75 lines
1.8 KiB
Go
75 lines
1.8 KiB
Go
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package crypto
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import (
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"crypto/aes"
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"crypto/cipher"
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"encoding/binary"
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"errors"
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"github.com/lucas-clemente/quic-go/internal/protocol"
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)
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type aeadAESGCM struct {
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otherIV []byte
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myIV []byte
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encrypter cipher.AEAD
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decrypter cipher.AEAD
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}
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var _ AEAD = &aeadAESGCM{}
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const ivLen = 12
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// NewAEADAESGCM creates a AEAD using AES-GCM
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func NewAEADAESGCM(otherKey []byte, myKey []byte, otherIV []byte, myIV []byte) (AEAD, error) {
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// the IVs need to be at least 8 bytes long, otherwise we can't compute the nonce
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if len(otherIV) != ivLen || len(myIV) != ivLen {
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return nil, errors.New("AES-GCM: expected 12 byte IVs")
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}
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encrypterCipher, err := aes.NewCipher(myKey)
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if err != nil {
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return nil, err
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}
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encrypter, err := cipher.NewGCM(encrypterCipher)
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if err != nil {
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return nil, err
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}
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decrypterCipher, err := aes.NewCipher(otherKey)
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if err != nil {
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return nil, err
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}
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decrypter, err := cipher.NewGCM(decrypterCipher)
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if err != nil {
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return nil, err
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}
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return &aeadAESGCM{
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otherIV: otherIV,
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myIV: myIV,
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encrypter: encrypter,
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decrypter: decrypter,
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}, nil
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}
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func (aead *aeadAESGCM) Open(dst, src []byte, packetNumber protocol.PacketNumber, associatedData []byte) ([]byte, error) {
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return aead.decrypter.Open(dst, aead.makeNonce(aead.otherIV, packetNumber), src, associatedData)
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}
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func (aead *aeadAESGCM) Seal(dst, src []byte, packetNumber protocol.PacketNumber, associatedData []byte) []byte {
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return aead.encrypter.Seal(dst, aead.makeNonce(aead.myIV, packetNumber), src, associatedData)
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}
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func (aead *aeadAESGCM) makeNonce(iv []byte, packetNumber protocol.PacketNumber) []byte {
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nonce := make([]byte, ivLen)
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binary.BigEndian.PutUint64(nonce[ivLen-8:], uint64(packetNumber))
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for i := 0; i < ivLen; i++ {
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nonce[i] ^= iv[i]
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}
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return nonce
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}
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func (aead *aeadAESGCM) Overhead() int {
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return aead.encrypter.Overhead()
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}
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