add struct for pubkey representation

dkim.go

@@ -14,6 +14,7 @@ import (
 	//"fmt"
 	"hash"
 	//"io/ioutil"
+	//"net"
 	"regexp"
 	"strings"
 )
@@ -25,6 +26,15 @@ const (
 	MaxHeaderLineLength = 70
 )
 
+type VerifyOutput int
+
+const (
+	SUCCESS VerifyOutput = 1 + iota
+	PERMFAIL
+	TEMPFAIL
+	NOTSIGNED
+)
+
 // sigOptions represents signing options
 type sigOptions struct {
 
@@ -143,30 +153,23 @@ func Sign(email *[]byte, options sigOptions) error {
 	}
 
 	// hash body
-	var bodyHash string
-	var h1, h2 hash.Hash
+	var h2 hash.Hash
 	var h3 crypto.Hash
 	signHash := strings.Split(options.Algo, "-")
 	if signHash[1] == "sha1" {
-		h1 = sha1.New()
+		//h1 = sha1.New()
 		h2 = sha1.New()
 		h3 = crypto.SHA1
 	} else {
-		h1 = sha256.New()
+		//h1 = sha256.New()
 		h2 = sha256.New()
 		h3 = crypto.SHA256
 	}
 
-	// if l tag (body length)
-	if options.BodyLength != 0 {
-		if uint(len(body)) < options.BodyLength {
-			return ErrBadDKimTagLBodyTooShort
+	bodyHash, err := getBodyHash(&body, signHash[1], options.BodyLength)
+	if err != nil {
+		return err
 	}
-		body = body[0:options.BodyLength]
-	}
-
-	h1.Write(body)
-	bodyHash = base64.StdEncoding.EncodeToString(h1.Sum(nil))
 
 	// Get dkim header base
 	dkimHeader := NewDkimHeaderBySigOptions(options)
@@ -209,27 +212,41 @@ func Sign(email *[]byte, options sigOptions) error {
 // state: SUCCESS or PERMFAIL or TEMPFAIL or NOTSIGNED
 // msg: a complementary message (if needed)
 // error: if an error occurs during verification
-func Verify(email *[]byte) (state, msg string, err error) {
+func Verify(email *[]byte) (VerifyOutput, error) {
 	// parse email
 	dkimHeader, err := NewFromEmail(email)
 	if err != nil {
 		if err == ErrDkimHeaderNotFound {
-			return "NOTSIGNED", ErrDkimHeaderNotFound.Error(), nil
+			return NOTSIGNED, ErrDkimHeaderNotFound
 		} else {
-			return "PERMFAIL", err.Error(), err
+			return PERMFAIL, err
 		}
 	}
-	println(dkimHeader)
 
-	// 	// Normalize
-	headers, body, err := canonicalize(email, dkimHeader.MessageCanonicalization, dkimHeader.Headers)
+	// Normalize
+	_, body, err := canonicalize(email, dkimHeader.MessageCanonicalization, dkimHeader.Headers)
 	if err != nil {
-		return "PERMFAIL", err.Error(), err
+		return PERMFAIL, err
+	}
+	sigHash := strings.Split(dkimHeader.Algorithm, "-")
+
+	// expired ? TODO
+
+	// get body hash
+	bodyHash, err := getBodyHash(&body, sigHash[0], dkimHeader.BodyLength)
+	if err != nil {
+		return PERMFAIL, err
+	}
+	println(bodyHash)
+	if bodyHash != dkimHeader.BodyHash {
+		return PERMFAIL, ErrVerifyBodyHash
 	}
 
-	// HERE
+	// we do not set quesry method because if it's other validation failed earlier
+	pubKey, err := newPubKeyFromDnsTxt(dkimHeader.Selector, dkimHeader.Domain)
+	println(pubKey)
 
-	return "SUCCESS", "", nil
+	return SUCCESS, nil
 }
 
 // canonicalize returns canonicalized version of header and body
@@ -386,6 +403,27 @@ func canonicalizeHeader(header string, algo string) (string, error) {
 	return header, ErrSignBadCanonicalization
 }
 
+// getBodyHash return the hash (bas64encoded) of the body
+func getBodyHash(body *[]byte, algo string, bodyLength uint) (string, error) {
+	var h hash.Hash
+	if algo == "sha1" {
+		h = sha1.New()
+	} else {
+		h = sha256.New()
+	}
+	toH := *body
+	// if l tag (body length)
+	if bodyLength != 0 {
+		if uint(len(toH)) < bodyLength {
+			return "", ErrBadDKimTagLBodyTooShort
+		}
+		toH = toH[0:bodyLength]
+	}
+
+	h.Write(toH)
+	return base64.StdEncoding.EncodeToString(h.Sum(nil)), nil
+}
+
 // removeFWS removes all FWS from string
 func removeFWS(in string) string {
 	rxReduceWS := regexp.MustCompile(`[ \t]+`)

dkimHeader.go

@@ -2,7 +2,7 @@ package dkim
 
 import (
 	"bytes"
-	"errors"
+	//"errors"
 	"fmt"
 	"net/mail"
 	"net/textproto"
@@ -271,6 +271,7 @@ func NewFromEmail(email *[]byte) (*DkimHeader, error) {
 	return keep, nil
 }
 
+// parseDkHeader parse raw dkim header
 func parseDkHeader(header string) (dkh *DkimHeader, err error) {
 	dkh = new(DkimHeader)
 
@@ -301,7 +302,7 @@ func parseDkHeader(header string) (dkh *DkimHeader, err error) {
 		switch flag {
 		case "v":
 			if data != "1" {
-				return nil, ErrDkimVersionUnsuported
+				return nil, ErrDkimVersionNotsupported
 			}
 			dkh.Version = data
 			mandatoryFlags["v"] = true
@@ -313,27 +314,51 @@ func parseDkHeader(header string) (dkh *DkimHeader, err error) {
 			mandatoryFlags["a"] = true
 		case "b":
 			dkh.SignatureData = removeFWS(data)
+			if len(dkh.SignatureData) != 0 {
 				mandatoryFlags["b"] = true
+			}
 		case "bh":
 			dkh.BodyHash = removeFWS(data)
+			if len(dkh.BodyHash) != 0 {
 				mandatoryFlags["bh"] = true
+			}
 		case "d":
 			dkh.Domain = strings.ToLower(data)
+			if len(dkh.Domain) != 0 {
 				mandatoryFlags["d"] = true
+			}
 		case "h":
 			data = strings.ToLower(data)
 			dkh.Headers = strings.Split(data, ":")
+			if len(dkh.Headers) != 0 {
 				mandatoryFlags["h"] = true
+			}
+			fromFound := false
+			for _, h := range dkh.Headers {
+				if h == "from" {
+					fromFound = true
+				}
+			}
+			if !fromFound {
+				return nil, ErrDkimHeaderNoFromInHTag
+			}
 		case "s":
 			dkh.Selector = strings.ToLower(data)
+			if len(dkh.Selector) != 0 {
 				mandatoryFlags["s"] = true
+			}
 		case "c":
 			dkh.MessageCanonicalization, err = validateCanonicalization(strings.ToLower(data))
 			if err != nil {
-				return
+				return nil, err
 			}
 		case "i":
+			if data != "" {
+				if !strings.HasSuffix(data, dkh.Domain) {
+					return nil, ErrDkimHeaderDomainMismatch
+				}
 				dkh.Auid = data
+			}
 		case "l":
 			ui, err := strconv.ParseUint(data, 10, 32)
 			if err != nil {
@@ -342,6 +367,9 @@ func parseDkHeader(header string) (dkh *DkimHeader, err error) {
 			dkh.BodyLength = uint(ui)
 		case "q":
 			dkh.QueryMethods = strings.Split(data, ":")
+			if len(dkh.QueryMethods) == 0 || strings.ToLower(dkh.QueryMethods[0]) != "dns/txt" {
+				return nil, errQueryMethodNotsupported
+			}
 		case "t":
 			ts, err := strconv.ParseInt(data, 10, 64)
 			if err != nil {
@@ -361,12 +389,22 @@ func parseDkHeader(header string) (dkh *DkimHeader, err error) {
 	}
 
 	// All mandatory flags are in ?
-	for f, p := range mandatoryFlags {
+	for _, p := range mandatoryFlags {
 		if !p {
-			return nil, errors.New("missing '" + f + "' flag in DKIM header")
+			return nil, ErrDkimHeaderMissingRequiredTag
 		}
 	}
 
+	// default for i/Auid
+	if dkh.Auid == "" {
+		dkh.Auid = "@" + dkh.Domain
+	}
+
+	// defaut for query method
+	if len(dkh.QueryMethods) == 0 {
+		dkh.QueryMethods = []string{"dns/text"}
+	}
+
 	return dkh, nil
 
 }

dkim_test.go

@@ -112,7 +112,7 @@ var signedSimpleSimple = "DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=simple
 	" DIpJW4XNA/uqLSswtjCYbJsSg9Ywv1o=" + CRLF + emailBase
 
 var signedNoFrom = "DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=simple/simple;" + CRLF +
-	" s=test; d=tmail.io; l=5; h=from:date:mime-version:received:received;" + CRLF +
+	" s=test; d=tmail.io; h=from:date:mime-version:received:received;" + CRLF +
 	" bh=GF+NsyJx/iX1Yab8k4suJkMG7DBO2lGAB9F2SCY4GWk=;" + CRLF +
 	" b=SoEhlu1Emm2ASqo8jMhz6FIf2nNHt3ouY4Av/pFFEkQ048RqUFP437ap7RbtL2wh0N3Kkm" + CRLF +
 	" AKF2TcTLZ++1nalq+djU+/aP4KYQd4RWWFBjkxDzvCH4bvB1M5AGp4Qz9ldmdMQBWOvvSp" + CRLF +
@@ -258,28 +258,38 @@ func Test_Sign(t *testing.T) {
 func Test_Verify(t *testing.T) {
 	// no DKIM header
 	email := []byte(emailBase)
-	status, msg, err := Verify(&email)
-	assert.NoError(t, err)
-	assert.Equal(t, "NOTSIGNED", status)
-	assert.Equal(t, ErrDkimHeaderNotFound.Error(), msg)
+	status, err := Verify(&email)
+	assert.Equal(t, NOTSIGNED, status)
+	assert.Equal(t, ErrDkimHeaderNotFound, err)
 
 	// No From
 	email = []byte(signedNoFrom)
-	status, msg, err = Verify(&email)
-	assert.NoError(t, err)
-	assert.Equal(t, "SUCCESS", status)
+	status, err = Verify(&email)
+	assert.Equal(t, ErrVerifyBodyHash, err)
+	assert.Equal(t, PERMFAIL, status) // cause we use dkheader of the "with from" email
 
 	// missing mandatory 'a' flag
 	email = []byte(signedMissingFlag)
-	status, msg, err = Verify(&email)
+	status, err = Verify(&email)
 	assert.Error(t, err)
-	assert.Equal(t, "PERMFAIL", status)
-	assert.Equal(t, "missing 'a' flag in DKIM header", msg)
+	assert.Equal(t, PERMFAIL, status)
+	assert.Equal(t, ErrDkimHeaderMissingRequiredTag, err)
 
 	// missing bad algo
 	email = []byte(signedBadAlgo)
-	status, msg, err = Verify(&email)
-	assert.Error(t, err)
-	assert.Equal(t, "PERMFAIL", status)
-	assert.Equal(t, ErrSignBadAlgo.Error(), msg)
+	status, err = Verify(&email)
+	assert.Equal(t, PERMFAIL, status)
+	assert.Equal(t, ErrSignBadAlgo, err)
+
+	// relaxed
+	email = []byte(signedRelaxedRelaxed)
+	status, err = Verify(&email)
+	assert.NoError(t, err)
+	assert.Equal(t, SUCCESS, status)
+
+	// simple
+	email = []byte(signedSimpleSimple)
+	status, err = Verify(&email)
+	assert.NoError(t, err)
+	assert.Equal(t, SUCCESS, status)
 }

errors.go

@@ -15,7 +15,7 @@ var (
 	ErrSignSelectorRequired = errors.New("Selector is required")
 
 	// If Headers is specified it should at least contain 'from'
-	ErrSignHeaderShouldContainsFrom = errors.New("Header must contains 'from' field")
+	ErrSignHeaderShouldContainsFrom = errors.New("header must contains 'from' field")
 
 	// If bad Canonicalization parameter
 	ErrSignBadCanonicalization = errors.New("bad Canonicalization parameter")
@@ -41,8 +41,21 @@ var (
 	// ErrDkimHeaderBTagNotFound when there's no b tag
 	ErrDkimHeaderBTagNotFound = errors.New("no tag 'b' found in dkim header")
 
-	ErrDkimHeaderMissingTagV = errors.New("no tag 'v' found in dkim header")
+	// ErrDkimHeaderNoFromInHTag
+	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")
 
 	// Version not supported
-	ErrDkimVersionUnsuported = errors.New("unsuported DKIM version")
+	ErrDkimVersionNotsupported = errors.New("incompatible version")
+
+	// Query method unsopported
+	errQueryMethodNotsupported = errors.New("query method not supported")
+
+	// ErrVerifyBodyHash when body hash doesn't verify
+	ErrVerifyBodyHash = errors.New("body hash did not verify")
 )

pubKeyRep.go

@@ -0,0 +1,26 @@
+package dkim
+
+import (
+	"crypto/rsa"
+	"fmt"
+	"net"
+)
+
+// pubKeyRep represents a parsed version of public key record
+type pubKeyRep struct {
+	Version      string
+	HashAlgo     []string
+	KeyType      string
+	Note         string
+	PubKey       rsa.PublicKey
+	ServiceType  []string
+	FlagTesting  bool // flag y
+	FlagIMustBeD bool // flag i
+}
+
+func newPubKeyFromDnsTxt(selector, domain string) (*pubKeyRep, error) {
+	txt, err := net.LookupTXT(selector + "._domainkey." + domain)
+	fmt.Println(txt, err)
+
+	return nil, nil
+}