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Improve error message if tproxy method is used without running as root.

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When the tproxy method is used, sshuttle must be run as root:
https://sshuttle.readthedocs.io/en/stable/tproxy.html

Prior to this patch, sshuttle would encounter a exception and print a
message about how a setsockopt() call had a "PermissionError: [Errno 1]
Operation not permitted."

With this patch, we catch this exception, print a more understandable
error message, and exit.

The lack of error message clarity caused at least one bug report: #136
This commit is contained in:
Scott Kuhl 2022-01-04 14:39:15 -05:00
parent ae1faa7fa1
commit 15a8752cc6
1 changed files with 23 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
sshuttle/methods/tproxy.py
View File

@ -6,6 +6,7 @@ from sshuttle.methods import BaseMethod
from sshuttle.helpers import debug1, debug2, debug3, Fatal, which
import socket
import os
IP_TRANSPARENT = 19
@ -69,6 +70,15 @@ class Method(BaseMethod):
return None
return srcip, dstip, data
def setsockopt_error(self, e):
"""The tproxy method needs root permissions to successfully
set the IP_TRANSPARENT option on sockets. This method is
called when we receive a PermissionError when trying to do
so."""
raise Fatal("Insufficient permissions for tproxy method.\n"
"Your effective UID is %d, not 0. Try rerunning as root.\n"
% os.geteuid())
def send_udp(self, sock, srcip, dstip, data):
if not srcip:
debug1(
@ -77,16 +87,26 @@ class Method(BaseMethod):
return
sender = socket.socket(sock.family, socket.SOCK_DGRAM)
sender.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sender.setsockopt(socket.SOL_IP, IP_TRANSPARENT, 1)
try:
sender.setsockopt(socket.SOL_IP, IP_TRANSPARENT, 1)
except PermissionError as e:
self.setsockopt_error(e)
sender.bind(srcip)
sender.sendto(data, dstip)
sender.close()
def setup_tcp_listener(self, tcp_listener):
tcp_listener.setsockopt(socket.SOL_IP, IP_TRANSPARENT, 1)
try:
tcp_listener.setsockopt(socket.SOL_IP, IP_TRANSPARENT, 1)
except PermissionError as e:
self.setsockopt_error(e)
def setup_udp_listener(self, udp_listener):
udp_listener.setsockopt(socket.SOL_IP, IP_TRANSPARENT, 1)
try:
udp_listener.setsockopt(socket.SOL_IP, IP_TRANSPARENT, 1)
except PermissionError as e:
self.setsockopt_error(e)
if udp_listener.v4 is not None:
udp_listener.v4.setsockopt(
socket.SOL_IP, IP_RECVORIGDSTADDR, 1)