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## `paramiko/pkey.py` — `class:PKey` (lines 62-653)
```python
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,
},
}
_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
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 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 <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, algorithm=None):
"""
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.
: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 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()
# 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 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.
"""
with open(filename, "w") as f:
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
```
## `paramiko/pkey.py` — `function:PKey._write_private_key_file` (lines 546-563)
```python
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.
"""
with open(filename, "w") as f:
os.chmod(filename, o600)
self._write_private_key(f, key, format, password=password)
```
## `tests/test_pkey.py` — `module:<module>@26` (lines 26-26)
```python
from binascii import hexlify
```
## `tests/test_pkey.py` — `module:<module>@42` (lines 42-42)
```python
from mock import patch
```
## `tests/test_pkey.py` — `module:<module>@43` (lines 43-43)
```python
import pytest
```
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