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Hack Mac OS X With Installer Packages
nezmar writes, "MacGeekery has a short but insightful piece with examples on how to use a malformed Installer package (.pkg) on Mac OS X to 'insert user accounts with administrator rights and change root-owned system configuration or binary files without prompting the vast majority of Mac OS X users for a password of any kind.'" The article notes that this issue was brought up on the Apple Discussion Boards 6 weeks back and that it was noted there as a duplicate / known issue. It also gives as an example the installation of Parallels, the popular virtualization software, which uses the described technique, but not for nefarious purposes.
At the very least, until this is fixed, this is yet another reminder not to install things without knowing what they are.
i run as a admin account and it still asks me to use my password to gain access even the program they listed it asked for my password to be entered to install. so it still is all good for me... i dont install things that i dont know what they are in the first place so those kiddies trying to hack on a mac will have problems downloading their haxzor programs cause it will crash their mac and allow some one to access it no big. just one less user in the world that cant learn how to get into ppls computers oh well
(yes i know i suck at spelling fell free to correct my grammar and/or spellin i dont care, im still not going to change
I knew it was weird when I installed Parallels a few months ago and it added several kernel extensions without a password prompt. This is a serious design flaw, and yet another reason for developers and users to avoid installer packages unless absolutely necessary.
How to solve most of our problems: 1.Lots of nuclear plants. 2.Cure aging.
You still have to install the package as an admin user. Lots of tools on Linux create admin user accounts without prompting for a password when run as root. The Debian Advanced Package Tool (APT), in fact, is one of them. It's perfectly possible to create a .deb package that sets up admin user accounts without prompting, as long as you are running as root. Does that mean you can hack Debian or Ubuntu with .deb packages?
My blog
So, when you're logged in as admin, and you install a package, that package can add whatever is in that package. Isn't that how it is supposed to work?
I'm not seeing the problem here. Am I missing something?
1. If you're sitting at the box, you might be able to 0wnz0r it. Same as for Linux, BSD, and Windows.
2. Regular folk should only install software from reasonably trusted sources.
I would assume that second point would be clear, given 10 years of watching Windows users open every last attachment that arrives in their inbox, while we sit at our Macs and laugh, but something tells me, probably not.
ZOMG I WOULD LOVE TO KNOW ABOUT YOUR FEELINGS ON MACINTOSH VERSUS WINDOWS, VI VERSUS EMACS, AND HOW YOU'RE NOT A DORK
It is hard to get most Mac users to not use an admin account, because if you're the only user it will be admin by default.
I've tried to explain to other Mac users that running as an admin by default is bad, and they always come back with "but you always get a pop-up asking for your username and password anyway, so you always know something is up". Unix-heads know this is wrong, but Mac users as a whole are as uninformed as your average Windows user.
The silly thing is OS X makes it absurdly easy to run as a non-admin. Just create a second account, make it an administrator, and then remove that privilege from your own account! If some task needs admin privileges, OS X will automatically prompt you for an admin account login - you don't even need to think about it beforehand (unlike XP's less-than-perfect "Run as..." solution). If an application tries to do something admin-y without asking you to authenticate as an admin, it will fail.
The only time this is ever a hassle is if you're installing one of a handful of software packages that doesn't use the OS X security framework. Adobe is the most egregious offender in this regard - they even require that the first time you launch a number of their programs (right after install in other words), it has to be done as an administrator. There's no good reason for them to do this, but it's part of their "We can't stop the pirates, but we can darn well make it a pain for law-abiding customers" initiative.
#DeleteChrome
from TFA:
Read my previous guide to securing Mac OS X and do not run as an admin user for daily activities.
Moreover, if you must run as the administrator, do not install packages from non-reputable sources without cracking open the package
Well, thank you, Captain Obvious!
One of the great features of the original MacOS was that it didn't have "installation". You put an application somewhere, the Finder found it, and you could launch it. If you wanted to delete it, you deleted it, and it disappeared. Maybe once in a while you had to rebuild the desktop to update the derived info that made this work.
But now, Apple has "installation", where install programs put stuff all over the place, and maybe change the state of the system. Just like Windows. Big step backwards.
On almost any system today, including Linux, OpenBSD, OS X, etc, software has far too much power. Even if I'm not logged in as an admin user, I could download an application, run it, have it trash my user folder, add some things to my .profile, etc. The truth is that the current 'security' on just about every system out there is a joke if you consider intentionally running a (secretly) malicious application a security problem. I absolutely do, but in the grand scheme of things, if Installer asks for a password or not on OS X to do things as root is not much of a concern compared to the gaping holes already there. Should it be fixed? Yes. Is it a major problem? No.
#DeleteChrome
There's a great security T-shirt out there that carries the slogan "Once you're penetrated, you're ****ed" (except with the canonical 4LW instead of ****).
Once an attacker has gained the ability to run unrestricted code on your computer, they can cause you grief even if they have no ability to install applications, install kernel components, run as root or Administrator, or even access the network. Being able to prevent applications from gaining extra privileges is good, at least it makes the cleanup easier, and possibly limits exposure to one account (though anyone who had an account on a shared timesharing system in college knows that's not guaranteed). But for most people, that account has everything they care about on the computer anyway, so once they're penetrated they're ****ed.
Apple needs to make the following changes to reduce the probability of penetration here.
1. Don't treat files (like, say, installers) as "safe". Treat applications that operate on files as "safe" or "unsafe", with "safe" limited to applications that are designed to deal with untrusted files.
2. INSTALLERS AREN'T DESIGNED TO DEAL WITH UNTRUSTED FILES. Don't run an installer automatically.
3. The user is allowed to shoot himself in the foot, but he has to actually pick up the gun and aim it aware that it might go off. It doesn't go in the bathroom cabinet with the hair dryer.
Don't mix untrusted and trusted files by default... downloads go in a "Downloads" folder, not on the desktop. Don't automatically install downloaded files, let the user request that. Don't run helper applications that are selected for the Finder or Windows Explorer, keep a separate list of helpers for web browsers and mail software...
PS: Mozilla folks: the same issue applies to XPI. You've got a big red tag on XPI installer saying 'THIS IS A GUN', but you're still leaving it in the bathroom cabinet next to the hair dryer. Cut that out.
I've known about this hole for about a year (yes I reported it to apple). The solution, which I use myself, is very simple. Do not run as sudo. I have two accouint. my everyday account and my sudo-user account. If you always run the installer as normal users then it will be forced to ask for a sudo-account name and password any time it needs to escalate privledges. There that's the fix.
If you always run as a sudo user then you are exposed to this hole. It's not techincally a hole, but most people would consider it an unexpected behaviour. Most people figure that if they don't give the installer their password then it can't be installing anything priveldged. Wrong, it is possible. But you were installing so....you sort of got what you asked for, but obviously it's ripe for a trojan.
The fix I give above simply forces the expected behaviour. If something wants to modify privledged files then it has to ask.
Now here's the nice thing. Unlike linux and windows, it is a perfectly pleasant experience for a poweruser to run as anormal user on a mac. I'd die if I had to have this dual account system on linux, since not having super user privs is a pain. KDE and GNOME try to help you with some operation, but it's so inconsisten you cant make it work well.
But on mac's it's nearly seemless. Anytime you need to authorize it pops up a window asking for a sudo account name. It's ubiquitous and there's virtually no time you need to be logged in as sudo-user. For extensive scrirpted or CLI coperations the terminal suffices to su to the sudo user. Now about once or twice a year, I find some situation where it is simpler to be in a GUI desktop as the sudo user. (one of those is fink-commander) For that there's fast user switching which lets me flip over to a logged in sudo GUI account instantly.
It's painless.
Some drink at the fountain of knowledge. Others just gargle.
Admin user in OS X are regular users on the admin group. The default setup creates an admin user. Installer.app allows PKGs run by admin TO RUN AS ROOT AND WRITE ON ROOT:WHEEL OWNED FILES WITHOUT A PASSWORD PROMPT. It's more-or-less OK for admins to write to /Applications. It's not to change /etc/sudoers or similar nefarious things without a prompt.
I'm going to reply to my own post because reading other comments I see that people don't grasp why this is an unexpected behaviour on a mac. It's a fairly normal behaviour on linux and Windows.
/bin and maybe overwrite somethings in /lib.
On a mac, it's normally possible to install an application without requiring any super user privledges. On linux and Windows it's frequently impossible or at least quite hard (on linux you often have to fiddle with the make configuration, and it results normally in a crippled application.
Here's one example. On a windows computer when you install something it has to have some way to get it's hooks into the OS. This might be as simple as notifying the OS of what extension/suffixes it can open or what services or filters it provides to other applications. This is done through the registry. And you need to be root to modify the registry. So you can't really install anything properly without giving your application the ability to write to the registry.
And since there's no selective privledges that would say "well I trust you to only modify this part of the registry and no where else nor any other file, you basically pull your pants down around your ankles, close your eyes and pray there is no unsolicited finger up the butt every time you install. Linux is simmilar, since it propably wants to shove stuff in
On a mac, applications don't do that. Normally an entire application lives in a single folder with no stuff placed anywhere else. SO how does the application provide services? Well what happens is that the operating system will interorogate the Application when it is installed or when you boot or launch it the first time. Inside the application is a standard XML file info.plist that declares all sorts of things the OS might want to know about the application. And then the OS relays this to the other applications as serices that are available. This is how for example, the OS knows what applications can open what kind of documents.
As a result, there is no need to unbuckle your jeans and grab your ankles when you do an install in most cases. And it's also easy to undo an application since the number of places it touches (usually just the application's folder and the library/preferences)
Now I just said in most cases. Some applications do need privledges since they are going to make strong modifications. THis might be installing a start-up item, for example, or things that make intimate hardare interface modifications And for those when you run the installer script you naturally expect it to ask you for your password so it can escalate it's privs.
And there is the problem. It turns out that the installer application on a mac, is a an application that can retain root privs after the first time you grant them (like says SETUID). To me this would seem unneccessary, but it does. And it turns out that if you are a sudo users, and if you have ever granted the installer elevated privs, then when it goes to install an application the requires elevated priv, it does not have to ask you for them! Now it also turns out that in most cases the applicaitons that are being installed can't know if a sudo user or a normal user is installing them so they automatically ask for the password. But they don't have to if you are sudo.
So the fix is not to install as a sudo user. Then the installer can't get the elevated privs be default. And so the application is forced to ask for them if it needs them.
Thus when your "make-a-smiley" application you got from gatorware asks for root during the install you have a chance to rethink if this might be a trojan.
Thus the behaviour of the installer that blows past the authentication check is bothersome to mac users even though they are doing an install. On linux and windows doing an install normally is always done at root privs so the peril is always there.
Some drink at the fountain of knowledge. Others just gargle.
Or you can boot from the install CD and just reset the password from there. Or boot from another OS X drive and change things from there. Or open the machine and do any of several different things.
If you can boot into single user mode, the machine is toast anyway. The best thing to do is to install Open Firmware Password to keep people from booting into single user mode or booting from another drive without the admin password, and then physically lock the machine so someone can't open it.
Albuquerque PC
You can't intercept it without modifying the OS kernel. And if you've done that you already own the machine. ctrl-alt-delete is a very low level signal. This has been around since NT for login, it's nothing new. On linux you can customise what the combo does by modifying the inittab file.
Good thing I'm using Windows.
w00t