#!/bin/rc

# This script generates and stores DKIM keypair, using the correct user
# It outputs all paths generated in the following order for each algorithm:
#  - privkey
#  - txt record to be used in dns
#
# Example/intended usage:
#  dkimfiles = `$nl{dkim/mkcert <selector>}
#  rsakey    = $dkimfiles(1)
#  rsatxt    = $dkimfiles(2)
#  edkey     = $dkimfiles(3)
#  edtxt     = $dkimfiles(4)

dir        = /etc/mail/dkim
user       = _dkimsign
selector   = $1
ed         = ed25519
rsaprivkey = $dir/$selector.rsa.priv.key
rsapubkey  = $dir/$selector.rsa.pub.key
rsatxt     = $dir/$selector.rsa.txt
edprivkey  = $dir/$selector.$ed.priv.key
edpubkey   = $dir/$selector.$ed.pub.key
edtxt      = $dir/$selector.$ed.txt

files      = ( $rsaprivkey $rsapubkey $rsatxt \
               $edprivkey  $edpubkey  $edtxt  )

fn err {
	echo $* >[1=2]
}

fn die {
	err fatal error: $*
	exit 1
}

fn as {
	doas -u $user $*
}

fn mustsucceed {
	if (!$*) {
		err fatal error: essential command failed
		cleanupfailed
		exit 1
	}
}

fn cleanupfailed {
	for (f in $files) {
		as rm $f [2]>/dev/null
	}
}

if (!~ $#* 1) {
	err 'usage: dkim/mkcert <selector>'
	exit 2
}

for (f in $files) {
	as test -e $f && die $f already exists
}

mustsucceed as mkdir -p $dir

# RSA
mustsucceed as openssl genrsa -out $rsaprivkey
mustsucceed as openssl rsa -in $rsaprivkey -pubout | \
	mustsucceed as tee $rsapubkey >/dev/null
mustsucceed as cat $rsapubkey | \
	mustsucceed as sed '1s/.*/v=DKIM1;p=/;:nl;${s/-----.*//;q;};N;s/\n//g;b nl;' | \
	mustsucceed as tee $rsatxt >/dev/null

# ED25519
mustsucceed as openssl genpkey -algorithm $ed -out $edprivkey
mustsucceed as openssl pkey -outform DER -pubout -in $edprivkey | \
	mustsucceed tail -c +13 | mustsucceed openssl base64 | \
	mustsucceed as tee $edpubkey >/dev/null
mustsucceed printf 'v=DKIM1;k=%s;p=%s\n' $ed `$nl{mustsucceed as cat $edpubkey} | \
	mustsucceed as tee $edtxt >/dev/null

err 'Paths generated (rsa privkey, rsa dns record, ed25519 privkey, ed25519 dns record):'
echo $rsaprivkey
echo $rsatxt
echo $edprivkey
echo $edtxt