# Copyright (c) 2022, Oracle and/or its affiliates.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License, version 2.0, as
# published by the Free Software Foundation.
#
# This program is also distributed with certain software (including
# but not limited to OpenSSL) that is licensed under separate terms,
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# documentation. The authors of MySQL hereby grant you an
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#
# Without limiting anything contained in the foregoing, this file,
# which is part of MySQL Connector/Python, is also subject to the
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#
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# See the GNU General Public License, version 2.0, for more details.
#
# You should have received a copy of the GNU General Public License
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# 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
"""LDAP SASL Authentication Plugin."""
import hmac
from base64 import b64decode, b64encode
from hashlib import sha1, sha256
from typing import Any, Callable, List, Optional, Tuple
from uuid import uuid4
from ..errors import InterfaceError, ProgrammingError
from ..logger import logger
from ..types import StrOrBytes
try:
import gssapi
except ImportError:
raise ProgrammingError(
"Module gssapi is required for GSSAPI authentication "
"mechanism but was not found. Unable to authenticate "
"with the server"
) from None
from ..utils import (
normalize_unicode_string as norm_ustr,
validate_normalized_unicode_string as valid_norm,
)
from . import BaseAuthPlugin
AUTHENTICATION_PLUGIN_CLASS = "MySQLLdapSaslPasswordAuthPlugin"
# pylint: disable=c-extension-no-member,no-member
class MySQLLdapSaslPasswordAuthPlugin(BaseAuthPlugin):
"""Class implementing the MySQL ldap sasl authentication plugin.
The MySQL's ldap sasl authentication plugin support two authentication
methods SCRAM-SHA-1 and GSSAPI (using Kerberos). This implementation only
support SCRAM-SHA-1 and SCRAM-SHA-256.
SCRAM-SHA-1 amd SCRAM-SHA-256
This method requires 2 messages from client and 2 responses from
server.
The first message from client will be generated by prepare_password(),
after receive the response from the server, it is required that this
response is passed back to auth_continue() which will return the
second message from the client. After send this second message to the
server, the second server respond needs to be passed to auth_finalize()
to finish the authentication process.
"""
sasl_mechanisms: List[str] = ["SCRAM-SHA-1", "SCRAM-SHA-256", "GSSAPI"]
requires_ssl: bool = False
plugin_name: str = "authentication_ldap_sasl_client"
def_digest_mode: Callable = sha1
client_nonce: Optional[str] = None
client_salt: Any = None
server_salt: Optional[str] = None
krb_service_principal: Optional[StrOrBytes] = None
iterations: int = 0
server_auth_var: Optional[str] = None
target_name: Optional[gssapi.Name] = None
ctx: gssapi.SecurityContext = None
servers_first: Optional[str] = None
server_nonce: Optional[str] = None
@staticmethod
def _xor(bytes1: bytes, bytes2: bytes) -> bytes:
return bytes([b1 ^ b2 for b1, b2 in zip(bytes1, bytes2)])
def _hmac(self, password: bytes, salt: bytes) -> bytes:
digest_maker = hmac.new(password, salt, self.def_digest_mode)
return digest_maker.digest()
def _hi(self, password: str, salt: bytes, count: int) -> bytes:
"""Prepares Hi
Hi(password, salt, iterations) where Hi(p,s,i) is defined as
PBKDF2 (HMAC, p, s, i, output length of H).
"""
pw = password.encode()
hi = self._hmac(pw, salt + b"\x00\x00\x00\x01")
aux = hi
for _ in range(count - 1):
aux = self._hmac(pw, aux)
hi = self._xor(hi, aux)
return hi
@staticmethod
def _normalize(string: str) -> str:
norm_str = norm_ustr(string)
broken_rule = valid_norm(norm_str)
if broken_rule is not None:
raise InterfaceError(f"broken_rule: {broken_rule}")
return norm_str
def _first_message(self) -> bytes:
"""This method generates the first message to the server to start the
The client-first message consists of a gs2-header,
the desired username, and a randomly generated client nonce cnonce.
The first message from the server has the form:
b'n,a=<user_name>,n=<user_name>,r=<client_nonce>
Returns client's first message
"""
cfm_fprnat = "n,a={user_name},n={user_name},r={client_nonce}"
self.client_nonce = str(uuid4()).replace("-", "")
cfm: StrOrBytes = cfm_fprnat.format(
user_name=self._normalize(self._username),
client_nonce=self.client_nonce,
)
if isinstance(cfm, str):
cfm = cfm.encode("utf8")
return cfm
def _first_message_krb(self) -> Optional[bytes]:
"""Get a TGT Authentication request and initiates security context.
This method will contact the Kerberos KDC in order of obtain a TGT.
"""
user_name = gssapi.raw.names.import_name(
self._username.encode("utf8"), name_type=gssapi.NameType.user
)
# Use defaults store = {'ccache': 'FILE:/tmp/krb5cc_1000'}#,
# 'keytab':'/etc/some.keytab' }
# Attempt to retrieve credential from default cache file.
try:
cred: Any = gssapi.Credentials()
logger.debug(
"# Stored credentials found, if password was given it will be ignored."
)
try:
# validate credentials has not expired.
cred.lifetime
except gssapi.raw.exceptions.ExpiredCredentialsError as err:
logger.warning(" Credentials has expired: %s", err)
cred.acquire(user_name)
raise InterfaceError(f"Credentials has expired: {err}") from err
except gssapi.raw.misc.GSSError as err:
if not self._password:
raise InterfaceError(
f"Unable to retrieve stored credentials error: {err}"
) from err
try:
logger.debug("# Attempt to retrieve credentials with given password")
acquire_cred_result = gssapi.raw.acquire_cred_with_password(
user_name,
self._password.encode("utf8"),
usage="initiate",
)
cred = acquire_cred_result[0]
except gssapi.raw.misc.GSSError as err2:
raise ProgrammingError(
f"Unable to retrieve credentials with the given password: {err2}"
) from err
flags_l = (
gssapi.RequirementFlag.mutual_authentication,
gssapi.RequirementFlag.extended_error,
gssapi.RequirementFlag.delegate_to_peer,
)
if self.krb_service_principal:
service_principal = self.krb_service_principal
else:
service_principal = "ldap/ldapauth"
logger.debug("# service principal: %s", service_principal)
servk = gssapi.Name(
service_principal, name_type=gssapi.NameType.kerberos_principal
)
self.target_name = servk
self.ctx = gssapi.SecurityContext(
name=servk, creds=cred, flags=sum(flags_l), usage="initiate"
)
try:
# step() returns bytes | None, see documentation,
# so this method could return a NULL payload.
# ref: https://pythongssapi.github.io/<suffix>
# suffix: python-gssapi/latest/gssapi.html#gssapi.sec_contexts.SecurityContext
initial_client_token = self.ctx.step()
except gssapi.raw.misc.GSSError as err:
raise InterfaceError(f"Unable to initiate security context: {err}") from err
logger.debug("# initial client token: %s", initial_client_token)
return initial_client_token
def auth_continue_krb(
self, tgt_auth_challenge: Optional[bytes]
) -> Tuple[Optional[bytes], bool]:
"""Continue with the Kerberos TGT service request.
With the TGT authentication service given response generate a TGT
service request. This method must be invoked sequentially (in a loop)
until the security context is completed and an empty response needs to
be send to acknowledge the server.
Args:
tgt_auth_challenge the challenge for the negotiation.
Returns: tuple (bytearray TGS service request,
bool True if context is completed otherwise False).
"""
logger.debug("tgt_auth challenge: %s", tgt_auth_challenge)
resp = self.ctx.step(tgt_auth_challenge)
logger.debug("# context step response: %s", resp)
logger.debug("# context completed?: %s", self.ctx.complete)
return resp, self.ctx.complete
def auth_accept_close_handshake(self, message: bytes) -> bytes:
"""Accept handshake and generate closing handshake message for server.
This method verifies the server authenticity from the given message
and included signature and generates the closing handshake for the
server.
When this method is invoked the security context is already established
and the client and server can send GSSAPI formated secure messages.
To finish the authentication handshake the server sends a message
with the security layer availability and the maximum buffer size.
Since the connector only uses the GSSAPI authentication mechanism to
authenticate the user with the server, the server will verify clients
message signature and terminate the GSSAPI authentication and send two
messages; an authentication acceptance b'\x01\x00\x00\x08\x01' and a
OK packet (that must be received after sent the returned message from
this method).
Args:
message a wrapped hssapi message from the server.
Returns: bytearray closing handshake message to be send to the server.
"""
if not self.ctx.complete:
raise ProgrammingError("Security context is not completed.")
logger.debug("# servers message: %s", message)
logger.debug("# GSSAPI flags in use: %s", self.ctx.actual_flags)
try:
unwraped = self.ctx.unwrap(message)
logger.debug("# unwraped: %s", unwraped)
except gssapi.raw.exceptions.BadMICError as err:
raise InterfaceError(f"Unable to unwrap server message: {err}") from err
logger.debug("# unwrapped server message: %s", unwraped)
# The message contents for the clients closing message:
# - security level 1 byte, must be always 1.
# - conciliated buffer size 3 bytes, without importance as no
# further GSSAPI messages will be sends.
response = bytearray(b"\x01\x00\x00\00")
# Closing handshake must not be encrypted.
logger.debug("# message response: %s", response)
wraped = self.ctx.wrap(response, encrypt=False)
logger.debug(
"# wrapped message response: %s, length: %d",
wraped[0],
len(wraped[0]),
)
return wraped.message
def auth_response( # type: ignore[override]
self,
auth_data: Optional[str] = None,
) -> Optional[bytes]:
"""This method will prepare the fist message to the server.
Returns bytes to send to the server as the first message.
"""
krb_service_principal = auth_data
auth_mechanism = self._auth_data.decode()
self.krb_service_principal = krb_service_principal
logger.debug("read_method_name_from_server: %s", auth_mechanism)
if auth_mechanism not in self.sasl_mechanisms:
auth_mechanisms = '", "'.join(self.sasl_mechanisms[:-1])
raise InterfaceError(
f'The sasl authentication method "{auth_mechanism}" requested '
f'from the server is not supported. Only "{auth_mechanisms}" '
f'and "{self.sasl_mechanisms[-1]}" are supported'
)
if b"GSSAPI" in self._auth_data:
return self._first_message_krb()
if self._auth_data == b"SCRAM-SHA-256":
self.def_digest_mode = sha256
return self._first_message()
def _second_message(self) -> bytes:
"""This method generates the second message to the server
Second message consist on the concatenation of the client and the
server nonce, and cproof.
c=<n,a=<user_name>>,r=<server_nonce>,p=<client_proof>
where:
<client_proof>: xor(<client_key>, <client_signature>)
<client_key>: hmac(salted_password, b"Client Key")
<client_signature>: hmac(<stored_key>, <auth_msg>)
<stored_key>: h(<client_key>)
<auth_msg>: <client_first_no_header>,<servers_first>,
c=<client_header>,r=<server_nonce>
<client_first_no_header>: n=<username>r=<client_nonce>
"""
if not self._auth_data:
raise InterfaceError("Missing authentication data (seed)")
passw = self._normalize(self._password)
salted_password = self._hi(passw, b64decode(self.server_salt), self.iterations)
logger.debug("salted_password: %s", b64encode(salted_password).decode())
client_key = self._hmac(salted_password, b"Client Key")
logger.debug("client_key: %s", b64encode(client_key).decode())
stored_key = self.def_digest_mode(client_key).digest()
logger.debug("stored_key: %s", b64encode(stored_key).decode())
server_key = self._hmac(salted_password, b"Server Key")
logger.debug("server_key: %s", b64encode(server_key).decode())
client_first_no_header = ",".join(
[
f"n={self._normalize(self._username)}",
f"r={self.client_nonce}",
]
)
logger.debug("client_first_no_header: %s", client_first_no_header)
client_header = b64encode(
f"n,a={self._normalize(self._username)},".encode()
).decode()
auth_msg = ",".join(
[
client_first_no_header,
self.servers_first,
f"c={client_header}",
f"r={self.server_nonce}",
]
)
logger.debug("auth_msg: %s", auth_msg)
client_signature = self._hmac(stored_key, auth_msg.encode())
logger.debug("client_signature: %s", b64encode(client_signature).decode())
client_proof = self._xor(client_key, client_signature)
logger.debug("client_proof: %s", b64encode(client_proof).decode())
self.server_auth_var = b64encode(
self._hmac(server_key, auth_msg.encode())
).decode()
logger.debug("server_auth_var: %s", self.server_auth_var)
msg = ",".join(
[
f"c={client_header}",
f"r={self.server_nonce}",
f"p={b64encode(client_proof).decode()}",
]
)
logger.debug("second_message: %s", msg)
return msg.encode()
def _validate_first_reponse(self, servers_first: bytes) -> None:
"""Validates first message from the server.
Extracts the server's salt and iterations from the servers 1st response.
First message from the server is in the form:
<server_salt>,i=<iterations>
"""
if not servers_first or not isinstance(servers_first, (bytearray, bytes)):
raise InterfaceError(f"Unexpected server message: {repr(servers_first)}")
try:
servers_first_str = servers_first.decode()
self.servers_first = servers_first_str
r_server_nonce, s_salt, i_counter = servers_first_str.split(",")
except ValueError:
raise InterfaceError(
f"Unexpected server message: {servers_first_str}"
) from None
if (
not r_server_nonce.startswith("r=")
or not s_salt.startswith("s=")
or not i_counter.startswith("i=")
):
raise InterfaceError(
f"Incomplete reponse from the server: {servers_first_str}"
)
if self.client_nonce in r_server_nonce:
self.server_nonce = r_server_nonce[2:]
logger.debug("server_nonce: %s", self.server_nonce)
else:
raise InterfaceError(
"Unable to authenticate response: response not well formed "
f"{servers_first_str}"
)
self.server_salt = s_salt[2:]
logger.debug(
"server_salt: %s length: %s",
self.server_salt,
len(self.server_salt),
)
try:
i_counter = i_counter[2:]
logger.debug("iterations: %s", i_counter)
self.iterations = int(i_counter)
except Exception as err:
raise InterfaceError(
f"Unable to authenticate: iterations not found {servers_first_str}"
) from err
def auth_continue(self, servers_first_response: bytes) -> bytes:
"""return the second message from the client.
Returns bytes to send to the server as the second message.
"""
self._validate_first_reponse(servers_first_response)
return self._second_message()
def _validate_second_reponse(self, servers_second: bytearray) -> bool:
"""Validates second message from the server.
The client and the server prove to each other they have the same Auth
variable.
The second message from the server consist of the server's proof:
server_proof = HMAC(<server_key>, <auth_msg>)
where:
<server_key>: hmac(<salted_password>, b"Server Key")
<auth_msg>: <client_first_no_header>,<servers_first>,
c=<client_header>,r=<server_nonce>
Our server_proof must be equal to the Auth variable send on this second
response.
"""
if (
not servers_second
or not isinstance(servers_second, bytearray)
or len(servers_second) <= 2
or not servers_second.startswith(b"v=")
):
raise InterfaceError("The server's proof is not well formated")
server_var = servers_second[2:].decode()
logger.debug("server auth variable: %s", server_var)
return self.server_auth_var == server_var
def auth_finalize(self, servers_second_response: bytearray) -> bool:
"""finalize the authentication process.
Raises InterfaceError if the ervers_second_response is invalid.
Returns True in successful authentication False otherwise.
"""
if not self._validate_second_reponse(servers_second_response):
raise InterfaceError(
"Authentication failed: Unable to proof server identity"
)
return True
# pylint: enable=c-extension-no-member,no-member