rsync - Dec 2004 - Restricting rsync over ssh

Hi
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.

If this is ok, i will code the dummy-shell and put it online for those 
who would like to do similar things...

Thanks in advance, Bob

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/


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