Implemented the support of Trezor devices.

Author: xaionaro

internal/readpassword/trezor.go

@@ -5,22 +5,86 @@ import (
 
 	"github.com/rfjakob/gocryptfs/internal/exitcodes"
 	"github.com/rfjakob/gocryptfs/internal/tlog"
+
+	"github.com/xaionaro-go/cryptoWallet"
+	"github.com/xaionaro-go/cryptoWallet/vendors"
 )
 
-// Trezor reads 16 deterministically derived bytes from a
+// It's required initial values to be constant to get the resulting key to
+// be deterministic (see the comment above and within function "Trezor()").
+// This values could be just a bunch of zeros, but it seems to be a little
+// degenerate case that may add risks, so random values were used.
+//
+// This values were generated using command:
+//   dd if=/dev/random of=/dev/stdout bs=48 count=1 2>/dev/null | hexdump -e '8/1 "0x%02x, " "\n"'
+var (
+	TREZOR_DUMMYKEY = []byte{
+		0xfc, 0x3b, 0xe3, 0xa6, 0xe6, 0x61, 0x32, 0xbc,
+		0x95, 0x86, 0x79, 0x06, 0x70, 0xf9, 0x7c, 0x0a,
+		0xab, 0x05, 0x3b, 0x12, 0xff, 0x4e, 0xa8, 0x8b,
+		0x5b, 0x58, 0x0a, 0x8e, 0x42, 0xcf, 0x5e, 0x20,
+	}
+	TREZOR_NONCE = []byte{
+		0xc9, 0xf1, 0x6d, 0xab, 0xba, 0x16, 0x68, 0xc9,
+		0xcc, 0xb6, 0xb2, 0xcd, 0xbc, 0x4a, 0xb6, 0xcb,
+	}
+	TREZOR_KEY_NAME            = "gocryptfs"
+	TREZOR_KEY_DERIVATION_PATH = `m/10019'/0'/0'/0'`
+)
+
+func trezorGetPin(title, description, ok, cancel string) ([]byte, error) {
+	return Once("", title), nil
+}
+func trezorGetConfirm(title, description, ok, cancel string) (bool, error) {
+	return false, nil // do not retry on connection failure
+}
+
+// Trezor reads 32 deterministically derived bytes from a
 // SatoshiLabs Trezor USB security module.
 // The bytes are pseudorandom binary data and may contain null bytes.
-// This function either succeeds and returns 16 bytes or calls os.Exit to end
+// This function either succeeds and returns 32 bytes or calls os.Exit to end
 // the application.
 func Trezor() []byte {
-	var err error
-	// TODO try to read bytes here....
-	// Handle errors
+	trezor := cryptoWallet.Find(cryptoWallet.Filter{
+		VendorId:   &[]uint16{vendors.GetVendorId("satoshilabs")}[0],
+		ProductIds: []uint16{1 /* Trezor One */},
+	})
+
+	if trezor == nil {
+		tlog.Fatal.Printf("Trezor device is not found. Check the connection.")
+		os.Exit(exitcodes.TrezorError)
+	}
+
+	// Trezor may ask for PIN or Passphrase. Setting the handler for this case.
+	trezor.SetGetPinFunc(trezorGetPin)
+
+	// In some cases (like lost connection to the Trezor device and cannot
+	// reconnect) it's required to get a confirmation from the user to
+	// retry to reconnect. Setting the handler for this case.
+	trezor.SetGetConfirmFunc(trezorGetConfirm)
+
+	// To generate a deterministic the key we trying to decrypt our
+	// predefined constant key using the Trezor device. The resulting key
+	// will depend on next variables:
+	// * the Trezor master key;
+	// * the passphrase (passed to the Trezor).
+	//
+	// The right key will be received only if both values (mentioned
+	// above) are correct.
+	//
+	// Note:
+	// Also the resulting key depends on this values (that we defined as
+	// constants above):
+	// * the key derivation path;
+	// * the "encrypted" key;
+	// * the nonce;
+	// * the key name.
+	key, err := trezor.DecryptKey(TREZOR_KEY_DERIVATION_PATH, TREZOR_DUMMYKEY, TREZOR_NONCE, TREZOR_KEY_NAME)
 	if err != nil {
-		tlog.Fatal.Printf("xxx some error was encountered...")
+		tlog.Fatal.Printf("Cannot get the key from the Trezor device. Error description:\n\t%v", err.Error())
 		os.Exit(exitcodes.TrezorError)
 	}
 
-	tlog.Warn.Println("XXX readpassword.Trezor(): not implemented yet - returning hardcoded dummy bytes XXX")
-	return []byte("1234567890123456")
+	// Everything ok
+	return key
 }