Terima kasih kepada Sasha Pachev untuk hack yang bagus di atas.
vpnagentdjuga mengacaukan resolver dengan menimpa perubahan yang dibuat /etc/resolv.conf. Saya menyelesaikannya dengan akhirnya memenangkan perlombaan melawannya:
#!/bin/bash
dnsfix() {
[ -f /etc/resolv.conf.vpnbackup ] || echo "Not connected?" >&2 || return 0 # do nothing in case of failure
while ! diff -q /etc/resolv.conf /etc/resolv.conf.vpnbackup #>/dev/null
do
cat /etc/resolv.conf.vpnbackup >/etc/resolv.conf
done
chattr +i /etc/resolv.conf
diff -q /etc/resolv.conf /etc/resolv.conf.vpnbackup >/dev/null
}
while ! dnsfix
do
echo "Retrying..."
chattr -i /etc/resolv.conf
done
Jangan lupa chattr -i /etc/resolv.confketika memutuskan koneksi.
Saya mencoba menyelesaikannya dengan memotong panggilan balik, seperti untuk metode rute di atas, tetapi belum dapat menemukan panggilan balik atau metode yang sesuai.
Update1 / 2: A stracemengungkapkan yang vpnagentdmenggunakan inotifyAPI untuk memantau perubahan file resolver. Dari sana dan seterusnya menurun. Inilah retas tambahan:
int _ZN18CFileSystemWatcher11AddNewWatchESsj(void *string, unsigned int integer)
{
return 0;
}
Itu sedikit berlebihan, memang, karena menonaktifkan semua file yang mengawasi agen. Tapi sepertinya berhasil OK.
Skrip pembungkus klien vpn di bawah ini mengintegrasikan semua fungsi (diperbarui untuk menyertakan peretasan tambahan ini). chattrtidak lagi digunakan / dibutuhkan.
Pembaruan 3: Memperbaiki pengaturan nama pengguna / kata sandi dalam skrip. Sekarang menggunakan vpn.conffile dengan format yang dijelaskan di bawah ini (dan izin root-only).
#!/bin/bash
# Change this as needed
CONF="/etc/vpnc/vpn.conf"
# vpn.conf format
#gateway <IP>
#username <username>
#password <password>
#delete_routes <"route spec"...> eg. "default gw 0.0.0.0 dev cscotun0"
#add_routes <"route spec"...> eg. "-net 192.168.10.0 netmask 255.255.255.0 dev cscotun0" "-host 10.10.10.1 dev cscotun0"
ANYCONNECT="/opt/cisco/anyconnect"
usage() {
echo "Usage: $0 {connect|disconnect|state|stats|hack}"
exit 1
}
CMD="$1"
[ -z "$CMD" ] && usage
ID=`id -u`
VPNC="$ANYCONNECT/bin/vpn"
dnsfix() {
[ -f /etc/resolv.conf.vpnbackup ] || echo "Not connected?" >&2 || return 0 # do nothing in case of failure
while ! diff -q /etc/resolv.conf /etc/resolv.conf.vpnbackup >/dev/null
do
cat /etc/resolv.conf.vpnbackup >/etc/resolv.conf
done
# chattr +i /etc/resolv.conf
diff -q /etc/resolv.conf /etc/resolv.conf.vpnbackup >/dev/null
}
case "$CMD" in
"connect")
[ $ID -ne 0 ] && echo "Needs root." && exit 1
HOST=`grep ^gateway $CONF | awk '{print $2}'`
USER=`grep ^user $CONF | awk '{print $2}'`
PASS=`grep ^password $CONF | awk '{print $2}'`
OLDIFS=$IFS
IFS='"'
DEL_ROUTES=(`sed -n '/^delete_routes/{s/delete_routes[ \t\"]*//;s/\"[ \t]*\"/\"/g;p}' $CONF`)
ADD_ROUTES=(`sed -n '/^add_routes/{s/add_routes[ \t\"]*//;s/\"[ \t]*\"/\"/g;p}' $CONF`)
IFS=$OLDIFS
/usr/bin/expect <<EOF
set vpn_client "$VPNC";
set ip "$HOST";
set user "$USER";
set pass "$PASS";
set timeout 5
spawn \$vpn_client connect \$ip
match_max 100000
expect {
timeout {
puts "timeout error\n"
spawn killall \$vpn_client
exit 1
}
">> The VPN client is not connected." { exit 0};
">> state: Disconnecting" { exit 0};
"Connect Anyway?"
}
sleep .1
send -- "y\r"
expect {
timeout {
puts "timeout error\n"
spawn killall \$vpn_client
exit 1
}
"Username:"
}
sleep .1
send -- "\$user\r"
expect {
timeout {
puts "timeout error\n"
spawn killall \$vpn_client
exit 1
}
"Password: "
}
send -- "\$pass\r";
expect eof
EOF
sleep 2
# iptables
iptables-save | grep -v DROP | iptables-restore
# routes
for ROUTE in "${DEL_ROUTES[@]}"
do
# echo route del $ROUTE
route del $ROUTE
done
for ROUTE in "${ADD_ROUTES[@]}"
do
# echo route add $ROUTE
route add $ROUTE
done
# dns
while ! dnsfix
do
echo "Try again..."
# chattr -i /etc/resolv.conf
done
echo "done."
;;
"disconnect")
# [ $ID -ne 0 ] && echo "Needs root." && exit 1
# dns
# chattr -i /etc/resolv.conf
$VPNC disconnect
;;
"state"|"stats")
$VPNC $CMD
;;
"hack")
[ $ID -ne 0 ] && echo "Needs root." && exit 1
/etc/init.d/vpnagentd stop
sleep 1
killall -9 vpnagentd 2>/dev/null
cat - >/tmp/hack.c <<EOF
#include <sys/socket.h>
#include <linux/netlink.h>
int _ZN27CInterfaceRouteMonitorLinux20routeCallbackHandlerEv()
{
int fd=50; // max fd to try
char buf[8192];
struct sockaddr_nl sa;
socklen_t len = sizeof(sa);
while (fd) {
if (!getsockname(fd, (struct sockaddr *)&sa, &len)) {
if (sa.nl_family == AF_NETLINK) {
ssize_t n = recv(fd, buf, sizeof(buf), MSG_DONTWAIT);
}
}
fd--;
}
return 0;
}
int _ZN18CFileSystemWatcher11AddNewWatchESsj(void *string, unsigned int integer)
{
return 0;
}
EOF
gcc -o /tmp/libhack.so -shared -fPIC /tmp/hack.c
mv /tmp/libhack.so $ANYCONNECT
sed -i "s+^\([ \t]*\)$ANYCONNECT/bin/vpnagentd+\1LD_PRELOAD=$ANYCONNECT/lib/libhack.so $ANYCONNECT/bin/vpnagentd+" /etc/init.d/vpnagentd
rm -f /tmp/hack.c
/etc/init.d/vpnagentd start
echo "done."
;;
*)
usage
;;
esac
