Safety of Linux Mint KDE

[selukwe]

As a Linux newbie, I installed LM 13 KDE to a USB flash drive, where the installation created 3 partitions - freely accessible FAT32, hidden Linux partition for the OS and again a hidden Solaris partition for its swap file.

My question is this: How safe is the Linux's main and swap file partitions when the login to Linux is password protected. My question is mainly whether someone might get access to my data stored on these partitions if my USB disk is stolen or lost. I know that with Windows the access to data even with password-protected login is pretty easy if such a disk is accessed from a bootable erd5, BartPE or Linux OS (unless the whole Windows OS is encrypted, e.g. with TrueCrypt). How is this done in Linux? Would my disk (not only USB but also a HDD where Linux is installed as the only OS) be an easy prey to look into?

[xenopeek]

This is not a topic specific to the KDE edition, so moving it here.

Assuming you selected to have an encrypted home folder during installation, you have not enabled automatic login, and have a long enough password your personal documents are relatively safe. You can gauge your password strength on various websites, such as http://www.passwordmeter.com/ (though I advise to never type your actual password, just something that is similar to it). Longer passwords are better than shorter passwords with w31rd characters.

While any tech savvy person that has physical access to your installation should be able to login as root very easily, it is not so easy to gain access to your encrypted files (they will have to guess your password). Changing your password on your user account (so they don't have to guess it), which root can do, will effectively destroy the files in your user's encrypted home directory.

With an encrypted home folder, your data should be mostly safe.

Note that if somebody has physical access to your installation, as root they can install some backdoor program so that when later you again log in they are able to get your personal documents that way. So if you are paranoid or carrying highly sensitive documents, you might want to increase your protection to prevent others from installing a backdoor on your installation. You may want to install with full disk encryption, instead of just home folder encrypted, though the Linux Mint installer currently can't do that automatically. There are various topics on that to be found however, such as viewtopic.php?f=46&t=103843. You may also want to password protect your GRUB2 boot loader, for example as shared here http://www.noobslab.com/2012/02/passwor ... -with.html.

[selukwe]

Many thanks, I learned a lot...

Password protecting home folder sounds intreaguing and a great idea but I was not given such an option during install... Is it possible to do it separately afterwards or how am I supposed to do it? Did I miss something when installing?

In the world of WinXP there's an option to use encrypted virtual disks, such as e.g. TrueCrypt, Dekart Private Disk or FreeOTFE. Is something similar possible also under Linux?

[xenopeek]

When creating the first user during installation, you had the option to encrypt the user's home folder. There are various guides on how to encrypt your home folder after installation, for example this should probably work: http://www.makeuseof.com/tag/encrypt-ho ... ion-linux/

You can also choose to make a new user account, and have that be encrypted. As shared by AlbertP here: viewtopic.php?f=90&t=105379#p594928

You can use TrueCrypt on Linux.I don't have any experience with that. Here are some alternatives as suggested by users of AlternativeTo.net: http://alternativeto.net/software/truec ... form=linux

[selukwe]

I'm afraid I wasn't offered an option to have an encrypted home folder during installation of LM 13 KBE and from the web I found that it was relevant to installing Ubuntu. To double-check on this, I made an additional, "testing" installation of LM and it is really like this. It's also a pity that LM has not included such an option; I'm sure many a user would welcome this. So I'll have a look at separate (later) encryption as you suggest.

To enhance the safety of the system, it would also be worthwhile to add a virtual keyboard to the login screen as this would protect the user against the hardware keyloggers at unknown PC's that are not connected with any OSs.

Do the LM programmers read this forum? It would be terrific if both features could be incorporated into future LM releases (or is there perhaps some other proper way how new ideas and tips could be communicated to them?).

[selukwe]

While any tech savvy person that has physical access to your installation should be able to login as root very easily, it is not so easy to gain access to your encrypted files (they will have to guess your password)... Changing your password on your user account (so they don't have to guess it), which root can do, will effectively destroy the files in your user's encrypted home directory.

I still return to this part of your earlier answer.

Do you mean that an experienced hacker may be actually able to log in to my password protected login as root not knowing my password? Do you really speak about him being able to log in as a root, not just to remove-reset my password? If this is really so, what is then the password protected login good for?

[xenopeek]

No, I'm saying a malicious person can log in as root and reset your password. That person can not log in as you unless he or she knows your password, or can easily guess it. And as shared, once your password is changed and you have an encrypted home folder, that effectively makes your files inaccessible. Even though the person now knows your password and can login as you, your files remain locked because your password was changed. The only way to change your password safely with an encrypted home folder is to login as yourself first, while the malicious person does so from the root login.

As for the option during installation, I see now that this isn't given with the KDE installer. It is given in the Gnome installer, so at least on MATE and Cinnamon by probably also on Xfce.

[selukwe]

One "subquestion" just to be more clear about this...

Would password protecting the grub boot loader prevent someone see (and access) my linux partition when booting from another linux medium? If not, then it would do only half job - preventing to reset my login password. But in order to have my home folder secure from access (viewing and copying!) it would also have to be encrypted separately.

Now how does such particualr encrypting process work? Is the home folder decrypted automatically on login or does it have to be decrypted manually afterwards? And if the home folder is really big (say a few GB..) would it take long to decrypt/encrypt it? If it is supposed to work this way then it would be highly impractical - also how would the OS behave with inaccessible user folder until it is decrypted?

[xenopeek]

With home folder encryption, which uses eCryptfs, you decrypt files only when you access them and encrypt them on saving changes. This is all done transparently to the user.

Perhaps this goes into too much detail, but Linux offers a wide variety of virtual filesystems. Like /proc, /var/run and others. While you can use these parts of your filesystem as any other part, they exist only in memory and not on disk. Filesystems of the type tmpfs, like /var/run, are just simple filesystems that exist only in memory and on which files can be put. You can read & write to them, but upon shutdown or reboot all their contents is lost. /proc and some others are actually a way to query and talk to the Linux kernel, and the files listed there don't actually exist but are generated by the Linux kernel for you and other programs to easily find information. For example in /proc, the directories with only numbers for their name are actually the process identifiers (PID) of each process running on your system. If you go into one of these directories, you can find out a lot about that process.

Right, so with an encrypted home folder you are actually also looking at a virtual filesystem. Your files are only stored on disk encrypted, in the .Private folder. If you are logged in, the passphrase to access your files is accessible and this .Private folder is mounted as a virtual filesystem on your home folder. So any request to read or write a file in your home folder actually goes through the eCryptfs program and it reads and decrypts, or encrypts and writes, then file requests from the .Private folder.