Add SignTypedData to native Keystore interface (ethereum#1220)

* Add SignTypedData to native Keystore interface

* Add simple smoke test for the signTypedData method in the native interface

mobile/accounts.go

@@ -20,13 +20,16 @@
 package geth
 
 import (
+	"encoding/json"
 	"errors"
+	"fmt"
 	"time"
 
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/signer/core"
 )
 
 const (
@@ -120,6 +123,31 @@ func (ks *KeyStore) SignHash(address *Address, hash []byte) (signature []byte, _
 	return ks.keystore.SignHash(accounts.Account{Address: address.address}, common.CopyBytes(hash))
 }
 
+// SignTypedData signs EIP-712 conformant typed data
+// hash = keccak256("\x19${byteVersion}${domainSeparator}${hashStruct(message)}")
+func (ks *KeyStore) SignTypedData(account *Account, typedDataJSON []byte) ([]byte, error) {
+	var typedData core.TypedData
+	err := json.Unmarshal(typedDataJSON, &typedData)
+	if err != nil {
+		return nil, err
+	}
+	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)
+	signature, err := ks.keystore.SignHash(account.account, sighash)
+	if err != nil {
+		return nil, err
+	}
+	return signature, nil
+}
+
 // SignTx signs the given transaction with the requested account.
 func (ks *KeyStore) SignTx(account *Account, tx *Transaction, chainID *BigInt) (*Transaction, error) {
 	if chainID == nil { // Null passed from mobile app

mobile/accounts_test.go

@@ -0,0 +1,123 @@
+package geth
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/accounts/keystore"
+)
+
+const jsonTypedData = `
+    {
+      "types": {
+        "EIP712Domain": [
+          {
+            "name": "name",
+            "type": "string"
+          },
+          {
+            "name": "version",
+            "type": "string"
+          },
+          {
+            "name": "chainId",
+            "type": "uint256"
+          },
+          {
+            "name": "verifyingContract",
+            "type": "address"
+          }
+        ],
+        "Person": [
+          {
+            "name": "name",
+            "type": "string"
+          },
+          {
+            "name": "test",
+            "type": "uint8"
+          },
+          {
+            "name": "wallet",
+            "type": "address"
+          }
+        ],
+        "Mail": [
+          {
+            "name": "from",
+            "type": "Person"
+          },
+          {
+            "name": "to",
+            "type": "Person"
+          },
+          {
+            "name": "contents",
+            "type": "string"
+          }
+        ]
+      },
+      "primaryType": "Mail",
+      "domain": {
+        "name": "Ether Mail",
+        "version": "1",
+        "chainId": "1",
+        "verifyingContract": "0xCCCcccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
+      },
+      "message": {
+        "from": {
+          "name": "Cow",
+		  "test": 3,
+          "wallet": "0xcD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
+        },
+        "to": {
+		  "name": "Bob",
+		  "test": 4,
+          "wallet": "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB"
+        },
+        "contents": "Hello, Bob!"
+      }
+    }
+`
+
+const scryptN = 2
+const scryptP = 1
+
+// copied from the keystore_test.go file in the keystore package
+func tmpKeyStore(t *testing.T, encrypted bool) (string, *keystore.KeyStore) {
+	d, err := ioutil.TempDir("", "eth-keystore-test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	newKs := keystore.NewPlaintextKeyStore
+	if encrypted {
+		newKs = func(kd string) *keystore.KeyStore {
+			return keystore.NewKeyStore(kd, scryptN, scryptP)
+		}
+	}
+	return d, newKs(d)
+}
+
+func TestSignTypedData(t *testing.T) {
+	dir, ks := tmpKeyStore(t, true)
+	defer os.RemoveAll(dir)
+
+	pass := "" // not used but required by API
+	a1, err := ks.NewAccount(pass)
+	if err != nil {
+		t.Fatal(err)
+	}
+	nks := &KeyStore{keystore: ks}
+	nAcc := &Account{account: a1}
+	if err := nks.Unlock(nAcc, ""); err != nil {
+		t.Fatal(err)
+	}
+	signature, err := nks.SignTypedData(nAcc, []byte(jsonTypedData))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if signature == nil || len(signature) != 65 {
+		t.Errorf("Expected 65 byte signature (got %d bytes)", len(signature))
+	}
+}