Disable calling functions in transitive dependencies, force them to be direct dependencies.

Why should sshd be allowed to call an xz function directly without xz being an immediate dependency.

I'm not sure what all that would entail with the ifunc stuff, but I remember encountering a glibc linking change moving from Red Hat 6 to RH7 that did something similar and broke the build process for some legacy code.

> what technology could be implemented to mitigate this type of attack (beyond sshd)?

UNIX ? (do one thing and do it well).

When your program links with 20 libraries, i have i very hard time to believe that security is one of your goals.

See: Qubes OS.