gtlsshd(8) System Manager's Manual gtlsshd(8)

gtlsshd - Server for shell over TLS

gtlsshd [options]

The gtlsshd program receives connections from gtlssh, authenticates the connections, and connects them to a shell or a program as requested.

gtlsshd will listen on both SCTP and TCP sockets unless told otherwise.

gtlsshd uses openssl public key certificate authentication both directions. When something connections, it uses standard SSL handling to validate itself to the user with the given key and certificate files.

On SSL does its job, it then runs an authentication protocol for the user on top of the SSL connection. The user sends the username, and gtlsshd will use the $HOME/.gtlssh/allowed_certs directory to authenticate a certificate the user presents. If the user doesn't have a certificate that matches the presented certificate, gtlsshd will attempt a normal password login if that is enabled.

See "WINDOWS HACKS" in the gtlssh-keygen.1 man page for information about special windows configuration.

gtlsshd supports two-factor authentication in a number of ways. The certauth gensio supports sending a second authentication token, gtlsshd will pick that up and use it if PAM asks for it. If it's not there but PAM asks for it, it will interactively prompt the user for the token unless --nointeractive is specified.

This requires, of course, proper PAM setup. It also direclty supports second authentication tokens with certificates. You can specify a different PAM authentication script for logins done with certificates using --pam-cert-auth to allow a second factor to be added for just certificate authentications.

You can request that the other end prompt for a second-factor authentication token and send it along with the password by adding the --do-2fa option. This will cause the other end to always ask for a second factor.

Use the given port instead of the default port.
Use the given file for the key instead of the default. Defaults to /etc/gtlssh/gtlsshd.key.
Set the certificate to use. Defaults to /etc/gtlssh/gtlsshd.crt.
Allow root logins. Otherwise root or uid=0 is denied.
Allow password logins. By default only certificate-based logins are allowed. Passwords are much less secure than certificate logins, so their use is discouraged.
Enable 2-factor authentication. This means that 2-factor authentication is enabled in PAM for gtlssh. This will cause the client end to request 2-factor data and transmit it over along with the password. During authentication, it is expected that PAM will request two authentication tokens and the first will be the password (if certificate failed). Note that this is not required to do 2-factor auth, but is useful to allow gtlssh to read the 2-factor data and transfer it as part of the login data.
If the connection is authorized with a certificate, still do a PAM authentication, but use the given name as the program name for PAM to use to find the rules. This will allow 2-factor auth to be done on a certificate login, as the given set of rules can be written to only do the second factor authentication part.
Do not fork the program at the beginning or when a connection is received. This allows easier debugging of the program.
Do not daemonize (double fork) the program.
Disable interactive logins. All authentication information must be passed in via the protocol. This is different than gtlssh's view of interactive, which affects how I/O is done. This only affects prompting for credentials interactively.
Disable SCTP support.
Disable TCP support
Enable the given accepter to receive connections for gtlsshd. This does not disable TCP or SCTP.
Create a standard pidfile using the given filename.
Do IPv4 only.
Do IPv6 only. -d|--debug Generate debugging output. Specifying more than once increases the output. This also causes syslog output to go to standard error.
Print the version number and exit.
Help output

gensio(5), gtlssh(1), gtlssh-keygen(1)


Corey Minyard <>

01/02/19 Server for shell over TLS