Module scrapli.transport.plugins.ssh2.transport¶
scrapli.transport.plugins.ssh2.transport
Expand source code
"""scrapli.transport.plugins.ssh2.transport"""
import base64
from dataclasses import dataclass
from typing import Optional
from ssh2.channel import Channel
from ssh2.exceptions import AuthenticationError, SSH2Error
from ssh2.session import Session
from scrapli.exceptions import (
ScrapliAuthenticationFailed,
ScrapliConnectionError,
ScrapliConnectionNotOpened,
)
from scrapli.ssh_config import SSHKnownHosts
from scrapli.transport.base import BasePluginTransportArgs, BaseTransportArgs, Transport
from scrapli.transport.base.base_socket import Socket
@dataclass()
class PluginTransportArgs(BasePluginTransportArgs):
auth_username: str
auth_password: str = ""
auth_private_key: str = ""
auth_strict_key: bool = True
ssh_config_file: str = ""
ssh_known_hosts_file: str = ""
class Ssh2Transport(Transport):
def __init__(
self, base_transport_args: BaseTransportArgs, plugin_transport_args: PluginTransportArgs
) -> None:
super().__init__(base_transport_args=base_transport_args)
self.plugin_transport_args = plugin_transport_args
self.socket: Optional[Socket] = None
self.session: Optional[Session] = None
self.session_channel: Optional[Channel] = None
def open(self) -> None:
self._pre_open_closing_log(closing=False)
if not self.socket:
self.socket = Socket(
host=self._base_transport_args.host,
port=self._base_transport_args.port,
timeout=self._base_transport_args.timeout_socket,
)
if not self.socket.isalive():
self.socket.open()
self.session = Session()
self._set_timeout(value=self._base_transport_args.timeout_transport)
try:
self.session.handshake(self.socket.sock)
except Exception as exc:
self.logger.critical("failed to complete handshake with host")
raise ScrapliConnectionNotOpened from exc
if self.plugin_transport_args.auth_strict_key:
self.logger.debug(f"attempting to validate {self._base_transport_args.host} public key")
self._verify_key()
self._authenticate()
if not self.session.userauth_authenticated():
msg = "all authentication methods failed"
self.logger.critical(msg)
raise ScrapliAuthenticationFailed(msg)
self._open_channel()
self._post_open_closing_log(closing=False)
def _verify_key(self) -> None:
"""
Verify target host public key, raise exception if invalid/unknown
Args:
N/A
Returns:
None
Raises:
ScrapliConnectionNotOpened: if session is unopened/None
ScrapliAuthenticationFailed: if public key verification fails
"""
if not self.session:
raise ScrapliConnectionNotOpened
known_hosts = SSHKnownHosts(self.plugin_transport_args.ssh_known_hosts_file)
if self._base_transport_args.host not in known_hosts.hosts.keys():
raise ScrapliAuthenticationFailed(
f"{self._base_transport_args.host} not in known_hosts!"
)
remote_server_key_info = self.session.hostkey()
encoded_remote_server_key = remote_server_key_info[0]
raw_remote_public_key = base64.encodebytes(encoded_remote_server_key)
remote_public_key = raw_remote_public_key.replace(b"\n", b"").decode()
if known_hosts.hosts[self._base_transport_args.host]["public_key"] != remote_public_key:
raise ScrapliAuthenticationFailed(
f"{self._base_transport_args.host} in known_hosts but public key does not match!"
)
def _authenticate(self) -> None:
"""
Parent method to try all means of authentication
Args:
N/A
Returns:
None
Raises:
ScrapliConnectionNotOpened: if session is unopened/None
ScrapliAuthenticationFailed: if auth fails
"""
if not self.session:
raise ScrapliConnectionNotOpened
if self.plugin_transport_args.auth_private_key:
self._authenticate_public_key()
if self.session.userauth_authenticated():
return
if (
not self.plugin_transport_args.auth_password
or not self.plugin_transport_args.auth_username
):
msg = (
f"Failed to authenticate to host {self._base_transport_args.host} with private "
f"key `{self.plugin_transport_args.auth_private_key}`. Unable to continue "
"authentication, missing username, password, or both."
)
raise ScrapliAuthenticationFailed(msg)
self._authenticate_password()
def _authenticate_public_key(self) -> None:
"""
Attempt to authenticate with public key authentication
Args:
N/A
Returns:
None
Raises:
ScrapliConnectionNotOpened: if session is unopened/None
"""
if not self.session:
raise ScrapliConnectionNotOpened
try:
self.session.userauth_publickey_fromfile(
self.plugin_transport_args.auth_username,
self.plugin_transport_args.auth_private_key.encode(),
)
except (AuthenticationError, SSH2Error):
pass
def _authenticate_password(self) -> None:
"""
Attempt to authenticate with password authentication
Args:
N/A
Returns:
None
Raises:
ScrapliConnectionNotOpened: if session is unopened/None
"""
if not self.session:
raise ScrapliConnectionNotOpened
try:
self.session.userauth_password(
username=self.plugin_transport_args.auth_username,
password=self.plugin_transport_args.auth_password,
)
return
except AuthenticationError:
pass
try:
self.session.userauth_keyboardinteractive(
self.plugin_transport_args.auth_username, self.plugin_transport_args.auth_password
)
except AttributeError:
msg = (
"Keyboard interactive authentication may not be supported in your "
"ssh2-python version."
)
self.logger.warning(msg)
except AuthenticationError:
pass
def _open_channel(self) -> None:
"""
Open channel, acquire pty, request interactive shell
Args:
N/A
Returns:
None
Raises:
ScrapliConnectionNotOpened: if session is unopened/None
"""
if not self.session:
raise ScrapliConnectionNotOpened
self.session_channel = self.session.open_session()
self.session_channel.pty()
self.session_channel.shell()
def close(self) -> None:
self._pre_open_closing_log(closing=True)
if self.session_channel:
self.session_channel.close()
if self.socket:
self.socket.close()
self.session = None
self.session_channel = None
self._post_open_closing_log(closing=True)
def isalive(self) -> bool:
if not self.session_channel:
return False
return not self.session_channel.eof()
def read(self) -> bytes:
if not self.session_channel:
raise ScrapliConnectionNotOpened
try:
buf: bytes
_, buf = self.session_channel.read(65535)
except Exception as exc:
msg = (
"encountered EOF reading from transport; typically means the device closed the "
"connection"
)
self.logger.critical(msg)
raise ScrapliConnectionError(msg) from exc
return buf
def write(self, channel_input: bytes) -> None:
if not self.session_channel:
raise ScrapliConnectionNotOpened
self.session_channel.write(channel_input)
def _set_timeout(self, value: float) -> None:
"""
Set session object timeout value
Args:
value: timeout in seconds
Returns:
None
Raises:
ScrapliConnectionNotOpened: if session is unopened/None
"""
if not self.session:
raise ScrapliConnectionNotOpened
# ssh2-python expects timeout in milliseconds
self.session.set_timeout(value * 1000)
Classes¶
PluginTransportArgs¶
1 | |
Expand source code
class PluginTransportArgs(BasePluginTransportArgs):
auth_username: str
auth_password: str = ""
auth_private_key: str = ""
auth_strict_key: bool = True
ssh_config_file: str = ""
ssh_known_hosts_file: str = ""
Ancestors (in MRO)¶
- scrapli.transport.base.base_transport.BasePluginTransportArgs
Class variables¶
auth_password: str
auth_private_key: str
auth_strict_key: bool
auth_username: str
ssh_config_file: str
ssh_known_hosts_file: str
Ssh2Transport¶
1 2 | |
Expand source code
class Ssh2Transport(Transport):
def __init__(
self, base_transport_args: BaseTransportArgs, plugin_transport_args: PluginTransportArgs
) -> None:
super().__init__(base_transport_args=base_transport_args)
self.plugin_transport_args = plugin_transport_args
self.socket: Optional[Socket] = None
self.session: Optional[Session] = None
self.session_channel: Optional[Channel] = None
def open(self) -> None:
self._pre_open_closing_log(closing=False)
if not self.socket:
self.socket = Socket(
host=self._base_transport_args.host,
port=self._base_transport_args.port,
timeout=self._base_transport_args.timeout_socket,
)
if not self.socket.isalive():
self.socket.open()
self.session = Session()
self._set_timeout(value=self._base_transport_args.timeout_transport)
try:
self.session.handshake(self.socket.sock)
except Exception as exc:
self.logger.critical("failed to complete handshake with host")
raise ScrapliConnectionNotOpened from exc
if self.plugin_transport_args.auth_strict_key:
self.logger.debug(f"attempting to validate {self._base_transport_args.host} public key")
self._verify_key()
self._authenticate()
if not self.session.userauth_authenticated():
msg = "all authentication methods failed"
self.logger.critical(msg)
raise ScrapliAuthenticationFailed(msg)
self._open_channel()
self._post_open_closing_log(closing=False)
def _verify_key(self) -> None:
"""
Verify target host public key, raise exception if invalid/unknown
Args:
N/A
Returns:
None
Raises:
ScrapliConnectionNotOpened: if session is unopened/None
ScrapliAuthenticationFailed: if public key verification fails
"""
if not self.session:
raise ScrapliConnectionNotOpened
known_hosts = SSHKnownHosts(self.plugin_transport_args.ssh_known_hosts_file)
if self._base_transport_args.host not in known_hosts.hosts.keys():
raise ScrapliAuthenticationFailed(
f"{self._base_transport_args.host} not in known_hosts!"
)
remote_server_key_info = self.session.hostkey()
encoded_remote_server_key = remote_server_key_info[0]
raw_remote_public_key = base64.encodebytes(encoded_remote_server_key)
remote_public_key = raw_remote_public_key.replace(b"\n", b"").decode()
if known_hosts.hosts[self._base_transport_args.host]["public_key"] != remote_public_key:
raise ScrapliAuthenticationFailed(
f"{self._base_transport_args.host} in known_hosts but public key does not match!"
)
def _authenticate(self) -> None:
"""
Parent method to try all means of authentication
Args:
N/A
Returns:
None
Raises:
ScrapliConnectionNotOpened: if session is unopened/None
ScrapliAuthenticationFailed: if auth fails
"""
if not self.session:
raise ScrapliConnectionNotOpened
if self.plugin_transport_args.auth_private_key:
self._authenticate_public_key()
if self.session.userauth_authenticated():
return
if (
not self.plugin_transport_args.auth_password
or not self.plugin_transport_args.auth_username
):
msg = (
f"Failed to authenticate to host {self._base_transport_args.host} with private "
f"key `{self.plugin_transport_args.auth_private_key}`. Unable to continue "
"authentication, missing username, password, or both."
)
raise ScrapliAuthenticationFailed(msg)
self._authenticate_password()
def _authenticate_public_key(self) -> None:
"""
Attempt to authenticate with public key authentication
Args:
N/A
Returns:
None
Raises:
ScrapliConnectionNotOpened: if session is unopened/None
"""
if not self.session:
raise ScrapliConnectionNotOpened
try:
self.session.userauth_publickey_fromfile(
self.plugin_transport_args.auth_username,
self.plugin_transport_args.auth_private_key.encode(),
)
except (AuthenticationError, SSH2Error):
pass
def _authenticate_password(self) -> None:
"""
Attempt to authenticate with password authentication
Args:
N/A
Returns:
None
Raises:
ScrapliConnectionNotOpened: if session is unopened/None
"""
if not self.session:
raise ScrapliConnectionNotOpened
try:
self.session.userauth_password(
username=self.plugin_transport_args.auth_username,
password=self.plugin_transport_args.auth_password,
)
return
except AuthenticationError:
pass
try:
self.session.userauth_keyboardinteractive(
self.plugin_transport_args.auth_username, self.plugin_transport_args.auth_password
)
except AttributeError:
msg = (
"Keyboard interactive authentication may not be supported in your "
"ssh2-python version."
)
self.logger.warning(msg)
except AuthenticationError:
pass
def _open_channel(self) -> None:
"""
Open channel, acquire pty, request interactive shell
Args:
N/A
Returns:
None
Raises:
ScrapliConnectionNotOpened: if session is unopened/None
"""
if not self.session:
raise ScrapliConnectionNotOpened
self.session_channel = self.session.open_session()
self.session_channel.pty()
self.session_channel.shell()
def close(self) -> None:
self._pre_open_closing_log(closing=True)
if self.session_channel:
self.session_channel.close()
if self.socket:
self.socket.close()
self.session = None
self.session_channel = None
self._post_open_closing_log(closing=True)
def isalive(self) -> bool:
if not self.session_channel:
return False
return not self.session_channel.eof()
def read(self) -> bytes:
if not self.session_channel:
raise ScrapliConnectionNotOpened
try:
buf: bytes
_, buf = self.session_channel.read(65535)
except Exception as exc:
msg = (
"encountered EOF reading from transport; typically means the device closed the "
"connection"
)
self.logger.critical(msg)
raise ScrapliConnectionError(msg) from exc
return buf
def write(self, channel_input: bytes) -> None:
if not self.session_channel:
raise ScrapliConnectionNotOpened
self.session_channel.write(channel_input)
def _set_timeout(self, value: float) -> None:
"""
Set session object timeout value
Args:
value: timeout in seconds
Returns:
None
Raises:
ScrapliConnectionNotOpened: if session is unopened/None
"""
if not self.session:
raise ScrapliConnectionNotOpened
# ssh2-python expects timeout in milliseconds
self.session.set_timeout(value * 1000)
Ancestors (in MRO)¶
- scrapli.transport.base.sync_transport.Transport
- scrapli.transport.base.base_transport.BaseTransport
- abc.ABC