79 lines
2.0 KiB
Go
79 lines
2.0 KiB
Go
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package pnyx
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import (
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"crypto/ed25519"
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"crypto/rand"
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"crypto/sha512"
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"fmt"
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"filippo.io/edwards25519"
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)
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func NewSessionOpen(key ed25519.PrivateKey) ([]byte, ed25519.PrivateKey, error) {
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if key == nil {
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return nil, nil, fmt.Errorf("Cannot create a SESSION_OPEN packet without a key")
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}
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public, private, err := ed25519.GenerateKey(rand.Reader)
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if err != nil {
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return nil, nil, fmt.Errorf("Failed to generate ecdh key: %w", err)
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}
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packet := make([]byte, SESSION_OPEN_LENGTH)
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cur := 0
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copy(packet[cur:], []byte(key.Public().(ed25519.PublicKey)))
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cur += PUBKEY_LENGTH
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copy(packet[cur:], []byte(public))
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cur += PUBKEY_LENGTH
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signature := ed25519.Sign(key, packet[:cur])
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copy(packet[cur:], signature)
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cur += SIGNATURE_LENGTH
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return packet, private, nil
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}
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func ParseSessionOpen(session_open []byte) (ed25519.PublicKey, ed25519.PublicKey, error) {
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if len(session_open) != SESSION_OPEN_LENGTH {
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return nil, nil, fmt.Errorf("Bad SESSION_OPEN length: %d/%d", len(session_open), SESSION_OPEN_LENGTH)
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}
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cur := 0
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client_pubkey := (ed25519.PublicKey)(session_open[cur:cur+PUBKEY_LENGTH])
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cur += PUBKEY_LENGTH
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client_ecdh := (ed25519.PublicKey)(session_open[cur:cur+PUBKEY_LENGTH])
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cur += PUBKEY_LENGTH
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digest := session_open[:cur]
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signature := session_open[cur:cur+SIGNATURE_LENGTH]
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cur += SIGNATURE_LENGTH
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if ed25519.Verify(client_pubkey, digest, signature) == false {
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return nil, nil, fmt.Errorf("SESSION_OPEN signature verification failed")
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}
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return client_pubkey, client_ecdh, nil
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}
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func ECDH(public ed25519.PublicKey, private ed25519.PrivateKey) ([]byte, error) {
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public_point, err := (&edwards25519.Point{}).SetBytes(public)
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if err != nil {
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return nil, err
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}
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h := sha512.Sum512(private.Seed())
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private_scalar, err := (&edwards25519.Scalar{}).SetBytesWithClamping(h[:32])
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if err != nil {
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return nil, err
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}
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shared_point := public_point.ScalarMult(private_scalar, public_point)
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return shared_point.BytesMontgomery(), nil
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}
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