// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package tls

type clientHelloMsg struct {
	raw                []byte
	major, minor       uint8
	random             []byte
	sessionId          []byte
	cipherSuites       []uint16
	compressionMethods []uint8
	nextProtoNeg       bool
	serverName         string
}

func (m *clientHelloMsg) marshal() []byte {
	if m.raw != nil {
		return m.raw
	}

	length := 2 + 32 + 1 + len(m.sessionId) + 2 + len(m.cipherSuites)*2 + 1 + len(m.compressionMethods)
	numExtensions := 0
	extensionsLength := 0
	if m.nextProtoNeg {
		numExtensions++
	}
	if len(m.serverName) > 0 {
		extensionsLength += 5 + len(m.serverName)
		numExtensions++
	}
	if numExtensions > 0 {
		extensionsLength += 4 * numExtensions
		length += 2 + extensionsLength
	}

	x := make([]byte, 4+length)
	x[0] = typeClientHello
	x[1] = uint8(length >> 16)
	x[2] = uint8(length >> 8)
	x[3] = uint8(length)
	x[4] = m.major
	x[5] = m.minor
	copy(x[6:38], m.random)
	x[38] = uint8(len(m.sessionId))
	copy(x[39:39+len(m.sessionId)], m.sessionId)
	y := x[39+len(m.sessionId):]
	y[0] = uint8(len(m.cipherSuites) >> 7)
	y[1] = uint8(len(m.cipherSuites) << 1)
	for i, suite := range m.cipherSuites {
		y[2+i*2] = uint8(suite >> 8)
		y[3+i*2] = uint8(suite)
	}
	z := y[2+len(m.cipherSuites)*2:]
	z[0] = uint8(len(m.compressionMethods))
	copy(z[1:], m.compressionMethods)

	z = z[1+len(m.compressionMethods):]
	if numExtensions > 0 {
		z[0] = byte(extensionsLength >> 8)
		z[1] = byte(extensionsLength)
		z = z[2:]
	}
	if m.nextProtoNeg {
		z[0] = byte(extensionNextProtoNeg >> 8)
		z[1] = byte(extensionNextProtoNeg)
		// The length is always 0
		z = z[4:]
	}
	if len(m.serverName) > 0 {
		z[0] = byte(extensionServerName >> 8)
		z[1] = byte(extensionServerName)
		l := len(m.serverName) + 5
		z[2] = byte(l >> 8)
		z[3] = byte(l)
		z = z[4:]

		// RFC 3546, section 3.1
		//
		// struct {
		//     NameType name_type;
		//     select (name_type) {
		//         case host_name: HostName;
		//     } name;
		// } ServerName;
		//
		// enum {
		//     host_name(0), (255)
		// } NameType;
		//
		// opaque HostName<1..2^16-1>;
		//
		// struct {
		//     ServerName server_name_list<1..2^16-1>
		// } ServerNameList;

		z[1] = 1
		z[3] = byte(len(m.serverName) >> 8)
		z[4] = byte(len(m.serverName))
		copy(z[5:], []byte(m.serverName))
		z = z[l:]
	}

	m.raw = x

	return x
}

func (m *clientHelloMsg) unmarshal(data []byte) bool {
	if len(data) < 43 {
		return false
	}
	m.raw = data
	m.major = data[4]
	m.minor = data[5]
	m.random = data[6:38]
	sessionIdLen := int(data[38])
	if sessionIdLen > 32 || len(data) < 39+sessionIdLen {
		return false
	}
	m.sessionId = data[39 : 39+sessionIdLen]
	data = data[39+sessionIdLen:]
	if len(data) < 2 {
		return false
	}
	// cipherSuiteLen is the number of bytes of cipher suite numbers. Since
	// they are uint16s, the number must be even.
	cipherSuiteLen := int(data[0])<<8 | int(data[1])
	if cipherSuiteLen%2 == 1 || len(data) < 2+cipherSuiteLen {
		return false
	}
	numCipherSuites := cipherSuiteLen / 2
	m.cipherSuites = make([]uint16, numCipherSuites)
	for i := 0; i < numCipherSuites; i++ {
		m.cipherSuites[i] = uint16(data[2+2*i])<<8 | uint16(data[3+2*i])
	}
	data = data[2+cipherSuiteLen:]
	if len(data) < 2 {
		return false
	}
	compressionMethodsLen := int(data[0])
	if len(data) < 1+compressionMethodsLen {
		return false
	}
	m.compressionMethods = data[1 : 1+compressionMethodsLen]

	data = data[1+compressionMethodsLen:]

	m.nextProtoNeg = false
	m.serverName = ""

	if len(data) == 0 {
		// ClientHello is optionally followed by extension data
		return true
	}
	if len(data) < 2 {
		return false
	}

	extensionsLength := int(data[0])<<8 | int(data[1])
	data = data[2:]
	if extensionsLength != len(data) {
		return false
	}

	for len(data) != 0 {
		if len(data) < 4 {
			return false
		}
		extension := uint16(data[0])<<8 | uint16(data[1])
		length := int(data[2])<<8 | int(data[3])
		data = data[4:]
		if len(data) < length {
			return false
		}

		switch extension {
		case extensionServerName:
			if length < 2 {
				return false
			}
			numNames := int(data[0])<<8 | int(data[1])
			d := data[2:]
			for i := 0; i < numNames; i++ {
				if len(d) < 3 {
					return false
				}
				nameType := d[0]
				nameLen := int(d[1])<<8 | int(d[2])
				d = d[3:]
				if len(d) < nameLen {
					return false
				}
				if nameType == 0 {
					m.serverName = string(d[0:nameLen])
					break
				}
				d = d[nameLen:]
			}
		case extensionNextProtoNeg:
			if length > 0 {
				return false
			}
			m.nextProtoNeg = true
		}
		data = data[length:]
	}

	return true
}

type serverHelloMsg struct {
	raw               []byte
	major, minor      uint8
	random            []byte
	sessionId         []byte
	cipherSuite       uint16
	compressionMethod uint8
	nextProtoNeg      bool
	nextProtos        []string
}

func (m *serverHelloMsg) marshal() []byte {
	if m.raw != nil {
		return m.raw
	}

	length := 38 + len(m.sessionId)
	numExtensions := 0
	extensionsLength := 0

	nextProtoLen := 0
	if m.nextProtoNeg {
		numExtensions++
		for _, v := range m.nextProtos {
			nextProtoLen += len(v)
		}
		nextProtoLen += len(m.nextProtos)
		extensionsLength += nextProtoLen
	}
	if numExtensions > 0 {
		extensionsLength += 4 * numExtensions
		length += 2 + extensionsLength
	}

	x := make([]byte, 4+length)
	x[0] = typeServerHello
	x[1] = uint8(length >> 16)
	x[2] = uint8(length >> 8)
	x[3] = uint8(length)
	x[4] = m.major
	x[5] = m.minor
	copy(x[6:38], m.random)
	x[38] = uint8(len(m.sessionId))
	copy(x[39:39+len(m.sessionId)], m.sessionId)
	z := x[39+len(m.sessionId):]
	z[0] = uint8(m.cipherSuite >> 8)
	z[1] = uint8(m.cipherSuite)
	z[2] = uint8(m.compressionMethod)

	z = z[3:]
	if numExtensions > 0 {
		z[0] = byte(extensionsLength >> 8)
		z[1] = byte(extensionsLength)
		z = z[2:]
	}
	if m.nextProtoNeg {
		z[0] = byte(extensionNextProtoNeg >> 8)
		z[1] = byte(extensionNextProtoNeg)
		z[2] = byte(nextProtoLen >> 8)
		z[3] = byte(nextProtoLen)
		z = z[4:]

		for _, v := range m.nextProtos {
			l := len(v)
			if l > 255 {
				l = 255
			}
			z[0] = byte(l)
			copy(z[1:], []byte(v[0:l]))
			z = z[1+l:]
		}
	}

	m.raw = x

	return x
}

func append(slice []string, elem string) []string {
	if len(slice) < cap(slice) {
		slice = slice[0 : len(slice)+1]
		slice[len(slice)-1] = elem
		return slice
	}

	fresh := make([]string, len(slice)+1, cap(slice)*2+1)
	copy(fresh, slice)
	fresh[len(slice)] = elem
	return fresh
}

func (m *serverHelloMsg) unmarshal(data []byte) bool {
	if len(data) < 42 {
		return false
	}
	m.raw = data
	m.major = data[4]
	m.minor = data[5]
	m.random = data[6:38]
	sessionIdLen := int(data[38])
	if sessionIdLen > 32 || len(data) < 39+sessionIdLen {
		return false
	}
	m.sessionId = data[39 : 39+sessionIdLen]
	data = data[39+sessionIdLen:]
	if len(data) < 3 {
		return false
	}
	m.cipherSuite = uint16(data[0])<<8 | uint16(data[1])
	m.compressionMethod = data[2]
	data = data[3:]

	m.nextProtoNeg = false
	m.nextProtos = nil

	if len(data) == 0 {
		// ServerHello is optionally followed by extension data
		return true
	}
	if len(data) < 2 {
		return false
	}

	extensionsLength := int(data[0])<<8 | int(data[1])
	data = data[2:]
	if len(data) != extensionsLength {
		return false
	}

	for len(data) != 0 {
		if len(data) < 4 {
			return false
		}
		extension := uint16(data[0])<<8 | uint16(data[1])
		length := int(data[2])<<8 | int(data[3])
		data = data[4:]
		if len(data) < length {
			return false
		}

		switch extension {
		case extensionNextProtoNeg:
			m.nextProtoNeg = true
			d := data
			for len(d) > 0 {
				l := int(d[0])
				d = d[1:]
				if l == 0 || l > len(d) {
					return false
				}
				m.nextProtos = append(m.nextProtos, string(d[0:l]))
				d = d[l:]
			}
		}
		data = data[length:]
	}

	return true
}

type certificateMsg struct {
	raw          []byte
	certificates [][]byte
}

func (m *certificateMsg) marshal() (x []byte) {
	if m.raw != nil {
		return m.raw
	}

	var i int
	for _, slice := range m.certificates {
		i += len(slice)
	}

	length := 3 + 3*len(m.certificates) + i
	x = make([]byte, 4+length)
	x[0] = typeCertificate
	x[1] = uint8(length >> 16)
	x[2] = uint8(length >> 8)
	x[3] = uint8(length)

	certificateOctets := length - 3
	x[4] = uint8(certificateOctets >> 16)
	x[5] = uint8(certificateOctets >> 8)
	x[6] = uint8(certificateOctets)

	y := x[7:]
	for _, slice := range m.certificates {
		y[0] = uint8(len(slice) >> 16)
		y[1] = uint8(len(slice) >> 8)
		y[2] = uint8(len(slice))
		copy(y[3:], slice)
		y = y[3+len(slice):]
	}

	m.raw = x
	return
}

func (m *certificateMsg) unmarshal(data []byte) bool {
	if len(data) < 7 {
		return false
	}

	m.raw = data
	certsLen := uint32(data[4])<<16 | uint32(data[5])<<8 | uint32(data[6])
	if uint32(len(data)) != certsLen+7 {
		return false
	}

	numCerts := 0
	d := data[7:]
	for certsLen > 0 {
		if len(d) < 4 {
			return false
		}
		certLen := uint32(d[0])<<24 | uint32(d[1])<<8 | uint32(d[2])
		if uint32(len(d)) < 3+certLen {
			return false
		}
		d = d[3+certLen:]
		certsLen -= 3 + certLen
		numCerts++
	}

	m.certificates = make([][]byte, numCerts)
	d = data[7:]
	for i := 0; i < numCerts; i++ {
		certLen := uint32(d[0])<<24 | uint32(d[1])<<8 | uint32(d[2])
		m.certificates[i] = d[3 : 3+certLen]
		d = d[3+certLen:]
	}

	return true
}

type serverHelloDoneMsg struct{}

func (m *serverHelloDoneMsg) marshal() []byte {
	x := make([]byte, 4)
	x[0] = typeServerHelloDone
	return x
}

func (m *serverHelloDoneMsg) unmarshal(data []byte) bool {
	return len(data) == 4
}

type clientKeyExchangeMsg struct {
	raw        []byte
	ciphertext []byte
}

func (m *clientKeyExchangeMsg) marshal() []byte {
	if m.raw != nil {
		return m.raw
	}
	length := len(m.ciphertext) + 2
	x := make([]byte, length+4)
	x[0] = typeClientKeyExchange
	x[1] = uint8(length >> 16)
	x[2] = uint8(length >> 8)
	x[3] = uint8(length)
	x[4] = uint8(len(m.ciphertext) >> 8)
	x[5] = uint8(len(m.ciphertext))
	copy(x[6:], m.ciphertext)

	m.raw = x
	return x
}

func (m *clientKeyExchangeMsg) unmarshal(data []byte) bool {
	m.raw = data
	if len(data) < 7 {
		return false
	}
	cipherTextLen := int(data[4])<<8 | int(data[5])
	if len(data) != 6+cipherTextLen {
		return false
	}
	m.ciphertext = data[6:]
	return true
}

type finishedMsg struct {
	raw        []byte
	verifyData []byte
}

func (m *finishedMsg) marshal() (x []byte) {
	if m.raw != nil {
		return m.raw
	}

	x = make([]byte, 16)
	x[0] = typeFinished
	x[3] = 12
	copy(x[4:], m.verifyData)
	m.raw = x
	return
}

func (m *finishedMsg) unmarshal(data []byte) bool {
	m.raw = data
	if len(data) != 4+12 {
		return false
	}
	m.verifyData = data[4:]
	return true
}

type nextProtoMsg struct {
	raw   []byte
	proto string
}

func (m *nextProtoMsg) marshal() []byte {
	if m.raw != nil {
		return m.raw
	}
	l := len(m.proto)
	if l > 255 {
		l = 255
	}

	padding := 32 - (l+2)%32
	length := l + padding + 2
	x := make([]byte, length+4)
	x[0] = typeNextProtocol
	x[1] = uint8(length >> 16)
	x[2] = uint8(length >> 8)
	x[3] = uint8(length)

	y := x[4:]
	y[0] = byte(l)
	copy(y[1:], []byte(m.proto[0:l]))
	y = y[1+l:]
	y[0] = byte(padding)

	m.raw = x

	return x
}

func (m *nextProtoMsg) unmarshal(data []byte) bool {
	m.raw = data

	if len(data) < 5 {
		return false
	}
	data = data[4:]
	protoLen := int(data[0])
	data = data[1:]
	if len(data) < protoLen {
		return false
	}
	m.proto = string(data[0:protoLen])
	data = data[protoLen:]

	if len(data) < 1 {
		return false
	}
	paddingLen := int(data[0])
	data = data[1:]
	if len(data) != paddingLen {
		return false
	}

	return true
}