# Copyright (C) 2003-2007 Robey Pointer # # 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., # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. """ Common API for all public keys. """ import base64 from base64 import encodebytes, decodebytes from binascii import unhexlify import os from hashlib import md5 import re import struct import bcrypt 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.util import u, b from paramiko.common import o600 from paramiko.ssh_exception import SSHException, PasswordRequiredException from paramiko.message import Message OPENSSH_AUTH_MAGIC = b"openssh-key-v1\x00" def _unpad_openssh(data): # At the moment, this is only used for unpadding private keys on disk. This # really ought to be made constant time (possibly by upstreaming this logic # into pyca/cryptography). padding_length = data[-1] if 0x20 <= padding_length < 0x7F: return data # no padding, last byte part comment (printable ascii) if padding_length > 15: raise SSHException("Invalid key") for i in range(padding_length): if data[i - padding_length] != i + 1: raise SSHException("Invalid key") return data[:-padding_length] class PKey: """ 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, }, } _PRIVATE_KEY_FORMAT_ORIGINAL = 1 _PRIVATE_KEY_FORMAT_OPENSSH = 2 BEGIN_TAG = re.compile( r"^-{5}BEGIN (RSA|DSA|EC|OPENSSH) PRIVATE KEY-{5}\s*$" ) END_TAG = re.compile(r"^-{5}END (RSA|DSA|EC|OPENSSH) PRIVATE KEY-{5}\s*$") 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 # TODO 4.0: just merge into __bytes__ (everywhere) 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 __bytes__(self): return self.asbytes() def __eq__(self, other): return isinstance(other, PKey) and self._fields == other._fields def __hash__(self): return hash(self._fields) @property def _fields(self): raise NotImplementedError 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 ` (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 ` containing the public part of the key. """ return u(encodebytes(self.asbytes())).replace("\n", "") def sign_ssh_data(self, data, algorithm=None): """ Sign a blob of data with this private key, and return a `.Message` representing an SSH signature message. :param bytes data: the data to sign. :param str algorithm: the signature algorithm to use, if different from the key's internal name. Default: ``None``. :return: an SSH signature `message <.Message>`. .. versionchanged:: 2.9 Added the ``algorithm`` kwarg. """ 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 bytes 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: the `bytes` that make 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() if not lines: raise SSHException("no lines in {} private key file".format(tag)) # find the BEGIN tag start = 0 m = self.BEGIN_TAG.match(lines[start]) line_range = len(lines) - 1 while start < line_range and not m: start += 1 m = self.BEGIN_TAG.match(lines[start]) start += 1 keytype = m.group(1) if m else None if start >= len(lines) or keytype is None: raise SSHException("not a valid {} private key file".format(tag)) # find the END tag end = start m = self.END_TAG.match(lines[end]) while end < line_range and not m: end += 1 m = self.END_TAG.match(lines[end]) if keytype == tag: data = self._read_private_key_pem(lines, end, password) pkformat = self._PRIVATE_KEY_FORMAT_ORIGINAL elif keytype == "OPENSSH": data = self._read_private_key_openssh(lines[start:end], password) pkformat = self._PRIVATE_KEY_FORMAT_OPENSSH else: raise SSHException( "encountered {} key, expected {} key".format(keytype, tag) ) return pkformat, data def _got_bad_key_format_id(self, id_): err = "{}._read_private_key() spat out an unknown key format id '{}'" raise SSHException(err.format(self.__class__.__name__, id_)) def _read_private_key_pem(self, lines, end, password): start = 0 # 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 # 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: {}".format(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 _read_private_key_openssh(self, lines, password): """ Read the new OpenSSH SSH2 private key format available since OpenSSH version 6.5 Reference: https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.key """ try: data = decodebytes(b("".join(lines))) except base64.binascii.Error as e: raise SSHException("base64 decoding error: {}".format(e)) # read data struct auth_magic = data[:15] if auth_magic != OPENSSH_AUTH_MAGIC: raise SSHException("unexpected OpenSSH key header encountered") cstruct = self._uint32_cstruct_unpack(data[15:], "sssur") cipher, kdfname, kdf_options, num_pubkeys, remainder = cstruct # For now, just support 1 key. if num_pubkeys > 1: raise SSHException( "unsupported: private keyfile has multiple keys" ) pubkey, privkey_blob = self._uint32_cstruct_unpack(remainder, "ss") if kdfname == b("bcrypt"): if cipher == b("aes256-cbc"): mode = modes.CBC elif cipher == b("aes256-ctr"): mode = modes.CTR else: raise SSHException( "unknown cipher `{}` used in private key file".format( cipher.decode("utf-8") ) ) # Encrypted private key. # 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" ) # Unpack salt and rounds from kdfoptions salt, rounds = self._uint32_cstruct_unpack(kdf_options, "su") # run bcrypt kdf to derive key and iv/nonce (32 + 16 bytes) key_iv = bcrypt.kdf( b(password), b(salt), 48, rounds, # We can't control how many rounds are on disk, so no sense # warning about it. ignore_few_rounds=True, ) key = key_iv[:32] iv = key_iv[32:] # decrypt private key blob decryptor = Cipher( algorithms.AES(key), mode(iv), default_backend() ).decryptor() decrypted_privkey = decryptor.update(privkey_blob) decrypted_privkey += decryptor.finalize() elif cipher == b("none") and kdfname == b("none"): # Unencrypted private key decrypted_privkey = privkey_blob else: raise SSHException( "unknown cipher or kdf used in private key file" ) # Unpack private key and verify checkints cstruct = self._uint32_cstruct_unpack(decrypted_privkey, "uusr") checkint1, checkint2, keytype, keydata = cstruct if checkint1 != checkint2: raise SSHException( "OpenSSH private key file checkints do not match" ) return _unpad_openssh(keydata) def _uint32_cstruct_unpack(self, data, strformat): """ Used to read new OpenSSH private key format. Unpacks a c data structure containing a mix of 32-bit uints and variable length strings prefixed by 32-bit uint size field, according to the specified format. Returns the unpacked vars in a tuple. Format strings: s - denotes a string i - denotes a long integer, encoded as a byte string u - denotes a 32-bit unsigned integer r - the remainder of the input string, returned as a string """ arr = [] idx = 0 try: for f in strformat: if f == "s": # string s_size = struct.unpack(">L", data[idx : idx + 4])[0] idx += 4 s = data[idx : idx + s_size] idx += s_size arr.append(s) if f == "i": # long integer s_size = struct.unpack(">L", data[idx : idx + 4])[0] idx += 4 s = data[idx : idx + s_size] idx += s_size i = util.inflate_long(s, True) arr.append(i) elif f == "u": # 32-bit unsigned int u = struct.unpack(">L", data[idx : idx + 4])[0] idx += 4 arr.append(u) elif f == "r": # remainder as string s = data[idx:] arr.append(s) break except Exception as e: # PKey-consuming code frequently wants to save-and-skip-over issues # with loading keys, and uses SSHException as the (really friggin # awful) signal for this. So for now...we do this. raise SSHException(str(e)) return tuple(arr) 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 bytes 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. with os.fdopen( os.open( filename, # 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. flags=os.O_WRONLY | os.O_TRUNC | os.O_CREAT, # 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). mode=o600, ), # Yea, you still gotta inform the FLO that it is in "write" mode. "w", ) as f: 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, str): key_types = [key_types] if isinstance(cert_types, str): 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: # [] # 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: """ 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 bytes 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