Questions[xinetd](server)

Let's say we have a user account called john on a CentOS server (192.168.1.1) and on the other side we have a user who owns this account and from time to time uses his account from different locations (laptops) to SSH.

[jsmith@mac ~]# ssh [email protected]

[johnsmith@ubuntu ~]# ssh [email protected]

Now, here is the question:

On the server-side, is there any way to find out about the actual local user-id who launched the SSH client in order to initiate the SSH connection which means jsmith for the time that the user was using his Mac machine and johnsmith for the time that the user was using his Ubuntu machine.

Notes and cosideraitions:

• I have root access to the server-side. I can install and configure any service if needed.
• I do not have access to the client's machine and I can not ask him to use a specific SSH client or make any changes to his machine.
• This is the closet post I was able to find. Using ident (xinetd) but the answer is not clear.

Get username of user who initiated SSH connection?

Thank You,

I recently upgraded a system to openSUSE 13.1. We're running a custom-built service on the system through xinetd, and in the old xinetd init script had the line ulimit -c unlimited before starting xinetd to enable core dumps. Since openSUSE 13.1 uses systemd, this does not work anymore.

systemd-coredumpctl does not find any core dumps even though there are kernel log messages that confirm the crashes. Starting the service manually from bash and then sending it SIGSEGV does create a core dump in the directory we configured. How do I get my core dumps back?

I'm using percona-clustercheck (which comes with Percona's XtraDB Cluster packages) with xinetd and I'm getting an error when trying to curl the clustercheck service.

/usr/bin/clustercheck:

#!/bin/bash 
#
# Script to make a proxy (ie HAProxy) capable of monitoring Percona XtraDB Cluster nodes properly
#
# Author: Olaf van Zandwijk <[email protected]>
# Documentation and download: https://github.com/olafz/percona-clustercheck
#
# Based on the original script from Unai Rodriguez 
#

MYSQL_USERNAME="clustercheckuser" 
MYSQL_PASSWORD="clustercheckpassword!" 
ERR_FILE="/dev/null" 
AVAILABLE_WHEN_DONOR=0

#
# Perform the query to check the wsrep_local_state
#
WSREP_STATUS=`mysql --user=${MYSQL_USERNAME} --password=${MYSQL_PASSWORD} -e "SHOW STATUS LIKE 'wsrep_local_state';" 2>${ERR_FILE} | awk '{if (NR!=1){print $2}}' 2>${ERR_FILE}` 

if [[ "${WSREP_STATUS}" == "4" ]] || [[ "${WSREP_STATUS}" == "2" && ${AVAILABLE_WHEN_DONOR} == 1 ]]
then 
    # Percona XtraDB Cluster node local state is 'Synced' => return HTTP 200
    /bin/echo -en "HTTP/1.1 200 OK\r\n" 
    /bin/echo -en "Content-Type: text/plain\r\n" 
    /bin/echo -en "\r\n" 
    /bin/echo -en "Percona XtraDB Cluster Node is synced.\r\n" 
    /bin/echo -en "\r\n" 
    exit 0
else 
    # Percona XtraDB Cluster node local state is not 'Synced' => return HTTP 503
    /bin/echo -en "HTTP/1.1 503 Service Unavailable\r\n" 
    /bin/echo -en "Content-Type: text/plain\r\n" 
    /bin/echo -en "\r\n" 
    /bin/echo -en "Percona XtraDB Cluster Node is not synced.\r\n" 
    /bin/echo -en "\r\n"
    exit 1 
fi

/etc/xinetd.mysqlchk:

# default: on
# description: mysqlchk
service mysqlchk
{
# this is a config for xinetd, place it in /etc/xinetd.d/
  disable = no
  flags = REUSE
  socket_type = stream
  port = 9200
  wait = no
  user = nobody
  server = /usr/bin/clustercheck
  log_on_failure += USERID
  only_from = 10.0.0.0/8 127.0.0.1
  # recommended to put the IPs that need
  # to connect exclusively (security purposes)
  per_source = UNLIMITED
}

When attempting to curl the service, I get a valid response (HTTP 200, text) but a 'connection reset by peer' notice at the end:

HTTP/1.1 200 OK
Content-Type: text/plain

Percona XtraDB Cluster Node is synced.

curl: (56) Recv failure: Connection reset by peer

Unfortunately, Amazon ELB appears to see this as a failed check, not a succeeded one.

How can I get clustercheck to exit gracefully in a manner that curl doesn't see a connection failure?

I have recently found out that a server I am working on has an xinetd service that is in fact a shell script that calls another shell script with arguments retrieved via respective network connections.

It does something like this:

    /execute/another/script $WITH $A $FEW $ARGUMENTS

What makes me afraid this is a real problem is the fact that the variables are not sanitized in any way and since this is executed as root it's something to be taken seriously.

Could someone please advise? I would also be curious to find out how one can abuse variables in such situations in order to have something else executed, can someone provide examples?

According to my current understanding, tcpwrappers can be used via inetd or xinetd. Lately I have been informed that inetd/xinetd came into existence to make more efficient use of hardware in earlier days and are therefore seen rarely nowadays.

My question is, if tcpwrappers are now considered to be an outdated technique, too. If yes, what is their replacement?