Add encryption support using cryptography to Sessions implementation

examples/memory/encrypted_session_example.py

@@ -0,0 +1,109 @@
+"""
+Example demonstrating encrypted session memory functionality.
+
+This example shows how to use encrypted session memory to maintain conversation history
+across multiple agent runs with automatic encryption and TTL-based expiration.
+The EncryptedSession wrapper provides transparent encryption over any underlying session.
+"""
+
+import asyncio
+from typing import cast
+
+from agents import Agent, Runner, SQLiteSession
+from agents.extensions.memory import EncryptedSession
+from agents.extensions.memory.encrypt_session import EncryptedEnvelope
+
+
+async def main():
+    # Create an agent
+    agent = Agent(
+        name="Assistant",
+        instructions="Reply very concisely.",
+    )
+
+    # Create an underlying session (SQLiteSession in this example)
+    session_id = "conversation_123"
+    underlying_session = SQLiteSession(session_id)
+
+    # Wrap with encrypted session for automatic encryption and TTL
+    session = EncryptedSession(
+        session_id=session_id,
+        underlying_session=underlying_session,
+        encryption_key="my-secret-encryption-key",
+        ttl=3600,  # 1 hour TTL for messages
+    )
+
+    print("=== Encrypted Session Example ===")
+    print("The agent will remember previous messages automatically with encryption.\n")
+
+    # First turn
+    print("First turn:")
+    print("User: What city is the Golden Gate Bridge in?")
+    result = await Runner.run(
+        agent,
+        "What city is the Golden Gate Bridge in?",
+        session=session,
+    )
+    print(f"Assistant: {result.final_output}")
+    print()
+
+    # Second turn - the agent will remember the previous conversation
+    print("Second turn:")
+    print("User: What state is it in?")
+    result = await Runner.run(agent, "What state is it in?", session=session)
+    print(f"Assistant: {result.final_output}")
+    print()
+
+    # Third turn - continuing the conversation
+    print("Third turn:")
+    print("User: What's the population of that state?")
+    result = await Runner.run(
+        agent,
+        "What's the population of that state?",
+        session=session,
+    )
+    print(f"Assistant: {result.final_output}")
+    print()
+
+    print("=== Conversation Complete ===")
+    print("Notice how the agent remembered the context from previous turns!")
+    print("All conversation history was automatically encrypted and stored securely.")
+
+    # Demonstrate the limit parameter - get only the latest 2 items
+    print("\n=== Latest Items Demo ===")
+    latest_items = await session.get_items(limit=2)
+    print("Latest 2 items (automatically decrypted):")
+    for i, msg in enumerate(latest_items, 1):
+        role = msg.get("role", "unknown")
+        content = msg.get("content", "")
+        print(f"  {i}. {role}: {content}")
+
+    print(f"\nFetched {len(latest_items)} out of total conversation history.")
+
+    # Get all items to show the difference
+    all_items = await session.get_items()
+    print(f"Total items in session: {len(all_items)}")
+
+    # Show that underlying storage is encrypted
+    print("\n=== Encryption Demo ===")
+    print("Checking underlying storage to verify encryption...")
+    raw_items = await underlying_session.get_items()
+    print("Raw encrypted items in underlying storage:")
+    for i, item in enumerate(raw_items, 1):
+        if isinstance(item, dict) and item.get("__enc__") == 1:
+            enc_item = cast(EncryptedEnvelope, item)
+            print(
+                f"  {i}. Encrypted envelope: __enc__={enc_item['__enc__']}, "
+                f"payload length={len(enc_item['payload'])}"
+            )
+        else:
+            print(f"  {i}. Unencrypted item: {item}")
+
+    print(f"\nAll {len(raw_items)} items are stored encrypted with TTL-based expiration.")
+
+    # Clean up
+    underlying_session.close()
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

pyproject.toml

@@ -39,6 +39,7 @@ viz = ["graphviz>=0.17"]
 litellm = ["litellm>=1.67.4.post1, <2"]
 realtime = ["websockets>=15.0, <16"]
 sqlalchemy = ["SQLAlchemy>=2.0", "asyncpg>=0.29.0"]
+encrypt = ["cryptography>=45.0, <46"]
 
 [dependency-groups]
 dev = [
@@ -65,6 +66,7 @@ dev = [
     "eval-type-backport>=0.2.2",
     "fastapi >= 0.110.0, <1",
     "aiosqlite>=0.21.0",
+    "cryptography>=45.0, <46",
 ]
 
 [tool.uv.workspace]

src/agents/extensions/memory/__init__.py

@@ -1,15 +1,42 @@
-"""Session memory backends living in the extensions namespace.
-
-This package contains optional, production-grade session implementations that
-introduce extra third-party dependencies (database drivers, ORMs, etc.). They
-conform to the :class:`agents.memory.session.Session` protocol so they can be
-used as a drop-in replacement for :class:`agents.memory.session.SQLiteSession`.
-"""
-
-from __future__ import annotations
-
-from .sqlalchemy_session import SQLAlchemySession  # noqa: F401
-
-__all__: list[str] = [
-    "SQLAlchemySession",
-]
+"""Session memory backends living in the extensions namespace.
+
+This package contains optional, production-grade session implementations that
+introduce extra third-party dependencies (database drivers, ORMs, etc.). They
+conform to the :class:`agents.memory.session.Session` protocol so they can be
+used as a drop-in replacement for :class:`agents.memory.session.SQLiteSession`.
+"""
+
+from __future__ import annotations
+
+from typing import Any
+
+__all__: list[str] = [
+    "EncryptedSession",
+    "SQLAlchemySession",
+]
+
+
+def __getattr__(name: str) -> Any:
+    if name == "EncryptedSession":
+        try:
+            from .encrypt_session import EncryptedSession  # noqa: F401
+
+            return EncryptedSession
+        except ModuleNotFoundError as e:
+            raise ImportError(
+                "EncryptedSession requires the 'cryptography' extra. "
+                "Install it with: pip install openai-agents[encrypt]"
+            ) from e
+
+    if name == "SQLAlchemySession":
+        try:
+            from .sqlalchemy_session import SQLAlchemySession  # noqa: F401
+
+            return SQLAlchemySession
+        except ModuleNotFoundError as e:
+            raise ImportError(
+                "SQLAlchemySession requires the 'sqlalchemy' extra. "
+                "Install it with: pip install openai-agents[sqlalchemy]"
+            ) from e
+
+    raise AttributeError(f"module {__name__} has no attribute {name}")

src/agents/extensions/memory/encrypt_session.py

@@ -0,0 +1,185 @@
+"""Encrypted Session wrapper for secure conversation storage.
+
+This module provides transparent encryption for session storage with automatic
+expiration of old data. When TTL expires, expired items are silently skipped.
+
+Usage::
+
+    from agents.extensions.memory import EncryptedSession, SQLAlchemySession
+
+    # Create underlying session (e.g. SQLAlchemySession)
+    underlying_session = SQLAlchemySession.from_url(
+        session_id="user-123",
+        url="postgresql+asyncpg://app:[email protected]/agents",
+        create_tables=True,
+    )
+
+    # Wrap with encryption and TTL-based expiration
+    session = EncryptedSession(
+        session_id="user-123",
+        underlying_session=underlying_session,
+        encryption_key="your-encryption-key",
+        ttl=600,  # 10 minutes
+    )
+
+    await Runner.run(agent, "Hello", session=session)
+"""
+
+from __future__ import annotations
+
+import base64
+import json
+from typing import Any, cast
+
+from cryptography.fernet import Fernet, InvalidToken
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.kdf.hkdf import HKDF
+from typing_extensions import Literal, TypedDict, TypeGuard
+
+from ...items import TResponseInputItem
+from ...memory.session import SessionABC
+
+
+class EncryptedEnvelope(TypedDict):
+    """TypedDict for encrypted message envelopes stored in the underlying session."""
+
+    __enc__: Literal[1]
+    v: int
+    kid: str
+    payload: str
+
+
+def _ensure_fernet_key_bytes(master_key: str) -> bytes:
+    """
+    Accept either a Fernet key (urlsafe-b64, 32 bytes after decode) or a raw string.
+    Returns raw bytes suitable for HKDF input.
+    """
+    if not master_key:
+        raise ValueError("encryption_key not set; required for EncryptedSession.")
+    try:
+        key_bytes = base64.urlsafe_b64decode(master_key)
+        if len(key_bytes) == 32:
+            return key_bytes
+    except Exception:
+        pass
+    return master_key.encode("utf-8")
+
+
+def _derive_session_fernet_key(master_key_bytes: bytes, session_id: str) -> Fernet:
+    hkdf = HKDF(
+        algorithm=hashes.SHA256(),
+        length=32,
+        salt=session_id.encode("utf-8"),
+        info=b"agents.session-store.hkdf.v1",
+    )
+    derived = hkdf.derive(master_key_bytes)
+    return Fernet(base64.urlsafe_b64encode(derived))
+
+
+def _to_json_bytes(obj: Any) -> bytes:
+    return json.dumps(obj, ensure_ascii=False, separators=(",", ":"), default=str).encode("utf-8")
+
+
+def _from_json_bytes(data: bytes) -> Any:
+    return json.loads(data.decode("utf-8"))
+
+
+def _is_encrypted_envelope(item: object) -> TypeGuard[EncryptedEnvelope]:
+    """Type guard to check if an item is an encrypted envelope."""
+    return (
+        isinstance(item, dict)
+        and item.get("__enc__") == 1
+        and "payload" in item
+        and "kid" in item
+        and "v" in item
+    )
+
+
+class EncryptedSession(SessionABC):
+    """Encrypted wrapper for Session implementations with TTL-based expiration.
+
+    This class wraps any SessionABC implementation to provide transparent
+    encryption/decryption of stored items using Fernet encryption with
+    per-session key derivation and automatic expiration of old data.
+
+    When items expire (exceed TTL), they are silently skipped during retrieval.
+
+    Note: Expired tokens are rejected based on the system clock of the application server.
+    To avoid valid tokens being rejected due to clock drift, ensure all servers in
+    your environment are synchronized using NTP.
+    """
+
+    def __init__(
+        self,
+        session_id: str,
+        underlying_session: SessionABC,
+        encryption_key: str,
+        ttl: int = 600,
+    ):
+        """
+        Args:
+            session_id: ID for this session
+            underlying_session: The real session store (e.g. SQLiteSession, SQLAlchemySession)
+            encryption_key: Master key (Fernet key or raw secret)
+            ttl: Token time-to-live in seconds (default 10 min)
+        """
+        self.session_id = session_id
+        self.underlying_session = underlying_session
+        self.ttl = ttl
+
+        master = _ensure_fernet_key_bytes(encryption_key)
+        self.cipher = _derive_session_fernet_key(master, session_id)
+        self._kid = "hkdf-v1"
+        self._ver = 1
+
+    def __getattr__(self, name):
+        return getattr(self.underlying_session, name)
+
+    def _wrap(self, item: TResponseInputItem) -> EncryptedEnvelope:
+        if isinstance(item, dict):
+            payload = item
+        elif hasattr(item, "model_dump"):
+            payload = item.model_dump()
+        elif hasattr(item, "__dict__"):
+            payload = item.__dict__
+        else:
+            payload = dict(item)
+
+        token = self.cipher.encrypt(_to_json_bytes(payload)).decode("utf-8")
+        return {"__enc__": 1, "v": self._ver, "kid": self._kid, "payload": token}
+
+    def _unwrap(self, item: TResponseInputItem | EncryptedEnvelope) -> TResponseInputItem | None:
+        if not _is_encrypted_envelope(item):
+            return cast(TResponseInputItem, item)
+
+        try:
+            token = item["payload"].encode("utf-8")
+            plaintext = self.cipher.decrypt(token, ttl=self.ttl)
+            return cast(TResponseInputItem, _from_json_bytes(plaintext))
+        except (InvalidToken, KeyError):
+            return None
+
+    async def get_items(self, limit: int | None = None) -> list[TResponseInputItem]:
+        encrypted_items = await self.underlying_session.get_items(limit)
+        valid_items: list[TResponseInputItem] = []
+        for enc in encrypted_items:
+            item = self._unwrap(enc)
+            if item is not None:
+                valid_items.append(item)
+        return valid_items
+
+    async def add_items(self, items: list[TResponseInputItem]) -> None:
+        wrapped: list[EncryptedEnvelope] = [self._wrap(it) for it in items]
+        await self.underlying_session.add_items(cast(list[TResponseInputItem], wrapped))
+
+    async def pop_item(self) -> TResponseInputItem | None:
+        while True:
+            enc = await self.underlying_session.pop_item()
+            if not enc:
+                return None
+            item = self._unwrap(enc)
+            if item is not None:
+                return item
+
+    async def clear_session(self) -> None:
+        await self.underlying_session.clear_session()