Beefy Boxes and Bandwidth Generously Provided by pair Networks
Clear questions and runnable code
get the best and fastest answer
 
PerlMonks  

Re: Re: Re: Re: Re: Re: Re: exiting a chroot environment

by MarkM (Curate)
on Jul 09, 2003 at 01:59 UTC ( #272539=note: print w/ replies, xml ) Need Help??


in reply to Re: Re: Re: Re: Re: Re: exiting a chroot environment
in thread exiting a chroot environment

I believe the conflict in our understanding is in each of our understanding on where the /.. = /. = / magic is implemented. My understanding of the file system structures tells me that /.. = /. = / is implemented at mkfs time, not at run time. The '..' and '.' entries in '/' both refer to the same inode as '/' refers to. There is no special magic in the kernel.

It is possible that I am incorrect, however, I suggest to you that my understanding is the only understanding that explains why Linux allows users to escape a chroot() jail by referring to '.' and './..'.

UPDATE:

I think we are both wrong. I can't seem to escape the Linux chroot() jail in any of the ways listed above unless '.' was already outside the chroot() jail, which is the exploit that the man page refers to.


Comment on Re: Re: Re: Re: Re: Re: Re: exiting a chroot environment
Re: Re: Re: Re: Re: Re: Re: Re: exiting a chroot environment
by sauoq (Abbot) on Jul 09, 2003 at 02:10 UTC
    explains why Linux allows users to escape a chroot() jail

    Ah, but Linux, AFAIK, doesn't allow just any user to escape the chroot() environment. It only allows the super-user to escape it.

    I think we might be referring to two different special cases.

    As for when /.. = /. = / is implemented, I wouldn't think it would happen during mkfs because mkfs would have no way of knowing whether the filesystem in question would be used as the root fs or not. (Might there be something going on when the root fs is mounted?) My understanding of this stuff is admittedly weak; I'd be happy to receive some enlightenment.

    -sauoq
    "My two cents aren't worth a dime.";
    

      The root file system is the only file system that doesn't need /. and /.. to be special.

      The special case is when a file system is mounted as a non-root filesystem, as then /mount/point/.. needs to appear to refer to the same inode as /mount does. The same is true of chroot(). The Linux code seems to jump through quite a few hoops (with functions names like 'graft_tree()') to deal with mounts...

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://272539]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others avoiding work at the Monastery: (5)
As of 2014-09-19 02:51 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    How do you remember the number of days in each month?











    Results (129 votes), past polls