move signSessionAuthProof to sessions_auth_proof.go

rpc/sessions_auth_proof.go

@@ -4,11 +4,14 @@ import (
 	"context"
 	"fmt"
 
+	"github.com/0xsequence/ethkit/ethwallet"
 	"github.com/0xsequence/ethkit/go-ethereum/common"
+	"github.com/0xsequence/go-sequence"
 	"github.com/0xsequence/go-sequence/intents"
 	"github.com/0xsequence/waas-authenticator/data"
 	"github.com/0xsequence/waas-authenticator/proto"
 	proto_wallet "github.com/0xsequence/waas-authenticator/proto/waas"
+	"github.com/0xsequence/waas-authenticator/rpc/tenant"
 )
 
 func (s *RPC) sessionAuthProof(
@@ -39,3 +42,46 @@ func (s *RPC) sessionAuthProof(
 
 	return convertIntentResponse(res), nil
 }
+
+func (s *RPC) signSessionAuthProof(
+	ctx context.Context,
+	proof *proto_wallet.SessionAuthProof,
+) error {
+	tntData := tenant.FromContext(ctx)
+
+	parentWallet, err := ethwallet.NewWalletFromPrivateKey(tntData.PrivateKey)
+	if err != nil {
+		return fmt.Errorf("recovering parent wallet: %w", err)
+	}
+
+	// Make sure the message is EIP191 encoded
+	msgBytes := sequence.MessageToEIP191(common.FromHex(proof.Message.Message))
+
+	// Validate that message match intent
+	digest := sequence.MessageDigest(msgBytes)
+
+	chainID, ok := sequence.ParseHexOrDec(proof.Message.ChainID)
+	if !ok {
+		return fmt.Errorf("invalid chain id: %s", proof.Message.ChainID)
+	}
+
+	subdigest, err := sequence.SubDigest(chainID, common.HexToAddress(proof.Wallet), digest)
+	if err != nil {
+		return fmt.Errorf("calculating digest: %w", err)
+	}
+
+	// Our EOA belongs to the *parent* wallet, so we need to sign the subdigest with the parent key
+	sig, parentSubdigest, err := s.signUsingParent(parentWallet, tntData.ParentAddress, subdigest, chainID)
+	if err != nil {
+		return fmt.Errorf("signing subdigest using parent wallet: %w", err)
+	}
+
+	proof.Signatures = []*proto_wallet.ProvidedSignature{
+		{
+			Digest:    "0x" + common.Bytes2Hex(parentSubdigest),
+			Signature: "0x" + common.Bytes2Hex(sig),
+			Address:   parentWallet.Address().String(),
+		},
+	}
+	return nil
+}