All posts by nicholas

CLI

mountpoint check script

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I have a few NFS mounts that I want to be working at all times. If there is a power outage, sometimes NFS clients come up before the NFS server does, and thus the mounts are not there. I wrote a quick little bash script to fix this utilizing the mountpoint command.

Behold (Change the mountpoint(s) to the one you want to monitor.)

#!/bin/bash
#Simple bash script to check mount points and re-mount them if they're not mounted
#Authored by Nick Jepspon 8/11/2019

### Variables ###
# Changes these to suit your needs

MOUNTPOINTS=(/mnt/1 /mnt/2 /mnt/3)  #space separated list of mountpoints to monitor

### End Variables ###


for mount in $MOUNTPOINTS 
do
    if  ! mountpoint -q $mount
    then
        echo "$mount is not mounted, attempting to mount."
        mount $mount
    fi
    #otherwise do nothing
done

I have this set as a cronjob running every 5 minutes

*/5 * * * * /mountcheck.sh

Now the system will continually try to mount the specified folder if it isn’t already mounted.

CLI, Networking

OPENVPN site to site vpn between USG and openwrt

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A new firewall means a new site to site VPN configuration. My current iteration of this is a USG Pro 4 serving as an OpenVPN server and a Netgear Nighthawk R8000 serving as a VPN client joining their two networks together.

First, I had to wrap my head around some concepts. To set this up you need three sets of certificates and a DH file:

  • CA: To generate and validate certificates
  • Server: To encrypt/decrypt traffic for the Server
  • Client: To encrypt/decrypt traffic from the Client
  • DH: Not a certificate but still needed by the server for encryption

The server and client will also need openvpn configurations containing matching encryption/hashing methods, CA public key, and protocol/port settings.

Generate certificates

If you already have PKI infrastructure in place you simply need to generate two sets of keys and a DH file for the server/client to use. If you don’t, the easy-rsa project comes to the rescue. This tutorial uses easy-rsa version 3.

I didn’t want to generate the certificates on my firewall so I picked a Debian system to do the certificate generation. First, install easy-rsa:

sudo apt install easy-rsa

In Debian easy-rsa is installed to /usr/share/easy-rsa/

Optional: Set desired variables by moving /usr/share/easy-rsa/vars.example to /usr/share/easy-rsa/vars and un-commenting / editing to suit your needs (in my case I like to extend the life of my certificates beyond two years.)

Next, create your PKI and generate CA certificates:

/usr/share/easy-rsa/easyrsa init-pki
/usr/share/easy-rsa/easyrsa build-ca

Now create your DH file. Grab a cup of coffee for this one, it can take up to ten minutes to complete:

/usr/share/easy-rsa/easyrsa gen-dh

Then create your server & client certificates. For this guide we are calling the server ovpn-server and the client ovpn-client

#For the server
/usr/share/easy-rsa/easyrsa gen-req ovpn-server nopass 
/usr/share/easy-rsa/easyrsa sign-req server ovpn-server

#For the client
/usr/share/easy-rsa/easyrsa gen-req ovpn-client nopass
/usr/share/easy-rsa/easyrsa sign-req client ovpn-client

You will be asked for a common name. Remember what you put here, you will need it later. If you just hit enter and accept the default the common name will match what was passed in the above commands (ovpn-server for the server certificate and ovpn-client for the client certificate.)

Lastly, copy these files to their respective hosts:

USG Server: CA, Server key & cert, and DH file. (substitute with IP of your device)

scp pki/dh.pem pki/ca.crt pki/private/ovpn-server.key  pki/issued/ovpn-server.crt admin@IP_OF_YOUR_USG:/config/auth/

OpenWRT Client: Client key & cert, and CA cert:

scp pki/private/ovpn-client.key pki/issued/ovpn-client.crt pki/ca.crt root@IP_OF_YOUR_OPENWRT:/etc/config/

USG: VPN Server

Documentation for the EdgeRouter is much easier to find than for the USG. Since they use the same operating system I based this off of this guide from Logan Marchione for the EdgeRouter. SSH into your USG and issue the following, substituting the $variables with the values you desire for your network.

Explanation of variables:

VPN_SUBNET: Used for VPN communication. Must be different from both server and client subnets.
SERVER_SUBNET: Subnet on server side you wish to pass to client network
VPN_PORT: Change this to desired listening port for the OpenVPN server
REMOTE_SUBNET: Subnet on client side you wish to pass to server network
REMOTE_NETMASK: Netmask of client subnet
REMOTE_VPN_IP: Static IP you wish to give the client on the VPN subnet.
REMOTE_CERT_NAME: Common name given to client certificate generated previously.

Replace $variables below before pasting into USG terminal:

configure
#OpenVPN config
set interfaces openvpn vtun0
set interfaces openvpn vtun0 description "OpenVPN Site to Site"
set interfaces openvpn vtun0 mode server
set interfaces openvpn vtun0 encryption aes256
set interfaces openvpn vtun0 hash sha256
set interfaces openvpn vtun0 server subnet $VPN_SUBNET
set interfaces openvpn vtun0 server push-route $SERVER_SUBNET
set interfaces openvpn vtun0 tls ca-cert-file /config/auth/ca.crt
set interfaces openvpn vtun0 tls cert-file /config/auth/ovpn-client.crt
set interfaces openvpn vtun0 tls key-file /config/auth/ovpn-client.key
set interfaces openvpn vtun0 tls dh-file /config/auth/dh.pem
set interfaces openvpn vtun0 openvpn-option "--port $VPN_PORT"
set interfaces openvpn vtun0 openvpn-option --tls-server
set interfaces openvpn vtun0 openvpn-option "--comp-lzo yes"
set interfaces openvpn vtun0 openvpn-option --persist-key
set interfaces openvpn vtun0 openvpn-option --persist-tun
set interfaces openvpn vtun0 openvpn-option "--keepalive 10 120"
set interfaces openvpn vtun0 openvpn-option "--user nobody"
set interfaces openvpn vtun0 openvpn-option "--group nogroup"
set interfaces openvpn vtun0 openvpn-option "--route $REMOTE_SUBNET $REMOTE_NETMASK $REMOTE_VPN_IP"
set interfaces openvpn vtun0 server client $REMOTE_CERT_NAME ip $REMOTE_VPN_IP
set interfaces openvpn vtun0 server client $REMOTE_CERT_NAME subnet $REMOTE_SUBNET $REMOTE_NETMASK

#Firewall config
set firewall name WAN_LOCAL rule 50 action accept
set firewall name WAN_LOCAL rule 50 description "OpenVPN Site to Site"
set firewall name WAN_LOCAL rule 50 destination port $VPN_PORT
set firewall name WAN_LOCAL rule 50 log enable
set firewall name WAN_LOCAL rule 50 protocol udp
commit

If the code above commits successfully, the next step is to add the config to config.gateway.json. The USG’s config is managed by its Unifi controller, so for any of the changes made above to stick we must copy them to /usr/lib/unifi/data/sites/default/config.gateway.json on the controller (create the file if it doesn’t already exist.)

A quick shortcut is to run the mca-ctrl -t dump-cfg command, then parse out the parts you want to go into config.gateway.json as outlined in the UniFi documentation. For the lazy, here is the config.gateway.json generated from the above commands (be sure to modify $variables to suit your needs.)

{
  "firewall": {
    "WAN_LOCAL": {
      "rule": {
        "50": {
          "action": "accept",
          "description": "OpenVPN Site to Site",
          "destination": {
            "port": "$VPN_PORT"
          },
          "log": "enable",
          "protocol": "udp"
        }
      }
    }
  },
  "interfaces": {
    "openvpn": {
      "vtun0": {
        "description": "OpenVPN Site to Site",
        "encryption": "aes256",
        "hash": "sha256",
        "mode": "server",
        "openvpn-option": [
          "--port $VPN_PORT",
          "--tls-server",
          "--comp-lzo yes",
          "--persist-key",
          "--persist-tun",
          "--keepalive 10 120",
          "--user nobody",
          "--group nogroup",
          "--route $REMOTE_SUBNET $REMOTE_NETMASK $REMOTE_VPN_IP"
        ],
        "server": {
          "client": {
            "$REMOTE_CERT_NAME": {
              "ip": "$REMOTE_VPN_IP",
              "subnet": [
                "$REMOTE_SUBNET $REMOTE_NETMASK"
              ]
            }
          },
          "push-route": [
            "$SERVER_SUBNET"
          ],
          "subnet": "$VPN_SUBNET"
        },
        "tls": {
          "ca-cert-file": "/config/auth/ca.crt",
          "cert-file": "/config/auth/ovpn-client.crt",
          "dh-file": "/config/auth/dh.pem",
          "key-file": "/config/auth/ovpn-client.key"
        }
      }
    }
  }
}

OpenWRT: VPN client

Configuration is doable from the GUI but I found much easier with the command line. I got a lot of the configuration from this gist from braian87b

Install openvpn and the luci-app-openvpn packages:

opkg update
opkg install openvpn luci-app-openvpn

OpenVPN config files are located in /etc/config. In addition to the certificates we copied there earlier, we will also want to copy the openvpn client configuration to that directory.

Here is the config file matching the configuration generated above. Again, remember to replace $variables with your config matching what was generated above. Save it to /etc/config/site2site.conf

#/etc/config/site2site.conf
client
dev tun
proto udp
remote $DNS_OR_IP_OF_USG_OPENVPN_SERVER $VPN_PORT
cipher AES-256-CBC
auth SHA256
resolv-retry infinite
nobind
comp-lzo yes
persist-key
persist-tun
verb 3
ca /etc/config/ca.crt
cert /etc/config/ovpn-client.crt
key /etc/config/ovpn-client.key
remote-cert-tls server

With the openvpn config file, client certificate & key, and CA certificate we are ready to configure firewall rules and instruct the router to initiate the VPN connection.

# a new OpenVPN instance:
uci set openvpn.site2site=openvpn
uci set openvpn.site2site.enabled='1'
uci set openvpn.site2site.config='/etc/config/site2site.conf'

# a new network interface for tun:
uci set network.site2sitevpn=interface
uci set network.site2sitevpn.proto='none' #dhcp #none
uci set network.site2sitevpn.ifname='tun0'

# a new firewall zone (for VPN):
uci add firewall zone
uci set firewall.@zone[-1].name='vpn'
uci set firewall.@zone[-1].input='ACCEPT'
uci set firewall.@zone[-1].output='ACCEPT'
uci set firewall.@zone[-1].forward='ACCEPT'
uci set firewall.@zone[-1].masq='1'
uci set firewall.@zone[-1].mtu_fix='1'
uci add_list firewall.@zone[-1].network='site2sitevpn'

# enable forwarding from LAN to VPN:
uci add firewall forwarding
uci set firewall.@forwarding[-1].src='lan'
uci set firewall.@forwarding[-1].dest='vpn'

# Finally, you should commit UCI changes:
uci commit

Monitor VPN connection progress by using logread. If all goes well you will see the successful connection established message. If not, you’ll be able to get an idea of what’s wrong.

logread -f

If all goes well you’ll now have a bidirectional VPN between your two sites; however, traffic from the server’s subnet going directly to the client router itself (the OpenWRT device’s IP) will be considered as coming from the WAN interface and will be blocked. If you need to access the OpenWRT device directly from the USG’s subnet, you’ll need to add a firewall rule allowing it to do so:

uci add firewall rule
uci set firewall.@rule[-1]=rule
uci set firewall.@rule[-1].enabled='1'
uci set firewall.@rule[-1].target='ACCEPT'
uci set firewall.@rule[-1].src='wan'
uci set firewall.@rule[-1].name='Allow VPN to access router'
uci set firewall.@rule[-1].src_ip='$SERVER_SUBNET'
uci set firewall.@rule[-1].dest_ip='$INTERNALL_IP_OF_OPENWRT_ROUTER'
uci commit

Troubleshooting

One-sided VPN

I fought for some time with the fact that the VPN was established, but only traffic going from the Client network to the Server network would work. Traffic from the OpenVPN server subnet to the OpenVPN client subnet would simply hang and not work.

I finally found on the ubiquiti forums that this is due to default OpenVPN behavior of restricting traffic from the server subnet to the client subnet (see the OpenVPN how-to for more information.) The solution is to add lines in the server config informing it of the client network and to allow traffic to it. Below is an example USG config allowing informing it of remote subnet 192.168.230/24 and assigning the Client an IP of 10.0.76.253:

set interfaces openvpn vtun5 server client client1 ip 10.0.76.253
set interfaces openvpn vtun5 server client client1 subnet 192.168.230.0/24

VPN status stays “stopped” in OpenWRT

The best way to troubleshoot is to look at the logs in realtime. SSH to the OpenWRT router and run the command “logread -f” then try to initiate the connection again. The errors there will point you to the problem.

CLI, OS

zfs drive removal ‘part of active pool’ fix

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Occasionally I will manually offline a disk in my ZFS pool for one reason or another. Annoyingly I will sometimes get this error when I try to online that same disk back into the pool:

cannot online /dev/sda: cannot relabel '/dev/sda': unable to read disk capacity

The fix, thankfully, is fairly simple. Simply run the following command (make double sure you’re doing it on the correct device!)

sudo wipefs -a <DEVICE>

After I ran that command ZFS automatically picked the disk back and resilvered it into the pool.

Thanks to this superuser.com discussion for the advice!

CLI, Hardware, Networking

Automate USG config deploy with Ubiquiti API in Bash

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I have a new Ubiquiti Unifi Security Gateway Pro 4 which is pretty neat; however, the Unifi web interface is pretty limited. Most advanced firewall functions must be configured outside of the GUI. One must create a .json file with the configuration they need, copy that file to the Unifi controller, and then force a provision of the gateway to get it to pick up the new config.

I wanted a way to automate this process but very frustratingly Ubiquiti hasn’t documented their Unifi Controller API. I had to resort to reverse engineering their API by using my browser’s developer console to figure out which API calls were needed to do what I wanted. I then took the API functions from https://dl.ui.com/unifi/5.10.25/unifi_sh_api (the current unifi controller software download link which has unifi_sh_api) and embedded them into a bash script. Thanks to this forum post for the information on how to do this.

This bash script copies the specified config file to the Unifi controller via SCP, then uses curl to issue the API call to tell the controller to force a provision to the device having the supplied mac address. 

#!/bin/bash
# Written by Nick Jeppson 08/01/2019
# Inspired by posts made from ubiquiti forums: https://community.ui.com/questions/API/82a3a9c7-60da-4ec2-a4d1-cac68e86b53c
# API interface functions taken from unifi_sh_api shipped with controller version 5.10.25, https://dl.ui.com/unifi/5.10.25/unifi_sh_api
#
# This bash script copies the specified config file to the Unifi controller via SCP
# It then uses curl to issue an API call to tell the controller to force a provision to the device with the supplied mac address. 

#### BEGIN VARIABLES ####
#Fill out to match your environment

gateway_mac="12:34:56:78:90:ab" #MAC address of the gateway you wish to manage
config_file="your_config_file.json"   #Path to config file
unifi_server="unifi_server_name"         #Name/IP of unifi controller server
unifi_gateway_path="/usr/lib/unifi/data/sites/default/config.gateway.json"    #Path to config.gateway.json on the controller
ssh_user="root"                 #User to SSH to controller as
username="unifi_admin_username"             #Unifi username
password="unifi_admin_password" #Unifi password
baseurl="https://unifi_server_name:8443" #Unifi URL
site="default"                  #Unifi site the gateway resides in

#### END VARIABLES ####

#Copy updated config to controller
scp $config_file $ssh_user@$unifi_server:$unifi_gateway_path

#API interface functions
cookie=$(mktemp)
curl_cmd="curl --tlsv1 --silent --cookie ${cookie} --cookie-jar ${cookie} --insecure "
unifi_login() {
    # authenticate against unifi controller
    ${curl_cmd} --data "{\"username\":\"$username\", \"password\":\"$password\"}" $baseurl/api/login
}

unifi_logout() {
    # logout
    ${curl_cmd} $baseurl/logout
}

unifi_api() {
    if [ $# -lt 1 ] ; then
        echo "Usage: $0 <uri> [json]"
        echo "    uri example /stat/sta "
        return
    fi
    uri=$1
    shift
    [ "${uri:0:1}" != "/" ] && uri="/$uri"
    json="$@"
    [ "$json" = "" ] && json="{}"
    ${curl_cmd} --data "$json" $baseurl/api/s/$site$uri
}

#Trigger a provision
unifi_login 
unifi_api /cmd/devmgr {\"mac\": \"$gateway_mac\", \"cmd\": \"force-provision\"}
unifi_logout

No more manually clicking provision after manually editing the config file on the controller!

CLI

rsync to remote directory containing spaces

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I ran into an issue where if I ran rsync to a remote server with a path that contained spaces it would simply terminate at the first space instead of copying the whole path. I learned you need to do some quote tricks to get this to work properly (thanks to this site for helping me.)

The trick is to enclose the entire remote path, server included, in SINGLE quotes. In addition to the single quotes you still need to escape every space with a backslash ( \ )

rsync -aP <source_folder> 'REMOTE_SERVER:/full\ path\ with\ escaped\ spaces/folder/'

CLI, Hardware, OS

Manually set monitor refresh rate with xrandr

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My recent distro hopping has found some distros don’t let you change your monitor’s refresh rate via the GUI. After a while I found this post which explains the syntax for xrandr to force the refresh rate of 100hz (adjust to your liking)

xrandr --output DP-0 --mode 3440x1440 --rate 100

Create an auto start item with this line of code in it to get this to happen automatically on startup.

CLI, OS

KeePassRPC incompatible with the current KeePass version

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I keep forgetting about this snag so I’ll document it. In Debian / Ubuntu distros, once you’ve added the PPA to have the latest version of KeePass installed, if you try to install the KeePassRPC plugin (Kee) it will tell you the version is incompatible, even though it is.

The following plugin is incompatible with the current KeePass version: /usr/lib/keepass2/Plugins/KeePassRPC.plgx

Have a look at the plugin's website for an appropriate version.

The fix, as found here, is to install the mono-complete package

sudo apt install mono-complete

Restart KeePass after installation. That’s it!

CLI, Web

Headless Private Internet Access with OpenVPN & Port Forwarding

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I wanted to initiate a connection to my VPN provider Private Internet Access (PIA) from one of my headless CentOS 7 servers. Unfortunately PIA software requires a GUI to work. Fortunately, PIA provides ovpn files that fully work with the openVPN software, which does work headlessly.

I followed this guide from htpcguides.com to get me going. I tweaked it a bit to work with CentOS 7. I then used this guide to help me set up port forwarding to work with transmission-daemon.

First, install openvpn & iproute

sudo yum -y install openvpn

Next grab PIA’s ovpn files for their servers:

wget https://www.privateinternetaccess.com/openvpn/openvpn.zip
sudo unzip openvpn.zip -d /etc/openvpn/pia

Now create a credentials file to specify your PIA username and password. The format is simply the first line being your PIA username, and the second line being your PIA password, nothing else.

#Create file
sudo vim /etc/openvpn/pia/.secret

#Enter PIA credentials into the file, then save and exit
USERNAME
PASSWORD

#Change permissions to be readable only by root
sudo chmod 700 /etc/openvpn/pia/.secret

Test if it’s working by manually running OpenVPN

sudo openvpn --config /etc/openvpn/PIA_SITE_FILENAME.ovpn --auth-user-pass /etc/openvpn/pia/.secret

Create a systemd service file to get OpenVPN to run on startup

sudo vim /usr/lib/systemd/system/pia.service

[Unit]
Description=OpenVPN
After=syslog.target network.target

[Service]
PrivateTmp=true
Type=forking
ExecStart=/usr/sbin/openvpn --daemon --config "/etc/openvpn/PIA_SITE_FILENAME.ovpn" --auth-user-pass /etc/openvpn/.secret

[Install]
WantedBy=multi-user.target

Reload systemd daemons and enable at boot:

sudo systemctl daemon-reload
sudo systemctl enable pia.service

Start the service (or reboot) and then use curl to verify your external IP has changed

sudo systemctl start pia.service
curl https://ipinfo.io/ip

Port Forwarding

PIA is awesome because it supports port forwarding to facilitate things like torrents. I took the script from this guide and tweaked it a bit to suit my needs (and to correct a syntax error)

Note: PIA only supports port forwarding from specific regions. Here is the current list.

Download script to pia directory

sudo wget -O /etc/openvpn/pia/portforward.sh https://raw.githubusercontent.com/HTPCGuides/pia-port-forwarding-scripts/master/transmission-pia-port-forwarding.sh
sudo chmod +x /etc/openvpn/portforward.sh

Edit the script to provide PIA username and pass, and Transmission user/pass (if you have that configured.) The variables to change are USERNAME,PASSWORD, TRANSUSER, and TRANSPASS

Test the script by running it manually (make sure both your pia service and transmission services are already running.) I’ve noticed that the script will say success even on failure which is why I suggest using bash -x so you can see actual error messages from PIA regarding port forwarding:

sudo bash -x /etc/openvpn/pia/portforward.sh

After that’s run you can check your transmission daemon to ensure it is listening on the PIA port that’s been forwarded.

Configure to run on startup and every two hours by invoking cron:

sudo crontab -e

@reboot sleep 60 && /etc/openvpn/pia/portforward.sh | while IFS= read -r line; do echo "$(date) $line"; done >> /var/log/pia_portforward.log 2>&1 #PIA Port Forward
0 */2 * * * /etc/openvpn/pia/portforward.sh | while IFS= read -r line; do echo "$(date) $line"; done >> /var/log/pia_portforward.log 2>&1 #PIA Port Forward

If you are paranoid about transmission running without the VPN working you can tweak your transmission service to rely on the pia service before starting. Modify /usr/lib/systemd/system/transmission-daemon.service and tweak the After line and add a Required line so it now reads this:

Required=pia.service
After=network.target pia.service

Don’t forget to run a sudo systemctl daemon-reload afterward.

Troubleshooting

If you get the error message “/etc/openvpn/pia/portforward.sh: line 35: [: : integer expression expected” it means you have to tweak the script a bit (it’s broken?)

Change line 35 to be the following:

if [ "$SPLITVPN" == 1 ]; then

CLI

Merge multiple MP4 files into one with ffmpeg concat

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I had a bunch of MP4 files I wanted to merge into a single file. FFMpeg came to the rescue, but it had a bit of a quirk I needed to figure out. Thanks to this site for the help.

First, create a list of files you wish to merge. In this example I want every file with a specific file pattern beginning with 2019-05-02. I take that output and run sed against it to add “file ‘” to the begging and a closing ” ‘ ” at the end. The end result is a nice list of files for ffmpeg to ingest.

ls 2019-05-02* | sed "s/^/file '/g; s/$/'/g" > filelist.txt

With our shiny new list we can now tell ffmpeg to use it to concatenate to a single file:

ffmpeg -f concat -safe 0 -i filelist.txt -c copy OUTPUT_FILENAME.mp4