a bunch of updates, including verify function

Signed-off-by: Dave Henderson <dhenderson@gmail.com>

cmd/image.go

@@ -3,6 +3,9 @@ package cmd
 import (
 	"context"
 	"fmt"
+	"os"
+
+	"github.com/pkg/errors"
 
 	"github.com/hairyhenderson/go-onerng"
 	"github.com/spf13/cobra"
@@ -10,17 +13,34 @@ import (
 
 // imageCmd represents the image command
 func imageCmd(ctx context.Context) *cobra.Command {
-	return &cobra.Command{
+	var imgOut string
+	cmd := &cobra.Command{
 		Use:   "image",
 		Short: "Dump the OneRNG's firmware image",
 		RunE: func(cmd *cobra.Command, args []string) error {
 			o := onerng.OneRNG{Path: opts.Device}
+			err := o.Init(ctx)
+			if err != nil {
+				return errors.Wrapf(err, "init failed before image extraction")
+			}
 			image, err := o.Image(ctx)
 			if err != nil {
 				return err
 			}
-			fmt.Printf("%q\n", image)
-			return nil
+			var out *os.File
+			if imgOut == "-" {
+				out = os.Stdout
+			} else {
+				out, err = os.OpenFile(imgOut, os.O_RDWR|os.O_CREATE, 0644)
+				if err != nil {
+					return err
+				}
+			}
+			n, err := out.Write(image)
+			fmt.Fprintf(os.Stderr, "Wrote %db to %s\n", n, imgOut)
+			return err
 		},
 	}
+	cmd.Flags().StringVarP(&imgOut, "out", "o", "onerng.img", "output file for image (use - for stdout)")
+	return cmd
 }

cmd/init.go

@@ -0,0 +1,21 @@
+package cmd
+
+import (
+	"context"
+
+	"github.com/hairyhenderson/go-onerng"
+	"github.com/spf13/cobra"
+)
+
+// initCmd represents the init command
+func initCmd(ctx context.Context) *cobra.Command {
+	return &cobra.Command{
+		Use:   "init",
+		Short: "Initialize the RNG",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			o := onerng.OneRNG{Path: opts.Device}
+			err := o.Init(ctx)
+			return err
+		},
+	}
+}

cmd/root.go

@@ -51,6 +51,7 @@ func initConfig(ctx context.Context, cmd *cobra.Command) {
 		idCmd(ctx),
 		flushCmd(ctx),
 		imageCmd(ctx),
+		initCmd(ctx),
 	)
 
 	if cfgFile != "" { // enable ability to specify config file via flag
@@ -63,7 +64,7 @@ func initConfig(ctx context.Context, cmd *cobra.Command) {
 
 	// If a config file is found, read it in.
 	if err := viper.ReadInConfig(); err == nil {
-		fmt.Println("Using config file:", viper.ConfigFileUsed())
+		fmt.Fprintln(os.Stderr, "Using config file:", viper.ConfigFileUsed())
 	}
 }
 

cmd/verify.go

@@ -1,8 +1,12 @@
 package cmd
 
 import (
+	"bytes"
 	"context"
 
+	"github.com/pkg/errors"
+
+	"github.com/hairyhenderson/go-onerng"
 	"github.com/spf13/cobra"
 )
 
@@ -78,7 +82,17 @@ func verifyCmd(ctx context.Context) *cobra.Command {
 		Use:   "verify",
 		Short: "Verify that OneRNG's firmware has not been tampered with.",
 		RunE: func(cmd *cobra.Command, args []string) error {
-			return nil
+			o := onerng.OneRNG{Path: opts.Device}
+			err := o.Init(ctx)
+			if err != nil {
+				return errors.Wrapf(err, "init failed before image verification")
+			}
+			image, err := o.Image(ctx)
+			if err != nil {
+				return errors.Wrapf(err, "image extraction failed before verification")
+			}
+			err = onerng.Verify(ctx, bytes.NewBuffer(image), publicKey)
+			return err
 		},
 	}
 }

onerng.go

@@ -3,9 +3,12 @@ package onerng
 import (
 	"bufio"
 	"context"
+	"fmt"
+	"io"
 	"os"
 	"strconv"
 	"strings"
+	"time"
 
 	"github.com/pkg/errors"
 )
@@ -38,22 +41,16 @@ func (o *OneRNG) Version(ctx context.Context) (int, error) {
 	}
 	defer d.Close()
 
+	err = o.cmd(ctx, d, CmdPause)
+	if err != nil {
+		return 0, err
+	}
+
 	_, cancel := context.WithCancel(ctx)
 	defer cancel()
 	buf := make(chan string)
 	errc := make(chan error, 1)
-	go func() {
-		defer close(buf)
-		defer close(errc)
-		scanner := bufio.NewScanner(d)
-		for scanner.Scan() {
-			select {
-			case <-ctx.Done():
-				return
-			case buf <- scanner.Text():
-			}
-		}
-	}()
+	go scan(ctx, d, buf, errc)
 
 	err = o.cmd(ctx, d, CmdSilent, CmdVersion, CmdRun)
 	if err != nil {
@@ -100,18 +97,7 @@ func (o *OneRNG) Identify(ctx context.Context) (string, error) {
 	defer cancel()
 	buf := make(chan string)
 	errc := make(chan error, 1)
-	go func() {
-		defer close(buf)
-		defer close(errc)
-		scanner := bufio.NewScanner(d)
-		for scanner.Scan() {
-			select {
-			case <-ctx.Done():
-				return
-			case buf <- scanner.Text():
-			}
-		}
-	}()
+	go scan(ctx, d, buf, errc)
 
 	err = o.cmd(ctx, d, CmdSilent, CmdID, CmdRun)
 	if err != nil {
@@ -166,30 +152,18 @@ func (o *OneRNG) Image(ctx context.Context) ([]byte, error) {
 	}
 	defer d.Close()
 
+	err = o.cmd(ctx, d, CmdPause, CmdSilent)
+	if err != nil {
+		return nil, err
+	}
+
+	time.Sleep(2 * time.Second)
+
 	_, cancel := context.WithCancel(ctx)
 	defer cancel()
 	buf := make(chan []byte)
 	errc := make(chan error, 1)
-	go func() {
-		defer close(buf)
-		defer close(errc)
-		b := make([]byte, 128)
-		for {
-			n, err := d.Read(b)
-			if err != nil {
-				errc <- err
-				return
-			}
-			select {
-			case <-ctx.Done():
-				return
-			case buf <- b:
-			}
-			if n == 0 {
-				return
-			}
-		}
-	}()
+	go stream(ctx, d, 4, buf, errc)
 
 	err = o.cmd(ctx, d, CmdSilent, CmdImage, CmdRun)
 	if err != nil {
@@ -197,6 +171,7 @@ func (o *OneRNG) Image(ctx context.Context) ([]byte, error) {
 	}
 
 	image := []byte{}
+	zeros := 0
 loop:
 	for {
 		var b []byte
@@ -204,9 +179,16 @@ loop:
 		case <-ctx.Done():
 			return nil, ctx.Err()
 		case b = <-buf:
-			copy(image, b)
-			if len(b) == 0 {
-				break loop
+			image = append(image, b...)
+			for _, v := range b {
+				if v == 0 {
+					zeros++
+				} else {
+					zeros = 0
+				}
+				if zeros > 200 {
+					break loop
+				}
 			}
 		case err := <-errc:
 			return nil, err
@@ -220,3 +202,91 @@ loop:
 
 	return image, err
 }
+
+// Init - wait for the device to finish initializing and start returning data
+func (o *OneRNG) Init(ctx context.Context) error {
+	i := 0
+	for ; i < 200; i++ {
+		n, err := o.readData(ctx)
+		if err != nil {
+			return err
+		}
+		if n > 0 {
+			break
+		}
+	}
+	fmt.Fprintf(os.Stderr, "Initialized after %d loops\n", i)
+	return nil
+}
+
+// readData - try to read some data from the RNG
+func (o *OneRNG) readData(ctx context.Context) (int, error) {
+	d, err := os.OpenFile(o.Path, os.O_RDWR, 0600)
+	if err != nil {
+		return 0, err
+	}
+	defer d.Close()
+
+	_, cancel := context.WithTimeout(ctx, 50*time.Millisecond)
+	defer cancel()
+
+	buf := make(chan []byte)
+	errc := make(chan error, 1)
+	go stream(ctx, d, 1, buf, errc)
+
+	err = o.cmd(ctx, d, CmdAvalanche, CmdRun)
+	if err != nil {
+		return 0, err
+	}
+
+	// make sure we always end with a pause/silence/flush
+	defer o.cmd(ctx, d, CmdPause, CmdSilent, CmdFlush)
+
+	// blocking read from the channel, with a timeout (from context)
+	select {
+	case <-ctx.Done():
+		return 0, ctx.Err()
+	case b := <-buf:
+		return len(b), nil
+	case err := <-errc:
+		return 0, err
+	}
+}
+
+// stream from a file into a channel until an error is encountered, the channel
+// is closed, or the context is cancelled.
+func stream(ctx context.Context, d *os.File, bs int, buf chan []byte, errc chan error) {
+	defer close(buf)
+	defer close(errc)
+	for {
+		b := make([]byte, bs)
+		n, err := io.ReadAtLeast(d, b, len(b))
+		if err != nil {
+			errc <- err
+			return
+		}
+		if n < len(b) {
+			errc <- errors.Errorf("unexpected short read - wanted %db, read %db", len(b), n)
+			return
+		}
+
+		select {
+		case <-ctx.Done():
+			return
+		case buf <- b:
+		}
+	}
+}
+
+func scan(ctx context.Context, d *os.File, buf chan string, errc chan error) {
+	defer close(buf)
+	defer close(errc)
+	scanner := bufio.NewScanner(d)
+	for scanner.Scan() {
+		select {
+		case <-ctx.Done():
+			return
+		case buf <- scanner.Text():
+		}
+	}
+}

verify.go

@@ -0,0 +1,140 @@
+package onerng
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/pkg/errors"
+	"golang.org/x/crypto/openpgp"
+)
+
+//	looks like:
+//		fe ed be ef 20 14	- magic number
+//		00 00 04 		- len (little endian)
+//		00 00			- version (little endian)
+//		image			- len bytes of image
+type fwImage struct {
+	magic   [6]byte      // must be 0xfeedbeef2014
+	length  [3]byte      // LE
+	version [2]byte      // LE
+	_       [1]byte      //
+	fullimg [262144]byte // full image
+	// image   [261536]byte // 256kb minus end offset
+	// slen    [2]byte      // signature length
+	// sig     [543]byte    // signature
+	// endOff  [608]byte
+}
+
+// Verify - this is a more-or-less straight port from the onerng_verify.py script
+// distributed with the OneRNG package
+func Verify(ctx context.Context, image io.Reader, pubkey string) error {
+	var x byte
+	length := 0
+	version := 0
+	state := int8(0)
+	for {
+		c := make([]byte, 1)
+		n, err := io.ReadAtLeast(image, c, len(c))
+		if err != nil {
+			return err
+		}
+		if n == 0 {
+			return errors.Errorf("Short image")
+		}
+		x = c[0]
+
+		// 1. read magic (6 bytes)
+		if state == 0 && x == 0xfe {
+			state++
+		} else if state == 1 && x == 0xed {
+			state++
+		} else if state == 2 && x == 0xbe {
+			state++
+		} else if state == 3 && x == 0xef {
+			state++
+		} else if state == 4 && x == 0x20 {
+			state++
+		} else if state == 5 && x == 0x14 {
+			state++
+			// 2. read length (3 bytes)
+		} else if state == 6 {
+			length = int(x)
+			state++
+		} else if state == 7 {
+			length = length | (int(x) << 8)
+			state++
+		} else if state == 8 {
+			length = length | (int(x) << 16)
+			state++
+			// 3. read version (2 bytes)
+		} else if state == 9 {
+			version = int(x)
+			state++
+		} else if state == 10 {
+			version = version | (int(x) << 8)
+			state++
+		} else if state == 11 {
+			// skip a padding byte I guess...
+			state++
+		} else if state == 12 {
+			// 4. read image
+			c := make([]byte, length)
+			n, err := io.ReadAtLeast(image, c, length)
+			if err != nil {
+				return err
+			}
+			if n != length {
+				return errors.Errorf("Bad image")
+			}
+
+			// determine end offset
+			endOff := 0
+			if version >= 3 {
+				endOff = 680
+			} else {
+				endOff = 600
+			}
+
+			// read length of signature - 2 bytes between image and signature
+			x = c[length-endOff]
+			klen := int(x)
+			x = c[length-endOff+1]
+			klen = klen | (int(x) << 8)
+
+			// split last part into image (signed part) & signature
+			signature := bytes.NewBuffer(c[length-endOff+2 : length-endOff+2+klen])
+			signed := bytes.NewBuffer(c[0 : length-endOff])
+
+			// leftovers := c[length-endOff+2+klen : length]
+			// fmt.Fprintf(os.Stderr, "leftovers (%d):\n%#x\n", len(leftovers), leftovers)
+
+			// read public key
+			keyring, err := openpgp.ReadArmoredKeyRing(bytes.NewBufferString(pubkey))
+			if err != nil {
+				return err
+			}
+
+			// verify
+			signer, err := openpgp.CheckDetachedSignature(keyring, signed, signature)
+			if err != nil {
+				return errors.Wrapf(err, "failed to verify firmware signature")
+			}
+
+			fmt.Fprintf(os.Stderr, "firmware verification passed OK - version=%d\n", version)
+			for _, id := range signer.Identities {
+				fmt.Fprintf(os.Stderr, "signed by: %#v\n", id.Name)
+				fmt.Fprintf(os.Stderr, "\tcreated: %q\n", id.SelfSignature.CreationTime)
+				fmt.Fprintf(os.Stderr, "\tfingerprint: %X\n", signer.PrimaryKey.Fingerprint)
+			}
+
+			break
+		} else {
+			// something didn't line up, so we need to begin again...
+			state = 0
+		}
+	}
+	return nil
+}