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New module utils openssh.certificate (#246)

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* Initial commit

* Adding informational comments

* Adding changelog fragment

* Fixing CRLF changelog fragment

* Refactoring public number parsing and added chaining for writer methods

* Adding more descriptive error for invalid certificate data

* Fixing signature data parsing

* Correcting ed25519 signature type to binary

* Applying initial review suggestions and fixing option-list writer

* Applying review suggestions

* Making OpensshWriter private
This commit is contained in:
Ajpantuso
2021-06-22 06:54:56 -04:00
committed by GitHub
parent 2ba77e015c
commit 5d153e05ef
5 changed files with 1018 additions and 1 deletions
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343
plugins/module_utils/openssh/utils.py
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@@ -1,6 +1,7 @@
# -*- coding: utf-8 -*-
#
# (c) 2020, Doug Stanley <doug+ansible@technologixllc.com>
# Copyright: (c) 2020, Doug Stanley <doug+ansible@technologixllc.com>
# Copyright: (c) 2021, Andrew Pantuso (@ajpantuso) <ajpantuso@gmail.com>
#
# Ansible is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
@@ -19,6 +20,38 @@ from __future__ import absolute_import, division, print_function
__metaclass__ = type
import re
from struct import Struct
from ansible.module_utils.six import PY3
# Protocol References
# -------------------
# https://datatracker.ietf.org/doc/html/rfc4251
# https://datatracker.ietf.org/doc/html/rfc4253
# https://datatracker.ietf.org/doc/html/rfc5656
# https://datatracker.ietf.org/doc/html/rfc8032
#
# Inspired by:
# ------------
# https://github.com/pyca/cryptography/blob/main/src/cryptography/hazmat/primitives/serialization/ssh.py
# https://github.com/paramiko/paramiko/blob/master/paramiko/message.py
if PY3:
long = int
# 0 (False) or 1 (True) encoded as a single byte
_BOOLEAN = Struct(b'?')
# Unsigned 8-bit integer in network-byte-order
_UBYTE = Struct(b'!B')
_UBYTE_MAX = 0xFF
# Unsigned 32-bit integer in network-byte-order
_UINT32 = Struct(b'!I')
# Unsigned 32-bit little endian integer
_UINT32_LE = Struct(b'<I')
_UINT32_MAX = 0xFFFFFFFF
# Unsigned 64-bit integer in network-byte-order
_UINT64 = Struct(b'!Q')
_UINT64_MAX = 0xFFFFFFFFFFFFFFFF
def parse_openssh_version(version_string):
@@ -33,3 +66,311 @@ def parse_openssh_version(version_string):
version = None
return version
# See https://datatracker.ietf.org/doc/html/rfc4251#section-5 for SSH data types
class OpensshParser(object):
"""Parser for OpenSSH encoded objects"""
BOOLEAN_OFFSET = 1
UINT32_OFFSET = 4
UINT64_OFFSET = 8
def __init__(self, data):
if not isinstance(data, (bytes, bytearray)):
raise TypeError("Data must be bytes-like not %s" % type(data))
self._data = memoryview(data) if PY3 else data
self._pos = 0
def boolean(self):
next_pos = self._check_position(self.BOOLEAN_OFFSET)
value = _BOOLEAN.unpack(self._data[self._pos:next_pos])[0]
self._pos = next_pos
return value
def uint32(self):
next_pos = self._check_position(self.UINT32_OFFSET)
value = _UINT32.unpack(self._data[self._pos:next_pos])[0]
self._pos = next_pos
return value
def uint64(self):
next_pos = self._check_position(self.UINT64_OFFSET)
value = _UINT64.unpack(self._data[self._pos:next_pos])[0]
self._pos = next_pos
return value
def string(self):
length = self.uint32()
next_pos = self._check_position(length)
value = self._data[self._pos:next_pos]
self._pos = next_pos
# Cast to bytes is required as a memoryview slice is itself a memoryview
return value if not PY3 else bytes(value)
def mpint(self):
return self._big_int(self.string(), "big", signed=True)
def name_list(self):
raw_string = self.string()
return raw_string.decode('ASCII').split(',')
# Convenience function, but not an official data type from SSH
def string_list(self):
result = []
raw_string = self.string()
if raw_string:
parser = OpensshParser(raw_string)
while parser.remaining_bytes():
result.append(parser.string())
return result
# Convenience function, but not an official data type from SSH
def option_list(self):
result = []
raw_string = self.string()
if raw_string:
parser = OpensshParser(raw_string)
while parser.remaining_bytes():
name = parser.string()
data = parser.string()
if data:
# data is doubly-encoded
data = OpensshParser(data).string()
result.append((name, data))
return result
def seek(self, offset):
self._pos = self._check_position(offset)
return self._pos
def remaining_bytes(self):
return len(self._data) - self._pos
def _check_position(self, offset):
if self._pos + offset > len(self._data):
raise ValueError("Insufficient data remaining at position: %s" % self._pos)
elif self._pos + offset < 0:
raise ValueError("Position cannot be less than zero.")
else:
return self._pos + offset
@classmethod
def signature_data(cls, signature_string):
signature_data = {}
parser = cls(signature_string)
signature_type = parser.string()
signature_blob = parser.string()
blob_parser = cls(signature_blob)
if signature_type == b'ssh-rsa':
# https://datatracker.ietf.org/doc/html/rfc4253#section-6.6
signature_data['s'] = cls._big_int(signature_blob, "big")
elif signature_type == b'ssh-dss':
# https://datatracker.ietf.org/doc/html/rfc4253#section-6.6
signature_data['r'] = cls._big_int(signature_blob[:20], "big")
signature_data['s'] = cls._big_int(signature_blob[20:], "big")
elif signature_type in (b'ecdsa-sha2-nistp256', b'ecdsa-sha2-nistp384', b'ecdsa-sha2-nistp521'):
# https://datatracker.ietf.org/doc/html/rfc5656#section-3.1.2
signature_data['r'] = blob_parser.mpint()
signature_data['s'] = blob_parser.mpint()
elif signature_type == b'ssh-ed25519':
# https://datatracker.ietf.org/doc/html/rfc8032#section-5.1.2
signature_data['R'] = cls._big_int(signature_blob[:32], "little")
signature_data['S'] = cls._big_int(signature_blob[32:], "little")
else:
raise ValueError("%s is not a valid signature type" % signature_type)
signature_data['signature_type'] = signature_type
return signature_data
@classmethod
def _big_int(cls, raw_string, byte_order, signed=False):
if byte_order not in ("big", "little"):
raise ValueError("Byte_order must be one of (big, little) not %s" % byte_order)
if PY3:
return int.from_bytes(raw_string, byte_order, signed=signed)
result = 0
byte_length = len(raw_string)
if byte_length > 0:
# Check sign-bit
msb = raw_string[0] if byte_order == "big" else raw_string[-1]
negative = bool(ord(msb) & 0x80)
# Match pad value for two's complement
pad = b'\xFF' if signed and negative else b'\x00'
# The definition of ``mpint`` enforces that unnecessary bytes are not encoded so they are added back
pad_length = (4 - byte_length % 4)
if pad_length < 4:
raw_string = pad * pad_length + raw_string if byte_order == "big" else raw_string + pad * pad_length
byte_length += pad_length
# Accumulate arbitrary precision integer bytes in the appropriate order
if byte_order == "big":
for i in range(0, byte_length, cls.UINT32_OFFSET):
left_shift = result << cls.UINT32_OFFSET * 8
result = left_shift + _UINT32.unpack(raw_string[i:i + cls.UINT32_OFFSET])[0]
else:
for i in range(byte_length, 0, -cls.UINT32_OFFSET):
left_shift = result << cls.UINT32_OFFSET * 8
result = left_shift + _UINT32_LE.unpack(raw_string[i - cls.UINT32_OFFSET:i])[0]
# Adjust for two's complement
if signed and negative:
result -= 1 << (8 * byte_length)
return result
class _OpensshWriter(object):
"""Writes SSH encoded values to a bytes-like buffer
.. warning::
This class is a private API and must not be exported outside of the openssh module_utils.
It is not to be used to construct Openssh objects, but rather as a utility to assist
in validating parsed material.
"""
def __init__(self, buffer=None):
if buffer is not None:
if not isinstance(buffer, (bytes, bytearray)):
raise TypeError("Buffer must be a bytes-like object not %s" % type(buffer))
else:
buffer = bytearray()
self._buff = buffer
def boolean(self, value):
if not isinstance(value, bool):
raise TypeError("Value must be of type bool not %s" % type(value))
self._buff.extend(_BOOLEAN.pack(value))
return self
def uint32(self, value):
if not isinstance(value, int):
raise TypeError("Value must be of type int not %s" % type(value))
if value < 0 or value > _UINT32_MAX:
raise ValueError("Value must be a positive integer less than %s" % _UINT32_MAX)
self._buff.extend(_UINT32.pack(value))
return self
def uint64(self, value):
if not isinstance(value, (long, int)):
raise TypeError("Value must be of type (long, int) not %s" % type(value))
if value < 0 or value > _UINT64_MAX:
raise ValueError("Value must be a positive integer less than %s" % _UINT64_MAX)
self._buff.extend(_UINT64.pack(value))
return self
def string(self, value):
if not isinstance(value, (bytes, bytearray)):
raise TypeError("Value must be bytes-like not %s" % type(value))
self.uint32(len(value))
self._buff.extend(value)
return self
def mpint(self, value):
if not isinstance(value, (int, long)):
raise TypeError("Value must be of type (long, int) not %s" % type(value))
self.string(self._int_to_mpint(value))
return self
def name_list(self, value):
if not isinstance(value, list):
raise TypeError("Value must be a list of byte strings not %s" % type(value))
try:
self.string(','.join(value).encode('ASCII'))
except UnicodeEncodeError as e:
raise ValueError("Name-list's must consist of US-ASCII characters: %s" % e)
return self
def string_list(self, value):
if not isinstance(value, list):
raise TypeError("Value must be a list of byte string not %s" % type(value))
writer = _OpensshWriter()
for s in value:
writer.string(s)
self.string(writer.bytes())
return self
def option_list(self, value):
if not isinstance(value, list) or (value and not isinstance(value[0], tuple)):
raise TypeError("Value must be a list of tuples")
writer = _OpensshWriter()
for name, data in value:
writer.string(name)
# SSH option data is encoded twice though this behavior is not documented
writer.string(_OpensshWriter().string(data).bytes() if data else bytes())
self.string(writer.bytes())
return self
@staticmethod
def _int_to_mpint(num):
if PY3:
byte_length = (num.bit_length() + 7) // 8
try:
result = num.to_bytes(byte_length, "big", signed=True)
# Handles values which require \x00 or \xFF to pad sign-bit
except OverflowError:
result = num.to_bytes(byte_length + 1, "big", signed=True)
else:
result = bytes()
# 0 and -1 are treated as special cases since they are used as sentinels for all other values
if num == 0:
result += b'\x00'
elif num == -1:
result += b'\xFF'
elif num > 0:
while num >> 32:
result = _UINT32.pack(num & _UINT32_MAX) + result
num = num >> 32
# Pack last 4 bytes individually to discard insignificant bytes
while num:
result = _UBYTE.pack(num & _UBYTE_MAX) + result
num = num >> 8
# Zero pad final byte if most-significant bit is 1 as per mpint definition
if ord(result[0]) & 0x80:
result = b'\x00' + result
else:
while (num >> 32) < -1:
result = _UINT32.pack(num & _UINT32_MAX) + result
num = num >> 32
while num < -1:
result = _UBYTE.pack(num & _UBYTE_MAX) + result
num = num >> 8
if not ord(result[0]) & 0x80:
result = b'\xFF' + result
return result
def bytes(self):
return bytes(self._buff)