303 lines
12 KiB
Nim
303 lines
12 KiB
Nim
import asyncfutures, asyncdispatch, asyncnet, strformat
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from net import IpAddress, Port, `$`, `==`, getPrimaryIPAddr, toSockAddr, parseIpAddress
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from nativesockets import SockAddr, Sockaddr_storage, SockLen, setSockOptInt
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from sequtils import any
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import asyncutils
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import ip_packet
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import network_interface
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import raw_socket
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var IPPROTO_IP {.importc: "IPPROTO_IP", header: "<netinet/in.h>".}: cint
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var IP_TTL {.importc: "IP_TTL", header: "<netinet/in.h>".}: cint
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const Timeout = 3000
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type
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ConnectAttempt* = ref object
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srcIp: IpAddress
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srcPort: Port
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dstIp: IpAddress
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dstPorts: seq[Port]
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firewallRules: seq[string]
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AcceptAttempt* = ref object
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srcIp: IpAddress
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srcPort: Port
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dstIp: IpAddress
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dstPorts: seq[Port]
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seqNums: seq[uint32]
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firewallRules: seq[string]
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future: Future[AsyncSocket]
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TcpSyniPuncher* = ref object
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connectAttempts: seq[ConnectAttempt]
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acceptAttempts: seq[AcceptAttempt]
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PunchProgressCb* = proc (seqNums: seq[uint32]) {.async.}
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PunchHoleError* = object of ValueError
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proc makeFirewallRule(srcIp: IpAddress, srcPort: Port,
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dstIp: IpAddress, dstPort: Port): string =
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result = fmt"""-w \
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-d {srcIp} \
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-p icmp \
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--icmp-type time-exceeded \
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-m conntrack \
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--ctstate RELATED \
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--ctproto tcp \
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--ctorigsrc {srcIp} \
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--ctorigsrcport {srcPort.int} \
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--ctorigdst {dstIp} \
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--ctorigdstport {dstPort.int} \
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-j DROP"""
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proc iptablesInsert(chain: string, rule: string) {.async.} =
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let firewall_cmd = fmt"iptables -I {chain} {rule}"
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discard await asyncExecCmd(firewall_cmd)
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proc iptablesDelete(chain: string, rule: string) {.async.} =
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let firewall_cmd = fmt"iptables -D {chain} {rule}"
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discard await asyncExecCmd(firewall_cmd)
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proc addFirewallRules[T](attempt: T) {.async.} =
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for dstPort in attempt.dstPorts:
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let rule = makeFirewallRule(attempt.srcIp, attempt.srcPort,
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attempt.dstIp, dstPort)
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try:
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await iptablesInsert("INPUT", rule)
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attempt.firewallRules.add(rule)
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except OSError as e:
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echo "cannot add firewall rule: ", e.msg
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raise newException(PunchHoleError, e.msg)
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proc deleteFirewallRules[T](attempt: T) {.async.} =
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for rule in attempt.firewallRules:
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# FIXME: close sock?
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try:
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await iptablesDelete("INPUT", rule)
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except OSError:
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# At least we tried
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discard
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proc injectTcpPacket(rawFd: AsyncFD, ipPacket: IpPacket) {.async.} =
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assert(ipPacket.protocol == tcp)
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try:
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let packet = serialize(ipPacket)
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var sockaddr: Sockaddr_storage
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var sockaddrLen: SockLen
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toSockAddr(ipPacket.ipAddrDst, ipPacket.tcpPortDst, sockaddr, sockaddrLen)
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await rawFd.sendTo(packet.cstring, packet.len,
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cast[ptr SockAddr](addr sockaddr), sockaddrLen)
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except OSError as e:
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raise newException(PunchHoleError, e.msg)
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proc captureSeqNumbers(attempt: ConnectAttempt, rawFd: AsyncFD,
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cb: PunchProgressCb) {.async.} =
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# FIXME: timeout?
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var seqNums = newSeq[uint32]()
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while seqNums.len < attempt.dstPorts.len:
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let packet = await rawFd.recv(4000)
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if packet == "":
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break
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let parsed = parseEthernetPacket(packet)
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if parsed.protocol == tcp and
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parsed.ipAddrSrc == attempt.srcIp and
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parsed.tcpPortSrc.int == attempt.srcPort.int and
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parsed.ipAddrDst == attempt.dstIp and
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parsed.tcpFlags == {SYN}:
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for port in attempt.dstPorts:
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if parsed.tcpPortDst.int == port.int:
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seqNums.add(parsed.tcpSeqNumber)
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break
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await cb(seqNums)
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proc captureAndResendAck(attempt: ConnectAttempt, captureFd: AsyncFD,
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injectFd: AsyncFD) {.async.} =
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while true:
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let packet = await captureFd.recv(4000)
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if packet == "":
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break
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var parsed = parseEthernetPacket(packet)
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if parsed.protocol == tcp and
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parsed.ipAddrSrc == attempt.srcIp and
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parsed.tcpPortSrc.int == attempt.srcPort.int and
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parsed.ipAddrDst == attempt.dstIp and
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parsed.tcpFlags == {ACK}:
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for port in attempt.dstPorts:
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if parsed.tcpPortDst.int == port.int:
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parsed.ipTTL = 64
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echo &"[{parsed.ipAddrSrc}:{parsed.tcpPortSrc.int} -> {parsed.ipAddrDst}:{parsed.tcpPortDst}, SEQ {parsed.tcpSeqNumber}] resending ACK with TTL {parsed.ipTTL}"
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await injectFd.injectTcpPacket(parsed)
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return
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proc initPuncher*(): TcpSyniPuncher = TcpSyniPuncher()
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proc findConnectAttempt(puncher: TcpSyniPuncher, srcIp: IpAddress,
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srcPort: Port, dstIp: IpAddress,
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dstPorts: seq[Port]): int =
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for (index, attempt) in puncher.connectAttempts.pairs():
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if attempt.srcIp == srcIp and attempt.srcPort == srcPort and
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attempt.dstIp == dstIp and
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attempt.dstPorts.any(proc (p: Port): bool = p in dstPorts):
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return index
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return -1
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proc findAcceptAttempt(puncher: TcpSyniPuncher, srcIp: IpAddress,
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srcPort: Port, dstIp: IpAddress,
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dstPorts: seq[Port]): int =
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for (index, attempt) in puncher.acceptAttempts.pairs():
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if attempt.srcIp == srcIp and attempt.srcPort == srcPort and
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attempt.dstIp == dstIp and
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attempt.dstPorts.any(proc (p: Port): bool = p in dstPorts):
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return index
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return -1
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proc findAcceptAttemptsByLocalAddr(puncher: TcpSyniPuncher, address: IpAddress,
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port: Port): seq[AcceptAttempt] =
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for attempt in puncher.acceptAttempts:
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if attempt.srcIp == address and attempt.srcPort == port:
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result.add(attempt)
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proc predictPortRange(dstPorts: seq[Port]): seq[Port] =
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# TODO: do real port prediction
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result = newSeq[Port](1)
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let basePort = min(dstPorts[1].uint16,
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uint16.high - (result.len - 1).uint16)
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for i in 0 .. result.len - 1:
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result[i] = Port(basePort + i.uint16)
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proc cleanup*(puncher: TcpSyniPuncher) {.async.} =
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for attempt in puncher.connectAttempts:
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await attempt.deleteFirewallRules()
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for attempt in puncher.acceptAttempts:
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await attempt.deleteFirewallRules()
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proc doConnect(srcIp: IpAddress, srcPort: Port, dstIp: IpAddress, dstPort: Port,
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future: Future[AsyncSocket]) {.async.} =
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let sock = newAsyncSocket()
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sock.setSockOpt(OptReuseAddr, true)
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sock.getFd.setSockOptInt(IPPROTO_IP, IP_TTL, 2)
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echo &"doConnect {srcIp}:{srcPort} -> {dstIp}:{dstPort}"
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sock.bindAddr(srcPort, $srcIp)
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try:
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await sock.connect($dstIp, dstPort)
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sock.getFd.setSockOptInt(IPPROTO_IP, IP_TTL, 64)
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future.complete(sock)
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except OSError as e:
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echo &"connection {srcIP}:{srcPort.int} -> {dstIp}:{dstPort.int} failed: ", e.msg
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discard
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proc connect*(puncher: TcpSyniPuncher, srcPort: Port, dstIp: IpAddress,
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dstPorts: seq[Port],
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progressCb: PunchProgressCb): Future[AsyncSocket] {.async.} =
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let localIp = getPrimaryIPAddr(dstIp)
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if puncher.findConnectAttempt(localIp, srcPort, dstIp, dstPorts) != -1:
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raise newException(PunchHoleError, "hole punching for given parameters already active")
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let attempt = ConnectAttempt(srcIp: localIp, srcPort: srcPort, dstIp: dstIp,
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dstPorts: predictPortRange(dstPorts))
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puncher.connectAttempts.add(attempt)
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await attempt.addFirewallRules()
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let iface = fromIpAddress(attempt.srcIp)
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let captureSeqFd = setupEthernetCapturingSocket(iface)
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let captureAckFd = setupEthernetCapturingSocket(iface)
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let injectAckFd = setupTcpInjectingSocket()
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asyncCheck attempt.captureSeqNumbers(captureSeqFd, progressCb)
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asyncCheck attempt.captureAndResendAck(captureAckFd, injectAckFd)
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try:
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let connectFuture = newFuture[AsyncSocket]("connect")
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for dstPort in attempt.dstPorts:
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asyncCheck doConnect(attempt.srcIp, attempt.srcPort, attempt.dstIp,
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dstPort, connectfuture)
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await connectFuture or sleepAsync(Timeout)
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await attempt.deleteFirewallRules()
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puncher.connectAttempts.del(puncher.connectAttempts.find(attempt))
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if connectFuture.finished():
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result = connectFuture.read()
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else:
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raise newException(PunchHoleError, "timeout")
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except OSError as e:
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raise newException(PunchHoleError, e.msg)
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proc prepareAccept(attempt: AcceptAttempt) {.async.} =
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for dstPort in attempt.dstPorts:
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try:
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let sock = newAsyncSocket()
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sock.setSockOpt(OptReuseAddr, true)
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sock.getFd.setSockOptInt(IPPROTO_IP, IP_TTL, 2)
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sock.bindAddr(attempt.srcPort, $(attempt.srcIp))
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let connectFuture = sock.connect($(attempt.dstIp), dstPort)
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await connectFuture or sleepAsync(Timeout)
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if connectFuture.finished():
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echo "connected during accept phase"
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sock.close()
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except OSError:
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discard
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proc doAccept(puncher: TcpSyniPuncher, srcIp: IpAddress,
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srcPort: Port) {.async.} =
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let sock = newAsyncSocket()
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sock.setSockOpt(OptReuseAddr, true)
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sock.bindAddr(srcPort, $(srcIp))
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sock.listen()
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while true:
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let acceptFuture = sock.accept()
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await acceptFuture or sleepAsync(Timeout)
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if acceptFuture.finished():
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let peer = acceptFuture.read()
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let (peerAddr, peerPort) = peer.getPeerAddr()
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let peerIp = parseIpAddress(peerAddr)
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let i = puncher.findAcceptAttempt(srcIp, srcPort, peerIp, @[peerPort])
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if i == -1:
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echo "Accepted connection, but no attempt found. Discarding."
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else:
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let attempt = puncher.acceptAttempts[i]
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attempt.future.complete(peer)
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else:
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let attempts = puncher.findAcceptAttemptsByLocalAddr(srcIp, srcPort)
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# FIXME: should attempts have timestamps, so we can decide here which ones to delete?
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if attempts.len() <= 1:
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break
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sock.close()
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proc accept*(puncher: TcpSyniPuncher, srcPort: Port, dstIp: IpAddress,
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dstPorts: seq[Port],
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seqNums: seq[uint32]): Future[AsyncSocket] {.async.} =
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let localIp = getPrimaryIPAddr(dstIp)
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let existingAttempts = puncher.findAcceptAttemptsByLocalAddr(localIp, srcPort)
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if existingAttempts.len() == 0:
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echo &"accepting connections from {dstIp}:{dstPorts[0].int}"
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asyncCheck puncher.doAccept(localIp, srcPort)
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else:
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for a in existingAttempts:
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if a.dstIp == dstIp and
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a.dstPorts.any(proc (p: Port): bool = p in dstPorts):
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raise newException(PunchHoleError, "hole punching for given parameters already active")
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let attempt = AcceptAttempt(srcIp: localIp, srcPort: srcPort, dstIp: dstIp,
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dstPorts: dstPorts, seqNums: seqNums,
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future: newFuture[AsyncSocket]("accept"))
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puncher.acceptAttempts.add(attempt)
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await attempt.addFirewallRules()
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await attempt.prepareAccept()
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try:
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let rawFd = setupTcpInjectingSocket()
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for dstPort in attempt.dstPorts:
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for seqNum in attempt.seqNums:
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let ipPacket = IpPacket(protocol: tcp, ipAddrSrc: attempt.dstIp,
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ipAddrDst: attempt.srcIp, ipTTL: 64,
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tcpPortSrc: dstPort,
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tcpPortDst: attempt.srcPort,
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tcpSeqNumber: seqNum, tcpAckNumber: 0,
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tcpFlags: {SYN}, tcpWindowSize: 1452 * 10)
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echo &"[{ipPacket.ipAddrSrc}:{ipPacket.tcpPortSrc} -> {ipPacket.ipAddrDst}:{ipPacket.tcpPortDst}, SEQ {ipPacket.tcpSeqNumber}] injecting SYN"
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asyncCheck rawFd.injectTcpPacket(ipPacket)
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await attempt.future or sleepAsync(Timeout)
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await attempt.deleteFirewallRules()
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puncher.acceptAttempts.del(puncher.acceptAttempts.find(attempt))
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if attempt.future.finished():
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result = attempt.future.read()
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else:
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raise newException(PunchHoleError, "timeout")
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except OSError as e:
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echo &"accepting connections from {dstIP}:{dstPorts[0].int} failed: ", e.msg
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