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 accepted: "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 available 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
configuration 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 undefined.
PARAMETERS¶
- AddAllSignatureResults (Boolean)
- If "true", results for all signatures will be
reported by an added Authentication-Results header field. Otherwise, only
one signature will be reported, and which one depends on the
TrustSignaturesFrom setting or, in its absence, which one(s) passed
first or, if none passed, which one was found first during message
processing.
- ADSPAction (string)
- Selects the action to be taken when an ADSP check against a
message with no valid author signature results in the message being deemed
suspicious and discardable. Possible values are "discard"
(accept the mesasge but throw it away) and "reject" (bounce the
message). If not set, discardable messages will still be delivered.
- ADSPNoSuchDomain (Boolean)
- If "true", requests rejection of messages that
are determined to be from nonexistent domains according to the author
domain signing practises (ADSP) test.
- 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.
- AlwaysSignHeaders (dataset)
- Specifies a set of header fields that should be included in
all signature header lists (the "h=" tag) even if they were not
present at the time the signature was generated. The set is empty by
default. The purpose of listing an absent header field is to prevent its
addition between the signer and the verifier, since the verifier would
include that header field if it were added when performing verification,
which would mean the signed message and the verified message were
different and the verification would fail.
- AuthservID (string)
- Sets the "authserv-id" to use when generating the
Authentication-Results: header field after verifying a message. The
default 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
represented ("s" or "S" for seconds, the default;
"m" or "M" for minutes; "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 service running in the background. The default is
"true".
- BaseDirectory (string)
- If set, instructs the filter to change to the specified
directory 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 arranging that any crash
dumps will be saved to a specific location.
- BodyLengthDB (dataset)
- Requests that opendkim include a "l=" body
length tag when the set contains any of the envelope recipient addresses.
The addresses 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 action) and fail (return a "fail" result; this is
the default).
- BogusPolicy (string)
- Instructs the filter to treat an ADSP policy found in an
bogus (forged) DNS record in a special way. Possible values are
apply (apply the policy) and ignore (ignore the policy; 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 specification. The
default is simple. The value may include two different
canonicalizations separated by a slash ("/") character, in which
case the first will be applied to the header and the second to the body.
- ChangeRootDirectory (string)
- Requests that the operating system change the effective
root directory of the process to the one specified here prior to beginning
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
future. 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 diagnosing verification failures. Not recommended for
normal operation.
- 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.
- DisableADSP (Boolean)
- If set, suppresses Author Domain Signing Practices (ADSP)
checks, which require multiple additional DNS queries.
- DKIMReputationFail (integer)
- If the reputation returned by the DNS reputation service
exceeds this value then the result "x-dkim-rep" is set to
"fail". Defaults to 0. (Experimental feature not enabled for
this installation.)
- DKIMReputationPass (integer)
- If the reputation returned by the DNS reputation service is
less than this value then the result "x-dkim-rep" is set to
"pass". Defaults to 0. Values in between
DKIMReputationFail and DKIMReputationPass result in
"x-dkim-rep" being set to "neutral". (Experimental
feature not enabled for this installation.)
- DKIMReputationReject (integer)
- If the reputation returned by the DNS reputation service
exceeds this value then the message is rejected. The default value here is
1001, a deliberately impossible value so that rejections are not enabled
by default. (Experimental feature not enabled for this installation.)
- DKIMReputationRoot (string)
- This is the root directory of the DNS reputation service.
Its interface is defined at http://www.dkim-reputation.org. The default
value here is "al.dkim-reputation.org". A value of
"none" disables the check. (Experimental feature not enabled for
this installation.)
- DNSConnect (Boolean)
- Requests that the asynchronous resolver start using TCP
immediately 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
infinite wait. The default is 5. Ignored if not using an asynchronous
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. The default is "false".
- 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 reason. 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. Basically suppresses the "external host
(hostname) tried to send mail as (domain)" log messages. Entries 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
entire message has been received. This can be used to enact local policy
decisions such as message rejection, quarantine, rerouting, 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.)
- Include (string)
- Names a file to be opened and read as an additional
configuration file. Nesting is allowed to a maximum of five levels.
- InsecureKey (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 (return a
"neutral" result), none (take no special action; this is
the default) and fail (return a "fail" result).
- InsecurePolicy (string)
- Instructs the filter to treat an ADSP policy found in an
insecure (i.e. not protected by DNSSEC) DNS record in a special way.
Possible values are apply (apply the policy; this is the default)
and ignore (ignore the policy).
- 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 address explicitly.
- KeepAuthResults (boolean)
- Suppresses removal of Authentication-Results header fields
containing 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
TemporaryDirectory parameter. Intended only for debugging
verification 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
values: (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
apparent 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 select 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
authenticate to an LDAP server. Requires SASL support be installed on the
local system. There is no default.
- LDAPAuthRealm (string)
- Specifies the authentication realm to use when using SASL
to authenticate to an LDAP server. Requires SASL support be installed on
the local system. There is no default.
- LDAPAuthUser (string)
- Specifies the authenticating user to use when using SASL to
authenticate to an LDAP server. Requires SASL support be installed on the
local system. There is no default.
- LDAPBindPassword (string)
- Specifies the password to use when conducting an LDAP
"bind" operation. There is no default.
- LDAPBindUser (string)
- Specifies the user ID to use when conducting an LDAP
"bind" operation. There is no default.
- 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
before abandoning the connection. If not specified, the LDAP library
default is used.
- LDAPSoftStart (Boolean)
- If set, the inability to bind and authenticate to an LDAP
server will not prevent the filter from starting, and reconnections will
be attempted for each query. The default is "False".
- 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".
- LocalADSP (dataset)
- Allows specification of local ADSP overrides for domains.
This is expected to be a data set with keys and matching values; the keys
are each either a fully-qualified domain name (e.g.
"foo.example.com") or a subdomain name preceded by a period
(e.g. ".example.com"), and the values are either unknown,
all, or discardable, as per the ADSP specification
(RFC5617). This allows local overrides of policies to enforce for domains
that either don't publish ADSP or publish weaker policies than the
verifier would like to enforce.
- LogResults (boolean)
- If logging is enabled (see Syslog below), requests
that the results 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 filter for
checking, the MTA must send it during the protocol exchange. This is
either accomplished via manual configuration of the MTA to send the
desired macros or, for MTA/filter combinations 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
compile the filter and the version of the MTA making the connection.
This data set must be of type "file" or "csl".
- MaximumHeaders (integer)
- Defines the maximum number of bytes the header block of a
message may consume before the filter will reject the message. This
mitigates a denial-of-service attack in which a client connects 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 unspecified 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. Signatures
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. Note that this could cause an author domain signature to be
ignored, causing the ADSP evaluation to fail and, if
SendADSPReports is enabled, a questionable report could be
generated.
- 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. The default is 0.
- Minimum (string)
- Instructs the verification code to fail messages for which
a partial signature was received. There are three possible formats:
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.
Signatures with smaller key sizes, even if they otherwise pass DKIM
validation, will me marked as invalid. The default is 1024, which accepts
all signatures.
- Mode (string)
- Selects operating modes. The string is a concatenation of
characters 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 following combinations must also be set: (a) Domain, KeyFile,
Selector, no KeyTable, no SigningTable; (b) KeyTable, SigningTable, no
Domain, no KeyFile, no Selector; (c) KeyTable, SetupPolicyScript, 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 SendADSPReports and
SendReports. The default is /usr/sbin/sendmail. The executable
should accept typical sendmail(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 error.
- 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
covered 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.
- 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 specification (RFC6376, Section 5.4)
as "SHOULD NOT" be signed; the default 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
entire 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
validate. 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 accept. Note that the "t" (testing) flag in a DKIM key
does not alter this behaviour; even keys marked as test keys whose
signatures fail will still be subjected to the selected 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
followed by specific overrides.
- On-DNSError (string)
- Selects the action to be taken when a transient DNS error
is encountered. Possible values are the same as those for
On-BadSignature. 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
signature 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-PolicyError (string)
- Selects the action to be taken when a an attempt to
retrieve and evaluate the author domain's signing policy (ADSP) is
unsuccessful. 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.
- OversignHeaders (dataset)
- Specifies a set of header fields that should be included in
all signature header lists (the "h=" tag) even if they were
present at the time the signature was generated. The set is empty by
default. The purpose of listing an absent header field is to prevent its
addition between the signer and the verifier, since the verifier would
include that header field if it were added when performing verification,
which would mean the signed message and the verified message were
different and the verification would fail. Unlike
AlwaysSignHeaders, the names in this data set are always added to
signatures even if they did appear in the original header field set. Note
that the fields in this list must also be present in the
SignHeaders list, or any signature produced will be impossible to
validate. (Note: Feature is experimental.)
- PeerList (dataset)
- Identifies a set of "peers" that identifies
clients whose connections 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
("!") character 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
connection type. More precise entries are preferred over less precise
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.
- 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 installation.)
- 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. (Not enabled for this installation.)
- RemoveARAll (Boolean)
- Removes all Authentication-Results: header fields that also
satisfy 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 delivery.
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 experimental.)
- 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 local MTAs.
This can be used to accommodate expected changes such as are 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 '#' character 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
outgoing reports (see SendReports and SendADSPReports
below). If not specified, the executing user and local hostname will be
used to construct the address.
- ReportBccAddress (string)
- Specifies address(es) to include in a Bcc: header field on
outgoing reports (see SendReports and SendADSPReports
below). If multiple addresses are required, they should be comma
separated.
- RequestReports (boolean)
- When signing, includes a request for signature evaluation
failures in the signature. (See draft-ietf-marf-dkim-reporting 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 indicates whether or not all mail should be signed (if set)
versus only verified mail being signed (if not set). The default is
"false". (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 message 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.)
- ResolvConf (string)
- Specifies a file from which a list of nameservers should be
read when doing DNS queries and applying the DNSSEC protocol. The file
should be formatted as described in resolv.conf(5). See the
documentation at http://unbound.net for details.
- ResolverTracing (Boolean)
- Requests resolver tracing features be enabled, if
available. The effect of this depends on how debugging features of the
resolver 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 particular,
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 that certain signatures be
ignored based on that information. 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
messages. 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.
- SelectorHeader (string)
- Names a header field whose contents name the key to use
when signing. The referenced key must appear in the KeyTable.
@SELECTOR_HEADER_MANNOTICE@
- SelectorHeaderRemove (Boolean)
- Remove the SelectorHeader before signing.
@SELECTOR_HEADER_MANNOTICE@
- SendADSPReports (Boolean)
- If true, when a policy evaluation fails and the signing
site advertises a reporting address (i.e. r=user in its policy
record) and a request for reports of such failures, the filter will send a
structured report to that address containing details of the incident.
- 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 verifying a
message to determine the origin domain (for policy checks), and when
signing for deciding which signing request(s) to make. By default, the
DKIM library's internal list is used, which consists solely of the
"From" header field. See the OmitHeaders setting for a
description of possible values.
- SenderMacro (string)
- Use the milter macro string to determine the sender of the
message. (Experimental feature not enabled for this installation.)
- SendReports (Boolean)
- If true, when a signature verification fails and the
signing site advertises a reporting address (i.e. r=user in its
policy record) and a request for reports of such failures, the filter will
send a structured report to that address containing details needed to
reproduce the problem.
- 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 signatures.
- 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 implicitly added. By
default, those fields listed in the DKIM specification 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 contains a name found in the
KeyTable (see above) that identifies which key should be used in
generating the signature, and an optional 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
replaced by the domain found in the From: header field. Similarly, 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 superdomains
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
MultipleSignatures is enabled in which case all matches are
applied.
- Socket (string)
- Specifies the socket that should be established by the
filter to receive connections from sendmail(8) in order to provide
service. socketspec is in one of two forms: local:path,
which creates 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 address must be
enclosed in square brackets. This option is mandatory either in the
configuration file or on the command line.
- Statistics (filename)
- This specifies a file in which to store DKIM transaction
statistics. See opendkim-stats(8) for a mechanism to parse the
file's contents, and opendkim-importstats() for a mechanism to
translate 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
gethostname(3) is used. (Note: Feature is experimental.)
- StatisticsPrefix (string)
- When AnonymousStatistics is enabled, this string may
be specified 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 facility names are the same as the ones allowed in
syslog.conf(5). The default is "mail".
- SyslogSuccess (Boolean)
- Log via calls to syslog(3) additional entries
indicating successful signing or verification of messages.
- TemporaryDirectory (string)
- Specifies the directory in which temporary canonicalization
files should be written. The default is to use the libdkim default
location, currently /var/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 during
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. See the
Unbound documentation 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
creation. 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.
- UnboundConfigFile (string)
- Specifies a configuration file to be passed to the Unbound
library that performs DNS queries applying the DNSSEC protocol. See the
Unbound documentation at http://unbound.net for the expected content of
this file. The results of using this and the TrustAnchorFile
setting at the same time are undefined.
- UserID (string)
- Attempts to become the specified userid before starting
operations. 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 experimental.)
- VBR-TrustedCertifiers (string)
- A colon or comma sparated list of trusted certifiers to
accept when verifying VBR-Info header field. (Note: Feature is
experimental.)
- VBR-TrustedCertifiersOnly (Boolean)
- By default, the certifiers that are in both the trusted
certifiers 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, which makes later ADSP checks impossible.
- X-Header (Boolean)
- Causes opendkim to add an "X-DKIM" header
field indicating the presence of this filter in the path of the message
from injection 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 verify mode is enabled and configuration
would otherwise have caused the message to be signed, then it will not
have this header field added).
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 interaction
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 2.6.8 of
opendkim.
COPYRIGHT¶
Copyright (c) 2007, 2008, Sendmail, Inc. and its suppliers. All rights reserved.
Copyright (c) 2009-2012, The OpenDKIM Project. All rights reserved.
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