:::info
[room](https://tryhackme.com/r/room/reverselfiles)
:::

# Crackme1

用 IDA 打開後，小改一下程式

#include <stdio.h>
#include <string.h> 

int main() {
  char s[32]; // [rsp+10h] [rbp-90h] BYREF
  int v5[27]; // [rsp+30h] [rbp-70h]
  unsigned int i; // [rsp+9Ch] [rbp-4h]

  v5[0] = 37;
  v5[1] = 43;
  v5[2] = 32;
  v5[3] = 38;
  v5[4] = 58;
  v5[5] = 45;
  v5[6] = 46;
  v5[7] = 51;
  v5[8] = 30;
  v5[9] = 51;
  v5[10] = 39;
  v5[11] = 32;
  v5[12] = 51;
  v5[13] = 30;
  v5[14] = 42;
  v5[15] = 40;
  v5[16] = 45;
  v5[17] = 35;
  v5[18] = 30;
  v5[19] = 46;
  v5[20] = 37;
  v5[21] = 30;
  v5[22] = 36;
  v5[23] = 43;
  v5[24] = 37;
  v5[25] = 60;
  v5[26] = -65;
  

  memset(s, 65, 27);
  for (i = 0; i <= 0x1A; ++i)
    s[i] += (char)v5[i];
  
  puts(s);
  
  return 0;
}

flag{not_that_kind_of_elf}

# Crackme2

直接用 r2 打開看，就可以看到 password

┌──(kali㉿G)-[/mnt/d/Users/cheng/Downloads]
└─$ ./crackme2 super_secret_password
Access granted.
flag{if_i_submit_this_flag_then_i_will_get_points}

# Crackme3

用 r2 打開看發現這次的 password 變成 base64 ， decode 後就是這題答案

┌──(kali㉿G)-[/tmp]
└─$ echo "ZjByX3kwdXJfNWVjMG5kX2xlNTVvbl91bmJhc2U2NF80bGxfN2gzXzdoMW5nNQ==" | base64 -d
f0r_y0ur_5ec0nd_le55on_unbase64_4ll_7h3_7h1ng5

# Crackme4

觀察後可以發現是用 `strcmp` 做比較用 `ltrace` 追中，即可看到答案

┌──(kali㉿G)-[/mnt/d/Users/cheng/Downloads]
└─$ ./crackme4
Usage : ./crackme4 password
This time the string is hidden and we used strcmp

┌──(kali㉿G)-[/mnt/d/Users/cheng/Downloads]
└─$ ltrace ./crackme4 adsf
__libc_start_main(0x400716, 2, 0x7ffca957ed28, 0x400760 <unfinished ...>
strcmp("my_m0r3_secur3_pwd", "adsf")                                                            = 12
printf("password "%s" not OK\n", "adsf"password "adsf" not OK
)                                                        = 23
+++ exited (status 0) +++

# Crackme5

同上

┌──(kali㉿G)-[/mnt/d/Users/cheng/Downloads]
└─$  ./crackme5 adsf
Enter your input:
asdf
Good game

┌──(kali㉿G)-[/mnt/d/Users/cheng/Downloads]
└─$ ltrace ./crackme5 adsf
__libc_start_main(0x400773, 2, 0x7ffffac06388, 0x4008d0 <unfinished ...>
puts("Enter your input:"Enter your input:
)                                                                       = 18
__isoc99_scanf(0x400966, 0x7ffffac06220, 0, 0x7f324c3504e0

d
)                                     = 1
strlen("d")                                                                                     = 1
strlen("d")                                                                                     = 1
strncmp("d", "OfdlDSA|3tXb32~X3tX@sX`4tXtz2\177", 28)                                           = 21
puts("Good game"Good game
)                                                                               = 10
+++ exited (status 0) +++

ans:OfdlDSA|3tXb32~X3tX@sX`4tXtz2

# Crackme6

用 IDA 追中到這個 function　是做密碼檢查
分別把那些數值轉ASCII，得知密碼`1337_pwd`

# Crackme7

整個流程大致長這樣
其中追中到右下角那部分
可以發現拿到 flag 的神奇數字 `0x7a69`

┌──(kali㉿G)-[/mnt/d/Users/cheng/Downloads]
└─$ ./crackme7
Menu:

[1] Say hello
[2] Add numbers
[3] Quit

[>] 31337
Wow such h4x0r!
flag{much_reversing_very_ida_wow}

# Crackme8

分析完程式後，直接 patch 把原本的 `je 0x8048502` 改成 `jne 0x8048502`

┌──(kali㉿G)-[/mnt/d/Users/cheng/Downloads]
└─$ ./crackme8 asdf
Access granted.
flag{at_least_this_cafe_wont_leak_your_credit_card_numbers}