security-alert-center/backend/app/services/rdg_workstation_session.py

"""Correlate RDG 303/303-failed with workstation rdp.login.success (1149)."""

from __future__ import annotations

from sqlalchemy import select
from sqlalchemy.orm import Session
from sqlalchemy.orm.attributes import flag_modified

from app.models import Event
from app.services.host_sessions import (
    SESSION_TERMINATED_AT_KEY,
    _details_dict,
    _event_login_user,
)
from app.services.rdg_client_host import find_windows_host_by_ipv4
from app.services.rdg_session_flap import (
    RDG_END_TYPES,
    _event_user,
    event_internal_ip,
    find_rdg_success_before_end,
)

SESSION_CLOSED_BY_RDG_AT_KEY = "session_closed_by_rdg_at"
SESSION_CLOSED_BY_RDG_EVENT_ID_KEY = "session_closed_by_rdg_event_id"

WORKSTATION_LOGIN_TYPE = "rdp.login.success"


def normalize_sam_account(user: str) -> str:
    text = (user or "").strip()
    if "\\" in text:
        return text.split("\\")[-1].strip().casefold()
    if "@" in text:
        return text.split("@")[0].strip().casefold()
    return text.casefold()


def users_match_rdg(login_user: str, rdg_user: str) -> bool:
    left = normalize_sam_account(login_user)
    right = normalize_sam_account(rdg_user)
    return bool(left and right and left == right)


def event_closed_by_rdg(event: Event) -> bool:
    details = _details_dict(event)
    at = details.get(SESSION_CLOSED_BY_RDG_AT_KEY)
    return at is not None and str(at).strip() != ""


def mark_login_closed_by_rdg(login_event: Event, *, rdg_end_event: Event) -> None:
    details = dict(_details_dict(login_event))
    details[SESSION_CLOSED_BY_RDG_AT_KEY] = rdg_end_event.occurred_at.isoformat()
    details[SESSION_CLOSED_BY_RDG_EVENT_ID_KEY] = rdg_end_event.id
    login_event.details = details
    flag_modified(login_event, "details")


def _login_already_closed(login_event: Event) -> bool:
    details = _details_dict(login_event)
    if details.get("session_terminated") is True:
        return True
    at = details.get(SESSION_TERMINATED_AT_KEY)
    if at is not None and str(at).strip() != "":
        return True
    return event_closed_by_rdg(login_event)


def find_workstation_login_for_rdg_end(db: Session, rdg_end_event: Event) -> Event | None:
    if rdg_end_event.type not in RDG_END_TYPES:
        return None
    internal_ip = event_internal_ip(rdg_end_event)
    if not internal_ip:
        return None
    client_host = find_windows_host_by_ipv4(db, internal_ip)
    if client_host is None:
        return None

    rdg_user = _event_user(rdg_end_event)
    if not rdg_user:
        return None
    end_at = rdg_end_event.occurred_at

    candidates = db.scalars(
        select(Event)
        .where(
            Event.host_id == client_host.id,
            Event.type == WORKSTATION_LOGIN_TYPE,
            Event.occurred_at <= end_at,
            Event.id != rdg_end_event.id,
        )
        .order_by(Event.occurred_at.desc())
    ).all()

    for login in candidates:
        if _login_already_closed(login):
            continue
        login_user = _event_login_user(login)
        if not users_match_rdg(login_user, rdg_user):
            continue
        return login
    return None


def find_rdg_end_after_workstation_login(db: Session, login_event: Event) -> Event | None:
    """Runtime lookup for historical events without persisted close flag."""
    if login_event.type != WORKSTATION_LOGIN_TYPE:
        return None
    if _login_already_closed(login_event):
        return None

    host = login_event.host
    if host is None or not host.ipv4:
        return None

    workstation_ip = host.ipv4.strip()
    login_user = _event_login_user(login_event)
    if not login_user:
        return None
    login_at = login_event.occurred_at

    candidates = db.scalars(
        select(Event)
        .where(
            Event.type.in_(RDG_END_TYPES),
            Event.occurred_at >= login_at,
            Event.id != login_event.id,
        )
        .order_by(Event.occurred_at.asc())
    ).all()

    for end in candidates:
        if event_internal_ip(end) != workstation_ip:
            continue
        if not users_match_rdg(_event_user(end), login_user):
            continue
        if find_rdg_success_before_end(db, end) is not None:
            continue
        return end
    return None


def resolve_workstation_login_closed(db: Session, login_event: Event) -> bool:
    if event_closed_by_rdg(login_event):
        return True
    return find_rdg_end_after_workstation_login(db, login_event) is not None


def close_workstation_session_for_rdg_end(db: Session, rdg_end_event: Event) -> Event | None:
    """On RDG disconnect, mark matching workstation login as session-closed."""
    if rdg_end_event.type not in RDG_END_TYPES:
        return None
    if find_rdg_success_before_end(db, rdg_end_event) is not None:
        return None

    login = find_workstation_login_for_rdg_end(db, rdg_end_event)
    if login is None:
        return None
    mark_login_closed_by_rdg(login, rdg_end_event=rdg_end_event)
    return login