mirror of
https://github.com/apernet/OpenGFW.git
synced 2024-11-13 13:59:24 +08:00
refactor: Improve parsing docs
Reveal intentions by: - extracting magic numbers into constants - changing function names with >1 responsibilities - documenting non-obvious behaviors.
This commit is contained in:
macie
parent
4257788f33
commit
3bd02ed46e
@ -5,7 +5,26 @@ import (
|
||||
"github.com/apernet/OpenGFW/analyzer/utils"
|
||||
)
|
||||
|
||||
func ParseTLSClientHello(chBuf *utils.ByteBuffer) analyzer.PropMap {
|
||||
// TLS record types.
|
||||
const (
|
||||
RecordTypeHandshake = 0x16
|
||||
)
|
||||
|
||||
// TLS handshake message types.
|
||||
const (
|
||||
TypeClientHello = 0x01
|
||||
TypeServerHello = 0x02
|
||||
)
|
||||
|
||||
// TLS extension numbers.
|
||||
const (
|
||||
extServerName = 0x0000
|
||||
extALPN = 0x0010
|
||||
extSupportedVersions = 0x002b
|
||||
extEncryptedClientHello = 0xfe0d
|
||||
)
|
||||
|
||||
func ParseTLSClientHelloMsgData(chBuf *utils.ByteBuffer) analyzer.PropMap {
|
||||
var ok bool
|
||||
m := make(analyzer.PropMap)
|
||||
// Version, random & session ID length combined are within 35 bytes,
|
||||
@ -76,7 +95,7 @@ func ParseTLSClientHello(chBuf *utils.ByteBuffer) analyzer.PropMap {
|
||||
return m
|
||||
}
|
||||
|
||||
func ParseTLSServerHello(shBuf *utils.ByteBuffer) analyzer.PropMap {
|
||||
func ParseTLSServerHelloMsgData(shBuf *utils.ByteBuffer) analyzer.PropMap {
|
||||
var ok bool
|
||||
m := make(analyzer.PropMap)
|
||||
// Version, random & session ID length combined are within 35 bytes,
|
||||
@ -133,7 +152,7 @@ func ParseTLSServerHello(shBuf *utils.ByteBuffer) analyzer.PropMap {
|
||||
|
||||
func parseTLSExtensions(extType uint16, extDataBuf *utils.ByteBuffer, m analyzer.PropMap) bool {
|
||||
switch extType {
|
||||
case 0x0000: // SNI
|
||||
case extServerName:
|
||||
ok := extDataBuf.Skip(2) // Ignore list length, we only care about the first entry for now
|
||||
if !ok {
|
||||
// Not enough data for list length
|
||||
@ -154,7 +173,7 @@ func parseTLSExtensions(extType uint16, extDataBuf *utils.ByteBuffer, m analyzer
|
||||
// Not enough data for SNI
|
||||
return false
|
||||
}
|
||||
case 0x0010: // ALPN
|
||||
case extALPN:
|
||||
ok := extDataBuf.Skip(2) // Ignore list length, as we read until the end
|
||||
if !ok {
|
||||
// Not enough data for list length
|
||||
@ -175,7 +194,7 @@ func parseTLSExtensions(extType uint16, extDataBuf *utils.ByteBuffer, m analyzer
|
||||
alpnList = append(alpnList, alpn)
|
||||
}
|
||||
m["alpn"] = alpnList
|
||||
case 0x002b: // Supported Versions
|
||||
case extSupportedVersions:
|
||||
if extDataBuf.Len() == 2 {
|
||||
// Server only selects one version
|
||||
m["supported_versions"], _ = extDataBuf.GetUint16(false, true)
|
||||
@ -197,7 +216,7 @@ func parseTLSExtensions(extType uint16, extDataBuf *utils.ByteBuffer, m analyzer
|
||||
}
|
||||
m["supported_versions"] = versions
|
||||
}
|
||||
case 0xfe0d: // ECH
|
||||
case extEncryptedClientHello:
|
||||
// We can't parse ECH for now, just set a flag
|
||||
m["ech"] = true
|
||||
}
|
||||
|
||||
@ -44,12 +44,12 @@ type tlsStream struct {
|
||||
func newTLSStream(logger analyzer.Logger) *tlsStream {
|
||||
s := &tlsStream{logger: logger, reqBuf: &utils.ByteBuffer{}, respBuf: &utils.ByteBuffer{}}
|
||||
s.reqLSM = utils.NewLinearStateMachine(
|
||||
s.tlsClientHelloSanityCheck,
|
||||
s.parseClientHello,
|
||||
s.tlsClientHelloPreprocess,
|
||||
s.parseClientHelloData,
|
||||
)
|
||||
s.respLSM = utils.NewLinearStateMachine(
|
||||
s.tlsServerHelloSanityCheck,
|
||||
s.parseServerHello,
|
||||
s.tlsServerHelloPreprocess,
|
||||
s.parseServerHelloData,
|
||||
)
|
||||
return s
|
||||
}
|
||||
@ -89,61 +89,105 @@ func (s *tlsStream) Feed(rev, start, end bool, skip int, data []byte) (u *analyz
|
||||
return update, cancelled || (s.reqDone && s.respDone)
|
||||
}
|
||||
|
||||
func (s *tlsStream) tlsClientHelloSanityCheck() utils.LSMAction {
|
||||
data, ok := s.reqBuf.Get(9, true)
|
||||
// tlsClientHelloPreprocess validates ClientHello message.
|
||||
//
|
||||
// During validation, message header and first handshake header may be removed
|
||||
// from `s.reqBuf`.
|
||||
func (s *tlsStream) tlsClientHelloPreprocess() utils.LSMAction {
|
||||
// headers size: content type (1 byte) + legacy protocol version (2 bytes) +
|
||||
// + content length (2 bytes) + message type (1 byte) +
|
||||
// + handshake length (3 bytes)
|
||||
const headersSize = 9
|
||||
|
||||
// minimal data size: protocol version (2 bytes) + random (32 bytes) +
|
||||
// + session ID (1 byte) + cipher suites (4 bytes) +
|
||||
// + compression methods (2 bytes) + no extensions
|
||||
const minDataSize = 41
|
||||
|
||||
header, ok := s.reqBuf.Get(headersSize, true)
|
||||
if !ok {
|
||||
// not a full header yet
|
||||
return utils.LSMActionPause
|
||||
}
|
||||
if data[0] != 0x16 || data[5] != 0x01 {
|
||||
// Not a TLS handshake, or not a client hello
|
||||
|
||||
if header[0] != internal.RecordTypeHandshake || header[5] != internal.TypeClientHello {
|
||||
return utils.LSMActionCancel
|
||||
}
|
||||
s.clientHelloLen = int(data[6])<<16 | int(data[7])<<8 | int(data[8])
|
||||
if s.clientHelloLen < 41 {
|
||||
// 2 (Protocol Version) +
|
||||
// 32 (Random) +
|
||||
// 1 (Session ID Length) +
|
||||
// 2 (Cipher Suites Length) +_ws.col.protocol == "TLSv1.3"
|
||||
// 2 (Cipher Suite) +
|
||||
// 1 (Compression Methods Length) +
|
||||
// 1 (Compression Method) +
|
||||
// No extensions
|
||||
// This should be the bare minimum for a client hello
|
||||
|
||||
s.clientHelloLen = int(header[6])<<16 | int(header[7])<<8 | int(header[8])
|
||||
if s.clientHelloLen < minDataSize {
|
||||
return utils.LSMActionCancel
|
||||
}
|
||||
|
||||
// TODO: something is missing. See:
|
||||
// const messageHeaderSize = 4
|
||||
// fullMessageLen := int(header[3])<<8 | int(header[4])
|
||||
// msgNo := fullMessageLen / int(messageHeaderSize+s.serverHelloLen)
|
||||
// if msgNo != 1 {
|
||||
// // what here?
|
||||
// }
|
||||
// if messageNo != int(messageNo) {
|
||||
// // what here?
|
||||
// }
|
||||
|
||||
return utils.LSMActionNext
|
||||
}
|
||||
|
||||
func (s *tlsStream) tlsServerHelloSanityCheck() utils.LSMAction {
|
||||
data, ok := s.respBuf.Get(9, true)
|
||||
// tlsServerHelloPreprocess validates ServerHello message.
|
||||
//
|
||||
// During validation, message header and first handshake header may be removed
|
||||
// from `s.reqBuf`.
|
||||
func (s *tlsStream) tlsServerHelloPreprocess() utils.LSMAction {
|
||||
// header size: content type (1 byte) + legacy protocol version (2 byte) +
|
||||
// + content length (2 byte) + message type (1 byte) +
|
||||
// + handshake length (3 byte)
|
||||
const headersSize = 9
|
||||
|
||||
// minimal data size: server version (2 byte) + random (32 byte) +
|
||||
// + session ID (>=1 byte) + cipher suite (2 byte) +
|
||||
// + compression method (1 byte) + no extensions
|
||||
const minDataSize = 38
|
||||
|
||||
header, ok := s.respBuf.Get(headersSize, true)
|
||||
if !ok {
|
||||
// not a full header yet
|
||||
return utils.LSMActionPause
|
||||
}
|
||||
if data[0] != 0x16 || data[5] != 0x02 {
|
||||
// Not a TLS handshake, or not a server hello
|
||||
|
||||
if header[0] != internal.RecordTypeHandshake || header[5] != internal.TypeServerHello {
|
||||
return utils.LSMActionCancel
|
||||
}
|
||||
s.serverHelloLen = int(data[6])<<16 | int(data[7])<<8 | int(data[8])
|
||||
if s.serverHelloLen < 38 {
|
||||
// 2 (Protocol Version) +
|
||||
// 32 (Random) +
|
||||
// 1 (Session ID Length) +
|
||||
// 2 (Cipher Suite) +
|
||||
// 1 (Compression Method) +
|
||||
// No extensions
|
||||
// This should be the bare minimum for a server hello
|
||||
|
||||
s.serverHelloLen = int(header[6])<<16 | int(header[7])<<8 | int(header[8])
|
||||
if s.serverHelloLen < minDataSize {
|
||||
return utils.LSMActionCancel
|
||||
}
|
||||
|
||||
// TODO: something is missing. See example:
|
||||
// const messageHeaderSize = 4
|
||||
// fullMessageLen := int(header[3])<<8 | int(header[4])
|
||||
// msgNo := fullMessageLen / int(messageHeaderSize+s.serverHelloLen)
|
||||
// if msgNo != 1 {
|
||||
// // what here?
|
||||
// }
|
||||
// if messageNo != int(messageNo) {
|
||||
// // what here?
|
||||
// }
|
||||
|
||||
return utils.LSMActionNext
|
||||
}
|
||||
|
||||
func (s *tlsStream) parseClientHello() utils.LSMAction {
|
||||
// parseClientHelloData converts valid ClientHello message data (without
|
||||
// headers) into `analyzer.PropMap`.
|
||||
//
|
||||
// Parsing error may leave `s.reqBuf` in an unusable state.
|
||||
func (s *tlsStream) parseClientHelloData() utils.LSMAction {
|
||||
chBuf, ok := s.reqBuf.GetSubBuffer(s.clientHelloLen, true)
|
||||
if !ok {
|
||||
// Not a full client hello yet
|
||||
return utils.LSMActionPause
|
||||
}
|
||||
m := internal.ParseTLSClientHello(chBuf)
|
||||
m := internal.ParseTLSClientHelloMsgData(chBuf)
|
||||
if m == nil {
|
||||
return utils.LSMActionCancel
|
||||
} else {
|
||||
@ -153,13 +197,17 @@ func (s *tlsStream) parseClientHello() utils.LSMAction {
|
||||
}
|
||||
}
|
||||
|
||||
func (s *tlsStream) parseServerHello() utils.LSMAction {
|
||||
// parseServerHelloData converts valid ServerHello message data (without
|
||||
// headers) into `analyzer.PropMap`.
|
||||
//
|
||||
// Parsing error may leave `s.respBuf` in an unusable state.
|
||||
func (s *tlsStream) parseServerHelloData() utils.LSMAction {
|
||||
shBuf, ok := s.respBuf.GetSubBuffer(s.serverHelloLen, true)
|
||||
if !ok {
|
||||
// Not a full server hello yet
|
||||
return utils.LSMActionPause
|
||||
}
|
||||
m := internal.ParseTLSServerHello(shBuf)
|
||||
m := internal.ParseTLSServerHelloMsgData(shBuf)
|
||||
if m == nil {
|
||||
return utils.LSMActionCancel
|
||||
} else {
|
||||
|
||||
@ -36,41 +36,40 @@ type quicStream struct {
|
||||
}
|
||||
|
||||
func (s *quicStream) Feed(rev bool, data []byte) (u *analyzer.PropUpdate, done bool) {
|
||||
// minimal data size: protocol version (2 bytes) + random (32 bytes) +
|
||||
// + session ID (1 byte) + cipher suites (4 bytes) +
|
||||
// + compression methods (2 bytes) + no extensions
|
||||
const minDataSize = 41
|
||||
|
||||
if rev {
|
||||
// We don't support server direction for now
|
||||
s.invalidCount++
|
||||
return nil, s.invalidCount >= quicInvalidCountThreshold
|
||||
}
|
||||
|
||||
pl, err := quic.ReadCryptoPayload(data)
|
||||
if err != nil || len(pl) < 4 {
|
||||
if err != nil || len(pl) < 4 { // FIXME: isn't length checked inside quic.ReadCryptoPayload? Also, what about error handling?
|
||||
s.invalidCount++
|
||||
return nil, s.invalidCount >= quicInvalidCountThreshold
|
||||
}
|
||||
// Should be a TLS client hello
|
||||
if pl[0] != 0x01 {
|
||||
// Not a client hello
|
||||
|
||||
if pl[0] != internal.TypeClientHello {
|
||||
s.invalidCount++
|
||||
return nil, s.invalidCount >= quicInvalidCountThreshold
|
||||
}
|
||||
|
||||
chLen := int(pl[1])<<16 | int(pl[2])<<8 | int(pl[3])
|
||||
if chLen < 41 {
|
||||
// 2 (Protocol Version) +
|
||||
// 32 (Random) +
|
||||
// 1 (Session ID Length) +
|
||||
// 2 (Cipher Suites Length) +_ws.col.protocol == "TLSv1.3"
|
||||
// 2 (Cipher Suite) +
|
||||
// 1 (Compression Methods Length) +
|
||||
// 1 (Compression Method) +
|
||||
// No extensions
|
||||
// This should be the bare minimum for a client hello
|
||||
if chLen < minDataSize {
|
||||
s.invalidCount++
|
||||
return nil, s.invalidCount >= quicInvalidCountThreshold
|
||||
}
|
||||
m := internal.ParseTLSClientHello(&utils.ByteBuffer{Buf: pl[4:]})
|
||||
|
||||
m := internal.ParseTLSClientHelloMsgData(&utils.ByteBuffer{Buf: pl[4:]})
|
||||
if m == nil {
|
||||
s.invalidCount++
|
||||
return nil, s.invalidCount >= quicInvalidCountThreshold
|
||||
}
|
||||
|
||||
return &analyzer.PropUpdate{
|
||||
Type: analyzer.PropUpdateMerge,
|
||||
M: analyzer.PropMap{"req": m},
|
||||
|
||||
Loading…
Reference in New Issue
Block a user