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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.
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.
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
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.
I believe you misunderstand. sudo is a command that takes a user listed in the sudoers file and gives them root priviledges. In a default OS X install, only admins are in the sudoers file. There are three levels of access in OS X: unpriviledged user, admin and root. Only admins may be promoted to root through sudo. If your password works for the installer, you are an admin.
It has been a nervous year, with people beginning to feel like Christian Scientists with appendicitis.
#DeleteChrome
I do not know any Mac users, so I really don't know whether they are as dumb as Windows users.
/.ers still come here to see the latest tech news and participate in or see in-depth discussion of these issues to enrich ourselves and others. The problem is there are too many smug people like yourself here not acutally lending anything to the actual discussions but instead just toss pointless insults around and generally trying spread to show how smug you are. It kind of lends itself to a Beavis and Butthead mentality where the lowest common denominator (you) end up distracting people from the actual discussion taking place. Now do I think this is a real issue? Not really and certainly not specifically for Apple (see my other post) but it is worth an educated discussion about the pros and cons and look at the options. Posts like yours just distract from the issues at hand I guess in some hope to get some cheap karma points by pointlessly slamming people when its completely irrelevant to the discussion while actually adding nothing.
Oh, sure! I'm certain you were expecting a bunch of well thought out replys discussing if Mac users and/or Windows users are stupid and really get to the bottom of this deep question. Its a textbook flame, deal with it. You were just tossing out insults in some sad attempt to make yourself feel superior.
Here's the thing, many of us
"reality has a well-known liberal bias" - Steven Colbert
I don't even think we're making a different point. My definition of admin is just more confusing I guess. You're indeed right that the default user is a user from the admin group, but my point is that even though the user might be an admin, he doesn't have root priviledges without giving a password first.
The problem is with the package management. What the article is saying is that package creator is allowed to set authorization for installation. They can choose either to authorize with Root privilege or with Admin priviledge. Installations that require Root privilege will prompt for password from a user even if the user is logged on as an Administrator. Admin privileged installation doesn't require a password if the user is Administrator. The danger is that some installations which should require Root priviledge (ones that deeply modify the OS) can be carried out with a passwordless Admin priviledge, so the Admin doesn't realize just how much modification is being made to the system.
A scenario would work like this:
Admin thinks he just installing a regular editor application. Package author specifies installation with Admin priviledge no authorization. Admin proceeds to install package but is unaware that package install program is silently adding system kernel extensions. Normally, this would require Root priviledges for system modifications, but doesn't because of this weakness in the installation api.
Uhh... have you even used Mac OS X? The vast majority of applications are distributed as "bundles," which are basically special directories that contain everything the program needs to run. You can put the bundle whereever you like, and execute it from there, though the OS provides an "Applications" folder to keep everything neat.
Frameworks, like Quicktime or SDL, work in a similar way, though they get dropped in the "Library/Frameworks" folder.
The only things that use the Installer are things that need to make fundamental changes to the system, such as kernel extensions, or programs that have to noodle with the main directory structure, like Fink. They usually provide an uninstall script as well. Granted, Apple's first party apps use the Installer, but they're more complex and integrated. The only program I've ever used that wasn't supplied as a bundle was Fink (basically a port of Debian's APT to make installing Unix applications easier).
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.
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.
Actually, a better solution for authentication from the OS is a secure attention sequence (SAS), e.g. CTRL+ALT+DELETE on Windows NT or CTRL+ALT+PAUSE on Linux. The OS supersedes any application's attempt to trap this key sequence and puts the display into a mode that only shows OS sanctioned secure dialog boxes. On Windows (and XP with the welcome screen off) this is the "Windows Security" screen. This way, if you always enter the SAS before entering your password, you know that only the OS is receiving it. It helps to build the habit when the OS always asks you for the SAS before entering passwords.
The new authorization dialog boxes in Vista are like this; this is the reason they take over the desktop. IIRC, you can hit CTRL+ALT+DELETE while one of these is up and you'll know its authentic because it'll stay there (if it weren't you'd switch to the "Windows Security" screen instead.)
Of course, these are useless if the OS is already compromised, but the whole idea is to keep it from getting that far.