我在 Debian 9 上运行 fail2ban (0.9.6-2)，并使用 busybox-syslogd 将日志记录到 /var/log/auth.log 设置，并在 /etc/rc.local 中使用以下行将日志写入文件。
/sbin/syslogd -O /var/log/auth.log || exit 1
SSHD jail 已启用，但没有看到失败的登录尝试
使用 sshd 过滤器在 auth.log 文件上运行 fail2ban-regex 不会失败。
sshd_config 设置为 AUTHPRIV 和 VERBOSE
以下是 auth.log 日志的示例：
Jan 14 17:12:41 Fire-Video authpriv.info sshd[2556]: Failed none for video from 192.168.60.5 port 56068 ssh2
Jan 14 17:12:42 Fire-Video authpriv.info sshd[2556]: Failed password for video from 192.168.60.5 port 56068 ssh2
Jan 14 17:12:42 Fire-Video authpriv.info sshd[2556]: Failed password for video from 192.168.60.5 port 56068 ssh2
Jan 14 17:12:42 Fire-Video authpriv.info sshd[2556]: Connection closed by 192.168.60.5 port 56068 [preauth]
Jan 14 17:12:49 Fire-Video authpriv.info sshd[2558]: Connection from 192.168.60.5 port 56074 on 192.168.40.19 port 22
Jan 14 17:12:53 Fire-Video authpriv.debug sshd[2558]: pam_usermapper(sshd:auth): pam_sm_authenticate flags: 00000001
Jan 14 17:12:53 Fire-Video authpriv.notice sshd[2558]: pam_usermapper(sshd:auth): aliasing to 'root'
Jan 14 17:12:53 Fire-Video authpriv.notice sshd[2558]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=192.168.60.5 user=root
Jan 14 17:12:55 Fire-Video authpriv.info sshd[2558]: Failed password for video from 192.168.60.5 port 56074 ssh2
Jan 14 17:13:15 Fire-Video authpriv.debug sshd[2558]: pam_usermapper(sshd:auth): pam_sm_authenticate flags: 00000001
Jan 14 17:13:16 Fire-Video authpriv.info sshd[2558]: Failed password for video from 192.168.60.5 port 56074 ssh2
Jan 14 17:13:21 Fire-Video authpriv.debug sshd[2558]: pam_usermapper(sshd:auth): pam_sm_authenticate flags: 00000001
Jan 14 17:13:21 Fire-Video authpriv.info sshd[2558]: Accepted password for video from 192.168.60.5 port 56074 ssh2
Jan 14 17:13:21 Fire-Video authpriv.info sshd[2558]: pam_unix(sshd:session): session opened for user root by (uid=0)
这是我的 filter.d 中的 sshd.conf
# PasswordAuthentication in sshd_config.
#
#
# "Connection from <HOST> port \d+" requires LogLevel VERBOSE in sshd_config
#
[INCLUDES]
# Read common prefixes. If any customizations available -- read them from
# common.local
before = common.conf
[Definition]
_daemon = sshd
failregex = ^%(__prefix_line)s(?:error: PAM: )?[aA]uthentication (?:failure|error|failed) for .* from <HOST>( via \S+)?\s*$
^%(__prefix_line)s(?:error: PAM: )?User not known to the underlying authentication module for .* from <HOST>\s*$
^%(__prefix_line)sFailed \S+ for (?P<cond_inv>invalid user )?(?P<user>(?P<cond_user>\S+)|(?(cond_inv)(?:(?! from ).)*?|[^:]+)) from <HOST>(?: port \d+)?(?: ssh\d*)?(?(cond_user):|(?:(?:(?! from ).)*)$)
^%(__prefix_line)sROOT LOGIN REFUSED.* FROM <HOST>\s*$
^%(__prefix_line)s[iI](?:llegal|nvalid) user .*? from <HOST>(?: port \d+)?\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)sUser .+ from <HOST> not allowed because not in any group\s*$
^%(__prefix_line)srefused connect from \S+ \(<HOST>\)\s*$
^%(__prefix_line)s(?:error: )?Received disconnect from <HOST>: 3: .*: Auth fail(?: \[preauth\])?$
^%(__prefix_line)sUser .+ from <HOST> not allowed because a group is listed in DenyGroups\s*$
^%(__prefix_line)sUser .+ from <HOST> not allowed because none of user's groups are listed in AllowGroups\s*$
^(?P<__prefix>%(__prefix_line)s)User .+ not allowed because account is locked<SKIPLINES>(?P=__prefix)(?:error: )?Received disconnect from <HOST>: 11: .+ \[preauth\]$
^(?P<__prefix>%(__prefix_line)s)Disconnecting: Too many authentication failures for .+? \[preauth\]<SKIPLINES>(?P=__prefix)(?:error: )?Connection closed by <HOST> \[preauth\]$
^(?P<__prefix>%(__prefix_line)s)Connection from <HOST> port \d+(?: on \S+ port \d+)?<SKIPLINES>(?P=__prefix)Disconnecting: Too many authentication failures for .+? \[preauth\]$
^%(__prefix_line)s(error: )?maximum authentication attempts exceeded for .* from <HOST>(?: port \d*)?(?: ssh\d*)? \[preauth\]$
^%(__prefix_line)spam_unix\(sshd:auth\):\s+authentication failure;\s*logname=\S*\s*uid=\d*\s*euid=\d*\s*tty=\S*\s*ruser=\S*\s*rhost=<HOST>\s.*$
ignoreregex =
[Init]
# "maxlines" is number of log lines to buffer for multi-line regex searches
maxlines = 10
journalmatch = _SYSTEMD_UNIT=sshd.service + _COMM=sshd
# DEV Notes:
#
# "Failed \S+ for .*? from <HOST>..." failregex uses non-greedy catch-all because
# it is coming before use of <HOST> which is not hard-anchored at the end as well,
# and later catch-all's could contain user-provided input, which need to be greedily
# matched away first.
#
# Author: Cyril Jaquier, Yaroslav Halchenko, Petr Voralek, Daniel Black
答案1
所有这些的问题在于，与__prefix_linebusybox syslogd 奇怪的日志格式不匹配。因此 fail2ban 无法理解任何busybox 创建的日志条目。
您可以尝试使用该-S选项使 busybox syslogd 使用缩写日志格式，应该匹配__prefix_line，但作为一般日志用处不大。
/sbin/syslogd -S -O /var/log/auth.log || exit 1