1POLICYD-SPF(1) General Commands Manual POLICYD-SPF(1)
3
7 policyd-spf - pure-Python Postfix policy daemon for SPF checking
8
10 2.0.0
11
14 NOTE: Depending on the packaging and distribution, the exact path to
15 the executable may vary.
16 $ policyd-spf (Start using installed config file)
18 $ policyd-spf -h (Display usage message)
20 $ policyd-spf /etc/policyd-spf/policyd-spf.conf (Config file name to
22 use)
23 Configuration options are described in the sample configuration file
25 provided with the package (policyd-spf.conf.commented) and in policyd-
26 spf.conf(5). The the configuration file provided with the package can
27 generally be found in /usr/local/etc/policyd-spf/, but installation lo‐
28 cation varies depending on installtion method.
29 Additionally, whitelisting certain IP addresses or IP addresses used by
31 listed domains from SPF checks is supported. Skipping SPF checks for
32 local submission or trusted relays is also provided. The sample con‐
33 figuration file and policyd-spf.conf(5) shows the format to use.
34
37 This documentation assumes you have read Postfix's README_FILES/
38 SMTPD_POLICY_README and are generally familiar with Sender Policy
39 Framework (SPF). See RFC 7208 for details.
40 See man 5 policyd-spf.conf for configuration file information.
42 man 5 policyd-spf.peruser provides documentation on setting up and us‐
44 ing different configuration options on a per user (mail reciepient) ba‐
45 sis.
46
49 python-policyd-spf is a Postfix SMTPd policy daemon for SPF checking.
50 It is implemented in pure Python and uses the pyspf module. The SPF
51 web site is http://www.openspf.org/. The Postfix configuration must be
52 changed to check SPF.
53
56 Logging is sent to syslogd.
57 Each time a Postfix SMTP server process is started it connects to the
59 policy service socket and Postfix runs one instance of this Python
60 script. By default, a Postfix SMTP server process terminates after 100
61 seconds of idle time, or after serving 100 clients. Thus, the cost of
62 starting this Python script is smoothed over time
63 The default policy_time_limit is 1000 seconds. This may be too short
65 for some SMTP transactions to complete. As recommended in SMTPD_POL‐
66 ICY_README, this should be extended to 3600 seconds. To do so, set
67 "policy_time_limit = 3600" in /etc/postfix/main.cf.
68 Messages that get a Fail SPF result will be rejected. Messages that
70 get a Permerror are, by default, treated as if they had no SPF record.
71 Messages that get a Temperror result are, by default, treated as if
72 they had no SPF record, but can (and probably should) be deferred if
73 otherwise permitted. Messages that get other SPF results (Pass, None,
74 Neutral, Softfail) will have the SPF Received header prepended. Note:
75 Spamasassisn 3.2 and follow will use this header for spam scoring so
76 there is no need to configure a separate SPF check in these Spamassas‐
77 sin versions. See Spamassassin documentation for details.
78 Default Mail From rejection/deferal criteria are, by design, conserva‐
80 tive. Default HELO check actions are to reject mail with other than
81 Pass/None. HELO records are much simpler than Mail From records and re‐
82 jecting based on HELO checking does not present a false positive risk.
83 These settings are a matter of local policy and should be adjusted to
84 meet the requirements of site administrators. See policyd-spf.conf(5)
85 for configuration file details.
86
89 Policyd-spf will log messages to syslog about it's activities. The
90 "debugLevel" value in "policyd-spf.conf" can be increased to get addi‐
91 tional information to be logged. When set to a value of "0", only test
92 results (SPF hits/misses) are logged. Results will be returned to
93 Postfix and logged as a warning by Postfix also. For logging by this
94 policy server, look for "policyd-spf" in your mail log files.
95
98 Testing the policy daemon
99 To test the policy daemon by hand, execute:
101 policyd-spf
103 Each query is a bunch of attributes. Order does not matter, and the
105 daemon uses only a few of all the attributes shown below:
106 request=smtpd_access_policy
108 protocol_state=RCPT
109 protocol_name=SMTP
110 helo_name=some.domain.tld
111 queue_id=8045F2AB23
112 instance=12345.6789
113 sender=foo@bar.tld
114 recipient=bar@foo.tld
115 client_address=1.2.3.4
116 client_name=another.domain.tld
117 [empty line]
118 The policy daemon will answer in the same style, with an attribute list
120 followed by a empty line:
121 action=dunno
123 [empty line]
124
127 1. Add the following to /etc/postfix/master.cf:
128 policyd-spf unix - n n - 0
130 spawn
131 user=policyd-spf argv=/usr/bin/policyd-spf
132 NOTE: Check the path to both the installed Python 3 interpreter and
134 policyd-spf. These vary from system to system. To use non-
135 default
136 settings, you must also add the config file (see above and
137 policyd-spf.conf(5) for details). Python and Python 3 ver‐
138 sions
139 prior to 3.3 are not supported.
140 2. Configure the Postfix policy service in /etc/postfix/main.cf:
142 smtpd_recipient_restrictions =
144 ...
145 reject_unauth_destination
146 check_policy_service unix:private/policyd-spf
147 ...
148 policyd-spf_time_limit = 3600
149 policyd-spf_time_limit is an instance of transport_time_limit.
151 See
152 SMTPD_POLICY_README or postconf (5) transport_time_limit for
153 details.
154 NOTE: Specify check_policy_service AFTER reject_unauth_destination
156 or
157 else your system can become an open relay.
158 3. Reload Postfix.
161
164 The time to complete DNS lookups associated with SPF checks is the most
165 significant factor in policy server performance. Use of a capable lo‐
166 cal caching resolver is highly recommended. Specifics of resolver
167 setup are outside the scope of this document.
168 Long waits for DNS answers can cause performance bottlenecks. There
170 are two primary controls, policyd-spf.conf(5) has details, provided to
171 affect DNS timing. Lookup_Time controls the overall time, in seconds,
172 allowed for an SPF check to complete. Whitelist_Lookup_Time controls
173 the amount of time allowed for individual DNS lookups associated with
174 name based whitelist options.
175 Lookup_Time defaults to the 20 second value recommended by RFC 7208.
177 This is a conservative recommendation and often a lower limit works
178 quite well. Delays associated with whitelisting related DNS lookups
179 can be avoided by using IP based options instead.
180 A shorter time increases the likelihood that the result for some mes‐
182 sages will be a temporary error rather then the actual correct result.
183 To avoid some reported interoperability issues with some greylisting
184 implementations, TempError_Defer defaults to False. With TempError_De‐
185 fer set to True, such TempError messages will be deferred and when re‐
186 tried, the responses should be in the local DNS resolver's cache.
187 The combination of a low Lookup_Time setting, TempError_Defer = True,
189 and no DNS name based whitelisting will maximize SPF checking through‐
190 put with only mimimal delays. Consider a value of Lookup_Time = 5 sec‐
191 onds and monitor the system mail logs. If TempError results are rare
192 or non-existent, the value can be lowered. If such result are common
193 (more than 1% of mail), then the value should be raised.
194
197 policyd-spf.conf(5), policyd-spf.peruser(5), python-spf,
198 <http://www.openspf.org>, RFC 7208
199
202 This version of policyd-spf (python) was written by Copyright ©
203 2007-2016 Scott Kitterman <scott@kitterman.com>. It is derived from
204 Tumgreyspf, written by Sean Reifschneider, tummy.com, ltd
205 <jafo@tummy.com>. Portions of the documentation were written by Meng
206 Weng Wong <mengwong@pobox.com>.
207 This man-page was created by Scott Kitterman <scott@kitterman.com>. It
209 is licensed under the same terms as the program.
210 POLICYD-SPF(1)