internal/crypto: use crypto/ecdh in go1.20

internal/crypto/crypto.go

@@ -1,9 +1,6 @@
 package crypto
 
 import (
-	"crypto/elliptic"
-	"crypto/md5"
-	"crypto/rand"
 	"encoding/hex"
 	"encoding/json"
 	"net/http"
@@ -26,21 +23,11 @@ func NewECDH() *ECDH {
 	e := &ECDH{
 		SvrPublicKeyVer: 1,
 	}
-	e.generateKey(serverPublicKey)
+	key, _ := hex.DecodeString(serverPublicKey)
+	e.init(key)
 	return e
 }
 
-func (e *ECDH) generateKey(sPubKey string) {
-	pub, _ := hex.DecodeString(sPubKey)
-	p256 := elliptic.P256()
-	key, sx, sy, _ := elliptic.GenerateKey(p256, rand.Reader)
-	tx, ty := elliptic.Unmarshal(p256, pub)
-	x, _ := p256.ScalarMult(tx, ty, key)
-	hash := md5.Sum(x.Bytes()[:16])
-	e.ShareKey = hash[:]
-	e.PublicKey = elliptic.Marshal(p256, sx, sy)
-}
-
 type pubKeyResp struct {
 	Meta struct {
 		PubKeyVer uint16 `json:"KeyVer"`
@@ -61,5 +48,6 @@ func (e *ECDH) FetchPubKey(uin int64) {
 		return
 	}
 	e.SvrPublicKeyVer = pubKey.Meta.PubKeyVer
-	e.generateKey(pubKey.Meta.PubKey) // todo check key sign
+	key, _ := hex.DecodeString(pubKey.Meta.PubKey)
+	e.init(key) // todo check key sign
 }

internal/crypto/ecdh_119.go

@@ -0,0 +1,19 @@
+//go:build !go1.20
+
+package crypto
+
+import (
+	"crypto/elliptic"
+	"crypto/md5"
+	"crypto/rand"
+)
+
+func (e *ECDH) init(svrPubKey []byte) {
+	p256 := elliptic.P256()
+	key, sx, sy, _ := elliptic.GenerateKey(p256, rand.Reader)
+	tx, ty := elliptic.Unmarshal(p256, svrPubKey)
+	x, _ := p256.ScalarMult(tx, ty, key)
+	hash := md5.Sum(x.Bytes()[:16])
+	e.ShareKey = hash[:]
+	e.PublicKey = elliptic.Marshal(p256, sx, sy)
+}

internal/crypto/ecdh_120.go

@@ -0,0 +1,21 @@
+//go:build go1.20
+
+package crypto
+
+import (
+	"crypto/ecdh"
+	"crypto/md5"
+	"crypto/rand"
+)
+
+func (e *ECDH) init(svrPubKey []byte) {
+	p256 := ecdh.P256()
+	local, _ := p256.GenerateKey(rand.Reader)
+	remote, _ := p256.NewPublicKey(svrPubKey)
+	share, _ := p256.ECDH(local, remote)
+
+	hash := md5.New()
+	hash.Write(share[:16])
+	e.ShareKey = hash.Sum(nil)
+	e.PublicKey = local.PublicKey().Bytes()
+}