I’ve got an exploit working against this binary running in a representative environment (i.e. same version of libc, ld-linux-x86-64, libpthread etc) but it’s not working against the challenge server. The challenge server is also not behaving the same as the binary I’ve downloaded. E.g. the show_gems function doesn’t appear to be included (or working), as it never prints out your current total in the menu. E.g. I never get anything like this over the network connection:
[*] Current ?: [70]
However, the behaviour of the app shows that the gem count is maintained internally.
[EDIT] I was being stupid. The show_gems function outputs to STDERR, which explains why I’m not seeing it on the output from the challenge server (which is only displaying STDOUT).