From 16fa85bfa49a8a001443b7dd8c6e3b7991e8c858 Mon Sep 17 00:00:00 2001
From: Adam Gibson <ekaggata@gmail.com>
Date: Tue, 19 Oct 2021 19:34:35 +0100
Subject: [PATCH] Prevent amounts less than minsize being processed

Prior to this commit, it was possible for a modified
taker client to get a maker to participate in a join
tx with a size less than their minsize, which could
burn up to an amount of the txfee contribution to
miner fees.
After this commit, the maker stops the coinjoin
coordination when the too-small coinjoin size is seen,
as intended.
Additionally, a check is now in place in the function
`Maker.verify_unsigned_transaction` that the earned
amount is positive, which otherwise could raise an
Exception (but should now be impossible in any case).
Also, changed the default txfee_contibution to zero
as it is of no value to have a nonzero amount.
Also return added for unrecognized orderid, for clearer
error messages.
---
 jmclient/jmclient/configure.py       | 3 ++-
 jmclient/jmclient/maker.py           | 6 +++++-
 jmdaemon/jmdaemon/daemon_protocol.py | 2 ++
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/jmclient/jmclient/configure.py b/jmclient/jmclient/configure.py
index b56273db0..497bff0de 100644
--- a/jmclient/jmclient/configure.py
+++ b/jmclient/jmclient/configure.py
@@ -410,7 +410,8 @@ def jm_single():
 cjfee_factor = 0.1
 
 # [satoshis, any integer] / the average transaction fee you're adding to coinjoin transactions
-txfee_contribution = 100
+# (note: this will soon be deprecated; leave at zero)
+txfee_contribution = 0
 
 # [fraction, 0-1] / variance around the average fee. Ex: 1000 fee, 0.2 var = fee is btw 800-1200
 txfee_contribution_factor = 0.3
diff --git a/jmclient/jmclient/maker.py b/jmclient/jmclient/maker.py
index d790dc2f7..89ec9df01 100644
--- a/jmclient/jmclient/maker.py
+++ b/jmclient/jmclient/maker.py
@@ -215,7 +215,11 @@ def verify_unsigned_tx(self, tx, offerinfo):
         my_total_in = sum([va['value'] for va in utxos.values()])
         real_cjfee = calc_cj_fee(ordertype, cjfee, amount)
         expected_change_value = (my_total_in - amount - txfee + real_cjfee)
-        jlog.info('potentially earned = {}'.format(btc.amount_to_str(real_cjfee - txfee)))
+        potentially_earned = real_cjfee - txfee
+        if potentially_earned < 0:
+            return (False, "A negative earning was calculated: {}.".format(
+                potentially_earned))
+        jlog.info('potentially earned = {}'.format(btc.amount_to_str(potentially_earned)))
         jlog.info('mycjaddr, mychange = {}, {}'.format(cjaddr, changeaddr))
 
         #The remaining checks are needed to ensure
diff --git a/jmdaemon/jmdaemon/daemon_protocol.py b/jmdaemon/jmdaemon/daemon_protocol.py
index 5daf4090b..60b1294c0 100644
--- a/jmdaemon/jmdaemon/daemon_protocol.py
+++ b/jmdaemon/jmdaemon/daemon_protocol.py
@@ -771,9 +771,11 @@ def on_order_fill(self, nick, oid, amount, taker_pk, commit):
         offer_s = [o for o in self.offerlist if o['oid'] == oid]
         if len(offer_s) == 0:
             self.mcc.send_error(nick, 'oid not found')
+            return
         offer = offer_s[0]
         if amount < offer['minsize'] or amount > offer['maxsize']:
             self.mcc.send_error(nick, 'amount out of range')
+            return
         #prepare a pubkey for this valid transaction
         kp = init_keypair()
         try: