ssh-audit/src/ssh_audit/ssh2_kex.py

"""
   The MIT License (MIT)

   Copyright (C) 2017-2024 Joe Testa (jtesta@positronsecurity.com)
   Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)

   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files (the "Software"), to deal
   in the Software without restriction, including without limitation the rights
   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   copies of the Software, and to permit persons to whom the Software is
   furnished to do so, subject to the following conditions:

   The above copyright notice and this permission notice shall be included in
   all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   THE SOFTWARE.
"""
from typing import Dict, List
from typing import Union

from ssh_audit.outputbuffer import OutputBuffer
from ssh_audit.readbuf import ReadBuf
from ssh_audit.ssh2_kexparty import SSH2_KexParty
from ssh_audit.writebuf import WriteBuf


class SSH2_Kex:
    def __init__(self, outputbuffer: 'OutputBuffer', cookie: bytes, kex_algs: List[str], key_algs: List[str], cli: 'SSH2_KexParty', srv: 'SSH2_KexParty', follows: bool, unused: int = 0) -> None:  # pylint: disable=too-many-arguments
        self.__outputbuffer = outputbuffer
        self.__cookie = cookie
        self.__kex_algs = kex_algs
        self.__key_algs = key_algs
        self.__client = cli
        self.__server = srv
        self.__follows = follows
        self.__unused = unused

        self.__dh_modulus_sizes: Dict[str, int] = {}
        self.__host_keys: Dict[str, Dict[str, Union[bytes, str, int]]] = {}

    @property
    def cookie(self) -> bytes:
        return self.__cookie

    @property
    def kex_algorithms(self) -> List[str]:
        return self.__kex_algs

    @property
    def key_algorithms(self) -> List[str]:
        return self.__key_algs

    # client_to_server
    @property
    def client(self) -> 'SSH2_KexParty':
        return self.__client

    # server_to_client
    @property
    def server(self) -> 'SSH2_KexParty':
        return self.__server

    @property
    def follows(self) -> bool:
        return self.__follows

    @property
    def unused(self) -> int:
        return self.__unused

    def set_dh_modulus_size(self, gex_alg: str, modulus_size: int) -> None:
        self.__dh_modulus_sizes[gex_alg] = modulus_size

    def dh_modulus_sizes(self) -> Dict[str, int]:
        return self.__dh_modulus_sizes

    def set_host_key(self, key_type: str, raw_hostkey_bytes: bytes, hostkey_size: int, ca_key_type: str, ca_key_size: int) -> None:

        if key_type not in self.__host_keys:
            self.__host_keys[key_type] = {'raw_hostkey_bytes': raw_hostkey_bytes, 'hostkey_size': hostkey_size, 'ca_key_type': ca_key_type, 'ca_key_size': ca_key_size}
        else:  # A host key may only have one CA signature...
            self.__outputbuffer.d("WARNING: called SSH2_Kex.set_host_key() multiple times with the same host key type (%s)!  Existing info: %r, %r, %r; Duplicate (ignored) info: %r, %r, %r" % (key_type, self.__host_keys[key_type]['hostkey_size'], self.__host_keys[key_type]['ca_key_type'], self.__host_keys[key_type]['ca_key_size'], hostkey_size, ca_key_type, ca_key_size))

    def host_keys(self) -> Dict[str, Dict[str, Union[bytes, str, int]]]:
        return self.__host_keys

    def write(self, wbuf: 'WriteBuf') -> None:
        wbuf.write(self.cookie)
        wbuf.write_list(self.kex_algorithms)
        wbuf.write_list(self.key_algorithms)
        wbuf.write_list(self.client.encryption)
        wbuf.write_list(self.server.encryption)
        wbuf.write_list(self.client.mac)
        wbuf.write_list(self.server.mac)
        wbuf.write_list(self.client.compression)
        wbuf.write_list(self.server.compression)
        wbuf.write_list(self.client.languages)
        wbuf.write_list(self.server.languages)
        wbuf.write_bool(self.follows)
        wbuf.write_int(self.__unused)

    @property
    def payload(self) -> bytes:
        wbuf = WriteBuf()
        self.write(wbuf)
        return wbuf.write_flush()

    @classmethod
    def parse(cls, outputbuffer: 'OutputBuffer', payload: bytes) -> 'SSH2_Kex':
        buf = ReadBuf(payload)
        cookie = buf.read(16)
        kex_algs = buf.read_list()
        key_algs = buf.read_list()
        cli_enc = buf.read_list()
        srv_enc = buf.read_list()
        cli_mac = buf.read_list()
        srv_mac = buf.read_list()
        cli_compression = buf.read_list()
        srv_compression = buf.read_list()
        cli_languages = buf.read_list()
        srv_languages = buf.read_list()
        follows = buf.read_bool()
        unused = buf.read_int()
        cli = SSH2_KexParty(cli_enc, cli_mac, cli_compression, cli_languages)
        srv = SSH2_KexParty(srv_enc, srv_mac, srv_compression, srv_languages)
        kex = cls(outputbuffer, cookie, kex_algs, key_algs, cli, srv, follows, unused)
        return kex

    def __str__(self) -> str:
        ret = "----\nSSH2_Kex object:"
        ret += "\nHost keys: "
        ret += ", ".join(self.__key_algs)
        ret += "\nKey exchanges: "
        ret += ", ".join(self.__kex_algs)
        ret += "\nClient SSH2_KexParty:"
        ret += "\n" + str(self.__client)
        ret += "\nServer SSH2_KexParty:"
        ret += "\n" + str(self.__server)
        ret += "\n----"
        return ret