无法在AWS中使用Iptables和Strongswan进行NAT IP

问题描述

我刚刚配置了Strongswan，可以在AWS EC2实例上成功建立VPN隧道，但是流量存在问题，因为我们需要对EC2实例的私有IP地址进行NAT，以便所有流量都通过VPN来自特定的IP。

但是目前，如果我ping [DESTINATION_IP]地址，我的流量仍然来自我的专用IP。我在iptables中尝试了几个PREROUTING和POSTROUTING规则，但似乎没有任何效果。谁能解释这个问题可能是什么？

当前设置

在AWS Source / Destination中已禁用检查。

strongswan状态全部

Listening IP addresses:
  [PRIVATE_IP]
Connections:
          vpn:  %any...[VPN_FIREWALL_IP]  IKEv2,dpddelay=10s
          vpn:   local:  [[ELASTIC_PUBLIC_IP]] uses pre-shared key authentication
          vpn:   remote: [[VPN_FIREWALL_IP]] uses pre-shared key authentication
          vpn:   child:  0.0.0.0/0 === [DESTINATION_IP]/32 TUNNEL,dpdaction=restart
Security Associations (1 up,0 connecting):
          vpn[1]: ESTABLISHED 5 seconds ago,[PRIVATE_IP][[ELASTIC_PUBLIC_IP]]...[VPN_FIREWALL_IP][[VPN_FIREWALL_IP]]
          vpn[1]: IKEv2 SPIs: 6055db442ef8607c_i* 3d2ec0bb945e9a2c_r,pre-shared key reauthentication in 7 hours
          vpn[1]: IKE proposal: AES_CBC_128/HMAC_SHA2_256_128/PRF_HMAC_SHA1/MODP_2048
          vpn{1}:  INSTALLED,TUNNEL,reqid 1,ESP in UDP SPIs: ca9d2ca0_i df70a539_o
          vpn{1}:  AES_CBC_128/HMAC_SHA1_96,0 bytes_i,0 bytes_o,rekeying in 46 minutes
          vpn{1}:   [NAT_SOURCE_IP]/31 === [DESTINATION_IP]/32

ipsec.conf

config setup
    charondebug="all"
    uniqueids=no

conn %default
    ikelifetime=28800s
    keyexchange=ikev2
    keylife=3600s
    keyingtries=%forever
    mobike=no

conn vpn
    authby=psk
    auto=start
    dpddelay=10s
    dpdtimeout=30s
    dpdaction=restart
    ike=aes128-sha256-prfsha1-modp2048!
    esp=aes128-sha256-modp2048,aes128-sha1-modp2048!
    left=%defaultroute
    leftid=[ELASTIC_PUBLIC_IP]
    leftsubnet=0.0.0.0/0
    leftfirewall=yes
    rightsubnet=[DESTINATION_IP]/32
    right=[VPN_FIREWALL_IP]
    rightid=[VPN_FIREWALL_IP]
    type=tunnel
    mark=100

iptables保存

*nat
:PREROUTING ACCEPT [9728:543855]
:INPUT ACCEPT [7882:388791]
:OUTPUT ACCEPT [20219:1527154]
:POSTROUTING ACCEPT [20725:1569658]
COMMIT
*filter
:INPUT ACCEPT [142:30437]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [188:34735]
-A FORWARD -s [DESTINATION_IP]/32 -d [NAT_SOURCE_IP]/31 -i eth0 -m policy --dir in --pol ipsec --reqid 1 --proto esp -j ACCEPT
-A FORWARD -s [NAT_SOURCE_IP]/31 -d [DESTINATION_IP]/32 -o eth0 -m policy --dir out --pol ipsec --reqid 1 --proto esp -j ACCEPT
COMMIT

解决方法

如果我正确理解您的问题，则您正在询问如何使用Strongswan在EC2实例上设置源NAT。我运行相同的设置，在本例中，遵循[1]中的iptables规则可提供所需的功能：

iptables -t nat -A POSTROUTING -s <NAT_SOURCE_IP>/24 -o eth0 -m policy --dir out --pol ipsec -j ACCEPT
iptables -t nat -A POSTROUTING -s <NAT_SOURCE_IP>/24 -o eth0 -j MASQUERADE

[1] https://wiki.strongswan.org/projects/strongswan/wiki/ForwardingAndSplitTunneling