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Restrict access for one usergroup via permissions

Posted on 2009-05-12
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Last Modified: 2013-12-16
I have a single user on a server of mine that I need to have them scp files to their directory where a script will then run, and take control/ownership of the files.  I do not want this user to even see other directories or move about.  I tried chroot jail before but that has security holes that you can drive a truck through.  However I'm having a real problem understanding, and getting permission restrictions to work.  I could chmod directory by directory? but then wouldn't I also lock out other users/ groups that need to run processes?

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Question by:Illyankesh
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Assisted Solution

by:omarfarid
omarfarid earned 400 total points
ID: 24371253
if your are using vsftpd then please see link below:

http://www.experts-exchange.com/OS/Linux/Q_23155804.html
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Assisted Solution

by:small_student
small_student earned 100 total points
ID: 24374145
To give him limited shell access you can use sftp and limited shell, check this

http://www.experts-exchange.com/OS/Linux/Administration/Q_24288180.html

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Author Comment

by:Illyankesh
ID: 24380558
Blegh tried your solution Omarfarid.... went through the conf file line by line, and after following your steps, and restarting vsftpd...I can still move around the file system with a user who is on the list to be denied....
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Expert Comment

by:omarfarid
ID: 24381358
can you post your conf file?
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Accepted Solution

by:
Illyankesh earned 0 total points
ID: 24381847
Here ya go.  What did I miss?
# Example config file /etc/vsftpd.conf

#

# The default compiled in settings are fairly paranoid. This sample file

# loosens things up a bit, to make the ftp daemon more usable.

# Please see vsftpd.conf.5 for all compiled in defaults.

#

# READ THIS: This example file is NOT an exhaustive list of vsftpd options.

# Please read the vsftpd.conf.5 manual page to get a full idea of vsftpd's

# capabilities.

#

#

# Run standalone?  vsftpd can run either from an inetd or as a standalone

# daemon started from an initscript.

listen=YES

#

# Run standalone with IPv6?

# Like the listen parameter, except vsftpd will listen on an IPv6 socket

# instead of an IPv4 one. This parameter and the listen parameter are mutually

# exclusive.

#listen_ipv6=YES

#

# Allow anonymous FTP? (Beware - allowed by default if you comment this out).

anonymous_enable=NO

#

# Uncomment this to allow local users to log in.

local_enable=YES

#

# Uncomment this to enable any form of FTP write command.

write_enable=YES

#

# Default umask for local users is 077. You may wish to change this to 022,

# if your users expect that (022 is used by most other ftpd's)

local_umask=022

#

# Uncomment this to allow the anonymous FTP user to upload files. This only

# has an effect if the above global write enable is activated. Also, you will

# obviously need to create a directory writable by the FTP user.

#anon_upload_enable=YES

#

# Uncomment this if you want the anonymous FTP user to be able to create

# new directories.

#anon_mkdir_write_enable=YES

#

# Activate directory messages - messages given to remote users when they

# go into a certain directory.

dirmessage_enable=YES

#

# Activate logging of uploads/downloads.

xferlog_enable=YES

#

# Make sure PORT transfer connections originate from port 20 (ftp-data).

connect_from_port_20=YES

#

# If you want, you can arrange for uploaded anonymous files to be owned by

# a different user. Note! Using "root" for uploaded files is not

# recommended!

chown_uploads=YES

chown_username=imperator

#

# You may override where the log file goes if you like. The default is shown

# below.

#xferlog_file=/var/log/vsftpd.log

#

# If you want, you can have your log file in standard ftpd xferlog format

#xferlog_std_format=YES

#

# You may change the default value for timing out an idle session.

#idle_session_timeout=600

#

# You may change the default value for timing out a data connection.

#data_connection_timeout=120

#

# It is recommended that you define on your system a unique user which the

# ftp server can use as a totally isolated and unprivileged user.

#nopriv_user=ftpsecure

#

# Enable this and the server will recognise asynchronous ABOR requests. Not

# recommended for security (the code is non-trivial). Not enabling it,

# however, may confuse older FTP clients.

#async_abor_enable=YES

#

# By default the server will pretend to allow ASCII mode but in fact ignore

# the request. Turn on the below options to have the server actually do ASCII

# mangling on files when in ASCII mode.

# Beware that on some FTP servers, ASCII support allows a denial of service

# attack (DoS) via the command "SIZE /big/file" in ASCII mode. vsftpd

# predicted this attack and has always been safe, reporting the size of the

# raw file.

# ASCII mangling is a horrible feature of the protocol.

#ascii_upload_enable=YES

#ascii_download_enable=YES

#

# You may fully customise the login banner string:

ftpd_banner=Welcome to the adversarial ftp service bribery welcomed.

#

# You may specify a file of disallowed anonymous e-mail addresses. Apparently

# useful for combatting certain DoS attacks.

#deny_email_enable=YES

# (default follows)

#banned_email_file=/etc/vsftpd.banned_emails

#

# You may restrict local users to their home directories.  See the FAQ for

# the possible risks in this before using chroot_local_user or

# chroot_list_enable below.

chroot_local_user=YES

#

# You may specify an explicit list of local users to chroot() to their home

# directory. If chroot_local_user is YES, then this list becomes a list of

# users to NOT chroot().

#chroot_list_enable=YES

# (default follows)

#chroot_list_file=/etc/vsftpd.chroot_list

#

# You may activate the "-R" option to the builtin ls. This is disabled by

# default to avoid remote users being able to cause excessive I/O on large

# sites. However, some broken FTP clients such as "ncftp" and "mirror" assume

# the presence of the "-R" option, so there is a strong case for enabling it.

#ls_recurse_enable=YES

#

#

# Debian customization

#

# Some of vsftpd's settings don't fit the Debian filesystem layout by

# default.  These settings are more Debian-friendly.

#

# This option should be the name of a directory which is empty.  Also, the

# directory should not be writable by the ftp user. This directory is used

# as a secure chroot() jail at times vsftpd does not require filesystem

# access.

secure_chroot_dir=/var/run/vsftpd

#

# This string is the name of the PAM service vsftpd will use.

pam_service_name=vsftpd

#

# This option specifies the location of the RSA certificate to use for SSL

# encrypted connections.

rsa_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem

# This option specifies the location of the RSA key to use for SSL

# encrypted connections.

rsa_private_key_file=/etc/ssl/private/ssl-cert-snakeoil.key

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Author Comment

by:Illyankesh
ID: 24415394
Figured out solution using
http://www.howtoforge.com/chrooted-ssh-sftp-tutorial-debian-lenny
and
http://www.fuscholberger.net/programs/ssh-scp-sftp-chroot-jail

The directory structure in the script is different than what is posted on the web, and another expert fixed the issue.
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