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diff --git a/apache.asciidoci b/apache.asciidoci new file mode 100644 index 0000000..8c3b259 --- /dev/null +++ b/apache.asciidoci @@ -0,0 +1,134 @@ +== Apache Practical, Week 4 == + +This practical is about installing and configuring an Apache web server. Since +we need special features (e.g. support for PCRE), we cannot just install the +version provided by our package manager. Instead, we have to build Apache from +source. + +At the end of the practical, we should be able to access public pages on the +web server but also private pages which require HTTP authentication. + +=== Problem 1: Dependencies issue with APR and APR-Util === + +When we try to configure the build of Apache for the first time, it complains +about missing dependencies: APR (Apache Portable Runtime) and APR-util (Apache +Portable Runtime Utility). i.e. a command looking like this: + + $ ./configure --prefix=<pfx> --with-included-apr --with-pcre=/usr/local/pcre + +gives this output: + + > configure: error: Bundled APR requested but not found at ./srclib/. + > Download and unpack the corresponding apr and apr-util packages to ./srclib/. + +==== Resolution ==== + +Because these two libraries have to be linked with Apache during the build +process, we have to install them in order to be able to build. + +Apache build system already provides us a directory './srclib/' that can be used to +build the libraries along with the Apache itself. It saves us the time of +building them separately. So all we have to do is download the source code of +these two libraries and extract them is './srclib/' + + $ wget -q http://mir2.ovh.net/ftp.apache.org/dist//apr/apr-1.5.1.tar.gz + $ tar xzf apr-1.5.1.tar.gz -C ./srclib/ + $ wget -q http://apache.websitebeheerjd.nl//apr/apr-util-1.5.4.tar.gz + $ tar xzf apr-util-1.5.4.tar.gz -C ./srclib/ + +Since Apache build process expects directories named 'apr' and 'apr-util', we can +create symlinks. + + $ ln -s apr-1.5.1 srclib/apr + $ ln -s apr-util-1.5.4 srclib/apr-util + +Another attempt of running './configure' confirms us that APR and APR-util are +now in place and ready to be built. + +=== Problem 2: pcre-config is not found + +Even though, there is no more dependency issues with APR, the build process now +complains about a missing binary: 'pcre-config' + + > configure: error: pcre-config for libpcre not found. PCRE is required and available from http://pcre.org/ + +==== Resolution ==== + +'pcre-config' and eventually most of '-config' binaries are used by build +processes to portably retrieve linker and compiler flags for a given library. +On Debian and Ubuntu, these binaries are often provided by the '-dev' packages. +In our case, it is 'libpcre3-dev'. + + $ sudo apt-get install libpcre3-dev + +'./configure' now runs without any issue. We can then build and install Apache. + +=== Problem 3: Need of restarting the web server === + +During the configuration of the HTTP authentication, we have to restart the web +server each time we make a single modification because 'httpd.conf' is read at +startup. It becomes very cumbersome when we are not familiar with the syntax on +the configuration file. + +==== Resolution ==== + +Apache provides us a way to use configuration files that are read on the fly. +We often refer to these files as '.htaccess'. In our case, we can configure the +authentication on the fly by replacing in 'httpd.conf' + + AllowOverride None + +by + + AllowOverride AuthConfig + +and restarting the web server. This way, we can write our configuration +directives 'htdocs/private/.htaccess' and test them without reloading Apache. + +=== Problem 4: Web Browsers keep the authentication details === + +Most web browsers, until they are restarted, save your credentials whenever you +successfully pass HTTP authentication so that you do not need to provide them +again when you reload the same page. It is very annoying when we are testing +our HTTP authentication because we need to restart our browser after each +successful attempt. + +==== Resolution ==== + +Instead of using a web browser to test our authentication, we can use 'curl' +which is a tool capable of executing a HTTP request, print the answer and quit +without saving the credentials. + +For that, we first have to install it if it is not already present: + + $ sudo apt-get install curl + +Then we can perform queries to our web server (the '-u' option allows to provide +a 'user:password' pair). + +Only interesting excerpts of the output is shown below + +.Failing to access '/private' without providing user/password: +========== + + $ curl http://csvm2C4E.kent.ac.uk/private/ + > <title>401 Unauthorized</title> + +========== + +.Failing to access '/private' by providing a wrong password: +========== + + $ curl http://csvm2C4E.kent.ac.uk/private/ -u admin:wrong_pass + > <title>401 Unauthorized</title> + +========= + +.Successing to access '/private' by providing both a good username and password +========= + + $ curl http://csvm2C4E.kent.ac.uk/private/ -u admin:good_pass + > This content is private. If you can read this message, it means that you have successfully passed HTTP authentication. + +========= + |