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README.Debian
fail2ban for Debian ------------------- This package is ~95% identical to the upstream version. Few features could have been added but not yet propagated into upstream version and some modifications might be Debian-specific (logsys logging format). And although due to tight collaboration with upstream author most of the Debian modifications penetrate into the next upstream, few features present in Debian release were rejected by the upstream author (-e option for instance). Currently, the major difference with upstream: python libraries are placed under /usr/share/fail2ban instead of /usr/lib/fail2ban to comply with policy regarding architecture independent resources. Also the main config file /etc/fail2ban.conf is a copy of /usr/share/doc/examples/fail2ban.conf.iptables. There are config files for banning via shorewall or hosts.deny are provided BUT they might miss additional sections present in fail2ban.conf. Please copy them taking care about added sections. Those files will be obsolete in the next release which would handle split configuration files. Default behavior: ----------------- * Enabled Sections: Only handling of ssh files is enabled by default. If you want to use fail2ban with apache, please enable apache section manually in /etc/fail2ban.conf or enable section using command line parameter -e in /etc/default/fail2ban to avoid conflicts during upgrade of the config file. N.B. '-e' command line parameter is present solely in Debian release of fail2ban, thus it will not work if you decided to proceed with vanilla upstream. * Multiport banning: Comment for the wishlist #373592. Default iptables rules for banning use --dport statement which allows to ban just a single port. For multiport banning you would need to adjust iptables rules to use multiport module ( -m multiport --dports %(port)s ). If you would like to ban all ports for that host, just redefine fwban/fwunban commands to don't have --dport %(port)s statement at all (can be redefined on per-section basis as well) Such option is not enabled by default since multiport module might not be compiled for some hand compiled kernels. Troubleshooting: --------------- * Updated failregex: To resolve the security bug #330827 [1] failregex expressions must provide a named group (?P<host>...) as a placeholder of the abuser's host. The naming of the group was introduced to capture possible future generalizations of failregex to provide even more information. At a current point, all named groups are considered as possible locations of the host addresses, but usually you should need just a single group (?P<host>...) [1] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=330827 * "Interpolations" in the config file: Since version 0.6.0-3 to reduce duplication, thus to improve readability of the config file, interpolations provided by the module ConfigParser are used. If you had custom sections defined before, you might benefit from updating config file and adding appropriate information for the new sections. N.B. If you have some nice additional sections defined, I would really appreciate if you share them with me, so they could be eventually included in the fail2ban package for general use by the rest of the community. * Mailing: As it was reported (bug #329722) you might need to provide a full e-mail address in fail2ban.conf option MAIL:from to make your mail server accept that email. I've added @localhost to both MAIL:from and MAIL:to in the default configuration shipped with Debian. It seems to work nicely now See TODO.Debian for more details, as well as the Debian Bug Tracking system. * Dirty exit: If firewall rules gets cleaned out before fail2ban exits (like was happening with firestarter), errors get reported during the exit of fail2ban, but they are "safe" and can be ignored. ** SSHD Configuration Specific Problems * Ban "Not allowed" attempts: Make sure that you have ChallengeResponseAuthentication no PasswordAuthentication yes Details from the bug report #350980 [2] [2] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=350980 * Not caught attempts to login as root On the boxes running older versions of openssh (e.g. sarge distribution) in the case when PermitRootLogin is set to something else than "yes" and iff AllowUsers is active, failed root logins do not confirm to the standard logging message -- they omit the source IP, thus allowing attack to persist since such messages are not caught by fail2ban. * Bantime: An IP is banned for "bantime" not since the last failed login attempt from the IP, but rather since the moment when failed login was detected by fail2ban. Thus, if fail2ban gets [re]started, any IP which had enough of failed logins within "findtime" will be banned for "bantime" since [re]start moment, not since the last failed login time. -- Yaroslav O. Halchenko <debian@onerussian.com>, Sun, 19 Mar 2006 00:27:22 -0500