// step3-4
func (s socks5Handler) readRequest() (string, bool) {
var (
buf = make([]byte, 262) // 4+(1+255)+2
host string
ofs int
ver, cmd, atyp byte
)
var msg = []byte{5, 0, 0, 1, 0, 0, 0, 0, 0, 0}
setRTimeout(s.conn)
_, err := s.conn.Read(buf)
if err != nil {
exception.Spawn(&err, "socks: read request")
goto errLogging
}
ver, cmd, atyp = buf[0], buf[1], buf[3]
if ver != S5_VER || cmd != 1 {
exception.Spawn(&err, "socks: invalid request")
goto errHandler
}
buf = buf[4:]
switch atyp {
case IPV4:
host = net.IP(buf[:net.IPv4len]).String()
ofs = net.IPv4len
case IPV6:
host = "[" + net.IP(buf[:net.IPv6len]).String() + "]"
ofs = net.IPv6len
case DOMAIN:
dlen := int(buf[0])
ofs = dlen + 1
host = string(buf[1:ofs])
// literal IPv6
if strings.Count(host, ":") >= 2 && !strings.HasPrefix(host, "[") {
host = "[" + host + "]"
}
default:
exception.Spawn(&err, "socks: invalid request")
goto errHandler
}
// accept
_, err = s.conn.Write(msg)
if err != nil {
exception.Spawn(&err, "socks: write response")
goto errLogging
}
host += ":" + strconv.Itoa(int(binary.BigEndian.Uint16(buf[ofs:])))
return host, true
errHandler:
msg[1] = 0x1 // general SOCKS server failure
setWTimeout(s.conn)
s.conn.Write(msg)
errLogging:
log.Warningln(err)
return NULL, false
}
func (n *d5sman) authenticate(conn *Conn, session *Session) error {
var err error
setRTimeout(conn)
hashSRand, err := ReadFullByLen(1, conn)
if err != nil {
// client aborted
if IsClosedError(err) {
return ABORTED_ERROR.Apply(err)
} else {
return exception.Spawn(&err, "srand: read connection")
}
}
myHashSRand := hash256(n.sRand)
if !bytes.Equal(hashSRand, myHashSRand) {
// MITM ?
return INCONSISTENT_HASH
}
// client identity
setRTimeout(conn)
idBuf, err := ReadFullByLen(1, conn)
if err != nil {
return exception.Spawn(&err, "auth: read connection")
}
user, passwd, err := n.deserializeIdentity(idBuf)
if err != nil {
return err
}
if log.V(log.LV_LOGIN) {
log.Infoln("Login request:", user)
}
pass, err := n.AuthSys.Authenticate(user, passwd)
if !pass {
// authSys denied
log.Warningf("Auth %s:%s failed: %v\n", user, passwd, err)
// reply failed msg
conn.Write([]byte{1, 0})
return VALIDATION_FAILED
}
session.indentifySession(user, conn)
w := newMsgWriter()
w.WriteL1Msg([]byte{AUTH_PASS})
w.WriteL2Msg(n.tunParams.serialize())
// send tokens
num := maxInt(GENERATE_TOKEN_NUM, n.Parallels+2)
tokens := n.sessionMgr.createTokens(session, num)
w.WriteL2Msg(tokens[1:]) // skip index=0
setWTimeout(conn)
err = w.WriteTo(conn)
return exception.Spawn(&err, "setting: write connection")
}
// finish DHE
// 1, dhPub, dhSign, rand
// 2, hashHello, version
func (n *d5sman) finishDHExchange(conn *Conn) (cf *CipherFactory, err error) {
var dhPub, key []byte
dhKey, _ := crypto.NewDHKey(DH_METHOD)
setRTimeout(conn)
dhPub, err = ReadFullByLen(2, conn)
if err != nil {
exception.Spawn(&err, "dh: read connection")
return
}
w := newMsgWriter()
myDhPub := dhKey.ExportPubKey()
w.WriteL1Msg(myDhPub)
myDhSign := DSASign(n.privateKey, myDhPub)
w.WriteL1Msg(myDhSign)
n.sRand = randMinArray()
w.WriteL1Msg(n.sRand)
setWTimeout(conn)
err = w.WriteTo(conn)
if err != nil {
exception.Spawn(&err, "dh: write connection")
return
}
key, err = dhKey.ComputeKey(dhPub)
if err != nil {
exception.Spawn(&err, "dh: compute")
return
}
// setup cipher
cf = NewCipherFactory(n.Cipher, key, n.dbcHello)
conn.SetupCipher(cf, n.sRand)
// encrypted
w.WriteL1Msg(hash256(n.dbcHello))
w.WriteL1Msg(ito4b(VERSION))
setWTimeout(conn)
err = w.WriteTo(conn)
if err != nil {
exception.Spawn(&err, "em: write connection")
return
}
return
}
// step1-2
func (s socks5Handler) handshake() bool {
var buf = make([]byte, 2)
var n, nmethods int
var ver byte
setRTimeout(s.conn)
_, err := io.ReadFull(s.conn, buf)
if err != nil {
exception.Spawn(&err, "socks: read header")
goto errLogging
}
ver, nmethods = buf[0], int(buf[1])
if ver != S5_VER || nmethods < 1 {
err = INVALID_SOCKS5_HEADER
exception.Spawn(&err, "socks: read header [% x]", buf[:2])
goto errHandler
}
buf = make([]byte, nmethods+1) // consider method non-00
setRTimeout(s.conn)
n, err = io.ReadAtLeast(s.conn, buf, nmethods)
if err != nil || n != nmethods {
err = INVALID_SOCKS5_HEADER
exception.Spawn(&err, "socks: read header [% x]", buf)
goto errHandler
}
// accept
buf = []byte{5, 0}
setWTimeout(s.conn)
_, err = s.conn.Write(buf)
if err == nil {
return true
} else {
err = exception.Spawn(&err, "socks: write response")
goto errLogging
}
errHandler:
// handshake error feedback
// NO ACCEPTABLE METHODS
buf = []byte{5, 0xff}
setWTimeout(s.conn)
s.conn.Write(buf)
errLogging:
log.Warningln(err)
return false
}
// report hashRand0 then request authentication
// get tun params and tokens
func (n *d5cman) authThenFinishSetting(conn *Conn, t *tunParams) error {
var err error
w := newMsgWriter()
// hash sRand
w.WriteL1Msg(hash256(n.sRand))
// identity
w.WriteL1Msg(n.serializeIdentity())
setWTimeout(conn)
err = w.WriteTo(conn)
if err != nil {
return exception.Spawn(&err, "auth: write connection")
}
setRTimeout(conn)
var buf, params []byte
buf, err = ReadFullByLen(1, conn)
if err != nil {
return exception.Spawn(&err, "auth: read connection")
}
// auth_result
switch buf[0] {
case AUTH_PASS:
default:
return auth.AUTH_FAILED
}
// parse params
params, err = ReadFullByLen(2, conn)
if err != nil {
return exception.Spawn(&err, "param: read connection")
}
t.deserialize(params)
t.token, err = ReadFullByLen(2, conn)
if err != nil {
return exception.Spawn(&err, "token: read connection")
}
if len(t.token) < TKSZ || len(t.token)%TKSZ != 0 {
return ILLEGAL_STATE.Apply("incorrect token")
}
if log.V(log.LV_TOKEN) {
log.Infof("Received tokens size=%d\n", len(t.token)/TKSZ)
}
return nil
}
// read dhPub from server and verify sign
// dhPubLen~1 | dhPub~? | signLen~1 | sign~? | rand
func (n *d5cman) finishDHExchange(conn *Conn) (cf *CipherFactory, err error) {
var dhk, dhkSign []byte
// recv: rhPub~2+256 or ecdhPub~2+32
setRTimeout(conn)
dhk, err = ReadFullByLen(1, conn)
if err != nil {
// maybe: closed conn or reset by peer error caused by dbcHello
if IsClosedError(err) {
return nil, ERR_TIME_ERROR.Apply(NULL)
} else {
exception.Spawn(&err, "dh: read response")
return
}
}
setRTimeout(conn)
dhkSign, err = ReadFullByLen(1, conn)
if err != nil {
exception.Spawn(&err, "dh: read sign")
return
}
if !DSAVerify(n.sPubKey, dhkSign, dhk) {
// MITM ?
return nil, VALIDATION_FAILED
}
key, err := n.dhKey.ComputeKey(dhk)
if err != nil {
exception.Spawn(&err, "dh: compute")
return
}
n.sRand, err = ReadFullByLen(1, conn)
if err != nil {
exception.Spawn(&err, "srand: read connection")
return
}
// setup cipher
cf = NewCipherFactory(n.cipher, key, n.dbcHello)
conn.SetupCipher(cf, n.sRand)
return
}
// verify encrypted message
// hashHello, version
func (n *d5cman) validate(conn *Conn) error {
setRTimeout(conn)
hashHello, err := ReadFullByLen(1, conn)
if err != nil {
return exception.Spawn(&err, "validate: read connection")
}
myHashHello := hash256(n.dbcHello)
if !bytes.Equal(hashHello, myHashHello) {
// MITM ?
return INCONSISTENT_HASH
}
ver, err := ReadFullByLen(1, conn)
if err != nil {
return exception.Spawn(&err, "ver: read connection")
}
if err = compareVersion(ver); err != nil {
return err
}
return nil
}
func (n *d5cman) ResumeSession(p *tunParams, token []byte) (conn *Conn, err error) {
var rawConn net.Conn
rawConn, err = net.DialTimeout("tcp", n.sAddr, GENERAL_SO_TIMEOUT)
if err != nil {
exception.Spawn(&err, "resume: connnecting")
return
}
conn = NewConn(rawConn, nullCipherKit)
obf := makeDbcHello(TYPE_RES, preSharedKey(n.sPubKey))
w := newMsgWriter()
w.WriteMsg(obf)
w.WriteMsg(token)
err = w.WriteTo(conn)
if err != nil {
exception.Spawn(&err, "resume: write")
return
}
conn.SetupCipher(p.cipherFactory, token)
conn.SetId(n.provider, false)
return conn, nil
}
// 1-send dbcHello,dhPub
// dbcHello~256 | dhPubLen~2 | dhPub~?
func (n *d5cman) requestDHExchange(conn *Conn) (err error) {
// obfuscated header
obf := makeDbcHello(TYPE_NEW, preSharedKey(n.sPubKey))
w := newMsgWriter().WriteMsg(obf)
if len(obf) > DPH_P2 {
n.dbcHello = obf[DPH_P2:]
} else {
n.dbcHello = obf
}
// dhke
pub := n.dhKey.ExportPubKey()
w.WriteL2Msg(pub)
setWTimeout(conn)
err = w.WriteTo(conn)
exception.Spawn(&err, "dh: write connection")
return
}