TweetFollow Us on Twitter

Mac In The Shell: Plumbing the Depths

Volume Number: 23 (2007)
Issue Number: 08
Column Tag: Mac In The Shell

Mac In The Shell: Plumbing the Depths

Finding hidden gems in application bundles

by Edward Marczak

Introduction

With the advent of OS X, most Mac developers were introduced to the concept of bundles. More properly divided into bundles or packages, they both refer to a file-system directory that groups related resources together. This is true for frameworks (bundles: transparent structures that a user can easily access the contents of), applications (a package: an opaque bundle that requires work on the part of the user to open; contents are not easily modified), kernel extensions (another package), certain document types (check out Pages and Keynote, for example) and others. A bundle follows a very specific file layout, meaning, you'll know where to go find the goods. Follow along for a tour, and let's uncover some hidden apps.

Inside a Bundle

Those of us working with the Macintosh for a long enough period of time remember ResEdit, the resource format of OS 9, and all of the types we could store in the resource fork of a file. While OS X recognizes and respects the traditional dual-fork file, its format is deprecated, being replaced by the bundle. The purpose of a bundle is to keep the resources of an application, plug-in or framework in one place. This makes the contents easy to locate and easy to move without damage. What can go into a bundle? Well, technically anything, but you'll typically find the following types of data stored there:

Sounds

Images

Private libraries

String resources

Executable code

Naturally, it's the latter that interests us in this article.

Typically, to launch an application from a shell, you'd use the open command, like so:

open /Applications/TextEdit.app

This will always run the application in the context of the user, even if launched from a root shell, as shown in figure 1:


Figure 1 – TextEdit running as a standard user.

Of course, there are times where you may want (or need) an app to be running with some elevated privileges. How can we achieve this? Time to go digging!

A Direct Launch

As mentioned, a bundle conforms to a specific layout. Listing 1 shows this hierarchy using TextEdit as an example.

Listing 1 – TextEdit.app as bundle

TextEdit.app/
Contents/
Info.plist
MacOS/
TextEdit
PkgInfo
Resources/
DocumentWindows.nib
...
zh_TW.lproj
version.plist

The first item in all modern application bundles is the Contents folder. It is under this folder that all other objects reside. Within the Contents folder, you'll find an Info.plist file that tells the Finder many things about this bundle, including the bundle name, version, signature, applicable data types and more. You'll also find a Resources subdirectory, typically containing the images, sounds, movies and other resources used by the application. The application's executable itself resides in the MacOS subdirectory. If you are to look in there now, you'll find the TextEdit application. You can launch the application directly from here.

Gain a root shell using your preferred method, and launch the TextEdit application directly – not using open. Like this:

# /Applications/Textedit.app/Contents/MacOS/TextEdit

Now let's have a look in Activity Monitor, and you'll see that it's running with root privileges.


Figure 2 – TextEdit running with root privileges

Of course, the real point of this is not so much running with root, but the fact that you can access these binaries from the shell in some meaningful way.

Where's the Plunger?

Well, launching TextEdit is nice and all, but, not extremely practical. I'd like to continue with two very real-world examples that have made a difference in my daily work. While every GUI application will have its "true" binary buried in the application package, it may also have any number of helper-apps or other binaries that the app relies on. These are typically found in the Resources directory of the bundle. The easiest way to find executables in a bundle would be, in a shell, to change into the bundle directory and use this handy find command:

find . -type f -perm -100

This will allow you to quickly scour Application and Framework bundles. For instance:

$ cd /System/Library/CoreServices/RemoteManagement/ARDAgent.app/
$ find . -type f -perm -100
./Contents/MacOS/ARDAgent
./Contents/Resources/ARDPref.prefPane/Contents/MacOS/ARDPref
./Contents/Resources/ARDPref.prefPane/Contents/Resources/prefwritesettings
./Contents/Resources/kickstart
./Contents/Resources/RemoteDesktopAgent
./Contents/Support/ARDForcedViewer.app/Contents/MacOS/ARDForcedViewer
./Contents/Support/ARDHelper
./Contents/Support/build_hd_index
./Contents/Support/networksetup-panther
./Contents/Support/networksetup-tiger
./Contents/Support/Remote Desktop Message.app/Contents/MacOS/Remote Desktop Message
./Contents/Support/sysinfocachegen
./Contents/Support/systemsetup-panther
./Contents/Support/systemsetup-tiger

That's some wonderfully revealing information!

Secure Copy

The first really useful binary comes from the MacFUSE project. If you've installed MacFUSE core and the pre-compiled ssh filesystem, run our find command in the sshfs.app bundle. (If you haven't installed this, you should! It's an incredible resource. Find out more at http://code.google.com/p/macfuse/). Out of all the things we're returned, this turns out to be what we're looking for:

./Contents/Resources/sshfs-static

The sshfs-static binary lets us mount ssh file systems via a shell command rather than using the GUI app to do so. What's this good for? Automation, of course! In fact, you can use it to mount a remote ssh file system proactively, or in response to just about any event.

The easy thing to imagine is a nightly file copy. Mount the file system first, then, use ditto, rsync, or your preferred file moving method, and then unmount (using the standard umount command as, under OS X, there is no FUSE-specific unmounting needed). Better yet, though, think about a launchd job that watches a particular folder and perhaps copies files to a remote location as they show up in a source folder. Hmmmmmmm. So, how can we use this thing?

One way to make your life easier would be to symlink the sshfs-static binary to some appropriate location in your path. I'm going to run it straight from the application package, however, so for these examples, you'll need to change directly into the sshfs.app/Contents/Resources directory.

First, create a mount point for the file system. Then run the sshfs-static app and supply the following parameters:

user@hostname:/path/to/directory
mountpoint
-oreconnect,volname=name appearing in the Finder

The "reconnect" option, supplied with the -o switch isn't necessary, but does make things smoother if there's a network interruption and you're disconnected.

Since this all rides on top of ssh, ssh keys are respected. So, if you've generated some password-less keys, just like ssh, you won't be prompted for a password. Let's see this in action. First, I created /tmp/ssh as a mount point. Then, I used sshfs-static to mount a remote system:

$ ./sshfs-static marczak@www.example.com:/ /tmp/ssh -oreconnect,volname=wsweb
kextload: /System/Library/Filesystems/fusefs.fs/Support/fusefs.kext loaded successfully

...and let's take a look at it with mount:

$ mount
/dev/disk0s2 on / (local, journaled)
[snip]
sshfs#marczak@www.example.com:/ on /private/tmp/ssh (nodev, nosuid, synchronous, mounted by marczak)

Figure 3 shows the result of this in my Finder sidebar.


Figure 3: An ssh file system ("wsweb") as seen in the Finder

Very, very, very cool.

Network Probing

While 'black-hat' tools such as nmap sometimes get a bad rap, the fact is that tools like this are also perfect for system administrators when troubleshooting network issues. "Can I reach that port?" and "Is the target port open and responding?" are two of the most frequently asked questions when troubleshooting issues and planning network configurations. While I load nmap on my machine, I often find myself remotely accessing someone in need of assistance because his or her e-mail app "won't work" (residential ISPs typically block port 25) or iChat won't work in some manner (misconfigured/tightly restricted firewalls sometimes will block AIM or Google Talk/Jabber). It would, of course, be a chore and not very friendly to go load nmap and other tools onto someone else's system at that time. Is there a substitute built in to OS X?

Network Utility.app to the rescue! Huh?!? You expected a shell utility, right? Well, there's one hidden in the very graphical Network Utility.app that's found in your Utilities folder. Let's run our find command:

$ cd /Applications/Utilities/Network\ Utility.app/
$ find . -type f -perm -100
./Contents/MacOS/Network Utility
./Contents/Resources/stroke

Of course, we knew about MacOS/Network Utility, but Resources/stroke looks interesting! Nicely enough, the developer that wrote stroke was also kind enough to include a usage statement if you run it without parameters:

$ ./stroke 
2007-06-22 08:41:13.136 stroke[2113] stroke address startPort endPort
Let's see it in action:
./stroke 192.168.100.12 20 500
Port Scanning host: 192.168.100.12
         Open TCP Port:         22       pcanywherestat
         Open TCP Port:         25
         Open TCP Port:         53
         Open TCP Port:         80
         Open TCP Port:         106
         Open TCP Port:         110
         Open TCP Port:         119
         Open TCP Port:         139
         Open TCP Port:         143
         Open TCP Port:         311
         Open TCP Port:         389
         Open TCP Port:         427
         Open TCP Port:         443
         Open TCP Port:         445
         Open TCP Port:         465

Well, that's another useful tool that was buried, waiting for discovery. (Bonus points if you recognize the OS that I scanned).

Conclusion

The examples given here really only scratch the surface. There are plenty more hidden gems to be discovered. Take a look in your favorite applications. Dig in and see what you find! You will need to go hunt these utilities and helpers down yourself as they won't be in your shell's path.

Media of the month: Lost Season 1. OK, call me cheesy, but I really dig the show and am surprised at how many people have never given it a chance. Well, Summer is here and it's a great time to rent the DVDs and watch them at your own pace. If you're in the Southern Hemisphere, it's Winter....and what a great time to get under a blanket on the couch, sip some tea and watch a show...especially one that takes place on a tropical island! Enjoy.

WWDC 2007 has come and gone now, and got to reinforce the new concepts in Leopard. I hope everyone who went enjoyed the show, and will start practicing with the new tools and APIs...and have new tools, utilities and techniques ready for when Leopard ships. I've been plumbing the depths of the beta from the show, and have been pleasantly surprised.

Until next month, keep exploring!

Resources

Apple, Inc. "Bundle Programming Guide"


Ed Marczak gets dressed in the morning, drinks tea and enjoys breathing. All of this comes in handy in his role as Executive Editor of MacTech Magazine, or when running his consulting company Radiotope. They're also good features when around children. Why? http://www.radiotope.com/writing

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Alfred 3.2.1 - Quick launcher for apps a...
Alfred is an award-winning productivity application for OS X. Alfred saves you time when you search for files online or on your Mac. Be more productive with hotkeys, keywords, and file actions at... Read more
OmniPlan 3.6 - Robust project management...
With OmniPlan, you can create logical, manageable project plans with Gantt charts, schedules, summaries, milestones, and critical paths. Break down the tasks needed to make your project a success,... Read more
Backblaze 4.2.0.990 - Online backup serv...
Backblaze is an online backup service designed from the ground-up for the Mac. With unlimited storage available for $5 per month, as well as a free 15-day trial, peace of mind is within reach with... Read more
AppDelete 4.3.1 - $7.99
AppDelete is an uninstaller that will remove not only applications but also widgets, preference panes, plugins, and screensavers along with their associated files. Without AppDelete these associated... Read more
Apple GarageBand 10.1.4 - Complete recor...
The new GarageBand is a whole music creation studio right inside your Mac -- complete with keyboard, synths, orchestral and percussion instruments, presets for guitar and voice, an entirely... Read more
Adobe Lightroom 6.8 - Import, develop, a...
Adobe Lightroom is available as part of Adobe Creative Cloud for as little as $9.99/month bundled with Photoshop CC as part of the photography package. Lightroom 6 is also available for purchase as a... Read more
iMazing 2.1.3 - Complete iOS device mana...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more
Little Snitch 3.7.1 - Alerts you about o...
Little Snitch gives you control over your private outgoing data. Track background activity As soon as your computer connects to the Internet, applications often have permission to send any... Read more
OmniPlan Pro 3.6 - Professional-grade pr...
With OmniPlan Pro, you can create logical, manageable project plans with Gantt charts, schedules, summaries, milestones, and critical paths. Break down the tasks needed to make your project a success... Read more
Apple GarageBand 10.1.4 - Complete recor...
The new GarageBand is a whole music creation studio right inside your Mac -- complete with keyboard, synths, orchestral and percussion instruments, presets for guitar and voice, an entirely... Read more

Latest Forum Discussions

See All

Galaxy on Fire 3 and four other fantasti...
Galaxy on Fire 3 - Manticore brings the series back for another round of daring space battles. It's familiar territory for folks who are familiar with the franchise. If you've beaten the game and are looking to broaden your horizons, might we... | Read more »
The best apps for your holiday gift exch...
What's that, you say? You still haven't started your holiday shopping? Don't beat yourself up over it -- a lot of people have been putting it off, too. It's become easier and easier to procrastinate gift shopping thanks to a number of apps that... | Read more »
Toca Hair Salon 3 (Education)
Toca Hair Salon 3 1.0 Device: iOS Universal Category: Education Price: $2.99, Version: 1.0 (iTunes) Description: | Read more »
Winter comes to Darkwood as Seekers Note...
MyTona, based in the chilly Siberian city of Yakutsk, has brought a little festive fun to its hidden object game Seekers Notes: Hidden Mystery. The Christmas update introduces some new inhabitants to players, and with them a chance to win plenty of... | Read more »
Bully: Anniversary Edition (Games)
Bully: Anniversary Edition 1.03.1 Device: iOS Universal Category: Games Price: $6.99, Version: 1.03.1 (iTunes) Description: *** PLEASE NOTE: This game is officially supported on the following devices: iPhone 5 and newer, iPod Touch... | Read more »
PINE GROVE (Games)
PINE GROVE 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: A pine grove where there are no footsteps of people due to continuous missing cases. The case is still unsolved and nothing has... | Read more »
Niantic teases new Pokémon announcement...
After rumors started swirling yesterday, it turns out there is an official Pokémon GO update on its way. We’ll find out what’s in store for us and our growing Pokémon collections tomorrow during the Starbucks event, but Niantic will be revealing... | Read more »
3 reasons why Nicki Minaj: The Empire is...
Nicki Minaj is as business-savvy as she is musically talented and she’s proved that by launching her own game. Designed by Glu, purveyors of other fine celebrity games like cult favorite Kim Kardashian: Hollywood, Nicki Minaj: The Empire launched... | Read more »
Clash of Clans is getting its own animat...
Riding on its unending wave of fame and success, Clash of Clans is getting an animated web series based on its Clash-A-Rama animated shorts.As opposed to the current shorts' 60 second run time, the new and improved Clash-A-Rama will be comprised of... | Read more »
Leaks hint at Pokémon GO and Starbucks C...
Leaked images from a hub for Starbucks employees suggests that a big Pokémon GO event with the coffee giant could begin this very week. The images appeared on Reddit and hint at some exciting new things to come for Niantic's smash hit game. | Read more »

Price Scanner via MacPrices.net

12-inch Retina MacBooks, Apple refurbished, n...
Apple has restocked a full line of Certified Refurbished 2016 12″ Retina MacBooks, now available for $200-$260 off MSRP. Refurbished 2015 models are available starting at $929. Apple will include a... Read more
Holiday sale: 12-inch Retina MacBook for $100...
B&H has 12″ Retina MacBooks on sale for $100 off MSRP as part of their Holiday sale. Shipping is free, and B&H charges NY sales tax only: - 12″ 1.1GHz Space Gray Retina MacBook: $1199 $100... Read more
Apple refurbished 13-inch MacBook Airs availa...
Apple has Certified Refurbished 13″ MacBook Airs available starting at $849. An Apple one-year warranty is included with each MacBook, and shipping is free: - 13″ 1.6GHz/8GB/128GB MacBook Air: $849 $... Read more
Apple refurbished iMacs available for up to $...
Apple has Certified Refurbished 2015 21″ & 27″ iMacs available for up to $350 off MSRP. Apple’s one-year warranty is standard, and shipping is free. The following models are available: - 21″ 3.... Read more
Apple’s Education discount saves up to $300 o...
Purchase a new Mac or iPad using Apple’s Education Store and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free: -... Read more
Back in stock: Apple refurbished Mac minis fr...
Apple has Certified Refurbished Mac minis available starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: - 1.4GHz Mac mini: $419 $80 off MSRP - 2.6GHz Mac... Read more
Twenty-Five Years Of Apple Laptops – A person...
Among many other things, the often tumultuous 16th year of the new century marked the 25th anniversary of Apple laptop computers, not counting the optimistically named 16-pound Mac Portable of 1989.... Read more
Landlordy iOS App Adds Support For Appliances...
Riga, Latvia based E-protect SIA is releasing major update (version 1.8) to its Landlordy app for managing rental business financials on the go. Landlordy is iPhone and iPad app designed for self-... Read more
Holiday sale, Apple iMacs for up to $200 off...
B&H Photo has 21″ and 27″ Apple iMacs on sale for up to $200 off MSRP including free shipping plus NY sales tax only: - 27″ 3.3GHz iMac 5K: $2099 $200 off MSRP - 27″ 3.2GHz/1TB Fusion iMac 5K: $... Read more
Holiday sale: Mac minis for $50 to $100 off M...
B&H Photo has Mac minis on sale for up to $100 off MSRP free shipping plus NY sales tax only: - 1.4GHz Mac mini: $449 $50 off MSRP - 2.6GHz Mac mini: $629 $70 off MSRP - 2.8GHz Mac mini: $899 $... Read more

Jobs Board

*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions- Trumbul...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions- Philade...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions- San Ant...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Products Tester Needed - Apple (Unit...
…we therefore look forward to put out products to quality test for durability. Apple leads the digital music revolution with its iPods and iTunes online store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.