packer

1. Trying file and strings:

   ```shell file out

   out: ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), statically linked, no section header ```

   Can't use GDB as file is stripped

   ```shell strings out

   . . UPX! UPX! ```

   Hmm... It is packed with UPX

2. Unpack:

   ```shell upx -d out file out

   out: ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), statically linked, BuildID[sha1]=fedfa2b06929b414534771a3fdd291559e1190b1, for GNU/Linux 3.2.0, not stripped ```

   "not stripped" yay! GDB time now

3. break at main, run, and disas:

   gdb . . 0x0000000000401f47 <+482>: test %eax,%eax 0x0000000000401f49 <+484>: jne 0x401f65 <main+512> . .

   The result of test seems to decide the final jump..

4. Change the value of $eax:

   ```gdb (gdb) b *main+482 Breakpoint 2 at 0x401f47 (gdb) c Continuing. Enter the password to unlock this file: random You entered: random

   Breakpoint 2, 0x0000000000401f47 in main () (gdb) set $rax=0 (gdb) c Continuing. Password correct, please see flag: 7069636f4354467b5539585f556e5034636b314e365f42316e34526933535f33373161613966667d ```

5. Convert hex to ASCII

   shell echo "7069636f4354467b5539585f556e5034636b314e365f42316e34526933535f33373161613966667d" | xxd -r -p