Getting Node.js process to run on port 80 without sudo

iptables.rules

# NAT interface routing
*nat

# Setup
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [2:128]
:OUTPUT ACCEPT [2:120]
:POSTROUTING ACCEPT [2:120]

# Redirect port 80 to port 8080
-A PREROUTING -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 8080

# Redirect port 443 to port 9090
-A PREROUTING -p tcp -m tcp --dport 443 -j REDIRECT --to-ports 9090

# Save
COMMIT

# Filter interface routing
*filter

# Setup
:INPUT ACCEPT [2:128]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [246:28805]

# Allow all internal traffic
-A INPUT -i lo -j ACCEPT

# Accept already established connections
-A INPUT -i eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -i eth1 -m state --state RELATED,ESTABLISHED -j ACCEPT

# Our exposed ports
-A INPUT -p tcp -m tcp --dport 22 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 80 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 443 -j ACCEPT

# Save
COMMIT

# save to /etc/iptables.rules
# $ sudo iptables-restore < /etc/iptables.rules

iptaload

#!/bin/sh

# save this to /etc/network/if-pre-up.d/iptaload

iptables-restore < /etc/iptables.rules
exit 0

iptasave

#!/bin/sh

# save this to /etc/network/if-post-down.d/iptasave

iptables-save -c > /etc/iptables.save
if [ -f /etc/iptables.downrules ]; then
   iptables-restore < /etc/iptables.downrules
fi
exit 0

Also,

chmod +x /etc/network/if-post-down.d/iptasave
chmod +x /etc/network/if-pre-up.d/iptaload