添加 github.com/pion/dtls 代码

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

@@ -0,0 +1,104 @@
+package ciphersuite
+
+import (
+	"crypto/aes"
+	"crypto/rand"
+	"encoding/binary"
+	"fmt"
+
+	"github.com/pion/dtls/v2/pkg/crypto/ccm"
+	"github.com/pion/dtls/v2/pkg/protocol"
+	"github.com/pion/dtls/v2/pkg/protocol/recordlayer"
+)
+
+// CCMTagLen is the length of Authentication Tag
+type CCMTagLen int
+
+// CCM Enums
+const (
+	CCMTagLength8  CCMTagLen = 8
+	CCMTagLength   CCMTagLen = 16
+	ccmNonceLength           = 12
+)
+
+// CCM Provides an API to Encrypt/Decrypt DTLS 1.2 Packets
+type CCM struct {
+	localCCM, remoteCCM         ccm.CCM
+	localWriteIV, remoteWriteIV []byte
+	tagLen                      CCMTagLen
+}
+
+// NewCCM creates a DTLS GCM Cipher
+func NewCCM(tagLen CCMTagLen, localKey, localWriteIV, remoteKey, remoteWriteIV []byte) (*CCM, error) {
+	localBlock, err := aes.NewCipher(localKey)
+	if err != nil {
+		return nil, err
+	}
+	localCCM, err := ccm.NewCCM(localBlock, int(tagLen), ccmNonceLength)
+	if err != nil {
+		return nil, err
+	}
+
+	remoteBlock, err := aes.NewCipher(remoteKey)
+	if err != nil {
+		return nil, err
+	}
+	remoteCCM, err := ccm.NewCCM(remoteBlock, int(tagLen), ccmNonceLength)
+	if err != nil {
+		return nil, err
+	}
+
+	return &CCM{
+		localCCM:      localCCM,
+		localWriteIV:  localWriteIV,
+		remoteCCM:     remoteCCM,
+		remoteWriteIV: remoteWriteIV,
+		tagLen:        tagLen,
+	}, nil
+}
+
+// Encrypt encrypt a DTLS RecordLayer message
+func (c *CCM) Encrypt(pkt *recordlayer.RecordLayer, raw []byte) ([]byte, error) {
+	payload := raw[recordlayer.HeaderSize:]
+	raw = raw[:recordlayer.HeaderSize]
+
+	nonce := append(append([]byte{}, c.localWriteIV[:4]...), make([]byte, 8)...)
+	if _, err := rand.Read(nonce[4:]); err != nil {
+		return nil, err
+	}
+
+	additionalData := generateAEADAdditionalData(&pkt.Header, len(payload))
+	encryptedPayload := c.localCCM.Seal(nil, nonce, payload, additionalData)
+
+	encryptedPayload = append(nonce[4:], encryptedPayload...)
+	raw = append(raw, encryptedPayload...)
+
+	// Update recordLayer size to include explicit nonce
+	binary.BigEndian.PutUint16(raw[recordlayer.HeaderSize-2:], uint16(len(raw)-recordlayer.HeaderSize))
+	return raw, nil
+}
+
+// Decrypt decrypts a DTLS RecordLayer message
+func (c *CCM) Decrypt(in []byte) ([]byte, error) {
+	var h recordlayer.Header
+	err := h.Unmarshal(in)
+	switch {
+	case err != nil:
+		return nil, err
+	case h.ContentType == protocol.ContentTypeChangeCipherSpec:
+		// Nothing to encrypt with ChangeCipherSpec
+		return in, nil
+	case len(in) <= (8 + recordlayer.HeaderSize):
+		return nil, errNotEnoughRoomForNonce
+	}
+
+	nonce := append(append([]byte{}, c.remoteWriteIV[:4]...), in[recordlayer.HeaderSize:recordlayer.HeaderSize+8]...)
+	out := in[recordlayer.HeaderSize+8:]
+
+	additionalData := generateAEADAdditionalData(&h, len(out)-int(c.tagLen))
+	out, err = c.remoteCCM.Open(out[:0], nonce, out, additionalData)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %v", errDecryptPacket, err)
+	}
+	return append(in[:recordlayer.HeaderSize], out...), nil
+}