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crypto.go
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crypto.go
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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at https://mozilla.org/MPL/2.0/.
package dtls
import (
"bytes"
"crypto/elliptic"
"crypto/hmac"
"crypto/sha256"
"encoding/binary"
"fmt"
)
const (
AadAuthLen int = 13
)
func newNonce(iv []byte, epoch uint16, seq uint64) []byte {
nonce := new(bytes.Buffer)
nonce.Write(iv)
seq += uint64(epoch) << 48
binary.Write(nonce, binary.BigEndian, seq)
return nonce.Bytes()
}
func newNonceFromBytes(iv []byte, data []byte) []byte {
nonce := new(bytes.Buffer)
nonce.Write(iv)
nonce.Write(data)
return nonce.Bytes()
}
func newAad(s *session, epoch uint16, seq uint64, msgType uint8, cid []byte, dataLen uint16) []byte {
w := newByteWriter()
if cid != nil {
if s.cidVersion == DtlsExtConnectionIdLegacy {
w.PutUint16(epoch)
w.PutUint48(seq)
w.PutUint8(msgType)
w.PutUint16(DtlsVersion12)
w.PutBytes(cid)
w.PutUint8(uint8(len(cid)))
w.PutUint16(dataLen)
} else if s.cidVersion == DtlsExtConnectionId {
w.PutBytes([]byte{0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF})
w.PutUint8(msgType)
w.PutUint8(uint8(len(cid)))
w.PutUint8(msgType)
w.PutUint16(DtlsVersion12)
w.PutUint16(epoch)
w.PutUint48(seq)
w.PutBytes(cid)
w.PutUint16(dataLen)
}
} else {
w.PutUint16(epoch)
w.PutUint48(seq)
w.PutUint8(msgType)
w.PutUint16(DtlsVersion12)
w.PutUint16(dataLen)
}
return w.Bytes()
}
type KeyBlock struct {
MasterSecret []byte `json:"masterSecret"`
ClientMac []byte `json:"clientMac"`
ServerMac []byte `json:"serverMac"`
ClientWriteKey []byte `json:"clientWriteKey"`
ServerWriteKey []byte `json:"serverWriteKey"`
ClientIV []byte `json:"clientIV"`
ServerIV []byte `json:"serverIV"`
}
func (kb *KeyBlock) Print() string {
return fmt.Sprintf("ClientWriteKey[%X], ServerWriteKey[%X], ClientIV[%X], ServerIV[%X]", kb.ClientWriteKey, kb.ServerWriteKey, kb.ClientIV, kb.ServerIV)
}
func generatePskPreMasterSecret(psk []byte) []byte {
zeroBuffer := make([]byte, len(psk))
w := newByteWriter()
w.PutUint16(uint16(len(psk)))
w.PutBytes(zeroBuffer)
w.PutUint16(uint16(len(psk)))
w.PutBytes(psk)
return w.Bytes()
}
func generateEccPreMasterSecret(publicKey []byte, privateKey []byte) []byte {
x, y := elliptic.Unmarshal(elliptic.P256(), publicKey)
result, _ := elliptic.P256().ScalarMult(x, y, privateKey)
preMasterSecret := make([]byte, (elliptic.P256().Params().BitSize+7)>>3)
resultBytes := result.Bytes()
copy(preMasterSecret[len(preMasterSecret)-len(resultBytes):], resultBytes)
return resultBytes
}
func generatePrf(key, random1, random2 []byte, label string, keyLen int) []byte {
buf := make([]byte, 0, keyLen)
seed := hmac.New(sha256.New, key)
seed.Write([]byte(label))
seed.Write(random1)
seed.Write(random2)
seedHash := seed.Sum(nil)
hash := hmac.New(sha256.New, key)
for len(buf)+len(seedHash) < keyLen {
hash.Reset()
hash.Write(seedHash)
hash.Write([]byte(label))
hash.Write(random1)
hash.Write(random2)
tmp := hash.Sum(nil)
buf = append(buf, tmp...)
seed.Reset()
seed.Write(seedHash)
seedHash = seed.Sum(nil)
}
hash.Reset()
hash.Write(seedHash)
hash.Write([]byte(label))
hash.Write(random1)
hash.Write(random2)
tmp := hash.Sum(nil)
buf = append(buf, tmp...)
return buf[:keyLen]
}