Category Archives: Apple & Macs

We've been exploring remote access and remote management options for the Mac mini and other Macs running Mac OS X Panther or Tiger for several months, and today we'll turn our attention to another solution that is ideally suited for those with multiple Macs at different locations. Every copy of Mac OS X ships with client and server versions of the Apple File Protocol (AFP) over TCP/IP. Enabling the server is a one-click operation. Choose System Preferences->Sharing and put a check mark beside Personal File Sharing. Assuming you have enabled the Mac's built-in firewall (which we always recommend), this automatically opens ports 548 and 427. If you have a hardware-based firewall (which we also recommend), you'll need to open port 548 and point it to the internal IP address of your Mac. If you have two Macs with Internet connections at different locations, you'll need to do the same thing on the other end. To connect to a remote Mac, you'll need to know its IP address or fully qualified domain name. Using a web browser on the remote Mac, you can obtain the IP address of your Mac by clicking on this link.

Once you enable Personal File Sharing and open the necessary ports in your firewalls, anyone can access and upload files to your Macs knowing nothing more than your IP address or fully-qualified domain name. Only those with actual user accounts can read and write files and execute programs on your remote Mac, and their access is restricted just as if they had logged in sitting at the desktop. The anonymous write access may or may not be what you had in mind. One very real risk of this design is that, given enough time, a malicious passer-by can flood your Mac with data and fill your entire hard disk with junk which will eventually crash the operating system since there will be no room for temporary files. If you couldn't already tell, this isn't our favorite Apple engineering design so here's how to fix it.

As delivered from Apple, every user's account has a Public folder with a Drop Box subfolder. The owner-user has read-write-execute privileges. The owner's group and everyone else have write and execute privileges to the Drop Box folder. This means strangers can upload files but can't see what's been uploaded. To adjust this so that strangers have no access privilegs, open a Terminal window and switch to root privileges: sudo su. Switch to the directory which houses user accounts: cd /Users. Display a directory listing for this folder: ls -all. Then repeat the steps below for every user account on your Mac substituting the name of each user's file folder for thisuser:

Make certain that the public directory listing in Step #2 begins with the following:

drwxr-x---

There should be three trailing hyphens following the "x" and these are the important part. Don't worry if the rest of the rights don't match. Continue repeating the steps above until you've done it for every user account on your Mac. Forgetting just one means someone can fill your disk with garbage!

Now that we've gotten the security housekeeping out of the way, we're ready to test your AFP access. This can be done from another Mac on your local area network or from a Mac elsewhere on the Internet. If you're trying it from your LAN, use the private IP address of the remote Mac (we'll call the Mac we're connecting to the AFP host or AFP server). If you're trying this from elsewhere on the Internet, use your AFP host's Internet IP address, the one you obtained in the first paragraph above. Now, click on your Desktop and press Command-K. For the server address, type afp://192.168.0.102 substituting your AFP host's IP address, of course. Click the Connect button to make the AFP connection, and assuming you got the IP address typed correctly you will see an AFP login window which looks similar to the one shown in the inset to the left. Notice the Guest and Registered User options. Now you know why we did what we did above to disable Guest access. Technically, strangers still can connect. They just can't get to anything or do any damage. To see how this works, try Guest access to our beach house Mac by going to this address: afp://windswept.dyndns.org.

For our purposes, you'll want to log in as a Registered User. So type your username and password just as you would sitting in front of your AFP Mac host. If you have Administrator rights, you'll be asked whether to mount your user directory or one of your mounted drives. Mounting the internal drive gives you access to everything on your Mac just as if you had logged in as the root user. You now can perform almost any task as if you were sitting in front of your remote Mac ... only slower. If you're using a modem, make that "painfully slower." If you have broadband connections at both ends of your AFP connection, you'll find AFP is perfectly acceptable for transferring files back and forth but probably not desirable for executing most applications, such as Word or iTunes. Another drawback of pure AFP is that data is sent in clear text and is unencrypted meaning all of the data including your account names and passwords are subject to compromise especially from a "Man in the Middle" attack. A good example would be a curious college geek managing the routers for your local Internet service provider.

That brings us to the second half of this article which is how to use an encrypted SSH tunnel to protect your AFP sessions. In one of many great articles on the subject O'Reilly put it this way:

A tunnel is a networking term with an appropriate name. It refers to a connection, usually encrypted, that connects two computers together across another, usually untrusted network. Picture a mountain of evil 3l33t d00dz sitting between your laptop and a server on your internal, protected network. You don't want to just throw your traffic really hard at the mountain and hope it gets there; you want to first form a protected tunnel from you to your machine, and then send the traffic through it.

Without getting into too much detail, what we want to do is set up an encrypted tunnel using Mac OS X's SSH tools, and then we'll pass all of our AFP traffic through that tunnel to keep the bad guys from reading its contents. Once we finish our AFP session, we'll shut down the tunnel until we need it again. For this to work reliably, you'll need to set up identical user accounts with identical passwords on both the remote host and client machines, and these accounts should have administrator privileges. A user with admin privileges need not be logged in on the remote host to establish the tunnel successfully. On the remote host, you'll need to enable Remote Login by checking the appropriate box in System Preferences->Sharing. This will enable Port 22 traffic on your Mac firewall; however, you also will need to adjust your hardware-based firewall to route port 22 traffic to the internal IP address of your Mac. Now log in to your client Mac using the same account name with admin privileges that you established on your remote Mac. Open a Terminal window and type: ssh 192.168.0.102 substituting the remote IP address of your remote Mac host. You'll be warned that this machine may not be who you think it is. Type Yes to proceed anyway. Type your admin password when prompted. Once the tunnel is established, you can shut it down by typing Exit. You now know how to establish an SSH tunnel and, once established, you can do anything on the remote Mac that you could do sitting in front of it with a Terminal window.

But we want to tunnel our AFP session through the SSH tunnel. That gets a little trickier, and we've created yet another code snippet to save you a semester's worth of work trying to figure it out yourself. Nothing in this script is original incidentally. It merely combines various suggestions I've scoured from around the 'Net to save you a bunch of time. So download afptunnel.txt to your browser by Control-Clicking on it and choosing to open it in a new tab or window. Press Command-A and then Command-C to copy the contents of the snippet to your clipboard. Now open a Terminal window and create a new file: pico afptunnel. Once the Pico editor opens, press Command-V to copy the contents of the clipboard into the editor. Now search for "windswept": Ctrl-W,windswept,enter. With the cursor positioned over the w in windswept, use Ctrl-D to delete windswept.dyndns.org. Now type the fully qualified domain name or IP address of your remote Mac AFP host but make certain the line ends with a semicolon with no blank spaces between the address and the semicolon. Now save the file: Ctrl-X,Y,enter. Change the file attributes to support script execution: chmod 770 afptunnel. Now try out the script to connect from your local machine to your remote Mac host through an SSH tunnel: ./afptunnel. Type Yes if asked whether to trust the host. Provide your admin password when prompted. When the tunnel is established and the AFP connection is made, log in to the remote host using your remote account created earlier. Heed the Terminal window warning and leave the window open until you end your AFP session by dismounting your AFP drive. Then click in the Terminal window and press the ENTER key to close down your SSH tunnel. You're now an expert on AFP and SSH. Now you can securely connect to your remote Mac from any other Mac on the planet!

Security Alert. Just a heads up that earlier this week Apple announced a security vulnerability in the AFP server for Mac OS X Tiger only. You can read all about it here. Before using AFP Server on a Tiger system with or without an SSH tunnel, you are well advised to download and install Security Update 2005-006 for Mac OS X 10.4.1.

Other Mac Projects and HOW-TO's. We tackle a new open source project for the Mac almost every week on Nerd Vittles. You can review the complete list at any time by going here.

Once you get a web site up and running on your Mac mini (or any other Mac running Mac OS X Panther or Tiger), you’ll probably get hooked and want to add additional web sites or domains. So today we’re going to give you a template that can be used to add additional sites to your heart’s content. In a previous article, we covered one approach to hosting multiple domains. In that scenario, we built separate web sites in the Sites folder for various user accounts on your Mac. Then using Omnis.com‘s DNS tools, we pointed different domains or subdomains to the appropriate web sites on your Mac using a Proxy (aka mod_proxy) record for the domain that looked like this (substituting your own IP address, of course):

That solution works; however, it forces you to log in as different users to manage the different web sites. Today’s approach assumes you want to manage multiple web sites from a single account on your Mac using the traditional web site folder heirarchy located at /Library/WebServer/Documents. Our site design for multiple web sites and multiple domains goes like this. We’ll create a websites folder below the /Library/WebServer/Documents folder. Then, for each new web site or domain, we’ll create a subfolder below the websites folder. We’ll leave the websites folder empty and adjust Apache to bar direct access to the contents of that folder. Then we’ll assign a TCP port for the new site and add the necessary code to support the new domain to the Apache config file, httpd.conf. Finally, we’ll point our domains to your Mac’s IP address using the proxy service of a domain registrar, restart Apache, and presto, you’ll be hosting multiple web sites from your Mac mini ISP-In-A-Box. One advantage of this design is that you still can remotely manage all of your web sites using a WebDAV client on almost any computer. We covered all of that here last week. We’re assuming you already have built your first web site using our Apache tutorials. If not, start here. Then go here and here. Then you’ll be ready to continue on with this tutorial. As with most of our articles, a degree in Rocket Science isn’t required, but you do have to use the Pico editor to make a few customizations to the Apache configuration files. For the Internet wizards reading this, you’re probably saying there’s an easier way to set up multiple web sites with Apache. Yes, there is. It just doesn’t seem to work in the Mac environment. If anyone comes up with a simpler method that works, do us all a favor and put it in a comment.

Creating the First Web Site. Let’s begin by creating the folder that will house all of our new web sites. Open a Terminal window and switch to root access with your admin password: sudo su. Now move to the main web site folder: cd /Library/WebServer/Documents. Create the new websites folder: mkdir websites. Move to the websites folder: cd websites. Now create a directory to house our first new web site: mkdir mysite. For additional web sites, you’ll simply create additional folders below the websites folder as we just did.

Modifying Apache to Support New Web Sites. Because of Apple’s configuration design, we’re going to configure our new web sites to use TCP ports in the eighties beginning with 81 rather than the default HTTP port, port 80. Remember not to use 82. We used that for our WebDAV server. So we’ll need to first edit httpd.conf in the /etc/httpd folder. Open a Terminal window and switch to root access: sudo su. Move to the Apache config directory: cd /etc/httpd. Make a duplicate of the httpd.conf file just in case something goes wrong: cp httpd.conf httpd.sav. Now carefully edit the Apache config file: pico httpd.conf. Switch back to your web browser and Ctrl-Click on the access.txt code snippet here and open it in a new tab or window in your web browser. Press Command-A then Command-C to copy the code snippet to your clipboard. Now switch back to your Terminal window and move to the bottom of the httpd.conf file by repeatedly pressing Ctrl-V. Copy the clipboard contents there by pressing Command-V.

Now let’s look at what we pasted. The first three lines tell Apache not to display a directory listing of the websites folder if someone accesses your web site by typing: http://yourwebsite.com/websites/. The Listen 81 line tells Apache to listen on this TCP port as well as port 80. The VirtualHost _default_:81 line identifies the port which will be used to access this web site. The DocumentRoot and Directory lines tell Apache where the data for this web site is stored on your server: /Library/WebServer/Documents/websites/mysite. The allow from all line gives everyone access to this web site. And Options +Indexes tells Apache to display a directory listing of this folder if there is no index.html or index.php startup file in the folder. If you want to hide the directory if there is no startup file, change the plus sign to a minus sign.

Now that you understand what the various lines in the config file do, let’s save the changes to httpd.conf: Ctrl-X,Y,enter. Now restart the Apache web server: apachectl restart.

Firewall Adjustments. Remember to add a new port authorization in your Mac firewall to support port 81. Go to SystemPreferences->Sharing->Firewall and click the New button. Choose Other for the PortName, specify the desired TCP port number (81), and name the service HTTP81 so you can remember what it does. Click OK to save your update. Also make the necessary adjustment to your hardware based firewall to authorize the new port and point it to the internal IP address of your Mac. If your hardware firewall uses port 81 for remote access, be sure to change it to another port.

Domain Registrar Adjustments. Finally, access your domain registrar’s web site (as previously noted, we recommend Omnis.com which supports proxy DNS entries) and, using the registrar’s DNS tools, add a proxy record to point your domain to the IP address and port 81 of your Mac web server: http://111.111.111.111:81 using your own IP address. You usually have to make two proxy record entries, one for @ and one for www if you want your web site accessible as either www.yourwebsite.com or yourwebsite.com. If you don’t know the IP address of your Mac web server, just access our IP site identifier using a web browser on your Mac web server, and it will tell you.

Adding Additional Web Sites or Domains. When you’re ready to add additonal web sites or domains to your web server, just follow these simple steps. Add a new folder in the /Library/WebServer/Documents/websites folder. Add an additional Listen and VirtualHost block to your access.conf config file for each domain address which will be used to access the new web site. Be sure to change the access port to port 83 or higher and the web site directory location in every line that you added. Remember to use a different TCP port for each new domain you add. Restart your Apache web server. Make the necessary additions to your Mac and hardware-based firewalls to support the new port. Then add the proxy DNS entry for your new domain using your domain registrar’s proxy DNS tools. For a sample of what we just did using the mysite.webify.us subdomain, click here. Yes, we eat our own dog food.