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3 .\" Copyright (c) 2019 Martijn van Duren <martijn@openbsd.org>
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17 .Dd $Mdocdate$
18 .Dt FILTER-DKIMSIGN 8
19 .Os
20 .Sh NAME
21 .Nm filter-dkimsign
22 .Nd add dkim signature to messages
23 .Sh SYNOPSIS
24 .Nm
25 .Op Fl tz
26 .Op Fl a Ar algorithm
27 .Op Fl c Ar canonicalization
28 .Op Fl h Ar headers
29 .Op Fl x Ar seconds
30 .Fl d Ar domain
31 .Fl k Ar file
32 .Fl s Ar selector
33 .Sh DESCRIPTION
34 .Nm
35 adds a dkim signature to the message.
36 The following flags are supported:
37 .Bl -tag -width Ds
38 .It Fl a Ar algorithm
39 The algorithm to use.
40 This implementation only supports rsa cryptography.
41 Only sha256 should be used for hashing, since other algorithms are most likely
42 not supported by verifiers.
43 Defaults to
44 .Ar rsa-sha256 .
45 .It Fl c Ar canonicalization
46 The canonicalization algorithm used to sign the messge.
47 Defaults to
48 .Ar simple/simple .
49 .It Fl d Ar domain
50 The
51 .Ar domain
52 where the public key can be found.
53 This option can be specified multiple times to select the best
54 .Ar domain
55 during signing.
56 If specified multiple times it looks at the domain component of the first
57 mailbox in the from-header and tries to find a match.
58 If no exact match can be found it looks for the closest parent
59 .Ar domain .
60 If no matches can be the first
61 .Ar domain
62 specified will be used.
63 .It Fl h Ar headers
64 The email headers which are included in the mail signature.
65 Per RFC this option requires at least the from header to be included.
66 The headers are specified by separating them with a colon.
67 The default is
68 from:reply-to:subject:date:to:cc:resent-date:resent-from:resent-to:resent-cc:in-reply-to:references:list-id:list-help:list-unsubscribe:list-subscribe:list-post:list-owner:list-archive .
69 .It Fl k Ar file
70 .Ar file
71 should point to a file containing the RSA private key to sign the messages.
72 .It Fl s Ar selector
73 The selector within the _domainkey subdomain of
74 .Ar domain
75 where the public key can be found.
76 .It Fl t
77 Add the time of signing to the dkim header.
78 .It Fl x Ar seconds
79 Add the amount of
80 .Ar seconds
81 the signature is valid to the dkim header.
82 .It Fl z
83 Add the mail headers used in the dkim signature to the dkim header.
84 If a second
85 .Fl z
86 is specified all headers will be included in the dkim header.
87 Useful for debugging purposes.
88 .El
89 .Sh SEE ALSO
90 .Xr smtpd 8