|
| 1 | +import base64 |
| 2 | +import os |
| 3 | +import platform |
| 4 | +from typing import Final, Optional |
| 5 | + |
| 6 | +sspi = None |
| 7 | +gssapi = None |
| 8 | +PLATFORM = platform.system() |
| 9 | +TOKEN_PREFIX: Final = "_KERBEROSAUTH_" |
| 10 | + |
| 11 | + |
| 12 | +# For Windows SSPI token generation: |
| 13 | +if PLATFORM == "Windows": |
| 14 | + import sspi |
| 15 | +else: |
| 16 | + import gssapi |
| 17 | + |
| 18 | + |
| 19 | +class KerberosTokenProvider: |
| 20 | + def __init__( |
| 21 | + self, |
| 22 | + host: str, |
| 23 | + realm: Optional[str] = None, |
| 24 | + realm_user: Optional[str] = None, |
| 25 | + krb5_path: Optional[str] = None, |
| 26 | + ticket_cache: Optional[str] = None, |
| 27 | + krb5_mech: Optional[str] = None, |
| 28 | + ): |
| 29 | + self.host = host |
| 30 | + self.realm = realm |
| 31 | + self.realm_user = realm_user |
| 32 | + self.krb5_path = krb5_path |
| 33 | + self.ticket_cache = ticket_cache |
| 34 | + self.krb5_mech = krb5_mech |
| 35 | + |
| 36 | + if PLATFORM != "Windows": |
| 37 | + missing = [] |
| 38 | + if not self.realm: |
| 39 | + missing.append("realm") |
| 40 | + if not self.realm_user: |
| 41 | + missing.append("realm_user") |
| 42 | + if not self.krb5_path: |
| 43 | + missing.append("krb5_path") |
| 44 | + if missing: |
| 45 | + raise ValueError(f"Missing required parameters: {', '.join(missing)}") |
| 46 | + |
| 47 | + def get_token(self) -> str: |
| 48 | + return self._refresh_token() |
| 49 | + |
| 50 | + def _refresh_token(self) -> str: |
| 51 | + if PLATFORM == "Windows": |
| 52 | + return self._refresh_token_windows() |
| 53 | + else: |
| 54 | + return self._refresh_token_unix() |
| 55 | + |
| 56 | + def _format_token(self, token: bytes) -> str: |
| 57 | + token_b64 = base64.b64encode(token).decode("utf-8") |
| 58 | + return TOKEN_PREFIX + token_b64 |
| 59 | + |
| 60 | + def _refresh_token_windows(self) -> str: |
| 61 | + target = f"krbsvr400/{self.host}" |
| 62 | + client = sspi.ClientAuth("Kerberos", targetspn=target) |
| 63 | + |
| 64 | + err, out_buffer = client.authorize(None) |
| 65 | + if err != 0: |
| 66 | + raise RuntimeError(f"Windows SSPI error when attempting Kerberos login: {hex(err)}") |
| 67 | + |
| 68 | + token = out_buffer[0].Buffer |
| 69 | + return self._format_token(token) |
| 70 | + |
| 71 | + def _refresh_token_unix(self) -> str: |
| 72 | + os.environ["KRB5_CONFIG"] = self.krb5_path |
| 73 | + if self.ticket_cache: |
| 74 | + os.environ["KRB5CCNAME"] = self.ticket_cache |
| 75 | + |
| 76 | + mech = ( |
| 77 | + gssapi.OID.from_int_seq("1.2.840.113554.1.2.2") |
| 78 | + if self.krb5_mech is None |
| 79 | + else gssapi.OID.from_int_seq(self.krb5_mech) |
| 80 | + ) |
| 81 | + |
| 82 | + try: |
| 83 | + user_name = gssapi.Name( |
| 84 | + f"{self.realm_user}@{self.realm}", name_type=gssapi.NameType.user |
| 85 | + ) |
| 86 | + cred = gssapi.Credentials(name=user_name, usage="initiate", mechs=[mech]) |
| 87 | + server_name = gssapi.Name( |
| 88 | + f"krbsvr400@{self.host}", name_type=gssapi.NameType.hostbased_service |
| 89 | + ) |
| 90 | + ctx = gssapi.SecurityContext(name=server_name, mech=mech, creds=cred, usage="initiate") |
| 91 | + |
| 92 | + token = ctx.step(b"") |
| 93 | + if token is None: |
| 94 | + raise RuntimeError( |
| 95 | + "Failed to generate Kerberos token. No token returned from GSSAPI context." |
| 96 | + ) |
| 97 | + except gssapi.exceptions.GSSError as e: |
| 98 | + if "No credentials were supplied" in str(e) or "Unavailable" in str(e): |
| 99 | + raise RuntimeError("No valid TGT found in credential cache.") |
| 100 | + raise RuntimeError( |
| 101 | + f"Kerberos token generation error when attempting Kerberos login: {str(e)}" |
| 102 | + ) |
| 103 | + |
| 104 | + return self._format_token(token) |
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