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wip: Adding stub for connection handler.

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This commit is contained in:
Alexandre Beaulieu 2019-04-15 09:19:34 -04:00
commit da613f9a16
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1 changed files with 36 additions and 25 deletions
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61
modules/rdp_proxy/rdp_proxy_linux_amd64.go
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@ -12,6 +12,8 @@ import (
"github.com/bettercap/bettercap/session"
"github.com/chifflier/nfqueue-go/nfqueue"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/evilsocket/islazy/fs"
"github.com/evilsocket/islazy/tui"
@ -104,7 +106,18 @@ func (mod *RdpProxy) destroyQueue() {
mod.queue = nil
}
func (mod *RdpProxy) runRule(enable bool) (err error) {
// Setup the proxy chain
"iptables -t nat -N BCAPRDP" // Create RDP chain
"iptables -t nat -X BCAPRDP" // Delete RDP chain
"iptables -t nat -I 1 PREROUTING -j BCAPRDP" // Go to BCAPRDP immediately before anything else
// Intercept SYNS (TODO: -m conntrack --cstate=new) ?
"iptables -I 1 -p tcp -m tcp --dport 3389 -d 10.0.0.0/24 -j NFQUEUE --queue-num 0 --queue-bypass"
// Starts or stops a particular proxy instances.
func (mod *RdpProxy) doProxy(target net.IPv4, enable bool) (err error) {
// Configure the firewall.
action := "-A"
if !enable {
action = "-D"
@ -132,8 +145,14 @@ func (mod *RdpProxy) runRule(enable bool) (err error) {
}
func (mod *RdpProxy) Configure() (err error) {
//
// The gist of what this function does is:
// 1. Create a chain in the NAT table called BCAPRDP.
// 2. Add a fallback rule as the first PREROUTING entry that puts all new TCP connections on port `rdp.proxy.port` into an NFQUEUE.
// 3. Add a default PREROUTING rule to jump to BCAPRDP.
// During cleanup, the entire BCAPRDP chain is dropped and all pyrdp instances are terminated
//
golog.SetOutput(ioutil.Discard)
mod.destroyQueue()
if err, mod.queueNum = mod.IntParam("packet.proxy.queue.num"); err != nil {
@ -146,27 +165,12 @@ func (mod *RdpProxy) Configure() (err error) {
return
}
if mod.pluginPath == "" {
return fmt.Errorf("The parameter %s can not be empty.", tui.Bold("packet.proxy.plugin"))
} else if !fs.Exists(mod.pluginPath) {
return fmt.Errorf("%s does not exist.", mod.pluginPath)
}
mod.Info("loading packet proxy plugin from %s ...", mod.pluginPath)
mod.Info("Starting NFQUEUE handler...")
var ok bool
var sym plugin.Symbol
if mod.plugin, err = plugin.Open(mod.pluginPath); err != nil {
return
} else if sym, err = mod.plugin.Lookup("OnPacket"); err != nil {
return
} else if mod.queueCb, ok = sym.(func(*nfqueue.Payload) int); !ok {
return fmt.Errorf("Symbol OnPacket is not a valid callback function.")
}
// Create the NFQUEUE handler.
mod.queue = new(nfqueue.Queue)
if err = mod.queue.SetCallback(dummyCallback); err != nil {
if err = mod.queue.SetCallback(OnRDPConnection); err != nil {
return
} else if err = mod.queue.Init(); err != nil {
return
@ -185,14 +189,21 @@ func (mod *RdpProxy) Configure() (err error) {
return nil
}
func OnRDPConnection(payload *nfqueue.Payload) int {
func (mod *RdpProxy) handleRdpConnection(payload *nfqueue.Payload) int {
log.Info("New Connection: %v", payload)
// 1. Check if the destination IP already has a PYRDP session active, if so, do nothing.
// 2. Otherwise:
// 2.1. Spawn a PYRDP instance on a fresh port
// 2.2. Add a NAT rule in the firewall for this particular target IP
// Force a retransmit to trigger the new firewall rules.
// TODO: Find a more efficient way to do this.
payload.SetVerdict(nfqueue.NF_DROP) // Force a retransmit to trigger the new firewall rules.
return 0
payload.SetVerdict(nfqueue.NF_DROP)
}
func dummyCallback(payload *nfqueue.Payload) int {
return mod.queueCb(payload)
// NFQUEUE needs a raw function.
func OnRDPConnection(payload *nfqueue.Payload) int {
return mod.handleRdpConnection()
}
func (mod *RdpProxy) Start() error {