kitty/kittens/ssh/main.py

#!/usr/bin/env python3
# vim:fileencoding=utf-8
# License: GPL v3 Copyright: 2018, Kovid Goyal <kovid at kovidgoyal.net>

import os
import re
import shlex
import subprocess
import sys
from contextlib import suppress
from typing import List, NoReturn, Optional, Set, Tuple

from kitty.utils import SSHConnectionData

SHELL_SCRIPT = '''\
#!/bin/sh
# macOS ships with an ancient version of tic that cannot read from stdin, so we
# create a temp file for it
tmp=$(mktemp)
cat >$tmp << 'TERMEOF'
TERMINFO
TERMEOF

tic_out=$(tic -x -o ~/.terminfo $tmp 2>&1)
rc=$?
rm $tmp
if [ "$rc" != "0" ]; then echo "$tic_out"; exit 1; fi
if [ -z "$USER" ]; then export USER=$(whoami); fi
EXEC_CMD
shell_name=$(basename $0)

# We need to pass the first argument to the executed program with a leading -
# to make sure the shell executes as a login shell. Note that not all shells
# support exec -a so we use the below to try to detect such shells

case "dash" in
    *$shell_name*)
        python=$(command -v python3)
        if [ -z "$python" ]; then python=$(command -v python2); fi
        if [ -z "$python" ]; then python=python; fi
        exec $python -c "import os; os.execlp('$0', '-' '$shell_name')"
    ;;
esac

exec -a "-$shell_name" "$0"
'''


PYTHON_SCRIPT = '''\
#!/usr/bin/env python
from __future__ import print_function
from tempfile import NamedTemporaryFile
import subprocess, os, sys, pwd, binascii, json

# macOS ships with an ancient version of tic that cannot read from stdin, so we
# create a temp file for it
with NamedTemporaryFile() as tmp:
    tmp.write(binascii.unhexlify('{terminfo}'))
    p = subprocess.Popen(['tic', '-x', '-o', os.path.expanduser('~/.terminfo'), tmp.name], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    stdout, stderr = p.communicate()
    if p.wait() != 0:
        getattr(sys.stderr, 'buffer', sys.stderr).write(stdout + stderr)
        raise SystemExit('Failed to compile terminfo using tic')
command_to_execute = json.loads(binascii.unhexlify('{command_to_execute}'))
if command_to_execute:
    os.execlp(command_to_execute[0], *command_to_execute)
try:
    shell_path = pwd.getpwuid(os.geteuid()).pw_shell or '/bin/sh'
except KeyError:
    shell_path = '/bin/sh'
shell_name = '-' + os.path.basename(shell_path)
os.execlp(shell_path, shell_name)
'''


def get_ssh_cli() -> Tuple[Set[str], Set[str]]:
    other_ssh_args: List[str] = []
    boolean_ssh_args: List[str] = []
    stderr = subprocess.Popen(['ssh'], stderr=subprocess.PIPE).stderr
    assert stderr is not None
    raw = stderr.read().decode('utf-8')
    for m in re.finditer(r'\[(.+?)\]', raw):
        q = m.group(1)
        if len(q) < 2 or q[0] != '-':
            continue
        if ' ' in q:
            other_ssh_args.append(q[1])
        else:
            boolean_ssh_args.extend(q[1:])
    return set('-' + x for x in boolean_ssh_args), set('-' + x for x in other_ssh_args)


def get_connection_data(args: List[str]) -> Optional[SSHConnectionData]:
    boolean_ssh_args, other_ssh_args = get_ssh_cli()
    found_ssh = ''
    port: Optional[int] = None
    expecting_port = False
    expecting_option_val = False

    for i, arg in enumerate(args):
        if not found_ssh:
            if os.path.basename(arg).lower() in ('ssh', 'ssh.exe'):
                found_ssh = arg
            continue
        if arg.startswith('-') and not expecting_option_val:
            if arg in boolean_ssh_args:
                continue
            if arg.startswith('-p'):
                if arg[2:].isdigit():
                    with suppress(Exception):
                        port = int(arg[2:])
                elif arg == '-p':
                    expecting_port = True
            expecting_option_val = True
            continue

        if expecting_option_val:
            if expecting_port:
                with suppress(Exception):
                    port = int(arg)
                expecting_port = False
            expecting_option_val = False
            continue

        return SSHConnectionData(found_ssh, arg, port)


def parse_ssh_args(args: List[str]) -> Tuple[List[str], List[str], bool]:
    boolean_ssh_args, other_ssh_args = get_ssh_cli()
    passthrough_args = {'-' + x for x in 'Nnf'}
    ssh_args = []
    server_args: List[str] = []
    expecting_option_val = False
    passthrough = False
    for arg in args:
        if len(server_args) > 1:
            server_args.append(arg)
            continue
        if arg.startswith('-') and not expecting_option_val:
            all_args = arg[1:]
            for i, arg in enumerate(all_args):
                arg = '-' + arg
                if arg in passthrough_args:
                    passthrough = True
                if arg in boolean_ssh_args:
                    ssh_args.append(arg)
                    continue
                if arg in other_ssh_args:
                    ssh_args.append(arg)
                    rest = all_args[i+1:]
                    if rest:
                        ssh_args.append(rest)
                    else:
                        expecting_option_val = True
                    break
                raise SystemExit('Unknown option: {}'.format(arg))
            continue
        if expecting_option_val:
            ssh_args.append(arg)
            expecting_option_val = False
            continue
        server_args.append(arg)
    if not server_args:
        raise SystemExit('Must specify server to connect to')
    return ssh_args, server_args, passthrough


def quote(x: str) -> str:
    # we have to escape unbalanced quotes and other unparsable
    # args as they will break the shell script
    # But we do not want to quote things like * or 'echo hello'
    # See https://github.com/kovidgoyal/kitty/issues/1787
    try:
        shlex.split(x)
    except ValueError:
        x = shlex.quote(x)
    return x


def get_posix_cmd(terminfo: str, remote_args: List[str]) -> List[str]:
    sh_script = SHELL_SCRIPT.replace('TERMINFO', terminfo, 1)
    if remote_args:
        command_to_executeg = (quote(c) for c in remote_args)
        command_to_execute = 'exec ' + ' '.join(command_to_executeg)
    else:
        command_to_execute = ''
    sh_script = sh_script.replace('EXEC_CMD', command_to_execute)
    return [sh_script] + remote_args


def get_python_cmd(terminfo: str, command_to_execute: List[str]) -> List[str]:
    import json
    script = PYTHON_SCRIPT.format(
        terminfo=terminfo.encode('utf-8').hex(),
        command_to_execute=json.dumps(command_to_execute).encode('utf-8').hex()
    )
    return [f'python -c "{script}"']


def main(args: List[str]) -> NoReturn:
    args = args[1:]
    use_posix = True
    if args and args[0] == 'use-python':
        args = args[1:]
        use_posix = False
    ssh_args, server_args, passthrough = parse_ssh_args(args)
    cmd = ['ssh'] + ssh_args
    if passthrough:
        cmd += server_args
    else:
        hostname, remote_args = server_args[0], server_args[1:]
        cmd += ['-t', hostname]
        terminfo = subprocess.check_output(['infocmp']).decode('utf-8')
        f = get_posix_cmd if use_posix else get_python_cmd
        cmd += f(terminfo, remote_args)
    os.execvp('ssh', cmd)


if __name__ == '__main__':
    main(sys.argv)