Apache :: Tutorial for a HTML PHP Solution that Calls Another Program?

redapplesonly · Joined: 24 Feb 2022 Posts: 3

Hello all,

I have a general question: Can anyone recommend a tutorial for a HTTP/PHP website that calls another program when the user clicks a button?

Some details: I have an Ubuntu 16.04 server, on which runs some custom Java code that I've written for my colleagues. (There are 5 of us.) My colleagues want to use the code, but don't want to go through the hassle of running the code, which involves logging in/su'ing to an account/editing a file/submitting the file to the code/watching for output/etc. Its a pain.

A solution I've like to give them is a simple webpage, hosted on the Ubuntu. The page has a button; they click the button, and everything is automated.

I've installed Apache2 2.4.41 for this purpose. And I have a primitive website that has the button. But I need a PHP script that activates when that button is pushed. The script would have to run my Java code, then post the text-based output.

A wrinkle here is that I'm guessing the PHP script would run as user 'www-data'. But my Java code was installed for user 'pete'. So the PHP script has to be able to do a

tangent · Moderator Joined: 16 Aug 2020 Posts: 312 Location: UK

There are any number of methods to solve this problem (your favourite search engine is your friend), depending on how refined and secure a solution you want to create.

However, the simplest option I can think of is to start with a basic HTML form statement, and a CGI script. You could then enhance things with PHP rather than CGI should you want to.

You're running on Ubuntu, so enabling basic CGI in Apache is straightforward. Equally, you can configure the sudoers file so the Apache user www-data can run your Java program as pete (see below).

Code:

# a2enmod cgid
# apache2ctl restart

b) Create a test index.html file (say /var/www/html/test/index.html) with the following, e.g.

Code:

c) Create a suitable CGI test script, e.g.

Code:

# cat > /usr/lib/cgi-bin/test <<'EOF'
#!/bin/sh

echo "Content-Type: text/html\n\n";

echo "<html> <body>\n";
/usr/bin/sudo -u pete /home/pete/runJavaProgram.exe | sed -e 's/$/<br>/'
echo "</body> </html>\n";
EOF

Note the sudo command to run your Java program as pete. Also the use of sed to insert line breaks into the output content.

d) Make the script executable

Code:

# chmod 755 /usr/lib/cgi-bin/test

e) As root, edit the sudoers extras file (/etc/sudoers.d/extras), and add the following line to allow the Apache www-data account to run your Java program as pete.

Code:

www-data ALL=(pete) NOPASSWD: /home/pete/runJavaProgram.exe

f) Point a browser to your above test index page, e.g. http://localhost/test, and click the "Click me" button.

The CGI script should run and you'll hopefully see the output from your Java program.

This solution should be adequate for an internal network.

redapplesonly · Joined: 24 Feb 2022 Posts: 3

@tangent

Thanks, Tangent! I've studied your notes, and I'm eager to try your solution. Unfortunately, I need to do other work stuff at the moment. But I can clear my schedule tomorrow to work on this. Thank you so much! Smile

redapplesonly · Joined: 24 Feb 2022 Posts: 3

@tangent

So I implemented your solution this morning, but I'm afraid something is still amiss. May I review my configuration? I did all of the following:

(A) Enabled CGI and restarted Apache

(B) Set up a simple index.html page:

tangent · Moderator Joined: 16 Aug 2020 Posts: 312 Location: UK

As you say the clue to your problem is in the Apache error log, showing that sudo is requesting a password. Believe the problem is your entry in the sudoers file, which needs the NOPASSWRD tag adding to the www-data entry. There is no terminal associated with the Apache process in which the password could be entered, and moreover, the www-data account isn't interactive and equally has no password.

As listed above, suggest you try this line instead (with testScript.sh rather than runJavaProgram.exe)