ENH: catch failed ssh logins due to being listed in DenyUsers. Close gh-47 (Closes: #669063)

config/filter.d/sshd.conf

@@ -29,6 +29,7 @@ failregex = ^%(__prefix_line)s(?:error: PAM: )?Authentication failure for .* fro
             ^%(__prefix_line)sROOT LOGIN REFUSED.* FROM <HOST>\s*$
             ^%(__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)srefused connect from \S+ \(<HOST>\)\s*$
             ^%(__prefix_line)sAddress <HOST> .* POSSIBLE BREAK-IN ATTEMPT!*\s*$

testcases/files/logs/sshd

@@ -24,3 +24,6 @@ Nov 11 23:33:27 Server sshd[5174]: refused connect from _U2FsdGVkX19P3BCJmFBHhjL
 #7 added exclamation mark to BREAK-IN
 Oct 15 19:51:35 server sshd[7592]: Address 1.2.3.4 maps to 1234.bbbbbb.com, but this does not map back to the address - POSSIBLE BREAK-IN ATTEMPT
 Oct 15 19:51:35 server sshd[7592]: Address 1.2.3.4 maps to 1234.bbbbbb.com, but this does not map back to the address - POSSIBLE BREAK-IN ATTEMPT!
+
+#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