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Skype Linux Reads Password and Firefox Profile
mrcgran writes "Users of Skype for Linux have just found out that it reads the files /etc/passwd, firefox profile, plugins, addons, etc, and many other unnecessary files in /etc. This fact was originally discovered by using AppArmor, but others have confirmed this fact using strace on versions 1.4.0.94 and 1.4.0.99. What is going on? This probably shows how important it is to use AppArmor in any closed-source application in Linux to restrict any undue access to your files."
This is why you should have shadow passwords, so that your encrypted password isn't stored in /etc/passwd.
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# Canmephians for a better Linux Kernel
$Stalag99{"URL"}="http://stalag99.net";
.. only closed source applications? I don't think most people read the entire sources of open source applications that they use.
Is a public file, as are virtually all the others in /etc.
What's it doing? Well, what libraries is it linked with? Perhaps it's converting your UID into a name among other things.
Deleted
Dunno about AppArmour, but there is no way in hell to distinguish between legitimate getpwnam, getpwuid, etc calls and reading the whole passwd file on a linux system using strace.
/etc/passwd you should not claim that it does something illegitimate.
Example:
strace on ls -laF immediately gives
open("/etc/passwd", O_RDONLY) = 4
Followed by quite a few reads out of it. So by the logic of the poster ls -laF is a horrible application doing horrible things to your system.
Unless you have read the source or single-stepped trhough the app with a debugger, examined the data and found that it does something nefarious like sending skype the whole of your
Baker's Law: Misery no longer loves company. Nowadays it insists on it
http://www.sigsegv.cx/
Second: Any modern Linux system will use a shadow password file, its been years since I've seen a system use a regular password file.
This sort of "evil" is very transparent. You can code a hidden buffer overflow/exploit/backdoor in such a way that it's not obvious (= instead of == for example, caught in the Linux kernel once). But how do you hide an access to say, /proc/interrupts? You need to spell out the filename, and there's got to be an open or fopen for it somewhere. Any attempt to encode the filename is going to be weird and suspicious. Plus, file parsing would be quite a bit than a single line of code, so it's hard not to notice something is being read, stored, etc.
Uh huh. Such a thing would be an outright admission of evildoing. Depending on what is being done it might be enough for a lawsuit, and definitely enough for mass publication all over the web to ruin the developer's name. Slashdot had a story on some Mac developer who claimed there was an anti-piracy check that'd delete the user's documents folder. Just the claim (which the developer says wasn't real and intended to scare people off) resulted in such outrage he's probably unemployable for years now.
No, anybody with any brains would deny any wrongdoing and claim a hacked server, or pretend that no mail is arriving at all.
But 99% of Linux software is delivered by the distribution, with the package maintainer often being completely unrelated to the developer. While it's not impossible for something weird to be going on, those distribution maintainers do things like patching the source and dealing with its bugs. You can bet that eg, the Debian maintainer of Firefox looked at the source.
That's a tricky one, but you can use a different compiler. Compile gcc with icc for instance. For OSS I think this approach is unlikely due to the frequence with which somebody decides "let's rewrite this part". It's easy to make a compiler that hiddenly changes some well known part of the source, but it's much harder to deal with a complete reorganization of it. To keep it up would need updates
He mentioned the libc calls already. Those calls will use whatever method is appropriate for obtaining user information. On a default installation, this will be reading /etc/passwd.
No, you DO NOT INSTALL ANYTHING APART FROM SYS AS A ROOT! You only give them privileges, open ports, etc.
Linux users are nowadays just as stupid as mainstream.
Furthermore skype will try to install the firefox extension if you want it to, so reading your firefox profile isn't "unnecessary" as the article title claims...
+5, Truth
Ok, if you're so clever, provide an example of code that reads a file without making it easy to tell what it's doing, while avoiding looking suspicious.
Don't change subject. The original post was about a developer releasing "evil" code, then turning somebody who finds it to their side. Now you're talking about people submitting patches with somethind hidden in them. Completely different scenarios.
Most OSS projects don't blindly accept patches. Certainly not the ones in widespread usage. You might sneak a buffer overflow in, but to sneak an outright trojan would be seriously challenging. The submitter's anonymity isn't a problem if source is being examined.
Stupidity exist everywhere of course, can't be eliminated 100%. But while for Linux users perhaps 1% of all software comes from unverified sources, for Windows users it's 99%. Just why exactly do you trust that say, Trillian isn't doing anything strange? Nobody but its developers really knows what's there.
Not all of it, but there are many distributions, which each look at different parts of the source. To sneak something in you'd need to be really sure that part won't get looked at by anybody, and that's hard. Developers watch mailing lists, talk to people who work on the project and use 'svn diff'.
First you build gcc with icc. This is icc_gcc.
Then you build another copy of gcc with gcc. This is gcc_gcc.
Now you have two gccs with different code generated by different compilers.
So now you take both of those, and build the gcc source with both icc_gcc and gcc_gcc. Both should generate the same code. If they don't, something's fishy.
You can easily this with more compilers and multiple versions.
Well, I still think it can't be defined that the OSS approach is superior. It's not impossible to sneak something in. But in doing so you must take a very high risk of being found out, and if somebody tracks that back to you, well, chances are you're going to have to look for a new carreer. People with a known record of coding nasty things aren't very liked in the software world.
Right. And that bit of code looks obviously harmless. You'd obviously scroll right by it if you saw it in some package's source, because there's absolutely no chance anything odd would be going on in a piece of code like that.
I mean seriously, that SCREAMS that there's something odd there.
Here's the same challenge for you as for the other poster: Write some code that accesses some file it shouldn't, and does something with the data in it (writing it to a socket say) in such a way that you can't tell what's it doing without looking really well at it, and it looks harmless or to be doing something else.
This obviously excludes clear obfuscation, horrible formatting, encoding the filename in any way, hiding the file open by doing the syscall by calling int 80, etc.
But, linux is more secure. These things are protected. No one is writing exploits for linux.
Oh, wait, it isn't, they aren't, and they are.
Wait, who said no one is writing exploits for Linux? People write exploits for everything. No software is 100% secure, and anyone who claims the opposite is a fool.
In fact, with all that open source, isn't it easier to see what is going on so I can write a better exploit?
Open code allows anyone to do security audits to patch vulnerabilities before they can be exploited. Patches also tend to propagate faster because of their public nature, and the fact that anyone with sufficient knowledge about the issue can write and apply those patches himself. On the other hand, when a vulnerability is found in closed software, you have no choice but to patiently wait for the vendor to fix it, which may take some time depending on various factors such as PR and the perceived priority of the vulnerability to the vendor's eyes.
Isn't it easier for me to, say, sneak a corporate or national spy into the development team and compromise the project?
You seem to imply that it would be harder to do the same in a non-open project. At least in an open project the code can be audited by anyone. When you get proprietary software you can't inspect it yourself unless you're a member of the project. And if said project is compromised, you can't do anything.
With millions of lines of code, do you think we could keep an Iranian or Chinese spy from getting malicious code into the project?
Chinese spy? I'm not even going to bother replying to this one.
Hypothetical:
- Start a project for a civilian equivelent of a military application
- Form a project team
- Accept a programmer from a country that has very specific ideology driven agendas against much of the western world
- Wonder why the government won't switch to the OS of your desire
Again, the same thing could happen for a closed project, and with greater repercussions, so your argument is meaningless.
Now, the REAL reasons why some governments don't switch to open source:
- Lack of understanding of the movement
- Switching technologies is expensive, especially when the vendors of the current one has made sure it would be difficult to switch by disregarding standards
- Misinformation from corporate interests that see open source as a threat to their current business model instead of embracing it, or people like you
But, wait, linux is more secure. These things are protected. Nobody is writing exploits.
Made-up bullshit again.
And to add to that: if /etc/passwd was supposed to be soooo guarded, it wouldn't be 644.
Readable to all.
The proper way to get information about the user, such as his name, his home directory, etc is to call the function getpwuid() in a manner like: getpwuid(getuid()), it returns the following struct:
Sure it has the user's password listed there (in some format), but this is the proper way to retrieve all the other data also found here. All good applications which save settings per user or try to be more friendly towards the user will call getpwuid() and in turn end up reading
If you think a program reading
As for reading Firefox files, I'm not sure what it's doing, but Skype does offer Firefox integration right? Surely it's not too hard to imagine it's trying to figure out your configuration and check for conflicting plugins, and the like.
You can be an insane coder too, read: Insane Coding