Transcribe Audio or Video through an offline standalone application (HTML5 based)

I use a Sony TX650 device for recording audio notes. It allows me to increase/decrease the playback speed and helps me in faster transcription. However, it is not always efficient because when doing a transcription on a machine, I need to juggle between the player’s controls as well as the keyboard.

Transcribe Audio or Video Offline

To alleviate that, I created an offline transcription software. It is a single page HTML file and using Javascript and HTML5 Local Storage you can do transcription of both your audio and video files – and export the content.

A demo is available at

and the source code is available on GitHub at


How To Securely Open Ports (SSH, RDP etc.) On-Demand For Dynamic IPs Through iptables

An encrypted SSH connection allows complete access to your machine. However, unless you diligently manage all security updates to your OS and SSH Server, there is a possibility that your SSH server gets compromised.

Typically, system administrators restrict access to the SSH Server (Port 22) to selected IPs. The limitation in opening the Port 22 to selected Static IPs is that you will not be able to connect to it when you are on the move, and need to access your machine from, say a mobile phone.

To overcome this limitation, I have written a script that uses a combination of a web server and iptables firewall, and grants access to Port 22 (or any other Port) on demand to an IP you prefer. It can also work equally well on an AWS EC2 machine where you open Port 22 for all IPs ( using a Security Group, and then restrict access via iptables to that EC2 instance.

I will be using

  • Ubuntu
  • Apache with PHP
  • iptables Firewall
  • sudo Access

Step 1 – Grant Access to iptables to www-data user

On Ubuntu, Apache runs with www-data as a user. We will allow www-data user to execute iptables via sudo without a password

Edit the sudoers file

sudo visudo

At the end of the file, add the following

www-data ALL=NOPASSWD: /sbin/iptables

The line above allows www-data access to the command iptables, without a password.

Verify if sudo is indeed working for www-data user.

Run the following command to verify.

sudo -H -u www-data bash -c 'sudo iptables -L'

Note: It should not ask any password for www-data and show the data related to iptables as shown in the screenshot above.

Step 2 – Allow Authenticated Access to Ports via The Web

We will now create a file that we’ll put on a web server for easy access. Save the following in a file, and place it on a safe, https protected location on your web server.

  1. Get the code at GitHub –
  2. Change the password and the port that you wish to open in openport.php

Now access the openport.php script from your browser.

Complete GitHub Repository at

For example: (Replace the URL with your domain & script name)


  1. The ports that you open via the script tend to remain open like forever. You should ideally setup a firewall script via iptables and reset the rules at a pre-defined interval.
  2. Instead of using a fixed password, you can try out an OTP version (tutorial coming soon).
  3. For RDP and other ports that are not on the same machine, but are within the same network, you can setup Port Forwarding based on iptables and do the relevant NAT based redirection.

Use Amazon’s AWS VPC, & Your VPN To Extend Your Server Infrastructure (using Static Routing)

With the invent of cloud computing, a much powerful addition to a corporate data centre was the ability to scale its infrastructure in a virtual private cloud. The setup thus becomes flexible enough to manage the resource demand and remains safe from the public eye.

Using AWS VPC with Corporate VPN is an excellent option to extend a corporate data centre.

  • AWS offers multiple regions and extreme flexibility to tweak your infrastructure needs
  • The data rides on a VPN Tunnel and is not publicly exposed, thus meeting information security & confidentiality needs of an organisation

In the following post, I will delve deeper into creating a prototype of how you can extend your business network and put it on the “cloud”.

What we will be doing:

  1. Setup VPC & VPN on AWS
  2. Configure an External Machine to act as Corporate IPsec VPN (using “racoon”)
  3. Connect our External Machine to AWS and test

Note: We will use “Static” routing, which is simpler, and not “Dynamic (BGP)” routing, which requires many more steps.

AWSVPN-VPN Architecture

Interconnecting AWS VPC & VPN with Corporate VPN through IPSec (racoon)

Our Base Setup

  1. An External Machine to act as a Corporate VPN Appliance (referred as “CorpVPN”), running Ubuntu/Debian Linux variant with a public IP. I took a cloud server with Rackspace Cloud, but you can take it up on AWS in a different region too if you prefer.
  2. Opening of UDP 500 & UDP 4500 on the CorpVPN Firewall (or AWS Security Group Inbound Rule if you’re using AWS EC2 machine as CorpVPN Appliance).
  3. Since CorpVPN is an independent device, we don’t have a connecting internal network to it. So we will use the Link-local 169.254.x.x IP Addresses.
  4. An AWS Account where we can create an EC2 machine and configure VPN Services


Part 1 – AWS Setup

1a) VPC Configuration

Create a New VPC

Select “VPC” option under Services

Go to “Your VPCs”, and “Create New” VPC

AWSVPN-Setup of VPC 02

We will use the network as for the EC2 Machines which will work as our extended network.

Create a Subnet for your EC2 Machines. We will select it when we configure our EC2 Machine. In this example, we use as the subnet.

AWSVPN-Setup Subnet

Add an Internet Gateway

Create an Internet Gateway and attach it with the new VPC that you created so that your EC2 machines can reach Internet & you can connect to them remotely. You can let go of this option if you don’t want any external connectivity.

AWSVPN-Setup Internet Gateway 01AWSVPN-Setup Internet Gateway 02AWSVPN-Setup Routing

Setup a Security Group

Create a Security Group that allows ping and SSH to your EC2 machines. As per your preference, open ICMP and SSH for everyone or only to limited IP addresses.

AWSVPN-Create Security Group 01AWSVPN-Setup Security Group 02

1b) VPN Configuration

Customer Gateway (CGW)

The Customer Gateway is primarily our CorpVPN gateway. We need to provide the IP Address of our CorpVPN server. If you have it readily available, then provide it, else add a random IP and change later once your CorpVPN server is setup.

AWSVPN-Setup Customer Gateway

We will use as an example as the IP of the CorpVPN Server. Please note that “Static” routing is selected.

Virtual Private Gateway (VGW)

We create a Virtual Private Gateway that enables network connectivity to our VPC. It is a two step process

  • We create the VGW
  • We attach it to our VPC that we created

AWSVPN-Setup Virtual Private Gateway 01AWSVPN-Setup Virtual Private Gateway 02

VPN Connection

It is a hardware VPN and is a paid service. Create a new VPN and select the following

  • VGW that you created before
  • CGW that you created before
AWSVPN-Setup VPN Connection 01

Routing Option should be “Static”

AWSVPN-Setup VPN Connection 02


Static IP Prefixes will be Link-local addresses It means you will reach the AWS network through your Private IP Address in 169.254.x.x series.

Note: We are using the above configuration because we have an independent CorpVPN machine. If you do have a VPN appliance and a network behind it, please go ahead and use your internal IP range.

It takes a few minutes to get the VPN ready.

Once the VPN is available, you can download the “Generic” configuration. It is a text file with the VPN IP Addresses and other configuration details.

AWSVPN-Sample Tunnel Config

Example Tunnel #1 Configuration’s Text File

Enable Route Propagation

Open the “Route Table”, select the “Route Propagation” tab. For the CorpVPN VGW, enable “Propagate”.

AWSVPN-Route Propagation

It is a critical step. Without “Route Propagation”, you will not be able to reach the EC2 machines from the VPN.

1c) EC2 Machine Setup

In the same region where you have setup your VPN, create an EC2 machine. I used t2.nano with Ubuntu 16.04. This EC2 machine will act as our extended network hosted on AWS.

Please ensure that you select the VPC that we created when configuring the EC2 instance.

AWSVPN-EC2 Machine Setup 01

Also, ensure that you select the Security Group that we created for the Corporate VPC.

AWSVPN-EC2 Machine Setup 02

Part 2 – CorpVPN Setup (the CGW Setup)

Points to note:

  • AWS VPN Setup by default provides 2 VPN Tunnels (for Failover). However, since we are just testing it out, we will only be using 1 Tunnel. It will help ease the setup.
  • The CorpVPN setup is our Customer Gateway, and we had provided its IP address while configuring the VPN in AWS.
  • Remember – we are using a separate server (hosted on Rackspace Cloud) to act as CorpVPN Appliance. You can use an AWS Setup also by setting up an Ubuntu based server in a different region. Don’t forget to open UDP 500 & UDP 4500 in the Security Group / Firewall.

2a) Base Installation for IPsec & Racoon VPN Server

Install ipsec-tools & racoon. On a Debian/Ubuntu machine, you can use

apt-get install ipsec-tools racoon

Racoon is the IPsec server that we will use to establish the VPN. We will also use ipsec-tools to setup the SPD (Security Policy Database) to allow connection to-and-from AWS.

2b) IPsec Tools Configuration

Modify the file /etc/ipsec-tools.conf and use the entries below. You will need to refer to the “Generic Configuration” that you downloaded in the steps above from AWS interface.

To be specific, the IP Addresses as mentioned in our downloaded configuration are:

  • CGW Inside IP – (At Customer/CorpVPN’s end)
  • VGW Inside IP – (At AWS End)


  • CGW Outside IP – (CorpVPN’s publicly exposed IP)
  • VGW Outside IP – (For Tunnel #1, it is AWS VPN IP)



#!/usr/sbin/setkey -f

## Flush the SAD and SPD

# Tunnel 1
# -4 means use only IPv4. Can be omitted.
# a) Allow CGW Inside IP Address to VGW Inside IP Address "outbound" from CGW Outside IP Address to VGW Outside IP Address
spdadd -4 any -P out ipsec esp/tunnel/;
# b) Allow VGW Inside IP Address to CGW Inside IP Address "inbound" from VGW Outside IP Address to CGW Outside IP Address
spdadd -4 any -P in ipsec esp/tunnel/;

# c) Allow CGW Inside IP Address to VPC Network "outbound" from CGW Outside IP Address to VGW Outside IP Address
spdadd -4 any -P out ipsec esp/tunnel/;
# d) Allow VPC Network to CGW Inside IP Address "inbound" from VGW Outside IP Address to CGW Outside IP Address
spdadd -4 any -P in ipsec esp/tunnel/;

Now on the CorpVPN setup, we will add the CGW Inside IP

ip a a dev eth0

Replace eth0 with the relevant network card, preferably the one on which you have configured the CorpVPN/CGW IP.
Later, if you need to delete it, you can use ip a d dev eth0

Do a

route -n

To confirm if the IP is now available in the routing table.

Reset the ipsec-tools rules

/etc/init.d/setkey restart

2c) Racoon Configuration

We will now setup the IPsec Server – Racoon. The configuration is simple, and you can copy paste the following and replace the IPs with your relevant IP Address Ranges.

Modify the file /etc/racoon/racoon.conf

path pre_shared_key "/etc/racoon/psk.txt";

# Tunnel 1
# VGW Outside IP Address
     exchange_mode main;
     # CGW Outside IP Address
     my_identifier address; 
     # VGW Outside IP Address
     peers_identifier address;
     ike_frag on;
     generate_policy = off;
     initial_contact = on;
     nat_traversal = on;

     dpd_delay = 10;
     dpd_maxfail = 3;
     support_proxy on;
     proposal_check claim;

          authentication_method pre_shared_key;
          encryption_algorithm aes 128;
          hash_algorithm sha1;
          dh_group 2;
          lifetime time 28800 secs;

# CGW Inside IP Address & VGW Inside IP Address
sainfo address any address any
     encryption_algorithm aes 128;
     authentication_algorithm hmac_sha1;
     pfs_group 2;
     lifetime time 3600 secs;
     compression_algorithm deflate;


In /etc/racoon/psk.txt, enter the VGW Outside IP Address, and the Pre-Shared Key that is available in the configuration.    pjt61xwU3jRoNiUBXVli73aQs31awm4Gg


Restart Racoon.

  • To begin with, you can do a debug mode ON racoon initialisation. For example:
racoon -Fvdd
  • Later on, you can just manage it through init script.
/etc/init.d/racoon restart

Part 3 – Testing the setup

Now you need to ping your VGW Inside IP Address from your CorpVPN/CGW machine


It should start pinging within a few seconds.

You should be able to see the status of the VPN Tunnel as up for your VGW Outside IP Address under VPN Connections on Amazon. It is important for this to happen.


If the above doesn’t work, please refer to the Troubleshooting section.

Now you need to add a route so that you can reach your range of IP Addresses.

route add -net gw dev eth0

Do a

route -n

To check if your configuration is correct, and you have set the appropriate gateway.

Now ping your EC2 instance’s Private IP address.


It should work.

Similarly, from your AWS EC2 instance, you can ping the CGW Inside IP Address


If it works, then CONGRATULATIONS to you. You have successfully established the two way connection.

Part 4 – Maintenance & Troubleshooting

To make it permanent, you need to add the ip address addition (of CGW Inside IP Address), and routing rules (Using VGW Inside IP Address as Gateway for range) in maybe /etc/rc.local or in your /etc/network/interfaces so that they apply automatically on a reboot.

Also, to keep the tunnel alive, traffic has to pass through it. You can setup a cron job with the following to ensure that the tunnel is always up

* * * * * (/bin/ping -c 10 > /dev/null 2>&1

You have to be able to ping the inside IP Address of VGW. If that is not happening, please make sure you have done ‘Route Propagation’ for that VGW under ‘Routing Tables’ -> ‘Route Propagation’ under AWS VPC Settings.

You should be able to ping your EC2 instance. If not, then

  • Make sure you’ve allowed ICMP (ping packets) to pass through in the Firewall (Security Group for your EC2 Instance).
  • You have added the route on your CGW, for reaching your EC2 Subnet (172.16.x.x series for example) through your VGW Inside IP Address (as mentioned in the tutorial above).
  • Have you replaced the IP addresses with the ones provided in the Downloaded Configuration File as well as the ones of your Customer Gateway?

If the tunnel works but goes down intermittently, then to keep it active you need to ping the VGW Inside IP Address continuously. Use a cron job for that as explained in the tutorial above.

That’s all. There are instructions on AWS to setup through dedicated VPN Appliances. You can refer those to Extend Your Network and make it more scalable.

Fitbit Intraday Heart Rate Tracking (with Code)

I recently upgraded to Fitbit Alta HR. It is much better than Fitbit Flex that I had been using for past many years. And the best part is the heart rate tracking, which also helps in getting better Sleep Quality outputs.

Fitbit Alta HR captures Heart Rate periodically (at few second intervals)

What was missing?

However, one thing that I missed with Alta HR and the Fitbit App was the display of the Heart Rate data. For instance, below is my Heart Rate during an Emotionally Charged Up Environment at Workplace. Note, I was sitting with No Physical Activity!

Heartbeat - Emotionally Charged

Heart Rate Variation while sitting – but with Emotions Running High!

If you notice, the Fitbit App shows Heart Rate data in 5-minute intervals. And the self-quantification person that I am, that was not enough. I wanted the entire data that Alta HR recorded. Thus, I began working on getting that reliably.


The End Result, & How You Can Use It

I have created a web version where you can review your Heart Rate data quickly.

Get your Heart Rate Chart at

Remember to see the Tutorial on how to retrieve your “Client ID” from the Fitbit website.

Note: The application I have created saves the heart rate data in a database. It means that I will have your heart rate data. However, I am not asking for or collecting any user information. So despite the fact that I have the heart rate data, I cannot link it with an individual.

I have open sourced the entire code, and it is available on GitHub.

How it works

  • Fitbit allows developers to connect to its API after authentication through the OAuth2 Protocol.
  • Since the heart rate data is personal to a user, Fitbit does not permit third party developers to access heart rate data of another user.
  • You will need to authenticate yourself on the Fitbit Developer Portal and create an “App” on it. It is a relatively simple process, and if you are connecting to my service at, then you can view the tutorial on YouTube.

Now Go – Track your HB!

Asterisk VOIP and pfSense IPSec VPN Clients

I had setup a pfSense 2.1 based IPSec VPN following the instructions at which worked well for my mobile devices and machines.

However, using a SIP based softphone over VPN connecting to my workplace’s Asterisk based VOIP setup never really worked properly. I dabbled in changing the subnet masks, changing asterisk settings, phone settings, NAT and many other things – all of which didn’t really work. The maximum I was able to achieve was calling up *43 which is the echo number and hear my own voice.

The reason for it to not work was that my VPN setup was having a different IP Address range (e.g. 192.168.10.x/24), and my LAN network was different (say 192.168.5.x/24). This is how the VPN is setup, but this allows one way communication – my VPN clients can reach the LAN, but LAN cannot reach the VPN clients. So, Asterisk server, while signaling worked, the media didn’t. So the ring was there, but no voice, since it was trying to send it back to 192.168.10.x series and my pfSense box wasn’t passing it through.

The simple solution was adding a firewall rule in LAN settings, and allowing the LAN subnet to pass traffic to the 192.168.10.x/24 network (Protocol: any, Ports: any). By default it is blocked. And THEN I could ping my VPN clients from LAN too which was the ideal setup, even for remote troubleshooting.

Tracking your Route through GPS – Getting Started

It was 14th February 2013, Valentine’s Day. Inspired by one Motorola commercial, I set out to walk in a ‘heart shaped’ route, as a Valentine Gift for my beloved wife. The commercial is available at and the end result was tracked on Sports Tracker, with me walking in a heart shaped route near Lotus Temple, Delhi, India.


I don’t have a good navigation sense, and rely mostly on GPS/Google Maps/Map My India for my everyday needs. Thus, to accomplish this task I’d specially bought a professional compass to track the directions, and had planned to cover at least 2 kilometers walking/running (though eventually it was restricted to 100 meters, reasons I’ll not delve into).

But, the biggest gain (apart from the delighted beloved, and learning how to use a compass) was that I came across various techniques that are used across the globe to track/plan a route. It’s more awesome than I ever imagined!

Continue reading

Wireless on Ubuntu 11.10 and Lenovo Thinkpad E420

Unlike 11.04 and earlier, Ubuntu 11.10 runs much better on Lenovo Thinkpad E420. The only glitch is the wifi drivers which don’t run by default, and it could be corrected easily

Using LiveCD or a running system

  • Press Super (Window) key, and open Terminal
  • Type sudo modprobe -r acer_wmi

That’s all. You should be able to connect to the wireless till next reboot.

Making the change permanent

Edit the file /etc/modprobe.d/blacklist.conf and in the end type

blacklist acer_wmi

Reboot and you’re done. If you’re doing it entirely from the GUI, then editing the file could be done by pressing ALT+F2 (this would open a “Run” window) and typing there gksu gedit /etc/modprobe.d/blacklist.conf

Please note: This applies to wireless card having rtl8188ce chipset. You can view that by typing lspci in a terminal and searching for the entries respective to Network Controller.