.255.0  10.10.0.0/16
</Directory>

Log Files

   ErrorLog logs/test.com-error_log
   CustomLog logs/test.com-access_log common

Make sure the soft link exists: 

ln -s /var/log/httpd /etc/httpd/logs      # RHEL based
ln -s /var/log/apache2 /etc/apache2/logs  # Debian Based


Log HTTPS X-Forwarded-For

Log the X-Forwarded-For header in apache... 

LogFormat "[X-Forwarded-For: %{X-Forwarded-For}i] %h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "[X-Forwarded-For: %{X-Forwarded-For}i] %h %l %u %t \"%r\" %>s %b" common
LogFormat "%{Referer}i -> %U" referer
LogFormat "%{User-agent}i" agent

PHP

Install PHP with Apache: (Ubuntu) 

#apt-get install apache2 php5 libapache2-mod-php5
apt-get install apache2 php libapache2-mod-php

Apache SSL

Apache can do virtual SSL hosting!

Install mod_ssl: [5] 

# rhel
yum install mod_ssl

# debian
sudo a2enmod ssl
sudo a2ensite default-ssl

/etc/httpd/conf.d/ssl.conf: 

LoadModule ssl_module modules/mod_ssl.so
Listen 443
AddType application/x-x509-ca-cert .crt
AddType application/x-pkcs7-crl    .crl
SSLPassPhraseDialog  builtin
SSLSessionCache         shmcb:/var/cache/mod_ssl/scache(512000)
SSLSessionCacheTimeout  300
SSLMutex default
SSLRandomSeed startup file:/dev/urandom  256
SSLRandomSeed connect builtin
SSLCryptoDevice builtin

Note: Delete the default VirtualHost section so we can add our own. 

# SSL Configuration - from ssl.conf virtual host example
SSLEngine On
SSLProtocol all -SSLv2
SSLCipherSuite ALL:!ADH:!EXPORT:!SSLv2:RC4+RSA:+HIGH:+MEDIUM:+LOW
SSLCertificateFile /etc/pki/tls/certs/localhost.crt
SSLCertificateKeyFile /etc/pki/tls/private/localhost.key

CustomLog logs/ssl_request_log \
          "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"

# SSL configuration
SSLEngine On
SSLCipherSuite ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL
SSLCertificateFile /etc/apache2/ssl/cert.crt
SSLCertificateKeyFile /etc/apache2/ssl/cert.key
SSLCertificateChainFile /etc/apache2/ssl/sf_bundle.crt

NameVirtualHost *:80
<VirtualHost *:80>
    ServerName default.t0e.org

    # Redirect HTTP to HTTPS
    RewriteEngine On
    RewriteCond %{HTTPS} off
    RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}
</VirtualHost>

NameVirtualHost *:443
<VirtualHost *:443>
    ServerName kb.t0e.org

    # SSL Enabled: (only once in config file)
    SSLEngine on
    SSLCertificateFile /etc/t0e.org.pem
    SSLCertificateKeyFile /etc/t0e.org.pem
    SSLProtocol all -SSLv2
    SSLCipherSuite ALL:!ADH:!EXPORT:!SSLv2:RC4+RSA:+HIGH:+MEDIUM:+LOW

    DocumentRoot /www

    ServerAdmin admin@kb.t0e.org.com
    ErrorLog logs/kb.t0e.org-error_log
    CustomLog logs/kb.t0e.org-access_log common
</VirtualHost>

<VirtualHost *:443>
    ServerName wiki.t0e.org

    DocumentRoot /www

    ServerAdmin admin@wiki.t0e.org.com
    ErrorLog logs/wiki.t0e.org-error_log
    CustomLog logs/wiki.t0e.org-access_log common
</VirtualHost>

Note: With SSL, Apache will always use the first default virtual hosts' certificate, so it only makes sense to define it there.

References:

--- chain ---

If you have a chain, create the pem as "key, cert, chain" and set Apache config like so: 

   SSLCertificateFile /etc/ssl.pem
   SSLCertificateKeyFile /etc/ssl.pem
   SSLCertificateChainFile /etc/ssl.pem

or just 

   SSLCertificateFile /etc/ssl.pem
   SSLCertificateChainFile /etc/ssl.pem

Linux System Password Protection

Using system accounts for HTTP authentication - http://wiki.zs64.net/Using_system_accounts_for_HTTP_authentication 

 httpd.conf

Edit httpd.conf to add these lines to the general configuration:

LoadModule auth_external_module libexec/apache2/mod_auth_external.so

(Should have been added by installing the port already.)

Add these lines to each virtual host where you'd like to use system accounts for authentication:

AddExternalAuth pwauth /usr/local/bin/pwauth SetExternalAuthMethod pwauth pipe

Add these lines to each Directory or Location section that you want protected by authentication:

AuthType Basic AuthExternal pwauth require valid-user

Password Protection with .htaccess and htpasswd

Sample .htaccess file: 

AuthUserFile /var/www/htpasswd
AuthGroupFile /dev/null
AuthName "Secret Place"
AuthType Basic
Require valid-user

#Require user <user>
#Require group <group>

To use with httpd.conf or virtual.conf, wrap in "<Directory>" tags: 

<Directory />
  AuthUserFile ...
  ...
</Directory>

Note: if you want in your httpd.conf (or virtual.conf) surround with "<Location />...</Location>"

To add password file: 

htpasswd -c /var/www/htpasswd admin
htpasswd /var/www/htpasswd user1

# if you want to create a blank username with password:
htpasswd /path/htpasswd


To use .htaccess: 

<Directory />
    Options FollowSymLinks
    AllowOverride AuthConfig
</Directory>

Or user the .htaccess generator


Apache HTTP Server - Require Directive:

Require user userid [userid] ...

Only the named users can access the resource.

Require group group-name [group-name] ...

Only users in the named groups can access the resource.

Require valid-user

All valid users can access the resource.
AuthType Basic
AuthName "Restricted Resource"
AuthUserFile /web/users
AuthGroupFile /web/groups
Require group admin

web based htpasswd manager

see change_htpasswd.pl

htpasswd.cgi by David Efflandt


Perl CGI Script to Modify User Passwords:

This allows users to manage / change their own passwords.

Use the Perl CGI script htpasswd.pl [cache]

  • Edit location of Perl .i.e.: /usr/bin/perl
    • Not /usr/local/bin/perl
  • Edit the script to specify location of the password file i.e. /var/www/PasswordDir/.htpasswd
  • SELinux users must add the correct attribute i.e. chcon -R -h -t httpd_sys_content_t /var/www/PasswordDir
  • The password file must be located in a directory where CGI is allowed to modify files.

File: httpd.conf (portion): 

..
...
<Directory "/var/www/PasswordDir">
    Options -Indexes
    AllowOverride None
    Options None
    Order allow,deny
    Allow from all
</Directory>
...
..

Directory Browsing

DocumentRoot /www/files
<Directory />
    Options FollowSymLinks +Indexes
    AllowOverride None
</Directory>

Note: The '+' may not be needed.

In a .htaccess: 

Options +indexes

Long file names: [6] 

IndexOptions NameWidth=*

For root indexes, the welcome.conf may be overriding with the welcome screen. Make the following change: [7] 

<LocationMatch "^/$>
    #Options -Indexes
    Options Indexes
    ErrorDocument 403 /error/noindex.html
</LocationMatch>

cgi

Script Alias folder: 

ScriptAlias /cgi-bin/ "C:/Program Files/Apache Group/Apache/cgi-bin/" 
ScriptAlias /cgi-bin/ "/var/www/cgi-bin/"

My favorite option, make all .cgi files executable: (This will need to be surrounded with '<Location />' or '<Directory />' tags) 

AddHandler cgi-script .cgi 
Options +ExecCGI

Note: Make sure to 'chmod +x' the files.

Example: 

<VirtualHost *:80>
    ServerName hg.t0e.org

    DirectoryIndex hgweb.cgi
    DocumentRoot /www/hg

    <Location />
        AddHandler cgi-script .cgi
        Options +ExecCGI
    </Location>

    ServerAdmin admin@hg.t0e.org
    ErrorLog logs/hg.t0e.org-error_log
    CustomLog logs/hg.t0e.org-access_log common
</VirtualHost>

Source: How to Add CGI Script Support (Perl, Python, etc) to Your Apache Server on Windows (thesitewizard.com)

--

Only files without an extension: 

<VirtualHost *:80>
    ServerName pi.t0e.org
    DocumentRoot /www/pi
    <Directory />
        AllowOverride All
    </Directory>
    DirectoryIndex index index.php index.html index.htm
    <Files ~ "^[a-zA-Z]*$">
        SetHandler cgi-script
        Options +ExecCGI
    </Files>

CentOS Default

#
# ScriptAliases are essentially the same as Aliases, except that
# documents in the realname directory are treated as applications and
# run by the server when requested rather than as documents sent to the client.
# The same rules about trailing "/" apply to ScriptAlias directives as to
# Alias.
#
ScriptAlias /cgi-bin/ "/var/www/cgi-bin/"

#
# "/var/www/cgi-bin" should be changed to whatever your ScriptAliased
# CGI directory exists, if you have that configured.
#
<Directory "/var/www/cgi-bin">
    AllowOverride None
    Options None
    Order allow,deny
    Allow from all
</Directory>

Python CGI

See Python#Apache_CGI

mod_proxy

prefork vs worker

Prefork performs better. Worker uses less memory. Prefork is most commonly used, and is the better choice for a web server.

To see which is compiled, and look for prefork.c or worker.c: 

# httpd -l
 
Compiled in modules:
  core.c
  prefork.c
  http_core.c
  mod_so.c

Statistics

Connections

Count active connections: 

netstat -ant | grep ESTABLISHED | grep :80 | wc -l

From PHP: 

<?php
$number_of_users = shell_exec('netstat -ant | grep ESTABLISHED | grep :80 | wc -l');
echo $number_of_users;
?>

References:


mod_status

mod_status - Apache HTTP Server


Summary

The Status module allows a server administrator to find out how well their server is performing. A HTML page is presented that gives the current server statistics in an easily readable form. If required this page can be made to automatically refresh (given a compatible browser). Another page gives a simple machine-readable list of the current server state.

The details given are:

  • The number of worker serving requests
  • The number of idle worker
  • The status of each worker, the number of requests that worker has performed and the total number of bytes served by the worker (*)
  • A total number of accesses and byte count served (*)
  • The time the server was started/restarted and the time it has been running for
  • Averages giving the number of requests per second, the number of bytes served per second and the average number of bytes per request (*)
  • The current percentage CPU used by each worker and in total by Apache (*)
  • The current hosts and requests being processed (*)

The lines marked "(*)" are only available if ExtendedStatus is On. 

LoadModule status_module modules/mod_status.so

#
# ExtendedStatus controls whether Apache will generate "full" status
# information (ExtendedStatus On) or just basic information (ExtendedStatus
# Off) when the "server-status" handler is called. The default is Off.
#
#ExtendedStatus On


#
# Allow server status reports generated by mod_status,
# with the URL of http://servername/server-status
# Change the ".example.com" to match your domain to enable.
#
#<Location /server-status>
#    SetHandler server-status
#    Order deny,allow
#    Deny from all
#    Allow from .example.com
#</Location>


References:

TRACE and TRACK

ISO Audit may result in this "Medium" risk detected:

"HTTP Methods Allowed. It is observed that HTTP methods GET HEAD TRACE OPTIONS are allowed on this host. Disable all unnecessary methods."
"HTTP TRACE / TRACK Methods Allowed. The remote webserver supports the TRACE and/or TRACK methods. TRACE and TRACK are HTTP methods that are used to debug web server connections. Disable these methods."

Disabling TRACE

Apache: Disable TRACE and TRACK methods | Racker Hacker:

Lots of PCI Compliance and vulnerability scan vendors will complain about TRACE and TRACK methods being enabled on your server. Since most providers run Nessus, you'll see this fairly often. Here's the rewrite rules to add: 

RewriteEngine on
RewriteCond %{REQUEST_METHOD} ^(TRACE|TRACK)
RewriteRule .* - [F]

These directives will need to be added to each VirtualHost.

For apache version 1.3.34 (or later 1.3.x versions), or apache 2.0.55 (or later), this has been made easy. Just add the line TraceEnable off 

TraceEnable off


Disabling the HTTP TRACE method:

The HTTP TRACE request method causes the data received by IBM HTTP Server from the client to be sent back to the client, as in the following example: 

$ telnet 127.0.0.1 8080
Trying...
Connected to 127.0.0.1.
Escape character is '^]'.
TRACE / HTTP/1.0
Host: foo
A: b
C: d

HTTP/1.1 200 OK
Date: Mon, 04 Oct 2004 14:07:59 GMT
Server: IBM_HTTP_SERVER
Connection: close
Content-Type: message/http

TRACE / HTTP/1.0
A: b
C: d
Host: foo

Connection closed.

The TRACE capability could be used by vulnerable or malicious applications to trick a web browser into issuing a TRACE request against an arbitrary site and then send the response to the TRACE to a third party using web browser features.

Making the required configuration changes: 

<VirtualHost www.example.com>
...
# disable TRACE in the www.example.com virtual host
RewriteEngine On 
RewriteCond %{REQUEST_METHOD} ^TRACE 
RewriteRule .* - [F] 
</VirtualHost>

Using SSL: 

$ /usr/linux/bin/openssl s_client -connect 127.0.0.1:8444

For more information...

More background information on the concerns with TRACE is provided at http://www.apacheweek.com/issues/03-01-24#news.

Other:

TraceEnable

Apache Core Features - http://httpd.apache.org/docs/1.3/mod/core.html#traceenable

TraceEnable: 

Syntax: TraceEnable [on|off|extended]
Default: TraceEnable on
Context: server config
Status: core (Windows, NetWare)
Compatibility: Available only in Apache 1.3.34, 2.0.55 and later

This directive overrides the behavior of TRACE for both the core server and mod_proxy. The default TraceEnable on permits TRACE requests per RFC 2616, which disallows any request body to accompany the request. TraceEnable off causes the core server and mod_proxy to return a 405 FORBIDDEN error to the client.

Finally, for testing and diagnostic purposes only, request bodies may be allowed using the non-compliant TraceEnable extended directive. The core (as an origin server) will restrict the request body to 64k (plus 8k for chunk headers if Transfer-Encoding: chunked is used). The core will reflect the full headers and all chunk headers with the request body. As a proxy server, the request body is not restricted to 64k. At this time the Apache 1.3 mod_proxy does not permit chunked request bodies for any request, including the extended TRACE request.


Disabling TRACK

The HTTP TRACK method

The TRACK method is a type of request supported by Microsoft web servers. It is not RFC compliant and is not supported directly by IBM HTTP Server. The method may be utilized as part of a cross-site scripting attack. See Vulnerability Note VU#288308 for more information.

Even though IBM HTTP Server does not support the TRACK method natively, it is possible for plug-in modules to provide support for it. To disable this capability for plug-in modules, in addition to disabling the TRACE method, add these two additional directives after the existing RewriteCond and RewriteRule directives which are used to disable TRACE:

RewriteCond %{REQUEST_METHOD} ^TRACK RewriteRule .* - [F]

Here is a full example showing the directives to disable both TRACE and TRACK: 

<VirtualHost www.example.com>
...
# disable TRACE and TRACK in the www.example.com virtual host
RewriteEngine On 
RewriteCond %{REQUEST_METHOD} ^TRACE 
RewriteRule .* - [F] 
RewriteCond %{REQUEST_METHOD} ^TRACK
RewriteRule .* - [F] 
</VirtualHost>

Attack

Cross-Site Tracing issues

Earlier this week a paper was published, "Cross-Site Tracing" which gave details of how the TRACE HTTP request could be used in Cross-Site Scripting attacks. Unfortunately this issue has not been very well understood by the media and has received a unwarranted amount of attention.

When an HTTP TRACE request is sent to a web server that supports it, that server will respond echoing the data that is passed to it, including any HTTP headers. The paper explains that some browsers can be scripted to perform a TRACE request. A browser with this functionality could be made to issue a TRACE request against an arbitrary site and pass the results on elsewhere. Since browsers will only send authentication details and cookies to the sites that issue them this means a user having a browser with this functionality could be tricked into sending their cookies or authentication details for arbitrary sites to an attacker.

For example, if you visited a page that an attacker has carefully crafted, the page could cause your browser to bounce a TRACE request against some site for which you have authentication cookies. The result of the TRACE will be a copy of what was sent to the site, which will therefore include those cookies or authentication data. The carefully crafted page can then pass that information on to the attacker.

TRACE requests can be disabled by making a change to the Apache server configuration. Unfortunately it is not possible to do this using the Limit directive since the processing for the TRACE request skips this authorisation checking. Instead the following lines can be added which make use of the mod_rewrite module. 

   RewriteEngine On 
   RewriteCond %{REQUEST_METHOD} ^TRACE 
   RewriteRule .* - [F]

Although the particular attack highlighted made use of the TRACE functionality to grab authentication details, this isn't a vulnerability in TRACE, or in the Apache web server. The same browser functionality that permits the published attack can be used for different attacks even if TRACE is disabled on the remote web server. For example an attacker could create a carefully crafted page that when visited submits a hidden request to some arbitrary site through your browser, grabs the result and passes it to the attacker.

Performance Tuning

See Linux Performance Tuning

Apache and Firewall Performance Tips from the Xenu.net Masters

CentOS January 2009 Thread

-------- Original Message --------
Subject: 	[CentOS] Apache Server Tuning for Performance
Date: 	Wed, 21 Jan 2009 00:09:38 +0530
From: 	linux-crazy <hicheerup@gmail.com>
Reply-To: 	CentOS mailing list <centos@centos.org>
To: 	CentOS mailing list <centos@centos.org>


Hi all,

I am facing  facing performance issues with our web servers which is
working for concurrent  250 requests properly and then stops
responding when the requests are more than 250 .

The current configuration parameters are as follows :

apachectl -version
Server version: Apache/2.0.52
Server built:   Jan 30 2007 09:56:16

Kernel : 2.6.9-55.ELsmp #1 SMP Fri Apr 20 16:36:54 EDT 2007 x86_64
x86_64 x86_64 GNU/Linux

Server Hardware :
MAIN MEMORY
(i) Memory Size 4 GB  Dual-Core Intel 5160 processors.

httpd.conf

Timeout 300
KeepAlive On
MaxKeepAliveRequests 1000
KeepAliveTimeout 150

## Server-Pool Size Regulation (MPM specific)
# prefork MPM

# StartServers: number of server processes to start
# MinSpareServers: minimum number of server processes which are kept spare
# MaxSpareServers: maximum number of server processes which are kept spare
# ServerLimit: maximum value for MaxClients for the lifetime of the server
# MaxClients: maximum number of server processes allowed to start
# MaxRequestsPerChild: maximum number of requests a server process serves

<IfModule prefork.c>

StartServers       8
MinSpareServers    5
MaxSpareServers   20
ServerLimit      251
MaxClients       251
MaxRequestsPerChild  4000
</IfModule>

# worker MPM
# StartServers: initial number of server processes to start
# MaxClients: maximum number of simultaneous client connections
# MinSpareThreads: minimum number of worker threads which are kept spare
# MaxSpareThreads: maximum number of worker threads which are kept spare
# ThreadsPerChild: constant number of worker threads in each server process
# MaxRequestsPerChild: maximum number of requests a server process serves
<IfModule worker.c>
StartServers         2
MaxClients        150
MinSpareThreads     25
MaxSpareThreads     75
ThreadsPerChild     25
MaxRequestsPerChild  0
</IfModule>

     I want to  know about  the difference  between worker MPM and
Prefork MPM , how to find out which one will be used by my apache
server and  the recommended one   for highly loaded server.If some one
provide me the link that best explains above two comparison also  be
very use full.


 Can any one guide me tuning to be  done for the maximum utilization
of the Resources  and better performance of the Servers.

 Regards,
lingu
_______________________________________________
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CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos

Only use prefork MPM (worker is for Win32, AFAIK).

If you set ServerLimit to 251, that's the limit.
Set ServerLimit and MaxClients to the same value.
(Larger than 250)
OK?
And take a couple of minutes to study the apache documentation. It's  
actually quite good and tranlated into many languages...

BUT: what your server is being able to handle also depends on what you  
actually serve (PHP/JSP/Servelets/Perl/whatever!

This is usually not a problem that is easily described and solved in  
two sentences.

Rainer

Increase your MaxClients configuration, also enable if you
haven't already the server-status module and monitor the
server via http://<your server name>/server-status it will
show how many workers are busy and what they are doing.

As for which to use, prefork is the old forked method of
doing things, the other uses threads. Depending on what kind
of application your running on top of apache, if it is not
thread safe(at some point many PHP modules were not thread
safe), you may want to use prefork. Otherwise you can use
the threading model.

If your not sure I'd say stick to prefork to be safe until
you can determine for sure that threading is safe.

nate

Most list members would likely advise sticking with the prefork 
configuration.  Without knowing what kind of applications you are 
running on your webserver, I wouldn't suggest changing it.

Merely increasing the number of workers might make performance worse.

Use ps or top to figure out how much each apache worker is using. Then 
decide how much ram you want to dedicate on your server to Apache, 
without going into swap. (Over-allocating and then paging out memory 
will only make performance much worse.) For example, if I have 2G or 
ram, and I want 1.5 for apache workers, my average apache worker size 
(resident memory) is 65MB, then I have room for 23 workers. (1024 * 1.5 
) / 65. (There are more accurate ways to calculate this usage, like 
taking shared memory into account.)

Upgrading the ram in your web server is a pretty fast interim solution.

Consider your application performance, too. The longer a request in your 
application takes, the more workers are in use on your web server, 
taking up more memory. If you have long-running queries in your 
database, take care of those first.

Good luck

Jed

Jed Reynolds wrote:
> 
> Merely increasing the number of workers might make performance worse.
> 
> Use ps or top to figure out how much each apache worker is using. Then 
> decide how much ram you want to dedicate on your server to Apache, 
> without going into swap. (Over-allocating and then paging out memory 
> will only make performance much worse.)  For example, if I have 2G or
> ram, and I want 1.5 for apache workers, my average apache worker size 
> (resident memory) is 65MB, then I have room for 23 workers. (1024 * 1.5 
> ) / 65. (There are more accurate ways to calculate this usage, like 
> taking shared memory into account.)

Pay attention to shared memory when doing this.  A freshly-forked 
process shares virtually all RAM with its parent.  How much and how 
quickly this changes varies wildly with the application type and 
activity that causes the child's data to become unique.  With some types 
of applications (especially mod_perl) you may want to tune down the 
number of hits each child services to increase memory sharing.  Also, if 
you are running external cgi programs you must take them into account.

> Upgrading the ram in your web server is a pretty fast interim solution.
> 
> Consider your application performance, too. The longer a request in your 
> application takes, the more workers are in use on your web server, 
> taking up more memory. If you have long-running queries in your 
> database, take care of those first.

You may also have to turn off or tune down the HTTP 1.1 connection 
keepalives, trading the time it takes to establish a new connection for 
the RAM it takes to keep the associated process waiting for another 
request from the same client.

-- 
   Les Mikesell
    lesmikesell@gmail.com

Also take a look at apache alternatives like lighttpd and nginx. In certain
cases they do miracles.

Jure Pečar

I don't know about lighttpd (our results were mixed) - but NGINX is  
really _very_ fast.
Last time I checked, it seems to be the fastest way to accelerate  
webpage-delivery on generic hardware and with OSS-software.

But it's not a feature-monster like apache, so you still need that.

Rainer

Linux-crazy wrote on Wed, 21 Jan 2009 00:09:38 +0530:

> KeepAliveTimeout 150

My god, reduce this to 10 or 5.

> ServerLimit      251
> MaxClients       251

There's your limit. However, you should check with your hardware if upping 
it is really desirable. With 4 GB I think you won't be able to handle much 
more anyway.

Kai

Kai Schaetzl wrote:
> There's your limit. However, you should check with your hardware if upping 
> it is really desirable. With 4 GB I think you won't be able to handle much 
> more anyway.

That really depends. If you only shove out static pages and have one or
two or three odd cgis on the machine, you can flatten down the httpd
binary quite a bit by throwing out unneeded modules.

500 to 750 clients shouldn't be that much of a problem then ...

Cheers,

Ralph

Ralph Angenendt wrote on Wed, 21 Jan 2009 10:52:59 +0100:

> That really depends. If you only shove out static pages and have one or
> two or three odd cgis on the machine, you can flatten down the httpd
> binary quite a bit by throwing out unneeded modules.
> 
> 500 to 750 clients shouldn't be that much of a problem then ...

Sure it depends ;-) I do serve dynamic pages but by removing the really 
unnecessary modules I made my httpds much faster (especially on pipelined 
image downloads) and they only have some 10 MB (RES) per worker.

But I would expect that they are running the default set of modules.

Kai

Kai Schaetzl schrieb:
> Ralph Angenendt wrote on Wed, 21 Jan 2009 10:52:59 +0100:
>
>   
>> That really depends. If you only shove out static pages and have one or
>> two or three odd cgis on the machine, you can flatten down the httpd
>> binary quite a bit by throwing out unneeded modules.
>>
>> 500 to 750 clients shouldn't be that much of a problem then ...
>>     
>
> Sure it depends ;-) I do serve dynamic pages but by removing the really 
> unnecessary modules I made my httpds much faster (especially on pipelined 
> image downloads) and they only have some 10 MB (RES) per worker.
>
> But I would expect that they are running the default set of modules.
>
> Kai
>
>   

If you can separate-out the images to a specific URL (img.domain.com)
and put them all in the same directory, you can use NGINX to serve them.
Of course, the actual transfer-speed will not increase much - but
latency will go down to the absolute minimum.
And latency is what makes a page appear "fast" or "slow" to customers.

Ralph Angenendt wrote:
> Kai Schaetzl wrote:
>> There's your limit. However, you should check with your hardware if upping
>> it is really desirable. With 4 GB I think you won't be able to handle much
>> more anyway.
>
> That really depends. If you only shove out static pages and have one or
> two or three odd cgis on the machine, you can flatten down the httpd
> binary quite a bit by throwing out unneeded modules.
>
> 500 to 750 clients shouldn't be that much of a problem then ...

Yeah gotta monitor it.. just checked in on some servers I ran at
my last company and the front end proxies (99% mod_proxy) seem to
peak out traffic wise at about 230 workers. For no other reason other
than because I could each proxy has 8 apache instances running(4 for
HTTP 4 for HTTPS). CPU usage peaks at around 3%(dual proc single core),
memory usage around 800MB. About 100 idle workers. Keepalive was set
to 300 seconds due to poor application design.

One set of back end apache servers peaks traffic wise at around 100
active workers, though memory usage was higher, around 2GB because
of mod_fcgid running ruby on rails. CPU usage seems to be at around
25%(dual proc quad core) for that one application.

Each back end application had it's own dedicated apache instance(11
apps) for maximum stability/best performance monitoring. The bulk
of them ran on the same physical hardware though.

Traffic routing was handled by a combination of F5 load balancers
and the apache servers previously mentioned(F5 iRules were too slow
and F5's TMM was not scalable at the time).

nate

> 
> > KeepAliveTimeout 150
> 
>reduce this to 10 or 5.
> 
> 
> Kai
> 
> --
> Kai Schätzl, Berlin, Germany

Kai,

what do you think about the "general Timeout

it is set to 300

ive never much thought about it, yet should we be consider and possible
reduce that one too?

 - rh

RobertH wrote on Wed, 21 Jan 2009 11:26:41 -0800:

> what do you think about the "general Timeout
> 
> it is set to 300
> 
> ive never much thought about it, yet should we be consider and possible
> reduce that one too?

I'm using 120, but I don't think reducing this value has much impact.

Kai


Load Balancer

Apache Load Balancer

mod_proxy_balancer - Apache HTTP Server - mod_proxy_balancer - http://httpd.apache.org/docs/2.2/mod/mod_proxy_balancer.html 

<Proxy balancer://mycluster>
BalancerMember http://192.168.1.50:80
BalancerMember http://192.168.1.51:80
</Proxy>
ProxyPass /test balancer://mycluster

User Directories

Default: 

UserDir public_html

Results in: 

~/public_html/

To disable user directories: 

UserDir disabled

Ubuntu user dir config: 

        UserDir public_html
        UserDir disabled root

        <Directory /home/*/public_html>
                AllowOverride FileInfo AuthConfig Limit Indexes
                Options MultiViews Indexes SymLinksIfOwnerMatch IncludesNoExec
                <Limit GET POST OPTIONS>
                        Order allow,deny
                        Allow from all
                </Limit>
                <LimitExcept GET POST OPTIONS>
                        Order deny,allow
                        Deny from all
                </LimitExcept>
        </Directory>

References:

Minimal Memory Instance

Assuming running prefork module (check with 'apache -l'): 

KeepAlive off

<IfModule mpm_prefork_module>
StartServers          2
MinSpareServers       2
MaxSpareServers      5
ServerLimit          20
MaxClients           20
MaxRequestsPerChild  10000
</IfModule>

References:

---

TODO See:

Issues

Could not reliably determine domain name

Warning: 

Could not reliably determine the server's fully qualified domain name

Solution:

  • Force ServerName in apache configs [8]
ServerName localhost

client denied by server configuration

browser: 

403 Forbidden - You don't have permission to access / on this server.

Error: 

==> httpd/default-error_log <==
[Mon Sep 01 21:42:02.273169 2014] [authz_core:error] [pid 11221] [client 174.52.47.54:50675] AH01630: client denied by server configuration: /www/

Add Directory allow permissions: [9] 

DocumentRoot /www
<Directory /www>
  Order allow,deny
  Allow from all
</Directory>

or this worked better for me: [10] [11] 

DocumentRoot /www
<Directory /www>
  Require all granted
</Directory>

Actually this just worked on the latest Ubuntu system: 

<Directory /www/>
        Options Indexes FollowSymLinks
        AllowOverride None
        Require all granted
</Directory>

References:

permissions missing component path

==> httpd/default-error_log <==
[Mon Sep 01 21:50:09.256120 2014] [core:error] [pid 11511] (13)Permission denied: [client 174.52.47.54:50744] AH00035: access to \
/index.html denied (filesystem path '/www/index.html') because search permissions are missing on a component of the path

keywords

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