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Welcome back.

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In this lesson we are going to learn patching.

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This involves assembling and opening instructions.

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Also known as know Operation Instructions And the pitching process itself.

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So let us begin that is open this in SCC for the DG.

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Now we run to the entry point F nine

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and then we look for the string.

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Try to and put breakpoint here and applying there.

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It is supposed to jump

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in our last ness and we saw that we should not allow this junk to take place.

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It is jump happens if we display the that message.

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What we want is for the jam not to take place.

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Instead we want it to go to the next score which will show the good message which is our flag itself

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and then what we did was we toggle the zero fly like this so that the jam will not take place.

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So if the jam will not take place the call to show the good message will happen.

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However when we toggle the flag like this it is only temporary.

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It is not permanent.

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Let me demonstrate that is putting the breakpoint here first.

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Then we run to the break point now in the jam will be taken by let us target the flag.

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Ending click on F it and as you can see the flag is shown but if we were to re restart and rerun the

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program this toggle will be reverted back to is default state less.

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Let's take a oh if I were to rerun the flag again if I would rerun today jam again.

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Notice that the jump again will be taken and we again have to toggle the fly so in order to well why

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having to keep toggling the flight every time we run we can't make it permanent.

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So the way we may keep a million years we have to modify the instruction here so there is an instruction

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which you can use in order to remove this instruction and the instruction is call and Opie

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annual P stands for no operation instruction so we can substitute this and will be.

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So that this instruction will never take place.

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To substitute this you would be we double click it or press the spacebar here.

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Make sure that we check the feel of you know ops checkbox and then we type and would be in here.

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You can type it in uppercase or lowercase.

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It doesn't matter and then press.

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Okay.

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So now close this dialog box and you can see the jam instruction has been replaced you to anarchy.

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Why does it replace you to any B.

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Because the already doing jam instruction used up two bytes so we need to replace the two bytes.

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That is why we have two annual B's so now that we have replace the jam instruction entropy.

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We do not have to bother about the zero flat anymore.

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So to make this permanent we can save this E C executable as a new file.

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So to do that we click on file so petrified.

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And then here it gives you a summary of the purchase.

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So there are two batches.

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One person is here and then a batch is here so let's bashful.

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Click on the button batch file.

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And then give a new name to your new file.

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Have you choose your own name and append the dash

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best behind the name notice you have to maintain the DOT ESEA extension because it is an executable

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file.

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Click on safe to save the file click OK and close these data.

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Now you can test your new found by openly and selecting the best file

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just say yes.

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Yes again.

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And now your new batch file has been loaded to memory loaded into a 64 DB e.g. click on F nine to run

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to the entry point and now you at the entry point.

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So if you scroll down and look at the string you will see that the did.

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Previously there was a jump but we have replace it with and will be and in entropy still maintains meaning

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that it is not permanent.

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We do not have to use any zero flag toggling zoo of flight any more so over here we can put a jump put

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a breakpoint you can put a breakpoint over here or over here or any way here so that the program will

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pass and show us the output of the new message which is supposed to be the fly.

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So let's put a breakpoint maybe over here and then run to this a breakpoint by pressing f 9.

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So now we add a call if we were to f it.

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Now you execute in the column press F it and see the output in the terminal F it and you can see brings

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the flight to the terminal.

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So this is now permanent if I would remove the breakpoint however and rerun it

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f 9 to go to an entry point and notice nowadays no breakpoint.

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If I were to rerunning you execute and terminate the program because there is nothing to stop it.

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So we still need to have a breakpoint.

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So let's try again.

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Restart run to entry point by F 9 by pressing f 9 and then make sure you're going put your breakpoint

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at the

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somewhere.

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Here

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and then run to the breakpoint by pressing f 9.

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Then press TV to see the output OK so we still need to have a point in order to pass a program at the

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correct place to see the output and other place to put a brake line is to put it after the car so you

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can put a brake point maybe over here oh we're here any way you like so we can put a brake line here

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even or here.

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So let's put a breakpoint point here so you put a breakpoint here.

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Now let me try and we run

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press F nine to go the entry point.

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Press 7 9 to run to the brake point.

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You can see immediately Schuster print up on the terminal because how brake mine is after the car.

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So this car is executed.

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And then he shows this flag.

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Then he comes to the jump the jungle jump over the back message and go to our break point here and stop.

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OK so this is how we patch our file using the uh no instruction to overwrite or remove any jam that

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we do not want to happen.

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And patching itself requires to use all the command file Bashar OK.

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So now I'm going to pose a challenge to you and you know you can try to solve it as an exercise in patching.

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So at a moment if you were to remove any brake breakpoint and run as I mentioned earlier it will not

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pass you will just run execute showed a message and quickly close the program.

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So can you find a way to patch the program so that when you're running it will stop it will stop at

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message.

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Oh here it message we show a message and you will not create so.

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Can you do that.

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So if at a moment if you will decide you running from command line you will also not stop at the message.

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Let me show you if I want to go to

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if I were to run the page file

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notice that he execute and it doesn't display anything and increase so can you now find a way to test

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and file so that he will show the message and stop the and not can we not exit the program OK.

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So just try to push too far in such a way that he will run should the flag.

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Yes sir.

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Boss nay we thought exiting and without using any bricks.

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So many break points.

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So that is a challenge for you to try try to solve it.

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And I will show you the solution in the next lesson.

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I will give you a tip if you won the program not to quit but to stopping short the message you should

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use Jan So that's to him you should patch the file with Jan so early on I told you how to test your

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file using and would be so I repeat it in order to pacify you might.

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That.

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Or spacebar and then type in whatever new instructions you want to use to to overwrite the earlier instruction

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and English okay.

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Make sure you check this box.

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That is very important.

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Check this.

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So this process of overriding the or changing or modifying an existing instruction is also known as

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assembling so when you when you assemble you are actually changing the instruction which is already

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day OK.

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So that's the issue now modifying this to jam some way so that you will not create a program.

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So give it a try.

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See you in this lesson.

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Thank you for watching.