By default services that provide a remote shell, like ssh or telnet, or an interactive remote session for commands like sftp, allow a local user to change into any directory they have permissions for, and retrieve a copy of any file they have access to.
As a general security configuration this is unfortunate because there are many files and directories which are world-readable of necessity. For example here is me a non-root user on some remote CentOS box;
$ cd /etc
-bash-3.2$ ls -1
acpi
adjtime
aliases
...
e.g. I can access lots of stuff, that ideally you would want to restrict from some unknown user who you wish to provide local access to.
Here is me looking at all the local users configured in the /etc/passwd
file;
$ cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
...
Unix systems provide the chroot
command which allows you to reset the /
of the user to some directory in the filesystem hierarchy, where they cannot access "higher-up" files and directories.
However in your case, it would appropriate to provide a virtual chroot implemented by the remote shell service. sftp can be easily configured to restrict a local user to a specific subset of the filesystem using a configuration in the
hence in your case, you want to chroot
the adeveloper
user into the /var/www/html/website_abc
directory.
You can set a chroot directory for your user to confine them to the subdirectory /var/www/html/website_abc
like so in /etc/ssh/sshd_config
;
This stuff requires openssh-server later than 4.8?, so probably requires CentOS 6.2
Match Group sftp
ChrootDirectory %h
AllowTcpForwarding no
(not tested, see man sshd_config
to confirm syntax)
and then add those users to the sftp group;
groupadd sftp
usermod -d /var/www/html/website_abc adeveloper
usermod -G sftp adeveloper
Regarding shared keys
you should create an additional keypair for the adeveloper users, and send that to your consultant. (or alternatively, have them send your their public key and add it to the authorized_keys file for adeveloper
)
never give up your private key, thats why its called private ;-)
traditional ftp alternatives
vsftp/proftp etc also support chroot configurations, but in this modern day ssh based configurations are the normal way, and support for ftp is historical only.
there are a couple of links to tutorials here;
http://www.techrepublic.com/blog/opensource/chroot-users-with-openssh-an-easier-way-to-confine-users-to-their-home-directories/229
http://www.howtoforge.com/chrooted-ssh-sftp-tutorial-debian-lenny
Assuming that you've installed Apache and ProFTP from official Debian repositories, do the following,
$ chmod -R g+w /var/www/www.one.com /var/www/www.two.com
$ chown -R proftpd.www-data /var/www/www.one.com /var/www/www.two.com
The first command gives "write" permissions to the group and the second command changes the ownership of the docroots to user: "proftpd" and group: "www-data"
If this doesn't work, please check the "User" in /etc/proftpd/proftpd.conf and replace it that with proftpd
Best Answer
If you are using Ubuntu the Apache user will be www-data, but if you are using CentOS the webserver user will be Apache, so can you grep and see whether Apache user exist or not:
If the apache user exist you can use :