# AbstractFor the detailed version see the [Github page](https://github.com/KamilPacanek/writeups/blob/master/ctf/HTB.CA2021/passphrase.md).
## ToEWe are given the `passphrase` file.
## Analysis
First things first, analyze what we have with file:
```$ file passphrase 
passphrase: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked,interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=60f6b6064d2e34a2b6a24dda9feb943b0b8c360f, not stripped```
Symbols are left within the executable. This is good as it makes working with the file easier. Then I did quick lookups with `ns`, `objdump`, `ldd` and it helped me to establish that program compares user input with some string. So we need to find that string.
I'm using `strace` and `ltrace` having the latter one to show me the value I was looking for.
```strlen("\nTell me the secret passphrase: "...)                   = 32sleep(1)                                                         = 0fgets(dsada"dsada\n", 40, 0x7f8568531980)                             = 0x7ffc986e2da0strlen("dsada\n")                                                = 6strcmp("3xtr4t3rR3stR14L5_VS_hum4n5", "dsada")                   = -49printf("\033[31m")                                               = 5strlen("\nIntruder alert! \360\237\232\250\n")                   = 22```
So after presenting a secret passphrase, the executable gives us the flag:
```strlen("\nTell me the secret passphrase: "...)                   = 32sleep(1)                                                         = 0fgets(3xtr4t3rR3stR14L5_VS_hum4n5"3xtr4t3rR3stR14L5_VS_hum4n5\n", 40, 0x7f461a61c980)       = 0x7ffd79ab8ec0strlen("3xtr4t3rR3stR14L5_VS_hum4n5\n")                          = 28strcmp("3xtr4t3rR3stR14L5_VS_hum4n5", "3xtr4t3rR3stR14L5_VS_hum4n5") = 0puts("\342\234\224"✔)                                             = 4printf("\033[32m")                                               = 5printf("\nSorry for suspecting you, pleas"..., "3xtr4t3rR3stR14L5_VS_hum4n5"Sorry for suspecting you, please transfer this important message to the chief: CHTB{3xtr4t3rR3stR14L5_VS_hum4n5}```
## Solution> `CHTB{3xtr4t3rR3stR14L5_VS_hum4n5}`