support for user agents

15 files changed, 337 insertions, 71 deletions

diff --git a/rpc/api/admin.go b/rpc/api/admin.go
index 29f342ab6..5e392ae32 100644
--- a/rpc/api/admin.go
+++ b/rpc/api/admin.go
@@ -37,6 +37,7 @@ import (
 	"github.com/ethereum/go-ethereum/rpc/codec"
 	"github.com/ethereum/go-ethereum/rpc/comms"
 	"github.com/ethereum/go-ethereum/rpc/shared"
+	"github.com/ethereum/go-ethereum/rpc/useragent"
 	"github.com/ethereum/go-ethereum/xeth"
 )
 
@@ -71,6 +72,7 @@ var (
 		"admin_httpGet":            (*adminApi).HttpGet,
 		"admin_sleepBlocks":        (*adminApi).SleepBlocks,
 		"admin_sleep":              (*adminApi).Sleep,
+		"admin_enableUserAgent":    (*adminApi).EnableUserAgent,
 	}
 )
 
@@ -474,3 +476,10 @@ func (self *adminApi) HttpGet(req *shared.Request) (interface{}, error) {
 
 	return string(resp), nil
 }
+
+func (self *adminApi) EnableUserAgent(req *shared.Request) (interface{}, error) {
+	if fe, ok := self.xeth.Frontend().(*useragent.RemoteFrontend); ok {
+		fe.Enable()
+	}
+	return true, nil
+}
diff --git a/rpc/api/net.go b/rpc/api/net.go
index 39c230e14..9c6369615 100644
--- a/rpc/api/net.go
+++ b/rpc/api/net.go
@@ -32,7 +32,7 @@ var (
 	netMapping = map[string]nethandler{
 		"net_peerCount": (*netApi).PeerCount,
 		"net_listening": (*netApi).IsListening,
-		"net_version": (*netApi).Version,
+		"net_version":   (*netApi).Version,
 	}
 )
 
@@ -97,4 +97,3 @@ func (self *netApi) IsListening(req *shared.Request) (interface{}, error) {
 func (self *netApi) Version(req *shared.Request) (interface{}, error) {
 	return self.xeth.NetworkVersion(), nil
 }
-
diff --git a/rpc/api/personal.go b/rpc/api/personal.go
index e9942c1e5..6c73ac83d 100644
--- a/rpc/api/personal.go
+++ b/rpc/api/personal.go
@@ -17,6 +17,7 @@
 package api
 
 import (
+	"fmt"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -125,18 +126,17 @@ func (self *personalApi) UnlockAccount(req *shared.Request) (interface{}, error)
 		return nil, shared.NewDecodeParamError(err.Error())
 	}
 
-	var err error
+	if len(args.Passphrase) == 0 {
+		fe := self.xeth.Frontend()
+		if fe == nil {
+			return false, fmt.Errorf("No password provided")
+		}
+		return fe.UnlockAccount(common.HexToAddress(args.Address).Bytes()), nil
+	}
+
 	am := self.ethereum.AccountManager()
 	addr := common.HexToAddress(args.Address)
 
-	if args.Duration == -1 {
-		err = am.Unlock(addr, args.Passphrase)
-	} else {
-		err = am.TimedUnlock(addr, args.Passphrase, time.Duration(args.Duration)*time.Second)
-	}
-
-	if err == nil {
-		return true, nil
-	}
-	return false, err
+	err := am.TimedUnlock(addr, args.Passphrase, time.Duration(args.Duration)*time.Second)
+	return err == nil, err
 }
diff --git a/rpc/api/personal_args.go b/rpc/api/personal_args.go
index 7f00701e3..5a584fb0c 100644
--- a/rpc/api/personal_args.go
+++ b/rpc/api/personal_args.go
@@ -86,10 +86,10 @@ func (args *UnlockAccountArgs) UnmarshalJSON(b []byte) (err error) {
 		return shared.NewDecodeParamError(err.Error())
 	}
 
-	args.Duration = -1
+	args.Duration = 0
 
-	if len(obj) < 2 {
-		return shared.NewInsufficientParamsError(len(obj), 2)
+	if len(obj) < 1 {
+		return shared.NewInsufficientParamsError(len(obj), 1)
 	}
 
 	if addrstr, ok := obj[0].(string); ok {
@@ -98,10 +98,18 @@ func (args *UnlockAccountArgs) UnmarshalJSON(b []byte) (err error) {
 		return shared.NewInvalidTypeError("address", "not a string")
 	}
 
-	if passphrasestr, ok := obj[1].(string); ok {
-		args.Passphrase = passphrasestr
-	} else {
-		return shared.NewInvalidTypeError("passphrase", "not a string")
+	if len(obj) >= 2 && obj[1] != nil {
+		if passphrasestr, ok := obj[1].(string); ok {
+			args.Passphrase = passphrasestr
+		} else {
+			return shared.NewInvalidTypeError("passphrase", "not a string")
+		}
+	}
+
+	if len(obj) >= 3 && obj[2] != nil {
+		if duration, ok := obj[2].(float64); ok {
+			args.Duration = int(duration)
+		}
 	}
 
 	return nil
diff --git a/rpc/api/ssh_js.go b/rpc/api/shh_js.go
index a92ad1644..a92ad1644 100644
--- a/rpc/api/ssh_js.go
+++ b/rpc/api/shh_js.go
diff --git a/rpc/codec/codec.go b/rpc/codec/codec.go
index 2fdb0d8f3..786080b44 100644
--- a/rpc/codec/codec.go
+++ b/rpc/codec/codec.go
@@ -31,6 +31,8 @@ type ApiCoder interface {
 	ReadRequest() ([]*shared.Request, bool, error)
 	// Parse response message from underlying stream
 	ReadResponse() (interface{}, error)
+	// Read raw message from underlying stream
+	Recv() (interface{}, error)
 	// Encode response to encoded form in underlying stream
 	WriteResponse(interface{}) error
 	// Decode single message from data
diff --git a/rpc/codec/json.go b/rpc/codec/json.go
index d811b2096..cfc449143 100644
--- a/rpc/codec/json.go
+++ b/rpc/codec/json.go
@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"net"
 	"time"
+	"strings"
 
 	"github.com/ethereum/go-ethereum/rpc/shared"
 )
@@ -73,35 +74,41 @@ func (self *JsonCodec) ReadRequest() (requests []*shared.Request, isBatch bool,
 	return nil, false, err
 }
 
-func (self *JsonCodec) ReadResponse() (interface{}, error) {
-	bytesInBuffer := 0
-	buf := make([]byte, MAX_RESPONSE_SIZE)
+func (self *JsonCodec) Recv() (interface{}, error) {
+	var msg json.RawMessage
+	err := self.d.Decode(&msg)
+	if err != nil {
+		self.c.Close()
+		return nil, err
+	}
 
-	deadline := time.Now().Add(READ_TIMEOUT * time.Second)
-	if err := self.c.SetDeadline(deadline); err != nil {
+	return msg, err
+}
+
+func (self *JsonCodec) ReadResponse() (interface{}, error) {
+	in, err := self.Recv()
+	if err != nil {
 		return nil, err
 	}
 
-	for {
-		n, err := self.c.Read(buf[bytesInBuffer:])
-		if err != nil {
-			return nil, err
+	if msg, ok := in.(json.RawMessage); ok {
+		var req *shared.Request
+		if err = json.Unmarshal(msg, &req); err == nil && strings.HasPrefix(req.Method, "agent_") {
+			return req, nil
 		}
-		bytesInBuffer += n
 
-		var failure shared.ErrorResponse
-		if err = json.Unmarshal(buf[:bytesInBuffer], &failure); err == nil && failure.Error != nil {
+		var failure *shared.ErrorResponse
+		if err = json.Unmarshal(msg, &failure); err == nil && failure.Error != nil {
 			return failure, fmt.Errorf(failure.Error.Message)
 		}
 
-		var success shared.SuccessResponse
-		if err = json.Unmarshal(buf[:bytesInBuffer], &success); err == nil {
+		var success *shared.SuccessResponse
+		if err = json.Unmarshal(msg, &success); err == nil {
 			return success, nil
 		}
 	}
 
-	self.c.Close()
-	return nil, fmt.Errorf("Unable to read response")
+	return in, err
 }
 
 // Decode data
diff --git a/rpc/comms/comms.go b/rpc/comms/comms.go
index f5eeae84f..731b2f62e 100644
--- a/rpc/comms/comms.go
+++ b/rpc/comms/comms.go
@@ -49,7 +49,7 @@ var (
 )
 
 type EthereumClient interface {
-	// Close underlaying connection
+	// Close underlying connection
 	Close()
 	// Send request
 	Send(interface{}) error
diff --git a/rpc/comms/inproc.go b/rpc/comms/inproc.go
index f279f0163..e8058e32b 100644
--- a/rpc/comms/inproc.go
+++ b/rpc/comms/inproc.go
@@ -60,7 +60,7 @@ func (self *InProcClient) Send(req interface{}) error {
 }
 
 func (self *InProcClient) Recv() (interface{}, error) {
-	return self.lastRes, self.lastErr
+	return *shared.NewRpcResponse(self.lastId, self.lastJsonrpc, self.lastRes, self.lastErr), nil
 }
 
 func (self *InProcClient) SupportedModules() (map[string]string, error) {
diff --git a/rpc/comms/ipc.go b/rpc/comms/ipc.go
index 0250aa01e..e982ada13 100644
--- a/rpc/comms/ipc.go
+++ b/rpc/comms/ipc.go
@@ -44,35 +44,18 @@ func (self *ipcClient) Close() {
 
 func (self *ipcClient) Send(req interface{}) error {
 	var err error
-	if r, ok := req.(*shared.Request); ok {
-		if err = self.coder.WriteResponse(r); err != nil {
-			if _, ok := err.(*net.OpError); ok { // connection lost, retry once
-				if err = self.reconnect(); err == nil {
-					err = self.coder.WriteResponse(r)
-				}
+	if err = self.coder.WriteResponse(req); err != nil {
+		if _, ok := err.(*net.OpError); ok { // connection lost, retry once
+			if err = self.reconnect(); err == nil {
+				err = self.coder.WriteResponse(req)
 			}
 		}
-		return err
 	}
-
-	return fmt.Errorf("Invalid request (%T)", req)
+	return err
 }
 
 func (self *ipcClient) Recv() (interface{}, error) {
-	res, err := self.coder.ReadResponse()
-	if err != nil {
-		return nil, err
-	}
-
-	if r, ok := res.(shared.SuccessResponse); ok {
-		return r.Result, nil
-	}
-
-	if r, ok := res.(shared.ErrorResponse); ok {
-		return r.Error, nil
-	}
-
-	return res, err
+	return self.coder.ReadResponse()
 }
 
 func (self *ipcClient) SupportedModules() (map[string]string, error) {
@@ -91,7 +74,7 @@ func (self *ipcClient) SupportedModules() (map[string]string, error) {
 		return nil, err
 	}
 
-	if sucRes, ok := res.(shared.SuccessResponse); ok {
+	if sucRes, ok := res.(*shared.SuccessResponse); ok {
 		data, _ := json.Marshal(sucRes.Result)
 		modules := make(map[string]string)
 		err = json.Unmarshal(data, &modules)
@@ -109,8 +92,8 @@ func NewIpcClient(cfg IpcConfig, codec codec.Codec) (*ipcClient, error) {
 }
 
 // Start IPC server
-func StartIpc(cfg IpcConfig, codec codec.Codec, offeredApi shared.EthereumApi) error {
-	return startIpc(cfg, codec, offeredApi)
+func StartIpc(cfg IpcConfig, codec codec.Codec, initializer func(conn net.Conn) (shared.EthereumApi, error)) error {
+	return startIpc(cfg, codec, initializer)
 }
 
 func newIpcConnId() int {
diff --git a/rpc/comms/ipc_unix.go b/rpc/comms/ipc_unix.go
index 432bf93b5..6968fa844 100644
--- a/rpc/comms/ipc_unix.go
+++ b/rpc/comms/ipc_unix.go
@@ -48,7 +48,7 @@ func (self *ipcClient) reconnect() error {
 	return err
 }
 
-func startIpc(cfg IpcConfig, codec codec.Codec, api shared.EthereumApi) error {
+func startIpc(cfg IpcConfig, codec codec.Codec, initializer func(conn net.Conn) (shared.EthereumApi, error)) error {
 	os.Remove(cfg.Endpoint) // in case it still exists from a previous run
 
 	l, err := net.Listen("unix", cfg.Endpoint)
@@ -69,6 +69,13 @@ func startIpc(cfg IpcConfig, codec codec.Codec, api shared.EthereumApi) error {
 			id := newIpcConnId()
 			glog.V(logger.Debug).Infof("New IPC connection with id %06d started\n", id)
 
+			api, err := initializer(conn)
+			if err != nil {
+				glog.V(logger.Error).Infof("Unable to initialize IPC connection - %v\n", err)
+				conn.Close()
+				continue
+			}
+
 			go handle(id, conn, api, codec)
 		}
 
diff --git a/rpc/comms/ipc_windows.go b/rpc/comms/ipc_windows.go
index ee49f069b..b2fe2b29d 100644
--- a/rpc/comms/ipc_windows.go
+++ b/rpc/comms/ipc_windows.go
@@ -667,7 +667,7 @@ func (self *ipcClient) reconnect() error {
 	return err
 }
 
-func startIpc(cfg IpcConfig, codec codec.Codec, api shared.EthereumApi) error {
+func startIpc(cfg IpcConfig, codec codec.Codec, initializer func(conn net.Conn) (shared.EthereumApi, error)) error {
 	os.Remove(cfg.Endpoint) // in case it still exists from a previous run
 
 	l, err := Listen(cfg.Endpoint)
@@ -687,6 +687,13 @@ func startIpc(cfg IpcConfig, codec codec.Codec, api shared.EthereumApi) error {
 			id := newIpcConnId()
 			glog.V(logger.Debug).Infof("New IPC connection with id %06d started\n", id)
 
+			api, err := initializer(conn)
+			if err != nil {
+				glog.V(logger.Error).Infof("Unable to initialize IPC connection - %v\n", err)
+				conn.Close()
+				continue
+			}
+
 			go handle(id, conn, api, codec)
 		}
 
diff --git a/rpc/jeth.go b/rpc/jeth.go
index 07add2bad..158bfb64c 100644
--- a/rpc/jeth.go
+++ b/rpc/jeth.go
@@ -18,12 +18,17 @@ package rpc
 
 import (
 	"encoding/json"
-
 	"fmt"
 
+	"github.com/ethereum/go-ethereum/cmd/utils"
 	"github.com/ethereum/go-ethereum/jsre"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
 	"github.com/ethereum/go-ethereum/rpc/comms"
 	"github.com/ethereum/go-ethereum/rpc/shared"
+	"github.com/ethereum/go-ethereum/rpc/useragent"
+	"github.com/ethereum/go-ethereum/xeth"
+
 	"github.com/robertkrimen/otto"
 )
 
@@ -31,10 +36,21 @@ type Jeth struct {
 	ethApi shared.EthereumApi
 	re     *jsre.JSRE
 	client comms.EthereumClient
+	fe     xeth.Frontend
 }
 
-func NewJeth(ethApi shared.EthereumApi, re *jsre.JSRE, client comms.EthereumClient) *Jeth {
-	return &Jeth{ethApi, re, client}
+func NewJeth(ethApi shared.EthereumApi, re *jsre.JSRE, client comms.EthereumClient, fe xeth.Frontend) *Jeth {
+	// enable the jeth as the user agent
+	req := shared.Request{
+		Id:      0,
+		Method:  useragent.EnableUserAgentMethod,
+		Jsonrpc: shared.JsonRpcVersion,
+		Params:  []byte("[]"),
+	}
+	client.Send(&req)
+	client.Recv()
+
+	return &Jeth{ethApi, re, client, fe}
 }
 
 func (self *Jeth) err(call otto.FunctionCall, code int, msg string, id interface{}) (response otto.Value) {
@@ -72,16 +88,34 @@ func (self *Jeth) Send(call otto.FunctionCall) (response otto.Value) {
 		if err != nil {
 			return self.err(call, -32603, err.Error(), req.Id)
 		}
-		respif, err = self.client.Recv()
 
+	recv:
+		respif, err = self.client.Recv()
 		if err != nil {
 			return self.err(call, -32603, err.Error(), req.Id)
 		}
 
+		agentreq, isRequest := respif.(*shared.Request)
+		if isRequest {
+			self.handleRequest(agentreq)
+			goto recv // receive response after agent interaction
+		}
+
+		sucres, isSuccessResponse := respif.(*shared.SuccessResponse)
+		errres, isErrorResponse := respif.(*shared.ErrorResponse)
+		if !isSuccessResponse && !isErrorResponse {
+			return self.err(call, -32603, fmt.Sprintf("Invalid response type (%T)", respif), req.Id)
+		}
+
 		call.Otto.Set("ret_jsonrpc", shared.JsonRpcVersion)
 		call.Otto.Set("ret_id", req.Id)
 
-		res, _ := json.Marshal(respif)
+		var res []byte
+		if isSuccessResponse {
+			res, err = json.Marshal(sucres.Result)
+		} else if isErrorResponse {
+			res, err = json.Marshal(errres.Error)
+		}
 
 		call.Otto.Set("ret_result", string(res))
 		call.Otto.Set("response_idx", i)
@@ -105,3 +139,48 @@ func (self *Jeth) Send(call otto.FunctionCall) (response otto.Value) {
 
 	return
 }
+
+// handleRequest will handle user agent requests by interacting with the user and sending
+// the user response back to the geth service
+func (self *Jeth) handleRequest(req *shared.Request) bool {
+	var err error
+	var args []interface{}
+	if err = json.Unmarshal(req.Params, &args); err != nil {
+		glog.V(logger.Info).Infof("Unable to parse agent request - %v\n", err)
+		return false
+	}
+
+	switch req.Method {
+	case useragent.AskPasswordMethod:
+		return self.askPassword(req.Id, req.Jsonrpc, args)
+	case useragent.ConfirmTransactionMethod:
+		return self.confirmTransaction(req.Id, req.Jsonrpc, args)
+	}
+
+	return false
+}
+
+// askPassword will ask the user to supply the password for a given account
+func (self *Jeth) askPassword(id interface{}, jsonrpc string, args []interface{}) bool {
+	var err error
+	var passwd string
+	if len(args) >= 1 {
+		if account, ok := args[0].(string); ok {
+			fmt.Printf("Unlock account %s\n", account)
+			passwd, err = utils.PromptPassword("Passphrase: ", true)
+		} else {
+			return false
+		}
+	}
+
+	if err = self.client.Send(shared.NewRpcResponse(id, jsonrpc, passwd, err)); err != nil {
+		glog.V(logger.Info).Infof("Unable to send user agent ask password response - %v\n", err)
+	}
+
+	return err == nil
+}
+
+func (self *Jeth) confirmTransaction(id interface{}, jsonrpc string, args []interface{}) bool {
+	// Accept all tx which are send from this console
+	return self.client.Send(shared.NewRpcResponse(id, jsonrpc, true, nil)) == nil
+}
diff --git a/rpc/useragent/agent.go b/rpc/useragent/agent.go
new file mode 100644
index 000000000..df0739e65
--- /dev/null
+++ b/rpc/useragent/agent.go
@@ -0,0 +1,24 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library 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 Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// package user agent provides frontends and agents which can interact with the user
+package useragent
+
+var (
+	AskPasswordMethod        = "agent_askPassword"
+	ConfirmTransactionMethod = "agent_confirmTransaction"
+	EnableUserAgentMethod    = "admin_enableUserAgent"
+)
diff --git a/rpc/useragent/remote_frontend.go b/rpc/useragent/remote_frontend.go
new file mode 100644
index 000000000..0dd4a6049
--- /dev/null
+++ b/rpc/useragent/remote_frontend.go
@@ -0,0 +1,141 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library 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 Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package useragent
+
+import (
+	"encoding/json"
+	"fmt"
+	"net"
+
+	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
+	"github.com/ethereum/go-ethereum/rpc/shared"
+)
+
+// remoteFrontend implements xeth.Frontend and will communicate with an external
+// user agent over a connection
+type RemoteFrontend struct {
+	enabled bool
+	mgr     *accounts.Manager
+	d       *json.Decoder
+	e       *json.Encoder
+	n       int
+}
+
+// NewRemoteFrontend creates a new frontend which will interact with an user agent
+// over the given connection
+func NewRemoteFrontend(conn net.Conn, mgr *accounts.Manager) *RemoteFrontend {
+	return &RemoteFrontend{false, mgr, json.NewDecoder(conn), json.NewEncoder(conn), 0}
+}
+
+// Enable will enable user interaction
+func (fe *RemoteFrontend) Enable() {
+	fe.enabled = true
+}
+
+// UnlockAccount asks the user agent for the user password and tries to unlock the account.
+// It will try 3 attempts before giving up.
+func (fe *RemoteFrontend) UnlockAccount(address []byte) bool {
+	if !fe.enabled {
+		return false
+	}
+
+	err := fe.send(AskPasswordMethod, common.Bytes2Hex(address))
+	if err != nil {
+		glog.V(logger.Error).Infof("Unable to send password request to agent - %v\n", err)
+		return false
+	}
+
+	passwdRes, err := fe.recv()
+	if err != nil {
+		glog.V(logger.Error).Infof("Unable to recv password response from agent - %v\n", err)
+		return false
+	}
+
+	if passwd, ok := passwdRes.Result.(string); ok {
+		err = fe.mgr.Unlock(common.BytesToAddress(address), passwd)
+	}
+
+	if err == nil {
+		return true
+	}
+
+	glog.V(logger.Debug).Infoln("3 invalid account unlock attempts")
+	return false
+}
+
+// ConfirmTransaction asks the user for approval
+func (fe *RemoteFrontend) ConfirmTransaction(tx string) bool {
+	if !fe.enabled {
+		return true // backwards compatibility
+	}
+
+	err := fe.send(ConfirmTransactionMethod, tx)
+	if err != nil {
+		glog.V(logger.Error).Infof("Unable to send tx confirmation request to agent - %v\n", err)
+		return false
+	}
+
+	confirmResponse, err := fe.recv()
+	if err != nil {
+		glog.V(logger.Error).Infof("Unable to recv tx confirmation response from agent - %v\n", err)
+		return false
+	}
+
+	if confirmed, ok := confirmResponse.Result.(bool); ok {
+		return confirmed
+	}
+
+	return false
+}
+
+// send request to the agent
+func (fe *RemoteFrontend) send(method string, params ...interface{}) error {
+	fe.n += 1
+
+	p, err := json.Marshal(params)
+	if err != nil {
+		glog.V(logger.Info).Infof("Unable to send agent request %v\n", err)
+		return err
+	}
+
+	req := shared.Request{
+		Method:  method,
+		Jsonrpc: shared.JsonRpcVersion,
+		Id:      fe.n,
+		Params:  p,
+	}
+
+	return fe.e.Encode(&req)
+}
+
+// recv user response from agent
+func (fe *RemoteFrontend) recv() (*shared.SuccessResponse, error) {
+	var res json.RawMessage
+	if err := fe.d.Decode(&res); err != nil {
+		return nil, err
+	}
+
+	var response shared.SuccessResponse
+	if err := json.Unmarshal(res, &response); err == nil {
+		return &response, nil
+	}
+
+	return nil, fmt.Errorf("Invalid user agent response")
+}