invoices: deal with expiration of "0" mess

Internally, we've been using an expiration of 0 to mean "never expires".
For LN invoices, BOLT-11 does not specify what an expiration of 0 means.
Other clients seem to treat it as "0 seconds" (i.e. already expired).
This means there is no way to create a BOLT-11 invoice that "never" expires.

For LN invoices,
- we now treat an expiration of 0, , as "0 seconds",
- when creating an invoice, if the user selected never, we will put 100 years as expiration

electrum/gui/kivy/uix/screens.py

@@ -24,7 +24,7 @@ from kivy.utils import platform
 from kivy.logger import Logger
 
 from electrum.util import profiler, parse_URI, format_time, InvalidPassword, NotEnoughFunds, Fiat
-from electrum.util import PR_TYPE_ONCHAIN, PR_TYPE_LN
+from electrum.util import PR_TYPE_ONCHAIN, PR_TYPE_LN, PR_DEFAULT_EXPIRATION_WHEN_CREATING
 from electrum import bitcoin, constants
 from electrum.transaction import Transaction, tx_from_any, PartialTransaction, PartialTxOutput
 from electrum.util import (parse_URI, InvalidBitcoinURI, PR_PAID, PR_UNKNOWN, PR_EXPIRED,
@@ -419,7 +419,7 @@ class ReceiveScreen(CScreen):
         Clock.schedule_interval(lambda dt: self.update(), 5)
 
     def expiry(self):
-        return self.app.electrum_config.get('request_expiry', 3600) # 1 hour
+        return self.app.electrum_config.get('request_expiry', PR_DEFAULT_EXPIRATION_WHEN_CREATING)
 
     def clear(self):
         self.screen.address = ''

electrum/gui/qt/main_window.py

@@ -62,7 +62,7 @@ from electrum.util import (format_time, format_satoshis, format_fee_satoshis,
                            get_new_wallet_name, send_exception_to_crash_reporter,
                            InvalidBitcoinURI, maybe_extract_bolt11_invoice, NotEnoughFunds,
                            NoDynamicFeeEstimates, MultipleSpendMaxTxOutputs)
-from electrum.util import PR_TYPE_ONCHAIN, PR_TYPE_LN
+from electrum.util import PR_TYPE_ONCHAIN, PR_TYPE_LN, PR_DEFAULT_EXPIRATION_WHEN_CREATING
 from electrum.transaction import (Transaction, PartialTxInput,
                                   PartialTransaction, PartialTxOutput)
 from electrum.address_synchronizer import AddTransactionException
@@ -1007,7 +1007,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
         evl = sorted(pr_expiration_values.items())
         evl_keys = [i[0] for i in evl]
         evl_values = [i[1] for i in evl]
-        default_expiry = self.config.get('request_expiry', 3600)
+        default_expiry = self.config.get('request_expiry', PR_DEFAULT_EXPIRATION_WHEN_CREATING)
         try:
             i = evl_keys.index(default_expiry)
         except ValueError:
@@ -1139,7 +1139,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
     def create_invoice(self, is_lightning):
         amount = self.receive_amount_e.get_amount()
         message = self.receive_message_e.text()
-        expiry = self.config.get('request_expiry', 3600)
+        expiry = self.config.get('request_expiry', PR_DEFAULT_EXPIRATION_WHEN_CREATING)
         if is_lightning:
             key = self.wallet.lnworker.add_request(amount, message, expiry)
         else:

electrum/lnaddr.py

@@ -199,6 +199,8 @@ def lnencode(addr, privkey):
             # Get minimal length by trimming leading 5 bits at a time.
             expirybits = bitstring.pack('intbe:64', v)[4:64]
             while expirybits.startswith('0b00000'):
+                if len(expirybits) == 5:
+                    break  # v == 0
                 expirybits = expirybits[5:]
             data += tagged('x', expirybits)
         elif k == 'h':
@@ -259,21 +261,24 @@ class LnAddr(object):
         return self._min_final_cltv_expiry
 
     def get_tag(self, tag):
-        description = ''
-        for k,v in self.tags:
+        for k, v in self.tags:
             if k == tag:
-                description = v
-                break
-        return description
+                return v
+        return None
 
-    def get_description(self):
-        return self.get_tag('d')
+    def get_description(self) -> str:
+        return self.get_tag('d') or ''
 
-    def get_expiry(self):
-        return int(self.get_tag('x') or '3600')
+    def get_expiry(self) -> int:
+        exp = self.get_tag('x')
+        if exp is None:
+            exp = 3600
+        return int(exp)
 
-    def is_expired(self):
+    def is_expired(self) -> bool:
         now = time.time()
+        # BOLT-11 does not specify what expiration of '0' means.
+        # we treat it as 0 seconds here (instead of never)
         return now > self.get_expiry() + self.date
 
 

electrum/lnworker.py

@@ -1112,7 +1112,7 @@ class LNWallet(LNWorker):
             raise Exception(_("add invoice timed out"))
 
     @log_exceptions
-    async def _add_request_coro(self, amount_sat, message, expiry):
+    async def _add_request_coro(self, amount_sat, message, expiry: int):
         timestamp = int(time.time())
         routing_hints = await self._calc_routing_hints_for_invoice(amount_sat)
         if not routing_hints:
@@ -1122,6 +1122,12 @@ class LNWallet(LNWorker):
         payment_hash = sha256(payment_preimage)
         info = PaymentInfo(payment_hash, amount_sat, RECEIVED, PR_UNPAID)
         amount_btc = amount_sat/Decimal(COIN) if amount_sat else None
+        if expiry == 0:
+            # hack: BOLT-11 is not really clear on what an expiry of 0 means.
+            # It probably interprets it as 0 seconds, so already expired...
+            # Our higher level invoices code however uses 0 for "never".
+            # Hence set some high expiration here
+            expiry = 100 * 365 * 24 * 60 * 60  # 100 years
         lnaddr = LnAddr(payment_hash, amount_btc,
                         tags=[('d', message),
                               ('c', MIN_FINAL_CLTV_EXPIRY_FOR_INVOICE),

electrum/util.py

@@ -104,17 +104,22 @@ pr_tooltips = {
     PR_FAILED:_('Failed'),
 }
 
+PR_DEFAULT_EXPIRATION_WHEN_CREATING = 24*60*60  # 1 day
 pr_expiration_values = {
     0: _('Never'),
     10*60: _('10 minutes'),
     60*60: _('1 hour'),
     24*60*60: _('1 day'),
-    7*24*60*60: _('1 week')
+    7*24*60*60: _('1 week'),
 }
+assert PR_DEFAULT_EXPIRATION_WHEN_CREATING in pr_expiration_values
+
 
 def get_request_status(req):
     status = req['status']
     exp = req.get('exp', 0) or 0
+    if req.get('type') == PR_TYPE_LN and exp == 0:
+        status = PR_EXPIRED  # for BOLT-11 invoices, exp==0 means 0 seconds
     if req['status'] == PR_UNPAID and exp > 0 and req['time'] + req['exp'] < time.time():
         status = PR_EXPIRED
     status_str = pr_tooltips[status]