Finally managed to create a jailed SFTP server, but how secure?

TheO idgajelas@yahoo.com
Fri Dec 5 19:01:00 GMT 2008


> 
> You also need to try symlinks that point outside the "jail". Try 
> creating them both from the shell and within SFTP.
> 

Just got back from my Christmas shopping and now back to work :)

I don't know how to create a symlink from inside SFTP so I did it only from 
Console. I have created two files; foo and bar. foo is a link to a file outside
the jail /foo (absolute root), while bar is an ordinary file.

    sftp> ls -al
    drwxr-xr-x    2 root     root            0 Dec  5 15:52 .
    drwxr-xr-x    3 root     root            0 Dec  4 16:22 ..
    -rw-r--r--    1 root     root           34 Dec  5 15:52 bar
    lrwxrwxrwx    1 root     root            4 Dec  5 15:49 foo
    sftp> get foo
    Fetching /home/Administrator/foo to foo
    Couldn't stat remote file: No such file or directory
    sftp> get bar
    Fetching /home/Administrator/bar to bar
    /home/Administrator/bar                       100%   34     0.0KB/s   00:01

As expected user can't gain access outside his jail. But even if it had worked, 
I wouldn't have created a such "facility" purposedly myself.


> 
> Don't forget that even if you decide SFTP is "secure enough", you 
> need to consider the system as a whole.  One of the problems with
> Windows' security in general is the number of open ports and services 
> that are running.  If unauthorized users are able to gain access to 
> the system via any other route, then any security SFTP gives you is 
> totally illusory.  You would really need an external, aggressive 
> firewall to be sure that the only possible external access was via 
> SFTP.  You can't rely on just disabling services, because I have 
> known them to become enabled again after installing updates (thanks 
> MS!)
> 

Yes, I agree totally. We always put publicly accessible systems behind firewall.


      

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