Tag Archives: Linux

Introduction

A Virtual Private Network establishes a secure encrypted connection between your system and a server. It allows you to connect to an untrusted network and tunnel all your network traffic so that it emerges from the VPN server to its destination. In this howto, we will configure the OpenVPN client to connect to the VPN servers hosted by Private Internet Access.

I’ve chosen to use Private Internet Access only because I already have an account with them and they support the OpenVPN client to connect to their VPN servers. I’m sure other VPN service providers would work the same way.

Although I initially tested this on Raspbian Stretch on a Raspberry Pi, I have since used the same steps on Debian Stretch and achieved the same results.

Installing all the prerequisites

To accomplish this task we are going to need to install openvpn, unzip, wget, curl and openresolv. We can do this by using the following command:


apt -y install openvpn unzip wget curl openresolv

Setting up the directory structure

Just to keep things organized we will create a set of directories. This will help if we ever need to alter the configuration by only requiring the change of a couple of linked files. First we need to switch to “/etc/openvpn/client directory”.

cd /etc/openvpn/client

Once there we create several directories by issuing the following commands:

mkdir certs-available
mkdir confs-available
mkdir login-available
mkdir certs-enabled
mkdir login-enabled
mkdir vpn-bundles

Setting up all the configurations

Private Internet Access (as well as other VPN providers) provide configuration bundles for the OpenVPN default client. We are going to download those configurations, alter them a bit and use them to connect to the PIA VPN server as soon as our system finishes booting up.

Switch to the directory we created to store the configuration bundle by issuing the following command:

cd /etc/openvpn/client/vpn-bundles

Once in /etc/openvpn/client/vpn-bundles we can proceed to download the configuration bundle with wget by issuing the following:

wget https://www.privateinternetaccess.com/openvpn/openvpn.zip

Now that we have the zipped file with all the configurations we need to unzip it by using the following command:

unzip openvpn.zip -d "$(date +"%d-%m-%Y")"-PIA-openvpn

This command will unzip the openvpn.zip file into a directory whose name starts with the date followed by “-PIA-openvpn”. We are doing this so that in the future if there is a need to download a new set of configurations we can easily tell which directory contains the newly downloaded ones.

Once the file is unzipped we can start moving the configurations to the directories we previously created.

cd "$(date +"%d-%m-%Y")"-PIA-openvpn
mkdir /etc/openvpn/client/certs-available/PIA
cp *.crt /etc/openvpn/client/certs-available/PIA/
cp *.pem /etc/openvpn/client/certs-available/PIA/
mkdir /etc/openvpn/client/confs-available/PIA
cp *.ovpn /etc/openvpn/client/confs-available/PIA/

Because we want the OpenVPN client to start without user interaction, we need to add a couple of settings to all VPN configuration files we just downloaded. Change to the directory where we stored them by issuing the following command:

cd /etc/openvpn/client/confs-available/PIA

We need to alter all the configuration files so that they can get the user name and password from a file named “login” located at “/etc/openvpn/client/login-enabled/”. This can be accomplished by issuing the following command:

sed -i 's/auth-user-pass/auth-user-pass \/etc\/openvpn\/client\/login-enabled\/login/g' *.ovpn

We also need to add the following settings to all the configuration files. These settings deal with changing the DNS servers in order to prevent DNS leaks when the VPN is up.

script-security 2
up /etc/openvpn/update-resolv-conf
down /etc/openvpn/update-resolv-conf
down-pre

Going into each file to add the aforementioned settings would be too tedious, it is better to use a small script that goes into each file and adds the settings. The script is simple, just create a file named add_vpn_settings.sh with the following content:

#/bin/bash
cd /etc/openvpn/client/confs-available/PIA
for file in *
 do 
     echo "script-security 2" >> "$file"
     echo "up /etc/openvpn/update-resolv-conf" >> "$file"
     echo "down /etc/openvpn/update-resolv-conf" >> "$file"
     echo "down-pre" >> "$file"
 done

Next step is to make executable by issuing the following:

chmod +x add_vpn_settings.sh

And finally we run the add_vpn_settings.sh script by issuing:

./add_vpn_settings.sh

Now we need to backup the original update-resolv-conf file, this is because we are going to use a replacement that is better able to update the DNS servers in /etc/resolv.conf when they are pushed in by the VPN server. We can do this be issuing the following commands:

cd /etc/openvpn
mv update-resolv-conf update-resolv-conf-ORIG

If we ever need to return to the default script we just rename “update-resolv-conf-ORIG” back to “update-resolv-conf “.

Next we need to download the replacement update-resolv-conf file from https://github.com/masterkorp/openvpn-update-resolv-conf. We can issue the following commands to accomplish this:

cd /etc/openvpn
wget https://github.com/masterkorp/openvpn-update-resolv-conf/raw/master/update-resolv-conf.sh

Now we rename it and make it executable:

mv update-resolv-conf.sh update-resolv-conf
chown root:root update-resolv-conf
chmod 555 update-resolv-conf

Next we need to create a the file that contains the actual username and password for the PIA VPN server. Issuing the following three commands should do the job:

cd /etc/openvpn/client/login-available
echo "YOUR_PIA_USERNAME" > PIA-Login
echo "YOUR_PIA_PASSWORD" >> PIA-Login

Now we create a link from /etc/openvpn/client/login-available to /etc/openvpn/client/login-enabled/login by issuing the following:

ln -s /etc/openvpn/client/login-available/PIA-Login /etc/openvpn/client/login-enabled/login

Finally we link one of the configurations available to be the default one (I’ve used the UK London configuration as an example below, you can use whichever configuration you desire).

ln -s /etc/openvpn/client/confs-available/PIA/UK\ London.ovpn /etc/openvpn/default.conf

After a reboot, the openvpn client should be up and everything should be flowing through the vpn tunnel.

How-tos, Linux

Setting up a mining system with xmr-stak built from source and Ubuntu 16.04

January 21, 2018 d h

If using an Nvidia GPU, install the Nvidia CUDA toolkit:

Download installer type “deb(network)” from:

https://developer.nvidia.com/cuda-downloads?target_os=Linux&target_arch=x86_64&target_distro=Ubuntu&target_version=1604

To install issue the following commands:

$ sudo dpkg -i cuda-repo-ubuntu1604_9.1.85-1_amd64.deb
$ sudo apt-key adv --fetch-keys http://developer.download.nvidia.com/compute/cuda/repos/ubuntu1604/x86_64/7fa2af80.pub
$ sudo apt-get update
$ sudo apt-get install cuda

Editing the enviroment to include the CUDA path:

$ sudo nano /etc/environment

Find the PATH variable and include the /usr/local/cuda-9.1/bin folder at the end of the string.

Save the file and reboot.

If using and AMG GPU, install AMD APP SDK 3.0:

Download and install the latest version from:

http://developer.amd.com/amd-accelerated-parallel-processing-app-sdk/

Untar the SDK to a location of your choice.

Decompress the file wit the following command:

$ tar -xvjf AMD-APP-SDKInstaller-v<3.0.x.y>-GA-linux64.tar.bz2

Run the installer:

$ sudo ./AMD-APP-SDKInstaller-v<3.0.x.y>-GA-linux64.sh

To fix libOpenCL issue:

$ cd $AMDAPPSDKROOT/lib/x86_64
$ sudo ln -sf sdk/libOpenCL.so.1 libOpenCL.so

then logout and login again.

Installing amdgpu-pro

Download the latest package from:

https://support.amd.com/en-us/kb-articles/Pages/AMDGPU-PRO-Driver-for-Linux-Release-Notes.aspx

Decompress the file wit the following command:

$ tar -xJvf amdgpu-pro-17.40-492261.tar.xz
$ cd amdgpu-pro-17.40-492261
$ sudo ./amd-pro-install -y

Reference:
https://linuxconfig.org/install-amdgpu-pro-16-50-on-ubuntu-16-04-xenial-xerus-linux

Building xmr-stak from source

Install all dependencies:

$ sudo apt install git libmicrohttpd-dev libssl-dev cmake build-essential libhwloc-dev

Create a directory for the source files and clone the source:

$ mkdir GIT-sources
$ cd GIT-sources
$ git clone https://github.com/fireice-uk/xmr-stak.git

Create a build directory:

$ mkdir xmr-stak/build
$ cd xmr-stak/build

Configuring and building xmr-stak

If building xmr-stak for CPU only mining and without http server support, use the following cmake flags:

$ cmake .. -DCUDA_ENABLE=FALSE -DOpenCL_ENABLE=FALSE -DMICROHTTPD_ENABLE=FALSE

If building xmr-stak for AMD GPU mining and CPU mining, use the following cmake flags:

$ cmake .. -DCUDA_ENABLE=FALSE

If building xmr-stak for Nvidia GPU and CPU mining, use the following cmake flags:

$ cmake .. -DOpenCL_ENABLE=FALSE

If building for all (AMD GPU, Nvidia GPU and CPU mining)

$ cmake ..

After cmake finishes, execute the following to build:

$ make -j4 install

Final system configurations

If using GPU mining (Nvidia GPU or AMD GPU), ensure the user you will use to mine is part of the video group in /etc/group

$ sudo usermod -a -G video $LOGNAME

Enabling Large Page Support for AMDGPU-PRO

Edit /etc/default/grub and add GRUB_CMDLINE_LINUX=”amdgpu.vm_fragment_size=9″

After editing ggrub, do:
$ sudo update-grub
$ sudo reboot

Configuring Large Page Support for Operating system (applies to all GPUs and CPUs)

Create a file named 98-HugePages-miner.conf in /etc/sysctl.d with the following content:

############################
vm.nr_hugepages=128
############################

Add the following lines to /etc/security/limits.conf (where “miner” is the name of your mining account):

############################
miner soft memlock 262144
miner hard memlock 262144
############################

Then reboot with:

$ reboot

You will find the xmr-stak binary in ~/GIT-sources/xmr-stak/build/bin. Run xmr-stak and follow the prompts to begin mining.

How-tos, Linux

Building a Root CA and an Intermediate CA using OpenSSL and Debian Stretch

December 27, 2017 d h

A bit of background

A Root Certificate Authority is used to issue digital certificates to servers, clients or users. It generates digital certificates that certify the ownership of a public key, allowing others to trust the certificate.

An Intermediate Certificate is a subordinate certificate issued by a Root certificate authority for the purpose of issuing certificates. This creates a certificate chain that begins in the Root CA, through the intermediate and ending in the issued certificate. This establishes a chain of trust that can verify the validity of a certificate.

In this post, we will step through the process of creating a Root CA, then an Intermediate CA and finally sign digital certificates for a server. A bit of warning, this setup should be sufficient for a homelab or a small local setup; you should not use this as a production service.

Prepare to build

Install Debian Stretch, the minimum should suffice. There is no need any GUI. Install SSH for ease of administration and to transfer you certificates securely out.

Make sure that the Fully Qualified Domain Name of the computer is set correctly.

Make sure your time zone is correctly set.

Make sure the time and date are correctly set.

If you wish you can install ntp to ensure time is always correct.

# apt install ntp

Download the following configuration files:

openssl_root.cnf

openssl_intermediate.cnf

openssl_csr_san.cnf

After download rename all of them by dropping the “.txt” extension.

Creating the Root CA

Create the directory structure for the Root CA:

# mkdir /root/ca
# cd /root/ca
# mkdir newcerts certs crl private requests

While at /root/ca we should also create “index.txt” file for OpenSSL to keep track of all signed certificates and the “serial” file to give the start point for each signed certificate’s serial number. This can be accomplished by doing the following:

# cd /root/ca
# touch index.txt
# touch index.txt.attr
# echo '1000' > serial

Copy openssl_root.cnf to /root/ca, edit it and look for the following entries:

# The root key and root certificate.
private_key = $dir/private/ca.DOMAINNAME.key.pem
certificate = $dir/certs/ca.DOMAINNAME.cert.pem

# For certificate revocation lists.
crlnumber = $dir/crlnumber
crl = $dir/crl/ca.DOMAINNAME.crl.pem
crl_extensions = crl_ext
default_crl_days = 30

Change DOMAINNAME to something that matches the domain of your network, this isn’t strictly necessary but it makes for a more customized naming convention.

Generate the Root private key

(change DOMAINNAME to match what you used in the openssl_root.cnf):

# cd /root/ca
# openssl genrsa -aes256 -out private/ca.DOMAINNAME.key.pem 4096

Signing the Root Certificate

Use the root private key to sign the root certificate.
(change DOMAINNAME to match what you used in the openssl_root.cnf):

# openssl req -config openssl_root.cnf -new -x509 -sha512 -extensions v3_ca -key /root/ca/private/ca.DOMAINNAME.key.pem -out /root/ca/certs/ca.DOMAINNAME.crt.pem -days 3650 -set_serial 0

Ensure that when filling out the “Common Name” variable that you use the CA server + Domain name of the network

Creating an Intermediate Certificate Authority

Create a directory to separate the intermediary files from our root configuration

# mkdir /root/ca/intermediate

Also all the directories and files needed to support (similar to the ones we created for the Root CA):

# cd /root/ca/intermediate
# mkdir certs newcerts crl csr private
# touch index.txt
# touch index.txt.attr
# echo 1000 > /root/ca/intermediate/crlnumber
# echo '1234' > serial

Copy openssl_intermediate.cnf to /root/ca/intermediate, edit it and look for the following entries:

# The root key and root certificate.
private_key = $dir/private/int.DOMAINNAME.key.pem
certificate = $dir/certs/int.DOMAINNAME.crt.pem

# For certificate revocation lists.
crlnumber = $dir/crlnumber
crl = $dir/crl/int.DOMAINNAME.crl.pem
crl_extensions = crl_ext
default_crl_days = 30

Change DOMAINNAME to the same thing that you used in openssl_root.cnf

Creating the private key and certificate signing request for the Intermediate CA

(change DOMAINNAME to the value you’ve been using so far)

# cd /root/ca
# openssl req -config /root/ca/intermediate/openssl_intermediate.cnf -new -newkey rsa:4096 -keyout /root/ca/intermediate/private/int.DOMAINNAME.key.pem -out /root/ca/intermediate/csr/int.DOMAINNAME.csr

Creating the intermediate certificate

(change DOMAINNAME to the value you’ve been using so far)

# openssl ca -config /root/ca/openssl_root.cnf -extensions v3_intermediate_ca -days 3650 -notext -md sha512 -in /root/ca/intermediate/csr/int.DOMAINNAME.csr -out /root/ca/intermediate/certs/int.DOMAINNAME.crt.pem

** Notice that the root CA configurtion (openssl_root.cnf) is used.

Creating the certificate chain

# cd /root/ca
# cat intermediate/certs/int.DOMAINNAME.crt.pem certs/ca.DOMAINNAME.crt.pem > intermediate/certs/chain.DOMAINNAME.crt.pem

What are all these files for?

So now that you have created all these files, which ones are the ones you need?

In /root/ca/certs, ca.DOMAINNAME.crt.pem is the Root CA certificate.
In /root/ca/intermediate/certs, int.DOMAINNAME.crt.pem is the Intermediate CA certificate.
In /root/ca/intermediate/certs, chain.DOMAINNAME.crt.pem is the concatenation of the Root CA certificate and the Intermediate CA certificate.

Creating server certificates

Copy openssl_csr_san.cnf to /root/ca/intermediate, edit it and change the entries under [alt_names] so that the DNS.* entries match the Fully Qualified Domain Name of the server you wish to create a certificate for. This will create a certificate with embedded Subject Alternative Name (SANs), so no more warnings from Chrome about NET::ERR_CERT_AUTHORITY_INVALID.

Creating the key and certificate signing request

(change “www.example.com” to your server’s FQDN)

# cd /root/ca
# openssl req -out intermediate/csr/www.example.com.csr.pem -newkey rsa:2048 -nodes -keyout intermediate/private/www.example.com.key.pem -config intermediate/openssl_csr_san.cnf

Creating the certificate by signing the signing request with the intermediate CA

(change “www.example.com” to your server’s FQDN)

# cd /root/ca
# openssl ca -config intermediate/openssl_intermediate.cnf -extensions server_cert -days 3750 -notext -md sha512 -in intermediate/csr/www.example.com.csr.pem -out intermediate/certs/www.example.com.crt.pem

In /root/ca/intermediate/certs you should now have a certificate for use in the server (www.example.com in the case of the example).

Creating a combined certificate for use with Apache server

(change “www.example.com” to your server’s FQDN)

# openssl pkcs12 -inkey www.example.com.key.pem -in www.example.com.crt.pem -export -out www.example.com.combined.pfx
# openssl pkcs12 -in www.example.com.combined.pfx -nodes -out www.example.com.combined.crt