添加 github.com/pion/dtls 代码

dtls-2.0.9/pkg/crypto/ciphersuite/ciphersuite.go

@@ -0,0 +1,72 @@
+// Package ciphersuite provides the crypto operations needed for a DTLS CipherSuite
+package ciphersuite
+
+import (
+	"encoding/binary"
+	"errors"
+
+	"github.com/pion/dtls/v2/pkg/protocol"
+	"github.com/pion/dtls/v2/pkg/protocol/recordlayer"
+)
+
+var (
+	errNotEnoughRoomForNonce = &protocol.InternalError{Err: errors.New("buffer not long enough to contain nonce")} //nolint:goerr113
+	errDecryptPacket         = &protocol.TemporaryError{Err: errors.New("failed to decrypt packet")}               //nolint:goerr113
+	errInvalidMAC            = &protocol.TemporaryError{Err: errors.New("invalid mac")}                            //nolint:goerr113
+)
+
+func generateAEADAdditionalData(h *recordlayer.Header, payloadLen int) []byte {
+	var additionalData [13]byte
+	// SequenceNumber MUST be set first
+	// we only want uint48, clobbering an extra 2 (using uint64, Golang doesn't have uint48)
+	binary.BigEndian.PutUint64(additionalData[:], h.SequenceNumber)
+	binary.BigEndian.PutUint16(additionalData[:], h.Epoch)
+	additionalData[8] = byte(h.ContentType)
+	additionalData[9] = h.Version.Major
+	additionalData[10] = h.Version.Minor
+	binary.BigEndian.PutUint16(additionalData[len(additionalData)-2:], uint16(payloadLen))
+
+	return additionalData[:]
+}
+
+// examinePadding returns, in constant time, the length of the padding to remove
+// from the end of payload. It also returns a byte which is equal to 255 if the
+// padding was valid and 0 otherwise. See RFC 2246, Section 6.2.3.2.
+//
+// https://github.com/golang/go/blob/039c2081d1178f90a8fa2f4e6958693129f8de33/src/crypto/tls/conn.go#L245
+func examinePadding(payload []byte) (toRemove int, good byte) {
+	if len(payload) < 1 {
+		return 0, 0
+	}
+
+	paddingLen := payload[len(payload)-1]
+	t := uint(len(payload)-1) - uint(paddingLen)
+	// if len(payload) >= (paddingLen - 1) then the MSB of t is zero
+	good = byte(int32(^t) >> 31)
+
+	// The maximum possible padding length plus the actual length field
+	toCheck := 256
+	// The length of the padded data is public, so we can use an if here
+	if toCheck > len(payload) {
+		toCheck = len(payload)
+	}
+
+	for i := 0; i < toCheck; i++ {
+		t := uint(paddingLen) - uint(i)
+		// if i <= paddingLen then the MSB of t is zero
+		mask := byte(int32(^t) >> 31)
+		b := payload[len(payload)-1-i]
+		good &^= mask&paddingLen ^ mask&b
+	}
+
+	// We AND together the bits of good and replicate the result across
+	// all the bits.
+	good &= good << 4
+	good &= good << 2
+	good &= good << 1
+	good = uint8(int8(good) >> 7)
+
+	toRemove = int(paddingLen) + 1
+
+	return toRemove, good
+}