initial version

.gitignore

@@ -0,0 +1 @@
+vault-openvpn

example/living-example/README.md

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+# Example: living-example
+
+This example is the configuration I'm running for my personal VPN connection. Sure there are some modifications but that are customizations not relevant for this project.
+
+## How to set up the server?
+
+- Edit the `cloud-init.yml` file and set your own variables in `/etc/script_env`
+- Create a DigitalOcean droplet using this config
+- Replace the `myserver.com` part in the `client.conf` with your IP
+- Generate a server configuration and put it into `/etc/openvpn/server.conf`  
+```bash
+# vault-openvpn --auto-revoke --pki-mountpoint luzifer_io server edda.openvpn.luzifer.io
+server 10.231.0.0 255.255.255.0
+route 10.231.0.0 255.255.255.0
+[...]
+```
+- Ensure the server has finished generating `dh.pem` and reload the config: `systemctl restart openvpn`
+- Generate a client configuration and put it into Tunnelblick or any other client software you like:  
+```bash
+# vault-openvpn --auto-revoke --pki-mountpoint luzifer_io client knut-ws02.openvpn.luzifer.io
+remote myserver.com 1194 udp
+
+client
+nobind
+dev tap
+
+<ca>
+[...]
+```
+

example/living-example/client.conf

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+remote myserver.com 1194 udp
+
+client
+nobind
+dev tap
+
+<ca>
+{{ .CertAuthority }}
+</ca>
+
+<cert>
+{{ .Certificate }}
+</cert>
+
+<key>
+{{ .PrivateKey }}
+</key>
+

example/living-example/cloud-init.yml

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+#cloud-config
+
+packages:
+  - openvpn
+
+write_files:
+  - content: |
+      VAULT_ADDR="https://..."
+      PKI_PATH="${VAULT_ADDR}/v1/luzifer_io"
+    path: /etc/script_env
+    owner: root:root
+    permissions: '0600'
+
+  - content: |
+      #!/bin/bash -ex
+      source /etc/script_env
+
+      sed -i 's/#AUTOSTART="all"/AUTOSTART="all"/' /etc/default/openvpn
+      systemctl daemon-reload
+
+      openssl dhparam -out /etc/openvpn/dh2048.pem 2048
+      /usr/local/bin/refresh_crl
+    path: /tmp/setup.sh
+    owner: root:root
+    permissions: '0755'
+
+  - content: |
+      #!/bin/bash -ex
+      source /etc/script_env
+      
+      curl -sSLo /tmp/crl.pem ${PKI_PATH}/crl/pem
+      if ! ( diff -wq /etc/openvpn/crl.pem /tmp/crl.pem ); then
+        mv /tmp/crl.pem /etc/openvpn/crl.pem
+      fi
+    path: /usr/local/bin/refresh_crl
+    owner: root:root
+    permissions: '0755'
+
+  - content: |
+      */5 * * * * root /usr/local/bin/refresh_crl
+    path: /etc/cron.d/openvpn
+    owner: root:root
+
+runcmd:
+  - [ /tmp/setup.sh ]

example/living-example/server.conf

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+server 10.231.0.0 255.255.255.0
+route 10.231.0.0 255.255.255.0
+
+keepalive 5 30
+persist-key
+persist-tun
+
+proto udp
+port 1194
+dev tap
+status /var/log/openvpn-status.log
+
+client-to-client
+ifconfig-pool-persist /etc/openvpn/ipp.txt
+
+verb 3
+
+push dhcp-option DNS 8.8.8.8
+push dhcp-option DNS 8.8.4.4
+
+dh /etc/openvpn/dh2048.pem
+crl-verify /etc/openvpn/crl.pem
+
+<ca>
+{{ .CertAuthority }}
+</ca>
+
+<cert>
+{{ .Certificate }}
+</cert>
+
+<key>
+{{ .PrivateKey }}
+</key>

example/openvpn-sample/client.conf

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+##############################################
+# Sample client-side OpenVPN 2.0 config file #
+# for connecting to multi-client server.     #
+#                                            #
+# This configuration can be used by multiple #
+# clients, however each client should have   #
+# its own cert and key files.                #
+#                                            #
+# On Windows, you might want to rename this  #
+# file so it has a .ovpn extension           #
+##############################################
+
+# Specify that we are a client and that we
+# will be pulling certain config file directives
+# from the server.
+client
+
+# Use the same setting as you are using on
+# the server.
+# On most systems, the VPN will not function
+# unless you partially or fully disable
+# the firewall for the TUN/TAP interface.
+;dev tap
+dev tun
+
+# Windows needs the TAP-Windows adapter name
+# from the Network Connections panel
+# if you have more than one.  On XP SP2,
+# you may need to disable the firewall
+# for the TAP adapter.
+;dev-node MyTap
+
+# Are we connecting to a TCP or
+# UDP server?  Use the same setting as
+# on the server.
+;proto tcp
+proto udp
+
+# The hostname/IP and port of the server.
+# You can have multiple remote entries
+# to load balance between the servers.
+remote my-server-1 1194
+;remote my-server-2 1194
+
+# Choose a random host from the remote
+# list for load-balancing.  Otherwise
+# try hosts in the order specified.
+;remote-random
+
+# Keep trying indefinitely to resolve the
+# host name of the OpenVPN server.  Very useful
+# on machines which are not permanently connected
+# to the internet such as laptops.
+resolv-retry infinite
+
+# Most clients don't need to bind to
+# a specific local port number.
+nobind
+
+# Downgrade privileges after initialization (non-Windows only)
+;user nobody
+;group nobody
+
+# Try to preserve some state across restarts.
+persist-key
+persist-tun
+
+# If you are connecting through an
+# HTTP proxy to reach the actual OpenVPN
+# server, put the proxy server/IP and
+# port number here.  See the man page
+# if your proxy server requires
+# authentication.
+;http-proxy-retry # retry on connection failures
+;http-proxy [proxy server] [proxy port #]
+
+# Wireless networks often produce a lot
+# of duplicate packets.  Set this flag
+# to silence duplicate packet warnings.
+;mute-replay-warnings
+
+# SSL/TLS parms.
+# See the server config file for more
+# description.  It's best to use
+# a separate .crt/.key file pair
+# for each client.  A single ca
+# file can be used for all clients.
+<ca>
+{{ .CertAuthority }}
+</ca>
+
+<cert>
+{{ .Certificate }}
+</cert>
+
+<key>
+{{ .PrivateKey }}
+</key>
+
+# Verify server certificate by checking
+# that the certicate has the nsCertType
+# field set to "server".  This is an
+# important precaution to protect against
+# a potential attack discussed here:
+#  http://openvpn.net/howto.html#mitm
+#
+# To use this feature, you will need to generate
+# your server certificates with the nsCertType
+# field set to "server".  The build-key-server
+# script in the easy-rsa folder will do this.
+;ns-cert-type server
+
+# If a tls-auth key is used on the server
+# then every client must also have the key.
+;tls-auth ta.key 1
+
+# Select a cryptographic cipher.
+# If the cipher option is used on the server
+# then you must also specify it here.
+;cipher x
+
+# Enable compression on the VPN link.
+# Don't enable this unless it is also
+# enabled in the server config file.
+comp-lzo
+
+# Set log file verbosity.
+verb 3
+
+# Silence repeating messages
+;mute 20

example/openvpn-sample/server.conf

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+#################################################
+# Sample OpenVPN 2.0 config file for            #
+# multi-client server.                          #
+#                                               #
+# This file is for the server side              #
+# of a many-clients  one-server                 #
+# OpenVPN configuration.                        #
+#                                               #
+# OpenVPN also supports                         #
+# single-machine  single-machine                #
+# configurations (See the Examples page         #
+# on the web site for more info).               #
+#                                               #
+# This config should work on Windows            #
+# or Linux/BSD systems.  Remember on            #
+# Windows to quote pathnames and use            #
+# double backslashes, e.g.:                     #
+# "C:\\Program Files\\OpenVPN\\config\\foo.key" #
+#                                               #
+# Comments are preceded with '#' or ';'         #
+#################################################
+
+# Which local IP address should OpenVPN
+# listen on? (optional)
+;local a.b.c.d
+
+# Which TCP/UDP port should OpenVPN listen on?
+# If you want to run multiple OpenVPN instances
+# on the same machine, use a different port
+# number for each one.  You will need to
+# open up this port on your firewall.
+port 1194
+
+# TCP or UDP server?
+;proto tcp
+proto udp
+
+# "dev tun" will create a routed IP tunnel,
+# "dev tap" will create an ethernet tunnel.
+# Use "dev tap0" if you are ethernet bridging
+# and have precreated a tap0 virtual interface
+# and bridged it with your ethernet interface.
+# If you want to control access policies
+# over the VPN, you must create firewall
+# rules for the the TUN/TAP interface.
+# On non-Windows systems, you can give
+# an explicit unit number, such as tun0.
+# On Windows, use "dev-node" for this.
+# On most systems, the VPN will not function
+# unless you partially or fully disable
+# the firewall for the TUN/TAP interface.
+;dev tap
+dev tun
+
+# Windows needs the TAP-Windows adapter name
+# from the Network Connections panel if you
+# have more than one.  On XP SP2 or higher,
+# you may need to selectively disable the
+# Windows firewall for the TAP adapter.
+# Non-Windows systems usually don't need this.
+;dev-node MyTap
+
+# SSL/TLS root certificate (ca), certificate
+# (cert), and private key (key).  Each client
+# and the server must have their own cert and
+# key file.  The server and all clients will
+# use the same ca file.
+#
+# See the "easy-rsa" directory for a series
+# of scripts for generating RSA certificates
+# and private keys.  Remember to use
+# a unique Common Name for the server
+# and each of the client certificates.
+#
+# Any X509 key management system can be used.
+# OpenVPN can also use a PKCS #12 formatted key file
+# (see "pkcs12" directive in man page).
+<ca>
+{{ .CertAuthority }}
+</ca>
+
+<cert>
+{{ .Certificate }}
+</cert>
+
+<key>
+{{ .PrivateKey }}
+</key>
+
+# Diffie hellman parameters.
+# Generate your own with:
+#   openssl dhparam -out dh1024.pem 1024
+# Substitute 2048 for 1024 if you are using
+# 2048 bit keys. 
+dh dh1024.pem
+
+# Configure server mode and supply a VPN subnet
+# for OpenVPN to draw client addresses from.
+# The server will take 10.8.0.1 for itself,
+# the rest will be made available to clients.
+# Each client will be able to reach the server
+# on 10.8.0.1. Comment this line out if you are
+# ethernet bridging. See the man page for more info.
+server 10.8.0.0 255.255.255.0
+
+# Maintain a record of client  virtual IP address
+# associations in this file.  If OpenVPN goes down or
+# is restarted, reconnecting clients can be assigned
+# the same virtual IP address from the pool that was
+# previously assigned.
+ifconfig-pool-persist ipp.txt
+
+# Configure server mode for ethernet bridging.
+# You must first use your OS's bridging capability
+# to bridge the TAP interface with the ethernet
+# NIC interface.  Then you must manually set the
+# IP/netmask on the bridge interface, here we
+# assume 10.8.0.4/255.255.255.0.  Finally we
+# must set aside an IP range in this subnet
+# (start=10.8.0.50 end=10.8.0.100) to allocate
+# to connecting clients.  Leave this line commented
+# out unless you are ethernet bridging.
+;server-bridge 10.8.0.4 255.255.255.0 10.8.0.50 10.8.0.100
+
+# Push routes to the client to allow it
+# to reach other private subnets behind
+# the server.  Remember that these
+# private subnets will also need
+# to know to route the OpenVPN client
+# address pool (10.8.0.0/255.255.255.0)
+# back to the OpenVPN server.
+;push "route 192.168.10.0 255.255.255.0"
+;push "route 192.168.20.0 255.255.255.0"
+
+# To assign specific IP addresses to specific
+# clients or if a connecting client has a private
+# subnet behind it that should also have VPN access,
+# use the subdirectory "ccd" for client-specific
+# configuration files (see man page for more info).
+
+# EXAMPLE: Suppose the client
+# having the certificate common name "Thelonious"
+# also has a small subnet behind his connecting
+# machine, such as 192.168.40.128/255.255.255.248.
+# First, uncomment out these lines:
+;client-config-dir ccd
+;route 192.168.40.128 255.255.255.248
+# Then create a file ccd/Thelonious with this line:
+#   iroute 192.168.40.128 255.255.255.248
+# This will allow Thelonious' private subnet to
+# access the VPN.  This example will only work
+# if you are routing, not bridging, i.e. you are
+# using "dev tun" and "server" directives.
+
+# EXAMPLE: Suppose you want to give
+# Thelonious a fixed VPN IP address of 10.9.0.1.
+# First uncomment out these lines:
+;client-config-dir ccd
+;route 10.9.0.0 255.255.255.252
+# Then add this line to ccd/Thelonious:
+#   ifconfig-push 10.9.0.1 10.9.0.2
+
+# Suppose that you want to enable different
+# firewall access policies for different groups
+# of clients.  There are two methods:
+# (1) Run multiple OpenVPN daemons, one for each
+#     group, and firewall the TUN/TAP interface
+#     for each group/daemon appropriately.
+# (2) (Advanced) Create a script to dynamically
+#     modify the firewall in response to access
+#     from different clients.  See man
+#     page for more info on learn-address script.
+;learn-address ./script
+
+# If enabled, this directive will configure
+# all clients to redirect their default
+# network gateway through the VPN, causing
+# all IP traffic such as web browsing and
+# and DNS lookups to go through the VPN
+# (The OpenVPN server machine may need to NAT
+# the TUN/TAP interface to the internet in
+# order for this to work properly).
+# CAVEAT: May break client's network config if
+# client's local DHCP server packets get routed
+# through the tunnel.  Solution: make sure
+# client's local DHCP server is reachable via
+# a more specific route than the default route
+# of 0.0.0.0/0.0.0.0.
+;push "redirect-gateway"
+
+# Certain Windows-specific network settings
+# can be pushed to clients, such as DNS
+# or WINS server addresses.  CAVEAT:
+# http://openvpn.net/faq.html#dhcpcaveats
+;push "dhcp-option DNS 10.8.0.1"
+;push "dhcp-option WINS 10.8.0.1"
+
+# Uncomment this directive to allow different
+# clients to be able to "see" each other.
+# By default, clients will only see the server.
+# To force clients to only see the server, you
+# will also need to appropriately firewall the
+# server's TUN/TAP interface.
+;client-to-client
+
+# Uncomment this directive if multiple clients
+# might connect with the same certificate/key
+# files or common names.  This is recommended
+# only for testing purposes.  For production use,
+# each client should have its own certificate/key
+# pair.
+#
+# IF YOU HAVE NOT GENERATED INDIVIDUAL
+# CERTIFICATE/KEY PAIRS FOR EACH CLIENT,
+# EACH HAVING ITS OWN UNIQUE "COMMON NAME",
+# UNCOMMENT THIS LINE OUT.
+;duplicate-cn
+
+# The keepalive directive causes ping-like
+# messages to be sent back and forth over
+# the link so that each side knows when
+# the other side has gone down.
+# Ping every 10 seconds, assume that remote
+# peer is down if no ping received during
+# a 120 second time period.
+keepalive 10 120
+
+# For extra security beyond that provided
+# by SSL/TLS, create an "HMAC firewall"
+# to help block DoS attacks and UDP port flooding.
+#
+# Generate with:
+#   openvpn --genkey --secret ta.key
+#
+# The server and each client must have
+# a copy of this key.
+# The second parameter should be '0'
+# on the server and '1' on the clients.
+;tls-auth ta.key 0 # This file is secret
+
+# Select a cryptographic cipher.
+# This config item must be copied to
+# the client config file as well.
+;cipher BF-CBC        # Blowfish (default)
+;cipher AES-128-CBC   # AES
+;cipher DES-EDE3-CBC  # Triple-DES
+
+# Enable compression on the VPN link.
+# If you enable it here, you must also
+# enable it in the client config file.
+comp-lzo
+
+# The maximum number of concurrently connected
+# clients we want to allow.
+;max-clients 100
+
+# It's a good idea to reduce the OpenVPN
+# daemon's privileges after initialization.
+#
+# You can uncomment this out on
+# non-Windows systems.
+;user nobody
+;group nobody
+
+# The persist options will try to avoid
+# accessing certain resources on restart
+# that may no longer be accessible because
+# of the privilege downgrade.
+persist-key
+persist-tun
+
+# Output a short status file showing
+# current connections, truncated
+# and rewritten every minute.
+status openvpn-status.log
+
+# By default, log messages will go to the syslog (or
+# on Windows, if running as a service, they will go to
+# the "\Program Files\OpenVPN\log" directory).
+# Use log or log-append to override this default.
+# "log" will truncate the log file on OpenVPN startup,
+# while "log-append" will append to it.  Use one
+# or the other (but not both).
+;log         openvpn.log
+;log-append  openvpn.log
+
+# Set the appropriate level of log
+# file verbosity.
+#
+# 0 is silent, except for fatal errors
+# 4 is reasonable for general usage
+# 5 and 6 can help to debug connection problems
+# 9 is extremely verbose
+verb 3
+
+# Silence repeating messages.  At most 20
+# sequential messages of the same message
+# category will be output to the log.
+;mute 20

main.go

@@ -0,0 +1,234 @@
+package main
+
+import (
+	"crypto/x509"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"strings"
+	"text/template"
+	"time"
+
+	"github.com/Luzifer/go_helpers/str"
+	"github.com/Luzifer/rconfig"
+	"github.com/hashicorp/vault/api"
+	homedir "github.com/mitchellh/go-homedir"
+)
+
+const (
+	actionRevoke           = "revoke"
+	actionMakeClientConfig = "client"
+	actionMakeServerConfig = "server"
+)
+
+var (
+	cfg = struct {
+		VaultAddress string `flag:"vault-addr" env:"VAULT_ADDR" default:"https://127.0.0.1:8200" description:"Vault API address"`
+		VaultToken   string `flag:"vault-token" env:"VAULT_TOKEN" vardefault:"vault-token" description:"Specify a token to use instead of app-id auth"`
+
+		PKIMountPoint string `flag:"pki-mountpoint" default:"/pki" description:"Path the PKI provider is mounted to"`
+		PKIRole       string `flag:"pki-role" default:"openvpn" description:"Role defined in the PKI usable by the token and able to write the specified FQDN"`
+
+		AutoRevoke bool          `flag:"auto-revoke" default:"false" description:"Automatically revoke older certificates for this FQDN"`
+		CertTTL    time.Duration `flag:"ttl" default:"8760h" description:"Set the TTL for this certificate"`
+
+		VersionAndExit bool `flag:"version" default:"false" description:"Prints current version and exits"`
+	}{}
+
+	version = "dev"
+
+	client *api.Client
+)
+
+type templateVars struct {
+	CertAuthority string
+	Certificate   string
+	PrivateKey    string
+}
+
+func vaultTokenFromDisk() string {
+	vf, err := homedir.Expand("~/.vault-token")
+	if err != nil {
+		return ""
+	}
+
+	data, err := ioutil.ReadFile(vf)
+	if err != nil {
+		return ""
+	}
+
+	return string(data)
+}
+
+func init() {
+	rconfig.SetVariableDefaults(map[string]string{
+		"vault-token": vaultTokenFromDisk(),
+	})
+
+	if err := rconfig.Parse(&cfg); err != nil {
+		log.Fatalf("Unable to parse commandline options: %s", err)
+	}
+
+	if cfg.VersionAndExit {
+		fmt.Printf("vault-openvpn %s\n", version)
+		os.Exit(0)
+	}
+
+	if cfg.VaultToken == "" {
+		log.Fatalf("[ERR] You need to set vault-token")
+	}
+}
+
+func main() {
+	if len(rconfig.Args()) != 3 {
+		fmt.Println("Usage: vault-openvpn [options] <action> <FQDN>")
+		fmt.Println("         actions: client / server / revoke")
+		os.Exit(1)
+	}
+
+	action := rconfig.Args()[1]
+	fqdn := rconfig.Args()[2]
+
+	if !str.StringInSlice(action, []string{actionRevoke, actionMakeClientConfig, actionMakeServerConfig}) {
+		log.Fatalf("Unknown action: %s", action)
+	}
+
+	var err error
+	client, err = api.NewClient(&api.Config{
+		Address: cfg.VaultAddress,
+	})
+
+	if err != nil {
+		log.Fatalf("Could not create Vault client: %s", err)
+	}
+
+	client.SetToken(cfg.VaultToken)
+
+	if cfg.AutoRevoke || action == actionRevoke {
+		if err := revokeOlderCertificate(fqdn); err != nil {
+			log.Fatalf("Could not revoke certificate: %s", err)
+		}
+	}
+
+	if action != actionMakeClientConfig && action != actionMakeServerConfig {
+		return
+	}
+
+	tplName := "client.conf"
+	if action == actionMakeServerConfig {
+		tplName = "server.conf"
+	}
+
+	caCert, err := getCACert()
+	if err != nil {
+		log.Fatalf("Could not load CA certificate: %s", err)
+	}
+
+	tplv, err := generateCertificate(fqdn)
+	if err != nil {
+		log.Fatalf("Could not generate new certificate: %s", err)
+	}
+
+	tplv.CertAuthority = caCert
+
+	if err := renderTemplate(tplName, tplv); err != nil {
+		log.Fatalf("Could not render configuration: %s", err)
+	}
+}
+
+func renderTemplate(tplName string, tplv *templateVars) error {
+	raw, err := ioutil.ReadFile(tplName)
+	if err != nil {
+		return err
+	}
+
+	tpl, err := template.New("tpl").Parse(string(raw))
+	if err != nil {
+		return err
+	}
+
+	return tpl.Execute(os.Stdout, tplv)
+}
+
+func revokeOlderCertificate(fqdn string) error {
+	path := strings.Join([]string{strings.Trim(cfg.PKIMountPoint, "/"), "certs"}, "/")
+	secret, err := client.Logical().List(path)
+	if err != nil {
+		return err
+	}
+
+	if secret.Data == nil {
+		return errors.New("Got no data from backend")
+	}
+
+	for _, serial := range secret.Data["keys"].([]interface{}) {
+		path := strings.Join([]string{strings.Trim(cfg.PKIMountPoint, "/"), "cert", serial.(string)}, "/")
+		cs, err := client.Logical().Read(path)
+		if err != nil {
+			errors.New("Unable to read certificate: " + err.Error())
+		}
+
+		cn, err := commonNameFromCertificate(cs.Data["certificate"].(string))
+		if err != nil {
+			return err
+		}
+
+		log.Printf("Found certificate %s with CN %s", serial, cn)
+
+		if cn == fqdn {
+			path := strings.Join([]string{strings.Trim(cfg.PKIMountPoint, "/"), "revoke"}, "/")
+			if _, err := client.Logical().Write(path, map[string]interface{}{
+				"serial_number": serial.(string),
+			}); err != nil {
+				return errors.New("Revoke of serial " + serial.(string) + " failed: " + err.Error())
+			}
+			log.Printf("Revoked certificate %s", serial)
+		}
+	}
+
+	return nil
+}
+
+func commonNameFromCertificate(pemString string) (string, error) {
+	data, _ := pem.Decode([]byte(pemString))
+	cert, err := x509.ParseCertificate(data.Bytes)
+	if err != nil {
+		return "", err
+	}
+
+	return cert.Subject.CommonName, nil
+}
+
+func getCACert() (string, error) {
+	path := strings.Join([]string{strings.Trim(cfg.PKIMountPoint, "/"), "cert", "ca"}, "/")
+	cs, err := client.Logical().Read(path)
+	if err != nil {
+		errors.New("Unable to read certificate: " + err.Error())
+	}
+
+	return cs.Data["certificate"].(string), nil
+}
+
+func generateCertificate(fqdn string) (*templateVars, error) {
+	path := strings.Join([]string{strings.Trim(cfg.PKIMountPoint, "/"), "issue", cfg.PKIRole}, "/")
+	secret, err := client.Logical().Write(path, map[string]interface{}{
+		"common_name": fqdn,
+		"ttl":         cfg.CertTTL.String(),
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	if secret.Data == nil {
+		return nil, errors.New("Got no data from backend")
+	}
+
+	return &templateVars{
+		Certificate: secret.Data["certificate"].(string),
+		PrivateKey:  secret.Data["private_key"].(string),
+	}, nil
+}