IKEv2 is a modern protocol developed by Microsoft and Cisco which was chosen as a default VPN type in OS X 10.11 (El Capitan) and Windows since 7. It supports strong encryption, auto reconnection on network change (MOBIKE), easy configuration and more.
This manual describes minimal IKEv2 server configuration for the most simple client setup based on username/password authentication.
No 3rd party software required on client side
Only native OS tools used on client devices with Windows, MacOS, iOS.
No certificates importing on client
Simple configuration. Just type login/passowrd and server address like any other VPN connection.
IKEv2 supported platforms
|Windows||≥ 7||3DES, AES||1024|
|Windows Phone||≥ 8.1||3DES, AES||1024|
|OS X||10.11 El Capitan||DES
|768 - 8192
8 (no GUI)
|same as OS X|
|Android||StrongSwan app||AES, AES-GCM|
|Linux / FreeBSD||strongSwan ≥ 5||any||any|
X.509 Certificates intro
In order to prevent man-in-the-middle attacks IPsec IKEv2 server always authenticates itself with an X.509 certificate using a strong RSA or ECDSA signature.
After a secure communication channel has been established, clients authenticate themselves using the EAP-MSCHAPv2 protocol based on user name and password (or other authentication protocol).
This means that client needs to verify X.509 certificate authenticity using CA in system keychan. Just as for HTTPS connections in a web browser. Server certificate must be valid for successful client authentication.
There are two ways of getting server certificate:
1. Use certificate issued by CA trusted by most operating systems.
2. Issue self-signed certificate and distribute your own CA to every clients’ system.
The First way makes connection setup much easier on client side because it does not require importing any certificates in the system. This way is recommended.
Self-signed certificates are more complicated. Follow this way only if you know exactly what you need them for and how to manage your own PKI.
Issue certificate from one of Ceritifaces Authorities
Fortunately X.509 certificates that we used to deploy as SSL certificates for HTTPS web servers are also suitable for IKEv2.
You can get free certificate from Wosign, StartSSL, or LetsEncrypt, or any of your favorite CA.
The only few requirements wich certificate must comply with:
Have an Extended Key Usage (EKU) flag explicitly allowing the certificate to be used for authentication purposes. OID 184.108.40.206.220.127.116.11.1 (often called TLS server authentication) All certificated issued for web servers authenitcation have this flag.
Subdomain wich will be used as IKEv2 server adress must be in Subject Alternative Name.
Needed domain must be added as a additional domain, not as general one when issuing SSL certificate. I will use
(Optional) If possible choose SHA-256 instead of SHA-1 signature algorithm, because SHA-1 is weak and deprecated.
Selfsigned certificates requires to deploy complete PKI. Issue your own Root Certificate Authority (CA),
destribute this CA to all clients systems, issue server certificate, manage CLR (Certificate Revocation List) and OCSP.
This subject is very complicated and goes out this manual, so I won’t describe it here.
In most cases you don’t need selfsigned certificates. It is required only if you are planning to use client certificate authentication (without username/password).
If you decided to use selfsigned certificates, take a look at EasyRSA fork than allows to issue certificates suitable both for OpenVPN and IKEv2 and simplifies PKI management.
strongSwan - powerfull and open source IPsec/IKEv2 server and client solution.
You will need any Linux box with 2.6 or 3.x kernel to run strongSwan server.
Check that your favorite distro have strongSwan ≥ 5.x package in repo.
If you run Linux in virtual container, make sure that you have XEN or KVM virtualization but not OpenVZ, because OpenVZ not supporting kernel IPsec.
I recommend Linode as VPS hosting bacause they provide additional /64 IPv6 routable subnet that easely can be assigned to IPsec clients.
In this example I will use
Debian 8.2 jessie as most common distro.
Make sure that your stongSwan package not older than
Installing strongSwan and extra plugins:
apt-get install strongswan libcharon-extra-plugins
On this step you must have all necessary certificates and key files.
List of required files:
privatekey.pem — RSA private key which was used for CSR when issuing certificate. Key must be non-encrypted.
CA.crt — Root Certificate of your Certificate Authority. It can be downloaded from web or exported from system keychain.
intermediate1.crt — intermediate certificate of your Certificate Authority. If you get certificate from WoSign look at for Other Server.zip archive.
intermediate2.crt — (optional) Number of intermediate certificates may be varied, depending on your CA.
my.crt — your certificate. In the example this file will be named tunnel.zhovner.com.crt
How this chain looks from Google Chrome certificate information
Place each file to the proper path:
/etc/ipsec.d/private/privatekey.pem /etc/ipsec.d/cacerts/ca.crt /etc/ipsec.d/cacerts/intermediate1.crt /etc/ipsec.d/cacerts/intermediate2.crt /etc/ipsec.d/certs/tunnel.zhovner.com.crt
/etc/ipsec.secrets that contains users and private keys credentionals:
Restart strongSwan to read new config files:
systemctl restart strongswan
Verify that all cerifitaces configured correctly by executing
Notice that output is very long and must be readed from the top.
Full certificates chain must be presented and Entity Certificate must contain “has private key”.
List of X.509 End Entity Certificates: altNames: zhovner.com, www.zhovner.com, hub.zhovner.com, tunnel.zhovner.com, .... subject: "CN=zhovner.com" issuer: "C=CN, O=WoSign CA Limited, CN=CA CA 沃通免费SSL证书 G2" serial: 11:eb:85:14:5b:e2:56:96:0d:b4:fe:f2:4a:88:48:21 validity: not before Apr 22 17:19:27 2015, ok not after Apr 22 18:19:27 2018, ok pubkey: RSA 2048 bits, has private key keyid: 0a:c6:c8:96:59:73:2c:6c:6f:7d:03:d0:35:da:e8:49:db:86:6e:fb subjkey: f8:b0:bb:e9:9b:2c:8c:a2:90:b2:c0:77:b5:2b:c1:1f:d0:98:7e:d7 authkey: 30:da:74:86:f3:28:90:56:9e:d7:31:31:c2:bd:59:cd:93:12:39:1d List of X.509 CA Certificates: subject: "C=CN, O=WoSign CA Limited, CN=CA 沃通免费SSL证书 G2" issuer: "C=CN, O=WoSign CA Limited, CN=CA 沃通根证书" serial: 01:58:8c:3a:35:07:b3:f8:97:23:1c:76:b7:ef:85:dd validity: not before Nov 08 03:58:58 2014, ok not after Nov 08 03:58:58 2029, ok pubkey: RSA 2048 bits keyid: 7b:07:23:98:e4:9f:25:2f:19:3f:76:4d:cd:0f:70:f6:4b:fc:b0:e6 subjkey: 30:da:74:86:f3:28:90:56:9e:d7:31:31:c2:bd:59:cd:93:12:39:1d authkey: e0:4d:bf:dc:9b:41:5d:13:e8:64:f0:a7:e9:15:a4:e1:81:c1:ba:31 pathlen: 0 subject: "C=CN, O=WoSign CA Limited, CN=CA 沃通根证书" issuer: "C=IL, O=StartCom Ltd., OU=Secure Digital Certificate Signing, CN=StartCom Certification Authority" serial: 1f:ce:a7:f6:a9:7f:e9 validity: not before Sep 18 02:46:36 2006, ok not after Jan 01 02:59:59 2020, ok pubkey: RSA 4096 bits keyid: c2:06:fb:d5:3b:ba:0c:ee:f2:d2:d2:45:3d:07:52:26:3a:9f:e7:5f subjkey: e0:4d:bf:dc:9b:41:5d:13:e8:64:f0:a7:e9:15:a4:e1:81:c1:ba:31 authkey: 4e:0b:ef:1a:a4:40:5b:a5:17:69:87:30:ca:34:68:43:d0:41:ae:f2 pathlen: 2 subject: "C=IL, O=StartCom Ltd., OU=Secure Digital Certificate Signing, CN=StartCom Certification Authority" issuer: "C=IL, O=StartCom Ltd., OU=Secure Digital Certificate Signing, CN=StartCom Certification Authority" serial: 01 validity: not before Sep 17 23:46:36 2006, ok not after Sep 17 22:46:36 2036, ok pubkey: RSA 4096 bits keyid: 23:4b:71:25:56:13:e1:30:dd:e3:42:69:c9:cc:30:d4:6f:08:41:e0 subjkey: 4e:0b:ef:1a:a4:40:5b:a5:17:69:87:30:ca:34:68:43:d0:41:ae:f2
That’s all. If everything looks right try connect to server.
For debbuging connection problems run live logs stream
journalctl -f -u strongswan
For let out VPN clients into Internet you need configure NAT.
This subject is not covered in this manual.
For testing porpose (insecure):
echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
It is possible to assign native IPv6 addresses as well as IPv4 to VPN clients.
For this you will need additional IPv6 subnet routed to you machine but not assigned on server interface.
Unfortunately from lots of VPS providers that I’ve used, only Linode provide additional /64 IPv6 subnet for free.
For DigitalOcean and others providers you will need setup NDP proxy. Related thread https://lists.strongswan.org/pipermail/users/2015-July/008365.html
OS X 10.11 and iOS 9 autconfiguration profile
A configuration profile is an XML file that allows you to distribute configuration information. If you need to configure a large number of devices or to provide lots of custom email settings, VPN profiles, network settings, or certificates to a large number of devices, configuration profiles are an easy way to do it. In our case we will use VPN payload for one click configuration.
For IKEv2 VPN connections the configuration profile is the only way to set advanced options like ciphers, DH groups, PFS, rekey timeout and so on.
More about it https://developer.apple.com/library/ios/featuredarticles/iPhoneConfigurationProfileRef/Introduction/Introduction.html
Configuration profile can be created manually or via Apple Configurator 2 utility.
Syntax is same for OS X and iOS. Profile can be distributed as mail attachments or via http link.
Profile name must end with
.mobileconfig and if you plan to share it over HTTP web server should response with Content-Type
Always On Mode
In Apple terms “Always On” mode prevents user from disconnect VPN manually. This mode can be configured only on device that in supervision mode.
But you can do the same without supervision mode in more flexible way by usign rule that connects VPN automatically every time when you have internet connection. And reconnect it when connection lost. “On demand” mode can be configured only via
This mode can cause a problems when you can’t connect to the VPN server, becuase it will block internet access without VPN connection.
Always On mode unchek
On Demand options in VPN connection preferences.
The easiest way to get working profile is to edit 4 variables in this template: RemoteAddress, RemoteIdentifier, AuthName, AuthPassword. Edit the rest of template following comments.
Example profile of our VPN server
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0"> <dict> <!-- Set the name to whatever you like, it is used in the profile list on the device --> <key>PayloadDisplayName</key> <string>Super IKEv2 VPN</string> <key>PayloadIdentifier</key> <!-- This is a reverse-DNS style unique identifier used to detect duplicate profiles --> <string>com.zhovner.tunnel</string> <!-- A globally unique identifier, use uuidgen on Linux/Mac OS X to generate it --> <key>PayloadUUID</key> <string>A6F46838-77E8-49EC-8045-67C7D751063E</string> <key>PayloadType</key> <string>Configuration</string> <key>PayloadVersion</key> <integer>1</integer> <key>PayloadContent</key> <array> <!-- It is possible to add multiple VPN payloads with different identifiers/UUIDs and names --> <dict> <!-- This is an extension of the identifier given above --> <key>PayloadIdentifier</key> <string>com.zhovner.tunnel.conf</string> <!-- A globally unique identifier for this payload --> <key>PayloadUUID</key> <string>647D41C3-52E4-497D-BA25-59B9FB4043B6</string> <key>PayloadType</key> <string>com.apple.vpn.managed</string> <key>PayloadVersion</key> <integer>1</integer> <key>UserDefinedName</key> <!-- This is the name of the VPN connection as seen in the VPN application later --> <string>London VPN IKEv2</string> <key>VPNType</key> <string>IKEv2</string> <key>IKEv2</key> <dict> <!-- This is the hostname or IP address of VPN server. Chosing IP address can avoid issues with client DNS resolvers and speed up connection process. --> <key>RemoteAddress</key> <string>18.104.22.168</string> <!-- leftid in ipsec.conf --> <key>RemoteIdentifier</key> <string>tunnel.zhovner.com</string> <!-- OnDemand references: http://www.v2ex.com/t/137653 https://developer.apple.com/library/mac/featuredarticles/iPhoneConfigurationProfileRef/Introduction/Introduction.html Continue reading: https://github.com/iphoting/ovpnmcgen.rb --> <!-- AlwaysOn OnDemand Rule --> <key>OnDemandEnabled</key> <integer>1</integer> <key>OnDemandRules</key> <array> <dict> <key>Action</key> <string>Connect</string> </dict> </array> <key>DeadPeerDetectionRate</key> <string>High</string> <key>AuthenticationMethod</key> <string>Certificate</string> <key>NATKeepAliveInterval</key> <integer>30</integer> <key>NATKeepAliveOffloadEnable</key> <true/> <key>ExtendedAuthEnabled</key> <integer>1</integer> <!-- Username and password from ipsec.secrets --> <key>AuthName</key> <string>obama</string> <key>AuthPassword</key> <string>SuperPassword123</string> </dict> </dict> </array> </dict> </plist>
For testing purpose you can use my dummy profile: zhovner.com/supervpn.mobileconfig
Opening link in iOS Safari will start installation:
iOS manual configuration
OS X 10.11 manual configuration
It’s impossible to set advanced options (like ciphers, DH groups, PFS, rekey timeout) via GUI.
If you need it use configuration profile method.
Create new VPN connection in network preferences
Choose type IKEv2 and name of connection
Set server address and RemoteID (leftid in ipsec.conf)
Enter username and password from ipsec.secrets file
Connect to VPN
Windows 7/8/10 IKEv2 manual configuration
In windows you can’t define RemoteID separately from server address, so FQDN should be used.
Also keep in mind that IPv6 will not work in windows.