more work on making the bash scripts readable

setup/ssl.sh

@@ -2,7 +2,7 @@
 #
 # SSL Certificate
 # ---------------
-#
+
 # Create a self-signed SSL certificate if one has not yet been created.
 #
 # The certificate is for PRIMARY_HOSTNAME specifically and is used for:
@@ -22,29 +22,31 @@ source /etc/mailinabox.conf # load global vars
 apt_install openssl
 
 mkdir -p $STORAGE_ROOT/ssl
-# Generate a new private key if one doesn't already exist.
+# Generate a new private key.
 # Set the umask so the key file is not world-readable.
 if [ ! -f $STORAGE_ROOT/ssl/ssl_private_key.pem ]; then
 	(umask 077; hide_output \
 		openssl genrsa -out $STORAGE_ROOT/ssl/ssl_private_key.pem 2048)
 fi
 
-# Generate a certificate signing request if one doesn't already exist.
+# Generate a certificate signing request.
 if [ ! -f $STORAGE_ROOT/ssl/ssl_cert_sign_req.csr ]; then
 	hide_output \
 	openssl req -new -key $STORAGE_ROOT/ssl/ssl_private_key.pem -out $STORAGE_ROOT/ssl/ssl_cert_sign_req.csr \
 	  -sha256 -subj "/C=$CSR_COUNTRY/ST=/L=/O=/CN=$PRIMARY_HOSTNAME"
 fi
 
-# Generate a SSL certificate by self-signing if a SSL certificate doesn't yet exist.
+# Generate a SSL certificate by self-signing.
 if [ ! -f $STORAGE_ROOT/ssl/ssl_certificate.pem ]; then
 	hide_output \
 	openssl x509 -req -days 365 \
 	  -in $STORAGE_ROOT/ssl/ssl_cert_sign_req.csr -signkey $STORAGE_ROOT/ssl/ssl_private_key.pem -out $STORAGE_ROOT/ssl/ssl_certificate.pem
 fi
 
-# For nginx and postfix, pre-generate some better DH bits. They seem to
-# each rely on openssl's default of 1024 bits.
+# For nginx and postfix, pre-generate some Diffie-Hellman cipher bits which is
+# used when a Diffie-Hellman cipher is selected during TLS negotiation. Diffie-Hellman
+# provides Perfect Forward Security. openssl's default is 1024 bits, but we'll
+# create 2048.
 if [ ! -f $STORAGE_ROOT/ssl/dh2048.pem ]; then
 	openssl dhparam -out $STORAGE_ROOT/ssl/dh2048.pem 2048
 fi