From 978f1f3f6d44d1e71c85b5ea2ac13e80cde773bb Mon Sep 17 00:00:00 2001
From: Dmitry Yu Okunev
Date: Mon, 25 Jun 2018 23:52:55 +0200
Subject: Implemented the support of Trezor devices.

---
 internal/readpassword/trezor.go | 84 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 75 insertions(+), 9 deletions(-)

diff --git a/internal/readpassword/trezor.go b/internal/readpassword/trezor.go
index 45edfd8..be9c22a 100644
--- a/internal/readpassword/trezor.go
+++ b/internal/readpassword/trezor.go
@@ -5,31 +5,97 @@ import (
 
 	"github.com/rfjakob/gocryptfs/internal/exitcodes"
 	"github.com/rfjakob/gocryptfs/internal/tlog"
+
+	"github.com/xaionaro-go/cryptoWallet"
+	"github.com/xaionaro-go/cryptoWallet/vendors"
 )
 
 const (
 	// TrezorPayloadLen is the length of the payload data passed to Trezor's
 	// CipherKeyValue function.
-	TrezorPayloadLen = 32
+	TrezorPayloadLen        = 32
+	trezorNonce             = "" // the "nonce" is optional and has no use in here
+	trezorKeyName           = "gocryptfs"
+	trezorKeyDerivationPath = `m/10019'/0'`
 )
 
-// Trezor reads 16 deterministically derived bytes from a
+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(payload []byte) []byte {
 	if len(payload) != TrezorPayloadLen {
 		tlog.Fatal.Printf("Invalid TrezorPayload length: wanted %d, got %d bytes\n", TrezorPayloadLen, len(payload))
 		os.Exit(exitcodes.LoadConf)
 	}
-	var err error
-	// TODO try to read bytes here....
-	// Handle errors
+
+	// Find all trezor devices
+	trezors := cryptoWallet.Find(cryptoWallet.Filter{
+		VendorID:   &[]uint16{vendors.GetVendorID("satoshilabs")}[0],
+		ProductIDs: []uint16{1 /* Trezor One */},
+	})
+
+	// ATM, we require to one and only one trezor device to be connected.
+	// The support of multiple trezor devices is not implemented, yet.
+	if len(trezors) == 0 {
+		tlog.Fatal.Printf("Trezor device is not found. Check the connection.")
+		os.Exit(exitcodes.TrezorError)
+	}
+	if len(trezors) > 1 {
+		tlog.Fatal.Printf("It's more than one Trezor device connected. This case is not implemented, yet. The number of currently connected devices: %v.", len(trezors))
+		os.Exit(exitcodes.TrezorError)
+	}
+
+	// Using the first found device
+	trezor := trezors[0]
+
+	// 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 reset the state of the device and check if it's initialized.
+	// If device is not initialized then trezor.Reset() will return an
+	// error.
+	err := trezor.Reset()
 	if err != nil {
-		tlog.Fatal.Printf("xxx some error was encountered...")
+		tlog.Fatal.Printf("Cannot reset the Trezor device. Error: %v", err.Error())
 		os.Exit(exitcodes.TrezorError)
 	}
-	tlog.Warn.Println("XXX readpassword.Trezor(): not implemented yet - returning hardcoded dummy bytes XXX")
-	return []byte("1234567890123456")
+
+	// To generate a deterministic 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" payload;
+	// * the nonce;
+	// * the key name.
+	key, err := trezor.DecryptKey(trezorKeyDerivationPath, payload, []byte(trezorNonce), trezorKeyName)
+	if err != nil {
+		tlog.Fatal.Printf("Cannot get the key from the Trezor device. Error description:\n\t%v", err.Error())
+		os.Exit(exitcodes.TrezorError)
+	}
+
+	// Everything ok
+	return key
 }
-- 
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