chore: make deps, go mod vendor

vendor/github.com/ProtonMail/go-crypto/openpgp/x25519/x25519.go

@@ -0,0 +1,221 @@
+package x25519
+
+import (
+	"crypto/sha256"
+	"crypto/subtle"
+	"io"
+
+	"github.com/ProtonMail/go-crypto/openpgp/aes/keywrap"
+	"github.com/ProtonMail/go-crypto/openpgp/errors"
+	x25519lib "github.com/cloudflare/circl/dh/x25519"
+	"golang.org/x/crypto/hkdf"
+)
+
+const (
+	hkdfInfo      = "OpenPGP X25519"
+	aes128KeySize = 16
+	// The size of a public or private key in bytes.
+	KeySize = x25519lib.Size
+)
+
+type PublicKey struct {
+	// Point represents the encoded elliptic curve point of the public key.
+	Point []byte
+}
+
+type PrivateKey struct {
+	PublicKey
+	// Secret represents the secret of the private key.
+	Secret []byte
+}
+
+// NewPrivateKey creates a new empty private key including the public key.
+func NewPrivateKey(key PublicKey) *PrivateKey {
+	return &PrivateKey{
+		PublicKey: key,
+	}
+}
+
+// Validate validates that the provided public key matches the private key.
+func Validate(pk *PrivateKey) (err error) {
+	var expectedPublicKey, privateKey x25519lib.Key
+	subtle.ConstantTimeCopy(1, privateKey[:], pk.Secret)
+	x25519lib.KeyGen(&expectedPublicKey, &privateKey)
+	if subtle.ConstantTimeCompare(expectedPublicKey[:], pk.PublicKey.Point) == 0 {
+		return errors.KeyInvalidError("x25519: invalid key")
+	}
+	return nil
+}
+
+// GenerateKey generates a new x25519 key pair.
+func GenerateKey(rand io.Reader) (*PrivateKey, error) {
+	var privateKey, publicKey x25519lib.Key
+	privateKeyOut := new(PrivateKey)
+	err := generateKey(rand, &privateKey, &publicKey)
+	if err != nil {
+		return nil, err
+	}
+	privateKeyOut.PublicKey.Point = publicKey[:]
+	privateKeyOut.Secret = privateKey[:]
+	return privateKeyOut, nil
+}
+
+func generateKey(rand io.Reader, privateKey *x25519lib.Key, publicKey *x25519lib.Key) error {
+	maxRounds := 10
+	isZero := true
+	for round := 0; isZero; round++ {
+		if round == maxRounds {
+			return errors.InvalidArgumentError("x25519: zero keys only, randomness source might be corrupt")
+		}
+		_, err := io.ReadFull(rand, privateKey[:])
+		if err != nil {
+			return err
+		}
+		isZero = constantTimeIsZero(privateKey[:])
+	}
+	x25519lib.KeyGen(publicKey, privateKey)
+	return nil
+}
+
+// Encrypt encrypts a sessionKey with x25519 according to
+// the OpenPGP crypto refresh specification section 5.1.6. The function assumes that the
+// sessionKey has the correct format and padding according to the specification.
+func Encrypt(rand io.Reader, publicKey *PublicKey, sessionKey []byte) (ephemeralPublicKey *PublicKey, encryptedSessionKey []byte, err error) {
+	var ephemeralPrivate, ephemeralPublic, staticPublic, shared x25519lib.Key
+	// Check that the input static public key has 32 bytes
+	if len(publicKey.Point) != KeySize {
+		err = errors.KeyInvalidError("x25519: the public key has the wrong size")
+		return
+	}
+	copy(staticPublic[:], publicKey.Point)
+	// Generate ephemeral keyPair
+	err = generateKey(rand, &ephemeralPrivate, &ephemeralPublic)
+	if err != nil {
+		return
+	}
+	// Compute shared key
+	ok := x25519lib.Shared(&shared, &ephemeralPrivate, &staticPublic)
+	if !ok {
+		err = errors.KeyInvalidError("x25519: the public key is a low order point")
+		return
+	}
+	// Derive the encryption key from the shared secret
+	encryptionKey := applyHKDF(ephemeralPublic[:], publicKey.Point[:], shared[:])
+	ephemeralPublicKey = &PublicKey{
+		Point: ephemeralPublic[:],
+	}
+	// Encrypt the sessionKey with aes key wrapping
+	encryptedSessionKey, err = keywrap.Wrap(encryptionKey, sessionKey)
+	return
+}
+
+// Decrypt decrypts a session key stored in ciphertext with the provided x25519
+// private key and ephemeral public key.
+func Decrypt(privateKey *PrivateKey, ephemeralPublicKey *PublicKey, ciphertext []byte) (encodedSessionKey []byte, err error) {
+	var ephemeralPublic, staticPrivate, shared x25519lib.Key
+	// Check that the input ephemeral public key has 32 bytes
+	if len(ephemeralPublicKey.Point) != KeySize {
+		err = errors.KeyInvalidError("x25519: the public key has the wrong size")
+		return
+	}
+	copy(ephemeralPublic[:], ephemeralPublicKey.Point)
+	subtle.ConstantTimeCopy(1, staticPrivate[:], privateKey.Secret)
+	// Compute shared key
+	ok := x25519lib.Shared(&shared, &staticPrivate, &ephemeralPublic)
+	if !ok {
+		err = errors.KeyInvalidError("x25519: the ephemeral public key is a low order point")
+		return
+	}
+	// Derive the encryption key from the shared secret
+	encryptionKey := applyHKDF(ephemeralPublicKey.Point[:], privateKey.PublicKey.Point[:], shared[:])
+	// Decrypt the session key with aes key wrapping
+	encodedSessionKey, err = keywrap.Unwrap(encryptionKey, ciphertext)
+	return
+}
+
+func applyHKDF(ephemeralPublicKey []byte, publicKey []byte, sharedSecret []byte) []byte {
+	inputKey := make([]byte, 3*KeySize)
+	// ephemeral public key | recipient public key | shared secret
+	subtle.ConstantTimeCopy(1, inputKey[:KeySize], ephemeralPublicKey)
+	subtle.ConstantTimeCopy(1, inputKey[KeySize:2*KeySize], publicKey)
+	subtle.ConstantTimeCopy(1, inputKey[2*KeySize:], sharedSecret)
+	hkdfReader := hkdf.New(sha256.New, inputKey, []byte{}, []byte(hkdfInfo))
+	encryptionKey := make([]byte, aes128KeySize)
+	_, _ = io.ReadFull(hkdfReader, encryptionKey)
+	return encryptionKey
+}
+
+func constantTimeIsZero(bytes []byte) bool {
+	isZero := byte(0)
+	for _, b := range bytes {
+		isZero |= b
+	}
+	return isZero == 0
+}
+
+// ENCODING/DECODING ciphertexts:
+
+// EncodeFieldsLength returns the length of the ciphertext encoding
+// given the encrypted session key.
+func EncodedFieldsLength(encryptedSessionKey []byte, v6 bool) int {
+	lenCipherFunction := 0
+	if !v6 {
+		lenCipherFunction = 1
+	}
+	return KeySize + 1 + len(encryptedSessionKey) + lenCipherFunction
+}
+
+// EncodeField encodes x25519 session key encryption fields as
+// ephemeral x25519 public key | follow byte length | cipherFunction (v3 only) | encryptedSessionKey
+// and writes it to writer.
+func EncodeFields(writer io.Writer, ephemeralPublicKey *PublicKey, encryptedSessionKey []byte, cipherFunction byte, v6 bool) (err error) {
+	lenAlgorithm := 0
+	if !v6 {
+		lenAlgorithm = 1
+	}
+	if _, err = writer.Write(ephemeralPublicKey.Point); err != nil {
+		return err
+	}
+	if _, err = writer.Write([]byte{byte(len(encryptedSessionKey) + lenAlgorithm)}); err != nil {
+		return err
+	}
+	if !v6 {
+		if _, err = writer.Write([]byte{cipherFunction}); err != nil {
+			return err
+		}
+	}
+	_, err = writer.Write(encryptedSessionKey)
+	return err
+}
+
+// DecodeField decodes a x25519 session key encryption as
+// ephemeral x25519 public key | follow byte length | cipherFunction (v3 only) | encryptedSessionKey.
+func DecodeFields(reader io.Reader, v6 bool) (ephemeralPublicKey *PublicKey, encryptedSessionKey []byte, cipherFunction byte, err error) {
+	var buf [1]byte
+	ephemeralPublicKey = &PublicKey{
+		Point: make([]byte, KeySize),
+	}
+	// 32 octets representing an ephemeral x25519 public key.
+	if _, err = io.ReadFull(reader, ephemeralPublicKey.Point); err != nil {
+		return nil, nil, 0, err
+	}
+	// A one-octet size of the following fields.
+	if _, err = io.ReadFull(reader, buf[:]); err != nil {
+		return nil, nil, 0, err
+	}
+	followingLen := buf[0]
+	// The one-octet algorithm identifier, if it was passed (in the case of a v3 PKESK packet).
+	if !v6 {
+		if _, err = io.ReadFull(reader, buf[:]); err != nil {
+			return nil, nil, 0, err
+		}
+		cipherFunction = buf[0]
+		followingLen -= 1
+	}
+	// The encrypted session key.
+	encryptedSessionKey = make([]byte, followingLen)
+	if _, err = io.ReadFull(reader, encryptedSessionKey); err != nil {
+		return nil, nil, 0, err
+	}
+	return ephemeralPublicKey, encryptedSessionKey, cipherFunction, nil
+}