fail2ban custom filter on multiline

Question

Is it possible to catch authentication failure on multiple line with fail2ban regex?

Here is the example :

Sep 08 11:54:59.207814 afpd[16190] {dsi_tcp.c:241} (I:DSI): AFP/TCP session from 10.0.71.149:53863
Sep 08 11:54:59.209504 afpd[16190] {uams_dhx2_pam.c:329} (I:UAMS): DHX2 login: thierry
Sep 08 11:54:59.272092 afpd[16190] {uams_dhx2_pam.c:214} (I:UAMS): PAM DHX2: PAM Success
Sep 08 11:55:01.522258 afpd[16190] {uams_dhx2_pam.c:666} (I:UAMS): DHX2: PAM_Error: Authentication failure

Thanks

Answer 1

Yeah sure, fail2ban uses python regex with the multiline option. In your case, try:

"afpd\[[0-9]+\] {dsi_tcp.c:241} \(I:DSI\): AFP/TCP session from <HOST>:[0-9]+\n.*afpd\[[0-9]+\] {uams_dhx2_pam.c:[0-9]+}.*\n.*afpd\[[0-9]+\] {uams_dhx2_pam.c:[0-9]+}.*\n.*afpd\[[0-9]+\] {uams_dhx2_pam.c:[0-9]+}.*PAM_Error: Authentication failure"

As you can see, you just have to put \n where needed. Don't forgot to set the maxlines option to 4 in your case, so that fail2ban uses 4 lines to match the regex. Your filter file should look something like:

[Init]
maxlines = 4

[Definition]

failregex = "afpd\[[0-9]+\] {dsi_tcp.c:241} \(I:DSI\): AFP/TCP session from <HOST>:[0-9]+\n.*afpd\[[0-9]+\] {uams_dhx2_pam.c:[0-9]+}.*\n.*afpd\[[0-9]+\] {uams_dhx2_pam.c:[0-9]+}.*\n.*afpd\[[0-9]+\] {uams_dhx2_pam.c:[0-9]+}.*PAM_Error: Authentication failure"

ignoreregex =

Use fail2ban-regex to test your regex.