fix(chisel): convert seed to private key file EE-5099 (#9149)

api/chisel/crypto/crypto.go

@@ -0,0 +1,61 @@
+package crypto
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"io"
+	"math/big"
+
+	chshare "github.com/jpillora/chisel/share"
+)
+
+var one = new(big.Int).SetInt64(1)
+
+// GenerateGo119CompatibleKey This function is basically copied from chshare.GenerateKey.
+func GenerateGo119CompatibleKey(seed string) ([]byte, error) {
+	r := chshare.NewDetermRand([]byte(seed))
+	priv, err := ecdsaGenerateKey(elliptic.P256(), r)
+	if err != nil {
+		return nil, err
+	}
+	b, err := x509.MarshalECPrivateKey(priv)
+	if err != nil {
+		return nil, fmt.Errorf("Unable to marshal ECDSA private key: %w", err)
+	}
+	return pem.EncodeToMemory(&pem.Block{Type: "EC PRIVATE KEY", Bytes: b}), nil
+}
+
+// This function is copied from Go1.19
+func randFieldElement(c elliptic.Curve, rand io.Reader) (k *big.Int, err error) {
+	params := c.Params()
+	// Note that for P-521 this will actually be 63 bits more than the order, as
+	// division rounds down, but the extra bit is inconsequential.
+	b := make([]byte, params.N.BitLen()/8+8)
+	_, err = io.ReadFull(rand, b)
+	if err != nil {
+		return
+	}
+
+	k = new(big.Int).SetBytes(b)
+	n := new(big.Int).Sub(params.N, one)
+	k.Mod(k, n)
+	k.Add(k, one)
+	return
+}
+
+// This function is copied from Go1.19
+func ecdsaGenerateKey(c elliptic.Curve, rand io.Reader) (*ecdsa.PrivateKey, error) {
+	k, err := randFieldElement(c, rand)
+	if err != nil {
+		return nil, err
+	}
+
+	priv := new(ecdsa.PrivateKey)
+	priv.PublicKey.Curve = c
+	priv.D = k
+	priv.PublicKey.X, priv.PublicKey.Y = c.ScalarBaseMult(k.Bytes())
+	return priv, nil
+}