forked from toorop/go-dkim
/
pubKeyRep.go
127 lines (118 loc) · 2.9 KB
/
pubKeyRep.go
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package dkim
import (
"crypto/rsa"
"crypto/x509"
"encoding/base64"
"net"
"strings"
)
// 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, verifyOutput, error) {
txt, err := net.LookupTXT(selector + "._domainkey." + domain)
if err != nil {
if strings.HasSuffix(err.Error(), "no such host") {
return nil, PERMFAIL, ErrVerifyNoKeyForSignature
} else {
return nil, TEMPFAIL, ErrVerifyKeyUnavailable
}
}
// empty record
if len(txt) == 0 {
return nil, PERMFAIL, ErrVerifyNoKeyForSignature
}
pkr := new(pubKeyRep)
pkr.Version = "DKIM1"
pkr.HashAlgo = []string{"sha1", "sha256"}
pkr.KeyType = "rsa"
pkr.ServiceType = []string{"all"}
pkr.FlagTesting = false
pkr.FlagIMustBeD = false
// parsing, we keep the first record
// TODO: if there is multiple record
p := strings.Split(txt[0], ";")
for i, data := range p {
keyVal := strings.SplitN(data, "=", 2)
val := ""
if len(keyVal) > 1 {
val = strings.TrimSpace(keyVal[1])
}
switch strings.ToLower(strings.TrimSpace(keyVal[0])) {
case "v":
// RFC: is this tag is specified it MUST be the first in the record
if i != 0 {
return nil, PERMFAIL, ErrVerifyTagVMustBeTheFirst
}
pkr.Version = val
if pkr.Version != "DKIM1" {
return nil, PERMFAIL, ErrVerifyVersionMusBeDkim1
}
case "h":
p := strings.Split(strings.ToLower(val), ":")
pkr.HashAlgo = []string{}
for _, h := range p {
h = strings.TrimSpace(h)
if h == "sha1" || h == "sha256" {
pkr.HashAlgo = append(pkr.HashAlgo, h)
}
}
// if empty switch back to default
if len(pkr.HashAlgo) == 0 {
pkr.HashAlgo = []string{"sha1", "sha256"}
}
case "k":
if strings.ToLower(val) != "rsa" {
return nil, PERMFAIL, ErrVerifyBadKeyType
}
case "n":
pkr.Note = val
case "p":
rawkey := val
if rawkey == "" {
return nil, PERMFAIL, ErrVerifyRevokedKey
}
un64, err := base64.StdEncoding.DecodeString(rawkey)
if err != nil {
return nil, PERMFAIL, ErrVerifyBadKey
}
pk, err := x509.ParsePKIXPublicKey(un64)
pkr.PubKey = *pk.(*rsa.PublicKey)
case "s":
t := strings.Split(strings.ToLower(val), ":")
for _, tt := range t {
if tt == "*" {
pkr.ServiceType = []string{"all"}
break
}
if tt == "email" {
pkr.ServiceType = []string{"email"}
}
}
case "t":
flags := strings.Split(strings.ToLower(val), ":")
for _, flag := range flags {
if flag == "y" {
pkr.FlagTesting = true
continue
}
if flag == "s" {
pkr.FlagIMustBeD = true
}
}
}
}
// if no pubkey
if pkr.PubKey == (rsa.PublicKey{}) {
return nil, PERMFAIL, ErrVerifyNoKey
}
return pkr, SUCCESS, nil
}