Estou executando um OpenVPN-Server (Debian 8) para fins de privacidade quando uso wifi público. Portanto, todo o tráfego de rede do cliente deve ser manipulado pela conexão VPN. A configuração do servidor e do cliente é fornecida abaixo.
Configuração do servidor:
port 1194
proto tcp
dev tun
ca /etc/openvpn/ca.crt
cert /etc/openvpn/server.crt
key /etc/openvpn/server.key
dh /etc/openvpn/dh.pem
tls-auth /etc/openvpn/tlsauth.key 0
user nobody
group nogroup
server 10.11.12.0 255.255.255.0
ifconfig-pool-persist ipp.txt
keepalive 10 120
push "redirect-gateway def1 bypass-dhcp"
push "dhcp-option DNS 8.8.8.8"
push "dhcp-option DNS 8.8.4.4"
persist-key
persist-tun
comp-lzo
status openvpn-status.log
verb 3
Configuração do cliente:
client
remote X.X.X.X 1194
proto tcp
dev tun
resolv-retry-infinite
nobind
user nobody
group nogroup
persist-key
persist-tun
ca /etc/openvpn/ca.crt
cert /etc/openvpn/client.crt
key /etc/openvpn/client.key
tls-auth /etc/openvpn/tlsauth.key 0
comp-lzo 0
verb 2
Quando o serviço VPN é iniciado no cliente, a tabela de roteamento é alterada conforme abaixo:
Tabela de roteamento (192.168.178.0/24 denota o wifi público):
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 10.11.12.13 128.0.0.0 UG 0 0 0 tun0
0.0.0.0 192.168.178.1 0.0.0.0 UG 1024 0 0 wlan0
10.11.12.1 10.11.12.13 255.255.255.255 UGH 0 0 0 tun0
10.11.12.13 0.0.0.0 255.255.255.255 UH 0 0 0 tun0
128.0.0.0 10.11.12.13 128.0.0.0 UG 0 0 0 tun0
169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 wlan0
192.168.178.0 0.0.0.0 255.255.255.0 U 0 0 0 wlan0
X.X.X.X 192.168.178.1 255.255.255.255 UGH 0 0 0 wlan0
A seção relevante do syslog ao iniciar o openvpn:
ovpn-client[3395]: OpenVPN 2.3.4 i586-pc-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [PKCS11] [MH] [IPv6] built on Dec 1 2014
ovpn-client[3395]: library versions: OpenSSL 1.0.1k 8 Jan 2015, LZO 2.08
ovpn-client[3395]: WARNING: No server certificate verification method has been enabled. See http://openvpn.net/howto.html#mitm for more info.
ovpn-client[3395]: Control Channel Authentication: using '/etc/openvpn/tlsauth.key' as a OpenVPN static key file
ovpn-client[3395]: Outgoing Control Channel Authentication: Using 160 bit message hash 'SHA1' for HMAC authentication
ovpn-client[3395]: Incoming Control Channel Authentication: Using 160 bit message hash 'SHA1' for HMAC authentication
ovpn-client[3396]: NOTE: UID/GID downgrade will be delayed because of --client, --pull, or --up-delay
ovpn-client[3396]: Attempting to establish TCP connection with [AF_INET]X.X.X.X:1194 [nonblock]
ovpn-client[3396]: TCP connection established with [AF_INET]X.X.X.X:1194
ovpn-client[3396]: TCPv4_CLIENT link local: [undef]
ovpn-client[3396]: TCPv4_CLIENT link remote: [AF_INET]X.X.X.X:1194
ovpn-client[3396]: VERIFY OK: depth=1, [...]
ovpn-client[3396]: VERIFY OK: depth=0, [...]
ovpn-client[3396]: Data Channel Encrypt: Cipher 'BF-CBC' initialized with 128 bit key
ovpn-client[3396]: Data Channel Encrypt: Using 160 bit message hash 'SHA1' for HMAC authentication
ovpn-client[3396]: Data Channel Decrypt: Cipher 'BF-CBC' initialized with 128 bit key
ovpn-client[3396]: Data Channel Decrypt: Using 160 bit message hash 'SHA1' for HMAC authentication
ovpn-client[3396]: Control Channel: TLSv1, cipher TLSv1/SSLv3 DHE-RSA-AES256-SHA, 2048 bit RSA
ovpn-client[3396]: [VPN-Server] Peer Connection Initiated with [AF_INET]X.X.X.X:1194
ovpn-client[3396]: TUN/TAP device tun0 opened
ovpn-client[3396]: do_ifconfig, tt->ipv6=0, tt->did_ifconfig_ipv6_setup=0
ovpn-client[3396]: /sbin/ip link set dev tun0 up mtu 1500
NetworkManager[556]: <info> (tun0): carrier is OFF
NetworkManager[556]: <info> (tun0): new Tun device (driver: 'unknown' ifindex: 15)
NetworkManager[556]: <info> (tun0): exported as /org/freedesktop/NetworkManager/Devices/14
ovpn-client[3396]: /sbin/ip addr add dev tun0 local 10.11.12.14 peer 10.11.12.13
NetworkManager[556]: <info> (tun0): link connected
ovpn-client[3396]: ERROR: Linux route add command failed: external program exited with error status: 2
ovpn-client[3396]: GID set to nogroup
ovpn-client[3396]: UID set to nobody
ovpn-client[3396]: Initialization Sequence Completed
NetworkManager[556]: <info> (tun0): device state change: unmanaged -> unavailable (reason 'connection-assumed') [10 20 41]
NetworkManager[556]: <info> (tun0): device state change: unavailable -> disconnected (reason 'connection-assumed') [20 30 41]
NetworkManager[556]: <info> Activation (tun0) starting connection 'tun0'
NetworkManager[556]: <info> Activation (tun0) Stage 1 of 5 (Device Prepare) scheduled...
NetworkManager[556]: <info> devices added (path: /sys/devices/virtual/net/tun0, iface: tun0)
NetworkManager[556]: <info> device added (path: /sys/devices/virtual/net/tun0, iface: tun0): no ifupdown configuration found.
NetworkManager[556]: <info> Activation (tun0) Stage 1 of 5 (Device Prepare) started...
NetworkManager[556]: <info> (tun0): device state change: disconnected -> prepare (reason 'none') [30 40 0]
NetworkManager[556]: <info> Activation (tun0) Stage 2 of 5 (Device Configure) scheduled...
NetworkManager[556]: <info> Activation (tun0) Stage 1 of 5 (Device Prepare) complete.
NetworkManager[556]: <info> Activation (tun0) Stage 2 of 5 (Device Configure) starting...
NetworkManager[556]: <info> (tun0): device state change: prepare -> config (reason 'none') [40 50 0]
NetworkManager[556]: <info> Activation (tun0) Stage 2 of 5 (Device Configure) successful.
NetworkManager[556]: <info> Activation (tun0) Stage 3 of 5 (IP Configure Start) scheduled.
NetworkManager[556]: <info> Activation (tun0) Stage 2 of 5 (Device Configure) complete.
NetworkManager[556]: <info> Activation (tun0) Stage 3 of 5 (IP Configure Start) started...
NetworkManager[556]: <info> (tun0): device state change: config -> ip-config (reason 'none') [50 70 0]
NetworkManager[556]: <info> Activation (tun0) Stage 5 of 5 (IPv4 Configure Commit) scheduled...
NetworkManager[556]: <info> Activation (tun0) Stage 3 of 5 (IP Configure Start) complete.
NetworkManager[556]: <info> Activation (tun0) Stage 5 of 5 (IPv4 Commit) started...
NetworkManager[556]: <info> (tun0): device state change: ip-config -> ip-check (reason 'none') [70 80 0]
NetworkManager[556]: <info> Activation (tun0) Stage 5 of 5 (IPv4 Commit) complete.
NetworkManager[556]: <info> (tun0): device state change: ip-check -> secondaries (reason 'none') [80 90 0]
NetworkManager[556]: <info> (tun0): device state change: secondaries -> activated (reason 'none') [90 100 0]
NetworkManager[556]: <info> Activation (tun0) successful, device activated.
Minhas perguntas são:
-
A tabela de roteamento está correta? Para mim, parece um pouco estranho devido às duas entradas padrão. Além disso, ao gravar o tráfego no roteador wifi público (usando o tcpdump), nem todo o tráfego é roteado pela VPN.
-
O que o erro ( ERROR: Linux route add command failed: external program exited with error status: 2 ) no syslog diz? Isso pode ser conectado à primeira pergunta?
Edit: Obrigado pela resposta, Michal. Para reduzir o tráfego multicast / local / ..., estou planejando também usar o iptables para eliminar esse tráfego também.
Estou tentando usar as regras do iptables da seguinte forma:
#!/bin/bash
GATEWAY="192.168.178.1"
iptables -F
# Allow loopback device (internal communication)
iptables -A INPUT -i lo -j ACCEPT
iptables -A OUTPUT -o lo -j ACCEPT
# Allow DHCP communication with gateway
iptables -A INPUT -i wlan0 -p udp -s $GATEWAY/32 --dport 67:68 --sport 67:68 -j ACCEPT
iptables -A OUTPUT -o wlan0 -p udp -d $GATEWAY/32 --dport 67:68 --sport 67:68 -j ACCEPT
# Allow ICMP communication with gateway
iptables -A INPUT -i wlan0 -p icmp -s $GATEWAY/32 -j ACCEPT
iptables -A OUTPUT -o wlan0 -p icmp -d $GATEWAY/32 -j ACCEPT
#Allow VPN establishment
iptables -A OUTPUT -p tcp --dport 1194 -j ACCEPT
iptables -A INPUT -p tcp --sport 1194 -j ACCEPT
#Accept all TUN connections (tun = VPN tunnel)
iptables -A OUTPUT -o tun+ -j ACCEPT
iptables -A INPUT -i tun+ -j ACCEPT
#Set default policies to drop all communication unless specifically allowed
iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP
IMO, essas regras devem ser suficientes para obter um IP atribuído pelo gateway, estabelecer uma conexão com o servidor OpenVPN e lidar com todo o tráfego nessa conexão. Mas o DNS não funciona, embora também deva usar a conexão VPN. Por que isso não funciona?
Próxima edição: Configure um servidor de nomes local ( dnsmasq ) no servidor VPN. A configuração do servidor mudou para
push "dhcp-option DNS 10.11.12.1"
em vez de
push "dhcp-option DNS 8.8.8.8"
push "dhcp-option DNS 8.8.4.4"
Ao executar dig +short serverfault.com @10.11.12.1 no próprio servidor VPN, o nome do host poderá ser recuperado com êxito. Se o comando for executado em um host diferente que não esteja usando VPN ( dig +short stackoverflow.com @X.X.X.X ), o nome do host também poderá ser recuperado com êxito. No entanto, quando o comando é executado em um cliente conectado à VPN ( dig +short stackoverflow.com @10.11.12.1 ), o comando falha ( ;; connection timed out; no servers could be reached ). Por quê? Iptables são configurados para ACCEPT all.