It is important to note that the use of client alive messages is very different from TCPKeepAlive below. The client alive messages are sent through the encrypted channel and therefore will not be spoofable. The client alive mechanism is valuable when the client or server depend on knowing when a connection has become inactive. The default value is 3. This option applies to protocol version 2 only. ClientAliveInterval Sets a timeout interval in seconds after which if no data has been received from the client, sshd 8 will send a message through the encrypted channel to request a response from the client.
The default is 0, indicating that these messages will not be sent to the client. Compression Specifies whether compression is allowed, or delayed until the user has authenticated successfully. The argument must be ''yes'', ''delayed'', or ''no''. The default is ''delayed''. DenyGroups This keyword can be followed by a list of group name patterns, separated by spaces. Login is disallowed for users whose primary group or supplementary group list matches one of the patterns. DenyUsers This keyword can be followed by a list of user name patterns, separated by spaces.
Login is disallowed for user names that match one of the patterns. The command is invoked by using the user's login shell with the -c option. This applies to shell, command, or subsystem execution. It is most useful inside a Match block. Specifying a command of ''internal-sftp'' will force the use of an in-process sftp server that requires no support files when used with ChrootDirectory.
GatewayPorts Specifies whether remote hosts are allowed to connect to ports forwarded for the client. By default, sshd 8 binds remote port forwardings to the loopback address. This prevents other remote hosts from connecting to forwarded ports. GatewayPorts can be used to specify that sshd should allow remote port forwardings to bind to non-loopback addresses, thus allowing other hosts to connect.
The argument may be ''no'' to force remote port forwardings to be available to the local host only, ''yes'' to force remote port forwardings to bind to the wildcard address, or ''clientspecified'' to allow the client to select the address to which the forwarding is bound. The default is ''no''. Note that this option applies to protocol version 2 only. If ''yes'' then the client must authenticate against the host service on the current hostname.
If ''no'' then the client may authenticate against any service key stored in the machine's default store. This facility is provided to assist with operation on multi homed machines. This option can be used to accepted renewed or updated credentials from a compatible client. A setting of ''yes'' means that sshd 8 uses the name supplied by the client rather than attempting to resolve the name from the TCP connection itself. It is possible to have multiple host key files. IgnoreRhosts Specifies that.
To use this option, the server needs a Kerberos servtab which allows the verification of the KDC's identity. KerberosTicketCleanup Specifies whether to automatically destroy the user's ticket cache file on logout. KerberosUseKuserok Specifies whether to look at. KeyRegenerationInterval In protocol version 1, the ephemeral server key is automatically regenerated after this many seconds if it has been used. The purpose of regeneration is to prevent decrypting captured sessions by later breaking into the machine and stealing the keys.
The key is never stored anywhere. If the value is 0, the key is never regenerated. The default is seconds. ListenAddress Specifies the local addresses sshd 8 should listen on. The default is to listen on all local addresses. Multiple ListenAddress options are permitted. Additionally, any Port options must precede this option for non-port qualified addresses. LoginGraceTime The server disconnects after this time if the user has not successfully logged in.
If the value is 0, there is no time limit. LogLevel Gives the verbosity level that is used when logging messages from sshd 8. LinkPhoenix 1 1 silver badge 4 4 bronze badges. How does this answer the question? I think he's giving directions on configuring a server which accepts ssh connections. In fact it does not answer the question and the original text formatting is impossible to read, I have modified but I do not know if he lewis hamilton will come back to accept the chamges i made.
The question is about the configuration file for the ssh client and not for the ssh server. So I made an answer that answers his question. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Does ES6 make JavaScript frameworks obsolete?
Usually this is done by editing the default configuration file to change just a few options. The SSH server actually reads several configuration files. It may also refer to a number of other files. Many individual developers and power users wish to maximize their convenience rather than go for maximum security. For such use, we recommend the following settings for homes, development servers, and universities.
For important systems even such organizations should follow the guidelines for configuring enterprise servers. Larger enterprises, or others wanting to run a tight security policy for certain servers, may want to configure the following configuration options.
Symmetric algorithms for encrypting the bulk of transferred data are configured using the Ciphers option. A good value is aesctr,aesctr,aesctr. This should also provide good interoperability. Host key algorithms are selected by the HostKeyAlgorithms option. Key exchange algorithms are selected by the KexAlgorithms option. We recommend ecdh-sha2-nistp,ecdh-sha2-nistp,ecdh-sha2-nistp,diffie-hellman-groupsha1,diffie-hellman-group-exchange-sha In particular, we do not recommend allowing diffie-hellman-group1-sha1 , unless needed for compatibility.
It uses a bit prime number, which is too small by today's standards and may be breakable by intelligence agencies in real time.
Using it could expose connections to man-in-the-middle attacks when faced with such adversaries. Message authentication code algorithms are configured using the MACs option. A good value is hmac-sha,hmac-sha,hmac-sha1. We have included the sha-1 algorithm in the above sets only for compatibility. Its use is questionable from a security perspective. If it is not needed for compatibility, we recommend disabling it. NIST has also issued guidance on it. Some organizations may also want to set policy for PubkeyAcceptedKeyTypes.
Active Oldest Votes. Improve this answer. Piotr P. Karwasz Piotr P. Karwasz 4, 2 2 gold badges 7 7 silver badges 19 19 bronze badges. Thanks you Piotr. Why would using exclusive be over zealous?
As far as I know, the other public key algorithms are not broken if the keys are large enough , but better ask on Security StackExchange. Also some elliptic curves may be weak, so I wouldn't trust exclusively ED Sign up or log in Sign up using Google.
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