Cyber Security – Penetration Testing Checklist

Hello folks,

Below is the list of Penetration Testing checklist notes that were discussed in the OWASP meeting I attended yesterday.

1). Web Applications – Check if a web application is able to identify spam attacks on contact forms used in the website.

2). Proxy Servers – Check if the network traffic is monitored by proxy appliances. Proxy servers make it difficult for hackers to get internal details of the network.

3). Spam Email Filters – Verify if incoming and outgoing email traffic is filtered and unsolicited emails are blocked.

4). Firewalls – Make sure an entire network or computers are protected with a firewall.

5). Exploits – Try to exploit all servers, desktop systems, printers and network devices (Within scope).

6). Verification – Verify that all usernames and passwords are encrypted and transferred over secured connections like HTTPs.

7). Cookies – Verify information stored in website cookies. It should not be in readable format.

8). Vulnerabilities – Review previously found vulnerabilities to check if the fix is working.

9). Open Ports – Ensure there are no unnecessary open ports on a network.

10). Telephones – Check all telephone(VOIP) devices.

11). WiFi – Test Wifi network security.

12). HTTP Methods – Review HTPP methods. PUT and DELETE methods should not be enabled on web server.

13). Passwords – Password should be at least 8 character long containing at least one number and one special character.

14). Usernames – Usernames should not be like “admin” or “administrator”

15). Application Login Pages – Application logins pages should be locked upon few unsuccessful login attempts (Brute force attacks).

16). Error messages – Error messages should be generic and not mention specific error details like “Invalid username” or “Invalid Password”.

17). Special Characters – Verify if special characters, HTML tags and scripts are handled properly as an input value.

18). Internal System Details – Internal system details should not be revealed in any of the error or alert messages.

19). Custom Error Messages – Custom error messages should be displayed to the end users in case of web page crash.

20). Registry Entries – Review the use of registry entries. Sensitive Information should not be kept in registry.

21). Scanning Files – All files must be scanned before uploading to server.

22). Sensitive Data – Sensitive data should not be passed in URL’s while communicating with different internal modules of the web application.

23). No Hard-Coded usernames or passwords – There should not be any hard coded username of password in the system.

24). Input Fields – Check all input fields with long input strings – With and Without spaces.

25). Password Functionality – Ensure reset password functionality’s secure.

26). SQL Injection – Check application for Cross Site Scripting.

27). XSS – Check application for Cross Site Scripting.

28). Input Validations – Important input validations should be done at server side instead of Javascript checks at client side.

29). System Resources – Critical resources in the system should be available to authorized persons and services only.

30). Access Permissions – All access logs should be maintained with proper access permissions.

31). Ending Sessions – Check that user sessions end upon log off.

32). Directory Browsing – Verify that directory browsing is disabled on the server.

33). Up To Date Versions – Verify that all applications and database versions are up to date.

34). URL Manipulation – Review URL manipulation to make sure a web application is not showing any unwanted information.

35). Buffer Overflow – Check memory leak and buffer overflow.

36). Brute Force Attacks – Check if systems are safe from Bruce Force Attacks – use a trial and error method to find sensitive information like passwords.

37). DoS (Denial of Service) – Ensure the system or network is secured from DoS (Denial-of-service) attacks.

 

All credits to Rob Taylor

Hope you’ve liked it.

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JSHint Errors

When using a simple ternary operator with JSHint, may cause the build error shown below,

someExpressionThatIsEitherTrueOrFalse ? someFunctionThatIsCalledIfExpressionIsTrue(x, y) :
setOtherVariableIfExpressionIsFalse = true;
^ Expected an assignment or function call and instead saw an expression.

Solution

Add below JSHint Comments where expression has been written

/* jshint expr: true */

Ex:

/* jshint expr: true */
nameController.isMiddleNameNullOrEmpty ? submit() : validate();

Note: The important thing to remember is to have this JSHint comments (/* jshint expr: true */ ) be used only within the function where the expression is being used, else it would turn off the JShint globally.

All about NPM (Node Package Manager)

All about NPM (Node Package Manager) https://www.npmjs.com/

  • Its about Sharing the Code or Packages or Modules on the node package manager repository.
  • By default node package manager repository is publicly accessible, however there are options to make it private at a price.
  • We can search for packages that have been registered in the registry. Go to https://www.npmjs.com/ and find the Packages or Using the Query URL https://www.npmjs.com/search?q=bower
  • The packages are managed and powered by the CouchDB database.
  • You can also run the published packages on the node package manager over the browser using Runkit @https://runkit.com/npm/npm-demo-pkg29 where “npm-demo-pkg29” is the package I created. This package has a reported method “printMsg()”, which prints “Hello”. You can also share the code https://runkit.com/5801f19682bd9d0014eec77c/580289b7ce0bd500138eec0c

Here are some of the differences between Packages and Modules within NPM

Packages:

  • A “package” is a file or directory that is described by a package.json file. In other words, a package.json file defines a package. For example, if you create a file at node_modules/foo.js and then had a program that did var f = require(‘foo.js’), it would load the module. However,foo.js is not a “package” in this case, because it does not have a package.json.
  • A package is any of:
    • a) a folder containing a program described by a package.json file
    • b) a gzipped tarball containing (a)
    • c) a url that resolves to (b)
    • d) a <name>@<version> that is published on the registry with (c)
    • e) a <name>@<tag> that points to (d)
    • f) a <name> that has a latest tag satisfying (e)
    • g) a git url that, when cloned, results in (a).
  • Even if the package is never published to the npm repository, you can circulate the packages locally and achieve benefits of using npm:
    • if you just want to write a node program, and/or
    • if you also want to be able to easily install it elsewhere after packing it up into a tarball

Modules:

  • A module is any file or directory that can be loaded by Node.js’ require(). For example, if you create a package which does not have an index.js or a “main”field in the package.json file, then it is not a module. Even if it’s installed in node_modules, it can’t be an argument to require().
  • ‘CLI’ packages for example is not modules since they only contain executable command line interface and don’t provide a main field for use in Node.js programs.
  • A module is any of:
    • A folder with a package.json file containing a main field.
    • A folder with an index.js file in it.
    • A JavaScript file.
  • In the context of a Node program, the module is also the thing that was loaded from a file. For example, in the following program:
    var req = require(‘request’)
    we might say that “The variable req refers to the request module”.
  • Most npm packages are modules because, npm packages that are used in Node.js program are loaded with require, making them modules. However, there’s no requirement that an npm package be a module

Here are the list of NPM commands that I use (some of which are the ones that I occasionally use).

npm -v
Gives the version of installed npm

npm install npm@latest -g
Installs the latest version of npm

npm install {packageName}
{packageName} can be any packages that are available on the npm repository. If the Packages are not available then npm CLI will throw error.
npm install {packageName} -g
options: -g
global install. Usually this gets installed in (/usr/local). If this option is not specified, node_modules gets installed in the same directory where you are on the terminal. Check pwd for the current directory.

For uninstalling use npm uninstall {packageName}

Note: Just in case if you do not have permissions to the folder (/usr/local), run the commands using sudo prefix

npm config get prefix
Gives the current directory where npm modules gets installed globally.
Check this https://docs.npmjs.com/getting-started/fixing-npm-permissions if you intend to change permissions.

npm init
This is used to create a package.json with a questionnaire being prompted on CLI.

npm init –yes
option –yes // Creates a default package.json file with default inputs, without asking any questions.

npm install {packageName}  –save This adds entry to package.json’s dependencies attribute.

For removing the dependency use npm uninstall {packageName} – – save

npm install {packageName}  –save-dev
This adds entry to package.json’s devDependencies attribute

For removing the dependency use npm uninstall {packageName} –save-dev

npm update
Updates the dependencies of the the packages defined in the package.json file. Note: The folder should contain package.json file

For updating all packages globally (/usr/local), use option -g; npm update -g

npm outdated
Check if the packages are outdated.

For checking all outdated packages globally (/usr/local), use option -g;

npm outdated -g

npm outdated -g –depth=0 // Same as above, but finds at a given depth

npm config list
Spits out the npm’s configuration file’s list

npm config ls -l
Lists out all the default values of npm’s configuration file.

npm ls  OR npm list
Lists the dependencies and see the relationships of other dependent dependencies with version numbers

npm ls –depth=0
Lists only the primary dependencies. The other alternative is using the ‘tree’ command tree -d /usr/local/lib/node_modules

npm root
Gives the directory path where node moduels are installed. npm root -g gives the directory path where node modules are installed globally.

npm view {packageName} version
Ex: npm view angular version
Gives the package version that is installed locally. -g at the end of the command gives the package version installed globally.

Breakdown of NPM resources from NPM Documentation:

Using package.json with versioning’s and versioning details:

https://docs.npmjs.com/misc/semver

https://docs.npmjs.com/getting-started/using-a-package.json

https://docs.npmjs.com/getting-started/semantic-versioning

https://docs.npmjs.com/getting-started/using-tags

https://docs.npmjs.com/files/package.json

Creating and Publishing packages to npm registry:

https://docs.npmjs.com/getting-started/creating-node-modules

https://docs.npmjs.com/getting-started/publishing-npm-packages

NPM’s Dependency resolution, Duplication and DeDuplication

https://docs.npmjs.com/how-npm-works/npm2

https://docs.npmjs.com/how-npm-works/npm3

https://docs.npmjs.com/how-npm-works/npm3-dupe

https://docs.npmjs.com/how-npm-works/npm3-nondet

Javascript: A word with Spaces

Given a word “HELLO”, print the word with spaces “H E L L O”.

Naive Solution:

function spacing(a){
   var b = a.split(''), c = b[0];
   for(var i=1; i < b.length; i++){
       c += " " + b[i];
   }
   console.log(c);
}

spacing('hello');

The output is:

h e l l o

Using Javascript prototypes:

function SetString(stringName){
   this.stringName = stringName;
}

function SpacingFunction(){
   var b = this.stringName.split(''), c = b[0];
   for(var i=1; i < b.length; i++){
      c += " " + b[i];
    }
   console.log(c);
}

SetString.prototype.spacingFunction = SpacingFunction;

new SetString('hello').spacingFunction();

The output is:

h e l l o


Resources:

http://javascriptissexy.com/javascript-prototype-in-plain-detailed-language/

Javascript: Type Error vs Reference Error

In order to understand Type Error vs Reference Error, first we will need to know Variable Declaration vs Variable Initialization.

var x;

In this above statement, we can say that x is declared but not yet initialized.

var x = 5;

Here, we can say that x is declared and as well initialized.

Now, let’s say we would want to access the x’s property that has been declared but not initialized.

var x;
console.log(x);

This would result variable x to be

undefined

Now, let’s say that we would want to declare and initialize x to undefined and then access the x’s toString() method.

var x = undefined;
console.log(x.toString());

This would result in

Uncaught TypeError: Cannot read property ‘toString’ of undefined(…)

Now, let’s say we would like to access the x’s property thats been been declared as well as initialized.

var x = 5;
console.log(x.toString());

This would result

5   // Since 5 is declared and initialized as a number, 
    //and we were trying to convert it to a String.

Now, let’s say we would want to access a variable y that doesn’t exist in the scope (meaning that there is not presence of variable y with out any initialization or declaration)

console.log(y);

This would result in

Uncaught ReferenceError: y is not defined(…)

 

Happy Learning 🙂

Order of execution in Javascript

Given the below functions

function ME(){console.log("ME")};

function MYSELF(){window.setTimeout(function(){console.log("MYSELF")}, 0);}

function I(){
   return new Promise(function(resolve, reject){
      window.setTimeout(function(){resolve("hi");},5000);
   }
).then(function(response){
          console.log("I");
     }, function(error){
          console.log("error");
      }
)}

If I supposedly call these functions sequentially as shown below:

MYSELF();
I();
ME();

Here is the order the javascript engine (Google’s V8 if chrome) takes precedence of executing it.

The output would be:

ME    // The ME() function outputs its result in the first place because it gets executed immediately even though it is being called in 3rd line, and the main reason being, it has no timeouts and nothing gets listed to the browser’s window Object

MYSELF   // The MYSELF() function outputs its result the second place even though it is being called in the 1st place AND it has a timeout function which is set to 0 seconds, because the timeout function is bound to the window object of the browser and it takes an extra roundtrip for the browser to get the event listened on its window object.

I   // The I() function outputs its result in the third place even though it is being called in the 2nd place, because it uses the asynchronicity feature using the Javascripts Native Promise function and also the resolve function of Promise gets called after a timeout of 5 seconds.

Resources:

https://developers.google.com/web/fundamentals/getting-started/primers/promises

Find the middle element of the linked list in single pass – O(n) complexity

A linked list contains Nodes that are linked to each other.

Create a Node – A node consists of data of that node and some information about the next linked node

function Node(data, nextNode){
this.data = data;
this.nextNode = nextNode;
}

Create all nodes

Note: First Node from right. This would be our last node in sequence. The reference to next node would be null since this is our last node.

var n5 = new Node("5", null); 
var n4 = new Node("4", n5);
var n3 = new Node("3", n4);
var n2 = new Node("2", n3);
var n1 = new Node("1", n2);

// So here is the representation of the linked list nodes, that we just created.
// n1 (1, n2) –> n2 (2, n3) –> n3 (3, n4) –> n4 (4, n5) –> n5 (5, null)

Here is how the linked list looks

linkedlist

The Naive Solution to this problem would be in 2 passes (2 for loops), which takes O(n^2) worst case complexity

1st pass is to loop thru to get the count of nodes in linked list and
2nd pass is to loop thru find the middle element by dividing the Count of Nodes by 2

So, for example if there are 5 Nodes.

1st pass is to count the number of nodes = 5
2nd pass is to loop thru to get the middle element by dividing 5/2 = 2.5 (so in the middle element to be 3)

There is a better and a faster way to get this in 1 Pass (1 for/while loop), with O(n) complexity

Assign 2 pointers while looping.
1st pointer moves 1 element at a time.
2nd pointer moves 2 elements at a time (twice as faster as the 1st pointer)

Some theory/story:

Assume that Person A and Person B would like to reach a destination X from same starting point.

Assume that it would actually take 10 mins to reach destination X.

Assume that Person B walks 2 times faster than Person A, then by the time Person B reaches destination X, Person A is exactly half way thru.

So, lets give a starting point to our node n1.

var slowNode = n1;
var fastNode = n1;

// Check if nextNode is not null and nextNode of the nextNode 
// (2 Nodes from the current Node) is also not null
while(fastNode.nextNode != null && fastNode.nextNode.nextNode != null) {
// slowNode should be moving to the next element of the linked list sequentially
slowNode = slowNode.nextNode;
// Now the fastNode should be twice as faster as the slowNode
fastNode = fastNode.nextNode.nextNode;
}

console.log(slowNode.data);

Relevant Code using Java

public class MiddleElementLinkedList {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		// Create Linked List Nodes
		
		LinkedListNode n5 = new LinkedListNode("5", null);
		LinkedListNode n4 = new LinkedListNode("4", n5);
		LinkedListNode n3 = new LinkedListNode("3", n4);
		LinkedListNode n2 = new LinkedListNode("2", n3);
		LinkedListNode n1 = new LinkedListNode("1", n2);
		
		// Set the starting point
		
		LinkedListNode slowNode = n1;
		LinkedListNode fastNode = n1;
		
		while(fastNode.getNextNode() != null && fastNode.getNextNode().getNextNode() != null){
			slowNode = slowNode.getNextNode();
			fastNode = fastNode.getNextNode().getNextNode();
		}
		
		System.out.println("Middle Element: " + slowNode.getData());

	}
	
	public static class LinkedListNode {
		private String data;
		/**
		 * @return the data
		 */
		public String getData() {
			return data;
		}

		/**
		 * @param data the data to set
		 */
		public void setData(String data) {
			this.data = data;
		}

		/**
		 * @return the nextNode
		 */
		public LinkedListNode getNextNode() {
			return nextNode;
		}

		/**
		 * @param nextNode the nextNode to set
		 */
		public void setNextNode(LinkedListNode nextNode) {
			if(nextNode == null)
				this.nextNode = null;
			this.nextNode = nextNode;
		}

		private LinkedListNode nextNode;
		
		LinkedListNode (String data, LinkedListNode nextNode) {
			this.data = data;
			this.nextNode = nextNode;
		}
	}

}

Here is how the linked list looks in Java

linkedlistjava

 

Happy Coding !!!

A few Javascript Gotchas

Regular Equality vs Strict Equality.

{} === {}

false // Even though they are empty objects, strict equality not only checks for type & value, but also checks the created instance. The created instance is different for each new Object

{} == {}
false

{x:5} == {x:5}
false

{x:5} === {x:5}
false

0 === false
false

0 == false
true

0 == 0
true

0 === 0
true

1 == 1
true

1 === 1
true

new Object() == new Object()
false

new Object() === new Object()
false

Object.create([]) === Object.create([])
false

Object.create([]) == Object.create([])
false

var x =””;
if(x){console.log(“123”)} else{console.log(“456”)}
456

var x = [];
if(x){console.log(“123”)} else{console.log(“456”)}
123

“” == 0
true

[] == “”
true

“” === 0
false

[] === “”
false

“” == ”
true

“” === ”
true

typeof(”)
“string”

typeof(“”)
“string”

” instanceof String
false

“” instanceof String
false

new String(“”) instanceof String
true

typeof(new String())
“object”

“”.toString == new String(“”)
false

“”.toString() == new String(“”)
true

“”.toString() == new String(“”).toString()
true

“”.toString === new String(“”)
false

“”.toString() === new String(“”)
false

“”.toString() === new String(“”).toString()
true

[] == new Array[];
VM362:1 Uncaught SyntaxError: Unexpected token ]

[] === new Array[];
VM363:1 Uncaught SyntaxError: Unexpected token ]

typeof(“”)
“string”

typeof(”)
“string”

typeof([])
“object”

typeof(Object)
“function”

typeof(new Array())
“object”

typeOf(new Array()) // typeOf is not defined, O in red is capital
VM418:1 Uncaught ReferenceError: typeOf is not defined(…)(anonymous function)

[].constructor.toString().indexOf(“Array”) > -1
true

[] instanceof Array
true

typeof null
“object”

typeof {}
“object”

{} instanceof Object
VM1270:1 Uncaught SyntaxError: Unexpected token instanceof

var t = {}
t instanceof Object
true

Object instanceof t
VM1385:1 Uncaught TypeError: Right-hand side of ‘instanceof’ is not callable(…)

typeof undefined
“undefined”
Note that typeof undefined is undefined which is wrapped in string quotes, but not a string.

typeof (typeof undefined)
“string”
Since the (inner) typeof undefined is undefined wrapped in string quotes, and the (outer) typeof (“undefined”) is being assumed as a string.

typeof when variable is defined.

var d = {};

typeof d === undefined
false

typeof d === “undefined”
false

d === “undefined”
false

d === undefined
false

typeof when variable is not defined

typeof u === undefined
false

typeof u === “undefined”
true

u === “undefined”
VM455:1 Uncaught ReferenceError: u is not defined
at <anonymous>:1:1
(anonymous) @ VM455:1

u === undefined
VM458:1 Uncaught ReferenceError: u is not defined
at <anonymous>:1:1

Numbers

1/-0 > 0
false

1/-0
-Infinity

-Infinity == 0
false

-Infinity > 0
false

-Infinity === 0
false

-Infinity > 1
false

-Infinity == 1
false

-Infinity === 1
false

Infinity == NaN
false

Infinity === NaN
false

1 instanceof Number
false

1/0 instanceof Number
false

1/0
Infinity

Infinity instanceof Number
false

typeof(“”)
“string”

typeof(Infinity)
“number”

new Number(1) instanceof Number
true

99.99 instanceof Number
false

typeof(99.99)
“number”

new Number(99.99) instanceof Number
true

typeof(NaN)
“number”

NaN instanceof Number
false

new Number(NaN)
Number {[[PrimitiveValue]]: NaN}

new Number(NaN) instanceof Number
true

NaN == Number
false

NaN === Number
false

new Number(NaN) === Number
false

new Number(NaN) == Number
false

NaN == undefined
false

NaN === undefined
false

NaN === ”
false

NaN == ”
false

NaN == null
false

NaN === null
false

isNaN(NaN)
true

Objects/Functions

var e = function(){};
var r = function(){};
var e1 = new e();
var r1 = new r();

e == r
false

e === r
false

typeof e
“function”

e instanceof function
VM352:1 Uncaught SyntaxError: Unexpected end of input

function instanceof e
VM387:1 Uncaught SyntaxError: Unexpected token instanceof

e1 == r1
false

e1 === r1
false

e1 instanceof r1
VM750:1 Uncaught TypeError: Right-hand side of ‘instanceof’ is not callable(…)(anonymous function) @ VM750:1

e1 instanceof Function
false

e1 instanceof Object
true

typeof(e1)
“object”

Assignments

var a = [1,2,3];
var b = [4,5,6];

a = b
[4, 5, 6] // This the value of a

a
[4, 5, 6] // a assignment to b copied over all values of b

b
[4, 5, 6] // No changes to b, so b still had reference to its original values

Pass by reference/value

var func = function(a) { var tempArray = [4,5,6];   a = tempArray;   console.log(a);}

func([1,2,3]);

[4,5,6] // Even though we pass by reference with a different value, the assigned variable value would be overridden with internal assignment (if any).

Which is best to use: typeof or instanceof?

http://stackoverflow.com/questions/899574/which-is-best-to-use-typeof-or-instanceof

Area, Perimeter and Type of a Triangle.

Problem Statement: Given 3 sides of a triangle, find the area, perimeter and determine the type of the triangle, if isosceles, equilateral, or scalene. Also, check for Right Angled Triangle. /*Skipping Acute and Obtuse triangle types.*/

Prompt 3 user inputs for sides of the triangle and a dialog to output.

Solution:

import javax.swing.JOptionPane;

public class Triangle {

	/**
	 * This is a class to determine if the given side lengths form a triangle.
	 * It lets the user know the type of the triangle based on the given side lengths.
	 * Also, it gives the Perimeter and Area of the triangle.
	 * @param args
	 */
	public static void main(String[] args) {

//		String sideA, sideB, sideC;
		double a,b,c;
		a = Double.parseDouble(JOptionPane.showInputDialog(null,"Please input side 1 length of the triangle: ", "Triangle Side 1", JOptionPane.QUESTION_MESSAGE));
		b = Double.parseDouble(JOptionPane.showInputDialog(null,"Please input side 2 length of the triangle: ", "Triangle Side 2", JOptionPane.QUESTION_MESSAGE));
		c = Double.parseDouble(JOptionPane.showInputDialog(null,"Please input side 3 length of the triangle: ", "Triangle Side 3", JOptionPane.QUESTION_MESSAGE));
		
		// For right angled triangle, as per mathematics, square of the hypotenuse is equal to the sum of the squares of the other 2 sides. h^2 = a^2 + b^2 where h is hypotenuse (can be any side a,b,c)
		// So we first need to determine the hypotenuse
		
		double h = a > b ? (a > c ? a : c) : (b > c ? b : c);
		
		// Permiter of the triangle
		double p = a + b + c, s = p/2;
		
		//Area of triangle
		double areaOfTriangle = Math.sqrt(s * (s-a) * (s-b) * (s-c));
		
		// Check to see if the triangle is equilateral -- All sides should be equal
		if(a == b && b == c){ // no need to check a == c the value always holds true.
			JOptionPane.showMessageDialog(null, "Based on the given sides, the triangle is a equilateral." +
					"\nPerimeter of the triangle is " + p + 
					"\nArea of Triangle is " + areaOfTriangle);
		} 
		// Check to see if the triangle is isosceles -- At least 2 sides should be equal
		else if(a == b || b == c || c == a) {
			JOptionPane.showMessageDialog(null, "Based on the given sides, the triangle is a isosceles." +
					"\nPerimeter of the triangle is " + p + 
					"\nArea of Triangle is " + areaOfTriangle);
		}
		// Check to see if the triangle is right angle -- Can be verified if sum of squares of each of the sides is equal to twice the square of the hypotenuse. 
		//Ex : 3^2 + 4^2 + 5^2 = 2 * h^2 where h is the hypotenuse
		else if(Math.pow(h,2) * 2 == Math.pow(a,2) + Math.pow(b,2) + Math.pow(c,2)) {
			JOptionPane.showMessageDialog(null, "Based on the given sides, the triangle is a right angled triangle." +
					"\nPerimeter of the triangle is " + p + 
					"\nArea of Triangle is " + areaOfTriangle);
		}// Check to see if the triangle is scalene -- no sides should be equal
		else if(a != b && b != c && a != c) {
			JOptionPane.showMessageDialog(null, "Based on the given sides, the triangle is scalene." +
					"\nPerimeter of the triangle is " + p + 
					"\nArea of Triangle is " + areaOfTriangle);
		}
		// Check if the triangle is not a triangle
		else if(a > b + c || b > a + c || c > a + b ) {
			JOptionPane.showMessageDialog(null, "Based on the given sides, the triangle is not a triangle");
		}
		else {
			JOptionPane.showMessageDialog(null, "Based on the given sides, the triangle is a normal triangle." +
					"\nPerimeter of the triangle is " + p + 
					"\nArea of Triangle is " + areaOfTriangle);
		}
	}

triangle

 

mailto: protocol with attachment in javascript?

Hello Folks,

It’s been quite a while I haven’t word pressing. I wanted to take some time out to blog a few helpful coding tips & tricks that I am coming across these days.

A few days back, my colleague had a requirement on opening a Outlook email using simple javascript which also includes a attachment to the outlook email. Well google’ing a bit found the answer to do so, but including a attachment to that is being hosted on a different server (OnBase Document Server) was a challenge.

Clicking this button below opens the Mail Draft Dialog Window (Mail is a default application for eMails in Mac OSX) / Outlook Draft Dialog Window (if Windows OS), with user set TO (sent by) email address, Subject Line (Outlook takes in maximum of 255 characters on Subject Line), Message Body. Note that the FROM (received from) email address will be decided by the default account set in Mail App/Outlook App.

mailTo

<a href="mailto:rc@rakeshchouhan.com?subject=Test%20Mail-To-Talk"></a>
According to RFC 2368 you can’t add an attachment to a message with the mailto: URL scheme due security reasons:

The user agent interpreting a mailto URL SHOULD choose not to create a message if any of the headers are considered dangerous; it may also choose to create a message with only a subset of the headers given in the URL. Only the Subject, Keywords, and Body headers are believed to be both safe and useful.

Conclusion:

mailto: only supports header values or text/plain content.

 

Happy learning 🙂

Convert a Maven project to eclipse project..

Given that a project is built in Maven, and you would like to import the same project in eclipse IDE. Or sometimes developers intentionally do not check in .project, .settings files to the repository. These files are generated by the eclipse IDE.

cd to the project directory

mvn eclipse:eclipse

Note: ensure that the project directory has pom.xml

Pascal’s Triangle with O(n^2) worst case.

public class PascalTriangle {
    
    public static void main(String[] args) {
        showPascal(9);
    }
    
    // This takes O(n^2) constraint.
    public static void showPascal(int rows){
    	// rows = Number of Pascal triangle rows to show up
    	// i = loop thru each row.
    	for(int i = 0; i<rows; i++)
    	{
    		// Start from 1. So, initialize the first number to 1
    		int number = 1;
    		// Give the spacing - Ex: If rows is 9, then the spacing  would 18 (because I specified the args as "", else if I specify args as "_", you would notice that the spacing is 17 and on 18th bit there would be a '_' ) for the first iteration of i = 0.
    		System.out.format("%"+(rows-i)*2+"s", "");
    		// j = loop thru  each column of a row by CALCULATing and display
    		for(int j=0; j<=i; j++)
    		{
    			// Give 3 more spacing and print the number on the 4th bit.
    			System.out.format("%4d", number);
    			
    			// Formula to calculate each column.
    			number = number * (i - j)/(j + 1);
    		}
    		// Print a empty line after each row.
    		System.out.println();
    	}
    }

Here is how the output look like:

pascaltriangleoutput

Happy Coding !!!

WebPage Loading & Rendering – How fast it that?

Hello There…

For the past few days, I was speed testing how fast my website loads and researching on how can I improve it. During this research, I came across many different ways and different techniques to improve a web page to load faster and render with a  very minimal memory footprint, from coding standpoint to server configuration.

Here are the metrics of my website’s performance, studied and tested with…

  1. Google Developers Page Speed Performance toolgoogledevelopersperformanceinsights
  2. Pingdom Website Speed Testpingdomspeedtest
  3. GTmetrix Performance Toolgtmetrixperformance

 

Notice that each test tool provides different performance test results. All the results are approximated based on their test strategy. However, there may be many other test tools to test out the website’s speed, but the important point to note is, these tools lets us know what went wrong and what can be done to improve it.

Here are some of things I had to do for improving..

Within HTML, JS & CSS files

  1. Minifying HTML, Javascript’s and CSS.
  2. Using ‘async’ and ‘defer’ (sometimes together where ever required) while loading javascript files.
  3. Inlining small CSS and scripting small JS within main document to minimize requests.
  4. Placing CSS in the document head.
  5. Sizing Content to Viewport.
  6. Serving Scaled images (If images are small sized, use data-uri’s instead)

      Within .htaccess file. (This file exists on the domain root folder)

  1. Leverage Browser Caching by specifying a “Cache-Control” to all Files Matching html, js, css, etc…
  2. Specifying a “Vary: Accept-Encoding header” to advise public proxies to store both compressed and uncompressed version of the resource.
  3. Specifying a ETag Header to validate Cache for all resources ending with file names.
  4. Ensuring landing page redirects are avoided (enabled by default)
  5. Ensuring gzip compression (enabled by default)
  6. Ensuring Keep-Alive is enabled (enabled by default in http.conf. If shared host, then we would have to set it manually in .htaccess)

Having done that, I do had some unanswered questions during this research.

  1. How to leverage browser caching andE-Tag (Cache Validator) to certain resources that do not end with file name in .htaccess file?Example for Resource URL’s:
    http://fonts.googleapis.com/css?family=Lato:400,700
    https://maps.googleapis.com/maps/vt?pb=!&#8230;

    The above resource URL’s DO NOT END with any file names.

  2. Since these resources are not cached by some proxy caching servers. How to remove query string and encode the parameters into the URL for resources having “?” (see resource URLs example from Q.1 above).
  3. How to prioritize visible content for rendering “above-fold-content” (as suggested in the Google developers page test tool), when your page is just one single page template?

Here are the resources that I was going through this research process..

 

Happy Learning 🙂

Well Known TCP/IP (Reserved) Ports

In TCP/IP and UDP networks, a port is an endpoint to a logical connection and the way a client program specifies a specific server program on a computer in a network. Some ports have numbers that are pre-assigned to them by the IANA, and these are called the “wellknown ports” which are specified in RFC 1700.

Port numbers range from 0 to 65536, but only ports numbers 0 to 1024 are reserved for privileged services and designated as wellknown ports. This list of wellknown port numbers specifies the port used by the server process as its contact port.

Note: Important ones are highlighted in bold.

Port Number Description
1 TCP Port Service Multiplexer (TCPMUX)
5 Remote Job Entry (RJE)
7 ECHO
18 Message Send Protocol (MSP)
20 FTP Data
21 FTP Control
22 SSH Remote Login Protocol
23 Telnet
25 Simple Mail Transfer Protocol
29 MSG ICP
37 Time
42 Host Name Server (Nameserv)
43 WhoIs
49 Login Host Protocol (Login)
53 Domain Name System (DNS)
69 Trivial File Transfer Protocol (TFTP)
70 Gopher Services
79 Finger
80 HTTP
103 Standard
108 SNA Gateway Access Server
109 POP2
110 POP3
115 Simple File Transfer Protocol (SFTP)
118 SQL Services
119 Newsgroup (NNTP)
137 NetBIOS Name Service
139 NetBIOS Datagram Service
143 Interim Mail Access Protocol (IMAP)
150 NetBIOS Session Service
156 SQL Server
161 SNMP
179 Border Gateway Protocol (BGP)
190 Gateway Access Control Protocol (GACP)
194 Internet Relay Chat (IRC)
197 Directory Location Service (DLS)
389 Lightweight Directory Access Protocol (LDAP)
396 Novell Netware over IP
443 HTTPS
444 Simple Network Paging Protocol (SNPP)
445 Microsoft-DS
458 Apple QuickTime
546 DHCP Client
547 DHCP Server
563 SNEWS
569 MSN
1080 Socks

@Courtesy: http://www.webopedia.com/quick_ref/portnumbers.asp

Happy Learning !!!

H5 – Are you about to add an image to your Web Application ? Think about self encoded data-uri’s.

There are 2 ways to add an image to your html page.

1) Add it inline using your tag within html file
2) Add it using CSS

Everyone knows how to do it the both ways, but the best way to do is by using base64 encoder and adding the content data uri to the image.

I use a simply encoder utility tool from WebSemantics @ http://websemantics.co.uk/online_tools/image_to_data_uri_convertor/

The above utility tool does not allow images with large sizes, and here is another tool which does the same..

http://www.askapache.com/online-tools/base64-image-converter/

However, there are many tools that are available in the market. You can also have your own base64 algorithm to encode the images for security purposes (like avoiding “HOT LINKING“).

Given the input image, this tool gives you a base64 encoded data, which you would want to use it to attach it to html or css.