feat: Support metamask mobile login (#2844)

idp/metamask.go

@@ -15,15 +15,43 @@
 package idp
 
 import (
+	"encoding/hex"
 	"encoding/json"
 	"errors"
 	"fmt"
 	"net/http"
+	"strings"
 	"time"
 
+	"github.com/ethereum/go-ethereum/crypto"
+
 	"golang.org/x/oauth2"
 )
 
+type EIP712Message struct {
+	Domain struct {
+		ChainId string `json:"chainId"`
+		Name    string `json:"name"`
+		Version string `json:"version"`
+	} `json:"domain"`
+	Message struct {
+		Prompt   string `json:"prompt"`
+		Nonce    string `json:"nonce"`
+		CreateAt string `json:"createAt"`
+	} `json:"message"`
+	PrimaryType string `json:"primaryType"`
+	Types       struct {
+		EIP712Domain []struct {
+			Name string `json:"name"`
+			Type string `json:"type"`
+		} `json:"EIP712Domain"`
+		AuthRequest []struct {
+			Name string `json:"name"`
+			Type string `json:"type"`
+		} `json:"AuthRequest"`
+	} `json:"types"`
+}
+
 type MetaMaskIdProvider struct {
 	Client *http.Client
 }
@@ -42,6 +70,15 @@ func (idp *MetaMaskIdProvider) GetToken(code string) (*oauth2.Token, error) {
 	if err := json.Unmarshal([]byte(code), &web3AuthToken); err != nil {
 		return nil, err
 	}
+	valid, err := VerifySignature(web3AuthToken.Address, web3AuthToken.TypedData, web3AuthToken.Signature)
+	if err != nil {
+		return nil, err
+	}
+
+	if !valid {
+		return nil, fmt.Errorf("invalid signature")
+	}
+
 	token := &oauth2.Token{
 		AccessToken: web3AuthToken.Signature,
 		TokenType:   "Bearer",
@@ -68,3 +105,43 @@ func (idp *MetaMaskIdProvider) GetUserInfo(token *oauth2.Token) (*UserInfo, erro
 	}
 	return userInfo, nil
 }
+
+func VerifySignature(userAddress string, originalMessage string, signatureHex string) (bool, error) {
+	var eip712Mes EIP712Message
+	err := json.Unmarshal([]byte(originalMessage), &eip712Mes)
+	if err != nil {
+		return false, fmt.Errorf("invalid signature (Error parsing JSON)")
+	}
+
+	createAtTime, err := time.Parse("2006/1/2 15:04:05", eip712Mes.Message.CreateAt)
+	currentTime := time.Now()
+	if createAtTime.Before(currentTime.Add(-1*time.Minute)) && createAtTime.After(currentTime) {
+		return false, fmt.Errorf("invalid signature (signature does not meet time requirements)")
+	}
+
+	if !strings.HasPrefix(signatureHex, "0x") {
+		signatureHex = "0x" + signatureHex
+	}
+
+	signatureBytes, err := hex.DecodeString(signatureHex[2:])
+	if err != nil {
+		return false, err
+	}
+
+	if signatureBytes[64] != 27 && signatureBytes[64] != 28 {
+		return false, fmt.Errorf("invalid signature (incorrect recovery id)")
+	}
+	signatureBytes[64] -= 27
+
+	msg := fmt.Sprintf("\x19Ethereum Signed Message:\n%d%s", len([]byte(originalMessage)), []byte(originalMessage))
+	hash := crypto.Keccak256Hash([]byte(msg))
+
+	pubKey, err := crypto.SigToPub(hash.Bytes(), signatureBytes)
+	if err != nil {
+		return false, err
+	}
+
+	recoveredAddr := crypto.PubkeyToAddress(*pubKey)
+
+	return strings.EqualFold(recoveredAddr.Hex(), userAddress), nil
+}