Srijan Rooftop

Srijan Addas

So you're eager to learn about pointers but unfortunately you got stuck because they seemed to you terrible in nature? That's not true I know, but many of the people get confused when they arrive at the topic of pointers. Well pointers are the most important tools in C programming and are the one that can make you fly (unless you don't know how to ride over them). In this article we're going to learn basics of pointers.

Pointers are the varaibles that store addresses of other variables. Easy ain't it?

So lets start with the decleration of a pointer, pointer is decreleared as:

data_type *var_name;
e,g
int *pt;

well the astrisk(*) before the variable name is the thing that makes variable a pointer. So far so good now what?
Now lets say we want to store address of a variable in our pointer variable that seems pretty complex..!

Let's do it:

int number = 100;
int *pt = &num;

Is it really complex..?
what we are doing here is that we are first declaring and initializing a integer variable (number) with value of 100 and then we declare and initialize a pointer variable (pt) with the address of number variable. Now pt (pointer variable) contains the address of number (integer varaible). So what? Now we can use this pointer variable to change the value of number variable. Is this some kind of Magic? Maybe. Lets' do it:

*pt = 200;

what we have done here is that we De-referencing the pt variable with the asterisk (*) and then assigned it the value of 200 now the number variable contains 200. Isn't it a magic? De-referencing is used for accessing the value of the variable towards which our pointer is pointing simple. So lets write a full program of what we have learned so far.

/*Pointer Basics: Creating and Using Pointers*/
#include<stdio.h>
int main(void){
int number = 100;
int *pt = &number;
printf("Value of 'number' is: %d", number);
printf("Address of 'number' is: %p", pt);
*pt = 200;
printf("New value of 'number' is: %d", number);
return 0;
}

What this whole program did was it created a integer variable and a pointer to integer variable and then printed out the value and address of the 'number' variable and after that we De-referenced the pointer variable so that we can access the value to which our pointer variable is pointing and changed the old 100 value with new 200 value and at last we printed that out. Easy isn't it?
But do you know that you can get the address of a variable even by using ampersand (&) operator? Lemme show you how. I'll declare and initialize a variable 'var' and then print it to screen using ampersand (&) operator:

int var = 10;
printf("Address of 'var' is %p\n", &var);

the last statement here will print out the address of 'var' not value so that means it is equal to this statement:

int *pt = &var;
printf("Address of 'var' is %p\n", pt);

here we first assigned the address of 'var' to pointer variable 'pt' and then printed out the address of 'var' using the pointer variable (pt).
So lets write another program that will wrap up this part of 'Pointer Basics':

/*Pointer Basics Part 1: Program 2*/
#include<stdio.h>
int main(void){
   int var = 10;
   int *pt = &var;
   printf("The Value of 'var' is: %d\n", var);
   printf("De-referencing: *pt = %d\n", *pt);
   printf("Ampersand: The Address of 'var' is %p\n", &var);
   printf("pt = %p\n", pt);
   return 0;
}

So that's the end of first part watch out for the next part in which we'll tighten our grip on pointers and get ready for some Advanced '*po(inter)-fo'.

We had an overwhelming turnout out of submissions for Call for Papers and Call for Training for the OWASP Global AppSec DC 2019 (formerly AppSec USA) We want to give each submission the time deserved to evaluate each before choosing. Keeping that in mind the notifications of acceptance and thanks will be CHANGED to July 1, 2019. We appreciate your understanding and patience in this matter.

https://dc.globalappsec.org/

Connecting Hardware to Your Real Car:

I realized the other day I posted Part 2 of this series to my youtube awhile ago but not blogger so this one will be quick and mostly via video walkthrough. I often post random followup videos which may never arrive on this blog. So if you're waiting on something specific I mentioned or the next part to a series its always a good idea to subscribe to the YouTube. This is almost always true if there is video associated with the post.

In the last blog we went over using virtual CAN devices to interact with a virtual car simulators of a CAN network This was awesome because it allowed us to learn how to interact with he underlying CAN network without fear of hacking around on an expensive automobile. But now it's time to put on your big boy pants and create a real CAN interface with hardware and plug your hardware device into your ODB2 port.

The video I created below will show you where to plug your device in, how to configure it and how to take the information you learned while hacking around on the virtual car from part1 and apply it directly to a real car.

Video Walk Through Using Hardware on a Real Car

As a reference here are the two device options I used in the video and the needed cable:

Hardware Used:

Get OBD2 Cable:
https://amzn.to/2QSmtyL

Get CANtact:
https://amzn.to/2xCqhMt

Get USB2CAN:
https://shop.8devices.com/usb2can

Creating Network Interfaces:

As a reference here are the commands from the video for creating a CAN network interface:

USB2Can Setup:

The following command will bring up your can interface and you should see the device light color change:

sudo ip link set can0 up type can bitrate 125000

Contact Setup:

Set your jumpers on 3,5 and 7 as seen in the picture in the video

Sudo slcand -o -s6 /dev/ttyACM can0 <— whatever device you see in your DMESG output

Ifconfig can0 up

Summary:

That should get you started connecting to physical cars and hacking around. I was also doing a bit of python coding over these interfaces to perform actions and sniff traffic. I might post that if anyone is interested. Mostly I have been hacking around on blockchain stuff and creating full course content recently so keep a look out for that in the future.

Srijan Rooftop

Wednesday, May 31, 2023

Pointers Part 1: The Basics

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ANNOUNCEMENT: Submitters Of Papers And Training For Global AppSec DC 2019 (Formerly AppSec USA)

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Tuesday, May 30, 2023

Hacking All The Cars - Part 2

Connecting Hardware to Your Real Car:

Video Walk Through Using Hardware on a Real Car

Hardware Used:

Creating Network Interfaces:

Summary:

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