This splits the user authentication code from the sshd-session
binary into a separate sshd-auth binary. This will be executed by
sshd-session to complete the user authentication phase of the
protocol only.
Splitting this code into a separate binary ensures that the crucial
pre-authentication attack surface has an entirely disjoint address
space from the code used for the rest of the connection. It also
yields a small runtime memory saving as the authentication code will
be unloaded after thhe authentication phase completes.
Joint work with markus@ feedback deraadt@
Tested in snaps since last week
OpenBSD-Commit-ID: 9c3b2087ae08626ec31b4177b023db600e986d9c
Not all systems with Solaris privs have priv_basicset so factor that
out and provide backward compatibility code. Similarly, not all have
PRIV_NET_ACCESS so wrap that in #ifdef. Based on code from
alex at cooperi.net and djm@ with help from carson at taltos.org and
wieland at purdue.edu.
