Exercise 2: Constructing C Code From x86 Assembly

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

Exercise - 2 Constructing C Code From x86 Assembly

In this article, we will look into the following assembly code, analyze it and try to construct the corresponding C code.

0000000000400546 <main>:
  400546:	push   rbp
  400547:	mov    rbp,rsp
  40054a:	sub    rsp,0x30
  40054e:	mov    rax,QWORD PTR fs:0x28
  400555:	00 00 
  400557:	mov    QWORD PTR [rbp-0x8],rax
  40055b:	xor    eax,eax
  40055d:	mov    DWORD PTR [rbp-0x20],0x6c707041
  400564:	mov    WORD PTR [rbp-0x1c],0x65
  40056a:	mov    DWORD PTR [rbp-0x24],0x0
  400571:	jmp    40058a <main+0x44>
  400573:	mov    eax,DWORD PTR [rbp-0x24]
  400576:	cdqe   
  400578:	movzx  edx,BYTE PTR [rbp+rax*1-0x20]
  40057d:	mov    eax,DWORD PTR [rbp-0x24]
  400580:	cdqe   
  400582:	mov    BYTE PTR [rbp+rax*1-0x10],dl
  400586:	add    DWORD PTR [rbp-0x24],0x1
  40058a:	mov    eax,DWORD PTR [rbp-0x24]
  40058d:	cdqe   
  40058f:	movzx  eax,BYTE PTR [rbp+rax*1-0x20]
  400594:	test   al,al
  400596:	jne    400573 <main+0x2d>
  400598:	mov    eax,DWORD PTR [rbp-0x24]
  40059b:	cdqe   
  40059d:	mov    BYTE PTR [rbp+rax*1-0x10],0x0
  4005a2:	mov    eax,0x0
  4005a7:	mov    rcx,QWORD PTR [rbp-0x8]
  4005ab:	xor    rcx,QWORD PTR fs:0x28
  4005b2:	00 00 
  4005b4:	je     4005bb <main+0x75>
  4005b6:	call   400420 <__stack_chk_fail@plt>
  4005bb:	leave  
  4005bc:	ret    
  4005bd:	nop    DWORD PTR [rax]

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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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