6 ms·

ECryptfs Security Audit

77 points by SaintSal 12y ago

hadoukenio 12y ago
I chose eryptfs over TrueCrypt because I wasn't happy with using encryption software written by an anonymous developer. Was this a naive decision or do others feel the same? The audit linked says that it ecryptfs might not have been designed/written by a cryptographer. What would people recommend these days seeing as TrueCrypt is likely to be compromised and ecryptfs might not be as secure as it could be?
- bignaj 12y ago
  Well, TrueCrypt (controversially) recommended BitLocker... that seems to be one of the few options left. Disclaimer: I work for Microsoft in a non-related division but I feel like if it's good enough to protect enterprise customers' secrets it's good enough for my personal use outside of work. You are free to use whatever you like, of course. The HN neckbeard illuminati will likely disagree with me, already aware of this. To each his/her own.
  - fluidcruft 12y ago
    BitLocker has the advantage of being accepted by my employer and now that XP was banished in favor of Win7 it's available on all of the company computers. It has the extreme disadvantage that I can't mount my disk on anything except windows. Which is a no-go given that I mostly live in Linux and most of my colleagues do a lot of work with MacOS. We all have Windows machines for the bureaucratic stuff we must do (word documents, excel, various internal web portals that require IE or some sort of ActiveX plugin). The things is: when it comes to closed source companies, Microsoft is one that I am willing to accept that they have sound engineering and release policies. But they refuse to explain how it works, so we can't inter-operate and we have to do something else. (Which for me means that I use a FIPS certified hardware encrypted USB drive with a built in keypad that you use to enter a pin, but for everyone else it basically means they don't bother and just use stupid unencrypted FAT drives and don't care if they "get caught". Or they try to use the awful Box sync shit IT is currently trying to foist on us)
    - bignaj 12y ago
      Just to add some perspective... for most of the world lack of support for Linux isn't an extreme disadvantage. For most it's not a disadvantage at all. I have a Linux machine and use Linux servers just like you, but welcome to the HN bubble...
    - tux1968 12y ago
      You should be able to mount BitLocker volumes under Linux with Fuse: https://github.com/Aorimn/dislocker
  - Dylan16807 12y ago
    That disclaimer really detracts from your post. But on topic, BitLocker is only suitable for enterprise because it's simply unavailable for home versions.
    - eli 12y ago
      No, it's available on the "Ultimate" edition of windows too, which is for home use. Many higher-end Windows machines come with it already installed.
    - bignaj 12y ago
      I agree, but I feel like it's only fair to report any potential conflict of interest (come from a research background where this is standard). You are also incorrect: Bitlocker is not only available for enterprise versions. See the other reply to your comment :)
      - Dylan16807 12y ago
        It's not that you have a disclaimer, it's that you're being hostile in it. Ultimate is a weird expensive combined edition that doesn't even exist for Windows 8. I didn't think I had to specifically exclude it, but I definitely don't accept it as making BitLocker available for 'home versions'
- tptacek 12y ago
  EcryptFS and Truecrypt are very different systems. Truecrypt is simulated hardware encryption. It creates a virtual encrypted hard disk, which your operating system can more or less treat like an ordinary hard disk, but for the kernel hooks Truecrypt adds to lock and unlock the disk. EcryptFS is an encrypted filesystem. Unlike Truecrypt, which encrypts individual disk blocks, systems like EcryptFS encrypt and decrypt whole files. All else being equal, you'd prefer an encrypted filesystem to a simulated encrypted hard disk. Some of the reasons are technical: the crypto involved in encrypting a block device is crappier than the crypto involved in protecting a file (most notably, block crypto is typically not authenticated). But at a higher level, the reason is that you'd like your cryptosystem to have as much information to work with as possible, and one nice bit of information for it to have is where files begin and end. All things are not equal though, and to select EcryptFS over Truecrypt, you also have to select EcryptFS's design and implementation over Truecrypt's. Truecrypt's design is simple and has been looked at more carefully than EcryptFS's. On the other hand, Truecrypt is an XTS cryptosystem, which isn't great. I would have a hard time making a recommendation between the two. It's more important that you understand the limitations of transparent disk encryption. Unless you are pretty regularly telling your crypto software that it's OK to unlock a given file or disk or whatever, then it's probably "always on", and your keys are always resident in memory, and your files are more or less always exposed to malware. Malware is a much scarier threat (for most people) than police raids. If you're interested: we work in a pretty high-risk environment (we handle a lot of hazmat). Our general crypto regime at Matasano is: * Everyone uses Filevault2's native XTS disk encryption (along with some fiddly rules for what state your machine needs to be in if it's in your bag). * Everyone uses OS X encrypted DMGs (I don't remember what the block crypto design for DMGs is, but you can check out John the Ripper if you're curious) to isolate different projects; we audit machines to make sure keys aren't in the keyring. * Everyone uses PGP for email and to encrypt specific files. If this sounds like a pain in the ass, be aware that this is pretty close to the minimum viable amount of security you can be providing a mobile device; if you're skipping one of these steps, you should know why.
  - pbsd 12y ago
    Do you guys only use OS X over there, or are there equivalent setups for other systems?
- x1798DE 12y ago
  >What would people recommend these days seeing as TrueCrypt is likely to be compromised and ecryptfs might not be as secure as it could be? Just to push back on this a bit, I don't think it's particularly likely that TrueCrypt is in any way compromised. It's been stable software for quite some time now, it's open source, and there have been no identified flaws with it. The main problem with TrueCrypt is that it may be nearing the end of its useful life as filesystem technology changes and TrueCrypt is not updated along with it (this has already happened with GPT/UEFI and TrueCrypt's full-disk encryption). If TrueCrypt will work for you, at the moment you don't really have to worry that it's been compromised or worry about "lack of support" (note it hadn't been updated for over two years before the abrupt departure of the anonymous devs). It's quite possible that you won't even run into any compatibility issues in the future, as future encryption tools will likely offer support for TrueCrypt volumes - once the phase II (crypto) audit is complete, assuming no major flaws are found, it will be a vetted, open technology, so it'd be a no-brainer to write an implementation based on it.
  - tptacek 12y ago
    I'm involved in the TC audit, and zero of the people I know that are working with the TC audit believe that it's compromised.
    - mhogomchungu 12y ago
      TrueCrypt in linux has a serious security issue discussed below and i hope you guys will address this. TrueCrypt has a serious security bug that allows a person who can mount TrueCrypt volumes to get root shell or run any command as root user because it mount its volumes with "suid" option instead of "nosuid" option. You can get the below program to test locally if you have a linux box around. http://pastebin.com/vT4G7nU0 http://pastebin.com/vT4G7nU0
      - simoncion 12y ago
        > 4. set the binary to have 4755 permissions with owner as root:root. If you can do this, you already have root access. If you have root access, then you don't need dirty tricks to get root access. Additionally, in the three minutes that I spent searching, I found a bunch of evidence that indicated that TrueCrypt volumes mounted through FUSE are mounted with the nosuid option. (Ferinstance, search for 'nosuid' here: http://www.reddit.com/r/archlinux/comments/1fcwvr/truecrypt_volumes_will_not_dismount_volume/ http://www.reddit.com/r/archlinux/comments/1fcwvr/truecrypt_... )
dobbsbob 12y ago
This is an example of what you can do with eCryptfs and Overlayfs. http://www.onarlioglu.com/privexec/ http://www.onarlioglu.com/privexec/

77 points by SaintSal 12y ago

I chose eryptfs over TrueCrypt because I wasn't happy with using encryption software written by an anonymous developer. Was this a naive decision or do others feel the same? The audit linked says that it ecryptfs might not have been designed/written by a cryptographer. What would people recommend these days seeing as TrueCrypt is likely to be compromised and ecryptfs might not be as secure as it could be?

bignaj 12y ago
Well, TrueCrypt (controversially) recommended BitLocker... that seems to be one of the few options left. Disclaimer: I work for Microsoft in a non-related division but I feel like if it's good enough to protect enterprise customers' secrets it's good enough for my personal use outside of work. You are free to use whatever you like, of course. The HN neckbeard illuminati will likely disagree with me, already aware of this. To each his/her own.
- fluidcruft 12y ago
  BitLocker has the advantage of being accepted by my employer and now that XP was banished in favor of Win7 it's available on all of the company computers. It has the extreme disadvantage that I can't mount my disk on anything except windows. Which is a no-go given that I mostly live in Linux and most of my colleagues do a lot of work with MacOS. We all have Windows machines for the bureaucratic stuff we must do (word documents, excel, various internal web portals that require IE or some sort of ActiveX plugin). The things is: when it comes to closed source companies, Microsoft is one that I am willing to accept that they have sound engineering and release policies. But they refuse to explain how it works, so we can't inter-operate and we have to do something else. (Which for me means that I use a FIPS certified hardware encrypted USB drive with a built in keypad that you use to enter a pin, but for everyone else it basically means they don't bother and just use stupid unencrypted FAT drives and don't care if they "get caught". Or they try to use the awful Box sync shit IT is currently trying to foist on us)
  - bignaj 12y ago
    Just to add some perspective... for most of the world lack of support for Linux isn't an extreme disadvantage. For most it's not a disadvantage at all. I have a Linux machine and use Linux servers just like you, but welcome to the HN bubble...
  - tux1968 12y ago
    You should be able to mount BitLocker volumes under Linux with Fuse: https://github.com/Aorimn/dislocker
- Dylan16807 12y ago
  That disclaimer really detracts from your post. But on topic, BitLocker is only suitable for enterprise because it's simply unavailable for home versions.
  - eli 12y ago
    No, it's available on the "Ultimate" edition of windows too, which is for home use. Many higher-end Windows machines come with it already installed.
  - bignaj 12y ago
    I agree, but I feel like it's only fair to report any potential conflict of interest (come from a research background where this is standard). You are also incorrect: Bitlocker is not only available for enterprise versions. See the other reply to your comment :)
    - Dylan16807 12y ago
      It's not that you have a disclaimer, it's that you're being hostile in it. Ultimate is a weird expensive combined edition that doesn't even exist for Windows 8. I didn't think I had to specifically exclude it, but I definitely don't accept it as making BitLocker available for 'home versions'
tptacek 12y ago
EcryptFS and Truecrypt are very different systems. Truecrypt is simulated hardware encryption. It creates a virtual encrypted hard disk, which your operating system can more or less treat like an ordinary hard disk, but for the kernel hooks Truecrypt adds to lock and unlock the disk. EcryptFS is an encrypted filesystem. Unlike Truecrypt, which encrypts individual disk blocks, systems like EcryptFS encrypt and decrypt whole files. All else being equal, you'd prefer an encrypted filesystem to a simulated encrypted hard disk. Some of the reasons are technical: the crypto involved in encrypting a block device is crappier than the crypto involved in protecting a file (most notably, block crypto is typically not authenticated). But at a higher level, the reason is that you'd like your cryptosystem to have as much information to work with as possible, and one nice bit of information for it to have is where files begin and end. All things are not equal though, and to select EcryptFS over Truecrypt, you also have to select EcryptFS's design and implementation over Truecrypt's. Truecrypt's design is simple and has been looked at more carefully than EcryptFS's. On the other hand, Truecrypt is an XTS cryptosystem, which isn't great. I would have a hard time making a recommendation between the two. It's more important that you understand the limitations of transparent disk encryption. Unless you are pretty regularly telling your crypto software that it's OK to unlock a given file or disk or whatever, then it's probably "always on", and your keys are always resident in memory, and your files are more or less always exposed to malware. Malware is a much scarier threat (for most people) than police raids. If you're interested: we work in a pretty high-risk environment (we handle a lot of hazmat). Our general crypto regime at Matasano is: * Everyone uses Filevault2's native XTS disk encryption (along with some fiddly rules for what state your machine needs to be in if it's in your bag). * Everyone uses OS X encrypted DMGs (I don't remember what the block crypto design for DMGs is, but you can check out John the Ripper if you're curious) to isolate different projects; we audit machines to make sure keys aren't in the keyring. * Everyone uses PGP for email and to encrypt specific files. If this sounds like a pain in the ass, be aware that this is pretty close to the minimum viable amount of security you can be providing a mobile device; if you're skipping one of these steps, you should know why.
- pbsd 12y ago
  Do you guys only use OS X over there, or are there equivalent setups for other systems?
x1798DE 12y ago
>What would people recommend these days seeing as TrueCrypt is likely to be compromised and ecryptfs might not be as secure as it could be? Just to push back on this a bit, I don't think it's particularly likely that TrueCrypt is in any way compromised. It's been stable software for quite some time now, it's open source, and there have been no identified flaws with it. The main problem with TrueCrypt is that it may be nearing the end of its useful life as filesystem technology changes and TrueCrypt is not updated along with it (this has already happened with GPT/UEFI and TrueCrypt's full-disk encryption). If TrueCrypt will work for you, at the moment you don't really have to worry that it's been compromised or worry about "lack of support" (note it hadn't been updated for over two years before the abrupt departure of the anonymous devs). It's quite possible that you won't even run into any compatibility issues in the future, as future encryption tools will likely offer support for TrueCrypt volumes - once the phase II (crypto) audit is complete, assuming no major flaws are found, it will be a vetted, open technology, so it'd be a no-brainer to write an implementation based on it.
- tptacek 12y ago
  I'm involved in the TC audit, and zero of the people I know that are working with the TC audit believe that it's compromised.
  - mhogomchungu 12y ago
    TrueCrypt in linux has a serious security issue discussed below and i hope you guys will address this. TrueCrypt has a serious security bug that allows a person who can mount TrueCrypt volumes to get root shell or run any command as root user because it mount its volumes with "suid" option instead of "nosuid" option. You can get the below program to test locally if you have a linux box around. http://pastebin.com/vT4G7nU0 http://pastebin.com/vT4G7nU0
    - simoncion 12y ago
      > 4. set the binary to have 4755 permissions with owner as root:root. If you can do this, you already have root access. If you have root access, then you don't need dirty tricks to get root access. Additionally, in the three minutes that I spent searching, I found a bunch of evidence that indicated that TrueCrypt volumes mounted through FUSE are mounted with the nosuid option. (Ferinstance, search for 'nosuid' here: http://www.reddit.com/r/archlinux/comments/1fcwvr/truecrypt_volumes_will_not_dismount_volume/ http://www.reddit.com/r/archlinux/comments/1fcwvr/truecrypt_... )

dobbsbob 12y ago

This is an example of what you can do with eCryptfs and Overlayfs. http://www.onarlioglu.com/privexec/ http://www.onarlioglu.com/privexec/