9 ms·

The State of Linux Security

141 points by kungfudoi 10y ago

0xcde4c3db 10y ago
> Backdoor in Linux Mint (February 2016) > Stop using MD5. If you still use SHA1, then add also the SHA256 or SHA512 hashes. How did hash strength have anything to do with this? Unless my sources are completely out of whack, the MD5 of the backdoored ISO didn't match the official ISO. My understanding is that there is a vulnerability along these lines, but it requires the official build process to be compromised, whereas this was an edit on the Mint website to point to a malicious file on an attacker-controlled server.
- chao- 10y ago
  The edit to the site was due to the whole thing being Wordpress. I know that Wordpress is decently flexible, "good enough" or even comfortable for many users, even technical ones, my thought is why not have the site be statically hosted instead? Or at least the primary informational pages.
- maxt 10y ago
  Interesting that the site uses TLS, but most of the servers containing the download use plain old HTTP, which as we know, can be easily subjected to a MITM attack. https://linuxmint.com/edition.php?id=225 https://linuxmint.com/edition.php?id=225 Only a few of the ISOs are delivered with TLS/HTTPS, like this one: https://mirrors.c0urier.net/linux/linuxmint/iso/stable/18.1/linuxmint-18.1-cinnamon-32bit.iso https://mirrors.c0urier.net/linux/linuxmint/iso/stable/18.1/...
  - dublinben 10y ago
    Properly signed images shouldn't need to be delivered over a secure connection. As long as you can receive a signed hash, and the signing key itself over a secure connection, you can obtain the image itself from anywhere.
    - dsp1234 10y ago
      and the signed hash is actually checked against the image. Of course, this is the step that is missing because it's a non-mandatory manual process. Serving the images directly over HTTPS would provide more security for every end user that is not manually checking signing hashes.
    - garrettr_ 10y ago
      True, although sometimes it's good to deliver signed updates over a secure connection for defense-in-depth - for example, to mitigate vulnerabilities like the recent CVE-2016-1252.
      - dom0 10y ago
        +1 "but some software has it's own crypto"¹ is kinda bad excuse for actively avoiding additional security - like Debian has on their mirrors (I think there even is (was?) an FAQ entry why there are no HTTPS mirrors, stating that APT packages are securely signed and that's all you'd need). ¹ I'm aware that APT actually uses GPG, but it does (did) so fishy manipulations both before and after invoking GPG on the signed files, that, if this would've happened in a corporate setting, I'd have rather peculiar questions for the employee who wrote that code. That recent CVE, and also issues in software that I co-maintain, plus all the other CVEs that are delivered to my inbox changed my mind on open source quite a lot. Open source is completely worthless if no one actually bothers to read the code; I doubt anyone actually read those portions of the APT code, because anyone with a secure coding or crypto coding background should be alerted already by the function names (look them up). Instead we all always assume "ah well people use it and someone probably checked that anyway... should be good to go!". NO. It's not good to go. Read [the] code.
        cyphar 10y ago
        > ¹ I'm aware that APT actually uses GPG, but it does (did) so fishy manipulations both before and after invoking GPG on the signed files, that, if this would've happened in a corporate setting, I'd have rather peculiar questions for the employee who wrote that code. From the openSUSE, I brought up my concerns about us not using HTTPS and it boils down to the fact that few mirrors want to host stuff over SSL. And if not many mirrors will do it, the benefit to users is diminished (you can't force the usage of SSL on the client). On the plus side, openSUSE does serve a copy of the GPG signing key for the ISO over HTTPS (from the main site). I just wish that there were less steps required to be sure that the ISO is official.
- clishem 10y ago
  Hashing strength has nothing to do with it. The real lesson is that they should have signed the hash they put on their website and actively encourage users to check it.
- drvdevd 10y ago
  I would also argue that it's important not to conflate issues with the Linux kernel with any particular Linux distribution specific issue. The incident with Linux Mint is not reflective of the broader security of Linux in general, although it is good to point out that how one distributes anything can have security ramifications. I feel the same way about the discussion of Mirai - the only thing broken embedded/IoT systems have in common with any given Linux distro, is the kernel, and maybe a few basic userspace bits (sometimes). The site does have some interesting discussion about Core Infrastructure (again technically separate from Linux, although fundamental) and other Kernel issues and hardening though.
lostmsu 10y ago
Wait, Linux did not have stack guard pages and r-x code pages until 4.9?
- luch 10y ago
  Pax/Grsecurity fork probably has it for some time, but not mainline tree (i.e "torvalds" linux).
ctz 10y ago
Linux doesn't power the smallest devices in the world. It's about two orders of magnitude too large out at the low end.
- ancarda 10y ago
  Out of interest, what does?
  - dmoy 10y ago
    Just random RT OS's? It's been awhile since I've worked on tiny 8 bit mcus, but all the stuff was really small and seemingly hand rolled, nothing as monolithic as Linux. I would not be surprised to learn that it varies from company to company and chip to chip, with various bits being shared for common logic.
    - Tempest1981 10y ago
      I remember VxWorks. Bigger than a while loop, but used in space missions back in the 90s: http://www.windriver.com/inspace/ http://www.windriver.com/inspace/ Edit: looks like VxWorks wants a 32-bit CPU, 128KB of ROM, and 1-2MB of RAM. But you get threads, networking, filesystem, etc.
  - emidln 10y ago
    On the really low end, hardware is often single-purpose and you don't really need an operating system. When there is an operating system (maybe you have to listen to messages from something while performing a previously requested activity), a small hard real-time scheduling library gets used as an "operating system".
  - marcosdumay 10y ago
    There are all kinds of micro-everything circulating out there, from timing and IO drivers to entire network stacks.
  - foofoo55 10y ago
    The almost-smallest devices are powered by LoopOS(tm): while(1){ }
eugeneionesco 10y ago
Not a single mention of grsecurity and RAP, useless article.
- staticassertion 10y ago
  Yep. More of the same. Despite most of the recent improvements to the Linux kernel essentially boiling down to cherry picking Grsec/PaX, no one gives them due credit. And no one's even talking about RAP.
- cyphar 10y ago
  Well, given the fact that the grsecurity folks violate the GPL, in not sure what recognition they deserve other than "you can now get their feature in a free software, mainline kernel".
  - eugeneionesco 10y ago
    Can you let me know exactly where I can get RAP? You seems to be slandering grsec for no reason.
    - cyphar 10y ago
      > You seems to be slandering grsec for no reason. It's not without reason, I don't like people abusing free software in the manner the grsecurity people do it (https://grsecurity.net/agree/agreement.php https://grsecurity.net/agree/agreement.php). They license code under the GPL (because they have to) but then they effectively tell their customers that exercising their right to redistribute code will result in a termination of contract (which is at best against the spirit of the GPL, and at worst illegal).
      - eugeneionesco 10y ago
        You obviously have no clue how GPL works. Everything is explained very well on the agreement page.
snvzz 10y ago
Linux will always be insecure. There's no fixing millions of lines of code running in supervisor mode. What will happen instead is that the world will move on to a microkernel-based OS.
- SEJeff 10y ago
  Ok Mr Tanenbaum, Linus and you already had this argument </sarcasm>
  - pjmlp 10y ago
    And looking at embedded OSes, L4, sandboxing in Apple, Google and Microsoft OSes, the future direction is quite clear.
    - dispose13432 10y ago
      Does Apple run on a MicroKernel? Microsoft? Google definitely doesn't (it runs on linux). The problems they solve are orthogonal to kernel issues. Sandboxing thwarts userspace attacks (any program I install has access to my userspace). Microkernels solve kernel side attacks.
      - huxley 10y ago
        Apple uses XNU which is a hybrid kernel based on the Mach 3 microkernel https://en.wikipedia.org/wiki/XNU https://en.wikipedia.org/wiki/XNU
        tossedaway334 10y ago
        OSX is effectively a microkernel in name only, its a microkernel with a single monolithic UNIX kernel client, and has virtually none of the advantages of a real microkernel setup with multiple clients sharing tasks.
      - mtgx 10y ago
        The real irony is that Android might as well run on a microkernel, considering no OEM has any intention of ever making their firmware work on anyone else's hardware. Everyone's ROMs would be more or less just as incompatible as they are now, but at least they'd be faster and much more secure at the kernel level.

141 points by kungfudoi 10y ago

> Backdoor in Linux Mint (February 2016) > Stop using MD5. If you still use SHA1, then add also the SHA256 or SHA512 hashes. How did hash strength have anything to do with this? Unless my sources are completely out of whack, the MD5 of the backdoored ISO didn't match the official ISO. My understanding is that there is a vulnerability along these lines, but it requires the official build process to be compromised, whereas this was an edit on the Mint website to point to a malicious file on an attacker-controlled server.

chao- 10y ago
The edit to the site was due to the whole thing being Wordpress. I know that Wordpress is decently flexible, "good enough" or even comfortable for many users, even technical ones, my thought is why not have the site be statically hosted instead? Or at least the primary informational pages.
maxt 10y ago
Interesting that the site uses TLS, but most of the servers containing the download use plain old HTTP, which as we know, can be easily subjected to a MITM attack. https://linuxmint.com/edition.php?id=225 https://linuxmint.com/edition.php?id=225 Only a few of the ISOs are delivered with TLS/HTTPS, like this one: https://mirrors.c0urier.net/linux/linuxmint/iso/stable/18.1/linuxmint-18.1-cinnamon-32bit.iso https://mirrors.c0urier.net/linux/linuxmint/iso/stable/18.1/...
- dublinben 10y ago
  Properly signed images shouldn't need to be delivered over a secure connection. As long as you can receive a signed hash, and the signing key itself over a secure connection, you can obtain the image itself from anywhere.
  - dsp1234 10y ago
    and the signed hash is actually checked against the image. Of course, this is the step that is missing because it's a non-mandatory manual process. Serving the images directly over HTTPS would provide more security for every end user that is not manually checking signing hashes.
  - garrettr_ 10y ago
    True, although sometimes it's good to deliver signed updates over a secure connection for defense-in-depth - for example, to mitigate vulnerabilities like the recent CVE-2016-1252.
    - dom0 10y ago
      +1 "but some software has it's own crypto"¹ is kinda bad excuse for actively avoiding additional security - like Debian has on their mirrors (I think there even is (was?) an FAQ entry why there are no HTTPS mirrors, stating that APT packages are securely signed and that's all you'd need). ¹ I'm aware that APT actually uses GPG, but it does (did) so fishy manipulations both before and after invoking GPG on the signed files, that, if this would've happened in a corporate setting, I'd have rather peculiar questions for the employee who wrote that code. That recent CVE, and also issues in software that I co-maintain, plus all the other CVEs that are delivered to my inbox changed my mind on open source quite a lot. Open source is completely worthless if no one actually bothers to read the code; I doubt anyone actually read those portions of the APT code, because anyone with a secure coding or crypto coding background should be alerted already by the function names (look them up). Instead we all always assume "ah well people use it and someone probably checked that anyway... should be good to go!". NO. It's not good to go. Read [the] code.
      - cyphar 10y ago
        > ¹ I'm aware that APT actually uses GPG, but it does (did) so fishy manipulations both before and after invoking GPG on the signed files, that, if this would've happened in a corporate setting, I'd have rather peculiar questions for the employee who wrote that code. From the openSUSE, I brought up my concerns about us not using HTTPS and it boils down to the fact that few mirrors want to host stuff over SSL. And if not many mirrors will do it, the benefit to users is diminished (you can't force the usage of SSL on the client). On the plus side, openSUSE does serve a copy of the GPG signing key for the ISO over HTTPS (from the main site). I just wish that there were less steps required to be sure that the ISO is official.
clishem 10y ago
Hashing strength has nothing to do with it. The real lesson is that they should have signed the hash they put on their website and actively encourage users to check it.
drvdevd 10y ago
I would also argue that it's important not to conflate issues with the Linux kernel with any particular Linux distribution specific issue. The incident with Linux Mint is not reflective of the broader security of Linux in general, although it is good to point out that how one distributes anything can have security ramifications. I feel the same way about the discussion of Mirai - the only thing broken embedded/IoT systems have in common with any given Linux distro, is the kernel, and maybe a few basic userspace bits (sometimes). The site does have some interesting discussion about Core Infrastructure (again technically separate from Linux, although fundamental) and other Kernel issues and hardening though.

lostmsu 10y ago

Wait, Linux did not have stack guard pages and r-x code pages until 4.9?

luch 10y ago
Pax/Grsecurity fork probably has it for some time, but not mainline tree (i.e "torvalds" linux).

ctz 10y ago

Linux doesn't power the smallest devices in the world. It's about two orders of magnitude too large out at the low end.

ancarda 10y ago
Out of interest, what does?
- dmoy 10y ago
  Just random RT OS's? It's been awhile since I've worked on tiny 8 bit mcus, but all the stuff was really small and seemingly hand rolled, nothing as monolithic as Linux. I would not be surprised to learn that it varies from company to company and chip to chip, with various bits being shared for common logic.
  - Tempest1981 10y ago
    I remember VxWorks. Bigger than a while loop, but used in space missions back in the 90s: http://www.windriver.com/inspace/ http://www.windriver.com/inspace/ Edit: looks like VxWorks wants a 32-bit CPU, 128KB of ROM, and 1-2MB of RAM. But you get threads, networking, filesystem, etc.
- emidln 10y ago
  On the really low end, hardware is often single-purpose and you don't really need an operating system. When there is an operating system (maybe you have to listen to messages from something while performing a previously requested activity), a small hard real-time scheduling library gets used as an "operating system".
- marcosdumay 10y ago
  There are all kinds of micro-everything circulating out there, from timing and IO drivers to entire network stacks.
- foofoo55 10y ago
  The almost-smallest devices are powered by LoopOS(tm): while(1){ }

eugeneionesco 10y ago

Not a single mention of grsecurity and RAP, useless article.

staticassertion 10y ago
Yep. More of the same. Despite most of the recent improvements to the Linux kernel essentially boiling down to cherry picking Grsec/PaX, no one gives them due credit. And no one's even talking about RAP.
cyphar 10y ago
Well, given the fact that the grsecurity folks violate the GPL, in not sure what recognition they deserve other than "you can now get their feature in a free software, mainline kernel".
- eugeneionesco 10y ago
  Can you let me know exactly where I can get RAP? You seems to be slandering grsec for no reason.
  - cyphar 10y ago
    > You seems to be slandering grsec for no reason. It's not without reason, I don't like people abusing free software in the manner the grsecurity people do it (https://grsecurity.net/agree/agreement.php https://grsecurity.net/agree/agreement.php). They license code under the GPL (because they have to) but then they effectively tell their customers that exercising their right to redistribute code will result in a termination of contract (which is at best against the spirit of the GPL, and at worst illegal).
    - eugeneionesco 10y ago
      You obviously have no clue how GPL works. Everything is explained very well on the agreement page.

snvzz 10y ago

Linux will always be insecure. There's no fixing millions of lines of code running in supervisor mode. What will happen instead is that the world will move on to a microkernel-based OS.

SEJeff 10y ago
Ok Mr Tanenbaum, Linus and you already had this argument </sarcasm>
- pjmlp 10y ago
  And looking at embedded OSes, L4, sandboxing in Apple, Google and Microsoft OSes, the future direction is quite clear.
  - dispose13432 10y ago
    Does Apple run on a MicroKernel? Microsoft? Google definitely doesn't (it runs on linux). The problems they solve are orthogonal to kernel issues. Sandboxing thwarts userspace attacks (any program I install has access to my userspace). Microkernels solve kernel side attacks.
    - huxley 10y ago
      Apple uses XNU which is a hybrid kernel based on the Mach 3 microkernel https://en.wikipedia.org/wiki/XNU https://en.wikipedia.org/wiki/XNU
      - tossedaway334 10y ago
        OSX is effectively a microkernel in name only, its a microkernel with a single monolithic UNIX kernel client, and has virtually none of the advantages of a real microkernel setup with multiple clients sharing tasks.
    - mtgx 10y ago
      The real irony is that Android might as well run on a microkernel, considering no OEM has any intention of ever making their firmware work on anyone else's hardware. Everyone's ROMs would be more or less just as incompatible as they are now, but at least they'd be faster and much more secure at the kernel level.