opendkim.conf(5) File Formats Manual opendkim.conf(5)
NAME
opendkim.conf - Configuration file for opendkim
LOCATION
/etc/opendkim.conf
DESCRIPTION
opendkim(8) implements the DKIM specification for signing and verifying
e-mail messages on a per-domain basis. This file is its configuration
file.
Blank lines are ignored. Lines containing a hash ("#") character are
truncated at the hash character to allow for comments in the file.
Other content should be the name of a parameter, followed by white
space, followed by the value of that parameter, each on a separate
line.
For parameters that are Boolean in nature, only the first byte of the
value is processed. For positive values, the following are accepted:
"T", "t", "Y", "y", "1". For negative values, the following are ac-
cepted: "F", "f", "N", "n", "0".
Many, but not all, of these parameters are also available as command
line options to opendkim(8). However, new parameters are generally not
added as command line options so the complete set of options is avail-
able here, and thus use of the configuration file is encouraged. In
some future release, the set of available command line options is
likely to get trimmed.
See the opendkim(8) man page for details about how and when the config-
uration file contents are reloaded.
Some of these parameters are listed as having a type of "dataset". See
the opendkim(8) man page for a description of such parameters.
Unless otherwise stated, Boolean values default to "false", integer
values default to 0, and string and dataset values default to being un-
defined.
PARAMETERS
AllowSHA1Only (Boolean)
Permit verify mode when only SHA1 support is available. RFC6376
requires that verifiers implement both SHA1 and SHA256 support.
Setting this feature changes the absence of SHA256 support from
an error to a warning.
AlwaysAddARHeader (Boolean)
Add an "Authentication-Results:" header field even to unsigned
messages from domains with no "signs all" policy. The reported
DKIM result will be "none" in such cases. Normally unsigned
mail from non-strict domains does not cause the results header
field to be added.
AuthservID (string)
Sets the "authserv-id" to use when generating the Authentica-
tion-Results: header field after verifying a message. The de-
fault is to use the name of the MTA processing the message. If
the string "HOSTNAME" is provided, the name of the host running
the filter (as returned by the gethostname(3) function) will be
used.
AuthservIDWithJobID (Boolean)
If "true", requests that the authserv-id portion of the added
Authentication-Results: header fields contain the job ID of the
message being evaluated.
AutoRestart (Boolean)
Automatically re-start on failures. Use with caution; if the
filter fails instantly after it starts, this can cause a tight
fork(2) loop.
AutoRestartCount (integer)
Sets the maximum automatic restart count. After this number of
automatic restarts, the filter will give up and terminate. A
value of 0 implies no limit; this is the default.
AutoRestartRate (string)
Sets the maximum automatic restart rate. If the filter begins
restarting faster than the rate defined here, it will give up
and terminate. This is a string of the form n/t[u] where n is
an integer limiting the count of restarts in the given interval
and t[u] defines the time interval through which the rate is
calculated; t is an integer and u defines the units thus repre-
sented ("s" or "S" for seconds, the default; "m" or "M" for min-
utes; "h" or "H" for hours; "d" or "D" for days). For example,
a value of "10/1h" limits the restarts to 10 in one hour. There
is no default, meaning restart rate is not limited.
Background (Boolean)
Causes opendkim to fork and exits immediately, leaving the ser-
vice running in the background. The default is "true".
BaseDirectory (string)
If set, instructs the filter to change to the specified direc-
tory using chdir(2) before doing anything else. This means any
files referenced elsewhere in the configuration file can be
specified relative to this directory. It's also useful for ar-
ranging that any crash dumps will be saved to a specific loca-
tion.
BodyLengthDB (dataset)
Requests that opendkim include a "l=" body length tag when the
set contains any of the envelope recipient addresses. The ad-
dresses presented are tested against the database in various
forms as described under the SigningTable setting (below). This
feature of the protocol exists to improve the likelihood that a
signature will survive transit through a mailing list server, as
they commonly append footers to messages. Note, however, that
this creates a potential security issue since someone could add
arbitrary text to the signed message and the signature would
still validate. See the DKIM specification for details.
BogusKey (string)
Instructs the filter to treat a passing signature associated
with a bogus (forged) key in a special way. Possible values are
neutral (return a "neutral" result), none (take no special ac-
tion) and fail (return a "fail" result; this is the default).
CaptureUnknownErrors (Boolean)
When set, and on systems where MTA quarantine is available, the
filter will request quarantine of a message that results in an
internal error or resource exhaustion.
Canonicalization (string)
Selects the canonicalization method(s) to be used when signing
messages. When verifying, the message's DKIM-Signature: header
field specifies the canonicalization method. The recognized
values are relaxed and simple as defined by the DKIM specifica-
tion. The default is simple. The value may include two differ-
ent canonicalizations separated by a slash ("/") character, in
which case the first will be applied to the header and the sec-
ond to the body.
ChangeRootDirectory (string)
Requests that the operating system change the effective root di-
rectory of the process to the one specified here prior to begin-
ning execution. chroot(2) requires superuser access. A warning
will be generated if UserID is not also set.
ClockDrift (integer)
Sets the tolerance in seconds to be applied when determining
whether a signature was either expired or generated in the fu-
ture. The default is 300.
Diagnostics (Boolean)
Requests the inclusion of "z=" tags in signatures, which encode
the original header field set for use by verifiers when diagnos-
ing verification failures. Not recommended for normal opera-
tion.
DiagnosticDirectory (string)
Directory into which to write diagnostic reports when message
verification fails on a message bearing a "z=" tag. If not set
(the default), these files are not generated.
DisableCryptoInit (Boolean)
If set, skips initialization of the SSL library initialization
steps, which are normally required in multi-threaded environ-
ments. This assumes some other library opendkim is using will
do the required initialization and shutdown.
DNSConnect (Boolean)
Requests that the asynchronous resolver start using TCP immedi-
ately rather than using UDP until TCP is actually needed. Does
not work with all resolvers.
DNSTimeout (integer)
Sets the DNS timeout in seconds. A value of 0 causes an infi-
nite wait. The default is 5. Ignored if not using an asynchro-
nous resolver package. See also the NOTES section below.
Domain (dataset)
A set of domains whose mail should be signed by this filter.
Mail from other domains will be verified rather than being
signed.
This parameter is not required if a SigningTable is in use; in
that case, the list of signed domains is implied by the lines in
that file.
This parameter is ignored if a KeyTable is defined.
DomainKeysCompat (boolean)
If set, backward compatibility with DomainKeys (RFC4870) key
records is enabled. When not set, such keys are considered to
be syntactically invalid.
DontSignMailTo (dataset)
A set of e-mail address, mail to which should never be signed by
the filter. Note that this is an "any" feature; if any one of
the recipients of the message matches a member of this list, the
message will not be signed.
EnableCoredumps (boolean)
On systems that have such support, make an explicit request to
the kernel to dump cores when the filter crashes for some rea-
son. Some modern UNIX systems suppress core dumps during
crashes for security reasons if the user ID has changed during
the lifetime of the process. Currently only supported on Linux.
ExemptDomains (dataset)
Specifies a set of domains, mail from which should be ignored
entirely by the filter. This is similar to the PeerList setting
except that it bases its decision on the sender of the message
as identified from the header fields or other message data, not
the identity of the SMTP client sending the message.
ExternalIgnoreList (dataset)
Identifies a set of "external" hosts that may send mail through
the server as one of the signing domains without credentials as
such. This has the effect of suppressing the "external host
(hostname) tried to send mail as (domain)" log messages. En-
tries in the data set should be of the same form as those of the
PeerList option below. The set is empty by default.
FinalPolicyScript (string)
Gives the name of a Lua script that should be run after the en-
tire message has been received. This can be used to enact local
policy decisions such as message rejection, quarantine, rerout-
ing, etc. based on signatures found on the message, the results
of attempts to verify them, and other properties of the message
or signatures. See opendkim-lua(3) for details.
FixCRLF (Boolean)
Requests that the DKIM library convert bare CRs and LFs to CRLFs
during body canonicalization, anticipating that an MTA somewhere
before delivery will do that conversion anyway. The default is
to leave them as-is.
IdentityHeader (string)
This specifies the header field where an identity is stored.
(Experimental feature not enabled for this installation.)
IdentityHeaderRemove (Boolean)
Remove the IdentityHeader after signing. (Experimental feature
not enabled for this installation.)
IgnoreMalformedMail (boolean)
Silently passes malformed messages without alteration. This in-
cludes messages that fail the RequiredHeaders check, if enabled.
The default is to pass those messages but add an Authentication-
Results field indicating that they were malformed.
Include (string)
Names a file to be opened and read as an additional configura-
tion file. Nesting is allowed to a maximum of five levels.
InternalHosts (dataset)
Identifies a set internal hosts whose mail should be signed
rather than verified. Entries in this data set follow the same
form as those of the PeerList option below. If not specified,
the default of "127.0.0.1" is applied. Naturally, providing a
value here overrides the default, so if mail from 127.0.0.1
should be signed, the list provided here should include that ad-
dress explicitly.
KeepAuthResults (boolean)
Suppresses removal of Authentication-Results header fields con-
taining DKIM results apparently added by this filter (usually
the result of a misconfiguration or a forgery).
KeepTemporaryFiles (boolean)
Instructs the filter to create temporary files containing the
header and body canonicalizations of messages that are signed or
verified. The location of these files can be set using the Tem-
poraryDirectory parameter. Intended only for debugging verifi-
cation problems.
KeyFile (string)
Gives the location of a PEM-formatted private key to be used for
signing all messages. Ignored if a KeyTable is defined.
KeyTable (dataset)
Gives the location of a file mapping key names to signing keys.
If present, overrides any KeyFile setting in the configuration
file. The data set named here maps each key name to three val-
ues: (a) the name of the domain to use in the signature's "d="
value; (b) the name of the selector to use in the signature's
"s=" value; and (c) either a private key or a path to a file
containing a private key. If the first value consists solely of
a percent sign ("%") character, it will be replaced by the ap-
parent domain of the sender when generating a signature. If the
third value starts with a slash ("/") character, or "./" or
"../", then it is presumed to refer to a file from which the
private key should be read, otherwise it is itself a PEM-encoded
private key or a base64-encoded DER private key; a "%" in the
third value in this case will be replaced by the apparent domain
name of the sender. The SigningTable (see below) is used to se-
lect records from this table to be used to add signatures based
on the message sender.
LDAPAuthMechanism (string)
Names the authentication mechanism to use when connecting to an
LDAP server. The default is the empty string, meaning "simple"
authentication should be done.
LDAPAuthName (string)
Specifies the authenticating name to use when using SASL to au-
thenticate to an LDAP server. Requires SASL support be in-
stalled on the local system. There is no default.
LDAPAuthRealm (string)
Specifies the authentication realm to use when using SASL to au-
thenticate to an LDAP server. Requires SASL support be in-
stalled on the local system. There is no default.
LDAPAuthUser (string)
Specifies the authenticating user to use when using SASL to au-
thenticate to an LDAP server. Requires SASL support be in-
stalled on the local system. There is no default.
LDAPBindPassword (string)
Specifies the password to use when conducting an LDAP "bind" op-
eration. There is no default.
LDAPBindUser (string)
Specifies the user ID to use when conducting an LDAP "bind" op-
eration. There is no default.
LDAPDisableCache (Boolean)
Suppresses creation of a local cache in front of LDAP queries.
LDAPKeepaliveIdle (integer)
Sets the number of seconds a connection to an LDAP server needs
to remain idle before TCP starts sending keepalive probes. If
not specified, the LDAP library default is used.
LDAPKeepaliveInterval (integer)
Sets the interval in seconds between TCP keepalive probes. If
not specified, the LDAP library default is used.
LDAPKeepaliveProbes (integer)
Sets the maximum number of keepalive probes TCP should send be-
fore abandoning the connection. If not specified, the LDAP li-
brary default is used.
LDAPTimeout (integer)
Sets the time in seconds after which an LDAP operation should be
abandoned. The default is 5.
LDAPUseTLS (Boolean)
Indicates whether or not a TLS connection should be established
when contacting an LDAP server. The default is "False".
LogResults (boolean)
If logging is enabled (see Syslog below), requests that the re-
sults of evaluation of all signatures that were at least partly
intact (i.e., the "d=", "s=", and "b=" tags could be extracted).
LogWhy (boolean)
If logging is enabled (see Syslog below), issues very detailed
logging about the logic behind the filter's decision to either
sign a message or verify it. The logic behind the decision is
non-trivial and can be confusing to administrators not familiar
with its operation. A description of how the decision is made
can be found in the OPERATIONS section of the opendkim(8) man
page. This causes a large increase in the amount of log data
generated for each message, so it should be limited to debugging
use and not enabled for general operation.
MacroList (dataset)
Defines a set of MTA-provided macros that should be checked to
see if the sender has been determined to be a local user and
therefore whether or not the message should be signed. If a
value is specified matching a macro name in the data set, the
value of the macro must match a value specified (matching is
case-sensitive), otherwise the macro must be defined but may
contain any value. The set is empty by default, meaning macros
are not considered when making the sign-verify decision. The
general format of the value is value1[|value2[|...]]; if one or
more value is defined then the macro must be set to one of the
listed values, otherwise the macro must be set but can contain
any value.
In order for the macro and its value to be available to the fil-
ter for checking, the MTA must send it during the protocol ex-
change. This is either accomplished via manual configuration of
the MTA to send the desired macros or, for MTA/filter combina-
tions that support the feature, the filter can request those
macros that are of interest. The latter is a feature negotiated
at the time the filter receives a connection from the MTA and
its availability depends upon the version of milter used to com-
pile the filter and the version of the MTA making the connec-
tion.
This data set must be of type "file" or "csl".
MaximumHeaders (integer)
Defines the maximum number of bytes the header block of a mes-
sage may consume before the filter will reject the message.
This mitigates a denial-of-service attack in which a client con-
nects to the MTA and begins feeding an unbounded number of
header fields of arbitrary size; since the filter keeps a cache
of these, the attacker could cause the filter to allocate an un-
specified amount of memory. The default is 65536; a value of 0
removes the limit.
MaximumSignaturesToVerify (integer)
Defines the maximum number of signatures on a message for which
verification should be conducted. The default is three. Signa-
tures are selected from the top of the message downward. If
TrustSignaturesFrom is set, signatures from domains in that data
set are always verified, which may consume part or all of, or
even exceed, this limit.
MaximumSignedBytes (integer)
Specifies the maximum number of bytes of message body to be
signed. Messages shorter than this limit will be signed in
their entirety. Setting this value implies use of BodyLengthDB
for all addresses.
MilterDebug (integer)
Sets the debug level to be requested from the milter library.
Currently, the highest meaningful value is 6.
Minimum (string)
Instructs the verification code to fail messages for which a
partial signature was received. There are three possible for-
mats: min indicating at least min bytes of the message must be
signed (or if the message is smaller than min then all of it
must be signed); min% requiring that at least min percent of the
received message must be signed; and min+ meaning there may be
no more than min bytes of unsigned data appended to the message
for it to be considered valid.
MinimumKeyBits (integer)
Establishes a minimum key size for acceptable signatures. Sig-
natures with smaller key sizes, even if they otherwise pass DKIM
validation, will me marked as invalid. The default is 1024. A
value of 0 accepts all keys.
Mode (string)
Selects operating modes. The string is a concatenation of char-
acters that indicate which mode(s) of operation are desired.
Valid modes are s (signer) and v (verifier). The default is sv
except in test mode (see the opendkim(8) man page) in which case
the default is v. When signing mode is enabled, one of the fol-
lowing combinations must also be set: (a) Domain, KeyFile, Se-
lector, no KeyTable, no SigningTable; (b) KeyTable, Sign-
ingTable, no Domain, no KeyFile, no Selector; (c) KeyTable, Se-
tupPolicyScript, no Domain, no KeyFile, no Selector.
MTA (dataset)
A set of MTA names (a la the sendmail(8) DaemonPortOptions Name
parameter) whose mail should be signed by this filter. There is
no default, meaning MTA name is not considered when making the
sign-verify decision.
MTACommand (string)
Specifies the path to an executable to be used for sending mail
such as that generated by SendReports. The default is
/usr/sbin/sendmail. The executable should accept typical send-
mail(8) command line options "-t" (take addresses from message
body) and "-f" (set envelope sender), accept the new message on
its standard input, and return a non-zero exit status on any er-
ror.
MultipleSignatures (Boolean)
Allow addition of multiple signatures when a signing table is in
use. See SigningTable for more information.
MustBeSigned (dataset)
Specifies a set of header fields that, if present, must be cov-
ered by the DKIM signature when verifying a message. If a
header field in this set is present in the message and is not
signed, the filter will treat even an otherwise valid signature
as invalid. The default is an empty list.
Nameservers (string)
Provides a comma-separated list of IP addresses that are to be
used when doing DNS queries to retrieve DKIM keys, VBR records,
etc. These override any local defaults built in to the resolver
in use, which may be defined in /etc/resolv.conf or hard-coded
into the software.
NoHeaderB (Boolean)
If set, this feature suppresses the use of "header.b" tags in
added Authentication-Results header fields. The default is
"false", which means those tags will be applied.
OmitHeaders (dataset)
Specifies a set of header fields that should be omitted when
generating signatures. If an entry in the list names any header
field that is mandated by the DKIM specification, the entry is
ignored. A set of header fields is listed in the DKIM specifi-
cation (RFC6376, Section 5.4) as "SHOULD NOT" be signed; the de-
fault list for this parameter contains those fields (Return-
Path, Received, Comments, Keywords, Bcc, Resent-Bcc and DKIM-
Signature). To omit no headers, simply use the string "." (or
any string that will match no header field names). Specifying a
list with this parameter replaces the default entirely, unless
one entry is "*" in which case the list is interpreted as a
delta to the default; for example, "*,+foobar" will use the en-
tire default list plus the name "foobar", while "*,-Bcc" would
use the entire default list except for the "Bcc" entry.
On-BadSignature (string)
Selects the action to be taken when a signature fails to vali-
date. Possible values (with abbreviated forms in parentheses):
accept (a) accept the message; discard (d) discard the message;
quarantine (q) quarantine the message; reject (r) reject the
message; tempfail (t) temp-fail the message. The default is ac-
cept. Note that the "t" (testing) flag in a DKIM key bypasses
this behaviour; a bad signature that references a testing flag
will still be delivered, though the added Authentication-Results
field will indicate both the failed result and the test mode so
that consumers of the message can take appropriate action.
On-Default (string)
Selects the action to be taken when any verification or internal
error of any kind is encountered. This is processed before the
other "On-" values so it can be used as a blanket setting fol-
lowed by specific overrides.
On-DNSError (string)
Selects the action to be taken when a transient DNS error is en-
countered. Possible values are the same as those for On-BadSig-
nature. The default is tempfail.
On-InternalError (string)
Selects the action to be taken when an internal error of some
kind is encountered. Possible values are the same as those for
On-BadSignature. The default is tempfail.
On-KeyNotFound (string)
Selects the action to be taken when the key referenced by a sig-
nature is not present in the DNS. Possible values are the same
as those for On-BadSignature. The default is accept.
On-NoSignature (string)
Selects the action to be taken when a message arrives unsigned.
Possible values are the same as those for On-BadSignature. The
default is accept.
On-Security (string)
Selects the action to be taken when a message arrives containing
properties that may be a security concern. Possible values are
the same as those for On-BadSignature. The default is tempfail.
On-SignatureError (string)
Selects the action to be taken when a message cannot be signed
because of issues with the message or the key provided for sign-
ing. Possible values are the same as those for On-BadSignature.
The default is reject.
OversignHeaders (dataset)
Specifies a set of header fields that should be included in all
signature header lists (the "h=" tag) once more than the number
of times they were actually present in the signed message. The
set is empty by default. The purpose of this, and especially of
listing an absent header field, is to prevent the addition of
important fields between the signer and the verifier. Since the
verifier would include that header field when performing verifi-
cation if it had been added by an intermediary, the signed mes-
sage and the verified message were different and the verifica-
tion would fail. Note that listing a field name here and not
listing it in the SignHeaders list is likely to generate invalid
signatures.
PeerList (dataset)
Identifies a set of "peers" that identifies clients whose con-
nections should be accepted without processing by this filter.
The set should contain on each line a hostname, domain name
(e.g. ".example.com"), IP address, an IPv6 address (including an
IPv4 mapped address), or a CIDR-style IP specification (e.g.
"192.168.1.0/24"). An entry beginning with a bang ("!") charac-
ter means "not", allowing exclusions of specific hosts that are
otherwise members of larger sets. Host and domain names are
matched first, then the IP or IPv6 address depending on the con-
nection type. More precise entries are preferred over less pre-
cise ones, i.e. "192.168.1.1" will match before
"!192.168.1.0/24". The text form of IPv6 addresses will be
forced to lowercase when queried (RFC5952), so the contents of
this data set should also use lowercase. The IP address portion
of an entry may optionally contain square brackets; both forms
(with and without) will be checked.
PidFile (string)
Specifies the path to a file that should be created at process
start containing the process ID.
POPDBFile (dataset)
Requests that the filter consult a set for IP addresses that
should be allowed for signing. This feature was designed for
POP-before-SMTP datastores. (Not enabled for this installa-
tion.)
Quarantine (Boolean)
Requests that messages which fail verification be quarantined by
the MTA. (Requires a sufficiently recent version of the milter
library.)
QueryCache (Boolean)
Instructs the DKIM library to maintain its own local cache of
keys and policies retrieved from DNS, rather than relying on the
nameserver for caching service. Useful if the nameserver being
used by the filter is not local.
RedirectFailuresTo (address)
Messages bearing signatures that failed to verify are redirected
to the specified address. The original envelope recipient set
is recorded in the header before redirection occurs. By de-
fault, no redirection is done.
RemoveARAll (Boolean)
Removes all Authentication-Results: header fields that also sat-
isfy the requirements of RemoveARFrom below. By default, only
those containing a DKIM result are removed.
RemoveARFrom (dataset)
Defines a set of hostnames whose Authentication-Results: header
fields should be removed before the message is passed for deliv-
ery. By default only those header fields matching the local
host's canonical name will be removed. Matching is only done on
full hostnames (e.g. "host.example.com") or on domain names
(e.g. ".example.com").
RemoveOldSignatures (Boolean)
Removes all existing signatures when operating in signing mode.
ReplaceHeaders (data set)
Defines a set of header fields that should be affected by the
text replacement rules defined by the ReplaceRules setting. By
default, all header fields are included. (Note: Feature is ex-
perimental.)
ReplaceRules (string)
Specifies a file containing a list of text replacement rules
that are applied to the message header fields to replace certain
content expected to be changed as the message passes through lo-
cal MTAs. This can be used to accommodate expected changes such
as those made to From: fields by MTA "masquerade" features.
Each entry in the file consists of a POSIX regular expression,
followed by a tab (ASCII 9), followed by the text that should be
used to replace the text matching the expression. The '#' char-
acter denotes the beginning of a comment and text from that
point on in a single line is ignored. Blank lines are also
skipped. (Note: Feature is experimental.)
ReportAddress (string)
Specifies the string to use in the From: header field for outgo-
ing reports (see SendReports below). If not specified, the exe-
cuting user and local hostname will be used to construct the ad-
dress.
ReportBccAddress (string)
Specifies address(es) to include in a Bcc: header field on out-
going reports (see SendReports below). If multiple addresses are
required, they should be comma separated.
RequestReports (boolean)
When signing, includes a request for signature evaluation fail-
ures in the signature. (See RFC6651 for details.)
RequiredHeaders (boolean)
Checks all messages for compliance with RFC5322 header field
count requirements. Non-compliant messages are rejected.
RequireSafeKeys (boolean)
When reading a key file, a message will be logged if the key
file has the read or write bit set other than for the owner or
for a group that the executing process is in. With this feature
set to "true", the filter will further consider this an error
and refuse to make use of the file's contents. The default is
"true".
ResignAll (boolean)
Where ResignMailTo triggers a re-signing action, this flag indi-
cates whether or not all mail should be signed (if set) versus
only verified mail being signed (if not set). (Experimental
feature not enabled for this installation.)
ResignMailTo (dataset)
Checks each message recipient against the specified dataset for
a matching record. The full address is checked in each case,
then the hostname, then each domain preceded by ".". If there
is a match, the value returned is presumed to be the name of a
key in the KeyTable (if defined) to be used to re-sign the mes-
sage in addition to verifying it. If there is a match without a
KeyTable, the default key is applied. (Experimental feature not
enabled for this installation.)
ResolverConfiguration (string)
Provides the given string as configuration information to the
underlying resolver. For the standard UNIX resolver, this is
unused; for Unbound, the string contains a filename that is con-
sidered to be a configuration file. There is no default.
ResolverTracing (Boolean)
Requests resolver tracing features be enabled, if available.
The effect of this depends on how debugging features of the re-
solver might be implemented. Currently only effective with the
OpenDKIM asynchronous resolver library.
ScreenPolicyScript (string)
Gives the name of a Lua script that should be run after all of
the header fields have been processed for a message; in particu-
lar, this is useful after all DKIM signatures have been detected
and initial evaluation has been done. The script has access to
all of the header fields and connection information and can di-
rect that certain signatures be ignored based on that informa-
tion. See opendkim-lua(3) for details.
SelectCanonicalizationHeader (string)
Defines a header field name which, if present, adjusts which
canonicalization will be used to generate an outgoing signature.
Overrides the Canonicalization setting if the header field is
present. The default is "X-Canonicalization".
Selector (string)
Defines the name of the selector to be used when signing mes-
sages. See the DKIM specification for details. Used only when
signing with a single key; see the SigningTable parameter below
for more information.
This parameter is ignored if a KeyTable is defined.
SenderHeaders (dataset)
Specifies an ordered list of header fields that should be
searched to determine the sender of a message. The first header
field found is the one whose value is used. This is mainly used
when signing for deciding which signing request(s) to make. By
default, the "From" header field is the only one checked. See
the OmitHeaders setting for a description of possible values.
SenderMacro (string)
Use the milter macro string to determine the sender of the mes-
sage. (Note: Feature is experimental.)
SendReports (Boolean)
If true, when a signature verification fails and the signature
included a reporting request ("r=y") and the signing domain ad-
vertises a reporting address (i.e. ra=user) in a reporting
record in the DNS, the filter will send a structured report to
that address containing details needed to reproduce the problem.
See RFC6651 for a complete description of this mechanism.
SetupPolicyScript (string)
Gives the name of a Lua script that should be run once all
header fields for a message have arrived. The script has access
to all of the header fields and connection information and can
request DKIM verification or signing based on that information.
See opendkim-lua(3) for details.
SignatureAlgorithm (string)
Selects the signing algorithm to use when generating signatures.
Use 'opendkim -V' to see the list of supported algorithms. The
default is rsa-sha256 if it is available, otherwise it will be
rsa-sha1.
SignatureTTL (integer)
Sets the time-to-live, in seconds, of signatures generated by
the filter. If not set, no expiration time is added to signa-
tures.
SignHeaders (dataset)
Specifies the set of header fields that should be included when
generating signatures. If the list omits any header field that
is mandated by the DKIM specification, those fields are implic-
itly added. By default, those fields listed in the DKIM speci-
fication as "SHOULD" be signed (RFC6376, Section 5.4) will be
signed by the filter. See the OmitHeaders configuration option
for more information about the format and interpretation of this
field.
SigningTable (dataset)
Defines a table used to select one or more signatures to apply
to a message based on the address found in the From: header
field. Keys in this table vary depending on the type of table
used; values in this data set should include one field that con-
tains a name found in the KeyTable (see above) that identifies
which key should be used in generating the signature, and an op-
tional second field naming the signer of the message that will
be included in the "i=" tag in the generated signature. Note
that the "i=" value will not be included in the signature if it
conflicts with the signing domain (the "d=" value).
If the first field contains only a "%" character, it will be re-
placed by the domain found in the From: header field. Simi-
larly, within the optional second field, any "%" character will
be replaced by the domain found in the From: header field.
If this table specifies a regular expression file ("refile"),
then the keys are wildcard patterns that are matched against the
address found in the From: header field. Entries are checked in
the order in which they appear in the file.
For all other database types, the full user@host is checked
first, then simply host, then user@.domain (with all superdo-
mains checked in sequence, so "foo.example.com" would first
check "user@foo.example.com", then "user@.example.com", then
"user@.com"), then .domain, then user@*, and finally *.
In any case, only the first match is applied, unless MultipleS-
ignatures is enabled in which case all matches are applied.
SMTPURI (string)
Specifies a URI (e.g., "smtp://localhost") to which mail should
be sent via SMTP when notifications are generated. (Not enabled
for this installation.)
Socket (string)
Specifies the socket that should be established by the filter to
receive connections from sendmail(8) in order to provide ser-
vice. socketspec is in one of two forms: local:path, which cre-
ates a UNIX domain socket at the specified path, or
inet:port[@host] or inet6:port[@host] which creates a TCP socket
on the specified port and in the specified protocol family. If
the host is not given as either a hostname or an IP address, the
socket will be listening on all interfaces. A literal IP ad-
dress must be enclosed in square brackets. This option is
mandatory either in the configuration file or on the command
line.
SoftStart (Boolean)
If set, the inability to connect and authenticate to an LDAP or
SQL server will not prevent the filter from starting, and recon-
nections will be attempted for each query. The default is
"False".
SoftwareHeader (Boolean)
Causes opendkim to add an "DKIM-Filter" header field indicating
the presence of this filter in the path of the message from in-
jection to delivery. The product's name, version, and the job
ID are included in the header field's contents. Note that the
header field is not added if the Mode setting causes the message
to be ignored (e.g., if only signing mode is enabled and the
configuration causes the message not to be signed, or only ver-
ify mode is enabled and configuration would otherwise have
caused the message to be signed, then it will not have this
header field added).
Statistics (filename)
This specifies a file in which to store DKIM transaction statis-
tics. See opendkim-stats(8) for a mechanism to parse the file's
contents, and opendkim-importstats() for a mechanism to trans-
late the file's contents into SQL database insertions. (Note:
Feature is experimental.)
StatisticsName (string)
Defines the name to be used as the reporting host in statistics
logs. By default, the local host's name returned by gethost-
name(3) is used. (Note: Feature is experimental.)
StatisticsPolicyScript (string)
The statistics script is run after all of the DKIM verification
and signing work has been completed but before any final message
handling is done. The main purpose of this script is to give
the user an opportunity to examine the message or its signatures
and make arbitrary additional statistical observations that
should be recorded by the statistics module.
StatisticsPrefix (string)
When AnonymousStatistics is enabled, this string may be speci-
fied and will be prepended to all data before hashing for more
complete anonymization. This means two records from different
sources referencing the same source will still produce different
hashes, meaning such correlation is now only possible within the
data from a single repoter.
StrictHeaders (Boolean)
If set, instructs the DKIM library to refuse processing of a
message if the header field count does not conform to RFC5322
Section 3.6.
StrictTestMode (Boolean)
Selects strict CRLF mode during testing (see the -t command line
flag in the opendkim(8) man page); messages for which all header
fields and body lines are not CRLF-terminated are considered
malformed and will produce an error.
SubDomains (Boolean)
Sign subdomains of those listed by the Domain parameter as well
as the actual domains.
Syslog (Boolean)
Log via calls to syslog(3) any interesting activity.
SyslogFacility (string)
Log via calls to syslog(3) using the named facility. The facil-
ity names are the same as the ones allowed in syslog.conf(5).
The default is "mail".
SyslogName (string)
Log via calls to syslog(3) using that name. That way one could
distinguish multiple instances. The default is the name of the
executable, normally "opendkim".
SyslogSuccess (Boolean)
Log via calls to syslog(3) additional entries indicating suc-
cessful signing or verification of messages.
TemporaryDirectory (string)
Specifies the directory in which temporary canonicalization
files should be written. The default is to use the libopendkim
default location, currently /tmp.
TestDNSData (data set)
Provides a data set whose keys will be treated as DNS record
names and values as TXT record contents. Intended for use dur-
ing automated testing.
TestPublicKeys (string)
Names a file from which public keys should be read. Intended
for use only during automated testing.
TrustAnchorFile (string)
Specifies a file from which trust anchor data should be read
when doing DNS queries and applying the DNSSEC protocol. This
is currently ignored unless the underlying library is compiled
to use Unbound; see the documentation at at http://unbound.net
for the expected format of this file.
TrustSignaturesFrom (dataset)
This value consists of a set of domains that are considered
trustworthy in terms of third-party signatures. That is, if a
message arrives with a signature from a domain that doesn't
match the domain in the From: header, this setting determines
whether or not that signature will be trusted. If this value is
undefined, all signatures are trusted.
UMask (integer)
Requests a specific permissions mask to be used for file cre-
ation. This only really applies to creation of the socket when
Socket specifies a UNIX domain socket, and to the PidFile (if
any); temporary files are created by the mkstemp(3) function
that enforces a specific file mode on creation regardless of the
process umask. See umask(2) for more information.
UnprotectedKey (string)
Instructs the filter to treat a passing signature associated
with a key found in an insecure (i.e. not protected by DNSSEC)
DNS record in a special way. Possible values are neutral (re-
turn a "neutral" result), none (take no special action; this is
the default) and fail (return a "fail" result).
UserID (string)
Attempts to become the specified userid before starting opera-
tions. The value is of the form userid[:group]. The process
will be assigned all of the groups and primary group ID of the
named userid unless an alternate group is specified.
VBR-Certifiers (string)
The default certifiers if not specified in X-VBR-Certifiers
header field. (Note: Feature is experimental.)
VBR-PurgeFields (string)
If set, arranges to remove X-VBR-Certifiers and X-VBR-Type
fields on messages prior to sending them. (Note: Feature is ex-
perimental.)
VBR-TrustedCertifiers (string)
A colon or comma sparated list of trusted certifiers to accept
when verifying VBR-Info header field. (Note: Feature is experi-
mental.)
VBR-TrustedCertifiersOnly (Boolean)
By default, the certifiers that are in both the trusted certi-
fiers list (above) and those in the message's VBR-Info header
field will be checked for vouching. With this option set, the
trusted certifiers will be checked and the ones claimed by the
message will be ignored. (Note: Feature is experimental.)
VBR-Type (string)
This default VBR type if not specified in the X-VBR-Type header
field. (Note: Feature is experimental.)
WeakSyntaxChecks (Boolean)
Requests that the library continue processing messages even if
syntax errors are discovered early in message analysis. This
means, for example, that a signed message with a mangled From:
field will still proceed to verification even if the author's
domain could not be determined.
NOTES
When using DNS timeouts (see the DNSTimeout option above), be sure not
to use a timeout that is larger than the timeout being used for inter-
action between sendmail and the filter. Otherwise, the MTA could abort
a message while waiting for a reply from the filter, which in turn is
still waiting for a DNS reply.
Features that involve specification of IPv4 addresses or CIDR blocks
will use the inet_addr(3) function to parse that information. Users
should be familiar with the way that function handles the non-trivial
cases (for example, "192.0.2/24" and "192.0.2.0/24" are not the same
thing).
FILES
/etc/opendkim.conf
Default location of this file.
VERSION
This man page covers version 2.11.0 of opendkim.
COPYRIGHT
Copyright (c) 2007, 2008, Sendmail, Inc. and its suppliers. All rights
reserved.
Copyright (c) 2009-2015, The Trusted Domain Project. All rights re-
served.
SEE ALSO
opendkim(8), opendkim-lua(3), sendmail(8)
RFC5451 - Message Header Field for Indicating Message Authentication
Status
RFC5617 - DKIM Author Domain Signing Practises
RFC5965 - An Extensible Format for Email Feedback Reports
RFC6008 - Authentication-Results Registration for Differentiating among
Cryptographic Results
RFC6376 - DomainKeys Identified Mail
RFC6651 - Extensions to DomainKeys Identified Mail (DKIM) for Failure
Reporting
The Trusted Domain Project opendkim.conf(5)
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