Linux C++ 调试神技--如何将Linux C++ 可执行文件逆向工程到Intel格式汇编

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Linux C++ 调试神技--如何将Linux C++ 可执行文件逆向工程到Intel格式汇编

 

对于许多在windows 上调试代码的人而言, Intel IA32格式的汇编代码可能并不陌生,因为种种的原因,很多软件工程师不得不去尝试理解汇编代码。Windows PE的反汇编格式默认是Intel格式的,但是由于历史的原因,在这个世界上还存在另外一种汇编,ATT格式,这也是Linux C++ 可执行代码的默认反汇编格式。

 

难道还真需要哥们学习两种格式的汇编么?一种学会了已经很NB了?

 

难道哥们在Windows上学的汇编到Linux上就白费了么?玩不转了么?

 

底层的处理器都是一个架构的,机器码都是一样的,这两种汇编代码一定可以互相转换,否则工具设计者智商一定低到写不出来工具。

 

对于这个问题且听兄弟以一个例子详细到道来。假设有如下的C++代码,我们将其在Linux上编译为一个名字为hellod的执行文件。

1    #include<iostream>
2    int main()
3    {
4    std::cout << "Enter two numbers:" << std::endl;
5    int v1 = 0, v2 = 0;
6    std::cin >> v1 >> v2;
7    std::cout << "The sum of " << v1 << " and " << v2
8    << " is " << v1 + v2 << std::endl;
9    return 0;
10    }

如果想看看现在的默认反汇编格式是什么,可以使用如下命令,可以看到Linux默认的是ATT格式的

(gdb) show disassembly-flavor
The disassembly flavor is "att".

反汇编结果如下:

(gdb) disassemble main
Dump of assembler code for function main():
   0x000000000040092d <+0>:    push   %rbp
   0x000000000040092e <+1>:    mov    %rsp,%rbp
   0x0000000000400931 <+4>:    push   %r13
   0x0000000000400933 <+6>:    push   %r12
   0x0000000000400935 <+8>:    push   %rbx
   0x0000000000400936 <+9>:    sub    $0x18,%rsp
   0x000000000040093a <+13>:    mov    $0x400ad4,%esi
   0x000000000040093f <+18>:    mov    $0x6011a0,%edi
   0x0000000000400944 <+23>:    callq  0x400800 <[email protected]>
   0x0000000000400949 <+28>:    mov    $0x400830,%esi
   0x000000000040094e <+33>:    mov    %rax,%rdi
   0x0000000000400951 <+36>:    callq  0x400820 <[email protected]>
   0x0000000000400956 <+41>:    movl   $0x0,-0x28(%rbp)
   0x000000000040095d <+48>:    movl   $0x0,-0x24(%rbp)
   0x0000000000400964 <+55>:    lea    -0x28(%rbp),%rax
   0x0000000000400968 <+59>:    mov    %rax,%rsi
   0x000000000040096b <+62>:    mov    $0x601080,%edi
   0x0000000000400970 <+67>:    callq  0x400810 <[email protected]>
   0x0000000000400975 <+72>:    lea    -0x24(%rbp),%rdx
   0x0000000000400979 <+76>:    mov    %rdx,%rsi
   0x000000000040097c <+79>:    mov    %rax,%rdi
---Type <return> to continue, or q <return> to quit---
   0x000000000040097f <+82>:    callq  0x400810 <[email protected]>
   0x0000000000400984 <+87>:    mov    -0x28(%rbp),%edx
   0x0000000000400987 <+90>:    mov    -0x24(%rbp),%eax
   0x000000000040098a <+93>:    lea    (%rdx,%rax,1),%r13d
   0x000000000040098e <+97>:    mov    -0x24(%rbp),%ebx
   0x0000000000400991 <+100>:    mov    -0x28(%rbp),%r12d
   0x0000000000400995 <+104>:    mov    $0x400ae7,%esi
   0x000000000040099a <+109>:    mov    $0x6011a0,%edi
   0x000000000040099f <+114>:    callq  0x400800 <[email protected]>
   0x00000000004009a4 <+119>:    mov    %r12d,%esi
   0x00000000004009a7 <+122>:    mov    %rax,%rdi
   0x00000000004009aa <+125>:    callq  0x4007a0 <[email protected]>
   0x00000000004009af <+130>:    mov    $0x400af3,%esi
   0x00000000004009b4 <+135>:    mov    %rax,%rdi
   0x00000000004009b7 <+138>:    callq  0x400800 <[email protected]>
   0x00000000004009bc <+143>:    mov    %ebx,%esi
   0x00000000004009be <+145>:    mov    %rax,%rdi
   0x00000000004009c1 <+148>:    callq  0x4007a0 <[email protected]>
   0x00000000004009c6 <+153>:    mov    $0x400af9,%esi
   0x00000000004009cb <+158>:    mov    %rax,%rdi
   0x00000000004009ce <+161>:    callq  0x400800 <_ZStlsISt11char_traitsIcEERSt13---Type <return> to continue, or q <return> to quit---
[email protected]>
   0x00000000004009d3 <+166>:    mov    %r13d,%esi
   0x00000000004009d6 <+169>:    mov    %rax,%rdi
   0x00000000004009d9 <+172>:    callq  0x4007a0 <[email protected]>
   0x00000000004009de <+177>:    mov    $0x400830,%esi
   0x00000000004009e3 <+182>:    mov    %rax,%rdi
   0x00000000004009e6 <+185>:    callq  0x400820 <[email protected]>
   0x00000000004009eb <+190>:    mov    $0x0,%eax
   0x00000000004009f0 <+195>:    add    $0x18,%rsp
   0x00000000004009f4 <+199>:    pop    %rbx
   0x00000000004009f5 <+200>:    pop    %r12
   0x00000000004009f7 <+202>:    pop    %r13
   0x00000000004009f9 <+204>:    pop    %rbp
   0x00000000004009fa <+205>:    retq   
End of assembler dump.

那如果我看不懂,我想使用Intel格式的汇编怎么办呢?下面的命令就可以做到,牛X吧?哈哈

(gdb) set disassembly-flavor intel 
(gdb) show disassembly-flavor
The disassembly flavor is "intel".

再来看看这下我们反出来的汇编代码, 已经变成Intel 格式的了

(gdb) disassemble main
Dump of assembler code for function main():
   0x000000000040092d <+0>:    push   rbp
   0x000000000040092e <+1>:    mov    rbp,rsp
   0x0000000000400931 <+4>:    push   r13
   0x0000000000400933 <+6>:    push   r12
   0x0000000000400935 <+8>:    push   rbx
   0x0000000000400936 <+9>:    sub    rsp,0x18
   0x000000000040093a <+13>:    mov    esi,0x400ad4
   0x000000000040093f <+18>:    mov    edi,0x6011a0
   0x0000000000400944 <+23>:    call   0x400800 <[email protected]>
   0x0000000000400949 <+28>:    mov    esi,0x400830
   0x000000000040094e <+33>:    mov    rdi,rax
   0x0000000000400951 <+36>:    call   0x400820 <[email protected]>
   0x0000000000400956 <+41>:    mov    DWORD PTR [rbp-0x28],0x0
   0x000000000040095d <+48>:    mov    DWORD PTR [rbp-0x24],0x0
   0x0000000000400964 <+55>:    lea    rax,[rbp-0x28]
   0x0000000000400968 <+59>:    mov    rsi,rax
   0x000000000040096b <+62>:    mov    edi,0x601080
   0x0000000000400970 <+67>:    call   0x400810 <[email protected]>
   0x0000000000400975 <+72>:    lea    rdx,[rbp-0x24]
   0x0000000000400979 <+76>:    mov    rsi,rdx
   0x000000000040097c <+79>:    mov    rdi,rax
---Type <return> to continue, or q <return> to quit---
   0x000000000040097f <+82>:    call   0x400810 <[email protected]>
   0x0000000000400984 <+87>:    mov    edx,DWORD PTR [rbp-0x28]
   0x0000000000400987 <+90>:    mov    eax,DWORD PTR [rbp-0x24]
   0x000000000040098a <+93>:    lea    r13d,[rdx+rax*1]
   0x000000000040098e <+97>:    mov    ebx,DWORD PTR [rbp-0x24]
   0x0000000000400991 <+100>:    mov    r12d,DWORD PTR [rbp-0x28]
   0x0000000000400995 <+104>:    mov    esi,0x400ae7
   0x000000000040099a <+109>:    mov    edi,0x6011a0
   0x000000000040099f <+114>:    call   0x400800 <[email protected]>
   0x00000000004009a4 <+119>:    mov    esi,r12d
   0x00000000004009a7 <+122>:    mov    rdi,rax
   0x00000000004009aa <+125>:    call   0x4007a0 <[email protected]>
   0x00000000004009af <+130>:    mov    esi,0x400af3
   0x00000000004009b4 <+135>:    mov    rdi,rax
   0x00000000004009b7 <+138>:    call   0x400800 <[email protected]>
   0x00000000004009bc <+143>:    mov    esi,ebx
   0x00000000004009be <+145>:    mov    rdi,rax
   0x00000000004009c1 <+148>:    call   0x4007a0 <[email protected]>
   0x00000000004009c6 <+153>:    mov    esi,0x400af9
   0x00000000004009cb <+158>:    mov    rdi,rax
   0x00000000004009ce <+161>:    call   0x400800 <_ZStlsISt11char_traitsIcEERSt13---Type <return> to continue, or q <return> to quit---
[email protected]>
   0x00000000004009d3 <+166>:    mov    esi,r13d
   0x00000000004009d6 <+169>:    mov    rdi,rax
   0x00000000004009d9 <+172>:    call   0x4007a0 <[email protected]>
   0x00000000004009de <+177>:    mov    esi,0x400830
   0x00000000004009e3 <+182>:    mov    rdi,rax
   0x00000000004009e6 <+185>:    call   0x400820 <[email protected]>
   0x00000000004009eb <+190>:    mov    eax,0x0
   0x00000000004009f0 <+195>:    add    rsp,0x18
   0x00000000004009f4 <+199>:    pop    rbx
   0x00000000004009f5 <+200>:    pop    r12
   0x00000000004009f7 <+202>:    pop    r13
   0x00000000004009f9 <+204>:    pop    rbp
   0x00000000004009fa <+205>:    ret    
End of assembler dump.

 

总结

对于很多计算机工程领域的技术问题,理解原理是最重要的,软件工程师很忙,忙着学东西,但是有的东西你一旦知道了道理,靠分析已经能节省很多的时间,根本不用去再学一遍,就拿本例来说,如果不去分析,再去学一遍另一个版本的,可能也是事倍功半,站的高方能望的远,和大家共勉。