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Author: kunalvarudkar

Shellcode/HelloWorld_shellcode/Helloworld_shellcode

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+; Program Name: Helloworld_shellcode.nasm
+; Author: Kunal Varudkar
+
+; Purpose: Understanding the JMP-CALL-POP technique to dynamically use the memory address for shell coding :)
+
+
+global _start
+
+
+section .text
+
+_start:
+
+	JMP short call_shellcode
+
+shellcode:
+	
+	; print code 
+
+	xor eax, eax			; xor-ing to omit bad character (0x00) in op-code
+	mov al, 0x4			; sys call for printf
+	
+	xor ebx, ebx
+	mov bl, 0x1			; stdout=1
+
+	pop ecx				; poping the the address of next instruction into ecx 
+
+	xor edx, edx			
+	mov dl, 27			; length of message
+	int 0x80			; calling interrupt to execute syscall
+	
+	; exit code
+
+	xor eax, eax
+	mov al, 0x1			; syscall for exit
+	int 0x80			; calling interruptto execute syscall
+
+call_shellcode:
+
+	call shellcode
+	message:	db	"Hello world in shellcode!!", 0xA