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package quic
import (
"crypto/hmac"
"crypto/rand"
"crypto/sha256"
"hash"
"sync"
"github.com/quic-go/quic-go/internal/protocol"
)
type statelessResetter struct {
mx sync.Mutex
h hash.Hash
}
// newStatelessRetter creates a new stateless reset generator.
// It is valid to use a nil key. In that case, a random key will be used.
// This makes is impossible for on-path attackers to shut down established connections.
func newStatelessResetter(key *StatelessResetKey) *statelessResetter {
var h hash.Hash
if key != nil {
h = hmac.New(sha256.New, key[:])
} else {
b := make([]byte, 32)
_, _ = rand.Read(b)
h = hmac.New(sha256.New, b)
}
return &statelessResetter{h: h}
}
func (r *statelessResetter) GetStatelessResetToken(connID protocol.ConnectionID) protocol.StatelessResetToken {
r.mx.Lock()
defer r.mx.Unlock()
var token protocol.StatelessResetToken
r.h.Write(connID.Bytes())
copy(token[:], r.h.Sum(nil))
r.h.Reset()
return token
}
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