Solution by cetfor: Hey, here's my solution for Sh4ll1. I appreciate the thoughtful introductory challenge which are often difficult to make fun. You've done that by requiring some interesting inspection and knowledge of the stack. Thanks!
Solution by elprofesor: you will find a "readme.md" which explains everything, a "main_disassemble.txt", "systemv_disassemble.txt", "systemo_disassemble.txt" with comments at every important line that helped me to find the password. Hope it helps. Cheers!