AUTH 后 Postfix 连接丢失

Question

查看邮件服务器上的日志，我注意到如下消息：

Nov 29 12:09:38 mta postfix/smtpd[8362]: connect from unknown[183.13.165.14]
Nov 29 12:09:39 mta postfix/smtpd[8362]: lost connection after AUTH from unknown[183.13.165.14]
Nov 29 12:09:39 mta postfix/smtpd[8362]: disconnect from unknown[183.13.165.14]
Nov 29 12:09:39 mta postfix/smtpd[8409]: connect from unknown[183.13.165.14]
Nov 29 12:09:40 mta postfix/smtpd[8409]: lost connection after AUTH from unknown[183.13.165.14]
Nov 29 12:09:40 mta postfix/smtpd[8409]: disconnect from unknown[183.13.165.14]

在这些情况下没有 SASL 故障。其他时间会记录 SASL 失败，但从未记录过lost connection after AUTH.

这里发生了什么，我应该做些什么？
这些不是 MX，并且已经smtpd_client_connection_rate_limit设置。

可能相关：
在宣布 AUTH 之前，系统需要 SMTPS 或 STARTTLS。

Answer 1

我的日志文件被填满了，即使允许来自这些混蛋的连接也浪费了 CPU。我创建了一个fail2ban规则。

Jul 11 02:35:08 mail postfix/smtpd[16299]: lost connection after AUTH from unknown[196.12.178.73]

的内容 /etc/fail2ban/jail.conf

[postfix]
# Ban for 10 minutes if it fails 6 times within 10 minutes
enabled  = true
port     = smtp,ssmtp
filter   = postfix
logpath  = /var/log/mail.log
maxretry = 6
bantime  = 600
findtime = 600

的内容 /etc/fail2ban/filter.d/postfix.conf

# Fail2Ban configuration file
#
# Author: Cyril Jaquier
#
# $Revision$
#

[Definition]

# Option:  failregex
# Notes.:  regex to match the password failures messages in the logfile. The
#          host must be matched by a group named "host". The tag "<HOST>" can
#          be used for standard IP/hostname matching and is only an alias for
#          (?:::f{4,6}:)?(?P<host>[\w\-.^_]+)
# Values:  TEXT
#

# Jul 11 02:35:08 mail postfix/smtpd[16299]: lost connection after AUTH from unknown[196.12.178.73]

failregex = lost connection after AUTH from unknown\[<HOST>\]

# Option:  ignoreregex
# Notes.:  regex to ignore. If this regex matches, the line is ignored.
# Values:  TEXT
#
ignoreregex = 

Answer 2

这是一个来自中国的僵尸网络，它连接到您的盒子，试图发送垃圾邮件。但是当被告知要对自己进行身份验证时，机器人太愚蠢了，不知道该怎么做。机器人只是停止发送邮件，然后断开连接以攻击下一个受害者。

绝对没有什么可担心的。

Answer 3

就这样smtpd_recipient_restrictions设置：reject_unknown_client_hostname

smtpd_recipient_restrictions = reject_unknown_client_hostname

这将导致拒绝客户端以及主机名未知的流浪或愚蠢的僵尸机器人。设置后，您的日志将如下所示：

postfix/smtpd[11111]: NOQUEUE: reject: RCPT from unknown[183.13.165.14]: 450 4.7.1 Client host rejected: cannot find your hostname, [183.13.165.14]