Have a look at the following doc:
http://lists.mindrot.org/pipermail/openssh-unix-dev/2003-January/016430.html
otherwise you can create an login file and use syslog to log the ssh login infor to a file, here're the procedures I wrote long time ago:
To log all the ssh login infor:
edit sshd_config file, to set these directives:
#obsoletes QuietMode and FascistLogging
SyslogFacility AUTH
LogLevel INFO
We can increase your logging level with "DEBUG" in Loglevel directive.
# debug mode will generate a large log file, INFO is good enough for us.
Create a specific ssh logfile:
touch /var/adm/sshlog
chgrp sys /var/adm/sshlog
Edit /etc/syslog.conf file , to add this entry:
auth.debug /var/adm/sshlog # Must space
# log ssh connnetions add by Greg Yu, 7/7/2006
#auth.debug /var/adm/sshlog
auth.info /var/adm/sshlog
Stop e restart syslog service.
/etc/rc2.d/S74syslog stop
/etc/rc2.d/S74syslog start
Check your new logfile /var/adm/sshlog