Question

Is it possible to pack an executable into a shared library and upon calling a function inside the said library:

• unpack the executable
• use the executable through fork

The reason I am asking is because I was recently faced with a situation where my shared library was being loaded in a “sandbox” environment (maybe chroot based) and I would have really like the possibility of spawning a separate process for an executable (loose coupling).

Answer 1

As long as you have permission to write to a directory on a filesystem that isn’t mounted noexec, then you could just store the executable in a large array of unsigned char and write it out with fwrite, then use fork/exec to run it.

Really though, the best solution is just to use fork() without exec – just have the child side call into a different function after the fork() (and then exit with _exit() when that function is done).