ENH: match possibly present "pam_unix(sshd:auth):" portion for sshd (Closes: #648020)

config/filter.d/sshd.conf

@@ -30,7 +30,7 @@ failregex = ^%(__prefix_line)s(?:error: PAM: )?Authentication failure for .* fro
             ^%(__prefix_line)s[iI](?:llegal|nvalid) user .* from <HOST>\s*$
             ^%(__prefix_line)sUser .+ from <HOST> not allowed because not listed in AllowUsers\s*$
             ^%(__prefix_line)sUser .+ from <HOST> not allowed because listed in DenyUsers\s*$
-            ^%(__prefix_line)sauthentication failure; logname=\S* uid=\S* euid=\S* tty=\S* ruser=\S* rhost=<HOST>(?:\s+user=.*)?\s*$
+            ^%(__prefix_line)s(?:pam_unix\(sshd:auth\):\s)?authentication failure; logname=\S* uid=\S* euid=\S* tty=\S* ruser=\S* rhost=<HOST>(?:\s+user=.*)?\s*$
             ^%(__prefix_line)srefused connect from \S+ \(<HOST>\)\s*$
             ^%(__prefix_line)sAddress <HOST> .* POSSIBLE BREAK-IN ATTEMPT!*\s*$
             ^%(__prefix_line)sUser .+ from <HOST> not allowed because none of user's groups are listed in AllowGroups\s*$

testcases/files/logs/sshd

@@ -27,3 +27,6 @@ Oct 15 19:51:35 server sshd[7592]: Address 1.2.3.4 maps to 1234.bbbbbb.com, but
 
 #8 DenyUsers https://github.com/fail2ban/fail2ban/issues/47
 Apr 16 22:01:15 al-ribat sshd[5154]: User root from 46.45.128.3 not allowed because listed in DenyUsers
+
+# http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=648020
+Nov  8 11:19:38 bar sshd[25427]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=1.2.3.6