add dkimHeader struct

dkimHeader.go

@@ -0,0 +1,182 @@
+package dkim
+
+import (
+	"time"
+)
+
+type DkimHeader struct {
+	// Version  This tag defines the version of DKIM
+	// specification that applies to the signature record.
+	// tag v
+	Version string
+
+	// The algorithm used to generate the signature..
+	// Verifiers MUST support "rsa-sha1" and "rsa-sha256";
+	// Signers SHOULD sign using "rsa-sha256".
+	// tag a
+	Algorithm string
+
+	// The signature data (base64).
+	// Whitespace is ignored in this value and MUST be
+	// ignored when reassembling the original signature.
+	// In particular, the signing process can safely insert
+	// FWS in this value in arbitrary places to conform to line-length
+	// limits.
+	// tag b
+	SignatureData string
+
+	// The hash of the canonicalized body part of the message as
+	// limited by the "l=" tag (base64; REQUIRED).
+	// Whitespace is ignored in this value and MUST be ignored when reassembling the original
+	// signature.  In particular, the signing process can safely insert
+	// FWS in this value in arbitrary places to conform to line-length
+	// limits.
+	// tag bh
+	BodyHash string
+
+	// Message canonicalization (plain-text; OPTIONAL, default is
+	//"simple/simple").  This tag informs the Verifier of the type of
+	// canonicalization used to prepare the message for signing.  It
+	// consists of two names separated by a "slash" (%d47) character,
+	// corresponding to the header and body canonicalization algorithms,
+	// respectively.  These algorithms are described in Section 3.4.  If
+	// only one algorithm is named, that algorithm is used for the header
+	// and "simple" is used for the body.  For example, "c=relaxed" is
+	// treated the same as "c=relaxed/simple".
+	// tag c
+	MessageCanonicalization string
+
+	// The SDID claiming responsibility for an introduction of a message
+	//  into the mail stream (plain-text; REQUIRED).  Hence, the SDID
+	//  value is used to form the query for the public key.  The SDID MUST
+	// correspond to a valid DNS name under which the DKIM key record is
+	// published.  The conventions and semantics used by a Signer to
+	// create and use a specific SDID are outside the scope of this
+	// specification, as is any use of those conventions and semantics.
+	// When presented with a signature that does not meet these
+	// requirements, Verifiers MUST consider the signature invalid.
+	// Internationalized domain names MUST be encoded as A-labels, as
+	// described in Section 2.3 of [RFC5890].
+	// tag d
+	Domain string
+
+	// Signed header fields (plain-text, but see description; REQUIRED).
+	// A colon-separated list of header field names that identify the
+	// header fields presented to the signing algorithm.  The field MUST
+	// contain the complete list of header fields in the order presented
+	// to the signing algorithm.  The field MAY contain names of header
+	// fields that do not exist when signed; nonexistent header fields do
+	// not contribute to the signature computation (that is, they are
+	// treated as the null input, including the header field name, the
+	// separating colon, the header field value, and any CRLF
+	// terminator).  The field MAY contain multiple instances of a header
+	// field name, meaning multiple occurrences of the corresponding
+	// header field are included in the header hash.  The field MUST NOT
+	// include the DKIM-Signature header field that is being created or
+	// verified but may include others.  Folding whitespace (FWS) MAY be
+	// included on either side of the colon separator.  Header field
+	// names MUST be compared against actual header field names in a
+	// case-insensitive manner.  This list MUST NOT be empty.  See
+	// Section 5.4 for a discussion of choosing header fields to sign and
+	// Section 5.4.2 for requirements when signing multiple instances of
+	// a single field.
+	// tag h
+	Headers []string
+
+	// The Agent or User Identifier (AUID) on behalf of which the SDID is
+	// taking responsibility (dkim-quoted-printable; OPTIONAL, default is
+	// an empty local-part followed by an "@" followed by the domain from
+	// the "d=" tag).
+	// The syntax is a standard email address where the local-part MAY be
+	// omitted.  The domain part of the address MUST be the same as, or a
+	// subdomain of, the value of the "d=" tag.
+	// Internationalized domain names MUST be encoded as A-labels, as
+	// described in Section 2.3 of [RFC5890].
+	// tag i
+	Auid string
+
+	// Body length count (plain-text unsigned decimal integer; OPTIONAL,
+	// default is entire body).  This tag informs the Verifier of the
+	// number of octets in the body of the email after canonicalization
+	// included in the cryptographic hash, starting from 0 immediately
+	// following the CRLF preceding the body.  This value MUST NOT be
+	// larger than the actual number of octets in the canonicalized
+	// message body.  See further discussion in Section 8.2.
+	// tag l
+	BodyLength uint
+
+	// A colon-separated list of query methods used to retrieve the
+	// public key (plain-text; OPTIONAL, default is "dns/txt").  Each
+	// query method is of the form "type[/options]", where the syntax and
+	// semantics of the options depend on the type and specified options.
+	// If there are multiple query mechanisms listed, the choice of query
+	// mechanism MUST NOT change the interpretation of the signature.
+	// Implementations MUST use the recognized query mechanisms in the
+	// order presented.  Unrecognized query mechanisms MUST be ignored.
+	// Currently, the only valid value is "dns/txt", which defines the
+	// DNS TXT resource record (RR) lookup algorithm described elsewhere
+	// in this document.  The only option defined for the "dns" query
+	// type is "txt", which MUST be included.  Verifiers and Signers MUST
+	// support "dns/txt".
+	// tag q
+	QueryMethods []string
+
+	// The selector subdividing the namespace for the "d=" (domain) tag
+	// (plain-text; REQUIRED).
+	// Internationalized selector names MUST be encoded as A-labels, as
+	// described in Section 2.3 of [RFC5890].
+	// tag s
+	Selector string
+
+	// Signature Timestamp (plain-text unsigned decimal integer;
+	// RECOMMENDED, default is an unknown creation time).  The time that
+	// this signature was created.  The format is the number of seconds
+	// since 00:00:00 on January 1, 1970 in the UTC time zone.  The value
+	// is expressed as an unsigned integer in decimal ASCII.  This value
+	// is not constrained to fit into a 31- or 32-bit integer.
+	// Implementations SHOULD be prepared to handle values up to at least
+	// 10^12 (until approximately AD 200,000; this fits into 40 bits).
+	// To avoid denial-of-service attacks, implementations MAY consider
+	// any value longer than 12 digits to be infinite.  Leap seconds are
+	// not counted.  Implementations MAY ignore signatures that have a
+	// timestamp in the future.
+	// tag t
+	SignatureTimestamp time.Time
+
+	// Signature Expiration (plain-text unsigned decimal integer;
+	// RECOMMENDED, default is no expiration).  The format is the same as
+	// in the "t=" tag, represented as an absolute date, not as a time
+	// delta from the signing timestamp.  The value is expressed as an
+	// unsigned integer in decimal ASCII, with the same constraints on
+	// the value in the "t=" tag.  Signatures MAY be considered invalid
+	// if the verification time at the Verifier is past the expiration
+	// date.  The verification time should be the time that the message
+	// was first received at the administrative domain of the Verifier if
+	// that time is reliably available; otherwise, the current time
+	// should be used.  The value of the "x=" tag MUST be greater than
+	// the value of the "t=" tag if both are present.
+	//tag x
+	SignatureExpiration time.Time
+
+	// Copied header fields (dkim-quoted-printable, but see description;
+	// OPTIONAL, default is null).  A vertical-bar-separated list of
+	// selected header fields present when the message was signed,
+	// including both the field name and value.  It is not required to
+	// include all header fields present at the time of signing.  This
+	// field need not contain the same header fields listed in the "h="
+	// tag.  The header field text itself must encode the vertical bar
+	// ("|", %x7C) character (i.e., vertical bars in the "z=" text are
+	// meta-characters, and any actual vertical bar characters in a
+	// copied header field must be encoded).  Note that all whitespace
+	// must be encoded, including whitespace between the colon and the
+	// header field value.  After encoding, FWS MAY be added at arbitrary
+	// locations in order to avoid excessively long lines; such
+	// whitespace is NOT part of the value of the header field and MUST
+	// be removed before decoding.
+	// The header fields referenced by the "h=" tag refer to the fields
+	// in the [RFC5322] header of the message, not to any copied fields
+	// in the "z=" tag.  Copied header field values are for diagnostic
+	// use.
+	// tag z
+	CopiedHeaderFileds []string
+}