implement parsing of sample CHLO crypto stream

crypto_stream.go

@@ -0,0 +1,89 @@
+package quic
+
+import (
+	"encoding/binary"
+	"errors"
+)
+
+// A Tag in the QUIC crypto
+type Tag uint32
+
+const (
+	// TagCHLO is a client hello
+	TagCHLO Tag = 'C' + 'H'<<8 + 'L'<<16 + 'O'<<24
+
+	// TagPAD is padding
+	TagPAD Tag = 'P' + 'A'<<8 + 'D'<<16
+	// TagSNI is the server name indication
+	TagSNI Tag = 'S' + 'N'<<8 + 'I'<<16
+	// TagVER is the QUIC version
+	TagVER Tag = 'V' + 'E'<<8 + 'R'<<16
+	// TagCCS is the hash of the common certificate sets
+	TagCCS Tag = 'C' + 'C'<<8 + 'S'<<16
+	// TagMSPC is max streams per connection
+	TagMSPC Tag = 'M' + 'S'<<8 + 'P'<<16 + 'C'<<24
+	// TagUAID is the user agent ID
+	TagUAID Tag = 'U' + 'A'<<8 + 'I'<<16 + 'D'<<24
+	// TagTCID is truncation of the connection ID
+	TagTCID Tag = 'T' + 'C'<<8 + 'I'<<16 + 'D'<<24
+	// TagPDMD is the proof demand
+	TagPDMD Tag = 'P' + 'D'<<8 + 'M'<<16 + 'D'<<24
+	// TagSRBF is the socket receive buffer
+	TagSRBF Tag = 'S' + 'R'<<8 + 'B'<<16 + 'F'<<24
+	// TagICSL is the idle connection state lifetime
+	TagICSL Tag = 'I' + 'C'<<8 + 'S'<<16 + 'L'<<24
+	// TagNONP is the client proof nonce
+	TagNONP Tag = 'N' + 'O'<<8 + 'N'<<16 + 'P'<<24
+	// TagSCLS is the silently close timeout
+	TagSCLS Tag = 'S' + 'C'<<8 + 'L'<<16 + 'S'<<24
+	// TagCSCT is the signed cert timestamp (RFC6962) of leaf cert
+	TagCSCT Tag = 'C' + 'S'<<8 + 'C'<<16 + 'T'<<24
+	// TagCOPT are the connection options
+	TagCOPT Tag = 'C' + 'O'<<8 + 'P'<<16 + 'T'<<24
+	// TagCFCW is the initial session/connection flow control receive window
+	TagCFCW Tag = 'C' + 'F'<<8 + 'C'<<16 + 'W'<<24
+	// TagSFCW is the initial stream flow control receive window.
+	TagSFCW Tag = 'S' + 'F'<<8 + 'C'<<16 + 'W'<<24
+)
+
+var (
+	errCryptoMessageEOF = errors.New("ParseCryptoMessage: Unexpected EOF")
+)
+
+// ParseCryptoMessage reads a crypto message
+func ParseCryptoMessage(data []byte) (Tag, map[Tag][]byte, error) {
+	if len(data) < 8 {
+		return 0, nil, errCryptoMessageEOF
+	}
+
+	messageTag := Tag(binary.LittleEndian.Uint32(data[0:4]))
+	nPairs := int(binary.LittleEndian.Uint16(data[4:6]))
+
+	data = data[8:]
+
+	// We need space for at least nPairs * 8 bytes
+	if len(data) < int(nPairs)*8 {
+		return 0, nil, errCryptoMessageEOF
+	}
+
+	resultMap := map[Tag][]byte{}
+
+	dataStart := 0
+	for indexPos := 0; indexPos < nPairs*8; indexPos += 8 {
+		// We know from the check above that data is long enough for the index
+		tag := Tag(binary.LittleEndian.Uint32(data[indexPos : indexPos+4]))
+		dataEnd := int(binary.LittleEndian.Uint32(data[indexPos+4 : indexPos+8]))
+
+		if dataEnd > len(data) {
+			return 0, nil, errCryptoMessageEOF
+		}
+		if dataEnd < dataStart {
+			return 0, nil, errors.New("invalid end offset in crypto message")
+		}
+
+		resultMap[tag] = data[nPairs*8+dataStart : nPairs*8+dataEnd]
+		dataStart = dataEnd
+	}
+
+	return messageTag, resultMap, nil
+}