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CLI, OS

CentOS 7 Enterprise desktop setup

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These are my notes for standing up a CentOS 7 desktop in an enterprise environment.

Packages

Install the EPEL repository for a better experience:

sudo yum -y install epel-release

Desktop experience packages:

sudo yum -y install vlc libreoffice java gstreamer gstreamer1 gstreamer-ffmpeg gstreamer-plugins-good gstreamer-plugins-ugly gstreamer1-plugins-bad-freeworld gstreamer1-libav pidgin rhythmbox ffmpeg keepass xdotool ntfs-3g gvfs-fuse gvfs-smb fuse sshfs redshift-gtk stoken-gui stoken-cli

Additional packages that may come in handy

sudo yum -y install http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-5.el7.nux.noarch.rpm
sudo yum -y install libdvdcss gstreamer{,1}-plugins-ugly gstreamer-plugins-bad-nonfree gstreamer1-plugins-bad-freeworld libde265 x265

Enable ssh:

sudo systemctl enable sshd
sudo systemctl start sshd

Google Chrome

Paste into /etc/yum.repos.d/google-chrome.repo:

[google64]
name=Google - x86_64
baseurl=http://dl.google.com/linux/rpm/stable/x86_64
enabled=1
gpgcheck=1
gpgkey=https://dl-ssl.google.com/linux/linux_signing_key.pub
sudo yum -y install google-chrome-stable

Domain

It’s just easier to use PowerBroker Open from beyondtrust

sudo wget -O /etc/yum.repos.d/pbiso.repo http://repo.pbis.beyondtrust.com/yum/pbiso.repo
sudo yum -y install pbis-open

Cliff notes for joining the domain:

domainname=<your_domain_name>
domain_prefix=<your_domain_netbios_name>
domainaccount=<your_domain_admin_account

sudo domainjoin-cli join $domainname $domainaccount 
<enter password>

sudo /opt/pbis/bin/config UserDomainPrefix $domain_prefix
sudo /opt/pbis/bin/config AssumeDefaultDomain true
sudo /opt/pbis/bin/config LoginShellTemplate /bin/bash
sudo /opt/pbis/bin/config HomeDirTemplate %H/%U

Add domain admins to sudo, escaping spaces with a backlsash and replacing DOMAIN with your domain:

sudo visudo
%DOMAIN\\Domain\ Administrators ALL=(ALL) ALL

Reboot to make all changes go into effect.

Certificate

You might need to copy your domain’s CA certificate to your certificate trust store:

sudo cp <CA CERT FILENAME> /etc/pki/ca-trust/source/anchors/
sudo update-ca-trust

Drive mapping

I use a simple script to use gvfs-mount to mount network drives. Change suffix to match your domain and mounts to suit your needs.

#!/bin/bash
#Simple script to mount network drives on login

suffix=<DOMAIN_SUFFIX>
MOUNTS=(
	server1$suffix/folder1
	server2$suffix/folder2
        server3$suffix/folder3
)

for i in "${MOUNTS[@]}" 
do
	gvfs-mount "smb://$i"
done

Configure in gnome to run on startup:

Add the following to ~/.config/autostart/mount-drives.desktop, changing Exec= to the path of the above script.

[Desktop Entry]
Name=Mount network drives
GenericName=Mount network drives
Comment=Script to mount network drives
Exec=<location of mount script>
Terminal=false
Type=Application
X-GNOME-Autostart-enabled=true

Network Config

If you wish to add static IP and configure your DNS suffix (search domain) then run

nm-connection-editor

The other GUI for network configuration doesn’t have an option for search domains for some reason.

Smartcard

sudo yum -y install opensc pcsc-tools pcsc-lite

Be sure to install the drivers for your particular card reader. Mine came from here and here.

After installing you can test by starting pcscd and using pcsc_scan

sudo systemctl start pcscd
pcsc_scan

Vmware horizon view

Smartcard support

There is a problem with how the VMware View interacts with the opensc smartcard drivers shipped in popular Linux distributions such as CentOS and Ubuntu. View cannot load the drivers in the default configuration; therefore in order to get VMware View working with smartcards you need manually patch and compile the opensc package (thanks to this site for the information needed to do so.)

First, install the necessary development packages

sudo yum -y groupinstall "Development Tools"
sudo yum -y install openssl-devel pcsc-lite-devel

Next, download and extract opensc-0.13 from sourceforge:

wget http://downloads.sourceforge.net/project/opensc/OpenSC/opensc-0.13.0/opensc-0.13.0.tar.gz
tar zxvf opensc-0.13.0.tar.gz
cd opensc-0.13.0

Now we have to patch two specific files in the source before compiling:

echo "--- ./src/pkcs11/opensc-pkcs11.exports
 +++ ./src/pkcs11/opensc-pkcs11.exports
 @@ -1 +1,3 @@
  C_GetFunctionList
 +C_Initialize
 +C_Finalize
 --- ./src/pkcs11/pkcs11-spy.exports
 +++ ./src/pkcs11/pkcs11-spy.exports
 @@ -1 +1,3 @@
  C_GetFunctionList
 +C_Initialize
 +C_Finalize" > opensc.patch

patch -p1 -i opensc.patch

Next, compiling and installing:

./bootstrap
./configure
make
sudo make install

Assuming there were no errors, you can now link the compiled driver to the location VMware view expects it. Note: you must rename the library from opensc-pkcs11.so to libopensc-pkcs11.so for this to work (another lovely VMware bug)

sudo mkdir -p /usr/lib/vmware/view/pkcs11/
sudo ln -s /usr/local/lib/pkcs11/opensc-pkcs11.so /usr/lib/vmware/view/pkcs11/libopensc-pkcs11.so

Lync

Install the pidgin-sipe plugin as detailed here

sudo yum -y install pidgin pidgin-sipe

Choose “Office Communicator” as the protocol. Enter your e-mail address for the username, then go to the Advanced tab and check “Use single sign-on.”

On first run all contact names were missing. Per here, simply close and restart the application.

Gnome 3

Disable audible bell

Taken from here

Disable audible bell and enable visual bell with:

gsettings set org.gnome.desktop.wm.preferences audible-bell false
gsettings set org.gnome.desktop.wm.preferences visual-bell true

and change the type of the visual bell if you don’t need the fullscreen flash:

gsettings set org.gnome.desktop.wm.preferences visual-bell-type frame-flash

Extensions

If you can find your extension via yum it tends to work better than the gnome extension site. Make sure you’re using the correct shell version from the site:

gnome-shell --version
sudo yum -y install gnome-shell-extension-top-icons gnome-shell-extension-dash-to-dock

Other useful extensions:

backslide, multi monitors add-on , No topleft hot corner, Dropdown terminal, Media player indicator, Focus my window, Workspace indicator, Native window placement, Openweather, Panel osd, Dash to dock, Gpaste

RSA

For if you have the misfortune of being in an environment that uses RSA SecurID for two factor authentication, here is the official guide

Necessary packages to be installed:

sudo yum -y install selinux-policy-devel policycoreutils-devel
  1.  Download & extract PAM agent, cd to extracted directory 
    tar -xvf PAM-Agent*.tar
  2. Create /var/ace directory and place necessary files inside. Create sdopts.rec and add the IP address of the desktop. 
    mkdir /var/ace
cp sdconf.rec /var/ace
vi /var/ace/sdopts.rec
CLIENT_IP=<IP ADDRESS OF DESKTOP>
  3. Run the install_pam script and specify UDP authentication 
    ./install_pam.sh
  4.  Modify /etc/pam.d/password-auth to add the RSA authentication agent. Insert above pam_lsass.so smartcard_prompt try_first_pass line, then comment out pam_lsass.so smartcard_prompt try_first_pass line 
    auth required pam_securid.so
auth required pam_env.so
auth sufficient pam_lsass.so
  5. Add new system in RSA console: Access / Authentication Agents / Add new
  6. Test to make sure everything works: 
    /opt/pam/bin/64bit/acetest
OS

Troubleshoot RSA SecurID in CentOS 6

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Unexpected error from ACE/Agent API.

In following this guide for configuring a CentOS 6 system to authenticate with RSA SecurID I came across an unusual error message that had me scratching my head:

Unexpected error from ACE/Agent API.

The problem stemmed from having an incorrect value in the /var/ace/sdopts.rec file for CLIENT_IP. For some reason I had put the IP address of the RSA authentication server in there. CLIENT_IP is the IP address of the RSA client, or rather, the machine you’re working on. The client uses whatever’s in that file to report to the RSA server what its IP address is. If the RSA server gets an invalid IP response from the client, it won’t authenticate.

SELinux issues

Much blood and tears were shed in dealing with getting SELinux to exist harmoniously with RSA SecurID. The problem was exacerbated my the fact that there is a lot of half solutions and misinformation floating out there on the internet. This will hopefully help fix that.

The message entry does not exist for Message ID: 1001

At this point acetest worked beautifully but I could not use an RSA passcode to SSH into the system. Digging into the log revealed this error message:

sshd[2135]: ACEAGENT: The message entry does not exist for Message ID: 1001

Thanks to this post, I realized it was due to selinux. Modifying the selinux config information to allow /var/ace to be read, per the commands below, seemed to fix the issue.

setenforce 0
chcon -Rv --type=sshd_t /var/ace/
setenforce 1

But alas! The solution was not a very good one. The commands above have two problems with them: first, the chcon command is temporary and does not survive selinux policy relabels; second, it assigns the type sshd_t, which does allow SSH to access it, but revokes RSA SecurID’s ability to write to the directory. This is a problem if you ever need to clear node secrets. The server will initiate the wipe but the client will not be able to modify that directory, resulting in node secret mismatches.

I finally decided to RTFM and landed on this documentation page, which explained the issue I was having: selinux mislabeling. The proper solution to this problem is use a label that both SecurID and SSHD can write / read to. Thanks to this SELinux Manpage (it really pays to RTFM!) I discovered that the label I want is var_auth_t (the default label applied when creating /var/ace is var_t, which SSH can’t read.) 

To survive relabeling, use the semanage command, which is not installed by default. Thanks to this site I learned I must install policycoreutils-pithon:

yum install policycoreutils-python

Once semanage is installed, use it to change the label for /var/ace and everything inside it to var_auth_t, then apply the changes with restorecon:

semanage fcontext -a -t var_auth_t "/var/ace(/.*)?"
restorecon -R -v /var/ace

Finally, both RSA SecurID and OpenSSH can read what they need to and authentication is successful.

First acetest succeeds but subsequent ones fail

If you followed the bad advice of relabeling /var/ace to sshd_t you might run across a very frustrating issue where acetest would succeed, but any attempts to SSH into the box or even run acetest again would fail. The error message on the RSA SecurID server was

Node secret mismatch: cleared on server but not on agent

The problem is due to the improper SELinux labeling mentioned above. The fix is the same:

yum install policycoreutils-python
semanage fcontext -a -t var_auth_t "/var/ace(/.*)?"
restorecon -R -v /var/ace

SSH access denied even with successful acetest

If acetest succeeds and you’ve loaded the module into PAM but still get access denied, it could be due to your SSH configuration. Ensure the following options are set:

ChallengeResponseAuthentication yes 
UsePrivilegeSeparation no

Victory.