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77 lines
2.0 KiB
Go
77 lines
2.0 KiB
Go
package webpush
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import (
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"crypto/ecdh"
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"crypto/ecdsa"
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"crypto/elliptic"
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"encoding/base64"
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"fmt"
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"math/big"
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)
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// ecdhPublicKeyToECDSA converts an ECDH key to an ECDSA key.
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// This is deprecated as per https://github.com/golang/go/issues/63963
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// but we need to do it in order to parse the legacy private key format.
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func ecdhPublicKeyToECDSA(key *ecdh.PublicKey) (*ecdsa.PublicKey, error) {
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rawKey := key.Bytes()
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switch key.Curve() {
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case ecdh.P256():
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return &ecdsa.PublicKey{
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Curve: elliptic.P256(),
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X: big.NewInt(0).SetBytes(rawKey[1:33]),
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Y: big.NewInt(0).SetBytes(rawKey[33:]),
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}, nil
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case ecdh.P384():
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return &ecdsa.PublicKey{
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Curve: elliptic.P384(),
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X: big.NewInt(0).SetBytes(rawKey[1:49]),
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Y: big.NewInt(0).SetBytes(rawKey[49:]),
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}, nil
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case ecdh.P521():
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return &ecdsa.PublicKey{
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Curve: elliptic.P521(),
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X: big.NewInt(0).SetBytes(rawKey[1:67]),
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Y: big.NewInt(0).SetBytes(rawKey[67:]),
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}, nil
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default:
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return nil, fmt.Errorf("cannot convert non-NIST *ecdh.PublicKey to *ecdsa.PublicKey")
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}
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}
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func ecdhPrivateKeyToECDSA(key *ecdh.PrivateKey) (*ecdsa.PrivateKey, error) {
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// see https://github.com/golang/go/issues/63963
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pubKey, err := ecdhPublicKeyToECDSA(key.PublicKey())
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if err != nil {
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return nil, fmt.Errorf("converting PublicKey part of *ecdh.PrivateKey: %w", err)
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}
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return &ecdsa.PrivateKey{
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PublicKey: *pubKey,
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D: big.NewInt(0).SetBytes(key.Bytes()),
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}, nil
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}
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// DecodeLegacyVAPIDPrivateKey decodes the legacy string private key format
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// returned by GenerateVAPIDKeys in v1.
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func DecodeLegacyVAPIDPrivateKey(key string) (*VAPIDKeys, error) {
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bytes, err := decodeSubscriptionKey(key)
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if err != nil {
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return nil, err
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}
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ecdhPrivKey, err := ecdh.P256().NewPrivateKey(bytes)
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if err != nil {
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return nil, err
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}
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ecdsaPrivKey, err := ecdhPrivateKeyToECDSA(ecdhPrivKey)
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if err != nil {
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return nil, err
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}
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publicKey := base64.RawURLEncoding.EncodeToString(ecdhPrivKey.PublicKey().Bytes())
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return &VAPIDKeys{
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privateKey: ecdsaPrivKey,
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publicKey: publicKey,
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}, nil
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}
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