core/signer, clef: improve ui-test flow, fix errors in uint handling (#19584)

* core/signer, clef: improve ui-test flow, fix errors in uint handling for eip-712

* core/signer: add fuzzer testcases + crashfixes

* signer: address review concerns, check sign in integer parsing

27 files changed, 1326 insertions, 557 deletions

diff --git a/cmd/clef/main.go b/cmd/clef/main.go
index fecfcafaf..ad7ba186d 100644
--- a/cmd/clef/main.go
+++ b/cmd/clef/main.go
@@ -33,6 +33,7 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
+	"time"
 
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/accounts/keystore"
@@ -638,6 +639,10 @@ func testExternalUI(api *core.SignerAPI) {
 	errs := make([]string, 0)
 
 	a := common.HexToAddress("0xdeadbeef000000000000000000000000deadbeef")
+	addErr := func(errStr string) {
+		log.Info("Test error", "error", errStr)
+		errs = append(errs, errStr)
+	}
 
 	queryUser := func(q string) string {
 		resp, err := api.UI.OnInputRequired(core.UserInputRequest{
@@ -645,36 +650,39 @@ func testExternalUI(api *core.SignerAPI) {
 			Prompt: q,
 		})
 		if err != nil {
-			errs = append(errs, err.Error())
+			addErr(err.Error())
 		}
 		return resp.Text
 	}
 	expectResponse := func(testcase, question, expect string) {
 		if got := queryUser(question); got != expect {
-			errs = append(errs, fmt.Sprintf("%s: got %v, expected %v", testcase, got, expect))
+			addErr(fmt.Sprintf("%s: got %v, expected %v", testcase, got, expect))
 		}
 	}
 	expectApprove := func(testcase string, err error) {
 		if err == nil || err == accounts.ErrUnknownAccount {
 			return
 		}
-		errs = append(errs, fmt.Sprintf("%v: expected no error, got %v", testcase, err.Error()))
+		addErr(fmt.Sprintf("%v: expected no error, got %v", testcase, err.Error()))
 	}
 	expectDeny := func(testcase string, err error) {
 		if err == nil || err != core.ErrRequestDenied {
-			errs = append(errs, fmt.Sprintf("%v: expected ErrRequestDenied, got %v", testcase, err))
+			addErr(fmt.Sprintf("%v: expected ErrRequestDenied, got %v", testcase, err))
 		}
 	}
-
+	var delay = 1 * time.Second
 	// Test display of info and error
 	{
 		api.UI.ShowInfo("If you see this message, enter 'yes' to next question")
+		time.Sleep(delay)
 		expectResponse("showinfo", "Did you see the message? [yes/no]", "yes")
 		api.UI.ShowError("If you see this message, enter 'yes' to the next question")
+		time.Sleep(delay)
 		expectResponse("showerror", "Did you see the message? [yes/no]", "yes")
 	}
 	{ // Sign data test - clique header
 		api.UI.ShowInfo("Please approve the next request for signing a clique header")
+		time.Sleep(delay)
 		cliqueHeader := types.Header{
 			common.HexToHash("0000H45H"),
 			common.HexToHash("0000H45H"),
@@ -700,14 +708,27 @@ func testExternalUI(api *core.SignerAPI) {
 		_, err = api.SignData(ctx, accounts.MimetypeClique, *addr, hexutil.Encode(cliqueRlp))
 		expectApprove("signdata - clique header", err)
 	}
+	{ // Sign data test - typed data
+		api.UI.ShowInfo("Please approve the next request for signing EIP-712 typed data")
+		time.Sleep(delay)
+		addr, _ := common.NewMixedcaseAddressFromString("0x0011223344556677889900112233445566778899")
+		data := `{"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","wallet":"0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB","test":"2"},"contents":"Hello, Bob!"}}`
+		//_, err := api.SignData(ctx, accounts.MimetypeTypedData, *addr, hexutil.Encode([]byte(data)))
+		var typedData core.TypedData
+		err := json.Unmarshal([]byte(data), &typedData)
+		_, err = api.SignTypedData(ctx, *addr, typedData)
+		expectApprove("sign 712 typed data", err)
+	}
 	{ // Sign data test - plain text
 		api.UI.ShowInfo("Please approve the next request for signing text")
+		time.Sleep(delay)
 		addr, _ := common.NewMixedcaseAddressFromString("0x0011223344556677889900112233445566778899")
 		_, err := api.SignData(ctx, accounts.MimetypeTextPlain, *addr, hexutil.Encode([]byte("hello world")))
 		expectApprove("signdata - text", err)
 	}
 	{ // Sign data test - plain text reject
 		api.UI.ShowInfo("Please deny the next request for signing text")
+		time.Sleep(delay)
 		addr, _ := common.NewMixedcaseAddressFromString("0x0011223344556677889900112233445566778899")
 		_, err := api.SignData(ctx, accounts.MimetypeTextPlain, *addr, hexutil.Encode([]byte("hello world")))
 		expectDeny("signdata - text", err)
@@ -715,6 +736,7 @@ func testExternalUI(api *core.SignerAPI) {
 	{ // Sign transaction
 
 		api.UI.ShowInfo("Please reject next transaction")
+		time.Sleep(delay)
 		data := hexutil.Bytes([]byte{})
 		to := common.NewMixedcaseAddress(a)
 		tx := core.SendTxArgs{
@@ -733,16 +755,19 @@ func testExternalUI(api *core.SignerAPI) {
 	}
 	{ // Listing
 		api.UI.ShowInfo("Please reject listing-request")
+		time.Sleep(delay)
 		_, err := api.List(ctx)
 		expectDeny("list", err)
 	}
 	{ // Import
 		api.UI.ShowInfo("Please reject new account-request")
+		time.Sleep(delay)
 		_, err := api.New(ctx)
 		expectDeny("newaccount", err)
 	}
 	{ // Metadata
 		api.UI.ShowInfo("Please check if you see the Origin in next listing (approve or deny)")
+		time.Sleep(delay)
 		api.List(context.WithValue(ctx, "Origin", "origin.com"))
 		expectResponse("metadata - origin", "Did you see origin (origin.com)? [yes/no] ", "yes")
 	}
diff --git a/common/math/big.go b/common/math/big.go
index 9d2e7946d..d31c59af1 100644
--- a/common/math/big.go
+++ b/common/math/big.go
@@ -42,6 +42,13 @@ const (
 // HexOrDecimal256 marshals big.Int as hex or decimal.
 type HexOrDecimal256 big.Int
 
+// NewHexOrDecimal256 creates a new HexOrDecimal256
+func NewHexOrDecimal256(x int64) *HexOrDecimal256 {
+	b := big.NewInt(x)
+	h := HexOrDecimal256(*b)
+	return &h
+}
+
 // UnmarshalText implements encoding.TextUnmarshaler.
 func (i *HexOrDecimal256) UnmarshalText(input []byte) error {
 	bigint, ok := ParseBig256(string(input))
diff --git a/signer/core/api.go b/signer/core/api.go
index 783aaece4..73a94634e 100644
--- a/signer/core/api.go
+++ b/signer/core/api.go
@@ -482,7 +482,6 @@ func (api *SignerAPI) SignTransaction(ctx context.Context, args SendTxArgs, meth
 			return nil, err
 		}
 	}
-
 	req := SignTxRequest{
 		Transaction: args,
 		Meta:        MetadataFromContext(ctx),
diff --git a/signer/core/signed_data.go b/signer/core/signed_data.go
index 9dfd7b3f6..27eca9183 100644
--- a/signer/core/signed_data.go
+++ b/signer/core/signed_data.go
@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"math/big"
 	"mime"
+	"reflect"
 	"regexp"
 	"sort"
 	"strconv"
@@ -95,6 +96,9 @@ func (t *Type) typeName() string {
 }
 
 func (t *Type) isReferenceType() bool {
+	if len(t.Type) == 0 {
+		return false
+	}
 	// Reference types must have a leading uppercase characer
 	return unicode.IsUpper([]rune(t.Type)[0])
 }
@@ -109,11 +113,11 @@ type TypePriority struct {
 type TypedDataMessage = map[string]interface{}
 
 type TypedDataDomain struct {
-	Name              string   `json:"name"`
-	Version           string   `json:"version"`
-	ChainId           *big.Int `json:"chainId"`
-	VerifyingContract string   `json:"verifyingContract"`
-	Salt              string   `json:"salt"`
+	Name              string                `json:"name"`
+	Version           string                `json:"version"`
+	ChainId           *math.HexOrDecimal256 `json:"chainId"`
+	VerifyingContract string                `json:"verifyingContract"`
+	Salt              string                `json:"salt"`
 }
 
 var typedDataReferenceTypeRegexp = regexp.MustCompile(`^[A-Z](\w*)(\[\])?$`)
@@ -323,7 +327,10 @@ func (api *SignerAPI) SignTypedData(ctx context.Context, addr common.MixedcaseAd
 	}
 	rawData := []byte(fmt.Sprintf("\x19\x01%s%s", string(domainSeparator), string(typedDataHash)))
 	sighash := crypto.Keccak256(rawData)
-	message := typedData.Format()
+	message, err := typedData.Format()
+	if err != nil {
+		return nil, err
+	}
 	req := &SignDataRequest{ContentType: DataTyped.Mime, Rawdata: rawData, Message: message, Hash: sighash}
 	signature, err := api.sign(addr, req, true)
 	if err != nil {
@@ -377,9 +384,11 @@ func (typedData *TypedData) Dependencies(primaryType string, found []string) []s
 func (typedData *TypedData) EncodeType(primaryType string) hexutil.Bytes {
 	// Get dependencies primary first, then alphabetical
 	deps := typedData.Dependencies(primaryType, []string{})
-	slicedDeps := deps[1:]
-	sort.Strings(slicedDeps)
-	deps = append([]string{primaryType}, slicedDeps...)
+	if len(deps) > 0 {
+		slicedDeps := deps[1:]
+		sort.Strings(slicedDeps)
+		deps = append([]string{primaryType}, slicedDeps...)
+	}
 
 	// Format as a string with fields
 	var buffer bytes.Buffer
@@ -476,10 +485,60 @@ func (typedData *TypedData) EncodeData(primaryType string, data map[string]inter
 	return buffer.Bytes(), nil
 }
 
+func parseInteger(encType string, encValue interface{}) (*big.Int, error) {
+	var (
+		length = 0
+		signed = strings.HasPrefix(encType, "int")
+		b      *big.Int
+	)
+	if encType == "int" || encType == "uint" {
+		length = 256
+	} else {
+		lengthStr := ""
+		if strings.HasPrefix(encType, "uint") {
+			lengthStr = strings.TrimPrefix(encType, "uint")
+		} else {
+			lengthStr = strings.TrimPrefix(encType, "int")
+		}
+		atoiSize, err := strconv.Atoi(lengthStr)
+		if err != nil {
+			return nil, fmt.Errorf("invalid size on integer: %v", lengthStr)
+		}
+		length = atoiSize
+	}
+	switch v := encValue.(type) {
+	case *math.HexOrDecimal256:
+		b = (*big.Int)(v)
+	case string:
+		var hexIntValue math.HexOrDecimal256
+		if err := hexIntValue.UnmarshalText([]byte(v)); err != nil {
+			return nil, err
+		}
+		b = (*big.Int)(&hexIntValue)
+	case float64:
+		// JSON parses non-strings as float64. Fail if we cannot
+		// convert it losslessly
+		if float64(int64(v)) == v {
+			b = big.NewInt(int64(v))
+		} else {
+			return nil, fmt.Errorf("invalid float value %v for type %v", v, encType)
+		}
+	}
+	if b == nil {
+		return nil, fmt.Errorf("invalid integer value %v/%v for type %v", encValue, reflect.TypeOf(encValue), encType)
+	}
+	if b.BitLen() > length {
+		return nil, fmt.Errorf("integer larger than '%v'", encType)
+	}
+	if !signed && b.Sign() == -1 {
+		return nil, fmt.Errorf("invalid negative value for unsigned type %v", encType)
+	}
+	return b, nil
+}
+
 // EncodePrimitiveValue deals with the primitive values found
 // while searching through the typed data
 func (typedData *TypedData) EncodePrimitiveValue(encType string, encValue interface{}, depth int) ([]byte, error) {
-
 	switch encType {
 	case "address":
 		stringValue, ok := encValue.(string)
@@ -527,30 +586,11 @@ func (typedData *TypedData) EncodePrimitiveValue(encType string, encValue interf
 		}
 	}
 	if strings.HasPrefix(encType, "int") || strings.HasPrefix(encType, "uint") {
-		length := 0
-		if encType == "int" || encType == "uint" {
-			length = 256
-		} else {
-			lengthStr := ""
-			if strings.HasPrefix(encType, "uint") {
-				lengthStr = strings.TrimPrefix(encType, "uint")
-			} else {
-				lengthStr = strings.TrimPrefix(encType, "int")
-			}
-			atoiSize, err := strconv.Atoi(lengthStr)
-			if err != nil {
-				return nil, fmt.Errorf("invalid size on integer: %v", lengthStr)
-			}
-			length = atoiSize
-		}
-		bigIntValue, ok := encValue.(*big.Int)
-		if bigIntValue.BitLen() > length {
-			return nil, fmt.Errorf("integer larger than '%v'", encType)
-		}
-		if !ok {
-			return nil, dataMismatchError(encType, encValue)
+		b, err := parseInteger(encType, encValue)
+		if err != nil {
+			return nil, err
 		}
-		return abi.U256(bigIntValue), nil
+		return abi.U256(b), nil
 	}
 	return nil, fmt.Errorf("unrecognized type '%s'", encType)
 
@@ -649,35 +689,32 @@ func (typedData *TypedData) Map() map[string]interface{} {
 	return dataMap
 }
 
-// PrettyPrint generates a nice output to help the users
-// of clef present data in their apps
-func (typedData *TypedData) PrettyPrint() string {
-	output := bytes.Buffer{}
-	formatted := typedData.Format()
-	for _, item := range formatted {
-		output.WriteString(fmt.Sprintf("%v\n", item.Pprint(0)))
-	}
-	return output.String()
-}
-
 // Format returns a representation of typedData, which can be easily displayed by a user-interface
 // without in-depth knowledge about 712 rules
-func (typedData *TypedData) Format() []*NameValueType {
+func (typedData *TypedData) Format() ([]*NameValueType, error) {
+	domain, err := typedData.formatData("EIP712Domain", typedData.Domain.Map())
+	if err != nil {
+		return nil, err
+	}
+	ptype, err := typedData.formatData(typedData.PrimaryType, typedData.Message)
+	if err != nil {
+		return nil, err
+	}
 	var nvts []*NameValueType
 	nvts = append(nvts, &NameValueType{
 		Name:  "EIP712Domain",
-		Value: typedData.formatData("EIP712Domain", typedData.Domain.Map()),
+		Value: domain,
 		Typ:   "domain",
 	})
 	nvts = append(nvts, &NameValueType{
 		Name:  typedData.PrimaryType,
-		Value: typedData.formatData(typedData.PrimaryType, typedData.Message),
+		Value: ptype,
 		Typ:   "primary type",
 	})
-	return nvts
+	return nvts, nil
 }
 
-func (typedData *TypedData) formatData(primaryType string, data map[string]interface{}) []*NameValueType {
+func (typedData *TypedData) formatData(primaryType string, data map[string]interface{}) ([]*NameValueType, error) {
 	var output []*NameValueType
 
 	// Add field contents. Structs and arrays have special handlers.
@@ -694,44 +731,70 @@ func (typedData *TypedData) formatData(primaryType string, data map[string]inter
 			for _, v := range arrayValue {
 				if typedData.Types[parsedType] != nil {
 					mapValue, _ := v.(map[string]interface{})
-					mapOutput := typedData.formatData(parsedType, mapValue)
+					mapOutput, err := typedData.formatData(parsedType, mapValue)
+					if err != nil {
+						return nil, err
+					}
 					item.Value = mapOutput
 				} else {
-					primitiveOutput := formatPrimitiveValue(field.Type, encValue)
+					primitiveOutput, err := formatPrimitiveValue(field.Type, encValue)
+					if err != nil {
+						return nil, err
+					}
 					item.Value = primitiveOutput
 				}
 			}
 		} else if typedData.Types[field.Type] != nil {
-			mapValue, _ := encValue.(map[string]interface{})
-			mapOutput := typedData.formatData(field.Type, mapValue)
-			item.Value = mapOutput
+			if mapValue, ok := encValue.(map[string]interface{}); ok {
+				mapOutput, err := typedData.formatData(field.Type, mapValue)
+				if err != nil {
+					return nil, err
+				}
+				item.Value = mapOutput
+			} else {
+				item.Value = "<nil>"
+			}
 		} else {
-			primitiveOutput := formatPrimitiveValue(field.Type, encValue)
+			primitiveOutput, err := formatPrimitiveValue(field.Type, encValue)
+			if err != nil {
+				return nil, err
+			}
 			item.Value = primitiveOutput
 		}
 		output = append(output, item)
 	}
-	return output
+	return output, nil
 }
 
-func formatPrimitiveValue(encType string, encValue interface{}) string {
+func formatPrimitiveValue(encType string, encValue interface{}) (string, error) {
 	switch encType {
 	case "address":
-		stringValue, _ := encValue.(string)
-		return common.HexToAddress(stringValue).String()
+		if stringValue, ok := encValue.(string); !ok {
+			return "", fmt.Errorf("could not format value %v as address", encValue)
+		} else {
+			return common.HexToAddress(stringValue).String(), nil
+		}
 	case "bool":
-		boolValue, _ := encValue.(bool)
-		return fmt.Sprintf("%t", boolValue)
+		if boolValue, ok := encValue.(bool); !ok {
+			return "", fmt.Errorf("could not format value %v as bool", encValue)
+		} else {
+			return fmt.Sprintf("%t", boolValue), nil
+		}
 	case "bytes", "string":
-		return fmt.Sprintf("%s", encValue)
+		return fmt.Sprintf("%s", encValue), nil
 	}
 	if strings.HasPrefix(encType, "bytes") {
-		return fmt.Sprintf("%s", encValue)
-	} else if strings.HasPrefix(encType, "uint") || strings.HasPrefix(encType, "int") {
-		bigIntValue, _ := encValue.(*big.Int)
-		return fmt.Sprintf("%d (0x%x)", bigIntValue, bigIntValue)
+		return fmt.Sprintf("%s", encValue), nil
+
+	}
+	if strings.HasPrefix(encType, "uint") || strings.HasPrefix(encType, "int") {
+		if b, err := parseInteger(encType, encValue); err != nil {
+			return "", err
+		} else {
+			return fmt.Sprintf("%d (0x%x)", b, b), nil
+		}
 	}
-	return "NA"
+	return "", fmt.Errorf("unhandled type %v", encType)
 }
 
 // NameValueType is a very simple struct with Name, Value and Type. It's meant for simple
@@ -762,12 +825,21 @@ func (nvt *NameValueType) Pprint(depth int) string {
 // Validate checks if the types object is conformant to the specs
 func (t Types) validate() error {
 	for typeKey, typeArr := range t {
-		for _, typeObj := range typeArr {
+		if len(typeKey) == 0 {
+			return fmt.Errorf("empty type key")
+		}
+		for i, typeObj := range typeArr {
+			if len(typeObj.Type) == 0 {
+				return fmt.Errorf("type %v:%d: empty Type", typeKey, i)
+			}
+			if len(typeObj.Name) == 0 {
+				return fmt.Errorf("type %v:%d: empty Name", typeKey, i)
+			}
 			if typeKey == typeObj.Type {
 				return fmt.Errorf("type '%s' cannot reference itself", typeObj.Type)
 			}
 			if typeObj.isReferenceType() {
-				if _, exist := t[typeObj.Type]; !exist {
+				if _, exist := t[typeObj.typeName()]; !exist {
 					return fmt.Errorf("reference type '%s' is undefined", typeObj.Type)
 				}
 				if !typedDataReferenceTypeRegexp.MatchString(typeObj.Type) {
@@ -895,7 +967,7 @@ func isPrimitiveTypeValid(primitiveType string) bool {
 // validate checks if the given domain is valid, i.e. contains at least
 // the minimum viable keys and values
 func (domain *TypedDataDomain) validate() error {
-	if domain.ChainId == big.NewInt(0) {
+	if domain.ChainId == nil {
 		return errors.New("chainId must be specified according to EIP-155")
 	}
 
diff --git a/signer/core/signed_data_internal_test.go b/signer/core/signed_data_internal_test.go
new file mode 100644
index 000000000..b81872566
--- /dev/null
+++ b/signer/core/signed_data_internal_test.go
@@ -0,0 +1,51 @@
+// Copyright 2019 The go-ethereum Authors
+// This file is part of go-ethereum.
+//
+// go-ethereum is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// go-ethereum is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
+//
+package core
+
+import (
+	"math/big"
+	"testing"
+)
+
+func TestParseInteger(t *testing.T) {
+	for i, tt := range []struct {
+		t   string
+		v   interface{}
+		exp *big.Int
+	}{
+		{"uint32", "-123", nil},
+		{"int32", "-123", big.NewInt(-123)},
+		{"uint32", "0xff", big.NewInt(0xff)},
+		{"int8", "0xffff", nil},
+	} {
+		res, err := parseInteger(tt.t, tt.v)
+		if tt.exp == nil && res == nil {
+			continue
+		}
+		if tt.exp == nil && res != nil {
+			t.Errorf("test %d, got %v, expected nil", i, res)
+			continue
+		}
+		if tt.exp != nil && res == nil {
+			t.Errorf("test %d, got '%v', expected %v", i, err, tt.exp)
+			continue
+		}
+		if tt.exp.Cmp(res) != 0 {
+			t.Errorf("test %d, got %v expected %v", i, res, tt.exp)
+		}
+	}
+}
diff --git a/signer/core/signed_data_test.go b/signer/core/signed_data_test.go
index f7d199422..5a18defaa 100644
--- a/signer/core/signed_data_test.go
+++ b/signer/core/signed_data_test.go
@@ -20,12 +20,16 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"math/big"
+	"io/ioutil"
+	"path"
+	"strings"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/accounts/keystore"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/signer/core"
 )
 
@@ -128,7 +132,7 @@ var jsonTypedData = `
       "domain": {
         "name": "Ether Mail",
         "version": "1",
-        "chainId": 1,
+        "chainId": "1",
         "verifyingContract": "0xCCCcccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
       },
       "message": {
@@ -151,7 +155,7 @@ const primaryType = "Mail"
 var domainStandard = core.TypedDataDomain{
 	"Ether Mail",
 	"1",
-	big.NewInt(1),
+	math.NewHexOrDecimal256(1),
 	"0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC",
 	"",
 }
@@ -241,7 +245,6 @@ func TestDomainChainId(t *testing.T) {
 	if _, ok := withoutChainID.Domain.Map()["chainId"]; ok {
 		t.Errorf("Expected the chainId key to not be present in the domain map")
 	}
-
 	withChainID := core.TypedData{
 		Types: core.Types{
 			"EIP712Domain": []core.Type{
@@ -251,7 +254,7 @@ func TestDomainChainId(t *testing.T) {
 		},
 		Domain: core.TypedDataDomain{
 			Name:    "test",
-			ChainId: big.NewInt(1),
+			ChainId: math.NewHexOrDecimal256(1),
 		},
 	}
 
@@ -310,499 +313,96 @@ func TestEncodeData(t *testing.T) {
 	}
 }
 
-func TestMalformedDomainkeys(t *testing.T) {
-	// Verifies that malformed domain keys are properly caught:
-	//{
-	//	"name": "Ether Mail",
-	//	"version": "1",
-	//	"chainId": 1,
-	//	"vxerifyingContract": "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
-	//}
-	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": "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,
-        "vxerifyingContract": "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
-      },
-      "message": {
-        "from": {
-          "name": "Cow",
-          "wallet": "0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
-        },
-        "to": {
-          "name": "Bob",
-          "wallet": "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB"
-        },
-        "contents": "Hello, Bob!"
-      }
-    }
-`
-	var malformedDomainTypedData core.TypedData
-	err := json.Unmarshal([]byte(jsonTypedData), &malformedDomainTypedData)
-	if err != nil {
-		t.Fatalf("unmarshalling failed '%v'", err)
-	}
-	_, err = malformedDomainTypedData.HashStruct("EIP712Domain", malformedDomainTypedData.Domain.Map())
-	if err == nil || err.Error() != "provided data '<nil>' doesn't match type 'address'" {
-		t.Errorf("Expected `provided data '<nil>' doesn't match type 'address'`, got '%v'", err)
-	}
-}
-
-func TestMalformedTypesAndExtradata(t *testing.T) {
-	// Verifies several quirks
-	// 1. Using dynamic types and only validating the prefix:
-	//{
-	//	"name": "chainId",
-	//	"type": "uint256 ... and now for something completely different"
-	//}
-	// 2. Extra data in message:
-	//{
-	//  "blahonga": "zonk bonk"
-	//}
-	jsonTypedData := `
-    {
-      "types": {
-        "EIP712Domain": [
-          {
-            "name": "name",
-            "type": "string"
-          },
-          {
-            "name": "version",
-            "type": "string"
-          },
-          {
-            "name": "chainId",
-            "type": "uint256 ... and now for something completely different"
-          },
-          {
-            "name": "verifyingContract",
-            "type": "address"
-          }
-        ],
-        "Person": [
-          {
-            "name": "name",
-            "type": "string"
-          },
-          {
-            "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",
-          "wallet": "0xcD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
-        },
-        "to": {
-          "name": "Bob",
-          "wallet": "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB"
-        },
-        "contents": "Hello, Bob!"
-      }
-    }
-`
-	var malformedTypedData core.TypedData
-	err := json.Unmarshal([]byte(jsonTypedData), &malformedTypedData)
-	if err != nil {
-		t.Fatalf("unmarshalling failed '%v'", err)
-	}
-
-	malformedTypedData.Types["EIP712Domain"][2].Type = "uint256"
-	malformedTypedData.Message["blahonga"] = "zonk bonk"
-	_, err = malformedTypedData.HashStruct(malformedTypedData.PrimaryType, malformedTypedData.Message)
-	if err == nil || err.Error() != "there is extra data provided in the message" {
-		t.Errorf("Expected `there is extra data provided in the message`, got '%v'", err)
-	}
-}
-
-func TestTypeMismatch(t *testing.T) {
-	// Verifies that:
-	// 1. Mismatches between the given type and data, i.e. `Person` and
-	// 		the data item is a string, are properly caught:
-	//{
-	//	"name": "contents",
-	//	"type": "Person"
-	//},
-	//{
-	//	"contents": "Hello, Bob!" <-- string not "Person"
-	//}
-	// 2. Nonexistent types are properly caught:
-	//{
-	//	"name": "contents",
-	//	"type": "Blahonga"
-	//}
-	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": "wallet",
-            "type": "address"
-          }
-        ],
-        "Mail": [
-          {
-            "name": "from",
-            "type": "Person"
-          },
-          {
-            "name": "to",
-            "type": "Person"
-          },
-          {
-            "name": "contents",
-            "type": "Person"
-          }
-        ]
-      },
-      "primaryType": "Mail",
-      "domain": {
-        "name": "Ether Mail",
-        "version": "1",
-        "chainId": 1,
-        "verifyingContract": "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
-      },
-      "message": {
-        "from": {
-          "name": "Cow",
-          "wallet": "0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
-        },
-        "to": {
-          "name": "Bob",
-          "wallet": "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB"
-        },
-        "contents": "Hello, Bob!"
-      }
-    }
-`
-	var mismatchTypedData core.TypedData
-	err := json.Unmarshal([]byte(jsonTypedData), &mismatchTypedData)
-	if err != nil {
-		t.Fatalf("unmarshalling failed '%v'", err)
-	}
-	_, err = mismatchTypedData.HashStruct(mismatchTypedData.PrimaryType, mismatchTypedData.Message)
-	if err.Error() != "provided data 'Hello, Bob!' doesn't match type 'Person'" {
-		t.Errorf("Expected `provided data 'Hello, Bob!' doesn't match type 'Person'`, got '%v'", err)
-	}
-
-	mismatchTypedData.Types["Mail"][2].Type = "Blahonga"
-	_, err = mismatchTypedData.HashStruct(mismatchTypedData.PrimaryType, mismatchTypedData.Message)
-	if err == nil || err.Error() != "reference type 'Blahonga' is undefined" {
-		t.Fatalf("Expected `reference type 'Blahonga' is undefined`, got '%v'", err)
-	}
-}
-
-func TestTypeOverflow(t *testing.T) {
-	// Verifies data that doesn't fit into it:
-	//{
-	//	"test": 65536 <-- test defined as uint8
-	//}
-	var overflowTypedData core.TypedData
-	err := json.Unmarshal([]byte(jsonTypedData), &overflowTypedData)
+func TestFormatter(t *testing.T) {
+	var d core.TypedData
+	err := json.Unmarshal([]byte(jsonTypedData), &d)
 	if err != nil {
 		t.Fatalf("unmarshalling failed '%v'", err)
 	}
-	// Set test to something outside uint8
-	(overflowTypedData.Message["from"]).(map[string]interface{})["test"] = big.NewInt(65536)
-
-	_, err = overflowTypedData.HashStruct(overflowTypedData.PrimaryType, overflowTypedData.Message)
-	if err == nil || err.Error() != "integer larger than 'uint8'" {
-		t.Fatalf("Expected `integer larger than 'uint8'`, got '%v'", err)
+	formatted, _ := d.Format()
+	for _, item := range formatted {
+		fmt.Printf("'%v'\n", item.Pprint(0))
 	}
 
-	(overflowTypedData.Message["from"]).(map[string]interface{})["test"] = big.NewInt(3)
-	(overflowTypedData.Message["to"]).(map[string]interface{})["test"] = big.NewInt(4)
-
-	_, err = overflowTypedData.HashStruct(overflowTypedData.PrimaryType, overflowTypedData.Message)
-	if err != nil {
-		t.Fatalf("Expected no err, got '%v'", err)
-	}
+	j, _ := json.Marshal(formatted)
+	fmt.Printf("'%v'\n", string(j))
 }
 
-func TestArray(t *testing.T) {
-	// Makes sure that arrays work fine
-	//{
-	//	"type": "address[]"
-	//},
-	//{
-	//	"type": "string[]"
-	//},
-	//{
-	//	"type": "uint16[]",
-	//}
-
-	jsonTypedData := `
-		{
-	      "types": {
-	        "EIP712Domain": [
-	          {
-	            "name": "name",
-	            "type": "string"
-	          },
-	          {
-	            "name": "version",
-	            "type": "string"
-	          },
-	          {
-	            "name": "chainId",
-	            "type": "uint256"
-	          },
-	          {
-	            "name": "verifyingContract",
-	            "type": "address"
-	          }
-	        ],
-	        "Foo": [
-	          {
-	            "name": "bar",
-	            "type": "address[]"
-	          }
-	        ]
-	      },
-	      "primaryType": "Foo",
-	      "domain": {
-	        "name": "Lorem",
-	        "version": "1",
-	        "chainId": 1,
-	        "verifyingContract": "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
-	      },
-	      "message": {
-	        "bar": [
-	        	"0x0000000000000000000000000000000000000001",
-	        	"0x0000000000000000000000000000000000000002",
-	        	"0x0000000000000000000000000000000000000003"
-        	]
-	      }
-	    }
-	`
-	var arrayTypedData core.TypedData
-	err := json.Unmarshal([]byte(jsonTypedData), &arrayTypedData)
+func sign(typedData core.TypedData) ([]byte, []byte, error) {
+	domainSeparator, err := typedData.HashStruct("EIP712Domain", typedData.Domain.Map())
 	if err != nil {
-		t.Fatalf("unmarshalling failed '%v'", err)
+		return nil, nil, err
 	}
-	_, err = arrayTypedData.HashStruct(arrayTypedData.PrimaryType, arrayTypedData.Message)
+	typedDataHash, err := typedData.HashStruct(typedData.PrimaryType, typedData.Message)
 	if err != nil {
-		t.Fatalf("Expected no err, got '%v'", err)
-	}
-
-	// Change array to string
-	arrayTypedData.Types["Foo"][0].Type = "string[]"
-	arrayTypedData.Message["bar"] = []interface{}{
-		"lorem",
-		"ipsum",
-		"dolores",
-	}
-	_, err = arrayTypedData.HashStruct(arrayTypedData.PrimaryType, arrayTypedData.Message)
-	if err != nil {
-		t.Fatalf("Expected no err, got '%v'", err)
-	}
-
-	// Change array to uint
-	arrayTypedData.Types["Foo"][0].Type = "uint[]"
-	arrayTypedData.Message["bar"] = []interface{}{
-		big.NewInt(1955),
-		big.NewInt(108),
-		big.NewInt(44010),
-	}
-	_, err = arrayTypedData.HashStruct(arrayTypedData.PrimaryType, arrayTypedData.Message)
-	if err != nil {
-		t.Fatalf("Expected no err, got '%v'", err)
-	}
-
-	// Should not work with fixed-size arrays
-	arrayTypedData.Types["Foo"][0].Type = "uint[3]"
-	_, err = arrayTypedData.HashStruct(arrayTypedData.PrimaryType, arrayTypedData.Message)
-	if err == nil || err.Error() != "unknown type 'uint[3]'" {
-		t.Fatalf("Expected `unknown type 'uint[3]'`, got '%v'", err)
+		return nil, nil, err
 	}
+	rawData := []byte(fmt.Sprintf("\x19\x01%s%s", string(domainSeparator), string(typedDataHash)))
+	sighash := crypto.Keccak256(rawData)
+	return typedDataHash, sighash, nil
 }
 
-func TestCustomTypeAsArray(t *testing.T) {
-	var 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": "wallet",
-            "type": "address"
-          }
-        ],
-        "Person[]": [
-          {
-			"name": "baz",
-            "type": "string"
-          }
-		],
-        "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",
-			"wallet": "0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
-        },
-        "to": {"baz": "foo"},
-        "contents": "Hello, Bob!"
-      }
-    }
-
-`
-	var malformedTypedData core.TypedData
-	err := json.Unmarshal([]byte(jsonTypedData), &malformedTypedData)
+func TestJsonFiles(t *testing.T) {
+	testfiles, err := ioutil.ReadDir("testdata/")
 	if err != nil {
-		t.Fatalf("unmarshalling failed '%v'", err)
-	}
-	_, err = malformedTypedData.HashStruct("EIP712Domain", malformedTypedData.Domain.Map())
-	if err != nil {
-		t.Errorf("Expected no error, got '%v'", err)
+		t.Fatalf("failed reading files: %v", err)
+	}
+	for i, fInfo := range testfiles {
+		if !strings.HasSuffix(fInfo.Name(), "json") {
+			continue
+		}
+		expectedFailure := strings.HasPrefix(fInfo.Name(), "expfail")
+		data, err := ioutil.ReadFile(path.Join("testdata", fInfo.Name()))
+		if err != nil {
+			t.Errorf("Failed to read file %v: %v", fInfo.Name(), err)
+			continue
+		}
+		var typedData core.TypedData
+		err = json.Unmarshal([]byte(data), &typedData)
+		if err != nil {
+			t.Errorf("Test %d, file %v, json unmarshalling failed: %v", i, fInfo.Name(), err)
+			continue
+		}
+		_, _, err = sign(typedData)
+		fmt.Printf("Error %v\n", err)
+		if err != nil && !expectedFailure {
+			t.Errorf("Test %d failed, file %v: %v", i, fInfo.Name(), err)
+		}
+		if expectedFailure && err == nil {
+			t.Errorf("Test %d succeeded (expected failure), file %v: %v", i, fInfo.Name(), err)
+		}
 	}
 }
 
-func TestFormatter(t *testing.T) {
-	var d core.TypedData
-	err := json.Unmarshal([]byte(jsonTypedData), &d)
+// TestFuzzerFiles tests some files that have been found by fuzzing to cause
+// crashes or hangs.
+func TestFuzzerFiles(t *testing.T) {
+	corpusdir := path.Join("testdata", "fuzzing")
+	testfiles, err := ioutil.ReadDir(corpusdir)
 	if err != nil {
-		t.Fatalf("unmarshalling failed '%v'", err)
+		t.Fatalf("failed reading files: %v", err)
+	}
+	verbose := false
+	for i, fInfo := range testfiles {
+		data, err := ioutil.ReadFile(path.Join(corpusdir, fInfo.Name()))
+		if err != nil {
+			t.Errorf("Failed to read file %v: %v", fInfo.Name(), err)
+			continue
+		}
+		var typedData core.TypedData
+		err = json.Unmarshal([]byte(data), &typedData)
+		if err != nil {
+			t.Errorf("Test %d, file %v, json unmarshalling failed: %v", i, fInfo.Name(), err)
+			continue
+		}
+		_, err = typedData.EncodeData("EIP712Domain", typedData.Domain.Map(), 1)
+		if verbose && err != nil {
+			fmt.Printf("%d, EncodeData[1] err: %v\n", i, err)
+		}
+		_, err = typedData.EncodeData(typedData.PrimaryType, typedData.Message, 1)
+		if verbose && err != nil {
+			fmt.Printf("%d, EncodeData[2] err: %v\n", i, err)
+		}
+		typedData.Format()
 	}
-	formatted := d.Format()
-	for _, item := range formatted {
-		fmt.Printf("'%v'\n", item.Pprint(0))
-	}
-
-	j, _ := json.Marshal(formatted)
-	fmt.Printf("'%v'\n", string(j))
 }
diff --git a/signer/core/testdata/README.md b/signer/core/testdata/README.md
new file mode 100644
index 000000000..f425450a0
--- /dev/null
+++ b/signer/core/testdata/README.md
@@ -0,0 +1,5 @@
+### EIP 712 tests
+
+These tests are json files which are converted into eip-712 typed data. 
+All files are expected to be proper json, and tests will fail if they are not. 
+Files that begin with `expfail' are expected to not pass the hashstruct construction. 
diff --git a/signer/core/testdata/arrays-1.json b/signer/core/testdata/arrays-1.json
new file mode 100644
index 000000000..fea82b42c
--- /dev/null
+++ b/signer/core/testdata/arrays-1.json
@@ -0,0 +1,60 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "uint256"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Foo": [
+      {
+        "name": "addys",
+        "type": "address[]"
+      },
+      {
+        "name": "stringies",
+        "type": "string[]"
+      },
+      {
+        "name": "inties",
+        "type": "uint[]"
+      }
+    ]
+  },
+  "primaryType": "Foo",
+  "domain": {
+    "name": "Lorem",
+    "version": "1",
+    "chainId": "1",
+    "verifyingContract": "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
+  },
+  "message": {
+    "addys": [
+      "0x0000000000000000000000000000000000000001",
+      "0x0000000000000000000000000000000000000002",
+      "0x0000000000000000000000000000000000000003"
+    ],
+    "stringies": [
+      "lorem",
+      "ipsum",
+      "dolores"
+    ],
+    "inties": [
+      "0x0000000000000000000000000000000000000001",
+      "3",
+      4.0
+    ]
+  }
+}
diff --git a/signer/core/testdata/custom_arraytype.json b/signer/core/testdata/custom_arraytype.json
new file mode 100644
index 000000000..078de88c2
--- /dev/null
+++ b/signer/core/testdata/custom_arraytype.json
@@ -0,0 +1,54 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "uint256"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Person": [
+      {
+        "name": "name",
+        "type": "string"
+      }
+    ],
+    "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"},
+    "to": [{ "name": "Moose"},{ "name": "Goose"}],
+    "contents": "Hello, Bob!"
+  }
+}
diff --git a/signer/core/testdata/eip712.json b/signer/core/testdata/eip712.json
new file mode 100644
index 000000000..7b1cb8ae2
--- /dev/null
+++ b/signer/core/testdata/eip712.json
@@ -0,0 +1,76 @@
+{
+  "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": "test2",
+        "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",
+      "test2": 5.0,
+      "wallet": "0xcD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
+    },
+    "to": {
+      "name": "Bob",
+      "test": "0",
+      "test2": 5,
+      "wallet": "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB"
+    },
+    "contents": "Hello, Bob!"
+  }
+}
diff --git a/signer/core/testdata/expfail_arraytype_overload.json b/signer/core/testdata/expfail_arraytype_overload.json
new file mode 100644
index 000000000..786487f10
--- /dev/null
+++ b/signer/core/testdata/expfail_arraytype_overload.json
@@ -0,0 +1,67 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "uint256"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Person": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "wallet",
+        "type": "address"
+      }
+    ],
+    "Person[]": [
+      {
+        "name": "baz",
+        "type": "string"
+      }
+    ],
+    "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",
+      "wallet": "0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
+    },
+    "to": {"baz": "foo"},
+    "contents": "Hello, Bob!"
+  }
+}
diff --git a/signer/core/testdata/expfail_datamismatch_1.json b/signer/core/testdata/expfail_datamismatch_1.json
new file mode 100644
index 000000000..d19d470d1
--- /dev/null
+++ b/signer/core/testdata/expfail_datamismatch_1.json
@@ -0,0 +1,64 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "uint256"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Person": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "wallet",
+        "type": "address"
+      }
+    ],
+    "Mail": [
+      {
+        "name": "from",
+        "type": "Person"
+      },
+      {
+        "name": "to",
+        "type": "Person"
+      },
+      {
+        "name": "contents",
+        "type": "Person"
+      }
+    ]
+  },
+  "primaryType": "Mail",
+  "domain": {
+    "name": "Ether Mail",
+    "version": "1",
+    "chainId": "1",
+    "verifyingContract": "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
+  },
+  "message": {
+    "from": {
+      "name": "Cow",
+      "wallet": "0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
+    },
+    "to": {
+      "name": "Bob",
+      "wallet": "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB"
+    },
+    "contents": "Hello, Bob!"
+  }
+}
diff --git a/signer/core/testdata/expfail_extradata-1.json b/signer/core/testdata/expfail_extradata-1.json
new file mode 100644
index 000000000..fd704209b
--- /dev/null
+++ b/signer/core/testdata/expfail_extradata-1.json
@@ -0,0 +1,76 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "uint256 ... and now for something completely different"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Person": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "test",
+        "type": "uint8"
+      },
+      {
+        "name": "test2",
+        "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",
+      "test2": 5.0,
+      "wallet": "0xcD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
+    },
+    "to": {
+      "name": "Bob",
+      "test": "0",
+      "test2": 5,
+      "wallet": "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB"
+    },
+    "contents": "Hello, Bob!"
+  }
+}
diff --git a/signer/core/testdata/expfail_extradata-2.json b/signer/core/testdata/expfail_extradata-2.json
new file mode 100644
index 000000000..10f91c23a
--- /dev/null
+++ b/signer/core/testdata/expfail_extradata-2.json
@@ -0,0 +1,77 @@
+{
+  "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": "test2",
+        "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": {
+    "blahonga": "zonk bonk",
+    "from": {
+      "name": "Cow",
+      "test": "3",
+      "test2": 5.0,
+      "wallet": "0xcD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
+    },
+    "to": {
+      "name": "Bob",
+      "test": "0",
+      "test2": 5,
+      "wallet": "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB"
+    },
+    "contents": "Hello, Bob!"
+  }
+}
diff --git a/signer/core/testdata/expfail_malformeddomainkeys.json b/signer/core/testdata/expfail_malformeddomainkeys.json
new file mode 100644
index 000000000..354b3cc85
--- /dev/null
+++ b/signer/core/testdata/expfail_malformeddomainkeys.json
@@ -0,0 +1,64 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "uint256"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Person": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "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",
+    "vFAILFAILerifyingContract": "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
+  },
+  "message": {
+    "from": {
+      "name": "Cow",
+      "wallet": "0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
+    },
+    "to": {
+      "name": "Bob",
+      "wallet": "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB"
+    },
+    "contents": "Hello, Bob!"
+  }
+}
diff --git a/signer/core/testdata/expfail_nonexistant_type.json b/signer/core/testdata/expfail_nonexistant_type.json
new file mode 100644
index 000000000..d06bc20b9
--- /dev/null
+++ b/signer/core/testdata/expfail_nonexistant_type.json
@@ -0,0 +1,64 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "uint256"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Person": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "wallet",
+        "type": "address"
+      }
+    ],
+    "Mail": [
+      {
+        "name": "from",
+        "type": "Person"
+      },
+      {
+        "name": "to",
+        "type": "Person"
+      },
+      {
+        "name": "contents",
+        "type": "Blahonga"
+      }
+    ]
+  },
+  "primaryType": "Mail",
+  "domain": {
+    "name": "Ether Mail",
+    "version": "1",
+    "chainId": "1",
+    "verifyingContract": "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
+  },
+  "message": {
+    "from": {
+      "name": "Cow",
+      "wallet": "0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
+    },
+    "to": {
+      "name": "Bob",
+      "wallet": "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB"
+    },
+    "contents": "Hello, Bob!"
+  }
+}
diff --git a/signer/core/testdata/expfail_toolargeuint.json b/signer/core/testdata/expfail_toolargeuint.json
new file mode 100644
index 000000000..9854b65b1
--- /dev/null
+++ b/signer/core/testdata/expfail_toolargeuint.json
@@ -0,0 +1,38 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "uint256"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Mail": [
+      {
+        "name": "test",
+        "type": "uint8"
+      }
+    ]
+  },
+  "primaryType": "Mail",
+  "domain": {
+    "name": "Ether Mail",
+    "version": "1",
+    "chainId": "1",
+    "verifyingContract": "0xCCCcccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
+  },
+  "message": {
+    "test":"257"
+  }
+}
diff --git a/signer/core/testdata/expfail_toolargeuint2.json b/signer/core/testdata/expfail_toolargeuint2.json
new file mode 100644
index 000000000..c63ed41f9
--- /dev/null
+++ b/signer/core/testdata/expfail_toolargeuint2.json
@@ -0,0 +1,38 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "uint256"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Mail": [
+      {
+        "name": "test",
+        "type": "uint8"
+      }
+    ]
+  },
+  "primaryType": "Mail",
+  "domain": {
+    "name": "Ether Mail",
+    "version": "1",
+    "chainId": "1",
+    "verifyingContract": "0xCCCcccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
+  },
+  "message": {
+    "test":257
+  }
+}
diff --git a/signer/core/testdata/expfail_unconvertiblefloat.json b/signer/core/testdata/expfail_unconvertiblefloat.json
new file mode 100644
index 000000000..8229a333c
--- /dev/null
+++ b/signer/core/testdata/expfail_unconvertiblefloat.json
@@ -0,0 +1,38 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "uint256"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Mail": [
+      {
+        "name": "test",
+        "type": "uint8"
+      }
+    ]
+  },
+  "primaryType": "Mail",
+  "domain": {
+    "name": "Ether Mail",
+    "version": "1",
+    "chainId": "1",
+    "verifyingContract": "0xCCCcccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
+  },
+  "message": {
+    "test":"255.3"
+  }
+}
diff --git a/signer/core/testdata/expfail_unconvertiblefloat2.json b/signer/core/testdata/expfail_unconvertiblefloat2.json
new file mode 100644
index 000000000..59e6d38d2
--- /dev/null
+++ b/signer/core/testdata/expfail_unconvertiblefloat2.json
@@ -0,0 +1,38 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "uint256"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Mail": [
+      {
+        "name": "test",
+        "type": "uint8"
+      }
+    ]
+  },
+  "primaryType": "Mail",
+  "domain": {
+    "name": "Ether Mail",
+    "version": "1",
+    "chainId": "1",
+    "verifyingContract": "0xCCCcccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
+  },
+  "message": {
+    "test": 255.3
+  }
+}
diff --git a/signer/core/testdata/fuzzing/2850f6ccf2d7f5f846dfb73119b60e09e712783f b/signer/core/testdata/fuzzing/2850f6ccf2d7f5f846dfb73119b60e09e712783f
new file mode 100644
index 000000000..8229a333c
--- /dev/null
+++ b/signer/core/testdata/fuzzing/2850f6ccf2d7f5f846dfb73119b60e09e712783f
@@ -0,0 +1,38 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "uint256"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Mail": [
+      {
+        "name": "test",
+        "type": "uint8"
+      }
+    ]
+  },
+  "primaryType": "Mail",
+  "domain": {
+    "name": "Ether Mail",
+    "version": "1",
+    "chainId": "1",
+    "verifyingContract": "0xCCCcccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
+  },
+  "message": {
+    "test":"255.3"
+  }
+}
diff --git a/signer/core/testdata/fuzzing/36fb987a774011dc675e1b5246ac5c1d44d84d92 b/signer/core/testdata/fuzzing/36fb987a774011dc675e1b5246ac5c1d44d84d92
new file mode 100644
index 000000000..fea82b42c
--- /dev/null
+++ b/signer/core/testdata/fuzzing/36fb987a774011dc675e1b5246ac5c1d44d84d92
@@ -0,0 +1,60 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "uint256"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Foo": [
+      {
+        "name": "addys",
+        "type": "address[]"
+      },
+      {
+        "name": "stringies",
+        "type": "string[]"
+      },
+      {
+        "name": "inties",
+        "type": "uint[]"
+      }
+    ]
+  },
+  "primaryType": "Foo",
+  "domain": {
+    "name": "Lorem",
+    "version": "1",
+    "chainId": "1",
+    "verifyingContract": "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
+  },
+  "message": {
+    "addys": [
+      "0x0000000000000000000000000000000000000001",
+      "0x0000000000000000000000000000000000000002",
+      "0x0000000000000000000000000000000000000003"
+    ],
+    "stringies": [
+      "lorem",
+      "ipsum",
+      "dolores"
+    ],
+    "inties": [
+      "0x0000000000000000000000000000000000000001",
+      "3",
+      4.0
+    ]
+  }
+}
diff --git a/signer/core/testdata/fuzzing/37ec7b55c7ba014cced204c5f9989d2d0eb9ff6d b/signer/core/testdata/fuzzing/37ec7b55c7ba014cced204c5f9989d2d0eb9ff6d
new file mode 100644
index 000000000..c63ed41f9
--- /dev/null
+++ b/signer/core/testdata/fuzzing/37ec7b55c7ba014cced204c5f9989d2d0eb9ff6d
@@ -0,0 +1,38 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "uint256"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Mail": [
+      {
+        "name": "test",
+        "type": "uint8"
+      }
+    ]
+  },
+  "primaryType": "Mail",
+  "domain": {
+    "name": "Ether Mail",
+    "version": "1",
+    "chainId": "1",
+    "verifyingContract": "0xCCCcccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
+  },
+  "message": {
+    "test":257
+  }
+}
diff --git a/signer/core/testdata/fuzzing/582fa92154b784daa1faa293b695fa388fe34bf1 b/signer/core/testdata/fuzzing/582fa92154b784daa1faa293b695fa388fe34bf1
new file mode 100644
index 000000000..9bc43938d
--- /dev/null
+++ b/signer/core/testdata/fuzzing/582fa92154b784daa1faa293b695fa388fe34bf1
@@ -0,0 +1 @@
+{"domain":{"version":"0","chainId":""}}
\ No newline at end of file
diff --git a/signer/core/testdata/fuzzing/ab57cb2b2b5ce614efe13a47bc73814580f2cce8 b/signer/core/testdata/fuzzing/ab57cb2b2b5ce614efe13a47bc73814580f2cce8
new file mode 100644
index 000000000..fe27de916
--- /dev/null
+++ b/signer/core/testdata/fuzzing/ab57cb2b2b5ce614efe13a47bc73814580f2cce8
@@ -0,0 +1,54 @@
+{  "types": {  "":[   {
+       "name": "name",
+   "type":"string"    },
+   {
+    "name":"version",
+      "type": "string"    },     {
+     "name": "chaiI",
+    "type":"uint256 . ad nowretig omeedifere"     },     {
+     "ae": "eifinC",
+    "ty":"dess"
+    }
+ ],
+  "Person":[
+     {
+    "name":"name",
+      "type": "string"
+ },  {
+     "name":"tes",    "type":"it8"
+    },
+      {    "name":"t",      "tye":"uit8"
+    },
+    {
+       "a":"ale",
+    "type": "ress"
+     }
+    ],
+    "Mail": [
+   {
+       "name":"from",    "type":"Person"     },
+   {
+     "name": "to",        "type": "Person"
+    },
+   {
+     "name": "contents",
+     "type": "string"
+    }
+   ]
+ }, "primaryType": "Mail",
+ "domain": {
+"name":"theMail",    "version": "1",
+    "chainId": "1",
+    "verifyingntract": "0xCcccCCCcCCCCCCCcCCcCCCcCcccccC"
+  },
+  "message": {   "from": {
+    "name": "Cow",
+     "test": "3",
+      "est2":5.0,
+      "llt": "0xcD2a3938E13D947E0bE734DfDD86"   },   "to": {     "name": "Bob",
+    "ts":"",
+     "tet2": 5,
+     "allet": "0bBBBBbbBBbbbbBbbBbbbbBBBbB"
+  },
+    "contents": "Hello, Bob!"  }
+}
\ No newline at end of file
diff --git a/signer/core/testdata/fuzzing/e4303e23ca34fbbc43164a232b2caa7a3af2bf8d b/signer/core/testdata/fuzzing/e4303e23ca34fbbc43164a232b2caa7a3af2bf8d
new file mode 100644
index 000000000..c5e14b39e
--- /dev/null
+++ b/signer/core/testdata/fuzzing/e4303e23ca34fbbc43164a232b2caa7a3af2bf8d
@@ -0,0 +1,64 @@
+{
+  "types": {
+    "EIP712Domain": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "version",
+        "type": "string"
+      },
+      {
+        "name": "chainId",
+        "type": "int"
+      },
+      {
+        "name": "verifyingContract",
+        "type": "address"
+      }
+    ],
+    "Person": [
+      {
+        "name": "name",
+        "type": "string"
+      },
+      {
+        "name": "wallet",
+        "type": "address"
+      }
+    ],
+    "Mail": [
+      {
+        "name": "from",
+        "type": "Person"
+      },
+      {
+        "name": "to",
+        "type": "Mail"
+      },
+      {
+        "name": "s",
+        "type": "Person"
+      }
+    ]
+  },
+  "primaryType": "Mail",
+  "domain": {
+    "name": "l",
+    "version": "1",
+    "chainId": "",
+    "verifyingContract": "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
+  },
+  "message": {
+    "from": {
+      "name": "",
+      "wallet": "0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
+    },
+    "to": {
+      "name": "",
+      "wallet": "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB"
+    },
+    "": ""
+  }
+}
diff --git a/signer/core/testdata/fuzzing/f658340af009dd4a35abe645a00a7b732bc30921 b/signer/core/testdata/fuzzing/f658340af009dd4a35abe645a00a7b732bc30921
new file mode 100644
index 000000000..c4841cb07
--- /dev/null
+++ b/signer/core/testdata/fuzzing/f658340af009dd4a35abe645a00a7b732bc30921
@@ -0,0 +1 @@
+{"types":{"0":[{}]}}
\ No newline at end of file