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clientHello.go
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clientHello.go
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package crypt
import (
"strings"
)
type CurveID uint16
type SignatureScheme uint16
const (
statusTypeOCSP uint8 = 1
extensionServerName uint16 = 0
extensionStatusRequest uint16 = 5
extensionSupportedCurves uint16 = 10
extensionSupportedPoints uint16 = 11
extensionSignatureAlgorithms uint16 = 13
extensionALPN uint16 = 16
extensionSCT uint16 = 18 // https://tools.ietf.org/html/rfc6962#section-6
extensionSessionTicket uint16 = 35
extensionNextProtoNeg uint16 = 13172 // not IANA assigned
extensionRenegotiationInfo uint16 = 0xff01
scsvRenegotiation uint16 = 0x00ff
)
type ClientHelloMsg struct {
raw []byte
vers uint16
random []byte
sessionId []byte
cipherSuites []uint16
compressionMethods []uint8
nextProtoNeg bool
serverName string
ocspStapling bool
scts bool
supportedCurves []CurveID
supportedPoints []uint8
ticketSupported bool
sessionTicket []uint8
supportedSignatureAlgorithms []SignatureScheme
secureRenegotiation []byte
secureRenegotiationSupported bool
alpnProtocols []string
}
func (m *ClientHelloMsg) GetServerName() string {
return m.serverName
}
func (m *ClientHelloMsg) Unmarshal(data []byte) bool {
if len(data) < 42 {
return false
}
m.raw = data
m.vers = uint16(data[4])<<8 | uint16(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])
if m.cipherSuites[i] == scsvRenegotiation {
m.secureRenegotiationSupported = true
}
}
data = data[2+cipherSuiteLen:]
if len(data) < 1 {
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 = ""
m.ocspStapling = false
m.ticketSupported = false
m.sessionTicket = nil
m.supportedSignatureAlgorithms = nil
m.alpnProtocols = nil
m.scts = false
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:
d := data[:length]
if len(d) < 2 {
return false
}
namesLen := int(d[0])<<8 | int(d[1])
d = d[2:]
if len(d) != namesLen {
return false
}
for len(d) > 0 {
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[:nameLen])
// An SNI value may not include a
// trailing dot. See
// https://tools.ietf.org/html/rfc6066#section-3.
if strings.HasSuffix(m.serverName, ".") {
return false
}
break
}
d = d[nameLen:]
}
case extensionNextProtoNeg:
if length > 0 {
return false
}
m.nextProtoNeg = true
case extensionStatusRequest:
m.ocspStapling = length > 0 && data[0] == statusTypeOCSP
case extensionSupportedCurves:
// https://tools.ietf.org/html/rfc4492#section-5.5.1
if length < 2 {
return false
}
l := int(data[0])<<8 | int(data[1])
if l%2 == 1 || length != l+2 {
return false
}
numCurves := l / 2
m.supportedCurves = make([]CurveID, numCurves)
d := data[2:]
for i := 0; i < numCurves; i++ {
m.supportedCurves[i] = CurveID(d[0])<<8 | CurveID(d[1])
d = d[2:]
}
case extensionSupportedPoints:
// https://tools.ietf.org/html/rfc4492#section-5.5.2
if length < 1 {
return false
}
l := int(data[0])
if length != l+1 {
return false
}
m.supportedPoints = make([]uint8, l)
copy(m.supportedPoints, data[1:])
case extensionSessionTicket:
// https://tools.ietf.org/html/rfc5077#section-3.2
m.ticketSupported = true
m.sessionTicket = data[:length]
case extensionSignatureAlgorithms:
// https://tools.ietf.org/html/rfc5246#section-7.4.1.4.1
if length < 2 || length&1 != 0 {
return false
}
l := int(data[0])<<8 | int(data[1])
if l != length-2 {
return false
}
n := l / 2
d := data[2:]
m.supportedSignatureAlgorithms = make([]SignatureScheme, n)
for i := range m.supportedSignatureAlgorithms {
m.supportedSignatureAlgorithms[i] = SignatureScheme(d[0])<<8 | SignatureScheme(d[1])
d = d[2:]
}
case extensionRenegotiationInfo:
if length == 0 {
return false
}
d := data[:length]
l := int(d[0])
d = d[1:]
if l != len(d) {
return false
}
m.secureRenegotiation = d
m.secureRenegotiationSupported = true
case extensionALPN:
if length < 2 {
return false
}
l := int(data[0])<<8 | int(data[1])
if l != length-2 {
return false
}
d := data[2:length]
for len(d) != 0 {
stringLen := int(d[0])
d = d[1:]
if stringLen == 0 || stringLen > len(d) {
return false
}
m.alpnProtocols = append(m.alpnProtocols, string(d[:stringLen]))
d = d[stringLen:]
}
case extensionSCT:
m.scts = true
if length != 0 {
return false
}
}
data = data[length:]
}
return true
}