NAME
postfix-policyd-spf-perl - pure-Perl Postfix policy server for SPF
checking
VERSION
2.007
USAGE
Usage:
policyd-spf-perl [-v]
OTHER DOCUMENTATION
This documentation assumes you have read Postfix’s README_FILES/
SMTPD_POLICY_README.
SYNOPSIS
postfix-policyd-spf-perl is a Postfix SMTP policy server for SPF
checking. It is implemented in pure Perl and uses the Mail::SPF CPAN
module. Note that Mail::SPF is a complete re-implementation of SPF
based on the final SPF RFC, RFC 4408. It shares no code with the older
Mail::SPF::Query that was the original SPF development implementation.
This version of the policy server always checks HELO before Mail From
(older versions just checked HELO if Mail From was null). It will
reject mail that fails either Mail From or HELO SPF checks. It will
defer mail if there is a temporary SPF error and the message would
othersise be permitted (DEFER_IF_PERMIT). If the HELO check produces a
REJECT/DEFER result, Mail From will not be checked.
If the message is not rejected or deferred, the policy server will
PREPEND the appropriate SPF Received header. If Mail From is anything
other than completely empty (i.e. <>) then the Mail From result will be
used for SPF Received (e.g. Mail From None even if HELO is Pass).
The policy server skips SPF checks for connections from the localhost
(127.) and instead prepends and logs ’SPF skipped - localhost is always
allowed.’ If you have relays that you want to skip SPF checks for, you
can add them to relay_addresses on line 78 using standard CIDR notation
in a space separated list. For these addresses, ’X-Comment: SPF
skipped for whitelisted relay’ is prepended and logged.
Error conditions within the policy server (that don’t result in a
crash) or from Mail::SPF will return DUNNO.
DESCRIPTION
Logging is sent to syslogd.
Each time a Postfix SMTP server process is started it connects to the
policy service socket and Postfix runs one instance of this Perls
script. By default, a Postfix SMTP server process terminates after 100
seconds of idle time, or after serving 100 clients. Thus, the cost of
starting this Perl script is smoothed over time.
The default policy_time_limit is 1000 seconds. This may be too short
for some SMTP transactions to complete. As recommended in
SMTPD_POLICY_README, this should be extended to 3600 seconds. To do
so, set "policy_time_limit = 3600" in /etc/postfix/main.cf.
TESTING THE POLICY DAEMON
Testing the policy daemon
To test the policy daemon by hand, execute:
% /usr/sbin/postfix-policyd-spf-perl
Each query is a bunch of attributes. Order does not matter, and the
server uses only a few of all the attributes shown below:
request=smtpd_access_policy
protocol_state=RCPT
protocol_name=SMTP
helo_name=some.domain.tld
queue_id=
instance=71b0.45e2f5f1.d4da1.0
sender=foo@bar.tld
recipient=bar@foo.tld
client_address=1.2.3.4
client_name=another.domain.tld
[empty line]
The policy daemon will answer in the same style, with an attribute list
followed by a empty line:
action=550 Please see
http://www.openspf.org/Why?id=foo@bar.tld&ip=1.2.3.4&
receiver=bar@foo.tld
[empty line]
To test HELO checking sender should be empty:
sender=
... More attributes...
[empty line]
If you want more detail in the system logs change $VERBOSE to 1.
POSTFIX INTEGRATION
1. Add the following to /etc/postfix/master.cf:
spfcheck unix - n n - 0 spawn
user=policyd-spf argv=/usr/sbin/postfix-policyd-spf-perl
2. Configure the Postfix SPF policy service in /etc/postfix/main.cf:
smtpd_recipient_restrictions =
...
reject_unauth_destination
check_policy_service unix:private/spfcheck
...
policy_time_limit = 3600
NOTE: Specify check_policy_service AFTER reject_unauth_destination
or
else your system can become an open relay.
3. Set up machines which you expect to legitimately forward mail to
this
server (see description in synopsis). This should typically
include
the IP addresses which backup Mail eXchangers, and known non-SRS
forwarders will use to submit mail to this server (i.e. the source
IPs
of the other servers).
4. Restart Postfix.
5. Verify correct backup MX operation (if applicable).
SEE ALSO
libmail-spf-perl, <http://www.openspf.org>
AUTHORS
This version of policyd-spf-perl was written by Meng Weng Wong
<mengwong+spf@pobox.com> and updated for libmail-spf-perl by Scott
Kitterman <scott@kitterman.com> and Julian Mehnle <julian@mehnle.net>.
This man-page was written by Scott Kitterman <scott@kitterman.com>.
2008-07-25 postfix-policyd-spf-perl(1)