はじめに
AmazonLinux2023用のOpenDKIMリポジトリがなく、epel、rpmも使用できない...
AWS SESを使わずにEC2内で完結したい場合はビルドするしかない！
opendkimをインストール
ビルドや動作に必要なパッケージをインストール
（この中にもリポジトリが存在しないパッケージがあったかも）
EC2
[root@ip-xx-xx-xx-xx etc]# dnf install sendmail-devel openssl-devel libbsd-devel autoconf automake libtool
[root@ip-xx-xx-xx-xx etc]# dnf install gcc make libmilter libmilter-devel zlib-devel openssl-devel
opendkimのソースをダウンロード＆解凍
EC2
[root@ip-xx-xx-xx-xx etc]# cd /etc/
[root@ip-xx-xx-xx-xx etc]# wget https://downloads.sourceforge.net/project/opendkim/opendkim-2.10.3.tar.gz
[root@ip-xx-xx-xx-xx etc]# tar -xvf opendkim-2.10.3.tar.gz
ビルド作業
EC2
[root@ip-xx-xx-xx-xx etc]# cd opendkim-2.10.3
[root@ip-xx-xx-xx-xx opendkim-2.10.3]# mv configure configure.old
[root@ip-xx-xx-xx-xx opendkim-2.10.3]# cat configure.old | sed '16732,16862d' > configure
[root@ip-xx-xx-xx-xx opendkim-2.10.3]# chmod +x configure
[root@ip-xx-xx-xx-xx opendkim-2.10.3]# ./configure --prefix=/usr/local --sysconfdir=/etc --localstatedir=/var/run/opendkim
[root@ip-xx-xx-xx-xx opendkim-2.10.3]# make & make install
インストールできたか確認
EC2
[root@ip-xx-xx-xx-xx opendkim-2.10.3]# /usr/local/sbin/opendkim -V
opendkim: OpenDKIM Filter v2.10.3
Compiled with OpenSSL 3.0.8 7 Feb 2023
SMFI_VERSION 0x1000001
libmilter version 1.0.1
Supported signing algorithms:
rsa-sha1
rsa-sha256
Supported canonicalization algorithms:
relaxed
simple
libopendkim 2.10.3:
ユーザ・ディレクトリ・設定ファイルを作成
ビルドのため自分で作成する必要がある
opendkimユーザの作成
EC2
[root@ip-xx-xx-xx-xx etc]# useradd -r -s /sbin/nologin opendkim
/var/run/ にディレクトリ作成・権限変更
EC2
[root@ip-xx-xx-xx-xx etc]# mkdir -p /var/run/opendkim
[root@ip-xx-xx-xx-xx etc]# chmod 750 /var/run/opendkim
[root@ip-xx-xx-xx-xx etc]# chown -R opendkim:opendkim /var/run/opendkim
設定ファイル
/etc/opendkim.conf を作成
EC2
[root@ip-xx-xx-xx-xx etc]# cd /etc/
[root@ip-xx-xx-xx-xx etc]# touch opendkim.conf
[root@ip-xx-xx-xx-xx etc]# vi opendkim.conf
/etc/opendkim.conf
/etc/opendkim.conf
## BASIC OPENDKIM CONFIGURATION FILE
## See opendkim.conf(5) or /usr/share/doc/opendkim/opendkim.conf.sample for more
## BEFORE running OpenDKIM you must:
## - make your MTA (Postfix, Sendmail, etc.) aware of OpenDKIM
## - generate keys for your domain (if signing)
## - edit your DNS records to publish your public keys (if signing)
## See /usr/share/doc/opendkim/INSTALL for detailed instructions.
## DEPRECATED CONFIGURATION OPTIONS
##
## The following configuration options are no longer valid. They should be
## removed from your existing configuration file to prevent potential issues.
## Failure to do so may result in opendkim being unable to start.
##
## Removed in 2.10.0:
## AddAllSignatureResults
## ADSPAction
## ADSPNoSuchDomain
## BogusPolicy
## DisableADSP
## LDAPSoftStart
## LocalADSP
## NoDiscardableMailTo
## On-PolicyError
## SendADSPReports
## UnprotectedPolicy
## CONFIGURATION OPTIONS
## Specifies the path to the process ID file.
#PidFile /run/opendkim/opendkim.pid
## Selects operating modes. Valid modes are s (sign) and v (verify). Default is v.
## Must be changed to s (sign only) or sv (sign and verify) in order to sign outgoing
## messages.
Mode s
## Log activity to the system log.
Syslog yes
## Log additional entries indicating successful signing or verification of messages.
SyslogSuccess yes
## If logging is enabled, include detailed logging about why or why not a message was
## signed or verified. This causes an increase in the amount of log data generated
## for each message, so set this to No (or comment it out) if it gets too noisy.
LogWhy yes
## Attempt to become the specified user before starting operations.
UserID opendkim:opendkim
## Create a socket through which your MTA can communicate.
Socket inet:8891@127.0.0.1
#Socket local:/run/opendkim/opendkim.sock
## Required to use local socket with MTAs that access the socket as a non-
## privileged user (e.g. Postfix)
Umask 002
## This specifies a text file in which to store DKIM transaction statistics.
## OpenDKIM must be manually compiled with --enable-stats to enable this feature.
# Statistics /var/spool/opendkim/stats.dat
## Specifies whether or not the filter should generate report mail back
## to senders when verification fails and an address for such a purpose
## is provided. See opendkim.conf(5) for details.
SendReports yes
## Specifies the sending address to be used on From: headers of outgoing
## failure reports. By default, the e-mail address of the user executing
## the filter is used (executing_user@hostname).
# ReportAddress "Example.com Postmaster" <postmaster@example.com>
## Add a DKIM-Filter header field to messages passing through this filter
## to identify messages it has processed.
SoftwareHeader no
## SIGNING OPTIONS
## Selects the canonicalization method(s) to be used when signing messages.
Canonicalization relaxed/relaxed
## Domain(s) whose mail should be signed by this filter. Mail from other domains will
## be verified rather than being signed. Uncomment and use your domain name.
## This parameter is not required if a SigningTable is in use.
# Domain example.com
## Defines the name of the selector to be used when signing messages.
Selector default
## Specifies the minimum number of key bits for acceptable keys and signatures.
MinimumKeyBits 1024
## Gives the location of a private key to be used for signing ALL messages. This
## directive is ignored if KeyTable is enabled.
KeyFile /etc/opendkim/keys/default.private
## Gives the location of a file mapping key names to signing keys. In simple terms,
## this tells OpenDKIM where to find your keys. If present, overrides any KeyFile
## directive in the configuration file. Requires SigningTable be enabled.
KeyTable /etc/opendkim/KeyTable
## Defines a table used to select one or more signatures to apply to a message based
## on the address found in the From: header field. In simple terms, this tells
## OpenDKIM how to use your keys. Requires KeyTable be enabled.
SigningTable refile:/etc/opendkim/SigningTable
## Identifies a set of "external" hosts that may send mail through the server as one
## of the signing domains without credentials as such.
ExternalIgnoreList refile:/etc/opendkim/TrustedHosts
## Identifies a set "internal" hosts whose mail should be signed rather than verified.
InternalHosts refile:/etc/opendkim/TrustedHosts
## Contains a list of IP addresses, CIDR blocks, hostnames or domain names
## whose mail should be neither signed nor verified by this filter. See man
## page for file format.
# PeerList X.X.X.X
## Always oversign From (sign using actual From and a null From to prevent
## malicious signatures header fields (From and/or others) between the signer
## and the verifier. From is oversigned by default in the Fedora package
## because it is often the identity key used by reputation systems and thus
## somewhat security sensitive.
OversignHeaders From
## Instructs the DKIM library to maintain its own local cache of keys and
## policies retrieved from DNS, rather than relying on the nameserver for
## caching service. Useful if the nameserver being used by the filter is
## not local.
# QueryCache yes
/etc/ にopendkimディレクトリを作成・権限変更
EC2
[root@ip-xx-xx-xx-xx etc]# cd /etc/
[root@ip-xx-xx-xx-xx etc]# mkdir opendkim
[root@ip-xx-xx-xx-xx etc]# chown -R opendkim:opendkim /etc/opendkim
[root@ip-xx-xx-xx-xx etc]# cd opendkim/
[root@ip-xx-xx-xx-xx opendkim]# mkdir keys
[root@ip-xx-xx-xx-xx opendkim]# chmod 750 keys/
鍵を作成
EC2
[root@ip-xxx-xx-xx-xx opendkim]# opendkim-genkey -D /etc/opendkim/keys/ -s hoge
[root@ip-xxx-xx-xx-xx opendkim]# cd keys/
[root@ip-xxx-xx-xx-xx keys]# ll
total 8
-rw-------. 1 opendkim opendkim 916 Dec 11 16:03 hoge.private
-rw-------. 1 opendkim opendkim 313 Dec 11 16:03 hoge.txt
KeyTableの作成
EC2
[root@ip-xx-xx-xx-xx opendkim]# cd /etc/opendkim/
[root@ip-xx-xx-xx-xx opendkim]# touch KeyTable
[root@ip-xx-xx-xx-xx opendkim]# vi KeyTable
作成した鍵の情報を記載
KeyTable
# OPENDKIM KEY TABLE
# To use this file, uncomment the #KeyTable option in /etc/opendkim.conf,
# then uncomment the following line and replace example.com with your domain
# name, then restart OpenDKIM. Additional keys may be added on separate lines.
hoge._domainkey.example.com example.com:hoge:/etc/opendkim/keys/hoge.private
SigningTableの作成
EC2
[root@ip-xx-xx-xx-xx opendkim]# cd /etc/opendkim/
[root@ip-xx-xx-xx-xx opendkim]# touch SigningTable
[root@ip-xx-xx-xx-xx opendkim]# vi SigningTable
最下部に作成した鍵の情報を記載
SigningTable
# OPENDKIM SIGNING TABLE
# This table controls how to apply one or more signatures to outgoing messages based
# on the address found in the From: header field. In simple terms, this tells
# OpenDKIM "how" to apply your keys.
# To use this file, uncomment the SigningTable option in /etc/opendkim.conf,
# then uncomment one of the usage examples below and replace example.com with your
# domain name, then restart OpenDKIM.
# WILDCARD EXAMPLE
# Enables signing for any address on the listed domain(s), but will work only if
# "refile:/etc/opendkim/SigningTable" is included in /etc/opendkim.conf.
# Create additional lines for additional domains.
#*@example.com default._domainkey.example.com
# NON-WILDCARD EXAMPLE
# If "file:" (instead of "refile:") is specified in /etc/opendkim.conf, then
# wildcards will not work. Instead, full user@host is checked first, then simply host,
# then user@.domain (with all superdomains checked in sequence, so "foo.example.com"
# would first check "user@foo.example.com", then "user@.example.com", then "user@.com"),
# then .domain, then user@*, and finally *. See the opendkim.conf(5) man page under
# "SigningTable" for more details.
*@example.com hoge._domainkey.example.com
TrustedHostsの作成
EC2
[root@ip-xx-xx-xx-xx opendkim]# cd /etc/opendkim/
[root@ip-xx-xx-xx-xx opendkim]# touch TrustedHosts
[root@ip-xx-xx-xx-xx opendkim]# vi TrustedHosts
内容は変更なし
TrustedHosts
# OPENDKIM TRUSTED HOSTS
# To use this file, uncomment the #ExternalIgnoreList and/or the #InternalHosts
# option in /etc/opendkim.conf then restart OpenDKIM. Additional hosts
# may be added on separate lines (IP addresses, hostnames, or CIDR ranges).
# The localhost IP (127.0.0.1) should always be the first entry in this file.
127.0.0.1
::1
#host.example.com
#192.168.1.0/24
opendkimの起動と有効化
EC2
[root@ip-xx-xx-xx-xx etc]# systemctl daemon-reload
[root@ip-xx-xx-xx-xx etc]# systemctl enable opendkim
[root@ip-xx-xx-xx-xx etc]# systemctl restart opendkim
[root@ip-xx-xx-xx-xx etc]# systemctl status opendkim
DKIMのレコードを追加
AWS Route53など使用しているドメインサービスで該当ドメインにレコードを追加する
レコード名：hoge._domainkey.example.com
形式：TXT
値：/etc/opendkim/keys/hoge.txt
/etc/postfix/mail.cf に以下を追記
/etc/postfix/mail.cf
smtpd_milters = inet:127.0.0.1:8891
non_smtpd_milters = $smtpd_milters
milter_default_action = accept