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IPv6 Tunnelbroker

The IPv6 Tunnelbroker is a project to provide fully routed IPv6 connectivity in situations where it is difficult for ISPs to provide it. Several projects for which we want to use this IPv6 tunnelbroker, include enviromental sensing in the Cairngorms, monitor glacier behaviour using sensor networks in Iceland and providing IPv6 for a mobile Cyber Rhino.

OpenVPN is the application of choice to build this tunnelbroker around.

Instructions for Building Certificate Authorities

These instructions are broadly based on those found at https://jamielinux.com/docs/openssl-certificate-authority/.

All commands are run from the /etc/openvpn/ipv6_tunnelbroker/ca/ directory unless otherwise stated.

Creating Root Key and Certificate

  1. Create key /etc/openvpn/ipv6_tunnelbroker/ca/private/ca.key.pem and set permissions (key size 4096 bits, passphrase encoded using AES-256 encryption):
openssl genrsa -aes256 -out private/ca.key.pem 4096
chmod 400 private/ca.key.pem
  1. Create certificate /etc/openvpn/ipv6_tunnelbroker/ca/certs/ca.cert.pem and set permissions (certificate length 20 years, using SHA-256 and configuration options in v3_ca section of /etc/openvpn/ipv6_tunnelbroker/ca/openssl.conf and default attributes but with Common Name "IPv6_Tunnelbroker_Root_CA"):
openssl req -config openssl.cnf -key private/ca.key.pem -new -x509 -days 7300 \
    -sha256 -extensions v3_ca -out certs/ca.cert.pem
chmod 444 certs/ca.cert.pem

Creating Intermediate Key and Certificate

  1. Create key /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/private/intermediate.key.pem and set permissions (key size 4096 bits, passphrase encoded using AES-256 encryption):
openssl genrsa -aes256 -out intermediate/private/intermediate.key.pem 4096
chmod 400 intermediate/private/intermediate.key.pem
  1. Create CSR /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/csr/intermediate.csr.pem using intermediate.key.pem just created and configuration from /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/openssl.cnf, (using the default attributes but with Common Name "IPv6_Tunnelbroker_Intermediate_CA"):
openssl req -config intermediate/openssl.cnf -new -sha256 \
    -key intermediate/private/intermediate.key.pem \ 
    -out intermediate/csr/intermediate.csr.pem
  1. Sign CSR intermediate.csr.pem to create /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/certs/intermediate.cert.pem (certificate length 10 years, using SHA-256 and configuration options in v3_intermediate_ca section of /etc/openvpn/ipv6_tunnelbroker/ca/openssl.conf):
openssl ca -config openssl.cnf -extensions v3_intermediate_ca -days 3650 \
    -notext -md sha256 -in intermediate/csr/intermediate.csr.pem \
    -out intermediate/certs/intermediate.cert.pem

Creating a CRL for Intermediate Certificate Authority

Create a CRL for the Intermediate certificate using the configuration options in /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/openssl.conf

openssl ca -config intermediate/openssl.cnf -gencrl \ 
    -out intermediate/crl/intermediate.crl.pem

When the CRL expires the same command can be used to replace it.

Creating OpenVPN Server Key and Certificate

This assumes using Tun rather than Tap interface, meaning only a single OpenVPN server configuration is needed.

  1. Create key /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/private/server.key.pem (key size 4096 bits, no passphrase):
openssl genrsa -out intermediate/private/server.key.pem 4096
  1. Create CSR /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/csr/server.csr.pem using server.key.pem just created and configuration from /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/openssl.cnf, (using the default attributes but with Common Name "IPv6_Tunnelbroker_Server_Cert"):
openssl req -config intermediate/openssl.cnf \
    -key intermediate/private/server.key.pem -new -sha256 \ 
    -out intermediate/csr/server.csr.pem
  1. Sign CSR server.csr.pem to create /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/certs/server.cert.pem (certificate length just over 3 years, using SHA-256 and configuration options in server_cert section of /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/openssl.conf):
openssl ca -config intermediate/openssl.cnf -extensions server_cert \
    -days 1000 -notext -md sha256 -in intermediate/csr/server.csr.pem \
    -out intermediate/certs/server.cert.pem

Creating OpenVPN Client Key and Certificate

  1. Create key /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/private/client1.key.pem (key size 4096 bits, no passphrase):
openssl genrsa -out intermediate/private/client1.key.pem 4096
  1. Create CSR /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/csr/client1.csr.pem using client1.key.pem just created and configuration from /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/openssl.cnf, (using the default attributes but with Common Name "IPv6_Tunnelbroker_Client1_Cert"):
openssl req -config intermediate/openssl.cnf \
    -key intermediate/private/client1.key.pem -new -sha256 \
    -out intermediate/csr/client1.csr.pem
  1. Sign CSR client1.csr.pem to create /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/certs/client1.cert.pem (certificate length just over 3 years, using SHA-256 and configuration options in usr_cert section of /etc/openvpn/ipv6_tunnelbroker/ca/intermediate/openssl.conf):
openssl ca -config intermediate/openssl.cnf -extensions usr_cert \
    -days 1000 -notext -md sha256 -in intermediate/csr/client1.csr.pem \ 
    -out intermediate/certs/client1.cert.pem