8 ms·

Windows Symbolic Link Mitigations

59 points by 2510c39011c5 11y ago

UnoriginalGuy 11y ago
Backwards compatibility is such a headache. Got to give it to Microsoft for their dedication to never breaking old code. I cannot imagine several of these scenarios happening more than in one or two programs given how niche they are. On modern UNIX (Linux, BSD, et al) when you create a symlink do you need write access into the target directory, or do they suffer from this same sandbox escape?
- TazeTSchnitzel 11y ago
  You don't need write access to the target. A symlink is simply a file with a special attribute set, so all you need is the ability to write to the symlink's location (as opposed to its target). e.g.: $ mkdir secrets $ ls -l drwxr-xr-x 2 ajf staff 68 28 Aug 15:17 secrets $ chmod -rwx secrets $ ls -l d--------- 2 ajf staff 68 28 Aug 15:17 secrets $ touch secrets/foo touch: secrets/foo: Permission denied $ ln -s secrets lies $
  - dogma1138 11y ago
    Hmm on Windows it will check the permissions for both the source and the target on NTFS junctions.....
    - TazeTSchnitzel 11y ago
      Yeah, I assume Windows's junctions work differently.
- deleted 11y ago
  [deleted]
- dr_zoidberg 11y ago
  Sometimes I get the feeling that, although good in theory, that dedication to keeping alive old code is also a big source of cruft and bugs in Windows. They didn't drop 16 bit support until Windows Vista! I mean, was there aby big chance of a 286 running Windows XP? I know, old (DOS-era) systems were being run inside WinXP, but having DOSbox take care of that was a way better solution -- which is what happened with those systems once they lost support from the OS.
  - protomyth 11y ago
    It really comes down to "Enterprise code better work or we won't upgrade". Its a straight migration issue, and that makes them an easy choice for an enterprise platform. It is amazing how many little programs cannot be broken. Now, I do wish they had done a "classic" emulation with a go forward API of .NET, but I guess that would have been hyper-difficult given the players.
    - mc32 11y ago
      It's quite true. About ten years ago I came across a system still running dos 3.1, not windows, dos. It controlled a microscope. They withheld upgrading because the licensing was significant for the small subdepts budget and while very antiquated, the system still worked, albeit inefficiently.
      - dogma1138 11y ago
        Why did it exactly work inefficiently? There are plenty of legacy systems out there, scientific and engineering equipment is a very common place to find them, i still got couple of scopes that are running DOS they are very good and very cheap why should i care? On a side note one of the big drivers dictating the shuttle decommission final date was that NASA ran out of 8086 chips they ran out of them in 2002, and there wasn't a big enough supply to push servicing them beyond 2012... The chips were apparently part of the pre-launch diagnostic module for the SRB's and there was an 8 months delay in shuttle missions in the early 2000's until NASA found a fresh batch some where. Since reading about that 13 years ago I still haven't heard of a cooler job at NASA (other than actually flying to space ;)) it's like being a modern day Indiana Jones hunting for new old hardware to keep their current missions in play... The International space station is probably running out of their 486DX's these days if some one has a hook on a good supply of fresh one's they might make a killing :)
NickHaflinger 11y ago
"There are three types of symbolic links .. Object Manager Symbolic Links, Registry Key Symbolic Links and NTFS Mount Points .. a fourth type, NTFS Symbolic Links" How did Unix ever manage with only the one type of symbolic link
- ygra 11y ago
  Because Unix uses the file system for everything Windows uses the object manager. Windows maps parts of the object manager to pre-existing concepts, like drive letters, for backwards compatibility. And, well, Windows has a registry, for better or for worse.

59 points by 2510c39011c5 11y ago

Backwards compatibility is such a headache. Got to give it to Microsoft for their dedication to never breaking old code. I cannot imagine several of these scenarios happening more than in one or two programs given how niche they are. On modern UNIX (Linux, BSD, et al) when you create a symlink do you need write access into the target directory, or do they suffer from this same sandbox escape?

TazeTSchnitzel 11y ago
You don't need write access to the target. A symlink is simply a file with a special attribute set, so all you need is the ability to write to the symlink's location (as opposed to its target). e.g.: $ mkdir secrets $ ls -l drwxr-xr-x 2 ajf staff 68 28 Aug 15:17 secrets $ chmod -rwx secrets $ ls -l d--------- 2 ajf staff 68 28 Aug 15:17 secrets $ touch secrets/foo touch: secrets/foo: Permission denied $ ln -s secrets lies $
- dogma1138 11y ago
  Hmm on Windows it will check the permissions for both the source and the target on NTFS junctions.....
  - TazeTSchnitzel 11y ago
    Yeah, I assume Windows's junctions work differently.
deleted 11y ago
[deleted]
dr_zoidberg 11y ago
Sometimes I get the feeling that, although good in theory, that dedication to keeping alive old code is also a big source of cruft and bugs in Windows. They didn't drop 16 bit support until Windows Vista! I mean, was there aby big chance of a 286 running Windows XP? I know, old (DOS-era) systems were being run inside WinXP, but having DOSbox take care of that was a way better solution -- which is what happened with those systems once they lost support from the OS.
- protomyth 11y ago
  It really comes down to "Enterprise code better work or we won't upgrade". Its a straight migration issue, and that makes them an easy choice for an enterprise platform. It is amazing how many little programs cannot be broken. Now, I do wish they had done a "classic" emulation with a go forward API of .NET, but I guess that would have been hyper-difficult given the players.
  - mc32 11y ago
    It's quite true. About ten years ago I came across a system still running dos 3.1, not windows, dos. It controlled a microscope. They withheld upgrading because the licensing was significant for the small subdepts budget and while very antiquated, the system still worked, albeit inefficiently.
    - dogma1138 11y ago
      Why did it exactly work inefficiently? There are plenty of legacy systems out there, scientific and engineering equipment is a very common place to find them, i still got couple of scopes that are running DOS they are very good and very cheap why should i care? On a side note one of the big drivers dictating the shuttle decommission final date was that NASA ran out of 8086 chips they ran out of them in 2002, and there wasn't a big enough supply to push servicing them beyond 2012... The chips were apparently part of the pre-launch diagnostic module for the SRB's and there was an 8 months delay in shuttle missions in the early 2000's until NASA found a fresh batch some where. Since reading about that 13 years ago I still haven't heard of a cooler job at NASA (other than actually flying to space ;)) it's like being a modern day Indiana Jones hunting for new old hardware to keep their current missions in play... The International space station is probably running out of their 486DX's these days if some one has a hook on a good supply of fresh one's they might make a killing :)

NickHaflinger 11y ago

"There are three types of symbolic links .. Object Manager Symbolic Links, Registry Key Symbolic Links and NTFS Mount Points .. a fourth type, NTFS Symbolic Links" How did Unix ever manage with only the one type of symbolic link

ygra 11y ago
Because Unix uses the file system for everything Windows uses the object manager. Windows maps parts of the object manager to pre-existing concepts, like drive letters, for backwards compatibility. And, well, Windows has a registry, for better or for worse.