Restricting rsync over ssh

[Bob]

I would like to avoid using chroot because it implies my dummy-shell 
must run in suid root. Furthermore, it forces to create a jail with the 
binaries and libraries inside. I was thinking to this solution to avoid 
doing this. Do you think there are some security issues using realpath 
instead of chroot ?

Bob

Dmitry V. Levin wrote:

>Hi,
>
>On Tue, Dec 28, 2004 at 04:53:45PM +0100, Bob wrote:
>  
>
>>I have very special needs and i wanted to use rsync over ssh. I don't 
>>know if a solution already exists for what i want to do. I want to 
>>provide rsync over ssh to my users. Howevern i want to have the 
>>following limitations :
>>1. No shell access
>>2. Limitting users to their home directories
>>
>>I was thinking to the folowing solution, but i don't know if it is 
>>secure enough :
>>Create a dummy-shell sor ssh login that only allow the rsync --server 
>>--sender command. Then i get the path of the wanted files, and i appened 
>>it to the home directory of the user. Ex : the user requests /test, i 
>>give him : /home/usrname/test
>>Then i uses the realpath function to canonicalize the path and i check 
>>that it really begins with /home/usrname to prevent users from getting 
>>files outside of their home directory.
>>I execute the rsync command with the new built path...
>>
>>I think this should work but i would like to know what do you think 
>>about security.
>>    
>>
>
>Use chroot(2) to get more robust solution.
>See also ftp://ftp.altlinux.org/pub/people/ldv/rshell/
>
>
>  
>