FTP users - preventing access to other directories

I want to allow an external user to access my unix system(through ftp) and drop/read files from one particular directory. for example the ftp user can go to directory /A/B/C and drop files to this directory or pick files from this directory.

The issue here that this after logging in using the ftp user id and password, this user can go to the root by doing a cd/ and once there, can access any files/directories that have the 666(rw_rw_rw) permissions.

How can I prevent this ftp user  from accessing/seeing any directory other than /A/B/C??

Thanks.
AreyannGurbaxaniAsked:
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jlevieCommented:
You need to set up a chroot enviornment for the FTP server that locks the user into /A when the FTP sesion starts. Within that session a user can 'cd' to any directory below /A (e.g. /A/B, or /A/C/D), but will not be able to change to any directory outside of /A. Effectively the root directory becomes the directory of the chroot environment.

How this is done depends on what FTP server your Unix system runs. The standard FTP server found on many Unix systems is a direct descendant of the original BSD server and it can be quite a bit of work to set up a chroot FTP server. FTP servers of later genre (NcFTPd, ProFTP, vsftpd, etc) make this quite easy.

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chris_calabreseCommented:
The ftpd man page on your system probably tells how to set this up.
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TintinCommented:
What Unix flavour are you running and which FTP server are you running?

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gheistCommented:
This option is called "chroot user to home directory" on most ftp servers
If your system ftp server does not support that, you can use PureFTPd or ProFTPd to accomplish what you need.
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TroxaliasCommented:
It  depends on the ftp server you are using but maybe this will do the trick:
Support that user's home directory is /A/B . Edit /etc/passwd and change user's home directory to /A/./B . Depending on your ftpd when the user logs in he will see /A/B as the root direcotry...
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CaseybeaCommented:
Sounds like you're running a pretty icky FTP server.    I'd get rid of it........... (who know what OTHER security holes you have because of it?)

This is the most secure FTP server known today for Unix systems--  and it's free.   And the documentation as well as configuration file are clearly laid out.

http://vsftpd.beasts.org/

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CaseybeaCommented:
I'd recommend an even split.
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