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Как настроить iptables для работы с tcpcrypt?

Фон

ОС: работа Ubuntu 16.04 x64 VirtualBox

Я - разработчик с минимальным знанием Ubuntu/Linux и был присвоен проекту, где цель состоит в том, чтобы использовать tcpcrypt при общении с определенными конечными точками.

tcpcrypt идет со сценарием оболочки, который устанавливает необходимые записи в iptables для маршрутизации пакетов к tcpcrypt для encrpt/decrypt. После выполнения этого сценария iptables похож:

фильтр

Chain INPUT (policy ACCEPT 4 packets, 552 bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 ACCEPT     tcp  --  lo     any     anywhere             anywhere             tcp dpt:65530 tos match0x22/0xff
    0     0 NFQUEUE    tcp  --  any    any    !localhost            anywhere             tcp dpt:65530 flags:FIN,SYN,RST,PSH,ACK,URG/SYN NFQUEUE num 666
    0     0 NFQUEUE    tcp  --  any    any     anywhere             anywhere             multiport sports  !ssh,261,https,nntps,614,ldaps,684,695,ftps-data,ftps,telnets:pop3s tcp flags:FIN,SYN,RST,PSH,ACK,URG/SYN,ACK NFQUEUE num 666

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain OUTPUT (policy ACCEPT 4 packets, 536 bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 NFQUEUE    tcp  --  any    any     anywhere             anywhere             multiport dports  !ssh,261,https,nntps,614,ldaps,684,695,ftps-data,ftps,telnets:pop3s tos match0x04/0xff owner UID match tcpcryptd NFQUEUE num 666
    0     0 NFQUEUE    tcp  --  any    any     anywhere             anywhere             tcp spt:65530 flags:FIN,SYN,RST,PSH,ACK,URG/SYN,ACK NFQUEUE num 666

туземный

Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination         
REDIRECT   tcp  --                                            multiport dports  !ssh,261,https,nntps,614,ldaps,684,695,ftps-data,ftps,telnets:pop3s redir ports 65530

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     tcp  --  anywhere             anywhere             multiport dports  !ssh,261,https,nntps,614,ldaps,684,695,ftps-data,ftps,telnets:pop3s owner UID match tcpcryptd
REDIRECT   tcp  --  anywhere             anywhere             multiport dports  !ssh,261,https,nntps,614,ldaps,684,695,ftps-data,ftps,telnets:pop3s redir ports 65530

искажение

Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination         

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         

Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination         
TOS        all  --  anywhere             anywhere             tos match0x04/0xff TOS and 0x00

С этими записями каждый пакет помещается на очередь, где tcpcrypt выбирает для enc/dec.

ОБНОВЛЕНИЕ

Это - сценарий для iptables:

#!/bin/sh
#DAEMON_USER DIVERT_PORT ONLY_PORTS OMIT_PORTS

# determine which operation is requested (Append or Delete)
if [ "$1" = "start" -o -z "$1" ]; then
    # during startup, bail early if any of these commands fails
    set -e
    OP="-A"
elif [ "$1" = "stop" -o "$1" = "-f" ] ; then
    OP="-D"
else
    echo "Expected \"start\" or \"stop\" as first argument" >&2
    exit 1
fi

# determine which ports should be tcpcrypt-enabled
if [ -z "$ONLY_PORTS" -a -z "$OMIT_PORTS" ] ; then
    echo "Expected either OMIT_PORTS or ONLY_PORTS environment variables to be set" >&2
    exit 1
fi
if [ -n "$ONLY_PORTS" -a -n "$OMIT_PORTS" ] ; then
    echo "Expected only one of OMIT_PORTS or ONLY_PORTS environment variables to be set" >&2
    exit 1
fi
if [ -n "$OMIT_PORTS" ] ; then
    PORT_TEST=!
    PORTS="$OMIT_PORTS"
fi
if [ -n "$ONLY_PORTS" ] ; then
    PORT_TEST=
    PORTS="$ONLY_PORTS"
fi

# more necessary configuration
if [ -z "$DAEMON_USER" ] ; then
    echo "Expected DAEMON_USER environment variable to be set" >&2
    exit 1
fi
if [ -z "$DIVERT_PORT" ] ; then
    echo "Expected DIVERT_PORT environment variable to be set" >&2
    exit 1
fi

# some shorthand to make rules more concise
from_enabled_port="-m multiport $PORT_TEST --source-ports $PORTS"
to_enabled_port="-m multiport $PORT_TEST --destination-ports $PORTS"
NFQUEUE="NFQUEUE --queue-num $DIVERT_PORT"
CRYPT_PORT="65530"
REDIRECT="REDIRECT --to-port $CRYPT_PORT"
INJECT_TOS="0x22"
HANDSHAKE_TOS="0x04"

filter="$ECHO iptables -t filter $OP"

# Injection from daemon: Accept
$filter INPUT -i lo -p tcp --dport $CRYPT_PORT \
          -m tos --tos $INJECT_TOS \
  -j ACCEPT

# SYN redirected to daemon:
#   Queue for daemon to initiate proxy connection with original destination
$filter INPUT -p tcp --dport $CRYPT_PORT --tcp-flags ALL SYN \
  -j $NFQUEUE

# SYN+ACK on proxy connection:
#   Queue for daemon to complete original handshake
$filter INPUT -p tcp $from_enabled_port --tcp-flags ALL SYN,ACK \
  -j $NFQUEUE

# Handshake packet of proxy connection from daemon:
#   Queue for daemon to set tcp options via DIVERT_MODIFY
$filter OUTPUT -p tcp $to_enabled_port \
           -m tos --tos $HANDSHAKE_TOS \
           -m owner --uid-owner $DAEMON_USER \
  -j $NFQUEUE

# SYN+ACK on redirected connection:
#   Queue for daemon to delay handshake until proxy connection succeeds
$filter OUTPUT -p tcp --sport $CRYPT_PORT --tcp-flags ALL SYN,ACK \
  -j $NFQUEUE


nat="$ECHO iptables -t nat $OP"

# Inbound connection for enabled ports:
#   Redirect to daemon (at localhost:$CRYPT_PORT) for encryption
#
# (The nat module will now translate addresses in both directions,
#  for the lifetime of this connection.)
$nat PREROUTING -p tcp $to_enabled_port \
  -j $REDIRECT


# Proxy connection from daemon to enabled port: Accept
$nat OUTPUT -p tcp $to_enabled_port \
        -m owner --uid-owner $DAEMON_USER \
  -j ACCEPT

# Outbound connections to enabled ports on remote hosts:
#   Redirect to daemon (at localhost port $CRYPT_PORT) for encryption
#
# (The nat module will now translate addresses in both directions,
#  for the lifetime of this connection.)
$nat OUTPUT \! -o lo -p tcp $to_enabled_port \
  -j $REDIRECT


mangle="$ECHO iptables -t mangle $OP"

# Packets leaving the machine with bookkeeping mark: Remove mark
$mangle POSTROUTING -m tos --tos $HANDSHAKE_TOS \
  -j TOS --set-tos 0x00

Вопрос

Как я должен изменить iptables с текущим (см. выше), записи для достижения следующих ограничений:

  1. Только пакеты с определенным местом назначения должны быть поставлены в очередь для tcpcrypt.
  2. Все другие пакеты не должны быть поставлены в очередь для tcpcrypt и должны свободно перемещаться.

Что я попробовал

A) Я пытался добавить желаемый IP-адрес к tcp месту назначения в OUTPUT цепочка, которая похожа:

Chain OUTPUT (policy ACCEPT 4 packets, 536 bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 NFQUEUE    tcp  --  any    any     anywhere             XXX.XXX.XXX.XXX      multiport dports  !ssh,261,https,nntps,614,ldaps,684,695,ftps-data,ftps,telnets:pop3s tos match0x04/0xff owner UID match tcpcryptd NFQUEUE num 666
    0     0 NFQUEUE    tcp  --  any    any     anywhere             XXX.XXX.XXX.XXX      tcp spt:65530 flags:FIN,SYN,RST,PSH,ACK,URG/SYN,ACK NFQUEUE num 666

B) Я пытался добавить источник и целевые параметры к правилам NAT:

target     prot opt source               destination         
REDIRECT   tcp  --  XXX.XXX.XXX.XXX       XXX.XXX.XXX.XXX       multiport dports  !ssh,261,https,nntps,614,ldaps,684,695,ftps-data,ftps,telnets:pop3s redir ports 65530

Но все еще все пакеты независимо от адреса назначения, отправляются в tcpcrypt.

6
задан 27 November 2017 в 06:31

1 ответ

Найденный решением, рабочим на основе метода B):

Для входящих пакетов на nat таблица PREROUTING цепочка, я пытался отфильтровать как ниже

$nat PREROUTING -p tcp -s XXX.XXX.XXX.XXX $to_enabled_port \
    -j $REDIRECT

где -s значение опции и IP после -p tcp. Затем я изменил его на 

$nat PREROUTING -s XXX.XXX.XXX.XXX -p tcp $to_enabled_port \
    -j $REDIRECT

С этим изменением и изменением OUTPUT цепочка nat соответственно, желаемые результаты были достигнуты.

Интересно, вывод iptables -t nat --line-numbers -L -nv взгляды точно то же для любой из вышеупомянутых команд. Однако, только второй урожай заканчивается согласно моим ограничениям.

Вот измененная версия iptables.sh который позволяет указывать один или несколько дюйм/с для ограничения tcpcrypt.

Посмотрите FILTER_IP ниже.

#!/bin/sh
#DAEMON_USER DIVERT_PORT ONLY_PORTS OMIT_PORTS

# determine which operation is requested (Append or Delete)
if [ "$1" = "start" -o -z "$1" ]; then
    # during startup, bail early if any of these commands fails
    set -e
    OP="-A"
elif [ "$1" = "stop" -o "$1" = "-f" ] ; then
    OP="-D"
else
    echo "Expected \"start\" or \"stop\" as first argument" >&2
    exit 1
fi

# determine which ports should be tcpcrypt-enabled
if [ -z "$ONLY_PORTS" -a -z "$OMIT_PORTS" ] ; then
    echo "Expected either OMIT_PORTS or ONLY_PORTS environment variables to be set" >&2
    exit 1
fi
if [ -n "$ONLY_PORTS" -a -n "$OMIT_PORTS" ] ; then
    echo "Expected only one of OMIT_PORTS or ONLY_PORTS environment variables to be set" >&2
    exit 1
fi
if [ -n "$OMIT_PORTS" ] ; then
    PORT_TEST=!
    PORTS="$OMIT_PORTS"
fi
if [ -n "$ONLY_PORTS" ] ; then
    PORT_TEST=
    PORTS="$ONLY_PORTS"
fi

# more necessary configuration
if [ -z "$DAEMON_USER" ] ; then
    echo "Expected DAEMON_USER environment variable to be set" >&2
    exit 1
fi
if [ -z "$DIVERT_PORT" ] ; then
    echo "Expected DIVERT_PORT environment variable to be set" >&2
    exit 1
fi

# some shorthand to make rules more concise
from_enabled_port="-m multiport $PORT_TEST --source-ports $PORTS"
to_enabled_port="-m multiport $PORT_TEST --destination-ports $PORTS"
NFQUEUE="NFQUEUE --queue-num $DIVERT_PORT"
CRYPT_PORT="65530"
REDIRECT="REDIRECT --to-port $CRYPT_PORT"
INJECT_TOS="0x22"
HANDSHAKE_TOS="0x04"

# You can specify multiple IPs, or a IP range accrding to required format
# For example, restricting tcpcrypt to 192.192.192.192 and 127.127.127.127
# FILTER_IP="192.192.192.192,127.127.127.127"
# See iptables manpage for more info
FILTER_IP="XXX.XXX.XXX.XXX"

filter="$ECHO iptables -t filter $OP"

# Injection from daemon: Accept
$filter INPUT -i lo -p tcp --dport $CRYPT_PORT \
          -m tos --tos $INJECT_TOS \
  -j ACCEPT

# SYN redirected to daemon:
#   Queue for daemon to initiate proxy connection with original destination
$filter INPUT -p tcp --dport $CRYPT_PORT --tcp-flags ALL SYN \
  -j $NFQUEUE

# SYN+ACK on proxy connection:
#   Queue for daemon to complete original handshake
$filter INPUT -p tcp $from_enabled_port --tcp-flags ALL SYN,ACK \
  -j $NFQUEUE

# Handshake packet of proxy connection from daemon:
#   Queue for daemon to set tcp options via DIVERT_MODIFY
$filter OUTPUT -p tcp $to_enabled_port \
           -m tos --tos $HANDSHAKE_TOS \
           -m owner --uid-owner $DAEMON_USER \
  -j $NFQUEUE

# SYN+ACK on redirected connection:
#   Queue for daemon to delay handshake until proxy connection succeeds
$filter OUTPUT -p tcp --sport $CRYPT_PORT --tcp-flags ALL SYN,ACK \
  -j $NFQUEUE


nat="$ECHO iptables -t nat $OP"

# Inbound connection for enabled ports:
#   Redirect to daemon (at localhost:$CRYPT_PORT) for encryption
#
# (The nat module will now translate addresses in both directions,
#  for the lifetime of this connection.)
$nat PREROUTING -s $FILTER_IP -p tcp $to_enabled_port \
  -j $REDIRECT


# Proxy connection from daemon to enabled port: Accept
$nat OUTPUT -p tcp $to_enabled_port \
        -m owner --uid-owner $DAEMON_USER \
  -j ACCEPT

# Outbound connections to enabled ports on remote hosts:
#   Redirect to daemon (at localhost port $CRYPT_PORT) for encryption
#
# (The nat module will now translate addresses in both directions,
#  for the lifetime of this connection.)
$nat OUTPUT -d $FILTER_IP \! -o lo -p tcp $to_enabled_port \
  -j $REDIRECT


mangle="$ECHO iptables -t mangle $OP"

# Packets leaving the machine with bookkeeping mark: Remove mark
$mangle POSTROUTING -m tos --tos $HANDSHAKE_TOS \
  -j TOS --set-tos 0x00
0
ответ дан 23 November 2019 в 08:18

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