Created
December 16, 2015 16:59
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Paramiko leaks Transports and Channels via Transport.server_accepts
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import time | |
import socket | |
import threading | |
import paramiko | |
class ServerInterface(paramiko.ServerInterface): | |
def get_allowed_auths(self, username): | |
return "none" | |
def check_auth_none(self, username): | |
print "auth", username | |
return paramiko.AUTH_SUCCESSFUL | |
def check_channel_request(self, kind, chanid): | |
return paramiko.OPEN_SUCCEEDED if kind == "session" else paramiko.OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED | |
key = paramiko.RSAKey.generate(1024) | |
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) | |
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) | |
sock.bind(("127.0.0.1", 2222)) | |
sock.listen(10) | |
print "listening..." | |
client, address = sock.accept() | |
transport = paramiko.Transport(client) | |
transport.load_server_moduli() | |
transport.add_server_key(key) | |
transport.set_subsystem_handler("sftp", paramiko.SFTPServer, paramiko.SFTPServerInterface) | |
event = threading.Event() | |
transport.start_server(server=ServerInterface(), event=event) | |
event.wait() | |
# Transport.server_accepts is empty | |
print "BEFORE transport.server_accepts =", transport.server_accepts | |
# Do work... | |
while transport.is_active(): | |
time.sleep(1) | |
# later on after the Transport finishes, we notice Transport.server_accepts has a single entry | |
# to a closed channel holding a disconnected transport which leaks | |
print "AFTER transport.server_accepts =", transport.server_accepts | |
# Example output | |
# > python sftp-server-test.py | |
# listening... | |
# BEFORE transport.server_accepts = [] | |
# auth foo | |
# AFTER transport.server_accepts = [<paramiko.Channel 1 (closed) -> <paramiko.Transport at 0x68273d50L (unconnected)>>] |
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