# Copyright (C) 2003-2007 Robey Pointer <robeypointer@gmail.com>
#
# This file is part of paramiko.
#
# Paramiko is free software; you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation; either version 2.1 of the License, or (at your option)
# any later version.
#
# Paramiko is distributed in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
# A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with Paramiko; if not, write to the Free Software Foundation, Inc.,
# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
"""
Common API for all public keys.
"""
import base64
from binascii import unhexlify
import os
from hashlib import md5
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.ciphers import algorithms, modes, Cipher
from paramiko import util
from paramiko.common import o600
from paramiko.py3compat import u, encodebytes, decodebytes, b, string_types
from paramiko.ssh_exception import SSHException, PasswordRequiredException
from paramiko.message import Message
class PKey(object):
"""
Base class for public keys.
"""
# known encryption types for private key files:
_CIPHER_TABLE = {
"AES-128-CBC": {
"cipher": algorithms.AES,
"keysize": 16,
"blocksize": 16,
"mode": modes.CBC,
},
"AES-256-CBC": {
"cipher": algorithms.AES,
"keysize": 32,
"blocksize": 16,
"mode": modes.CBC,
},
"DES-EDE3-CBC": {
"cipher": algorithms.TripleDES,
"keysize": 24,
"blocksize": 8,
"mode": modes.CBC,
},
}
def __init__(self, msg=None, data=None):
"""
Create a new instance of this public key type. If ``msg`` is given,
the key's public part(s) will be filled in from the message. If
``data`` is given, the key's public part(s) will be filled in from
the string.
:param .Message msg:
an optional SSH `.Message` containing a public key of this type.
:param str data: an optional string containing a public key
of this type
:raises: `.SSHException` --
if a key cannot be created from the ``data`` or ``msg`` given, or
no key was passed in.
"""
pass
def asbytes(self):
"""
Return a string of an SSH `.Message` made up of the public part(s) of
this key. This string is suitable for passing to `__init__` to
re-create the key object later.
"""
return bytes()
def __str__(self):
return self.asbytes()
# noinspection PyUnresolvedReferences
# TODO: The comparison functions should be removed as per:
# https://docs.python.org/3.0/whatsnew/3.0.html#ordering-comparisons
def __cmp__(self, other):
"""
Compare this key to another. Returns 0 if this key is equivalent to
the given key, or non-0 if they are different. Only the public parts
of the key are compared, so a public key will compare equal to its
corresponding private key.
:param .PKey other: key to compare to.
"""
hs = hash(self)
ho = hash(other)
if hs != ho:
return cmp(hs, ho) # noqa
return cmp(self.asbytes(), other.asbytes()) # noqa
def __eq__(self, other):
return hash(self) == hash(other)
def get_name(self):
"""
Return the name of this private key implementation.
:return:
name of this private key type, in SSH terminology, as a `str` (for
example, ``"ssh-rsa"``).
"""
return ""
def get_bits(self):
"""
Return the number of significant bits in this key. This is useful
for judging the relative security of a key.
:return: bits in the key (as an `int`)
"""
return 0
def can_sign(self):
"""
Return ``True`` if this key has the private part necessary for signing
data.
"""
return False
def get_fingerprint(self):
"""
Return an MD5 fingerprint of the public part of this key. Nothing
secret is revealed.
:return:
a 16-byte `string <str>` (binary) of the MD5 fingerprint, in SSH
format.
"""
return md5(self.asbytes()).digest()
def get_base64(self):
"""
Return a base64 string containing the public part of this key. Nothing
secret is revealed. This format is compatible with that used to store
public key files or recognized host keys.
:return: a base64 `string <str>` containing the public part of the key.
"""
return u(encodebytes(self.asbytes())).replace("\n", "")
def sign_ssh_data(self, data):
"""
Sign a blob of data with this private key, and return a `.Message`
representing an SSH signature message.
:param str data: the data to sign.
:return: an SSH signature `message <.Message>`.
"""
return bytes()
def verify_ssh_sig(self, data, msg):
"""
Given a blob of data, and an SSH message representing a signature of
that data, verify that it was signed with this key.
:param str data: the data that was signed.
:param .Message msg: an SSH signature message
:return:
``True`` if the signature verifies correctly; ``False`` otherwise.
"""
return False
@classmethod
def from_private_key_file(cls, filename, password=None):
"""
Create a key object by reading a private key file. If the private
key is encrypted and ``password`` is not ``None``, the given password
will be used to decrypt the key (otherwise `.PasswordRequiredException`
is thrown). Through the magic of Python, this factory method will
exist in all subclasses of PKey (such as `.RSAKey` or `.DSSKey`), but
is useless on the abstract PKey class.
:param str filename: name of the file to read
:param str password:
an optional password to use to decrypt the key file, if it's
encrypted
:return: a new `.PKey` based on the given private key
:raises: ``IOError`` -- if there was an error reading the file
:raises: `.PasswordRequiredException` -- if the private key file is
encrypted, and ``password`` is ``None``
:raises: `.SSHException` -- if the key file is invalid
"""
key = cls(filename=filename, password=password)
return key
@classmethod
def from_private_key(cls, file_obj, password=None):
"""
Create a key object by reading a private key from a file (or file-like)
object. If the private key is encrypted and ``password`` is not
``None``, the given password will be used to decrypt the key (otherwise
`.PasswordRequiredException` is thrown).
:param file_obj: the file-like object to read from
:param str password:
an optional password to use to decrypt the key, if it's encrypted
:return: a new `.PKey` based on the given private key
:raises: ``IOError`` -- if there was an error reading the key
:raises: `.PasswordRequiredException` --
if the private key file is encrypted, and ``password`` is ``None``
:raises: `.SSHException` -- if the key file is invalid
"""
key = cls(file_obj=file_obj, password=password)
return key
def write_private_key_file(self, filename, password=None):
"""
Write private key contents into a file. If the password is not
``None``, the key is encrypted before writing.
:param str filename: name of the file to write
:param str password:
an optional password to use to encrypt the key file
:raises: ``IOError`` -- if there was an error writing the file
:raises: `.SSHException` -- if the key is invalid
"""
raise Exception("Not implemented in PKey")
def write_private_key(self, file_obj, password=None):
"""
Write private key contents into a file (or file-like) object. If the
password is not ``None``, the key is encrypted before writing.
:param file_obj: the file-like object to write into
:param str password: an optional password to use to encrypt the key
:raises: ``IOError`` -- if there was an error writing to the file
:raises: `.SSHException` -- if the key is invalid
"""
raise Exception("Not implemented in PKey")
def _read_private_key_file(self, tag, filename, password=None):
"""
Read an SSH2-format private key file, looking for a string of the type
``"BEGIN xxx PRIVATE KEY"`` for some ``xxx``, base64-decode the text we
find, and return it as a string. If the private key is encrypted and
``password`` is not ``None``, the given password will be used to
decrypt the key (otherwise `.PasswordRequiredException` is thrown).
:param str tag: ``"RSA"`` or ``"DSA"``, the tag used to mark the
data block.
:param str filename: name of the file to read.
:param str password:
an optional password to use to decrypt the key file, if it's
encrypted.
:return: data blob (`str`) that makes up the private key.
:raises: ``IOError`` -- if there was an error reading the file.
:raises: `.PasswordRequiredException` -- if the private key file is
encrypted, and ``password`` is ``None``.
:raises: `.SSHException` -- if the key file is invalid.
"""
with open(filename, "r") as f:
data = self._read_private_key(tag, f, password)
return data
def _read_private_key(self, tag, f, password=None):
lines = f.readlines()
start = 0
beginning_of_key = "-----BEGIN " + tag + " PRIVATE KEY-----"
while start < len(lines) and lines[start].strip() != beginning_of_key:
start += 1
if start >= len(lines):
raise SSHException("not a valid " + tag + " private key file")
# parse any headers first
headers = {}
start += 1
while start < len(lines):
line = lines[start].split(": ")
if len(line) == 1:
break
headers[line[0].lower()] = line[1].strip()
start += 1
# find end
end = start
ending_of_key = "-----END " + tag + " PRIVATE KEY-----"
while end < len(lines) and lines[end].strip() != ending_of_key:
end += 1
# if we trudged to the end of the file, just try to cope.
try:
data = decodebytes(b("".join(lines[start:end])))
except base64.binascii.Error as e:
raise SSHException("base64 decoding error: " + str(e))
if "proc-type" not in headers:
# unencryped: done
return data
# encrypted keyfile: will need a password
proc_type = headers["proc-type"]
if proc_type != "4,ENCRYPTED":
raise SSHException(
'Unknown private key structure "{}"'.format(proc_type)
)
try:
encryption_type, saltstr = headers["dek-info"].split(",")
except:
raise SSHException("Can't parse DEK-info in private key file")
if encryption_type not in self._CIPHER_TABLE:
raise SSHException(
'Unknown private key cipher "{}"'.format(encryption_type)
)
# if no password was passed in,
# raise an exception pointing out that we need one
if password is None:
raise PasswordRequiredException("Private key file is encrypted")
cipher = self._CIPHER_TABLE[encryption_type]["cipher"]
keysize = self._CIPHER_TABLE[encryption_type]["keysize"]
mode = self._CIPHER_TABLE[encryption_type]["mode"]
salt = unhexlify(b(saltstr))
key = util.generate_key_bytes(md5, salt, password, keysize)
decryptor = Cipher(
cipher(key), mode(salt), backend=default_backend()
).decryptor()
return decryptor.update(data) + decryptor.finalize()
def _write_private_key_file(self, filename, key, format, password=None):
"""
Write an SSH2-format private key file in a form that can be read by
paramiko or openssh. If no password is given, the key is written in
a trivially-encoded format (base64) which is completely insecure. If
a password is given, DES-EDE3-CBC is used.
:param str tag:
``"RSA"`` or ``"DSA"``, the tag used to mark the data block.
:param filename: name of the file to write.
:param str data: data blob that makes up the private key.
:param str password: an optional password to use to encrypt the file.
:raises: ``IOError`` -- if there was an error writing the file.
"""
# Ensure that we create new key files directly with a user-only mode,
# instead of opening, writing, then chmodding, which leaves us open to
# CVE-2022-24302.
# NOTE: O_TRUNC is a noop on new files, and O_CREAT is a noop on
# existing files, so using all 3 in both cases is fine. Ditto the use
# of the 'mode' argument; it should be safe to give even for existing
# files (though it will not act like a chmod in that case).
kwargs = dict(flags=os.O_WRONLY | os.O_TRUNC | os.O_CREAT, mode=o600)
# NOTE: yea, you still gotta inform the FLO that it is in "write" mode
with os.fdopen(os.open(filename, **kwargs), mode="w") as f:
# TODO 3.0: remove the now redundant chmod
os.chmod(filename, o600)
self._write_private_key(f, key, format, password=password)
def _write_private_key(self, f, key, format, password=None):
if password is None:
encryption = serialization.NoEncryption()
else:
encryption = serialization.BestAvailableEncryption(b(password))
f.write(
key.private_bytes(
serialization.Encoding.PEM, format, encryption
).decode()
)
def _check_type_and_load_cert(self, msg, key_type, cert_type):
"""
Perform message type-checking & optional certificate loading.
This includes fast-forwarding cert ``msg`` objects past the nonce, so
that the subsequent fields are the key numbers; thus the caller may
expect to treat the message as key material afterwards either way.
The obtained key type is returned for classes which need to know what
it was (e.g. ECDSA.)
"""
# Normalization; most classes have a single key type and give a string,
# but eg ECDSA is a 1:N mapping.
key_types = key_type
cert_types = cert_type
if isinstance(key_type, string_types):
key_types = [key_types]
if isinstance(cert_types, string_types):
cert_types = [cert_types]
# Can't do much with no message, that should've been handled elsewhere
if msg is None:
raise SSHException("Key object may not be empty")
# First field is always key type, in either kind of object. (make sure
# we rewind before grabbing it - sometimes caller had to do their own
# introspection first!)
msg.rewind()
type_ = msg.get_text()
# Regular public key - nothing special to do besides the implicit
# type check.
if type_ in key_types:
pass
# OpenSSH-compatible certificate - store full copy as .public_blob
# (so signing works correctly) and then fast-forward past the
# nonce.
elif type_ in cert_types:
# This seems the cleanest way to 'clone' an already-being-read
# message; they're *IO objects at heart and their .getvalue()
# always returns the full value regardless of pointer position.
self.load_certificate(Message(msg.asbytes()))
# Read out nonce as it comes before the public numbers.
# TODO: usefully interpret it & other non-public-number fields
# (requires going back into per-type subclasses.)
msg.get_string()
else:
err = "Invalid key (class: {}, data type: {}"
raise SSHException(err.format(self.__class__.__name__, type_))
def load_certificate(self, value):
"""
Supplement the private key contents with data loaded from an OpenSSH
public key (``.pub``) or certificate (``-cert.pub``) file, a string
containing such a file, or a `.Message` object.
The .pub contents adds no real value, since the private key
file includes sufficient information to derive the public
key info. For certificates, however, this can be used on
the client side to offer authentication requests to the server
based on certificate instead of raw public key.
See:
https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.certkeys
Note: very little effort is made to validate the certificate contents,
that is for the server to decide if it is good enough to authenticate
successfully.
"""
if isinstance(value, Message):
constructor = "from_message"
elif os.path.isfile(value):
constructor = "from_file"
else:
constructor = "from_string"
blob = getattr(PublicBlob, constructor)(value)
if not blob.key_type.startswith(self.get_name()):
err = "PublicBlob type {} incompatible with key type {}"
raise ValueError(err.format(blob.key_type, self.get_name()))
self.public_blob = blob
# General construct for an OpenSSH style Public Key blob
# readable from a one-line file of the format:
# <key-name> <base64-blob> [<comment>]
# Of little value in the case of standard public keys
# {ssh-rsa, ssh-dss, ssh-ecdsa, ssh-ed25519}, but should
# provide rudimentary support for {*-cert.v01}
class PublicBlob(object):
"""
OpenSSH plain public key or OpenSSH signed public key (certificate).
Tries to be as dumb as possible and barely cares about specific
per-key-type data.
..note::
Most of the time you'll want to call `from_file`, `from_string` or
`from_message` for useful instantiation, the main constructor is
basically "I should be using ``attrs`` for this."
"""
def __init__(self, type_, blob, comment=None):
"""
Create a new public blob of given type and contents.
:param str type_: Type indicator, eg ``ssh-rsa``.
:param blob: The blob bytes themselves.
:param str comment: A comment, if one was given (e.g. file-based.)
"""
self.key_type = type_
self.key_blob = blob
self.comment = comment
@classmethod
def from_file(cls, filename):
"""
Create a public blob from a ``-cert.pub``-style file on disk.
"""
with open(filename) as f:
string = f.read()
return cls.from_string(string)
@classmethod
def from_string(cls, string):
"""
Create a public blob from a ``-cert.pub``-style string.
"""
fields = string.split(None, 2)
if len(fields) < 2:
msg = "Not enough fields for public blob: {}"
raise ValueError(msg.format(fields))
key_type = fields[0]
key_blob = decodebytes(b(fields[1]))
try:
comment = fields[2].strip()
except IndexError:
comment = None
# Verify that the blob message first (string) field matches the
# key_type
m = Message(key_blob)
blob_type = m.get_text()
if blob_type != key_type:
deets = "key type={!r}, but blob type={!r}".format(
key_type, blob_type
)
raise ValueError("Invalid PublicBlob contents: {}".format(deets))
# All good? All good.
return cls(type_=key_type, blob=key_blob, comment=comment)
@classmethod
def from_message(cls, message):
"""
Create a public blob from a network `.Message`.
Specifically, a cert-bearing pubkey auth packet, because by definition
OpenSSH-style certificates 'are' their own network representation."
"""
type_ = message.get_text()
return cls(type_=type_, blob=message.asbytes())
def __str__(self):
ret = "{} public key/certificate".format(self.key_type)
if self.comment:
ret += "- {}".format(self.comment)
return ret
def __eq__(self, other):
# Just piggyback on Message/BytesIO, since both of these should be one.
return self and other and self.key_blob == other.key_blob
def __ne__(self, other):
return not self == other