From e41c713ffba8fe5e6c7c3a5c761b942f2087985e Mon Sep 17 00:00:00 2001
From: crypto-facs <84574577+crypto-facs@users.noreply.github.com>
Date: Fri, 25 Feb 2022 08:42:33 -0500
Subject: [PATCH] rpc: add support for `eth_signedTypedData` (#953)
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* add signTypedData api

* fix typo

* fix lint issues

* add crypto recovery offset

* Apply suggestions from code review

* add changelog

Co-authored-by: Federico Kunze Küllmer <31522760+fedekunze@users.noreply.github.com>
---
 CHANGELOG.md                       |  5 +++-
 rpc/ethereum/namespaces/eth/api.go | 38 +++++++++++++++++++++++++++++-
 2 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index abeec1c2..9aea2047 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,4 @@
+
 <!--
 Guiding Principles:
 
@@ -39,7 +40,9 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Improvements
 
-- (log) [#948](https://github.com/tharsis/ethermint/pull/948) redirect go-ethereum's logs to cosmos-sdk logger.
+* (log) [#948](https://github.com/tharsis/ethermint/pull/948) redirect go-ethereum's logs to cosmos-sdk logger.
+* (rpc) [tharsis#953](https://github.com/tharsis/ethermint/pull/953) Add `eth_signTypedData` api support.
+
 
 ## [v0.10.0-beta1] - 2022-02-15
 
diff --git a/rpc/ethereum/namespaces/eth/api.go b/rpc/ethereum/namespaces/eth/api.go
index a9f70e86..0e5a3d03 100644
--- a/rpc/ethereum/namespaces/eth/api.go
+++ b/rpc/ethereum/namespaces/eth/api.go
@@ -7,6 +7,8 @@ import (
 	"math"
 	"math/big"
 
+	"github.com/ethereum/go-ethereum/signer/core/apitypes"
+
 	"github.com/ethereum/go-ethereum/core/vm"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rpc"
@@ -429,7 +431,41 @@ func (e *PublicAPI) Sign(address common.Address, data hexutil.Bytes) (hexutil.By
 		return nil, err
 	}
 
-	signature[64] += 27 // Transform V from 0/1 to 27/28 according to the yellow paper
+	signature[crypto.RecoveryIDOffset] += 27 // Transform V from 0/1 to 27/28 according to the yellow paper
+	return signature, nil
+}
+
+// SignTypedData signs EIP-712 conformant typed data
+func (e *PublicAPI) SignTypedData(address common.Address, typedData apitypes.TypedData) (hexutil.Bytes, error) {
+	e.logger.Debug("eth_signTypedData", "address", address.Hex(), "data", typedData)
+	from := sdk.AccAddress(address.Bytes())
+
+	_, err := e.clientCtx.Keyring.KeyByAddress(from)
+	if err != nil {
+		e.logger.Error("failed to find key in keyring", "address", address.String())
+		return nil, fmt.Errorf("%s; %s", keystore.ErrNoMatch, err.Error())
+	}
+
+	domainSeparator, err := typedData.HashStruct("EIP712Domain", typedData.Domain.Map())
+	if err != nil {
+		return nil, err
+	}
+
+	typedDataHash, err := typedData.HashStruct(typedData.PrimaryType, typedData.Message)
+	if err != nil {
+		return nil, err
+	}
+
+	rawData := []byte(fmt.Sprintf("\x19\x01%s%s", string(domainSeparator), string(typedDataHash)))
+	sigHash := crypto.Keccak256(rawData)
+	// Sign the requested hash with the wallet
+	signature, _, err := e.clientCtx.Keyring.SignByAddress(from, sigHash)
+	if err != nil {
+		e.logger.Error("keyring.SignByAddress failed", "address", address.Hex())
+		return nil, err
+	}
+
+	signature[crypto.RecoveryIDOffset] += 27 // Transform V from 0/1 to 27/28 according to the yellow paper
 	return signature, nil
 }