NAME

       gtlsshd - Server for shell over TLS

SYNOPSIS

       gtlsshd [options]

DESCRIPTION

       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.

TWO-FACTOR AUTHENTICATION

       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.

OPTIONS

       -p|--port port
              Use the given port instead of the default port.

       -h|--keyfile file
              Use  the  given  file  for  the  key  instead  of   the   default.    Defaults   to
              /etc/gtlssh/gtlsshd.key.

       -c|--certfile file
              Set the certificate to use.  Defaults to /etc/gtlssh/gtlsshd.crt.

       --permit-root
              Allow root logins.  Otherwise root or uid=0 is denied.

       --allow-password
              Allow  password  logins.   By  default  only  certificate-based logins are allowed.
              Passwords  are  much  less  secure  than  certificate  logins,  so  their  use   is
              discouraged.

       --do-2fa
              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.

       --pam-cert-auth <name>
              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.

       --oneshot
              Do not fork the program at the beginning or when a connection  is  received.   This
              allows easier debugging of the program.

       --nodaemon
              Do not daemonize (double fork) the program.

       --nointeractive
              Disable  interactive  logins.  All authentication information must be passed in via
              the protocol.

       --nosctp
              Disable SCTP support.

       --notcp
              Disable TCP support

       --other_acc <accepter>
              Enable the given accepter to  receive  connections  for  gtlsshd.   This  does  not
              disable TCP or SCTP.

       -P|--pidfile file
              Create a standard pidfile using the given filename.

       -4     Do IPv4 only.

       -6     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.

       -h|--help
              Help output

SEE ALSO

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

KNOWN PROBLEMS

       None.

AUTHOR

       Corey Minyard <minyard@acm.org>