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Creating a Hello World! Apache Module with KDevelop on Ubuntu

Mon, 12/24/2007 - 04:06 — Chris Barber

The Apache HTTP Web Server is a powerful and extensible web server that is the "A" in "LAMP". One of the neat things about Apache is its API for writing custom modules.

Nick Kew wrote an excellent book called The Apache Modules Book. Anyone who is serious about Apache module development must buy this book.

Modules can be written a number of ways, but the most common way is to use the C programming language. For an C/C++ development IDE, I use KDevelop. It is pretty easy to use once you figure out what you need to do.

It is possible to write modules in C++, but I don't recommend it if your module's source can't be contained in a single source file. There's all sorts of interesting issues with exported symbols and static function declarations. Another reason to stick with C is pretty much all core modules and examples are written using C. You may give it a try and determine that it works just fine for your project.

Prerequisites

Before you begin, there is a handful of applications and libraries you must have installed:

Apache 2
KDevelop 3.4
GCC (bundled with "build-essential" package)
automake
autoconf

Creating the Project

Launch KDevelop and select "New Project" from the Project menu. Since we are focusing on using C, select "Simple Hello world program" under the "C" folder. Give your module an "Application name" and specify the location to create the project.

On the next page of the wizard, you must enter your name, but your email address is not required.

The next couple wizard screens ask about version control and source templates. After finishing the wizard, you will be back at the IDE with the new project created.

The Code

Delete all of the source code that the editor created. Next paste the following code which originated from Nick's version on The Apache Modules Book Companion site.

#include <httpd.h>
#include <http_protocol.h>
#include <http_config.h>

static int helloworld_handler(request_rec* r)
{
	if (!r->handler || strcmp(r->handler, "helloworld"))
		return DECLINED;
	
	if (r->method_number != M_GET)
		return HTTP_METHOD_NOT_ALLOWED;
	
	ap_set_content_type(r, "text/html;charset=ascii");
	ap_rputs("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01//EN\">\n", r);
	ap_rputs("<html><head><title>Hello World!</title></head>", r);
	ap_rputs("<body><h1>Hello World!</h1></body></html>", r);
	return OK;
}

static void register_hooks(apr_pool_t* pool)
{
	ap_hook_handler(helloworld_handler, NULL, NULL, APR_HOOK_MIDDLE);
}

module AP_MODULE_DECLARE_DATA helloworld_module = {
	STANDARD20_MODULE_STUFF,
	NULL,
	NULL,
	NULL,
	NULL,
	NULL,
	register_hooks
};

Configuring the Project

Next we need to reconfigure the build target to create a library instead of a normal program. Right-click the build target and click "Remove":

When the dialog displays, uncheck the "Also remove from disk" option before clicking "OK". Now we need to add a new build target. Right-click the "src" folder and select "Add Target":

From the "Add Target" dialog, change the type to "Libtool Library" and enter the name of the module. Also check the "-avoid-version" and "-module" options.

As soon as the target is created, right-click on it and make sure the checked options saved properly. Right-click on the target again and select "Make Target Active":

Edit the project's options by right-clicking the "src" folder and selecting "Options":

Since this is a C project, we want to add the following options to the "CFLAGS" field:

-DLINUX=2 -D_GNU_SOURCE -D_LARGEFILE64_SOURCE -D_REENTRANT -pthread

From the "Includes" tab, add the following outside include directories:

/usr/includes/apr-1.0
/usr/includes/apache2

Reorder the include paths so that "$(all_includes)" is first. Due to a bug or poor design, you must edit the two paths you just added and prepend a "-I":

Since we deleted the old build target, we need to add the source files to the target by right-clicking the target and selecting "Add Existing Files":

From the dialog, drag and drop the files you want to be apart of the target. For this simple example, we only move the "mod_helloworld.c" file.

Building the Project

We are all set to compile the project. From the "Build" menu, select "Build Active Target":

If this is the first time you are performing the build, KDevelop will prompt you whether or not you want to run automake. Click the "Run Them" button to continue.

When the build is finished, the "Messages" panel will show up and display the build results. If everything went as planned, the output will say the build was successful.

Deploying the Module

The build process put the shared library file in the following location (assuming debug build):

/path/to/mod_helloworld/debug/src/.libs/libmod_helloworld

We need to install that file in the Apache modules directory which on Ubuntu is:

/usr/lib/apache2/modules

From a terminal, run the following command as root or sudo:

cp /path/to/mod_helloworld/debug/src/.libs/libmod_helloworld \
    /usr/lib/apache2/modules/mod_helloworld.so

Next you'll need to edit the Apache configuration file. In Ubuntu, the file is located at:

/etc/apache2/apache2.conf

You need to add the LoadModule and <Location> directives so Apache knows when to invoke the module.

LoadModule helloworld_module /usr/lib/apache2/modules/mod_helloworld.so
<Location /helloworld>
    SetHandler helloworld
</Location>

I've had spotty luck where to actually insert those settings. After the LogLevel, but before any other LoadModule entries seems to work for me. After you save the changes, restart Apache using the following command as root or sudo:

apache2ctl restart

If your Apache acts funny, try restarting it again.

Testing the Module

The last step is to test the module. Open up your favorite web browser and hit http://localhost/helloworld:

If everything worked, you should see something similar to the image above.

Where To Go From Here

We have only scratched the surface. The Apache Portable Runtime (APR) provides a ton of functionality that makes developing modules much easier. The Apache Modules Book dives into several topics such as configuration settings, content generators, filters, and database connectivity.

Another great resource is Apache's own module source code in their Subversion repository: http://svn.apache.org/viewvc/httpd/httpd/trunk/modules/.

Creating Self-Signed Certs on Apache 2.2

Sun, 05/13/2007 - 17:07 — Chris Barber

Security is a always a big concern and there's no reason your website should go unsecure. You can secure your Apache website with a self-signed SSL certificate. This post describes the process using Apache 2.2 and OpenSSL on a Ubuntu Linux server.

Begin by generating a private key:

> openssl genrsa -out mycert.key 1024

Next, generating a certificate request and enter the information:

> openssl req -new -key mycert.key -out mycert.csr
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:
State or Province Name (full name) [Some-State]:
Locality Name (eg, city) []:
Organization Name (eg, company) [Internet Widgits Pty Ltd]:
Organizational Unit Name (eg, section) []:
Common Name (eg, YOUR name) []:
Email Address []:

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:

Next, generate the self-signed certificate. You can specify the number of days the cert is valid for.

> openssl x509 -req -days 365 -in mycert.csr -signkey mycert.key -out mycert.cert
Signature ok
subject=/C=/ST=/L=/O=/CN=
Getting Private key

You no longer need the .csr request file. Create a folder and move the .key and .cert files into it:

> sudo mkdir /etc/apache2/ssl
> sudo mv *.cert /etc/apache2/ssl
> sudo mv *.key /etc/apache2/ssl
> sudo chmod 400 /etc/apache2/ssl/*.key

If the cert is protected with a password, by default Apache will prompt for the password when it starts. This can be a problem since you will need to enter the password each time Apache is restarted. We can fix this by having Apache call a program that returns the password.

Create the shell script /etc/apache2/ssl/password.sh and enter the following:

#!/bin/bash
echo “password”;

Next we need to tell Apache to run the script. Apache's SSL settings are stored in:

/etc/apache2/mods-enabled/ssl.conf

Edit the file and change the SSLPassPhraseDialog to:

SSLPassPhraseDialog exec:/etc/apache2/ssl/password.sh

The last step is to assign the certificate to your Apache site by editing the sites file:

/etc/apache2/sites-enabled/000-default

You'll need to configure the SSL settings for the site:

<VirtualHost 192.168.1.100:443>
        ...
        SSLEngine on
        SSLCertificateFile /etc/apache2/ssl/mycert.cert
        SSLCertificateKeyFile /etc/apache2/ssl/mycert.key
        ...
</VirtualHost>

Don't forget to tell Apache to listen on port 443 in the /etc/apache2/ports.conf file. Restart Apache with sudo apache2ctl restart and you should be a little closer to being secure.

Creating Self-Signed Certs on Apache Tomcat 5.5

Sat, 05/12/2007 - 09:13 — Chris Barber

Recently I needed to generate a self-signed SSL cert for Apache Tomcat 5.5 on my Ubuntu Linux server. The basic process is to create a Java keystore with the self-signed cert, change Tomcat's configuration file, and restart the server. Here's how I did it:

> keytool -genkey -alias tomcat -keyalg RSA -keystore mycert.jks
Enter keystore password:  changeit
What is your first and last name?
  [Unknown]:  Chris Barber
What is the name of your organizational unit?
  [Unknown]:  
What is the name of your organization?
  [Unknown]:  CB1, INC.
What is the name of your City or Locality?
  [Unknown]:  Minneapolis
What is the name of your State or Province?
  [Unknown]:  MN
What is the two-letter country code for this unit?
  [Unknown]:  US
Is CN=Chris Barber, OU=Unknown, O="CB1, INC.", L=Minneapolis, ST=MN, C=US correct?
  [no]:  yes

Enter key password for 
        (RETURN if same as keystore password):

By default, Tomcat will assume the password as "changeit". You can change the password, but then you need to set the keystorePass in Tomcat's configuration file. Regardless, the password for both the keystore and the cert MUST be the same. Store the keystore in a safe place such as Tomcat's configuration folder:

/etc/tomcat5.5

Next edit Tomcat's server configuration file:

/etc/tomcat5.5/server.xml

Locate the SSL connector declaration, uncomment it, and add the keystoreFile path:

<!-- Define a SSL HTTP/1.1 Connector on port 8443 -->
<Connector port="8443" maxHttpHeaderSize="8192"
        maxThreads="150" minSpareThreads="25" maxSpareThreads="75"
        enableLookups="false" disableUploadTimeout="true"
        acceptCount="100" scheme="https" secure="true"
        keystoreFile="/etc/tomcat5.5/mycert.jks"
        clientAuth="false" sslProtocol="TLS" />

Save the changes and restart Tomcat:

sudo /etc/init.d/tomcat5.5 restart

You should be good to go at this point. Launch your favorite web browser and go to https://localhost:8443.

Now you are secure and ready to rock.

CB1, INC.

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