1 files changed, 383 insertions, 0 deletions
diff --git a/vendor/github.com/rsc/letsencrypt/vendor/github.com/miekg/dns/tsig.go b/vendor/github.com/rsc/letsencrypt/vendor/github.com/miekg/dns/tsig.go
new file mode 100644
index 000000000..24013096b
--- /dev/null
+++ b/vendor/github.com/rsc/letsencrypt/vendor/github.com/miekg/dns/tsig.go
@@ -0,0 +1,383 @@
+package dns
+
+import (
+	"crypto/hmac"
+	"crypto/md5"
+	"crypto/sha1"
+	"crypto/sha256"
+	"crypto/sha512"
+	"encoding/binary"
+	"encoding/hex"
+	"hash"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// HMAC hashing codes. These are transmitted as domain names.
+const (
+	HmacMD5    = "hmac-md5.sig-alg.reg.int."
+	HmacSHA1   = "hmac-sha1."
+	HmacSHA256 = "hmac-sha256."
+	HmacSHA512 = "hmac-sha512."
+)
+
+// TSIG is the RR the holds the transaction signature of a message.
+// See RFC 2845 and RFC 4635.
+type TSIG struct {
+	Hdr        RR_Header
+	Algorithm  string `dns:"domain-name"`
+	TimeSigned uint64 `dns:"uint48"`
+	Fudge      uint16
+	MACSize    uint16
+	MAC        string `dns:"size-hex:MACSize"`
+	OrigId     uint16
+	Error      uint16
+	OtherLen   uint16
+	OtherData  string `dns:"size-hex:OtherLen"`
+}
+
+// TSIG has no official presentation format, but this will suffice.
+
+func (rr *TSIG) String() string {
+	s := "\n;; TSIG PSEUDOSECTION:\n"
+	s += rr.Hdr.String() +
+		" " + rr.Algorithm +
+		" " + tsigTimeToString(rr.TimeSigned) +
+		" " + strconv.Itoa(int(rr.Fudge)) +
+		" " + strconv.Itoa(int(rr.MACSize)) +
+		" " + strings.ToUpper(rr.MAC) +
+		" " + strconv.Itoa(int(rr.OrigId)) +
+		" " + strconv.Itoa(int(rr.Error)) + // BIND prints NOERROR
+		" " + strconv.Itoa(int(rr.OtherLen)) +
+		" " + rr.OtherData
+	return s
+}
+
+// The following values must be put in wireformat, so that the MAC can be calculated.
+// RFC 2845, section 3.4.2. TSIG Variables.
+type tsigWireFmt struct {
+	// From RR_Header
+	Name  string `dns:"domain-name"`
+	Class uint16
+	Ttl   uint32
+	// Rdata of the TSIG
+	Algorithm  string `dns:"domain-name"`
+	TimeSigned uint64 `dns:"uint48"`
+	Fudge      uint16
+	// MACSize, MAC and OrigId excluded
+	Error     uint16
+	OtherLen  uint16
+	OtherData string `dns:"size-hex:OtherLen"`
+}
+
+// If we have the MAC use this type to convert it to wiredata. Section 3.4.3. Request MAC
+type macWireFmt struct {
+	MACSize uint16
+	MAC     string `dns:"size-hex:MACSize"`
+}
+
+// 3.3. Time values used in TSIG calculations
+type timerWireFmt struct {
+	TimeSigned uint64 `dns:"uint48"`
+	Fudge      uint16
+}
+
+// TsigGenerate fills out the TSIG record attached to the message.
+// The message should contain
+// a "stub" TSIG RR with the algorithm, key name (owner name of the RR),
+// time fudge (defaults to 300 seconds) and the current time
+// The TSIG MAC is saved in that Tsig RR.
+// When TsigGenerate is called for the first time requestMAC is set to the empty string and
+// timersOnly is false.
+// If something goes wrong an error is returned, otherwise it is nil.
+func TsigGenerate(m *Msg, secret, requestMAC string, timersOnly bool) ([]byte, string, error) {
+	if m.IsTsig() == nil {
+		panic("dns: TSIG not last RR in additional")
+	}
+	// If we barf here, the caller is to blame
+	rawsecret, err := fromBase64([]byte(secret))
+	if err != nil {
+		return nil, "", err
+	}
+
+	rr := m.Extra[len(m.Extra)-1].(*TSIG)
+	m.Extra = m.Extra[0 : len(m.Extra)-1] // kill the TSIG from the msg
+	mbuf, err := m.Pack()
+	if err != nil {
+		return nil, "", err
+	}
+	buf := tsigBuffer(mbuf, rr, requestMAC, timersOnly)
+
+	t := new(TSIG)
+	var h hash.Hash
+	switch strings.ToLower(rr.Algorithm) {
+	case HmacMD5:
+		h = hmac.New(md5.New, []byte(rawsecret))
+	case HmacSHA1:
+		h = hmac.New(sha1.New, []byte(rawsecret))
+	case HmacSHA256:
+		h = hmac.New(sha256.New, []byte(rawsecret))
+	case HmacSHA512:
+		h = hmac.New(sha512.New, []byte(rawsecret))
+	default:
+		return nil, "", ErrKeyAlg
+	}
+	h.Write(buf)
+	t.MAC = hex.EncodeToString(h.Sum(nil))
+	t.MACSize = uint16(len(t.MAC) / 2) // Size is half!
+
+	t.Hdr = RR_Header{Name: rr.Hdr.Name, Rrtype: TypeTSIG, Class: ClassANY, Ttl: 0}
+	t.Fudge = rr.Fudge
+	t.TimeSigned = rr.TimeSigned
+	t.Algorithm = rr.Algorithm
+	t.OrigId = m.Id
+
+	tbuf := make([]byte, t.len())
+	if off, err := PackRR(t, tbuf, 0, nil, false); err == nil {
+		tbuf = tbuf[:off] // reset to actual size used
+	} else {
+		return nil, "", err
+	}
+	mbuf = append(mbuf, tbuf...)
+	// Update the ArCount directly in the buffer.
+	binary.BigEndian.PutUint16(mbuf[10:], uint16(len(m.Extra)+1))
+
+	return mbuf, t.MAC, nil
+}
+
+// TsigVerify verifies the TSIG on a message.
+// If the signature does not validate err contains the
+// error, otherwise it is nil.
+func TsigVerify(msg []byte, secret, requestMAC string, timersOnly bool) error {
+	rawsecret, err := fromBase64([]byte(secret))
+	if err != nil {
+		return err
+	}
+	// Strip the TSIG from the incoming msg
+	stripped, tsig, err := stripTsig(msg)
+	if err != nil {
+		return err
+	}
+
+	msgMAC, err := hex.DecodeString(tsig.MAC)
+	if err != nil {
+		return err
+	}
+
+	buf := tsigBuffer(stripped, tsig, requestMAC, timersOnly)
+
+	// Fudge factor works both ways. A message can arrive before it was signed because
+	// of clock skew.
+	now := uint64(time.Now().Unix())
+	ti := now - tsig.TimeSigned
+	if now < tsig.TimeSigned {
+		ti = tsig.TimeSigned - now
+	}
+	if uint64(tsig.Fudge) < ti {
+		return ErrTime
+	}
+
+	var h hash.Hash
+	switch strings.ToLower(tsig.Algorithm) {
+	case HmacMD5:
+		h = hmac.New(md5.New, rawsecret)
+	case HmacSHA1:
+		h = hmac.New(sha1.New, rawsecret)
+	case HmacSHA256:
+		h = hmac.New(sha256.New, rawsecret)
+	case HmacSHA512:
+		h = hmac.New(sha512.New, rawsecret)
+	default:
+		return ErrKeyAlg
+	}
+	h.Write(buf)
+	if !hmac.Equal(h.Sum(nil), msgMAC) {
+		return ErrSig
+	}
+	return nil
+}
+
+// Create a wiredata buffer for the MAC calculation.
+func tsigBuffer(msgbuf []byte, rr *TSIG, requestMAC string, timersOnly bool) []byte {
+	var buf []byte
+	if rr.TimeSigned == 0 {
+		rr.TimeSigned = uint64(time.Now().Unix())
+	}
+	if rr.Fudge == 0 {
+		rr.Fudge = 300 // Standard (RFC) default.
+	}
+
+	if requestMAC != "" {
+		m := new(macWireFmt)
+		m.MACSize = uint16(len(requestMAC) / 2)
+		m.MAC = requestMAC
+		buf = make([]byte, len(requestMAC)) // long enough
+		n, _ := packMacWire(m, buf)
+		buf = buf[:n]
+	}
+
+	tsigvar := make([]byte, DefaultMsgSize)
+	if timersOnly {
+		tsig := new(timerWireFmt)
+		tsig.TimeSigned = rr.TimeSigned
+		tsig.Fudge = rr.Fudge
+		n, _ := packTimerWire(tsig, tsigvar)
+		tsigvar = tsigvar[:n]
+	} else {
+		tsig := new(tsigWireFmt)
+		tsig.Name = strings.ToLower(rr.Hdr.Name)
+		tsig.Class = ClassANY
+		tsig.Ttl = rr.Hdr.Ttl
+		tsig.Algorithm = strings.ToLower(rr.Algorithm)
+		tsig.TimeSigned = rr.TimeSigned
+		tsig.Fudge = rr.Fudge
+		tsig.Error = rr.Error
+		tsig.OtherLen = rr.OtherLen
+		tsig.OtherData = rr.OtherData
+		n, _ := packTsigWire(tsig, tsigvar)
+		tsigvar = tsigvar[:n]
+	}
+
+	if requestMAC != "" {
+		x := append(buf, msgbuf...)
+		buf = append(x, tsigvar...)
+	} else {
+		buf = append(msgbuf, tsigvar...)
+	}
+	return buf
+}
+
+// Strip the TSIG from the raw message.
+func stripTsig(msg []byte) ([]byte, *TSIG, error) {
+	// Copied from msg.go's Unpack() Header, but modified.
+	var (
+		dh  Header
+		err error
+	)
+	off, tsigoff := 0, 0
+
+	if dh, off, err = unpackMsgHdr(msg, off); err != nil {
+		return nil, nil, err
+	}
+	if dh.Arcount == 0 {
+		return nil, nil, ErrNoSig
+	}
+
+	// Rcode, see msg.go Unpack()
+	if int(dh.Bits&0xF) == RcodeNotAuth {
+		return nil, nil, ErrAuth
+	}
+
+	for i := 0; i < int(dh.Qdcount); i++ {
+		_, off, err = unpackQuestion(msg, off)
+		if err != nil {
+			return nil, nil, err
+		}
+	}
+
+	_, off, err = unpackRRslice(int(dh.Ancount), msg, off)
+	if err != nil {
+		return nil, nil, err
+	}
+	_, off, err = unpackRRslice(int(dh.Nscount), msg, off)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	rr := new(TSIG)
+	var extra RR
+	for i := 0; i < int(dh.Arcount); i++ {
+		tsigoff = off
+		extra, off, err = UnpackRR(msg, off)
+		if err != nil {
+			return nil, nil, err
+		}
+		if extra.Header().Rrtype == TypeTSIG {
+			rr = extra.(*TSIG)
+			// Adjust Arcount.
+			arcount := binary.BigEndian.Uint16(msg[10:])
+			binary.BigEndian.PutUint16(msg[10:], arcount-1)
+			break
+		}
+	}
+	if rr == nil {
+		return nil, nil, ErrNoSig
+	}
+	return msg[:tsigoff], rr, nil
+}
+
+// Translate the TSIG time signed into a date. There is no
+// need for RFC1982 calculations as this date is 48 bits.
+func tsigTimeToString(t uint64) string {
+	ti := time.Unix(int64(t), 0).UTC()
+	return ti.Format("20060102150405")
+}
+
+func packTsigWire(tw *tsigWireFmt, msg []byte) (int, error) {
+	// copied from zmsg.go TSIG packing
+	// RR_Header
+	off, err := PackDomainName(tw.Name, msg, 0, nil, false)
+	if err != nil {
+		return off, err
+	}
+	off, err = packUint16(tw.Class, msg, off)
+	if err != nil {
+		return off, err
+	}
+	off, err = packUint32(tw.Ttl, msg, off)
+	if err != nil {
+		return off, err
+	}
+
+	off, err = PackDomainName(tw.Algorithm, msg, off, nil, false)
+	if err != nil {
+		return off, err
+	}
+	off, err = packUint48(tw.TimeSigned, msg, off)
+	if err != nil {
+		return off, err
+	}
+	off, err = packUint16(tw.Fudge, msg, off)
+	if err != nil {
+		return off, err
+	}
+
+	off, err = packUint16(tw.Error, msg, off)
+	if err != nil {
+		return off, err
+	}
+	off, err = packUint16(tw.OtherLen, msg, off)
+	if err != nil {
+		return off, err
+	}
+	off, err = packStringHex(tw.OtherData, msg, off)
+	if err != nil {
+		return off, err
+	}
+	return off, nil
+}
+
+func packMacWire(mw *macWireFmt, msg []byte) (int, error) {
+	off, err := packUint16(mw.MACSize, msg, 0)
+	if err != nil {
+		return off, err
+	}
+	off, err = packStringHex(mw.MAC, msg, off)
+	if err != nil {
+		return off, err
+	}
+	return off, nil
+}
+
+func packTimerWire(tw *timerWireFmt, msg []byte) (int, error) {
+	off, err := packUint48(tw.TimeSigned, msg, 0)
+	if err != nil {
+		return off, err
+	}
+	off, err = packUint16(tw.Fudge, msg, off)
+	if err != nil {
+		return off, err
+	}
+	return off, nil
+}