commit 9a98ad2881f67dab338e5a01c5d85169be2ef76e
parent 5be9f03fdfa12788e9650d0da809cbfbb2d31061
Author: ThomasV <thomasv@electrum.org>
Date: Sat, 16 Jan 2016 12:01:49 +0100
Merge branch 'master' of git://github.com/spesmilo/electrum
Diffstat:
2 files changed, 47 insertions(+), 16 deletions(-)
diff --git a/lib/coinchooser.py b/lib/coinchooser.py
@@ -17,13 +17,51 @@
# along with this program. If not, see <http://www.gnu.org/licenses/>.
from collections import defaultdict, namedtuple
-from random import choice, randint, shuffle
from math import floor, log10
+import struct
-from bitcoin import COIN, TYPE_ADDRESS
+from bitcoin import sha256, COIN, TYPE_ADDRESS
from transaction import Transaction
from util import NotEnoughFunds, PrintError, profiler
+# A simple deterministic PRNG. Used to deterministically shuffle a
+# set of coins - the same set of coins should produce the same output.
+# Although choosing UTXOs "randomly" we want it to be deterministic,
+# so if sending twice from the same UTXO set we choose the same UTXOs
+# to spend. This prevents attacks on users by malicious or stale
+# servers.
+
+class PRNG:
+ def __init__(self, seed):
+ self.sha = sha256(seed)
+ self.pool = bytearray()
+
+ def get_bytes(self, n):
+ while len(self.pool) < n:
+ self.pool.extend(self.sha)
+ self.sha = sha256(self.sha)
+ result, self.pool = self.pool[:n], self.pool[n:]
+ return result
+
+ def random(self):
+ # Returns random double in [0, 1)
+ four = self.get_bytes(4)
+ return struct.unpack("I", four)[0] / 4294967296.0
+
+ def randint(self, start, end):
+ # Returns random integer in [start, end)
+ return start + int(self.random() * (end - start))
+
+ def choice(self, seq):
+ return seq[int(self.random() * len(seq))]
+
+ def shuffle(self, x):
+ for i in reversed(xrange(1, len(x))):
+ # pick an element in x[:i+1] with which to exchange x[i]
+ j = int(self.random() * (i+1))
+ x[i], x[j] = x[j], x[i]
+
+
Bucket = namedtuple('Bucket', ['desc', 'size', 'value', 'coins'])
def strip_unneeded(bkts, sufficient_funds):
@@ -87,8 +125,8 @@ class CoinChooserBase(PrintError):
amounts = []
while n > 1:
average = remaining // n
- amount = randint(int(average * 0.7), int(average * 1.3))
- precision = min(choice(zeroes), int(floor(log10(amount))))
+ amount = self.p.randint(int(average * 0.7), int(average * 1.3))
+ precision = min(self.p.choice(zeroes), int(floor(log10(amount))))
amount = int(round(amount, -precision))
amounts.append(amount)
remaining -= amount
@@ -127,6 +165,10 @@ class CoinChooserBase(PrintError):
the transaction) it is kept, otherwise none is sent and it is
added to the transaction fee.'''
+ # Deterministic randomness from coins
+ utxos = [c['prevout_hash'] + str(c['prevout_n']) for c in coins]
+ self.p = PRNG(''.join(sorted(utxos)))
+
# Copy the ouputs so when adding change we don't modify "outputs"
tx = Transaction.from_io([], outputs[:])
# Size of the transaction with no inputs and no change
@@ -201,7 +243,7 @@ class CoinChooserRandom(CoinChooserBase):
for i in range(attempts):
# Get a random permutation of the buckets, and
# incrementally combine buckets until sufficient
- shuffle(permutation)
+ self.p.shuffle(permutation)
bkts = []
for count, index in enumerate(permutation):
bkts.append(buckets[index])
diff --git a/lib/wallet.py b/lib/wallet.py
@@ -196,7 +196,6 @@ class Abstract_Wallet(PrintError):
self.lock = threading.Lock()
self.transaction_lock = threading.Lock()
self.tx_event = threading.Event()
- self.tx_cache = (None, None, None, None, None)
self.check_history()
@@ -966,14 +965,6 @@ class Abstract_Wallet(PrintError):
# Change <= dust threshold is added to the tx fee
dust_threshold = 182 * 3 * self.relayfee() / 1000
- # Check cache to see if we just calculated this. If prior
- # calculated a fee and this fixes it to the same, return same
- # answer, to avoid random coin selection changing the answer
- if self.tx_cache[:4] == (outputs, coins, change_addrs, dust_threshold):
- tx = self.tx_cache[4]
- if tx.get_fee() == fee_estimator(tx.estimated_size()):
- return tx
-
# Let the coin chooser select the coins to spend
max_change = 3 if self.multiple_change else 1
coin_chooser = self.coin_chooser(config)
@@ -983,8 +974,6 @@ class Abstract_Wallet(PrintError):
# Sort the inputs and outputs deterministically
tx.BIP_LI01_sort()
- self.tx_cache = (outputs, coins, change_addrs, dust_threshold, tx)
-
run_hook('make_unsigned_transaction', self, tx)
return tx
