Incorporate the OpenSMTPD' privsep crypto engine. The idea behind
it is to never load the certificate' private keys in a networked
process, instead they are loaded in a separate process (the `crypto'
one) which signs payloads on the behalf of the server processes.
This way, we greatly reduce the risk of leaking the certificate'
private key should the server process be compromised.
This currently compiles only on LibreSSL (portable fix is in the
way).
avoids issues since the same file is sent to multiple processes
after being dup()'ed. Since these files are meant to be regular
files, I don't expect short reads.
Was temporarly disabled during the transition to real privsep.
While here, fix a memory leak when using `require client ca'.
Also, avoid leaking info about the parent address space layout to
server processes by not sending pointer values.
It uses the 'common' proc.c from various OpenBSD-daemons.
gmid grew organically bit by bit and it was also the first place where I
tried to implement privsep. It wasn't done very well, in fact the
parent process (that retains root privileges) just fork()s a generation
of servers, all sharing *exactly* the same address space. No good!
Now, we fork() and re-exec() ourselves, so that each process has a fresh
address space.
Some features (require client ca for example) are temporarly disabled,
will be fixed in subsequent commits. The "ge" program is also
temporarly disabled as it needs tweaks to do privsep too.
