50 lines
1.4 KiB
Go
50 lines
1.4 KiB
Go
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package crypto
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import (
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"github.com/bifurcation/mint"
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"github.com/lucas-clemente/quic-go/internal/protocol"
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)
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const (
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clientExporterLabel = "EXPORTER-QUIC client 1-RTT Secret"
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serverExporterLabel = "EXPORTER-QUIC server 1-RTT Secret"
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)
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// A TLSExporter gets the negotiated ciphersuite and computes exporter
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type TLSExporter interface {
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GetCipherSuite() mint.CipherSuiteParams
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ComputeExporter(label string, context []byte, keyLength int) ([]byte, error)
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}
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// DeriveAESKeys derives the AES keys and creates a matching AES-GCM AEAD instance
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func DeriveAESKeys(tls TLSExporter, pers protocol.Perspective) (AEAD, error) {
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var myLabel, otherLabel string
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if pers == protocol.PerspectiveClient {
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myLabel = clientExporterLabel
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otherLabel = serverExporterLabel
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} else {
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myLabel = serverExporterLabel
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otherLabel = clientExporterLabel
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}
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myKey, myIV, err := computeKeyAndIV(tls, myLabel)
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if err != nil {
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return nil, err
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}
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otherKey, otherIV, err := computeKeyAndIV(tls, otherLabel)
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if err != nil {
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return nil, err
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}
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return NewAEADAESGCM(otherKey, myKey, otherIV, myIV)
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}
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func computeKeyAndIV(tls TLSExporter, label string) (key, iv []byte, err error) {
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cs := tls.GetCipherSuite()
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secret, err := tls.ComputeExporter(label, nil, cs.Hash.Size())
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if err != nil {
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return nil, nil, err
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}
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key = mint.HkdfExpandLabel(cs.Hash, secret, "key", nil, cs.KeyLen)
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iv = mint.HkdfExpandLabel(cs.Hash, secret, "iv", nil, cs.IvLen)
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return key, iv, nil
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}
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