From e16155e22a8f00bdbb4acb0a108c605065f9ba3f Mon Sep 17 00:00:00 2001
From: Frank Denis <github@pureftpd.org>
Date: Fri, 26 Jan 2018 20:38:31 +0100
Subject: [PATCH] DoHstamps

---
 dnscrypt-proxy/sources.go |   2 +-
 dnscrypt-proxy/stamps.go  | 106 ++++++++++++++++++++++++++++++++++----
 2 files changed, 98 insertions(+), 10 deletions(-)

diff --git a/dnscrypt-proxy/sources.go b/dnscrypt-proxy/sources.go
index 139fb50f..6bb3392d 100644
--- a/dnscrypt-proxy/sources.go
+++ b/dnscrypt-proxy/sources.go
@@ -198,7 +198,7 @@ func (source *Source) parseV1(prefix string) ([]RegisteredServer, error) {
 		if strings.EqualFold(record[8], "yes") {
 			props |= ServerInformalPropertyNoLog
 		}
-		stamp, err := NewServerStampFromDNSCryptLegacy(serverAddrStr, serverPkStr, providerName, props)
+		stamp, err := NewDNSCryptServerStampFromLegacy(serverAddrStr, serverPkStr, providerName, props)
 		if err != nil {
 			return registeredServers, err
 		}
diff --git a/dnscrypt-proxy/stamps.go b/dnscrypt-proxy/stamps.go
index 5e1fa866..901777c3 100644
--- a/dnscrypt-proxy/stamps.go
+++ b/dnscrypt-proxy/stamps.go
@@ -9,6 +9,7 @@ import (
 	"net"
 	"strings"
 
+	"github.com/jedisct1/dlog"
 	"golang.org/x/crypto/ed25519"
 )
 
@@ -23,13 +24,14 @@ const (
 type ServerStamp struct {
 	serverAddrStr string
 	serverPk      []uint8
+	hash          []uint8
 	providerName  string
 	path          string
 	props         ServerInformalProperties
 	proto         StampProtoType
 }
 
-func NewServerStampFromDNSCryptLegacy(serverAddrStr string, serverPkStr string, providerName string, props ServerInformalProperties) (ServerStamp, error) {
+func NewDNSCryptServerStampFromLegacy(serverAddrStr string, serverPkStr string, providerName string, props ServerInformalProperties) (ServerStamp, error) {
 	if net.ParseIP(serverAddrStr) != nil {
 		serverAddrStr = fmt.Sprintf("%s:%d", serverAddrStr, DefaultPort)
 	}
@@ -46,22 +48,29 @@ func NewServerStampFromDNSCryptLegacy(serverAddrStr string, serverPkStr string,
 	}, nil
 }
 
-// id(u8) props addrLen(1) serverAddr pkStrlen(1) pkStr providerNameLen(1) providerName
-
 func NewServerStampFromString(stampStr string) (ServerStamp, error) {
-	stamp := ServerStamp{}
 	if !strings.HasPrefix(stampStr, "sdns://") && !strings.HasPrefix(stampStr, "dnsc://") {
-		return stamp, errors.New("Stamps are expected to start with sdns://")
+		return ServerStamp{}, errors.New("Stamps are expected to start with sdns://")
 	}
 	bin, err := base64.RawURLEncoding.DecodeString(stampStr[7:])
 	if err != nil {
-		return stamp, err
+		return ServerStamp{}, err
 	}
-	if len(bin) < 24 {
-		return stamp, errors.New("Stamp is too short")
+	if len(bin) < 1 {
+		return ServerStamp{}, errors.New("Stamp is too short")
 	}
 	if bin[0] != uint8(StampProtoTypeDNSCrypt) {
-		return stamp, errors.New("Unsupported stamp version")
+		return newDNSCryptServerStamp(bin)
+	}
+	return ServerStamp{}, errors.New("Unsupported stamp version or protocol")
+}
+
+// id(u8)=0x02 props addrLen(1) serverAddr pkStrlen(1) pkStr providerNameLen(1) providerName
+
+func newDNSCryptServerStamp(bin []byte) (ServerStamp, error) {
+	stamp := ServerStamp{}
+	if len(bin) < 24 {
+		return stamp, errors.New("Stamp is too short")
 	}
 	stamp.props = ServerInformalProperties(binary.LittleEndian.Uint64(bin[1:9]))
 	binLen := len(bin)
@@ -97,7 +106,64 @@ func NewServerStampFromString(stampStr string) (ServerStamp, error) {
 	return stamp, nil
 }
 
+// id(u8)=0x02 props addrLen(1) serverAddr hashLen(1) hash providerNameLen(1) providerName pathLen(1) path
+
+func newDoHServerStamp(bin []byte) (ServerStamp, error) {
+	stamp := ServerStamp{}
+
+	stamp.props = ServerInformalProperties(binary.LittleEndian.Uint64(bin[1:9]))
+	binLen := len(bin)
+	pos := 9
+
+	len := int(bin[pos])
+	if len >= binLen-pos {
+		return stamp, errors.New("Invalid stamp")
+	}
+	pos++
+	stamp.serverAddrStr = string(bin[pos : pos+len])
+	pos += len
+
+	len = int(bin[pos])
+	if len >= binLen-pos {
+		return stamp, errors.New("Invalid stamp")
+	}
+	pos++
+	stamp.hash = bin[pos : pos+len]
+	pos += len
+
+	len = int(bin[pos])
+	if len >= binLen-pos {
+		return stamp, errors.New("Invalid stamp")
+	}
+	pos++
+	stamp.providerName = string(bin[pos : pos+len])
+	pos += len
+
+	len = int(bin[pos])
+	if len >= binLen-pos {
+		return stamp, errors.New("Invalid stamp")
+	}
+	pos++
+	stamp.path = string(bin[pos : pos+len])
+	pos += len
+
+	if pos != binLen {
+		return stamp, errors.New("Invalid stamp (garbage after end)")
+	}
+	return stamp, nil
+}
+
 func (stamp *ServerStamp) String() string {
+	if stamp.proto == StampProtoTypeDNSCrypt {
+		return stamp.dnsCryptString()
+	} else if stamp.proto == StampProtoTypeDoH {
+		return stamp.dohString()
+	}
+	dlog.Fatal("Unsupported protocol")
+	return ""
+}
+
+func (stamp *ServerStamp) dnsCryptString() string {
 	bin := make([]uint8, 9)
 	bin[0] = uint8(StampProtoTypeDNSCrypt)
 	binary.LittleEndian.PutUint64(bin[1:9], uint64(stamp.props))
@@ -115,3 +181,25 @@ func (stamp *ServerStamp) String() string {
 
 	return "sdns://" + str
 }
+
+func (stamp *ServerStamp) dohString() string {
+	bin := make([]uint8, 9)
+	bin[0] = uint8(StampProtoTypeDoH)
+	binary.LittleEndian.PutUint64(bin[1:9], uint64(stamp.props))
+
+	bin = append(bin, uint8(len(stamp.serverAddrStr)))
+	bin = append(bin, []uint8(stamp.serverAddrStr)...)
+
+	bin = append(bin, uint8(len(stamp.hash)))
+	bin = append(bin, []uint8(stamp.hash)...)
+
+	bin = append(bin, uint8(len(stamp.providerName)))
+	bin = append(bin, []uint8(stamp.providerName)...)
+
+	bin = append(bin, uint8(len(stamp.path)))
+	bin = append(bin, []uint8(stamp.path)...)
+
+	str := base64.RawURLEncoding.EncodeToString(bin)
+
+	return "sdns://" + str
+}