README
¶
go-dkim
Fork of toorop's DKIM with non-pointer API and bugfixes.
Getting started
Install
go get github.com/andres-erbsen/go-dkim
Warning: you need to use Go 1.4.2-master or 1.4.3 (when it will be available) see https://github.com/golang/go/issues/10482 fro more info.
Sign email
import (
dkim "github.com/andres-erbsen/go-dkim"
)
func main(){
// email is the email to sign (byte slice)
// privateKey the private key (pem encoded, byte slice )
dkim := dkim.NewDkim()
options := dkim.NewSigOptions()
options.PrivateKey = privateKey
options.Domain = "mydomain.tld"
options.Selector = "myselector"
options.SignatureExpireIn = 3600
options.BodyLength = 50
options.Headers = []string{"from", "date", "mime-version", "received", "received"}
options.AddSignatureTimestamp = true
options.Canonicalization = "relaxed/relaxed"
err := dkim.Sign(&email, options)
// handle err..
}
Verify
import (
dkim "github.com/toorop/go-dkim"
)
func main(){
// email is the email to verify (byte slice)
dkim := dkim.NewDkim()
_, err := dkim.Verify(email)
}
Todo
- handle z tag (copied header fields used for diagnostic use)
- handle multiple dns records
Documentation
¶
Overview ¶
Package dkim provides tools for signing and verify a email according to RFC 6376
Index ¶
Constants ¶
View Source
const ( CRLF = "\r\n" TAB = " " FWS = CRLF + TAB MaxHeaderLineLength = 70 )
Variables ¶
View Source
var ( // ErrSignPrivateKeyRequired when there not private key in config ErrSignPrivateKeyRequired = errors.New("PrivateKey is required") // ErrSignDomainRequired when there is no domain defined in config ErrSignDomainRequired = errors.New("Domain is required") // ErrSignSelectorRequired when there is no Selcteir defined in config ErrSignSelectorRequired = errors.New("Selector is required") // ErrSignHeaderShouldContainsFrom If Headers is specified it should at least contain 'from' ErrSignHeaderShouldContainsFrom = errors.New("header must contains 'from' field") // ErrSignBadCanonicalization If bad Canonicalization parameter ErrSignBadCanonicalization = errors.New("bad Canonicalization parameter") // ErrCandNotParsePrivateKey when unable to parse private key ErrCandNotParsePrivateKey = errors.New("can not parse private key, check format (pem) and validity") // ErrSignBadAlgo Bad algorithm ErrSignBadAlgo = errors.New("bad algorithm. Only rsa-sha1 or rsa-sha256 are permitted") // ErrBadMailFormat unable to parse mail ErrBadMailFormat = errors.New("bad mail format") // ErrBadMailFormatHeaders bad headers format (not DKIM Header) ErrBadMailFormatHeaders = errors.New("bad mail format found in headers") // ErrDkimHeaderBadFormat when errors found in DKIM header ErrDkimHeaderBadFormat = errors.New("bad DKIM header format") // ErrDkimHeaderNotFound when there's no DKIM-Signature header in an email we have to verify ErrDkimHeaderNotFound = errors.New("no DKIM-Signature header field found ") // ErrDkimHeaderBTagNotFound when there's no b tag ErrDkimHeaderBTagNotFound = errors.New("no tag 'b' found in dkim header") // ErrDkimHeaderNoFromInHTag when from is missing in h tag ErrDkimHeaderNoFromInHTag = errors.New("'from' header is missing in h tag") // ErrDkimHeaderMissingRequiredTag when a required tag is missing ErrDkimHeaderMissingRequiredTag = errors.New("signature missing required tag") // ErrDkimHeaderDomainMismatch if i tag is not a sub domain of d tag ErrDkimHeaderDomainMismatch = errors.New("domain mismatch") // ErrDkimVersionNotsupported version not supported ErrDkimVersionNotsupported = errors.New("incompatible version") // ErrVerifyBodyHash when body hash doesn't verify ErrVerifyBodyHash = errors.New("body hash did not verify") // ErrVerifyNoKeyForSignature no key ErrVerifyNoKeyForSignature = errors.New("no key for verify") // This error may be temporary in some cases. ErrVerifyKeyUnavailable = errors.New("key unavailable") // ErrVerifyTagVMustBeTheFirst if present the v tag must be the firts in the record ErrVerifyTagVMustBeTheFirst = errors.New("pub key syntax error: v tag must be the first") // ErrVerifyVersionMusBeDkim1 if présent flag v (version) must be DKIM1 ErrVerifyVersionMusBeDkim1 = errors.New("flag v must be set to DKIM1") // ErrVerifyBadKeyType bad type for pub key (only rsa is accepted) ErrVerifyBadKeyType = errors.New("bad type for key type") // ErrVerifyRevokedKey key(s) for this selector is revoked (p is empty) ErrVerifyRevokedKey = errors.New("revoked key") // ErrVerifyBadKey when we can't parse pubkey ErrVerifyBadKey = errors.New("unable to parse pub key") // ErrVerifyNoKey when no key is found on DNS record ErrVerifyNoKey = errors.New("no public key found in DNS TXT") // ErrVerifySignatureHasExpired when signature has expired ErrVerifySignatureHasExpired = errors.New("signature has expired") // ErrVerifyInappropriateHashAlgo when h tag in pub key doesn't contain hash algo from a tag of DKIM header ErrVerifyInappropriateHashAlgo = errors.New("inappropriate has algorithm") // ErrTesting ErrTesting = errors.New("public key has testing flag set") )
Functions ¶
Types ¶
type DKIMHeader ¶
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
CopiedHeaderFields []string
// RawForsign represents the raw part (without canonicalization) of the header
// used for computint sig in verify process
RawForSign string
}
DKIMHeader
type DefaultSigner ¶
type DefaultSigner struct {
PrivateKey *rsa.PrivateKey
}
type PubKey ¶
type PubKey struct {
Version string
HashAlgo []string
KeyType string
Note string
PubKey rsa.PublicKey
ServiceType []string
FlagTesting bool // flag y
FlagIMustBeD bool // flag i
Selector string
}
pubKeyRep represents a parsed version of public key record
type SigOptions ¶
type SigOptions struct {
// DKIM version (default 1)
Version uint
// Private key used for signing (required)
PrivateKey []byte
// Domain (required)
Domain string
// Selector (required)
Selector string
// The Agent of User IDentifier
Auid 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.
Canonicalization string
// The algorithm used to generate the signature
//"rsa-sha1" or "rsa-sha256"
Algo string
// Signed header fields
Headers []string
// Body length count( if set to 0 this tag is ommited in Dkim header)
BodyLength uint
// Query Methods used to retrieve the public key
QueryMethods []string
// Add a signature timestamp
AddSignatureTimestamp bool
// Time validity of the signature (0=never)
SignatureExpireIn uint64
// CopiedHeaderFileds
CopiedHeaderFields []string
}
sigOptions represents signing options
Source Files
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