OpenBSD implements a vulnerability exploitation protection technique based on randomly relinking the sshd executable file at each system boot. Previously, a similar relinking technique was applied to the kernel and the libraries libc.so, libcrypto.so, and ld.so; now it will also be applied to certain executable files. This method is also planned to be implemented for ntpd and other server applications in the near future. The change has already been included in the CURRENT branch and will be offered in the OpenBSD 7.3 release.
Relinking makes the offsets of functions in libraries less predictable, which complicates the creation of exploits that use return-oriented programming (ROP) methods. When using ROP techniques, the attacker does not try to place their code in memory but instead operates with pieces of machine instructions already present in loaded libraries that end with return control instructions (usually the ends of library functions). The exploit’s operation is reduced to constructing a chain of calls to similar blocks (‘gadgets’) to obtain the desired functionality.
Source: opennet.ru
