OpenVPN

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OpenVPN
WhitespaceLogo.gif
What:
VPN server
Participants:
Jaroslov, Abe, Hans
Locations:
Whitespace
Cornify

Setup

An OpenVPN server on members.0x20.be, connected to Belnet, hosted by IBBT. There is also a p2p tunnel to the space to provide connectivity to the 0x20 internal network. Authentication is done with SSL client certificates based on a 0x20 CA. All client certificates signed by the 0x20 CA and with an 'OU=members' are allowed to connect. Future access can be denied by revoking the client certificate and updating the CRL (Certificate Revocation List).

See below for the steps to connect to the VPN server. Further below is the documentation of the server configurations.

Client

Create a new key

Linux/windows:

   $ openssl genrsa -aes256 -out 0x20-vpn-your_name_here.key 2048

Create a Certificate signing request

   $ openssl req -new -key 0x20-vpn-your_name_here.key -out 0x20-vpn-your_name_here.csr
           countryName               = BE
           stateOrProvinceName       = Ghent
           organizationName          = 0x20
           organizationalUnitName    = members
           commonName                = your_name_here

Get your certificate signed

Mail your CSR(certificate signing request) to someone who has access to the 0x20 CA. Best is being physically present in the space.

Sign cert:

   $ openssl ca -in ../0x20-vpn-your_name_here.csr -cert ca-0x20-cert.pem -keyfile private/ca-0x20-key.pem -out 0x20-vpn-your_name_here.cert -config ./openssl.cnf

Client config Linux

  • apt-get install openvpn
  • create following config file: /etc/openvpn/0x20-vpn.conf and change values in bold
   client
   remote members.0x20.be 1194
   proto udp 
   dev tun  
   
   resolv-retry infinite
   nobind
   
   user nobody
   group nogroup
       
   persist-key
   persist-tun
   
   ca certs/ca-0x20-cert.pem
   cert certs/0x20-vpn-<name>.cert
   key certs/0x20-vpn-<name>.key
   
   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
  
   cipher AES-256-CBC
   comp-lzo
   
   verb 3
   mute 20

Client config Wintendo

  • Get openvpn for windows here version OpenVPN 2.2.1 or higher
  • Save this content to this filename C:\Program Files\OpenVPN\config\Openvpn_0x20.ovpn
client
remote members.0x20.be 1194
proto udp 
dev tun  

resolv-retry infinite
nobind

user nobody
group nogroup
 
persist-key
persist-tun

#change the paths as needed.
ca "C:\\Program Files\\OpenVPN\\easy-rsa\\keys\\ca-0x20-cert.pem"
cert "C:\\Program Files\\OpenVPN\\easy-rsa\\keys\\0x20-vpn-your_name_here.cert"
key "C:\\Program Files\\OpenVPN\\easy-rsa\\keys\\0x20-vpn-your_name_here.key"


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
  
cipher AES-256-CBC
comp-lzo

verb 3
mute 20
  • open cmd with administrator privileges (start menu -> cmd -> run as admin)
  • cd Program Files\OpenVPN\easy-rsa
  • give command init-config.bat
  • Save following content as C:\Progra~1\OpenVPN\easy-rsa\openssl.cnf
#
# OpenSSL example configuration file.
# This is mostly being used for generation of certificate requests.
#

# This definition stops the following lines choking if HOME isn't
# defined.
HOME			= .
RANDFILE		= $ENV::HOME/.rnd

# Extra OBJECT IDENTIFIER info:
#oid_file		= $ENV::HOME/.oid
oid_section		= new_oids

# To use this configuration file with the "-extfile" option of the
# "openssl x509" utility, name here the section containing the
# X.509v3 extensions to use:
# extensions		= 
# (Alternatively, use a configuration file that has only
# X.509v3 extensions in its main [= default] section.)

[ new_oids ]

# We can add new OIDs in here for use by 'ca' and 'req'.
# Add a simple OID like this:
# testoid1=1.2.3.4
# Or use config file substitution like this:
# testoid2=${testoid1}.5.6

####################################################################
[ ca ]
default_ca	= CA_default		# The default ca section

####################################################################
[ CA_default ]

dir		= C:/user/local/ssl		# Where everything is kept
certs		= $dir			# Where the issued certs are kept
crl_dir		= $dir			# Where the issued crl are kept
database	= $dir/index.txt	# database index file.
new_certs_dir	= $dir			# default place for new certs.

certificate	= $dir/ca.crt	 	# The CA certificate
serial		= $dir/serial 		# The current serial number
crl		= $dir/crl.pem 		# The current CRL
private_key	= $dir/ca.key	 	# The private key
RANDFILE	= $dir/.rand		# private random number file

x509_extensions	= usr_cert		# The extentions to add to the cert

# Extensions to add to a CRL. Note: Netscape communicator chokes on V2 CRLs
# so this is commented out by default to leave a V1 CRL.
# crl_extensions	= crl_ext

default_days	= 3650			# how long to certify for
default_crl_days= 30			# how long before next CRL
default_md	= md5			# which md to use.
preserve	= no			# keep passed DN ordering

# A few difference way of specifying how similar the request should look
# For type CA, the listed attributes must be the same, and the optional
# and supplied fields are just that :-)
policy		= policy_match

# For the CA policy
[ policy_match ]
countryName		= match
stateOrProvinceName	= match
organizationName	= match
organizationalUnitName	= optional
commonName		= supplied
emailAddress		= optional

# For the 'anything' policy
# At this point in time, you must list all acceptable 'object'
# types.
[ policy_anything ]
countryName		= optional
stateOrProvinceName	= optional
localityName		= optional
organizationName	= optional
organizationalUnitName	= optional
commonName		= supplied
emailAddress		= optional

####################################################################
[ req ]
default_bits		= 2048
default_keyfile 	= privkey.pem
distinguished_name	= req_distinguished_name
attributes		= req_attributes
x509_extensions	= v3_ca	# The extentions to add to the self signed cert

# Passwords for private keys if not present they will be prompted for
# input_password = secret
# output_password = secret

# This sets a mask for permitted string types. There are several options. 
# default: PrintableString, T61String, BMPString.
# pkix	 : PrintableString, BMPString.
# utf8only: only UTF8Strings.
# nombstr : PrintableString, T61String (no BMPStrings or UTF8Strings).
# MASK:XXXX a literal mask value.
# WARNING: current versions of Netscape crash on BMPStrings or UTF8Strings
# so use this option with caution!
string_mask = nombstr

# req_extensions = v3_req # The extensions to add to a certificate request

[ req_distinguished_name ]
countryName			= Country Name (2 letter code)
countryName_default		= BE
countryName_min			= 2
countryName_max			= 2

stateOrProvinceName		= State or Province Name (full name)
stateOrProvinceName_default	= Ghent

localityName			= Locality Name (eg, city)
localityName_default		= Whitespace

0.organizationName		= Organization Name (eg, company)
0.organizationName_default	= 0x20

# we can do this but it is not needed normally :-)
#1.organizationName		= Second Organization Name (eg, company)
#1.organizationName_default	= World Wide Web Pty Ltd

organizationalUnitName		= Organizational Unit Name (eg, section)
organizationalUnitName_default	= members

commonName			= Common Name (eg, your name or your server\'s hostname)
commonName_max			= 64

emailAddress			= Email Address
#emailAddress_default		= $ENV::KEY_EMAIL
emailAddress_max		= 40

# SET-ex3			= SET extension number 3

[ req_attributes ]
challengePassword		= A challenge password
challengePassword_min		= 4
challengePassword_max		= 20

unstructuredName		= An optional company name

[ usr_cert ]

# These extensions are added when 'ca' signs a request.

# This goes against PKIX guidelines but some CAs do it and some software
# requires this to avoid interpreting an end user certificate as a CA.

basicConstraints=CA:FALSE

# Here are some examples of the usage of nsCertType. If it is omitted
# the certificate can be used for anything *except* object signing.

# This is OK for an SSL server.
# nsCertType			= server

# For an object signing certificate this would be used.
# nsCertType = objsign

# For normal client use this is typical
# nsCertType = client, email

# and for everything including object signing:
# nsCertType = client, email, objsign

# This is typical in keyUsage for a client certificate.
# keyUsage = nonRepudiation, digitalSignature, keyEncipherment

# This will be displayed in Netscape's comment listbox.
nsComment			= "OpenSSL Generated Certificate"

# PKIX recommendations harmless if included in all certificates.
subjectKeyIdentifier=hash
authorityKeyIdentifier=keyid,issuer:always

# This stuff is for subjectAltName and issuerAltname.
# Import the email address.
# subjectAltName=email:copy

# Copy subject details
# issuerAltName=issuer:copy

#nsCaRevocationUrl		= http://www.domain.dom/ca-crl.pem
#nsBaseUrl
#nsRevocationUrl
#nsRenewalUrl
#nsCaPolicyUrl
#nsSslServerName

[ server ]

# JY ADDED -- Make a cert with nsCertType set to "server"
basicConstraints=CA:FALSE
nsCertType			= server
nsComment			= "OpenSSL Generated Server Certificate"
subjectKeyIdentifier=hash
authorityKeyIdentifier=keyid,issuer:always

[ v3_req ]

# Extensions to add to a certificate request

basicConstraints = CA:FALSE
keyUsage = nonRepudiation, digitalSignature, keyEncipherment

[ v3_ca ]


# Extensions for a typical CA


# PKIX recommendation.

subjectKeyIdentifier=hash

authorityKeyIdentifier=keyid:always,issuer:always

# This is what PKIX recommends but some broken software chokes on critical
# extensions.
#basicConstraints = critical,CA:true
# So we do this instead.
basicConstraints = CA:true

# Key usage: this is typical for a CA certificate. However since it will
# prevent it being used as an test self-signed certificate it is best
# left out by default.
# keyUsage = cRLSign, keyCertSign

# Some might want this also
# nsCertType = sslCA, emailCA

# Include email address in subject alt name: another PKIX recommendation
# subjectAltName=email:copy
# Copy issuer details
# issuerAltName=issuer:copy

# DER hex encoding of an extension: beware experts only!
# obj=DER:02:03
# Where 'obj' is a standard or added object
# You can even override a supported extension:
# basicConstraints= critical, DER:30:03:01:01:FF

[ crl_ext ]

# CRL extensions.
# Only issuerAltName and authorityKeyIdentifier make any sense in a CRL.

# issuerAltName=issuer:copy
authorityKeyIdentifier=keyid:always,issuer:always
  • Navigate to a dir where you have write permissions
  • command : openssl genrsa -aes256 -out 0x20-vpn-your_name_here.key 2048
  • command : openssl req -new -key 0x20-vpn-your_name_here.key -out 0x20-vpn-your_name_here.csr -config C:\Progra~1\OpenVPN\easy-rsa\openssl.cnf
  • Answer the questions in accordance
    • countryName = BE
    • stateOrProvinceName = Ghent
    • organizationName = 0x20
    • organizationalUnitName = members
    • commonName = your_name_here
  • Send the csr to jaroslav
  • save the three files at the right place
   ca "C:\\Program Files\\OpenVPN\\easy-rsa\\keys\\ca-0x20-cert.pem"
   cert "C:\\Program Files\\OpenVPN\\easy-rsa\\keys\\0x20-vpn-your_name_here.cert"
   key "C:\\Program Files\\OpenVPN\\easy-rsa\\keys\\0x20-vpn-your_name_here.key"
  • start openvpn as admin... click on icon in taskbar ...

Important: When executing openvpn use administrator permissions (run as administrator). Selecte openvpn_0x20, select connect

Client Config Mac

  • You're on your own buddy.

Server members.0x20.be

  • server mode
  • uses 0x20 CA
  • only accepts client certificates with OU=members
  • uses crl
  • range 172.20.200.0/24

OpenVPN config

  • /etc/openvpn/public.conf :
mode server
lport 1194
proto udp 
dev-type tun 
dev vpn-public

ca certs/ca-0x20-cert.pem
crl-verify certs/ca-0x20-crl.pem
cert certs/0x20-members-vpn.cert
key certs/0x20-members-vpn.key # This file should be kept secret
dh certs/dh2048.pem

tls-verify "./certs/verify-ou members"

server 172.20.200.0 255.255.255.0
ifconfig-pool-persist ipp.txt
push "route 172.22.32.0 255.255.255.0"
push "redirect-gateway def1"

comp-lzo
cipher AES-256-CBC

user nobody
group nogroup

status /var/log/openvpn-status-public.log
log-append /var/log/openvpn-public.log
verb 2
mute 20
  • /etc/openvpn/certs/verify-ou :
#!/usr/bin/perl

# verify-cn -- a sample OpenVPN tls-verify script
#
# Return 0 if cn matches the common name component of
# X509_NAME_oneline, 1 otherwise.
#
# For example in OpenVPN, you could use the directive:
#
#   tls-verify "./verify-cn Test-Client"
#
# This would cause the connection to be dropped unless
# the client common name is "Test-Client"

die "usage: verify-cn cn certificate_depth X509_NAME_oneline" if (@ARGV != 3); 

# Parse out arguments:
#   ou    -- The common name which the client is required to have,
#            taken from the argument to the tls-verify directive
#            in the OpenVPN config file.
#   depth -- The current certificate chain depth.  In a typical
#            bi-level chain, the root certificate will be at level
#            1 and the client certificate will be at level 0.
#            This script will be called separately for each level.
#   x509  -- the X509 subject string as extracted by OpenVPN from
#            the client's provided certificate.
($ou, $depth, $x509) = @ARGV;

if ($depth == 0) {
    # If depth is zero, we know that this is the final
    # certificate in the chain (i.e. the client certificate),
    # and the one we are interested in examining.
    # If so, parse out the common name substring in
    # the X509 subject string.

    if ($x509 =~ /\/OU=([^\/]+)/) {
    # Accept the connection if the X509 common name
    # string matches the passed cn argument.
    if ($ou eq $1) {
        exit 0;
    }   
    }   

    # Authentication failed -- Either we could not parse
    # the X509 subject string, or the common name in the
    # subject string didn't match the passed cn argument.
    exit 1;
}
# If depth is nonzero, tell OpenVPN to continue processing
# the certificate chain.
exit 0;

Network config

  • Enable IP forwarding:
# sysctl -w net.ipv4.ip_forward=1
  • NAT:
# iptables -t nat -A POSTROUTING -s 172.20.200.0/24 -o eth0 -j MASQUERADE
  • Add route to make 0x20 network (172.22.32.0/24) available over the vpn tunnel:
# route add -net 172.22.32.0 netmask 255.255.255.0 dev vpn-0x20

Setup routing on 0x20-router (soekris):

# route add -net 172.20.200.0 netmask 255.255.255.0 dev vpn-members

Server 0x20 <-> IBBT

A P2P tunnel between 0x20 and IBBT.

  • 0x20/soekris config, /etc/openvpn/members.conf :
mode p2p                                       # Peer-to-peer-Mode
remote members.0x20.be                         # Peer-Address, (Dyn)DNS if it's
lport 40002                                    # local port
rport 443                                      # remote port
proto tcp-client                               # ...via TCP, use server mode
dev-type tun
dev vpn-members                                # interfacename, just individual
#tun-ipv6                                      # we want to use ipv6
comp-lzo                                       # compression
#cd /usr/local/etc/openvpn                     # here lays the key
secret members.key                             # the filename of the key
user nobody                                    # username under which openvpn
group nogroup                                  # ...group
persist-key                                    # on interruption, please keep
persist-tun                                    # on interruption, please keep
status /var/log/openvpn-status-members.log
log-append /var/log/openvpn-members.log
verb 2                                        # Verbose!
ifconfig 172.22.32.5 172.20.201.1             # addressing: 'ifconfig localip remoteip'
  • members.0x20.be config, /etc/openvpn/0x20.conf :
mode p2p                                       # Peer-to-peer-Mode
remote 83.101.72.80                            # Peer-Address, (Dyn)DNS if it's
lport 443                                      # local port
rport 40002                                    # remote por 
proto tcp-server                               # ...via TCP, use server mode
dev-type tun 
dev vpn-0x20                                   # interfacename, just individual
#tun-ipv6                                      # we want to use ipv6
comp-lzo                                       # compression
#cd /usr/local/etc/openvpn                     # here lays the key 
secret 0x20.key                                # the filename of the key
user nobody                                    # username under which openvpn
group nogroup                                  # ...group
persist-key                                    # on interruption, please keep
persist-tun                                    # on interruption, please keep
status /var/log/openvpn-status-0x20.log
log-append /var/log/openvpn-0x20.log
verb 2                                         # Verbose!
ifconfig 172.20.201.1 172.22.32.5              # addressing: 'ifconfig localip remoteip'