accounts/scwallet: use go-ethereum crypto instead of go-ecdh (#22212)

* accounts/scwallet: use go-ethereum crypto instead of go-ecdh

github.com/wsddn/go-ecdh is a wrapper package for ECDH functionality
with any elliptic curve.

Since 'generic' ECDH is not required in accounts/scwallet (the curve is
always secp256k1), we can just use the standard library functionality
and our own crypto libraries to perform ECDH and save a dependency.

* Update accounts/scwallet/securechannel.go

Co-authored-by: Guillaume Ballet <gballet@gmail.com>

* Use the correct key

Co-authored-by: Guillaume Ballet <gballet@gmail.com>

accounts/scwallet/securechannel.go

@@ -20,14 +20,14 @@ import (
 	"bytes"
 	"crypto/aes"
 	"crypto/cipher"
+	"crypto/elliptic"
 	"crypto/rand"
 	"crypto/sha256"
 	"crypto/sha512"
 	"fmt"
 
 	"github.com/ethereum/go-ethereum/crypto"
 	pcsc "github.com/gballet/go-libpcsclite"
-	"github.com/wsddn/go-ecdh"
 	"golang.org/x/crypto/pbkdf2"
 	"golang.org/x/text/unicode/norm"
 )
@@ -63,26 +63,19 @@ type SecureChannelSession struct {
 // NewSecureChannelSession creates a new secure channel for the given card and public key.
 func NewSecureChannelSession(card *pcsc.Card, keyData []byte) (*SecureChannelSession, error) {
 	// Generate an ECDSA keypair for ourselves
-	gen := ecdh.NewEllipticECDH(crypto.S256())
-	private, public, err := gen.GenerateKey(rand.Reader)
+	key, err := crypto.GenerateKey()
 	if err != nil {
 		return nil, err
 	}
-
-	cardPublic, ok := gen.Unmarshal(keyData)
-	if !ok {
-		return nil, fmt.Errorf("could not unmarshal public key from card")
-	}
-
-	secret, err := gen.GenerateSharedSecret(private, cardPublic)
+	cardPublic, err := crypto.UnmarshalPubkey(keyData)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("could not unmarshal public key from card: %v", err)
 	}
-
+	secret, _ := key.Curve.ScalarMult(cardPublic.X, cardPublic.Y, key.D.Bytes())
 	return &SecureChannelSession{
 		card:      card,
-		secret:    secret,
-		publicKey: gen.Marshal(public),
+		secret:    secret.Bytes(),
+		publicKey: elliptic.Marshal(crypto.S256(), key.PublicKey.X, key.PublicKey.Y),
 	}, nil
 }
 

go.mod

@@ -54,7 +54,6 @@ require (
 	github.com/stretchr/testify v1.7.0
 	github.com/syndtr/goleveldb v1.0.1-0.20200815110645-5c35d600f0ca
 	github.com/tyler-smith/go-bip39 v1.0.1-0.20181017060643-dbb3b84ba2ef
-	github.com/wsddn/go-ecdh v0.0.0-20161211032359-48726bab9208
 	golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9
 	golang.org/x/net v0.0.0-20200822124328-c89045814202 // indirect
 	golang.org/x/sys v0.0.0-20200824131525-c12d262b63d8

go.sum

@@ -365,8 +365,6 @@ github.com/tyler-smith/go-bip39 v1.0.1-0.20181017060643-dbb3b84ba2ef h1:wHSqTBrZ
 github.com/tyler-smith/go-bip39 v1.0.1-0.20181017060643-dbb3b84ba2ef/go.mod h1:sJ5fKU0s6JVwZjjcUEX2zFOnvq0ASQ2K9Zr6cf67kNs=
 github.com/urfave/cli v1.22.1/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60NtXRu0=
 github.com/willf/bitset v1.1.3/go.mod h1:RjeCKbqT1RxIR/KWY6phxZiaY1IyutSBfGjNPySAYV4=
-github.com/wsddn/go-ecdh v0.0.0-20161211032359-48726bab9208 h1:1cngl9mPEoITZG8s8cVcUy5CeIBYhEESkOB7m6Gmkrk=
-github.com/wsddn/go-ecdh v0.0.0-20161211032359-48726bab9208/go.mod h1:IotVbo4F+mw0EzQ08zFqg7pK3FebNXpaMsRy2RT+Ees=
 github.com/xlab/treeprint v0.0.0-20180616005107-d6fb6747feb6/go.mod h1:ce1O1j6UtZfjr22oyGxGLbauSBp2YVXpARAosm7dHBg=
 go.opencensus.io v0.21.0/go.mod h1:mSImk1erAIZhrmZN+AvHh14ztQfjbGwt4TtuofqLduU=
 go.opencensus.io v0.22.0/go.mod h1:+kGneAE2xo2IficOXnaByMWTGM9T73dGwxeWcUqIpI8=