Exercise 4: Constructing C Code From x86 Assembly

by | May 31, 2022 | Exclusive Articles, Featured, Reverse Engineering

Exercise - 4 Constructing C Code From x86 Assembly

In this article, we will look into the x86 assembly code, analyze it and try to construct the corresponding C code. Let’s first look into the following piece of x86 assembly code:

0000000000400546 <main>:
  400546:	push   rbp
  400547:	mov    rbp,rsp
  40054a:	sub    rsp,0x20
  40054e:	mov    rax,QWORD PTR fs:0x28
  400555:	00 00 
  400557:	mov    QWORD PTR [rbp-0x8],rax
  40055b:	xor    eax,eax
  40055d:	mov    BYTE PTR [rbp-0x15],0x61
  400561:	mov    DWORD PTR [rbp-0x14],0x0
  400568:	jmp    40057b <main+0x35>
  40056a:	mov    eax,DWORD PTR [rbp-0x14]
  40056d:	cdqe   
  40056f:	movzx  edx,BYTE PTR [rbp-0x15]
  400573:	mov    BYTE PTR [rbp+rax*1-0x10],dl
  400577:	add    DWORD PTR [rbp-0x14],0x1
  40057b:	cmp    DWORD PTR [rbp-0x14],0x4
  40057f:	jle    40056a <main+0x24>
  400581:	mov    eax,0x0
  400586:	mov    rcx,QWORD PTR [rbp-0x8]
  40058a:	xor    rcx,QWORD PTR fs:0x28
  400591:	00 00 
  400593:	je     40059a <main+0x54>
  400595:	call   400420 <__stack_chk_fail@plt>
  40059a:	leave  
  40059b:	ret    
  40059c:	nop    DWORD PTR [rax+0x0]

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Amrita Mitra

Author

Ms. Amrita Mitra is an author, who has authored the books “Cryptography And Public Key Infrastructure“, “Web Application Vulnerabilities And Prevention“, “A Guide To Cyber Security” and “Phishing: Detection, Analysis And Prevention“. She is also the founder of Asigosec Technologies, the company that owns The Security Buddy.

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