scrapli.transport.plugins.ssh2.transport
Ssh2Transport
Bases: Transport
Source code in transport/plugins/ssh2/transport.py
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290 | 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)
known_host_public_key = known_hosts.lookup(self._base_transport_args.host)
if not known_host_public_key:
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_host_public_key["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
with suppress(AuthenticationError, SSH2Error):
self.session.userauth_publickey_fromfile(
self.plugin_transport_args.auth_username,
self.plugin_transport_args.auth_private_key.encode(),
self.plugin_transport_args.auth_private_key_passphrase,
)
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
with suppress(AuthenticationError):
self.session.userauth_password(
username=self.plugin_transport_args.auth_username,
password=self.plugin_transport_args.auth_password,
)
return
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)
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