strongSwan + xl2tpd VPN server: how to configure several config files?

Question

I set up my VPN server with strongSwan and xl2tpd on Ubuntu server 16.04. After configuring, I tried to connect from a iPad, but got the errors as follows:

Mar 26 02:22:13 myname-ubuntu-server charon: 01[NET] received packet: from 61.205.5.249[44919] to 192.168.193.3[500] (788 bytes)
Mar 26 02:22:13 myname-ubuntu-server charon: 01[ENC] parsed ID_PROT request 0 [ SA V V V V V V V V V V V V ]
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received NAT-T (RFC 3947) vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-08 vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-07 vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-06 vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-05 vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-04 vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-03 vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-02 vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received draft-ietf-ipsec-nat-t-ike-02\n vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received FRAGMENTATION vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] received DPD vendor ID
Mar 26 02:22:13 myname-ubuntu-server charon: 01[IKE] 61.205.5.249 is initiating a Main Mode IKE_SA
Mar 26 02:22:13 myname-ubuntu-server charon: 01[ENC] generating ID_PROT response 0 [ SA V V V ]
Mar 26 02:22:13 myname-ubuntu-server charon: 01[NET] sending packet: from 192.168.193.3[500] to 61.205.5.249[44919] (136 bytes)
Mar 26 02:22:13 myname-ubuntu-server charon: 10[NET] received packet: from 61.205.5.249[44919] to 192.168.193.3[500] (380 bytes)
Mar 26 02:22:13 myname-ubuntu-server charon: 10[ENC] parsed ID_PROT request 0 [ KE No NAT-D NAT-D ]
Mar 26 02:22:13 myname-ubuntu-server charon: 10[IKE] local host is behind NAT, sending keep alives
Mar 26 02:22:13 myname-ubuntu-server charon: 10[IKE] remote host is behind NAT
Mar 26 02:22:13 myname-ubuntu-server charon: 10[ENC] generating ID_PROT response 0 [ KE No NAT-D NAT-D ]
Mar 26 02:22:13 myname-ubuntu-server charon: 10[NET] sending packet: from 192.168.193.3[500] to 61.205.5.249[44919] (396 bytes)
Mar 26 02:22:13 myname-ubuntu-server charon: 06[NET] received packet: from 61.205.5.249[4500] to 192.168.193.3[4500] (108 bytes)
Mar 26 02:22:13 myname-ubuntu-server charon: 06[ENC] parsed ID_PROT request 0 [ ID HASH N(INITIAL_CONTACT) ]
Mar 26 02:22:13 myname-ubuntu-server charon: 06[CFG] looking for pre-shared key peer configs matching 192.168.193.3...61.205.5.249[100.75.130.131]
Mar 26 02:22:13 myname-ubuntu-server charon: 06[IKE] found 1 matching config, but none allows pre-shared key authentication using Main Mode
Mar 26 02:22:13 myname-ubuntu-server charon: 06[ENC] generating INFORMATIONAL_V1 request 2960834334 [ HASH N(AUTH_FAILED) ]
Mar 26 02:22:13 myname-ubuntu-server charon: 06[NET] sending packet: from 192.168.193.3[4500] to 61.205.5.249[4500] (108 bytes)

I thought the critical point of the error is "found 1 matching config, but none allows pre-shared key authentication using Main Mode". Do anyone know how to resolve this error?

I found a answer for this problem that suggested to add "aggressiveness=yes" to /etc/ipsec.conf and tried but didn't work... (Maybe I add the line "aggressiveness=yes" in a wrong position... I'm a beginner in Linux...)

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I set up config files by following this site: http://qiita.com/namoshika/items/30c348b56474d422ef64 (I'm sorry but it's written in Japanese...I think you can read code parts at least.)

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If someone tell me reliable instruction documents for setting up VPN server on Ubuntu16.04 with L2TP/IPsec, I would appreciate it.

Solution

Don't use the aggressive mode, the connection will be less secure. Anyway try with this configuration. I use it on a my VPN Server with strongswan-5.3.5 and xl2tpd-1.3.6

ipsec.conf

config setup
    cachecrls=yes
    uniqueids=yes
    charondebug=""

conn %default
    keyingtries=%forever
    dpddelay=30s
    dpdtimeout=120s


conn L2TP
    dpdaction=clear
    #Server IP
    left=192.168.1.130
    #Server default gateway
    leftnexthop=192.168.1.254
    leftprotoport=17/1701
    rightprotoport=17/%any
    right=%any
    rightsubnet=0.0.0.0/0
    leftauth=psk
    rightauth=psk
    leftid="<insert-the-public-ip-here>"
    ikelifetime=1h
    keylife=8h
    ike=aes128-sha1-modp1536,aes128-sha1-modp1024,aes128-md5-modp1536,aes128-md5-modp1024,3des-sha1-modp1536,3des-sha1-modp1024,3des-md5-modp1536,3des-md5-modp1024
    esp=aes128-sha1-modp1536,aes128-sha1-modp1024,aes128-md5-modp1536,aes128-md5-modp1024,3des-sha1-modp1536,3des-sha1-modp1024,3des-md5-modp1536,3des-md5-modp1024
    auto=add
    keyexchange=ike
    type=transport

conn block
    auto=ignore
conn private
    auto=ignore
conn private-or-clear
    auto=ignore
conn clear-or-private
    auto=ignore
conn clear
    auto=ignore
conn packetdefault
    auto=ignore

ipsec.secrets

<insert-the-left-id-here> %any : PSK "<my-password>"

/etc/xl2tpd/xl2tpd.conf

[global]
ipsec saref = no
debug tunnel = no
debug avp = no
debug network = no
debug state = no


[lns default]
ip range = 10.0.0.20-10.0.0.30
local ip = 10.0.0.1
require authentication = yes
name = l2tp
pass peer = yes
ppp debug = no
pppoptfile = /etc/ppp/options.xl2tpd
length bit = yes
unix authentication = yes

/etc/ppp/options.xl2tpd

ipcp-accept-local
ipcp-accept-remote
ms-dns 10.0.0.1
auth
idle 1800
mtu 1200
mru 1200
nodefaultroute
lock
proxyarp
connect-delay 5000
name l2tpd
ifname l2tp
login

/etc/ppp/chap-secrets

username    *   "l2tppassword"  *

restart services

sudo service strongswan restart
sudo service xl2tpd restart

Comments

[Taiki Bessho]

Additionally, I needed to add a line: * l2tpd "" * to /etc/ppp/pap-secrets and It worked!!! Thank you!!

[Taiki Bessho]

Again, if you want to use chap authentication, you should write the line username * "l2tppassworddesu" * to /etc/ppp/chap-secrets instead of /etc/ppp/pap-secrets

[marstone]

works for me except for leftnexthop is deprecated in ubuntu 16.04 lts

[DarkVex]

@marstone yes, you're right! it's deprecated starting from the version 5.0.0 of strongswan (wiki.strongswan.org/projects/strongswan/wiki/…)