twisted.conch.ssh.transport.SSHServerTransport(SSHTransportBase)
class documentationtwisted.conch.ssh.transport
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SSHServerTransport implements the server side of the SSH protocol.
Instance Variable | isClient | since we are never the client, this is always False. |
Instance Variable | ignoreNextPacket | if True, ignore the next key exchange packet. This is set when the client sends a guessed key exchange packet but with an incorrect guess. |
Instance Variable | dhGexRequest | the KEX_DH_GEX_REQUEST(_OLD) that the client sent. The key generation needs this to be stored. |
Instance Variable | g | the Diffie-Hellman group generator. |
Instance Variable | p | the Diffie-Hellman group prime. |
Method | ssh_KEXINIT | No summary |
Method | ssh_KEX_DH_GEX_REQUEST_OLD | No summary |
Method | ssh_KEX_DH_GEX_REQUEST | No summary |
Method | ssh_KEX_DH_GEX_INIT | Called when we get a MSG_KEX_DH_GEX_INIT message. Payload:: integer e (client DH public key) |
Method | ssh_NEWKEYS | Called when we get a MSG_NEWKEYS message. No payload. When we get this, the keys have been set on both sides, and we start using them to encrypt and authenticate the connection. |
Method | ssh_SERVICE_REQUEST | Called when we get a MSG_SERVICE_REQUEST message. Payload:: string serviceName |
Method | _ssh_KEX_ECDH_INIT | Called from ssh_KEX_DH_GEX_REQUEST_OLD
to handle elliptic curve key exchanges. |
Method | _ssh_KEXDH_INIT | Called to handle the beginning of a non-group key exchange. |
Inherited from SSHTransportBase:
Instance Variable | protocolVersion | A string representing the version of the SSH protocol we support. Currently defaults to '2.0'. |
Instance Variable | version | A string representing the version of the server or client. Currently defaults to 'Twisted'. |
Instance Variable | comment | An optional string giving more information about the server or client. |
Instance Variable | supportedCiphers | A list of strings representing the encryption algorithms supported, in order 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 | supportedKeyExchanges | A list of strings representing the key exchanges supported, in order from most-preferred to least. |
Instance Variable | supportedPublicKeys | A list of strings representing the public key types 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 | supportedLanguages | A list of strings representing languages supported, from most-preferred to least. |
Instance Variable | supportedVersions | A container of strings representing supported ssh protocol version numbers. |
Instance Variable | gotVersion | A boolean indicating whether we have received the version string from the other side. |
Instance Variable | buf | Data we've received but hasn't been parsed into a packet. |
Instance Variable | outgoingPacketSequence | the sequence number of the next packet we will send. |
Instance Variable | incomingPacketSequence | the sequence number of the next packet we are expecting from the other side. |
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 | 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 | ourVersionString | the version string that we sent to the other side. 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 | otherKexInitPayload | the MSG_KEXINIT payload we received. Used in the key exchange |
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 | service | an SSHService instance, or None. If it's set to an object, it's the currently running service. |
Instance Variable | kexAlg 0 | the agreed-upon key exchange algorithm. |
Instance Variable | keyAlg | the agreed-upon public key type for the key exchange. |
Instance Variable | currentEncryptions | an SSHCiphers instance. It represents the current encryption and authentication options for the transport. |
Instance Variable | nextEncryptions | an SSHCiphers instance. Held here until the MSG_NEWKEYS messages are exchanged, when nextEncryptions is transitioned to currentEncryptions. |
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. |
Method | connectionLost | When the underlying connection is closed, stop the running service (if any), and log out the avatar (if any). |
Method | connectionMade | Called when the connection is made to the other side. We sent our version and the MSG_KEXINIT packet. |
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 | getPacket | Try to return a decrypted, authenticated, and decompressed packet out of the buffer. If there is not enough data, return None. |
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 | getPeer | Returns an SSHTransportAddress
corresponding to the other (peer) side of this transport. |
Method | getHost | Returns an SSHTransportAddress
corresponding to the this side of transport. |
Method | kexAlg 1 | The key exchange algorithm name agreed between client and server. |
Method | kexAlg | Set the key exchange algorithm name. |
Method | ssh_DISCONNECT | Called when we receive a MSG_DISCONNECT message. Payload:: long code string description |
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 |
Method | ssh_DEBUG | No summary |
Method | setService | Set our service to service and start it running. If we were running a service previously, stop it first. |
Method | sendDebug | Send a debug message to the other side. |
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 | sendUnimplemented | Send a message to the other side that the last packet was not understood. |
Method | sendDisconnect | Send a disconnect message to the other side and then disconnect. |
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 | loseConnection | Lose the connection to the other side, sending a DISCONNECT_CONNECTION_LOST message. |
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 | receiveDebug | Called when we receive a debug message from the other side. |
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 | _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. |
Method | _allowedKeyExchangeMessageType | Determine if the given message type may be sent while key exchange is in progress. |
Method | _unsupportedVersionReceived | Called when an unsupported version of the ssh protocol is received from the remote endpoint. |
Method | _getKey | Get one of the keys for authentication/encryption. |
Method | _keySetup | Set up the keys for the connection and sends MSG_NEWKEYS when finished, |
Method | _newKeys | No summary |
Inherited from Protocol (via SSHTransportBase):
Method | logPrefix | Return a prefix matching the class name, to identify log messages related to this protocol instance. |
Inherited from BaseProtocol (via SSHTransportBase, Protocol):
Method | makeConnection | Make a connection to a transport and a server. |
Called when we receive a MSG_KEXINIT message. For a description of the packet, see SSHTransportBase.ssh_KEXINIT(). Additionally, this method checks if a guessed key exchange packet was sent. If it was sent, and it guessed incorrectly, the next key exchange packet MUST be ignored.
Called from ssh_KEX_DH_GEX_REQUEST_OLD
to handle elliptic curve key exchanges.
Payload:
string client Elliptic Curve Diffie-Hellman public key
Just like _ssh_KEXDH_INIT
this message type is also not dispatched directly. Extra check to determine
if this is really KEX_ECDH_INIT is required.
First we load the host's public/private keys. Then we generate the ECDH public/private keypair for the given curve. With that we generate the shared secret key. Then we compute the hash to sign and send back to the client Along with the server's public key and the ECDH public key.
Parameters | packet | The message data. (type: bytes ) |
Returns | None. |
Called to handle the beginning of a non-group key exchange.
Unlike other message types, this is not dispatched automatically. It is
called from ssh_KEX_DH_GEX_REQUEST_OLD
because an extra check
is required to determine if this is really a KEXDH_INIT message or if it is
a KEX_DH_GEX_REQUEST_OLD message.
The KEXDH_INIT payload:
integer e (the client's Diffie-Hellman public key)
We send the KEXDH_REPLY with our host key and signature.
Parameters | packet | The message data. (type: bytes ) |
This represents different key exchange methods that share the same
integer value. If the message is determined to be a KEXDH_INIT, _ssh_KEXDH_INIT
is called to handle it. If it is a KEX_ECDH_INIT, _ssh_KEX_ECDH_INIT
is called. Otherwise, for KEX_DH_GEX_REQUEST_OLD payload:
integer ideal (ideal size for the Diffie-Hellman prime) We send the KEX_DH_GEX_GROUP message with the group that is closest in size to ideal.
If we were told to ignore the next key exchange packet by ssh_KEXINIT, drop it on the floor and return.
Parameters | packet | The message data. (type: bytes ) |
Called when we receive a MSG_KEX_DH_GEX_REQUEST message. Payload:
integer minimum integer ideal integer maximum
The client is asking for a Diffie-Hellman group between minimum and maximum size, and close to ideal if possible. We reply with a MSG_KEX_DH_GEX_GROUP message.
If we were told to ignore the next key exchange packet by ssh_KEXINIT, drop it on the floor and return.
Parameters | packet | The message data. (type: bytes ) |
Called when we get a MSG_KEX_DH_GEX_INIT message. Payload:
integer e (client DH public key)
We send the MSG_KEX_DH_GEX_REPLY message with our host key and signature.
Parameters | packet | The message data. (type: bytes ) |
Called when we get a MSG_NEWKEYS message. No payload. When we get this, the keys have been set on both sides, and we start using them to encrypt and authenticate the connection.
Parameters | packet | The message data. (type: bytes ) |
Called when we get a MSG_SERVICE_REQUEST message. Payload:
string serviceName
The client has requested a service. If we can start the service, start it; otherwise, disconnect with DISCONNECT_SERVICE_NOT_AVAILABLE.
Parameters | packet | The message data. (type: bytes ) |