143 lines
5.0 KiB
Python
143 lines
5.0 KiB
Python
"""
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Redis-backed credential persistence for Mail Intake.
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---
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## Summary
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This module provides a Redis-based implementation of the
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``CredentialStore`` abstraction, enabling credential persistence
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across distributed and horizontally scaled deployments.
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The Redis credential store is designed for environments where
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authentication credentials must be shared safely across multiple
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processes, containers, or nodes, such as container orchestration
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platforms and microservice architectures.
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Key characteristics:
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- Distributed-safe, shared storage using Redis
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- Explicit, caller-defined serialization and deserialization
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- No reliance on unsafe mechanisms such as pickle
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- Optional time-to-live (TTL) support for automatic credential expiry
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This module is responsible solely for persistence concerns.
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Credential validation, refresh, rotation, and acquisition remain the
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responsibility of authentication provider implementations.
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"""
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from typing import Optional, TypeVar, Callable
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from mail_intake.credentials.store import CredentialStore
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T = TypeVar("T")
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class RedisCredentialStore(CredentialStore[T]):
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"""
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Redis-backed implementation of ``CredentialStore``.
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This store persists credentials in Redis and is suitable for
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distributed and horizontally scaled deployments where credentials
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must be shared across multiple processes or nodes.
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Notes:
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**Responsibilities:**
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- This class is responsible only for persistence and retrieval
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- It does not interpret, validate, refresh, or otherwise manage the lifecycle of the credentials being stored
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**Guarantees:**
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- The store is intentionally generic and delegates all serialization concerns to caller-provided functions
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- This avoids unsafe mechanisms such as pickle and allows credential formats to be explicitly controlled and audited
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"""
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def __init__(
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self,
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redis_client,
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key: str,
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serialize: Callable[[T], bytes],
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deserialize: Callable[[bytes], T],
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ttl_seconds: Optional[int] = None,
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):
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"""
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Initialize a Redis-backed credential store.
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Args:
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redis_client (Any):
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An initialized Redis client instance (for example, ``redis.Redis`` or a compatible interface) used to communicate with the Redis server.
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key (str):
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The Redis key under which credentials are stored. Callers are responsible for applying appropriate namespacing to avoid collisions.
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serialize (Callable[[T], bytes]):
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A callable that converts a credential object of type ``T`` into a ``bytes`` representation suitable for storage in Redis.
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deserialize (Callable[[bytes], T]):
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A callable that converts a ``bytes`` payload retrieved from Redis back into a credential object of type ``T``.
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ttl_seconds (Optional[int]):
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Optional time-to-live (TTL) for the stored credentials, expressed in seconds. When provided, Redis will automatically expire the stored credentials after the specified duration. If ``None``, credentials are stored without an expiration.
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"""
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self.redis = redis_client
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self.key = key
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self.serialize = serialize
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self.deserialize = deserialize
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self.ttl_seconds = ttl_seconds
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def load(self) -> Optional[T]:
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"""
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Load credentials from Redis.
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Returns:
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Optional[T]:
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An instance of type ``T`` if credentials are present and
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successfully deserialized; otherwise ``None``.
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Notes:
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**Guarantees:**
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- If no value exists for the configured key, or if the stored payload cannot be successfully deserialized, this method returns ``None``
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- The store does not attempt to validate the returned credentials or determine whether they are expired or otherwise usable
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"""
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raw = self.redis.get(self.key)
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if not raw:
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return None
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try:
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return self.deserialize(raw)
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except Exception:
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return None
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def save(self, credentials: T) -> None:
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"""
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Persist credentials to Redis.
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Args:
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credentials (T):
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The credential object to persist.
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Notes:
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**Responsibilities:**
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- Any previously stored credentials under the same key are overwritten
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- If a TTL is configured, the credentials will expire automatically after the specified duration
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"""
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payload = self.serialize(credentials)
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if self.ttl_seconds:
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self.redis.setex(self.key, self.ttl_seconds, payload)
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else:
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self.redis.set(self.key, payload)
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def clear(self) -> None:
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"""
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Remove stored credentials from Redis.
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Notes:
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**Lifecycle:**
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- This operation deletes the configured Redis key if it exists
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- Implementations should treat this method as idempotent
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"""
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self.redis.delete(self.key)
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