Friday, February 19, 2010

Access List for qmail-smtpd

One of the feature that IndiMail adds to qmail-smtpd is accesslist between senders and recipients. Accesslist can be enabled by creating a control file /etc/indimail/control/accesslist. A line in accesslist is of the form
type:sender:recipient
where type is either the word 'from' or 'rcpt'. sender and recipient can be the actual sender, recipient, a wildcard or a regular expression (uses regex(3))
The accesslist happens at SMTP and mails which get restricted get rejected with permanent 5xx code.
To give some examples
rcpt:ceo@indimail.org:country_distribution_list@indimail.org
rcpt:md@indimail.org:country_distribution_list@indimail.org
from:recruiter@gmail.com:hr_manager@indimail.org

The above accesslist implies that only the users with email ceo@indimail.org and md@indimail.org can send a mail to the email country_distribution_list@indimail.org
The 3rd line implies that all outside mails from the sender recruiter@gmail.com will be rejected at SMTP unless the recipient is hr_manager@indimail.org
IndiMail also provides a program called uacl to test this accesslist. uacl is useful especially when you use wildcards or regular expressions.
An extreme example where you want to restrict the communication between two domains only
% cat /etc/indimail/control/accesslist
rcpt:*example.com:*@example1.com
from:*@example1.com:*@example.com


% uacl test@example.com test@example1.com
rule no 1: rcpt:*example.com:*@example1.com
matched recipient [test@example1.com] with [*@example1.com]
matched sender [test@example.com] with [*example.com] --
> access allowed
%
% uacl test@indimail.org test@example1.com
rule no 1: rcpt:*example.com:*@example1.com
matched recipient [test@example1.com] with [*@example1.com]
sender not matched [test@indimail.org] --
> access denied
%
% uacl test@example1.com test@example.com
rule no 2: from:*@example1.com:*@example.com
matched sender [test@example1.com] with [*@example1.com]
matched recipient [test@example.com] with [*@example.com] --
> access allowed
%
% uacl test@example1.com mbhangui@gmail.com
rule no 2: from:*@example1.com:*@example.com
matched sender [test@example1.com] with [*@example1.com]
recipient not matched [mbhangui@gmail.com] --
> access denied
%



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