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.

WINDOWS HACKS

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

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 sysconfidr/gtlssh/gtlsshd.key.
              On  unix sysconfdir is generally /etc.  On Windows it is one directory up from the executable with
              /etc appended.

       -c|--certfile file
              Set the certificate to use.  Defaults to sysconfdir/gtlssh/gtlsshd.crt.   On  unix  sysconfdir  is
              generally /etc.  On Windows it is one directory up from the executable with /etc appended.

       --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.

       --pam-service <name>
              Use the given name for the pam service, instead of using the program's name.

       --use-login, --no-use-login
              Use or do not use the login program to log the user in.  Some  systems  work  better  with  login,
              others  work  fine to directly execute the shell.  The default depends on the system and should be
              best.

       --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.
              This is different than gtlssh's view of interactive, which affects how I/O  is  done.   This  only
              affects prompting for credentials interactively.

       --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.

       --startup-retries
              The  number  of  times  gtlsshd  will  retry  creating  the  accepter.   It retries once a second.
              Generally, if creating the accepter fails, that means the nameserver is not  yet  operational  and
              converting  the local name to an address fails, so this can help with the resolver not being ready
              when gtlsshd starts.  Default is 30.

       -d|--debug
              Generate debugging output.  Specifying more than once increases  the  output.   This  also  causes
              syslog output to go to standard error.

       --version
              Print the version number and exit.

       -h|--help
              Help output

SEE ALSO

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

KNOWN PROBLEMS

       None.

AUTHOR

       Corey Minyard <minyard@acm.org>

Server for shell over TLS                           01/02/19                                          gtlsshd(8)