models.py

"""OAuth Provider Models"""
import base64
import binascii
import json
import time
from dataclasses import asdict, dataclass, field
from datetime import datetime
from hashlib import sha256
from typing import Any, Optional
from urllib.parse import urlparse, urlunparse

from cryptography.hazmat.primitives.asymmetric.ec import EllipticCurvePrivateKey
from cryptography.hazmat.primitives.asymmetric.rsa import RSAPrivateKey
from dacite import from_dict
from django.db import models
from django.http import HttpRequest
from django.utils import dateformat, timezone
from django.utils.translation import gettext_lazy as _
from jwt import encode
from rest_framework.serializers import Serializer

from authentik.core.models import ExpiringModel, PropertyMapping, Provider, User
from authentik.crypto.models import CertificateKeyPair
from authentik.events.models import Event, EventAction
from authentik.events.utils import get_user
from authentik.lib.generators import generate_id, generate_key
from authentik.lib.utils.time import timedelta_from_string, timedelta_string_validator
from authentik.providers.oauth2.apps import AuthentikProviderOAuth2Config
from authentik.providers.oauth2.constants import ACR_AUTHENTIK_DEFAULT


class ClientTypes(models.TextChoices):
    """Confidential clients are capable of maintaining the confidentiality
    of their credentials. Public clients are incapable."""

    CONFIDENTIAL = "confidential", _("Confidential")
    PUBLIC = "public", _("Public")


class GrantTypes(models.TextChoices):
    """OAuth2 Grant types we support"""

    AUTHORIZATION_CODE = "authorization_code"
    IMPLICIT = "implicit"
    HYBRID = "hybrid"


class ResponseMode(models.TextChoices):
    """https://openid.net/specs/oauth-v2-multiple-response-types-1_0.html#OAuth.Post"""

    QUERY = "query"
    FRAGMENT = "fragment"


class SubModes(models.TextChoices):
    """Mode after which 'sub' attribute is generateed, for compatibility reasons"""

    HASHED_USER_ID = "hashed_user_id", _("Based on the Hashed User ID")
    USER_USERNAME = "user_username", _("Based on the username")
    USER_EMAIL = (
        "user_email",
        _("Based on the User's Email. This is recommended over the UPN method."),
    )
    USER_UPN = (
        "user_upn",
        _(
            (
                "Based on the User's UPN, only works if user has a 'upn' attribute set. "
                "Use this method only if you have different UPN and Mail domains."
            )
        ),
    )


class IssuerMode(models.TextChoices):
    """Configure how the `iss` field is created."""

    GLOBAL = "global", _("Same identifier is used for all providers")
    PER_PROVIDER = "per_provider", _(
        "Each provider has a different issuer, based on the application slug."
    )


class ResponseTypes(models.TextChoices):
    """Response Type required by the client."""

    CODE = "code", _("code (Authorization Code Flow)")
    ID_TOKEN = "id_token", _("id_token (Implicit Flow)")
    ID_TOKEN_TOKEN = "id_token token", _("id_token token (Implicit Flow)")
    CODE_TOKEN = "code token", _("code token (Hybrid Flow)")
    CODE_ID_TOKEN = "code id_token", _("code id_token (Hybrid Flow)")
    CODE_ID_TOKEN_TOKEN = "code id_token token", _("code id_token token (Hybrid Flow)")


class JWTAlgorithms(models.TextChoices):
    """Algorithm used to sign the JWT Token"""

    HS256 = "HS256", _("HS256 (Symmetric Encryption)")
    RS256 = "RS256", _("RS256 (Asymmetric Encryption)")
    EC256 = "EC256", _("EC256 (Asymmetric Encryption)")


class ScopeMapping(PropertyMapping):
    """Map an OAuth Scope to users properties"""

    scope_name = models.TextField(help_text=_("Scope used by the client"))
    description = models.TextField(
        blank=True,
        help_text=_(
            (
                "Description shown to the user when consenting. "
                "If left empty, the user won't be informed."
            )
        ),
    )

    @property
    def component(self) -> str:
        return "ak-property-mapping-scope-form"

    @property
    def serializer(self) -> type[Serializer]:
        from authentik.providers.oauth2.api.scope import ScopeMappingSerializer

        return ScopeMappingSerializer

    def __str__(self):
        return f"Scope Mapping {self.name} ({self.scope_name})"

    class Meta:

        verbose_name = _("Scope Mapping")
        verbose_name_plural = _("Scope Mappings")


class OAuth2Provider(Provider):
    """OAuth2 Provider for generic OAuth and OpenID Connect Applications."""

    client_type = models.CharField(
        max_length=30,
        choices=ClientTypes.choices,
        default=ClientTypes.CONFIDENTIAL,
        verbose_name=_("Client Type"),
        help_text=_(ClientTypes.__doc__),
    )
    client_id = models.CharField(
        max_length=255,
        unique=True,
        verbose_name=_("Client ID"),
        default=generate_id,
    )
    client_secret = models.CharField(
        max_length=255,
        blank=True,
        verbose_name=_("Client Secret"),
        default=generate_key,
    )
    redirect_uris = models.TextField(
        default="",
        blank=True,
        verbose_name=_("Redirect URIs"),
        help_text=_("Enter each URI on a new line."),
    )

    include_claims_in_id_token = models.BooleanField(
        default=True,
        verbose_name=_("Include claims in id_token"),
        help_text=_(
            (
                "Include User claims from scopes in the id_token, for applications "
                "that don't access the userinfo endpoint."
            )
        ),
    )

    access_code_validity = models.TextField(
        default="minutes=1",
        validators=[timedelta_string_validator],
        help_text=_(
            (
                "Access codes not valid on or after current time + this value "
                "(Format: hours=1;minutes=2;seconds=3)."
            )
        ),
    )
    token_validity = models.TextField(
        default="days=30",
        validators=[timedelta_string_validator],
        help_text=_(
            (
                "Tokens not valid on or after current time + this value "
                "(Format: hours=1;minutes=2;seconds=3)."
            )
        ),
    )

    sub_mode = models.TextField(
        choices=SubModes.choices,
        default=SubModes.HASHED_USER_ID,
        help_text=_(
            (
                "Configure what data should be used as unique User Identifier. For most cases, "
                "the default should be fine."
            )
        ),
    )
    issuer_mode = models.TextField(
        choices=IssuerMode.choices,
        default=IssuerMode.PER_PROVIDER,
        help_text=_(("Configure how the issuer field of the ID Token should be filled.")),
    )

    signing_key = models.ForeignKey(
        CertificateKeyPair,
        verbose_name=_("Signing Key"),
        on_delete=models.SET_NULL,
        null=True,
        help_text=_(
            "Key used to sign the tokens. Only required when JWT Algorithm is set to RS256."
        ),
    )

    verification_keys = models.ManyToManyField(
        CertificateKeyPair,
        verbose_name=_("Allowed certificates for JWT-based client_credentials"),
        help_text=_(
            "JWTs created with the configured certificates can authenticate with this provider."
        ),
        related_name="+",
        default=None,
        blank=True,
    )

    def create_refresh_token(
        self, user: User, scope: list[str], request: HttpRequest
    ) -> "RefreshToken":
        """Create and populate a RefreshToken object."""
        token = RefreshToken(
            user=user,
            provider=self,
            refresh_token=generate_key(),
            expires=timezone.now() + timedelta_from_string(self.token_validity),
            scope=scope,
        )
        token.access_token = token.create_access_token(user, request)
        return token

    def get_jwt_key(self) -> tuple[str, str]:
        """Get either the configured certificate or the client secret"""
        if not self.signing_key:
            # No Certificate at all, assume HS256
            return self.client_secret, JWTAlgorithms.HS256
        key: CertificateKeyPair = self.signing_key
        private_key = key.private_key
        if isinstance(private_key, RSAPrivateKey):
            return key.key_data, JWTAlgorithms.RS256
        if isinstance(private_key, EllipticCurvePrivateKey):
            return key.key_data, JWTAlgorithms.EC256
        raise Exception(f"Invalid private key type: {type(private_key)}")

    def get_issuer(self, request: HttpRequest) -> Optional[str]:
        """Get issuer, based on request"""
        if self.issuer_mode == IssuerMode.GLOBAL:
            return request.build_absolute_uri("/")
        try:
            mountpoint = AuthentikProviderOAuth2Config.mountpoints[
                "authentik.providers.oauth2.urls"
            ]
            # pylint: disable=no-member
            return request.build_absolute_uri(f"/{mountpoint}{self.application.slug}/")
        except Provider.application.RelatedObjectDoesNotExist:
            return None

    @property
    def launch_url(self) -> Optional[str]:
        """Guess launch_url based on first redirect_uri"""
        if self.redirect_uris == "":
            return None
        main_url = self.redirect_uris.split("\n", maxsplit=1)[0]
        launch_url = urlparse(main_url)._replace(path="")
        return urlunparse(launch_url)

    @property
    def component(self) -> str:
        return "ak-provider-oauth2-form"

    @property
    def serializer(self) -> type[Serializer]:
        from authentik.providers.oauth2.api.provider import OAuth2ProviderSerializer

        return OAuth2ProviderSerializer

    def __str__(self):
        return f"OAuth2 Provider {self.name}"

    def encode(self, payload: dict[str, Any]) -> str:
        """Represent the ID Token as a JSON Web Token (JWT)."""
        headers = {}
        if self.signing_key:
            headers["kid"] = self.signing_key.kid
        key, alg = self.get_jwt_key()
        # If the provider does not have an RSA Key assigned, it was switched to Symmetric
        self.refresh_from_db()
        # pyright: reportGeneralTypeIssues=false
        return encode(payload, key, algorithm=alg, headers=headers)

    class Meta:

        verbose_name = _("OAuth2/OpenID Provider")
        verbose_name_plural = _("OAuth2/OpenID Providers")


class BaseGrantModel(models.Model):
    """Base Model for all grants"""

    provider = models.ForeignKey(OAuth2Provider, on_delete=models.CASCADE)
    user = models.ForeignKey(User, verbose_name=_("User"), on_delete=models.CASCADE)
    _scope = models.TextField(default="", verbose_name=_("Scopes"))
    revoked = models.BooleanField(default=False)

    @property
    def scope(self) -> list[str]:
        """Return scopes as list of strings"""
        return self._scope.split()

    @scope.setter
    def scope(self, value):
        self._scope = " ".join(value)

    class Meta:
        abstract = True


class AuthorizationCode(ExpiringModel, BaseGrantModel):
    """OAuth2 Authorization Code"""

    code = models.CharField(max_length=255, unique=True, verbose_name=_("Code"))
    nonce = models.TextField(null=True, default=None, verbose_name=_("Nonce"))
    is_open_id = models.BooleanField(default=False, verbose_name=_("Is Authentication?"))
    code_challenge = models.CharField(max_length=255, null=True, verbose_name=_("Code Challenge"))
    code_challenge_method = models.CharField(
        max_length=255, null=True, verbose_name=_("Code Challenge Method")
    )

    @property
    def c_hash(self):
        """https://openid.net/specs/openid-connect-core-1_0.html#IDToken"""
        hashed_code = sha256(self.code.encode("ascii")).hexdigest().encode("ascii")
        return (
            base64.urlsafe_b64encode(binascii.unhexlify(hashed_code[: len(hashed_code) // 2]))
            .rstrip(b"=")
            .decode("ascii")
        )

    class Meta:
        verbose_name = _("Authorization Code")
        verbose_name_plural = _("Authorization Codes")

    def __str__(self):
        return f"Authorization code for {self.provider} for user {self.user}"


@dataclass
class IDToken:
    """The primary extension that OpenID Connect makes to OAuth 2.0 to enable End-Users to be
    Authenticated is the ID Token data structure. The ID Token is a security token that contains
    Claims about the Authentication of an End-User by an Authorization Server when using a Client,
    and potentially other requested Claims. The ID Token is represented as a
    JSON Web Token (JWT) [JWT].

    https://openid.net/specs/openid-connect-core-1_0.html#IDToken"""

    # All these fields need to optional so we can save an empty IDToken for non-OpenID flows.
    iss: Optional[str] = None
    sub: Optional[str] = None
    aud: Optional[str] = None
    exp: Optional[int] = None
    iat: Optional[int] = None
    auth_time: Optional[int] = None
    acr: Optional[str] = ACR_AUTHENTIK_DEFAULT

    c_hash: Optional[str] = None

    nonce: Optional[str] = None
    at_hash: Optional[str] = None

    claims: dict[str, Any] = field(default_factory=dict)

    def to_dict(self) -> dict[str, Any]:
        """Convert dataclass to dict, and update with keys from `claims`"""
        dic = asdict(self)
        dic.pop("claims")
        dic.update(self.claims)
        return dic


class RefreshToken(ExpiringModel, BaseGrantModel):
    """OAuth2 Refresh Token"""

    access_token = models.TextField(verbose_name=_("Access Token"))
    refresh_token = models.CharField(max_length=255, unique=True, verbose_name=_("Refresh Token"))
    _id_token = models.TextField(verbose_name=_("ID Token"))

    class Meta:
        verbose_name = _("OAuth2 Token")
        verbose_name_plural = _("OAuth2 Tokens")

    @property
    def id_token(self) -> IDToken:
        """Load ID Token from json"""
        if self._id_token:
            raw_token = json.loads(self._id_token)
            return from_dict(IDToken, raw_token)
        return IDToken()

    @id_token.setter
    def id_token(self, value: IDToken):
        self._id_token = json.dumps(asdict(value))

    def __str__(self):
        return f"Refresh Token for {self.provider} for user {self.user}"

    @property
    def at_hash(self):
        """Get hashed access_token"""
        hashed_access_token = sha256(self.access_token.encode("ascii")).hexdigest().encode("ascii")
        return (
            base64.urlsafe_b64encode(
                binascii.unhexlify(hashed_access_token[: len(hashed_access_token) // 2])
            )
            .rstrip(b"=")
            .decode("ascii")
        )

    def create_access_token(self, user: User, request: HttpRequest) -> str:
        """Create access token with a similar format as Okta, Keycloak, ADFS"""
        token = self.create_id_token(user, request).to_dict()
        token["cid"] = self.provider.client_id
        token["uid"] = generate_key()
        return self.provider.encode(token)

    def create_id_token(self, user: User, request: HttpRequest) -> IDToken:
        """Creates the id_token.
        See: http://openid.net/specs/openid-connect-core-1_0.html#IDToken"""
        sub = ""
        if self.provider.sub_mode == SubModes.HASHED_USER_ID:
            sub = user.uid
        elif self.provider.sub_mode == SubModes.USER_EMAIL:
            sub = user.email
        elif self.provider.sub_mode == SubModes.USER_USERNAME:
            sub = user.username
        elif self.provider.sub_mode == SubModes.USER_UPN:
            sub = user.attributes.get("upn", user.uid)
        else:
            raise ValueError(
                (
                    f"Provider {self.provider} has invalid sub_mode "
                    f"selected: {self.provider.sub_mode}"
                )
            )

        # Convert datetimes into timestamps.
        now = int(time.time())
        iat_time = now
        exp_time = int(dateformat.format(self.expires, "U"))
        # We use the timestamp of the user's last successful login (EventAction.LOGIN) for auth_time
        auth_events = Event.objects.filter(action=EventAction.LOGIN, user=get_user(user)).order_by(
            "-created"
        )
        # Fallback in case we can't find any login events
        auth_time = datetime.now()
        if auth_events.exists():
            auth_time = auth_events.first().created
        auth_time = int(dateformat.format(auth_time, "U"))

        token = IDToken(
            iss=self.provider.get_issuer(request),
            sub=sub,
            aud=self.provider.client_id,
            exp=exp_time,
            iat=iat_time,
            auth_time=auth_time,
        )

        # Include (or not) user standard claims in the id_token.
        if self.provider.include_claims_in_id_token:
            from authentik.providers.oauth2.views.userinfo import UserInfoView

            user_info = UserInfoView()
            user_info.request = request
            claims = user_info.get_claims(self)
            token.claims = claims

        return token