mjhjmtu

This is the scenario: I have a server that's listening on port 6514 on TCP for logs. I created the .key .crt files on the server as described here: https://www.logzilla.net/2014/10/17/configuring-tls-tunnels-in-syslog-ng.html:

 [root@server1 ~]$ openssl genrsa -des3 -out logserver.key 2048
 Generating RSA private key, 2048 bit long modulus
 .................................................+++
 .+++
 e is 65537 (0x10001)
 Enter pass phrase for logserver.key:
 Verifying - Enter pass phrase for logserver.key:
 [root@server1 ~]$ openssl req -new -key logserver.key -out logserver.csr
 Enter pass phrase for logserver.key:
 You are about to be asked to enter information that will be incorporated
 into your certificate request.
 What you are about to enter is what is called a Distinguished Name or a 
 DN.
 There are quite a few fields but you can leave some blank
 For some fields there will be a default value,
 If you enter '.', the field will be left blank.
 -----
 Country Name (2 letter code) [XX]:
 State or Province Name (full name) :
 Locality Name (eg, city) [Default City]:
 Organization Name (eg, company) [Default Company Ltd]:
 Organizational Unit Name (eg, section) :
 Common Name (eg, your name or your server's hostname) :
 Email Address :

 Please enter the following 'extra' attributes
 to be sent with your certificate request
 A challenge password :
 An optional company name :
 [root@server1 ~]$ cp logserver.key logserver.key.org
 [root@server1 ~]$ openssl rsa -in logserver.key.org -out logserver.key
 Enter pass phrase for logserver.key.org:
 writing RSA key
 [root@server1 ~]$ openssl x509 -req -days 365 -in logserver.csr -signkey 
 logserver.key -out logserver.crt
 Signature ok
 subject=/C=XX/L=Default City/O=Default Company Ltd
 Getting Private key

and placed the settings in a created file named tls.conf in the /etc/syslog-ng/conf.d

I followed the next instructions.
Connect to the Client and mkdir -p /etc/syslog-ng/ssl. Download/Upload the /etc/syslog-ng/ssl/logserver.crt (which was created earlier on the Server) to the Client system and put the file in /etc/syslog-ng/ssl on the Client.

Find the hash for your key by running openssl x509 -noout -hash -in /etc/syslog-ng/ssl/logserver.crt

Next, create a symbolic link to the certificate that uses the hash returned by the previous command, with an added .0 suffix.

ln -s /etc/syslog-ng/ssl/logserver.crt /etc/syslog-ng/ssl/84d92a45.0

As soon as I add the client-to-server.conf under /etc/syslog-ng/conf.d/client-to-server.conf that has the following

@version:3.14
@define allow-config-dups 1
@include "scl.conf"
destination d_tls 
 tcp("192.168.1.7" port(6514)
 tls( ca_dir("/etc/syslog-ng/ssl/")) );
 ;

 log 
 source(s_sys);
 destination(d_tls);
 ;

the syslog-ng service won't start on the client.

 systemctl restart syslog-ng.service
 Job for syslog-ng.service failed because the control process exited with 
 error code. See "systemctl status syslog-ng.service" and "journalctl -xe" 
 for details.



 [root@localhost conf.d]# systemctl status syslog-ng.service -l
● syslog-ng.service - System Logger Daemon
 Loaded: loaded (/usr/lib/systemd/system/syslog-ng.service; enabled; vendor preset: enabled)
 Active: failed (Result: start-limit) since Thu 2018-06-07 22:50:30 EEST; 7min ago
 Docs: man:syslog-ng(8)
 Process: 18196 ExecStart=/usr/sbin/syslog-ng -F $SYSLOGNG_OPTS -p /var/run/syslogd.pid (code=exited, status=2)
 Main PID: 18196 (code=exited, status=2)
 Status: "Starting up... (Thu Jun 7 22:50:30 2018"

Jun 07 22:50:30 localhost.localdomain systemd[1]: syslog-ng.service: main process exited, code=exited, status=2/INVALIDARGUMENT
Jun 07 22:50:30 localhost.localdomain systemd[1]: Failed to start System Logger Daemon.
Jun 07 22:50:30 localhost.localdomain systemd[1]: Unit syslog-ng.service entered failed state.
Jun 07 22:50:30 localhost.localdomain systemd[1]: syslog-ng.service failed.
Jun 07 22:50:30 localhost.localdomain systemd[1]: syslog-ng.service holdoff time over, scheduling restart.
Jun 07 22:50:30 localhost.localdomain systemd[1]: start request repeated too quickly for syslog-ng.service
Jun 07 22:50:30 localhost.localdomain systemd[1]: Failed to start System Logger Daemon.
Jun 07 22:50:30 localhost.localdomain systemd[1]: Unit syslog-ng.service entered failed state.
Jun 07 22:50:30 localhost.localdomain systemd[1]: syslog-ng.service failed.

[root@localhost conf.d]# journalctl -xe
-- Subject: Unit syslog-ng.service has begun start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit syslog-ng.service has begun starting up.
Jun 07 22:50:30 localhost.localdomain syslog-ng[18190]: [2018-06-07T22:50:30.022361] Error setting up TLS session context; tls_error='(null):(null):(null)'
Jun 07 22:50:30 localhost.localdomain syslog-ng[18190]: [2018-06-07T22:50:30.022410] Error initializing message pipeline; plugin name='tcp', location='/etc/syslog-ng/conf.d/client-to-server.conf:5:7'
Jun 07 22:50:30 localhost.localdomain systemd[1]: syslog-ng.service: main process exited, code=exited, status=2/INVALIDARGUMENT
Jun 07 22:50:30 localhost.localdomain systemd[1]: Failed to start System Logger Daemon.
-- Subject: Unit syslog-ng.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit syslog-ng.service has failed.
-- 
-- The result is failed.
Jun 07 22:50:30 localhost.localdomain systemd[1]: Unit syslog-ng.service entered failed state.
Jun 07 22:50:30 localhost.localdomain systemd[1]: syslog-ng.service failed.
Jun 07 22:50:30 localhost.localdomain systemd[1]: syslog-ng.service holdoff time over, scheduling restart.
Jun 07 22:50:30 localhost.localdomain systemd[1]: Starting System Logger Daemon...
-- Subject: Unit syslog-ng.service has begun start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit syslog-ng.service has begun starting up.
Jun 07 22:50:30 localhost.localdomain syslog-ng[18193]: [2018-06-07T22:50:30.281966] Error setting up TLS session context; tls_error='(null):(null):(null)'
Jun 07 22:50:30 localhost.localdomain syslog-ng[18193]: [2018-06-07T22:50:30.282017] Error initializing message pipeline; plugin name='tcp', location='/etc/syslog-ng/conf.d/client-to-server.conf:5:7'
Jun 07 22:50:30 localhost.localdomain systemd[1]: syslog-ng.service: main process exited, code=exited, status=2/INVALIDARGUMENT
Jun 07 22:50:30 localhost.localdomain systemd[1]: Failed to start System Logger Daemon.
-- Subject: Unit syslog-ng.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit syslog-ng.service has failed.
-- 
-- The result is failed.
Jun 07 22:50:30 localhost.localdomain systemd[1]: Unit syslog-ng.service entered failed state.
Jun 07 22:50:30 localhost.localdomain systemd[1]: syslog-ng.service failed.
Jun 07 22:50:30 localhost.localdomain systemd[1]: syslog-ng.service holdoff time over, scheduling restart.
Jun 07 22:50:30 localhost.localdomain systemd[1]: Starting System Logger Daemon...
-- Subject: Unit syslog-ng.service has begun start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit syslog-ng.service has begun starting up.
Jun 07 22:50:30 localhost.localdomain syslog-ng[18196]: [2018-06-07T22:50:30.522580] Error setting up TLS session context; tls_error='(null):(null):(null)'
Jun 07 22:50:30 localhost.localdomain syslog-ng[18196]: [2018-06-07T22:50:30.522870] Error initializing message pipeline; plugin name='tcp', location='/etc/syslog-ng/conf.d/client-to-server.conf:5:7'
Jun 07 22:50:30 localhost.localdomain systemd[1]: syslog-ng.service: main process exited, code=exited, status=2/INVALIDARGUMENT
Jun 07 22:50:30 localhost.localdomain systemd[1]: Failed to start System Logger Daemon.
-- Subject: Unit syslog-ng.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit syslog-ng.service has failed.
-- 
-- The result is failed.
Jun 07 22:50:30 localhost.localdomain systemd[1]: Unit syslog-ng.service entered failed state.
Jun 07 22:50:30 localhost.localdomain systemd[1]: syslog-ng.service failed.
Jun 07 22:50:30 localhost.localdomain systemd[1]: syslog-ng.service holdoff time over, scheduling restart.
Jun 07 22:50:30 localhost.localdomain systemd[1]: start request repeated too quickly for syslog-ng.service
Jun 07 22:50:30 localhost.localdomain systemd[1]: Failed to start System Logger Daemon.
-- Subject: Unit syslog-ng.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit syslog-ng.service has failed.
-- 
-- The result is failed.
Jun 07 22:50:30 localhost.localdomain systemd[1]: Unit syslog-ng.service entered failed state.
Jun 07 22:50:30 localhost.localdomain systemd[1]: syslog-ng.service failed.

What am I doing wrong?

The syslog-ng client configuration section with tls for you should looks as below:

destination d_tls 
 network("192.168.1.7" port(6514)
 transport("tls")
 tls( ca-dir("/etc/syslog-ng/ssl/ca.d")
 key-file("/etc/syslog-ng/ssl/mykey.key")
 cert-file("/etc/syslog-ng/ssl/mykey.pem")) );
;
log 
 source(s_sys);
 destination(d_tls);
;