Difference between revisions of "OpenDKIM"

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(Updated with key generation using opendkim built in program "opendkim-genkey".)
(Move to mail server.)
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[[Category:Internet Applications]]
+
[[Category:Mail Server]]
 
DomainKeys Identified Mail is a digital email signing/verification technology, which is already supported by some common mail providers. (For example yahoo, google, etc).
 
DomainKeys Identified Mail is a digital email signing/verification technology, which is already supported by some common mail providers. (For example yahoo, google, etc).
  
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For more info see [http://tools.ietf.org/html/rfc6376 RFC 6376]
 
For more info see [http://tools.ietf.org/html/rfc6376 RFC 6376]
  
= Installation =
+
== Installation ==
  
 
Install [https://aur.archlinux.org/packages.php?ID=47389 opendkim]
 
Install [https://aur.archlinux.org/packages.php?ID=47389 opendkim]
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== Basic configuration ==
 
== Basic configuration ==
 
* Generate key:
 
* Generate key:
<pre>
+
opendkim-genkey -r -s server1 -d example.com
opendkim-genkey -r -s server1 -d example.com
+
</pre>
+
 
* Create /etc/opendkim/opendkim.conf (see example in the same directory)
 
* Create /etc/opendkim/opendkim.conf (see example in the same directory)
 
Minimal config:
 
Minimal config:
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master.cf example:
 
master.cf example:
<pre>
 
smtp      inet  n      -      n      -      -      smtpd
 
    -o smtpd_client_connection_count_limit=10
 
    -o smtpd_milters=inet:127.0.0.1:8891
 
  
submission inet n      -      n      -      -      smtpd
+
smtp      inet  n      -      n      -      -      smtpd
  -o smtpd_enforce_tls=no
+
  -o smtpd_client_connection_count_limit=10
  -o smtpd_sasl_auth_enable=yes
+
  -o smtpd_milters=inet:127.0.0.1:8891
  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
+
  -o smtpd_sasl_path=smtpd
+
submission inet n      -      n      -      -      smtpd
  -o cyrus_sasl_config_path=/etc/sasl2
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  -o smtpd_enforce_tls=no
  -o smtpd_milters=inet:127.0.0.1:8891
+
  -o smtpd_sasl_auth_enable=yes
</pre>
+
  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
 +
  -o smtpd_sasl_path=smtpd
 +
  -o cyrus_sasl_config_path=/etc/sasl2
 +
  -o smtpd_milters=inet:127.0.0.1:8891
  
 
== Notes ==
 
== Notes ==
 
While you're about to fight spam and increase people's trust in your server, you might want to take a look at [http://de.wikipedia.org/wiki/Sender_Policy_Framework Sender Policy Framework], which basically means adding a DNS Record stating which servers are authorized to send email for your domain.
 
While you're about to fight spam and increase people's trust in your server, you might want to take a look at [http://de.wikipedia.org/wiki/Sender_Policy_Framework Sender Policy Framework], which basically means adding a DNS Record stating which servers are authorized to send email for your domain.

Revision as of 08:33, 31 August 2012

DomainKeys Identified Mail is a digital email signing/verification technology, which is already supported by some common mail providers. (For example yahoo, google, etc).

The idea

Basically DKIM means digitally singing all messages on the server to verify the message actually was sent from the domain in question and is not spam or pishing (and has not been modified).

  • The sender's mail server signs outgoing email with the private key.
  • When the message arrives, the receiver (or his server) requests the public key from the domain's DNS and verifies the signature.

This ensures the message was sent from a server who's private key matches the domain's public key.

For more info see RFC 6376

Installation

Install opendkim

You may add user for opendkim or use existing one (for example: postfix)

Basic configuration

  • Generate key:
opendkim-genkey -r -s server1 -d example.com
  • Create /etc/opendkim/opendkim.conf (see example in the same directory)

Minimal config:

 Domain                  example.com
 KeyFile                 /path/to/keys/server1.private
 Selector                server1
 Socket                  inet:8891@localhost
 UserID                  opendkim
  • Add a DNS TXT record with your selector and public key. The correct record is generated with the private key and can be found in "server1.txt" in the same location as the private key.
  • Run it with /etc/rc.d/opendkim start or add it to DAEMONS in /etc/rc.conf

Postfix integration

Just add

 non_smtpd_milters=inet:127.0.0.1:8891

and/or

 smtpd_milters=inet:127.0.0.1:8891

into main.cf or smtpd options in master.cf

master.cf example:

smtp      inet  n       -       n       -       -       smtpd
  -o smtpd_client_connection_count_limit=10
  -o smtpd_milters=inet:127.0.0.1:8891

submission inet n       -       n       -       -       smtpd
  -o smtpd_enforce_tls=no
  -o smtpd_sasl_auth_enable=yes
  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
  -o smtpd_sasl_path=smtpd
  -o cyrus_sasl_config_path=/etc/sasl2
  -o smtpd_milters=inet:127.0.0.1:8891

Notes

While you're about to fight spam and increase people's trust in your server, you might want to take a look at Sender Policy Framework, which basically means adding a DNS Record stating which servers are authorized to send email for your domain.