class documentation

class SSHClientTransport(SSHTransportBase): (source)

Known subclasses: twisted.conch.client.direct.SSHClientTransport, twisted.conch.scripts.tkconch.SSHClientTransport, twisted.conch.endpoints._CommandTransport

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SSHClientTransport implements the client side of the SSH protocol.
Method connectionMade Called when the connection is started with the server. Just sets up a private instance variable.
Method connectionSecure Called when the encryption has been set up. Generally, requestService() is called to run another service over the transport.
Method requestService Request that a service be run over this transport.
Method ssh_KEX_DH_GEX_GROUP This handles different messages which share an integer value.
Method ssh_KEX_DH_GEX_REPLY Called when we receive a MSG_KEX_DH_GEX_REPLY message. Payload:: string server host key integer f (server DH public key)
Method ssh_KEXINIT Called when we receive a MSG_KEXINIT message. For a description of the packet, see SSHTransportBase.ssh_KEXINIT(). Additionally, this method sends the first key exchange packet.
Method ssh_NEWKEYS Called when we receive a MSG_NEWKEYS message. No payload. If we've finished setting up our own keys, start using them. Otherwise, remember that we've received this message.
Method ssh_SERVICE_ACCEPT Called when we receive a MSG_SERVICE_ACCEPT message. Payload:: string service name
Method verifyHostKey Returns a Deferred that gets a callback if it is a valid key, or an errback if not.
Instance Variable e our Diffie-Hellman public key.
Instance Variable ecPriv Undocumented
Instance Variable ecPub Undocumented
Instance Variable g the Diffie-Hellman group generator.
Instance Variable instance the SSHService object we are requesting.
Instance Variable isClient since we are always the client, this is always True.
Instance Variable p the Diffie-Hellman group prime
Instance Variable x our Diffie-Hellman private key.
Method _continueGEX_REPLY The host key has been verified, so we generate the keys.
Method _continueKEXDH_REPLY The host key has been verified, so we generate the keys.
Method _keySetup See SSHTransportBase._keySetup().
Method _ssh_KEX_ECDH_REPLY Called to handle a reply to a ECDH exchange message(KEX_ECDH_INIT).
Method _ssh_KEXDH_REPLY Called to handle a reply to a non-group key exchange message (KEXDH_INIT).
Instance Variable _dhMaximalGroupSize Maximal acceptable group size advertised by the client in MSG_KEX_DH_GEX_REQUEST.
Instance Variable _dhMinimalGroupSize Minimal acceptable group size advertised by the client in MSG_KEX_DH_GEX_REQUEST.
Instance Variable _dhPreferredGroupSize Preferred group size advertised by the client in MSG_KEX_DH_GEX_REQUEST.
Instance Variable _gotNewKeys if we receive a MSG_NEWKEYS message before we are ready to transition to the new keys, this is set to True so we can transition when the keys are ready locally.

Inherited from SSHTransportBase:

Method connectionLost When the underlying connection is closed, stop the running service (if any), and log out the avatar (if any).
Method dataReceived First, check for the version string (SSH-2.0-*). After that has been received, this method adds data to the buffer, and pulls out any packets.
Method dispatchMessage Send a received message to the appropriate method.
Method getHost Returns an SSHTransportAddress corresponding to the this side of transport.
Method getPacket Try to return a decrypted, authenticated, and decompressed packet out of the buffer. If there is not enough data, return None.
Method getPeer Returns an SSHTransportAddress corresponding to the other (peer) side of this transport.
Method isEncrypted Check if the connection is encrypted in the given direction.
Method isVerified Check if the connection is verified/authentication in the given direction.
Method kexAlg.setter Set the key exchange algorithm name.
Method loseConnection Lose the connection to the other side, sending a DISCONNECT_CONNECTION_LOST message.
Method receiveDebug Called when we receive a debug message from the other side.
Method receiveError Called when we receive a disconnect error message from the other side.
Method receiveUnimplemented Called when we receive an unimplemented packet message from the other side.
Method sendDebug Send a debug message to the other side.
Method sendDisconnect Send a disconnect message to the other side and then disconnect.
Method sendExtInfo Send an RFC 8308 extension advertisement to the remote peer.
Method sendIgnore Send a message that will be ignored by the other side. This is useful to fool attacks based on guessing packet sizes in the encrypted stream.
Method sendKexInit Send a KEXINIT message to initiate key exchange or to respond to a key exchange initiated by the peer.
Method sendPacket Sends a packet. If it's been set up, compress the data, encrypt it, and authenticate it before sending. If key exchange is in progress and the message is not part of key exchange, queue it to be sent later.
Method sendUnimplemented Send a message to the other side that the last packet was not understood.
Method setService Set our service to service and start it running. If we were running a service previously, stop it first.
Method ssh_DEBUG No summary
Method ssh_DISCONNECT Called when we receive a MSG_DISCONNECT message. Payload:: long code string description
Method ssh_EXT_INFO No summary
Method ssh_IGNORE Called when we receive a MSG_IGNORE message. No payload. This means nothing; we simply return.
Method ssh_UNIMPLEMENTED Called when we receive a MSG_UNIMPLEMENTED message. Payload:: long packet
Instance Variable buf Data we've received but hasn't been parsed into a packet.
Instance Variable comment An optional string giving more information about the server or client.
Instance Variable currentEncryptions an SSHCiphers instance. It represents the current encryption and authentication options for the transport.
Instance Variable dhSecretKey Undocumented
Instance Variable dhSecretKeyPublicMP Undocumented
Instance Variable first the first bytes of the next packet. In order to avoid decrypting data twice, the first bytes are decrypted and stored until the whole packet is available.
Instance Variable gotVersion A boolean indicating whether we have received the version string from the other side.
Instance Variable incomingCompression an object supporting the .decompress(str) method, or None if there is no incoming compression. Used to decompress incoming data.
Instance Variable incomingCompressionType A string representing the incoming compression type.
Instance Variable incomingPacketSequence the sequence number of the next packet we are expecting from the other side.
Instance Variable kexAlg The key exchange algorithm name agreed between client and server.
Instance Variable keyAlg the agreed-upon public key type for the key exchange.
Instance Variable nextEncryptions an SSHCiphers instance. Held here until the MSG_NEWKEYS messages are exchanged, when nextEncryptions is transitioned to currentEncryptions.
Instance Variable otherKexInitPayload the MSG_KEXINIT payload we received. Used in the key exchange
Instance Variable otherVersionString the version string sent by the other side. Used in the key exchange.
Instance Variable ourKexInitPayload the MSG_KEXINIT payload we sent. Used in the key exchange.
Instance Variable ourVersionString the version string that we sent to the other side. Used in the key exchange.
Instance Variable outgoingCompression an object supporting the .compress(str) and .flush() methods, or None if there is no outgoing compression. Used to compress outgoing data.
Instance Variable outgoingCompressionType A string representing the outgoing compression type.
Instance Variable outgoingPacketSequence the sequence number of the next packet we will send.
Instance Variable peerExtensions a dict of extensions supported by the other side of the connection.
Instance Variable protocolVersion A string representing the version of the SSH protocol we support. Currently defaults to '2.0'.
Instance Variable service an SSHService instance, or None. If it's set to an object, it's the currently running service.
Instance Variable sessionID a string that is unique to this SSH session. Created as part of the key exchange, sessionID is used to generate the various encryption and authentication keys.
Instance Variable supportedCiphers A list of strings representing the encryption algorithms supported, in order from most-preferred to least.
Instance Variable supportedCompressions A list of strings representing compression types supported, from most-preferred to least.
Instance Variable supportedKeyExchanges A list of strings representing the key exchanges supported, in order from most-preferred to least.
Instance Variable supportedLanguages A list of strings representing languages supported, from most-preferred to least.
Instance Variable supportedMACs A list of strings representing the message authentication codes (hashes) supported, in order from most-preferred to least. Both this and supportedCiphers can include 'none' to use no encryption or authentication, but that must be done manually,
Instance Variable supportedPublicKeys A list of strings representing the public key types supported, in order from most-preferred to least.
Instance Variable supportedVersions A container of strings representing supported ssh protocol version numbers.
Instance Variable version A string representing the version of the server or client. Currently defaults to 'Twisted'.
Method _allowedKeyExchangeMessageType Determine if the given message type may be sent while key exchange is in progress.
Method _encodeECPublicKey Encode an elliptic curve public key to bytes.
Method _finishEphemeralDH Completes the Diffie-Hellman key agreement started by _startEphemeralDH, and forgets the ephemeral secret key.
Method _generateECPrivateKey Generate an private key for ECDH key exchange.
Method _generateECSharedSecret Generate a shared secret for ECDH key exchange.
Method _getKey Get one of the keys for authentication/encryption.
Method _newKeys No summary
Method _startEphemeralDH Prepares for a Diffie-Hellman key agreement exchange.
Method _unsupportedVersionReceived Called when an unsupported version of the ssh protocol is received from the remote endpoint.
Class Variable _EXT_INFO_C Undocumented
Class Variable _EXT_INFO_S Undocumented
Class Variable _KEY_EXCHANGE_NONE Undocumented
Class Variable _KEY_EXCHANGE_PROGRESSING Undocumented
Class Variable _KEY_EXCHANGE_REQUESTED Undocumented
Class Variable _log Undocumented
Instance Variable _blockedByKeyExchange Whenever _keyExchangeState is not _KEY_EXCHANGE_NONE, this is a list of pending messages which were passed to sendPacket but could not be sent because it is not legal to send them while a key exchange is in progress. When the key exchange completes, another attempt is made to send these messages.
Instance Variable _kexAlg Undocumented
Instance Variable _keyExchangeState The current protocol state with respect to key exchange. This is either _KEY_EXCHANGE_NONE if no key exchange is in progress (and returns to this value after any key exchange completqes), _KEY_EXCHANGE_REQUESTED if this side of the connection initiated a key exchange, and _KEY_EXCHANGE_PROGRESSING if the other side of the connection initiated a key exchange. _KEY_EXCHANGE_NONE is the initial value (however SSH connections begin with key exchange, so it will quickly change to another state).
Instance Variable _peerSupportsExtensions a boolean indicating whether the other side of the connection supports RFC 8308 extension negotiation.

Inherited from Protocol (via SSHTransportBase):

Method logPrefix Return a prefix matching the class name, to identify log messages related to this protocol instance.
Class Variable factory Undocumented

Inherited from BaseProtocol (via SSHTransportBase, Protocol):

Method makeConnection Make a connection to a transport and a server.
Instance Variable connected Undocumented
Instance Variable transport Undocumented
def connectionMade(self): (source)
Called when the connection is started with the server. Just sets up a private instance variable.
def connectionSecure(self): (source)
Called when the encryption has been set up. Generally, requestService() is called to run another service over the transport.
def requestService(self, instance): (source)
Request that a service be run over this transport.
Parameters
instance:subclass of twisted.conch.ssh.service.SSHServiceThe service to run.
def ssh_KEX_DH_GEX_GROUP(self, packet): (source)

This handles different messages which share an integer value.

If the key exchange does not have a fixed prime/generator group, we generate a Diffie-Hellman public key and send it in a MSG_KEX_DH_GEX_INIT message.

Payload:

    string g (group generator)
    string p (group prime)
Parameters
packet:bytesThe message data.
def ssh_KEX_DH_GEX_REPLY(self, packet): (source)

Called when we receive a MSG_KEX_DH_GEX_REPLY message. Payload:

    string server host key
    integer f (server DH public key)

We verify the host key by calling verifyHostKey, then continue in _continueGEX_REPLY.

Parameters
packet:bytesThe message data.
Returns
A deferred firing once key exchange is complete.
def ssh_KEXINIT(self, packet): (source)

Called when we receive a MSG_KEXINIT message. For a description of the packet, see SSHTransportBase.ssh_KEXINIT(). Additionally, this method sends the first key exchange packet.

If the agreed-upon exchange is ECDH, generate a key pair for the corresponding curve and send the public key.

If the agreed-upon exchange has a fixed prime/generator group, generate a public key and send it in a MSG_KEXDH_INIT message. Otherwise, ask for a 2048 bit group with a MSG_KEX_DH_GEX_REQUEST message.

def ssh_NEWKEYS(self, packet): (source)
Called when we receive a MSG_NEWKEYS message. No payload. If we've finished setting up our own keys, start using them. Otherwise, remember that we've received this message.
Parameters
packet:bytesThe message data.
def ssh_SERVICE_ACCEPT(self, packet): (source)

Called when we receive a MSG_SERVICE_ACCEPT message. Payload:

    string service name

Start the service we requested.

Parameters
packet:bytesThe message data.
def verifyHostKey(self, hostKey, fingerprint): (source)
Returns a Deferred that gets a callback if it is a valid key, or an errback if not.
Parameters
hostKey:bytesThe host key to verify.
fingerprint:bytesThe fingerprint of the key.
Returns
A deferred firing with True if the key is valid.
our Diffie-Hellman public key.
ecPriv = (source)

Undocumented

ecPub = (source)

Undocumented

the Diffie-Hellman group generator.
instance = (source)
the SSHService object we are requesting.
isClient: bool = (source)
since we are always the client, this is always True.
the Diffie-Hellman group prime
our Diffie-Hellman private key.
def _continueGEX_REPLY(self, ignored, pubKey, f, signature): (source)
The host key has been verified, so we generate the keys.
Parameters
ignoredIgnored.
pubKey:strthe public key blob for the server's public key.
f:intthe server's Diffie-Hellman public key.
signature:strthe server's signature, verifying that it has the correct private key.
def _continueKEXDH_REPLY(self, ignored, pubKey, f, signature): (source)
The host key has been verified, so we generate the keys.
Parameters
ignoredIgnored.
pubKey:strthe public key blob for the server's public key.
f:intthe server's Diffie-Hellman public key.
signature:strthe server's signature, verifying that it has the correct private key.
def _keySetup(self, sharedSecret, exchangeHash): (source)
See SSHTransportBase._keySetup().
def _ssh_KEX_ECDH_REPLY(self, packet): (source)

Called to handle a reply to a ECDH exchange message(KEX_ECDH_INIT).

Like the handler for KEXDH_INIT, this message type has an overlapping value. This method is called from ssh_KEX_DH_GEX_GROUP if that method detects a non-group key exchange is in progress.

Payload:

    string serverHostKey
    string server Elliptic Curve Diffie-Hellman public key
    string signature

We verify the host key and continue if it passes verificiation. Otherwise raise an exception and return.

Parameters
packet:bytesThe message data.
Returns
A deferred firing when key exchange is complete.
def _ssh_KEXDH_REPLY(self, packet): (source)

Called to handle a reply to a non-group key exchange message (KEXDH_INIT).

Like the handler for KEXDH_INIT, this message type has an overlapping value. This method is called from ssh_KEX_DH_GEX_GROUP if that method detects a non-group key exchange is in progress.

Payload:

    string serverHostKey
    integer f (server Diffie-Hellman public key)
    string signature

We verify the host key by calling verifyHostKey, then continue in _continueKEXDH_REPLY.

Parameters
packet:bytesThe message data.
Returns
A deferred firing when key exchange is complete.
_dhMaximalGroupSize: int = (source)
Maximal acceptable group size advertised by the client in MSG_KEX_DH_GEX_REQUEST.
_dhMinimalGroupSize: int = (source)
Minimal acceptable group size advertised by the client in MSG_KEX_DH_GEX_REQUEST.
_dhPreferredGroupSize: int = (source)
Preferred group size advertised by the client in MSG_KEX_DH_GEX_REQUEST.
_gotNewKeys: int = (source)
if we receive a MSG_NEWKEYS message before we are ready to transition to the new keys, this is set to True so we can transition when the keys are ready locally.