427 lines
16 KiB
Python
427 lines
16 KiB
Python
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"""Durable PostgreSQL audit backend (AUDIT-WP-0005-T01).
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Production custody. Runs on the Railiance shared PostgreSQL platform
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(`rapp-postgres`), inside the database-per-consumer boundary fixed by that
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repo's ADR-0001.
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Two properties are pushed into the database rather than the application:
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* **Idempotency** — ``INSERT ... ON CONFLICT DO NOTHING RETURNING`` resolves
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insert-or-detect in one statement, so two concurrent submissions of the same
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event cannot both be told they were first. The SQLite backend learned this
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the hard way; see its test.
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* **Append-only custody** — a trigger rejects ``UPDATE`` and ``DELETE`` on the
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events table, so a leaked runtime credential can add records but cannot
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rewrite or erase existing ones. This is what lets ``RetentionPolicy`` declare
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``immutable=True`` honestly; see :meth:`retention_policy` for its limits.
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"""
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from __future__ import annotations
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import json
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import os
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from datetime import datetime, timezone
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from typing import Any
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from audit_core.interface import (
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AcceptResult,
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AuditEvent,
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BackendUnavailableError,
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EventConflictError,
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EventValidationError,
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RetentionPolicy,
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validate_event,
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)
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from audit_core.redaction import Finding
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try: # pragma: no cover - import guard
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import psycopg
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from psycopg_pool import ConnectionPool
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except ImportError as exc: # pragma: no cover
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raise ImportError(
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"the postgres backend needs psycopg: pip install 'audit-core[postgres]'"
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) from exc
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DEFAULT_SCHEMA = "audit_core"
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# Ordered, append-only. Each entry runs once and is recorded in
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# schema_migrations. Never edit a released migration — add a new one.
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MIGRATIONS: list[tuple[str, str]] = [
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(
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"0001-events",
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"""
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CREATE TABLE IF NOT EXISTS {schema}.events (
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event_id text PRIMARY KEY,
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payload_hash text NOT NULL,
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accepted_at timestamptz NOT NULL DEFAULT now(),
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observed_at timestamptz,
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tenant text NOT NULL,
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correlation_id text,
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source text NOT NULL,
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action text NOT NULL,
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record jsonb NOT NULL
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);
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CREATE INDEX IF NOT EXISTS events_correlation_idx
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ON {schema}.events (correlation_id);
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-- Tenant keying is mandatory per business-app-service-contract 1.3;
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-- the index makes per-tenant export and retention tractable.
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CREATE INDEX IF NOT EXISTS events_tenant_idx ON {schema}.events (tenant);
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""",
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),
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(
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"0002-append-only",
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"""
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CREATE OR REPLACE FUNCTION {schema}.reject_mutation() RETURNS trigger AS $fn$
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BEGIN
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RAISE EXCEPTION 'audit events are append-only (attempted %)', TG_OP
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USING ERRCODE = 'restrict_violation';
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END;
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$fn$ LANGUAGE plpgsql;
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DROP TRIGGER IF EXISTS events_append_only ON {schema}.events;
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CREATE TRIGGER events_append_only
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BEFORE UPDATE OR DELETE ON {schema}.events
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FOR EACH ROW EXECUTE FUNCTION {schema}.reject_mutation();
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""",
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),
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(
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"0003-dead-letters",
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"""
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CREATE TABLE IF NOT EXISTS {schema}.dead_letters (
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id bigserial PRIMARY KEY,
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event_id text,
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received_at timestamptz NOT NULL DEFAULT now(),
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sender text,
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reason text NOT NULL,
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payload_hash text NOT NULL,
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payload text,
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payload_withheld boolean NOT NULL DEFAULT false
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);
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CREATE INDEX IF NOT EXISTS dead_letters_event_idx
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ON {schema}.dead_letters (event_id);
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""",
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),
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(
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"0004-secret-findings",
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"""
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CREATE TABLE IF NOT EXISTS {schema}.secret_findings (
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sender text NOT NULL,
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source text NOT NULL,
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action text NOT NULL,
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field_path text NOT NULL,
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outcome text NOT NULL,
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persisted boolean NOT NULL DEFAULT false,
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occurrences bigint NOT NULL DEFAULT 0,
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first_seen timestamptz NOT NULL DEFAULT now(),
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last_seen timestamptz NOT NULL DEFAULT now(),
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PRIMARY KEY (sender, source, action, field_path, outcome)
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);
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""",
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),
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]
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# Rejection reasons whose payload must never be persisted — storing the body of
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# an event rejected *for carrying secret-shaped material* would write that
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# material into the audit store.
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WITHHOLD_PAYLOAD_REASONS = frozenset({"secret_shaped_field"})
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class PostgresAuditBackend:
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"""Audit custody in PostgreSQL."""
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def __init__(
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self,
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dsn: str | None = None,
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*,
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schema: str = DEFAULT_SCHEMA,
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retention_days: int | None = None,
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min_size: int = 1,
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max_size: int = 8,
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statement_timeout_ms: int = 30_000,
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migrate: bool = True,
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) -> None:
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self.dsn = dsn or os.environ.get("AUDIT_CORE_DATABASE_URL") or ""
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if not self.dsn:
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raise ValueError("a DSN is required (AUDIT_CORE_DATABASE_URL)")
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if not schema.isidentifier():
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raise ValueError(f"unsafe schema name: {schema!r}")
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self.schema = schema
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self.retention_days = retention_days
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try:
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self.pool = ConnectionPool(
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self.dsn,
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min_size=min_size,
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max_size=max_size,
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kwargs={
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"autocommit": True,
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# A stalled write must surface as unavailable rather than
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# hold a request open indefinitely.
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"options": f"-c statement_timeout={int(statement_timeout_ms)}",
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},
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open=True,
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timeout=10,
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)
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except Exception as exc: # psycopg raises a wide family here
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raise BackendUnavailableError(f"cannot connect: {exc}") from exc
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if migrate:
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self.migrate()
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# --- schema ------------------------------------------------------------
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def migrate(self) -> list[str]:
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"""Apply pending migrations. Returns the ids applied this call."""
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applied: list[str] = []
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try:
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with self.pool.connection() as conn:
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conn.execute(f'CREATE SCHEMA IF NOT EXISTS "{self.schema}"')
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conn.execute(
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f'CREATE TABLE IF NOT EXISTS "{self.schema}".schema_migrations ('
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" id text PRIMARY KEY, applied_at timestamptz NOT NULL DEFAULT now())"
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)
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done = {
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row[0]
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for row in conn.execute(
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f'SELECT id FROM "{self.schema}".schema_migrations'
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).fetchall()
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}
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for migration_id, body in MIGRATIONS:
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if migration_id in done:
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continue
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conn.execute(body.format(schema=f'"{self.schema}"'))
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conn.execute(
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f'INSERT INTO "{self.schema}".schema_migrations (id) VALUES (%s)',
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(migration_id,),
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)
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applied.append(migration_id)
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except psycopg.Error as exc:
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raise BackendUnavailableError(f"migration failed: {exc}") from exc
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return applied
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@property
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def _events(self) -> str:
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return f'"{self.schema}".events'
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# --- contract ----------------------------------------------------------
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@property
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def retention_policy(self) -> RetentionPolicy:
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"""Declared custody guarantees.
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``immutable`` is True because migration 0002 installs a trigger that
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rejects UPDATE and DELETE, so no consumer credential can alter a stored
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record. It is not a claim against the database owner or a superuser,
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who can drop the trigger; ``tamper_evidence`` is correspondingly False,
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because nothing here would *prove* they had. Hash-chaining or external
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anchoring would be needed for that, and is not implemented.
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"""
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return RetentionPolicy(
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custody_class="archive",
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retention_days=self.retention_days,
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immutable=True,
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tamper_evidence=False,
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durable=True,
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)
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def emit(self, event: AuditEvent) -> str:
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return self.accept(event, payload_hash=_record_hash(event)).reference
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def accept(self, event: AuditEvent, payload_hash: str) -> AcceptResult:
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validate_event(event)
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reference = f"audit:{event.event_id}"
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details = event.details if isinstance(event.details, dict) else {}
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record = event.as_record()
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try:
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with self.pool.connection() as conn:
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inserted = conn.execute(
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f"""
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INSERT INTO {self._events}
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(event_id, payload_hash, observed_at, tenant, correlation_id,
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source, action, record)
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VALUES (%s, %s, %s, %s, %s, %s, %s, %s)
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ON CONFLICT (event_id) DO NOTHING
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RETURNING event_id
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""",
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(
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event.event_id,
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payload_hash,
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_timestamp(event.observed_at),
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event.tenant,
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str(details.get("correlation_id") or "") or None,
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event.source,
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event.action,
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json.dumps(record, sort_keys=True),
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),
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).fetchone()
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if inserted is not None:
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return AcceptResult(duplicate=False, reference=reference)
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existing = conn.execute(
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f"SELECT payload_hash FROM {self._events} WHERE event_id = %s",
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(event.event_id,),
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).fetchone()
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except psycopg.Error as exc:
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raise BackendUnavailableError(str(exc)) from exc
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if existing is None:
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raise BackendUnavailableError("event disappeared during accept")
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if existing[0] != payload_hash:
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raise EventConflictError(
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f"event_id {event.event_id} already held with a different payload"
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)
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return AcceptResult(duplicate=True, reference=reference)
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# --- operator surface --------------------------------------------------
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def get(self, event_id: str) -> dict | None:
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rows = self._query(
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f"SELECT record, accepted_at FROM {self._events} WHERE event_id = %s",
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(event_id,),
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)
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if not rows:
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return None
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return {"accepted_at": _iso(rows[0][1]), **rows[0][0]}
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def by_correlation(self, correlation_id: str, limit: int = 100) -> list[dict]:
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rows = self._query(
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f"SELECT record, accepted_at FROM {self._events} "
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"WHERE correlation_id = %s ORDER BY accepted_at, event_id LIMIT %s",
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(correlation_id, int(limit)),
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)
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return [{"accepted_at": _iso(at), **rec} for rec, at in rows]
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def replay(self, event_id: str) -> AcceptResult:
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"""Re-submit a stored event through :meth:`accept`.
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Reconciliation, not re-creation: replaying an event already in custody
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must return ``duplicate=True`` against the same record. If it were to
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report a first acceptance, the store would be producing a second
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custody record for one source event — the exact failure the whole
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idempotency design exists to prevent.
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"""
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rows = self._query(
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f"SELECT record, payload_hash FROM {self._events} WHERE event_id = %s",
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(event_id,),
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)
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if not rows:
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raise KeyError(event_id)
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record, payload_hash = rows[0]
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return self.accept(_event_from_record(record), payload_hash)
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def record_rejection(
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self,
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*,
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event_id: str | None,
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reason: str,
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payload_hash: str,
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sender: str | None = None,
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payload: str | None = None,
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) -> None:
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withheld = reason in WITHHOLD_PAYLOAD_REASONS
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self._execute(
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f'INSERT INTO "{self.schema}".dead_letters '
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"(event_id, sender, reason, payload_hash, payload, payload_withheld) "
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"VALUES (%s, %s, %s, %s, %s, %s)",
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(event_id, sender, reason, payload_hash,
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None if withheld else payload, withheld),
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)
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def dead_letters(self, limit: int = 100) -> list[dict]:
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rows = self._query(
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"SELECT event_id, received_at, sender, reason, payload_hash, payload, "
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f'payload_withheld FROM "{self.schema}".dead_letters '
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"ORDER BY id DESC LIMIT %s",
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(int(limit),),
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)
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return [
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{
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"event_id": r[0], "received_at": _iso(r[1]), "sender": r[2],
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"reason": r[3], "payload_hash": r[4], "payload": r[5],
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"payload_withheld": bool(r[6]),
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}
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for r in rows
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]
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def count_secret_findings(
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self, *, sender: str, source: str, action: str, outcome: str, findings
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) -> None:
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for finding in findings:
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self._execute(
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f'INSERT INTO "{self.schema}".secret_findings '
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"(sender, source, action, field_path, outcome, persisted, occurrences) "
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"VALUES (%s, %s, %s, %s, %s, %s, 1) "
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"ON CONFLICT (sender, source, action, field_path, outcome) DO UPDATE "
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"SET occurrences = secret_findings.occurrences + 1, last_seen = now()",
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(sender, source, action, finding.path, outcome,
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bool(getattr(finding, "in_persisted_data", False))),
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)
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def secret_findings(self, limit: int = 100) -> list[dict]:
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rows = self._query(
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"SELECT sender, source, action, field_path, outcome, persisted, "
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f'occurrences, first_seen, last_seen FROM "{self.schema}".secret_findings '
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"ORDER BY occurrences DESC, last_seen DESC LIMIT %s",
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(int(limit),),
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)
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return [
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{
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"sender": r[0], "source": r[1], "action": r[2], "field_path": r[3],
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|
|
"outcome": r[4], "persisted": bool(r[5]), "occurrences": r[6],
|
||
|
|
"first_seen": _iso(r[7]), "last_seen": _iso(r[8]),
|
||
|
|
}
|
||
|
|
for r in rows
|
||
|
|
]
|
||
|
|
|
||
|
|
# --- lifecycle ---------------------------------------------------------
|
||
|
|
|
||
|
|
def health(self) -> None:
|
||
|
|
self._query("SELECT 1", ())
|
||
|
|
|
||
|
|
def close(self) -> None:
|
||
|
|
self.pool.close()
|
||
|
|
|
||
|
|
def _query(self, sql: str, params: tuple) -> list:
|
||
|
|
try:
|
||
|
|
with self.pool.connection() as conn:
|
||
|
|
return conn.execute(sql, params).fetchall()
|
||
|
|
except psycopg.Error as exc:
|
||
|
|
raise BackendUnavailableError(str(exc)) from exc
|
||
|
|
|
||
|
|
def _execute(self, sql: str, params: tuple) -> None:
|
||
|
|
try:
|
||
|
|
with self.pool.connection() as conn:
|
||
|
|
conn.execute(sql, params)
|
||
|
|
except psycopg.Error as exc:
|
||
|
|
raise BackendUnavailableError(str(exc)) from exc
|
||
|
|
|
||
|
|
|
||
|
|
def _timestamp(value: str | None) -> datetime | None:
|
||
|
|
if not value:
|
||
|
|
return None
|
||
|
|
try:
|
||
|
|
return datetime.fromisoformat(str(value).replace("Z", "+00:00"))
|
||
|
|
except ValueError:
|
||
|
|
return None
|
||
|
|
|
||
|
|
|
||
|
|
def _iso(value: Any) -> str | None:
|
||
|
|
if isinstance(value, datetime):
|
||
|
|
return value.astimezone(timezone.utc).replace(microsecond=0).isoformat()
|
||
|
|
return value
|
||
|
|
|
||
|
|
|
||
|
|
def _event_from_record(record: dict) -> AuditEvent:
|
||
|
|
return AuditEvent(
|
||
|
|
source=record["source"], action=record["action"], resource=record["resource"],
|
||
|
|
outcome=record["outcome"], tenant=record["tenant"], scope=record["scope"],
|
||
|
|
actor=record.get("actor"), reason=record.get("reason"),
|
||
|
|
details=record.get("details") or {}, event_id=record["event_id"],
|
||
|
|
observed_at=record["observed_at"], schema_version=record["schema_version"],
|
||
|
|
)
|
||
|
|
|
||
|
|
|
||
|
|
def _record_hash(event: AuditEvent) -> str:
|
||
|
|
import hashlib
|
||
|
|
|
||
|
|
return hashlib.sha256(
|
||
|
|
json.dumps(event.as_record(), sort_keys=True).encode("utf-8")
|
||
|
|
).hexdigest()
|