fix(protocol): trailing credential data skipped

This fixes an issue where the trailing data in the credential parsing function would be ignored.

protocol/credential.go

@@ -4,6 +4,7 @@ import (
 	"crypto/sha256"
 	"encoding/base64"
 	"encoding/json"
+	"errors"
 	"io"
 	"net/http"
 )
@@ -48,7 +49,7 @@ type CredentialCreationResponse struct {
 	PublicKeyCredential
 	AttestationResponse AuthenticatorAttestationResponse `json:"response"`
 
-	// Deprecated: Transports is deprecated due to upstream changes to the API. 
+	// Deprecated: Transports is deprecated due to upstream changes to the API.
 	// Use the Transports field of AuthenticatorAttestationResponse
 	// instead. Transports is kept for backward compatibility, and should not
 	// be used by new clients.
@@ -72,10 +73,18 @@ func ParseCredentialCreationResponse(response *http.Request) (*ParsedCredentialC
 func ParseCredentialCreationResponseBody(body io.Reader) (pcc *ParsedCredentialCreationData, err error) {
 	var ccr CredentialCreationResponse
 
-	if err = json.NewDecoder(body).Decode(&ccr); err != nil {
+	decoder := json.NewDecoder(body)
+
+	if err = decoder.Decode(&ccr); err != nil {
 		return nil, ErrBadRequest.WithDetails("Parse error for Registration").WithInfo(err.Error())
 	}
 
+	_, err = decoder.Token()
+
+	if !errors.Is(err, io.EOF) {
+		return nil, ErrBadRequest.WithDetails("Parse error for Registration").WithInfo("The body contains trailing data")
+	}
+
 	return ccr.Parse()
 }
 

protocol/credential_test.go

@@ -24,10 +24,13 @@ func TestParseCredentialCreationResponse(t *testing.T) {
 	byteClientDataJSON, _ := base64.RawURLEncoding.DecodeString("eyJjaGFsbGVuZ2UiOiJXOEd6RlU4cEdqaG9SYldyTERsYW1BZnFfeTRTMUNaRzFWdW9lUkxBUnJFIiwib3JpZ2luIjoiaHR0cHM6Ly93ZWJhdXRobi5pbyIsInR5cGUiOiJ3ZWJhdXRobi5jcmVhdGUifQ")
 
 	testCases := []struct {
-		name      string
-		args      args
-		expected  *ParsedCredentialCreationData
-		errString string
+		name       string
+		args       args
+		expected   *ParsedCredentialCreationData
+		errString  string
+		errType    string
+		errDetails string
+		errInfo    string
 	}{
 		{
 			name: "ShouldParseCredentialRequest",
@@ -215,6 +218,17 @@ func TestParseCredentialCreationResponse(t *testing.T) {
 			},
 			errString: "",
 		},
+		{
+			name: "ShouldHandleTrailingData",
+			args: args{
+				responseName: "trailingData",
+			},
+			expected:   nil,
+			errString:  "Parse error for Registration",
+			errType:    "invalid_request",
+			errDetails: "Parse error for Registration",
+			errInfo:    "The body contains trailing data",
+		},
 	}
 
 	for _, tc := range testCases {
@@ -226,6 +240,8 @@ func TestParseCredentialCreationResponse(t *testing.T) {
 			if tc.errString != "" {
 				assert.EqualError(t, err, tc.errString)
 
+				AssertIsProtocolError(t, err, tc.errType, tc.errDetails, tc.errInfo)
+
 				return
 			}
 
@@ -371,6 +387,24 @@ var testCredentialRequestResponses = map[string]string{
 		"transports":["usb","nfc","fake"]
 	}
 }
+`,
+	`trailingData`: `
+{
+	"id":"6xrtBhJQW6QU4tOaB4rrHaS2Ks0yDDL_q8jDC16DEjZ-VLVf4kCRkvl2xp2D71sTPYns-exsHQHTy3G-zJRK8g",
+	"rawId":"6xrtBhJQW6QU4tOaB4rrHaS2Ks0yDDL_q8jDC16DEjZ-VLVf4kCRkvl2xp2D71sTPYns-exsHQHTy3G-zJRK8g",
+	"type":"public-key",
+	"authenticatorAttachment":"platform",
+	"clientExtensionResults":{
+		"appid":true
+	},
+	"response":{
+		"attestationObject":"o2NmbXRkbm9uZWdhdHRTdG10oGhhdXRoRGF0YVjEdKbqkhPJnC90siSSsyDPQCYqlMGpUKA5fyklC2CEHvBBAAAAAAAAAAAAAAAAAAAAAAAAAAAAQOsa7QYSUFukFOLTmgeK6x2ktirNMgwy_6vIwwtegxI2flS1X-JAkZL5dsadg-9bEz2J7PnsbB0B08txvsyUSvKlAQIDJiABIVggLKF5xS0_BntttUIrm2Z2tgZ4uQDwllbdIfrrBMABCNciWCDHwin8Zdkr56iSIh0MrB5qZiEzYLQpEOREhMUkY6q4Vw",
+		"clientDataJSON":"eyJjaGFsbGVuZ2UiOiJXOEd6RlU4cEdqaG9SYldyTERsYW1BZnFfeTRTMUNaRzFWdW9lUkxBUnJFIiwib3JpZ2luIjoiaHR0cHM6Ly93ZWJhdXRobi5pbyIsInR5cGUiOiJ3ZWJhdXRobi5jcmVhdGUifQ",
+		"transports":["usb","nfc","fake"]
+	}
+}
+
+abc
 `,
 	`successDeprecatedTransports`: `
 {

protocol/func_test.go

@@ -0,0 +1,19 @@
+package protocol
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func AssertIsProtocolError(t *testing.T, err error, errType, errDetails, errInfo string) {
+	var e *Error
+
+	require.True(t, errors.As(err, &e))
+
+	assert.Equal(t, errType, e.Type)
+	assert.Equal(t, errDetails, e.Details)
+	assert.Equal(t, errInfo, e.DevInfo)
+}