Implement first client command

The client can now talk to the old Perl signer implementation. Running
socat has been documented in README.md. Commonly used I/O code has been
moved to the shared/io.go file.

README.md

@@ -0,0 +1,26 @@
+# CAcert signer in Go
+
+This is a reimplementation of the CAcert signer code from the
+[CommModule directory](https://git.cacert.org/gitweb/?p=cacert-devel.git;a=tree;f=CommModule) of the CAcert software
+in [Go](https://golang.org/). The goal of this effort is to provide a more maintainable version of the software.
+
+## Running the signer and client locally
+
+The signer is usually attached to a USB serial port. You can run the signer and client locally using the
+[socat](https://manpages.debian.org/buster/socat/socat.1.en.html) utility.
+
+```shell script
+socat -d -d PTY,link=$(pwd)/ttyS0 PTY,link=$(pwd)/ttyS1
+```
+
+You may then run the server
+
+```shell script
+go run signer/main.go -a $(pwd)/dev/ttyS0
+```
+
+and the client:
+
+```shell script
+go run client/main.go -a $(pwd)/dev/ttyS1
+```

client/main.go

@@ -1,71 +1,132 @@
 package main
 
 import (
+	"encoding/binary"
+	"errors"
 	"flag"
+	"fmt"
 	"git.cacert.org/cacert-gosigner/datastructures"
 	"git.cacert.org/cacert-gosigner/shared"
-	"log"
+	"io/ioutil"
 	"time"
 
 	"github.com/goburrow/serial"
+	log "github.com/sirupsen/logrus"
+	"gopkg.in/yaml.v2"
 )
 
-var (
+type SerialConfig struct {
-	address  string
+	Address  string `yaml:"address"`
-	baudrate int
+	BaudRate int    `yaml:"baudrate"`
-	databits int
+	DataBits int    `yaml:"databits"`
-	stopbits int
+	StopBits int    `yaml:"stopbits"`
-	parity   string
+	Parity   string `yaml:"parity"`
-	message  string
+}
-)
+
+type ClientConfig struct {
+	Serial        SerialConfig `yaml:"serial_config"`
+	Paranoid      bool         `yaml:"paranoid"`
+	Debug         bool         `yaml:"debug"`
+	GNUPGBinary   string       `yaml:"gnupg_bin"`
+	OpenSSLBinary string       `yaml:"openssl_bin"`
+	MySQLDSN      string       `yaml:"mysql_dsn"`
+}
+
+var defaultConfig = ClientConfig{
+	Serial: SerialConfig{
+		Address:  "/dev/ttyUSB0",
+		BaudRate: 115200,
+		DataBits: 8,
+		StopBits: 1,
+		Parity:   "N",
+	},
+	Paranoid:      false,
+	Debug:         false,
+	OpenSSLBinary: "/usr/bin/openssl",
+	GNUPGBinary:   "/usr/bin/gpg",
+	MySQLDSN:      "<username>:<password>@/database?parseTime=true",
+}
+
+const HandshakeByte = 0x02
+const AckByte = 0x10
+const NackByte = 0x11
+
+func readConfig(configFile string) (config *ClientConfig, err error) {
+	source, err := ioutil.ReadFile(configFile)
+	if err != nil {
+		log.Errorf("opening configuration file failed: %v", err)
+		if exampleConfig, err := generateExampleConfig(configFile); err != nil {
+			return nil, err
+		} else {
+			log.Info("starting with default config")
+			return exampleConfig, nil
+		}
+	}
+	if err := yaml.Unmarshal(source, &config); err != nil {
+		return nil, fmt.Errorf("loading configuration file failed: %v", err)
+	}
+
+	return config, nil
+}
+
+func generateExampleConfig(configFile string) (config *ClientConfig, err error) {
+	config = &defaultConfig
+	configBytes, err := yaml.Marshal(config)
+	if err != nil {
+		log.Errorf("could not generate configuration data")
+		return
+	}
+
+	log.Infof("example data for %s:\n\n---\n%s\n", configFile, configBytes)
+	return
+}
 
 func main() {
-	flag.StringVar(&address, "a", "/dev/ttyUSB0", "address")
+	var configFile string
-	flag.IntVar(&baudrate, "b", 115200, "baud rate")
+
-	flag.IntVar(&databits, "d", 8, "data bits")
+	flag.StringVar(&configFile, "c", "client.yaml", "client configuration file in YAML format")
-	flag.IntVar(&stopbits, "s", 1, "stop bits")
-	flag.StringVar(&parity, "p", "N", "parity (N/E/O)")
-	flag.StringVar(&message, "m", "serial", "message")
 	flag.Parse()
 
-	config := serial.Config{
+	var clientConfig *ClientConfig
-		Address:  address,
+	var serialConfig *serial.Config
-		BaudRate: baudrate,
+	var err error
-		DataBits: databits,
+
-		StopBits: stopbits,
+	if clientConfig, err = readConfig(configFile); err != nil {
-		Parity:   parity,
+		log.Panic(err)
+	}
+	serialConfig = &serial.Config{
+		Address:  clientConfig.Serial.Address,
+		BaudRate: clientConfig.Serial.BaudRate,
+		DataBits: clientConfig.Serial.DataBits,
+		StopBits: clientConfig.Serial.StopBits,
+		Parity:   clientConfig.Serial.Parity,
 		Timeout:  30 * time.Second,
 	}
-	log.Printf("connecting %+v", config)
+	if clientConfig.Debug {
-	port, err := serial.Open(&config)
+		log.SetLevel(log.DebugLevel)
+	}
+
+	log.Debugf("connecting %+v", serialConfig)
+	port, err := serial.Open(serialConfig)
 	if err != nil {
 		log.Fatal(err)
 	}
-	log.Println("connected")
+	log.Debug("connected")
 	defer func() {
 		err := port.Close()
 		if err != nil {
 			log.Fatal(err)
 		}
-		log.Println("closed")
+		log.Debug("closed")
 	}()
 
-	if _, err = port.Write([]byte{0x02}); err != nil {
-		log.Fatal(err)
-	}
-
-	resp := make([]byte, 1)
-	if _, err = port.Read(resp); err != nil {
-		log.Fatal(err)
-	}
-
 	request := datastructures.NewNulRequest()
 	timeout := time.After(2700 * time.Millisecond)
 	errorChannel := make(chan error, 1)
 	responseChannel := make(chan *datastructures.SignerResponse, 1)
 
 	go func() {
-		if response, err := SendRequest(&port, request); err != nil {
+		if response, err := SendRequest(port, request); err != nil {
 			errorChannel <- err
 		} else {
 			responseChannel <- response
@@ -82,25 +143,128 @@ func main() {
 			log.Fatal(err)
 		}
 	}
-	requestBytes := request.Serialize()
-
-	if _, err = port.Write(requestBytes); err != nil {
-		log.Fatal(err)
-	}
-
-	if _, err = port.Write([]byte{datastructures.CalculateXorCheckSum([][]byte{requestBytes})}); err != nil {
-		log.Fatal(err)
-	}
-
-	if _, err = port.Write([]byte(shared.MagicTrailer)); err != nil {
-		log.Fatal(err)
-	}
 }
 
 func Process(response *datastructures.SignerResponse) error {
+	log.Debugf("process %v", response)
 	return nil
 }
 
-func SendRequest(port *serial.Port, request *datastructures.SignerRequest) (*datastructures.SignerResponse, error) {
+func sendHandShake(port serial.Port) error {
+	log.Debug("Shaking hands ...")
+	if length, err := port.Write([]byte{HandshakeByte}); err != nil {
+		return fmt.Errorf("could not write handshake byte: %v", err)
+	} else {
+		log.Debugf("wrote %d handshake bytes", length)
+	}
+	handShakeResponse := make([]byte, 1)
+	if length, err := port.Read(handShakeResponse); err != nil {
+		return fmt.Errorf("failed to read handshake response: %v", err)
+	} else {
+		log.Debugf("read %d bytes", length)
+	}
+	if handShakeResponse[0] != AckByte {
+		return fmt.Errorf("invalid handshake response expected 0x10 received %x", handShakeResponse[0])
+	}
+	log.Debug("Handshake successful")
+	return nil
+}
+
+func receiveResponse(port *serial.Port, responseChan *chan []byte, errorChan *chan error) {
+	header, err := shared.ReceiveBytes(port, 1, 20)
+	if err != nil {
+		*errorChan <- err
+		return
+	}
+	if header[0] != HandshakeByte {
+		*errorChan <- fmt.Errorf("unexpected byte 0x%x expected 0x%x", header, HandshakeByte)
+	}
+
+	if _, err := (*port).Write([]byte{AckByte}); err != nil {
+		*errorChan <- errors.New("could not write ACK")
+		return
+	}
+
+	lengthBytes, err := shared.ReceiveBytes(port, 3, 2)
+	if err != nil {
+		*errorChan <- err
+		return
+	}
+	blockLength := binary.BigEndian.Uint32([]byte{0x0, lengthBytes[0], lengthBytes[1], lengthBytes[2]})
+	blockData, err := shared.ReceiveBytes(port, int(blockLength), 5)
+	if err != nil {
+		*errorChan <- err
+		return
+	}
+
+	checkSum, err := shared.ReceiveBytes(port, 1, 2)
+	if err != nil {
+		*errorChan <- err
+		return
+	}
+	log.Debugf("block checksum is %d", checkSum)
+	trailer, err := shared.ReceiveBytes(port, len(shared.MagicTrailer), 2)
+	if err != nil {
+		*errorChan <- err
+		return
+	}
+	if string(trailer) != shared.MagicTrailer {
+		*errorChan <- errors.New("expected trailer bytes not found")
+		return
+	}
+
+	if _, err := (*port).Write([]byte{AckByte}); err != nil {
+		*errorChan <- fmt.Errorf("could not write ACK byte: %v", err)
+	}
+	*responseChan <- blockData
+
+	return
+}
+
+func SendRequest(port serial.Port, request *datastructures.SignerRequest) (response *datastructures.SignerResponse, err error) {
+	log.Debugf("send request %v to serial port %v", request, port)
+
+	if err = sendHandShake(port); err != nil {
+		return nil, err
+	}
+
+	requestBytes := request.Serialize()
+	if length, err := port.Write(requestBytes); err != nil {
+		log.Fatal(err)
+	} else {
+		log.Debugf("wrote %d request bytes", length)
+	}
+
+	if length, err := port.Write([]byte{datastructures.CalculateXorCheckSum([][]byte{requestBytes})}); err != nil {
+		log.Fatal(err)
+	} else {
+		log.Debugf("wrote %d checksum bytes", length)
+	}
+
+	if length, err := port.Write([]byte(shared.MagicTrailer)); err != nil {
+		log.Fatal(err)
+	} else {
+		log.Debugf("wrote %d trailer bytes", length)
+	}
+
+	header, err := shared.ReceiveBytes(&port, 1, 20)
+	if err != nil {
+		return nil, err
+	}
+	if header[0] != AckByte {
+		return nil, fmt.Errorf("unexpected byte 0x%x expected 0x%x", header, AckByte)
+	}
+
+	responseChan := make(chan []byte, 1)
+	errChan := make(chan error, 1)
+	go receiveResponse(&port, &responseChan, &errChan)
+
+	select {
+	case responseData := <-responseChan:
+		log.Debugf("response data: %v", responseData)
+	case err := <-errChan:
+		log.Errorf("%v", err)
+	}
+
 	return nil, nil
 }

datastructures/signerrequest.go

@@ -22,6 +22,8 @@ type SignerRequest struct {
 	Content3      string
 }
 
+const protocolVersion = 1
+
 func SignerRequestFromData(lengthBytes []byte, blockData []byte, checkSum byte) (*SignerRequest, error) {
 	headerLength := decode24BitLength(blockData[0:3])
 	headerBytes := blockData[3 : 3+headerLength]
@@ -76,5 +78,9 @@ func (r SignerRequest) Serialize() []byte {
 }
 
 func NewNulRequest() *SignerRequest {
-	return &SignerRequest{Version: 1, Action: ActionNul, Content1: time.Now().UTC().Format("010203042006.05")}
+	return &SignerRequest{
+		Version: protocolVersion,
+		Action:  ActionNul,
+		Content1: time.Now().UTC().Format("010203042006.05"),
+	}
 }

shared/io.go

@@ -0,0 +1,31 @@
+package shared
+
+import (
+	"errors"
+	"github.com/goburrow/serial"
+	"io"
+	"time"
+)
+
+// receive the requested number of bytes from serial port and stop after the given timeout in seconds
+func ReceiveBytes(port *serial.Port, count int, timeout time.Duration) ([]byte, error) {
+	timeoutCh := time.After(timeout * time.Second)
+	readCh := make(chan []byte, 1)
+	errCh := make(chan error, 1)
+	go func() {
+		data := make([]byte, count)
+		if _, err := io.ReadAtLeast(*port, data, count); err != nil {
+			errCh <- err
+		} else {
+			readCh <- data
+		}
+	}()
+	select {
+	case <-timeoutCh:
+		return nil, errors.New("timeout")
+	case err := <-errCh:
+		return nil, err
+	case data := <-readCh:
+		return data, nil
+	}
+}

shared/shared.go

@@ -1,4 +1,3 @@
 package shared
 
 const MagicTrailer = "rie4Ech7"
-

signer/main.go

@@ -7,7 +7,6 @@ import (
 	"fmt"
 	"git.cacert.org/cacert-gosigner/datastructures"
 	"git.cacert.org/cacert-gosigner/shared"
-	"io"
 	"log"
 	"time"
 
@@ -70,7 +69,7 @@ readLoop:
 			if err != nil {
 				log.Printf("ERROR %v\n", err)
 			} else {
-				SendResponse(&port, response)
+				_ = SendResponse(&port, response)
 			}
 		case <-timeout:
 			log.Println("timeout in main loop")
@@ -90,7 +89,7 @@ func SendResponse(port *serial.Port, response *datastructures.SignerResponse) er
 		return err
 	}
 
-	if ack, err := receiveBytes(port, 1, 5); err != nil {
+	if ack, err := shared.ReceiveBytes(port, 1, 5); err != nil {
 		return err
 	} else if ack[0] != 0x10 {
 		return errors.New(fmt.Sprintf("invalid ack byte 0x%02x", ack[0]))
@@ -112,7 +111,7 @@ func SendResponse(port *serial.Port, response *datastructures.SignerResponse) er
 			return err
 		}
 
-		if ack, err := receiveBytes(port, 1, 5); err != nil {
+		if ack, err := shared.ReceiveBytes(port, 1, 5); err != nil {
 			return err
 		} else if ack[0] == 0x10 {
 			tryAgain = false
@@ -146,13 +145,13 @@ func handleNulAction(command datastructures.SignerRequest) (*datastructures.Sign
 
 // Receive a request and generate a request data structure
 func Receive(port *serial.Port, commandChan *chan datastructures.SignerRequest, errorChan *chan error) {
-	header, err := receiveBytes(port, 1, 20)
+	header, err := shared.ReceiveBytes(port, 1, 20)
 	if err != nil {
 		*errorChan <- err
 		return
 	}
 	if header[0] != 0x02 {
-		*errorChan <- errors.New(fmt.Sprintf("unexpected byte 0x%x expected 0x02", header))
+		*errorChan <- fmt.Errorf("unexpected byte 0x%x expected 0x02", header)
 	}
 
 	if _, err := (*port).Write([]byte{0x10}); err != nil {
@@ -160,19 +159,19 @@ func Receive(port *serial.Port, commandChan *chan datastructures.SignerRequest,
 		return
 	}
 
-	lengthBytes, err := receiveBytes(port, 3, 2)
+	lengthBytes, err := shared.ReceiveBytes(port, 3, 2)
 	if err != nil {
 		*errorChan <- err
 		return
 	}
 	blockLength := binary.BigEndian.Uint32([]byte{0x0, lengthBytes[0], lengthBytes[1], lengthBytes[2]})
-	blockData, err := receiveBytes(port, int(blockLength), 5)
+	blockData, err := shared.ReceiveBytes(port, int(blockLength), 5)
 	if err != nil {
 		*errorChan <- err
 		return
 	}
 
-	checkSum, err := receiveBytes(port, 1, 2)
+	checkSum, err := shared.ReceiveBytes(port, 1, 2)
 	if err != nil {
 		*errorChan <- err
 		return
@@ -183,7 +182,7 @@ func Receive(port *serial.Port, commandChan *chan datastructures.SignerRequest,
 		*errorChan <- err
 	}
 
-	trailer, err := receiveBytes(port, len(shared.MagicTrailer), 2)
+	trailer, err := shared.ReceiveBytes(port, len(shared.MagicTrailer), 2)
 	if err != nil {
 		*errorChan <- err
 		return
@@ -201,25 +200,3 @@ func Receive(port *serial.Port, commandChan *chan datastructures.SignerRequest,
 	*commandChan <- *command
 }
 
-// receive the requested number of bytes from serial port and stop after the given timeout in seconds
-func receiveBytes(port *serial.Port, count int, timeout time.Duration) ([]byte, error) {
-	timeoutCh := time.After(timeout * time.Second)
-	readCh := make(chan []byte, 1)
-	errCh := make(chan error, 1)
-	go func() {
-		data := make([]byte, count)
-		if _, err := io.ReadAtLeast(*port, data, count); err != nil {
-			errCh <- err
-		} else {
-			readCh <- data
-		}
-	}()
-	select {
-	case <-timeoutCh:
-		return nil, errors.New("timeout")
-	case err := <-errCh:
-		return nil, err
-	case data := <-readCh:
-		return data, nil
-	}
-}