Usernames with colons are wrongly parsed

Hello,

When I use a username with colon like 'proxyuser:target' the username is converted to proxyuser, preventing me to connect to the proxy.

# sshuttle -r proxyuser:target@10.4.42.52:2222 10.254.0.0/24 -vv
Starting sshuttle proxy (version 1.2.0).
c : Starting firewall manager with command: ['/usr/local/bin/sshuttle', '-v', '-v', '--method', 'auto', '--firewall']
fw: Starting firewall with Python version 3.9.2
fw: which() found 'iptables' at /usr/sbin/iptables
fw: which() found 'iptables' at /usr/sbin/iptables
fw: ready method name nat.
c : Using default IPv4 listen address 127.0.0.1
c : IPv6 enabled: Using default IPv6 listen address ::1
c : Method: nat
c : IPv4: on
c : IPv6: on
c : UDP : off (not available with nat method)
c : DNS : off (available)
c : User: off (available)
c : Subnets to forward through remote host (type, IP, cidr mask width, startPort, endPort):
c :   (<AddressFamily.AF_INET: 2>, '10.254.0.0', 24, 0, 0)
c : Subnets to exclude from forwarding:
c :   (<AddressFamily.AF_INET: 2>, '127.0.0.1', 32, 0, 0)
c :   (<AddressFamily.AF_INET6: 10>, '::1', 128, 0, 0)
c : Trying to bind redirector on port 12300
c : TCP redirector listening on ('::1', 12300, 0, 0).
c : TCP redirector listening with <socket.socket fd=5, family=AddressFamily.AF_INET6, type=SocketKind.SOCK_STREAM, proto=0, laddr=('::1', 12300, 0, 0)>.
c : TCP redirector listening on ('127.0.0.1', 12300).
c : TCP redirector listening with <socket.socket fd=7, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('127.0.0.1', 12300)>.
c : Starting client with Python version 3.9.2
c : Connecting to server...
c : which() found 'sshpass' at /usr/bin/sshpass
c : executing: ['/usr/bin/sshpass', '-e', 'ssh', '-p', '2222', 'proxyuser@10.4.42.52', '--', '/bin/sh -c \'P=python3; $P -V 2>/dev/null || P=python; exec "$P" -c \'"\'"\'import sys, os; verbosity=2; stdin = os.fdopen(0, \'"\'"\'"\'"\'"\'"\'"\'"\'rb\'"\'"\'"\'"\'"\'"\'"\'"\'); exec(compile(stdin.read(1785), \'"\'"\'"\'"\'"\'"\'"\'"\'assembler.py\'"\'"\'"\'"\'"\'"\'"\'"\', \'"\'"\'"\'"\'"\'"\'"\'"\'exec\'"\'"\'"\'"\'"\'"\'"\'"\')); sys.exit(98);\'"\'"\'; exit 97\'']
c :  > channel=0 cmd=PING len=7 (fullness=0)
proxyuser@10.4.42.52: Permission denied (publickey,keyboard-interactive).
c : fatal: failed to establish ssh session (2)

The ssh command should be ssh -p 2222 proxyuser:target@10.4.42.52 instead of ssh -p 2222 proxyuser@10.4.42.52

Is it possible to fix this? How could I help?

Thank you very much!

Start with sshuttle's command-line handling of the -r remote specification and trace how the username and host are passed to SSH. Reproduce the reported command, then add coverage for a colon-containing username. Done means the generated SSH command preserves proxyuser:target before the @ and the connection uses that complete username.