detect when trying to sign with a hw wallet offline in a not supported config

closes #4229

plugins/keepkey/plugin.py

@@ -7,7 +7,7 @@ from electrum.bitcoin import (b58_address_to_hash160, xpub_from_pubkey,
 from electrum import constants
 from electrum.i18n import _
 from electrum.plugins import BasePlugin
-from electrum.transaction import deserialize
+from electrum.transaction import deserialize, Transaction
 from electrum.keystore import Hardware_KeyStore, is_xpubkey, parse_xpubkey
 from electrum.base_wizard import ScriptTypeNotSupported
 
@@ -48,6 +48,8 @@ class KeepKeyCompatibleKeyStore(Hardware_KeyStore):
         for txin in tx.inputs():
             pubkeys, x_pubkeys = tx.get_sorted_pubkeys(txin)
             tx_hash = txin['prevout_hash']
+            if txin.get('prev_tx') is None and not Transaction.is_segwit_input(txin):
+                raise Exception(_('Offline signing with {} is not supported for legacy inputs.').format(self.device))
             prev_tx[tx_hash] = txin['prev_tx']
             for x_pubkey in x_pubkeys:
                 if not is_xpubkey(x_pubkey):

plugins/ledger/ledger.py

@@ -350,6 +350,9 @@ class Ledger_KeyStore(Hardware_KeyStore):
                 self.give_error("No matching x_key for sign_transaction") # should never happen
 
             redeemScript = Transaction.get_preimage_script(txin)
+            if txin.get('prev_tx') is None:  # and not Transaction.is_segwit_input(txin):
+                # note: offline signing does not work atm even with segwit inputs for ledger
+                raise Exception(_('Offline signing with {} is not supported.').format(self.device))
             inputs.append([txin['prev_tx'].raw, txin['prevout_n'], redeemScript, txin['prevout_hash'], signingPos, txin.get('sequence', 0xffffffff - 1) ])
             inputsPaths.append(hwAddress)
             pubKeys.append(pubkeys)

plugins/trezor/trezor.py

@@ -6,7 +6,7 @@ from electrum.bitcoin import (b58_address_to_hash160, xpub_from_pubkey,
 from electrum import constants
 from electrum.i18n import _
 from electrum.plugins import BasePlugin, Device
-from electrum.transaction import deserialize
+from electrum.transaction import deserialize, Transaction
 from electrum.keystore import Hardware_KeyStore, is_xpubkey, parse_xpubkey
 
 from ..hw_wallet import HW_PluginBase
@@ -63,6 +63,8 @@ class TrezorKeyStore(Hardware_KeyStore):
         for txin in tx.inputs():
             pubkeys, x_pubkeys = tx.get_sorted_pubkeys(txin)
             tx_hash = txin['prevout_hash']
+            if txin.get('prev_tx') is None and not Transaction.is_segwit_input(txin):
+                raise Exception(_('Offline signing with {} is not supported for legacy inputs.').format(self.device))
             prev_tx[tx_hash] = txin['prev_tx']
             for x_pubkey in x_pubkeys:
                 if not is_xpubkey(x_pubkey):