1Mail::SPF::Iterator(3)User Contributed Perl DocumentationMail::SPF::Iterator(3)
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4

NAME

6       Mail::SPF::Iterator - iterative SPF lookup
7

SYNOPSIS

9           use Net::DNS;
10           use Mail::SPF::Iterator;
11           use Mail::SPF::Iterator Debug =>1; # enable debugging
12           my $spf = Mail::SPF::Iterator->new(
13               $ip,       # IP4|IP6 of client
14               $mailfrom, # from MAIL FROM:
15               $helo,     # from HELO|EHLO
16               $myname,   # optional: my hostname
17               {
18                   default_spf => 'mx/24 ?all', # in case no record was found in DNS
19                   pass_all => SPF_SoftFail,    # treat records like '+all' as error
20                   # rfc4408 => 1,              # for compatibility only
21               }
22           );
23
24           # could be other resolvers too
25           my $resolver = Net::DNS::Resolver->new;
26
27           ### with nonblocking, but still in loop
28           ### (callbacks are preferred with non-blocking)
29           my ($result,@ans) = $spf->next; # initial query
30           while ( ! $result ) {
31               my @query = @ans;
32               die "no queries" if ! @query;
33               for my $q (@query) {
34                   # resolve query
35                   my $socket = $resolver->bgsend( $q );
36                   ... wait...
37                   my $answer = $resolver->bgread($socket);
38                   ($result,@ans) = $spf->next(
39                       $answer                             # valid answer
40                       || [ $q, $resolver->errorstring ]   # or DNS problem
41                   );
42                   last if $result; # got final result
43                   last if @ans;    # got more DNS queries
44               }
45           }
46
47           ### OR with blocking:
48           ### ($result,@ans) = $spf->lookup_blocking( undef,$resolver );
49
50           ### print mailheader
51           print "Received-SPF: ".$spf->mailheader;
52
53           # $result = Fail|Pass|...
54           # $ans[0] = comment for Received-SPF
55           # $ans[1] = %hash with infos for Received-SPF
56           # $ans[2] = explanation in case of Fail
57

DESCRIPTION

59       This module provides an iterative resolving of SPF records. Contrary to
60       Mail::SPF, which does blocking DNS lookups, this module just returns
61       the DNS queries and later expects the responses.
62
63       Lookup of the DNS records will be done outside of the module and can be
64       done in a event driven way. It is also possible to do many parallel SPF
65       checks in parallel without needing multiple threads or processes.
66
67       This module can also make use of SenderID records for checking the
68       "mfrom" part, but it will prefer SPF. It will only use DNS TXT records
69       for looking up SPF policies unless compatibility with RFC 4408 is
70       explicitly enabled.
71
72       See RFC 7208 (old RFC 4408) for SPF and RFC 4406 for SenderID.
73

METHODS

75       new( IP, MAILFROM, HELO, [ MYNAME ], [ \%OPT ] )
76           Construct a new Mail::SPF::Iterator object, which maintains the
77           state between the steps of the iteration. For each new SPF check a
78           new object has to be created.
79
80           IP is the IP if the client as string (IP4 or IP6).
81
82           MAILFROM is the user@domain part from the MAIL FROM handshake, e.g.
83           '<','>' and any parameters removed. If only '<>' was given (like in
84           bounces) the value is empty.
85
86           HELO is the string send within the HELO|EHLO dialog which should be
87           a domain according to the RFC but often is not.
88
89           MYNAME is the name of the local host. It's only used if required by
90           macros inside the SPF record.
91
92           OPT is used for additional arguments. Currently default_spf can be
93           used to set a default SPF record in case no SPF/TXT records are
94           returned from DNS (useful values are for example 'mx ?all' or
95           'mx/24 ?all').  rfc4408 can be set to true in case stricter
96           compatibility is needed with RFC 4408 instead of RFC 7208, i.e.
97           lookup of DNS SPF records, no limit on void DNS lookups etc.
98           pass_all can be set to the expected outcome in case a SPF policy
99           gets found, which would pass everything. Such policies are common
100           used domains used by spammers.
101
102           Returns the new object.
103
104       next([ ANSWER ])
105           "next" will be initially called with no arguments to get initial
106           DNS queries and then will be called with the DNS answers.
107
108           ANSWER is either a DNS packet with the response to a former query
109           or "[ QUERY, REASON ]" on failures, where QUERY is the DNS packet
110           containing the failed query and REASON the reason, why the query
111           failed (like TIMEOUT).
112
113           If a final result was achieved it will return "( RESULT, COMMENT,
114           HASH, EXPLAIN )". RESULT is the result, e.g. "Fail", "Pass",....
115           COMMENT is the comment for the Received-SPF header. HASH contains
116           information about problem, mechanism for the Received-SPF header.
117           EXPLAIN will be set to the explain string if RESULT is Fail.
118
119           If no final result was achieved yet it will either return
120           "(undef,@QUERIES)" with a list of new queries to continue, "('')"
121           in case the ANSWER produced an error but got ignored, because there
122           are other queries open, or "()" in case the ANSWER was ignored
123           because it did not match any open queries.
124
125       mailheader
126           Creates value for Received-SPF header based on the final answer
127           from next().  Returns header as string (one line, no folding) or
128           undef, if no final result was found.  This creates only the value,
129           not the 'Received-SPF' prefix.
130
131       result
132           Returns ( RESULT, COMMENT, HASH, EXPLAIN ) like the final "next"
133           does or () if the final result wasn't found yet.
134
135           If the SPF record had an explain modifier, which needed DNS lookups
136           to resolve this method might return the result (although with
137           incomplete explain) before "next" does it.
138
139       explain_default ( [ EXPLAIN ] )
140           Sets default explanation string if EXPLAIN is given.  If it's
141           called as a class method the default explanation string for the
142           class will be set, otherwise the default explanation string for the
143           object.
144
145           Returns the current default explanation string for the object or if
146           non given or if called as a class method the default explanation
147           string for the class.
148
149       lookup_blocking ( [ TIMEOUT, RESOLVER ] )
150           Quick way to get the SPF status.  This will simply call "next"
151           until it gets a final result.
152
153           TIMEOUT limits the lookup time and defaults to 20.  RESOLVER is a
154           Net::DNS::Resolver object (or similar) and  defaults to
155           "Net::DNS::Resolver->new".  Returns ( RESULT, COMMENT, HASH ) like
156           the final "next" does.
157
158           This is not the preferred way to use this module, because it's
159           blocking, so no lookups can be done in parallel in a single
160           process/thread.
161

EXPORTED SYMBOLS

163       For convenience the constants SPF_TempError, SPF_PermError, SPF_Pass,
164       SPF_Fail, SPF_SoftFail, SPF_Neutral, SPF_None are by default exported,
165       which have the values "TempError", "PermError" ...
166
167   Arguments to "use"/"import"
168       The "SPF_*" symbols are available for import and are exported if no
169       arguments are given to "use" or "import". Same effect with adding
170       ":DEFAULT" as an argument. Additionally the following arguments are
171       supported:
172
173       DebugFunc => \&coderef
174           Sets a custom debug function, which just takes on argument. If
175           given it will be called on all debug messages when debugging is
176           active. This function takes as the only argument the debug message.
177
178       Debug => 1|0
179           Switches debugging on/off.
180

AUTHOR

182       Steffen Ullrich <sullr@cpan.org>
183
185       Copyright by Steffen Ullrich.
186
187       This module is free software; you can redistribute it and/or modify it
188       under the same terms as Perl itself.
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192perl v5.32.1                      2021-01-27            Mail::SPF::Iterator(3)
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