电子邮件服务器DKIM配置

时间:2022-05-03
本文章向大家介绍电子邮件服务器DKIM配置，主要内容包括4.3. dkim、4.3.2. 测试、基本概念、基础应用、原理机制和需要注意的事项等，并结合实例形式分析了其使用技巧，希望通过本文能帮助到大家理解应用这部分内容。

本文节选自《Netkiller Mail 手札》

4.3. dkim

DKIM(DomainKeys Identified Mail) 是一种电子邮件的验证技术，使用密码学的基础提供了签名与验证的功能。DKIM 能增加你邮件的信任度。

安装 OpenDKIM 环境是CentOS 7

yum install -y opendkim

查看配置文件

[root@mail.netkiller.cn ~]# egrep -v "^#|^$"  /etc/opendkim.conf
PidFile	/var/run/opendkim/opendkim.pid
Mode	sv
Syslog	yes
SyslogSuccess	yes
LogWhy	yes
UserID	opendkim:opendkim
Socket	inet:8891@localhost
Umask	002
SendReports	yes
SoftwareHeader	yes
Canonicalization	relaxed/relaxed
Selector	default
MinimumKeyBits	1024
KeyFile	/etc/opendkim/keys/default.private
KeyTable	/etc/opendkim/KeyTable
SigningTable	refile:/etc/opendkim/SigningTable
InternalHosts	refile:/etc/opendkim/TrustedHosts
OversignHeaders	From

生成公钥和私钥example.com 替换成你的域名

mkdir /etc/opendkim/keys/example.com
opendkim-genkey -D /etc/opendkim/keys/example.com/ -d example.com -s default
chown -R opendkim: /etc/opendkim/keys/example.com
ln -s /etc/opendkim/keys/example.com/default.private /etc/opendkim/keys/default.private

将你域名example.com添加到/etc/opendkim/KeyTable格式如下：

default._domainkey.example.com example.com:default:/etc/opendkim/keys/example.com/default.private

接下来修改 /etc/opendkim/SigningTable 并添加如下记录

*@example.com default._domainkey.example.com

添加信任主机到/etc/opendkim/TrustedHosts，通常是 example.com / mail.example.com

example.com
mail.example.com

注意：TrustedHosts 是发送邮件机器的IP，不是邮件服务器的IP，例如你的WEB服务器连接到邮件服务器发送电子邮件，那么TrustedHosts 就是你的WEB服务器IP地址。

至此 opendkim 已经配置完毕。

现在需要配置域名TXT记录解析，开打文件 /etc/opendkim/keys/example.com/default.txt 参照下面配置

cat /etc/opendkim/keys/example.com/default.txt 
default._domainkey	IN	TXT	( "v=DKIM1; k=rsa; "
	  "p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC5anjIUkTgJT8DSBL2tiydi6DZLIMnPnveFBcyKshwIuGeRzIN2PwQW5F/bvQWdatPLGuw0w5mKXtATJtarbWXy89BgjcJgAGrPSr8GdzsNH0RXRqTy1A21BQyGER3Mx2Fbr6J62reTG2i7jY0w3/cxzuFIGlSn/RP/KrlMze4zQIDAQAB" )  ; ----- DKIM key default for example.com

接下来配置postfix把OpenDKIM整合到Postfix修改/etc/postfix/main.cf

smtpd_milters           = inet:127.0.0.1:8891
non_smtpd_milters       = $smtpd_milters
milter_default_action   = accept
milter_protocol         = 2

启动 opendkim，重启 postfix

systemctl enable opendkim.service
systemctl start opendkim.service		
systemctl restart postfix.service

检查opendkim状态与端口

# systemctl status opendkim.service
● opendkim.service - DomainKeys Identified Mail (DKIM) Milter
   Loaded: loaded (/usr/lib/systemd/system/opendkim.service; enabled; vendor preset: disabled)
   Active: active (running) since Thu 2016-08-25 02:07:42 EDT; 6s ago
     Docs: man:opendkim(8)
           man:opendkim.conf(5)
           man:opendkim-genkey(8)
           man:opendkim-genzone(8)
           man:opendkim-testadsp(8)
           man:opendkim-testkey
           http://www.opendkim.org/docs.html
  Process: 12577 ExecStart=/usr/sbin/opendkim $OPTIONS (code=exited, status=0/SUCCESS)
 Main PID: 12578 (opendkim)
   CGroup: /system.slice/opendkim.service
           └─12578 /usr/sbin/opendkim -x /etc/opendkim.conf -P /var/run/opendkim/opendkim.pid

Aug 25 02:07:42 localhost.localdomain systemd[1]: Starting DomainKeys Identified Mail (DKIM) Milter...
Aug 25 02:07:42 localhost.localdomain systemd[1]: Started DomainKeys Identified Mail (DKIM) Milter.
Aug 25 02:07:42 localhost.localdomain opendkim[12578]: OpenDKIM Filter v2.10.3 starting (args: -x /etc/opendkim.conf -P /var/run/opendkim/opendkim.pid)


# ss -lnt | grep 8891
LISTEN     0      128    127.0.0.1:8891                     *:*

4.3.1. 增加域名

创建证书

mkdir /etc/opendkim/keys/mydomain.com
opendkim-genkey -D /etc/opendkim/keys/mydomain.com/ -r -d mydomain.com
chown -R opendkim: /etc/opendkim/keys/mydomain.com

配置 KeyTable

default._domainkey.mydomain.com mydomain.com:default:/etc/opendkim/keys/mydomain.com/default.private

配置 SigningTable

*@mydomain.com default._domainkey.mydomain.com

4.3.2. 测试

/var/log/maillog

			Aug 26 03:02:03 localhost postfix/smtpd[5837]: connect from unknown[155.133.82.144]
Aug 26 03:02:03 localhost opendkim[5762]: configuration reloaded from /etc/opendkim.conf
Aug 26 03:02:04 localhost postfix/smtpd[5837]: lost connection after AUTH from unknown[155.133.82.144]
Aug 26 03:02:04 localhost postfix/smtpd[5837]: disconnect from unknown[155.133.82.144]
Aug 26 03:02:09 localhost postfix/smtpd[5837]: connect from unknown[202.130.101.34]
Aug 26 03:02:10 localhost postfix/smtpd[5837]: 27EEC802C1C5: client=unknown[202.130.101.34]
Aug 26 03:02:10 localhost postfix/cleanup[5843]: 27EEC802C1C5: message-id=<1770496307.0.1472194929612@Server>
Aug 26 03:02:10 localhost opendkim[5762]: 27EEC802C1C5: DKIM-Signature field added (s=default, d=cf139.com)
Aug 26 03:02:10 localhost postfix/qmgr[4605]: 27EEC802C1C5: from=<neo@netkiller.cn>, size=531, nrcpt=1 (queue active)
Aug 26 03:02:10 localhost postfix/smtpd[5837]: disconnect from unknown[202.130.101.34]
Aug 26 03:02:10 localhost postfix/smtp[5844]: connect to gmail-smtp-in.l.google.com[2607:f8b0:400e:c03::1b]:25: Network is unreachable
Aug 26 03:02:11 localhost postfix/smtp[5844]: 27EEC802C1C5: to=<netkiller@msn.com>, relay=gmail-smtp-in.l.google.com[74.125.25.26]:25, delay=1.6, delays=0.58/0.01/0.48/0.49, dsn=2.0.0, status=sent (250 2.0.0 OK 1472194931 om6si19759602pac.41 - gsmtp)
Aug 26 03:02:11 localhost postfix/qmgr[4605]: 27EEC802C1C5: removed

查看原件原文，如果正常会显示DKIM-Filter和DKIM-Signature两项

			Delivered-To: netkiller@msn.com
Received: by 10.28.169.3 with SMTP id s3csp180808wme;
        Fri, 26 Aug 2016 00:02:11 -0700 (PDT)
X-Received: by 10.66.10.234 with SMTP id l10mr3141577pab.69.1472194931522;
        Fri, 26 Aug 2016 00:02:11 -0700 (PDT)
Return-Path: <neo@netkiller.cn>
Received: from mail.cf139.com ([104.243.134.186])
        by mx.google.com with ESMTP id om6si19759602pac.41.2016.08.26.00.02.11
        for <netkiller@msn.com>;
        Fri, 26 Aug 2016 00:02:11 -0700 (PDT)
Received-SPF: pass (google.com: domain of neo@netkiller.cn designates 104.243.134.186 as permitted sender) client-ip=104.243.134.186;
Authentication-Results: mx.google.com;
       dkim=temperror (no key for signature) header.i=@cf139.com;
       spf=pass (google.com: domain of neo@netkiller.cn designates 104.243.134.186 as permitted sender) smtp.mailfrom=neo@netkiller.cn
Received: from Server (unknown [202.130.101.34])
	by mail.cf139.com (Postfix) with ESMTP id 27EEC802C1C5
	for <netkiller@msn.com>; Fri, 26 Aug 2016 03:02:09 -0400 (EDT)
DKIM-Filter: OpenDKIM Filter v2.10.3 mail.cf139.com 27EEC802C1C5
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cf139.com;
	s=default; t=1472194930;
	bh=aTYsMuMwFaanDPkTLEncpu/hxKsNsCaozbJRmQJ6aho=;
	h=Date:From:To:Subject:From;
	b=qPYy2TPDv+zxHQ2gqGOwVsgRm42E3p6WvSxdXgUaLtkY6LH6657cdEa96HYJLVqHC
	 EygkTz+3n7WePhGH9jAJrb/PBrGIK1XVCREz4ayfUxc3QUwFSQ9o+5ULkExxdhyRUu
	 4TiCbkcUMbYI3YXJqGiU0OBCyTq655trOaWBby+k=
Date: Fri, 26 Aug 2016 15:02:09 +0800 (CST)
From: neo@netkiller.cn
To: netkiller@msn.com
Message-ID: <1770496307.0.1472194929612@Server>
Subject: =?UTF-8?B?5Li76aKY77ya566A5Y2V6YKu5Lu2?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: base64

5rWL6K+V6YKu5Lu25YaF5a65

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