Harden Sigil: sigil/sessions.py

sigil/sessions.py

@@ -17,6 +17,8 @@ Two properties worth stating out loud:
 
 from __future__ import annotations
 
+import hashlib
+import json
 import secrets
 import time
 from typing import List, Optional
@@ -40,6 +42,16 @@ AGENT_SCOPES = (AGENT_ACT, "view:read", "view:write", "secret:use")
 DEFAULT_AGENT_TTL = 900  # 15 minutes. Short enough to be boring.
 
 
+def hash_token(token: str) -> str:
+    """Digest a bearer token for storage.
+
+    Session tokens are stored hashed, like one-time codes. A stolen database
+    must not hand an attacker live sessions; the plaintext token exists only in
+    the caller's hands, which is where a bearer token belongs.
+    """
+    return hashlib.sha256(token.encode("utf-8")).hexdigest()
+
+
 def _token() -> str:
     return secrets.token_urlsafe(32)
 
@@ -59,7 +71,8 @@ def issue_agent_session(
     token = _token()
     expires = int(time.time()) + ttl
     store.put_session(
-        token, AGENT, agent, agent, granted, expires, granted_by=None
+        hash_token(token), AGENT, agent, agent, granted, expires,
+        granted_by=None, fingerprint=fingerprint,
     )
     store.record(
         "session.issued",
@@ -88,6 +101,11 @@ def issue_view_session(
 ) -> dict:
     """Mint a human_via_agent session.
 
+    Plumbing primitive, not an entry point: it trusts whoever calls it. Code
+    reached from outside the process must authenticate first. issue_code()
+    enforces that by requiring an agent session, and redeem_code() may present a
+    one-time code as its credential.
+
     `granted_by` is the agent that approved the code. It is recorded so the
     audit trail can answer "who let this human in" and not merely "which
     agent's things did they see".
@@ -101,7 +119,7 @@ def issue_view_session(
     token = _token()
     expires = int(time.time()) + ttl
     store.put_session(
-        token,
+        hash_token(token),
         HUMAN_VIA_AGENT,
         f"{agent}'s human",
         agent,
@@ -134,22 +152,22 @@ def issue_view_session(
 
 def resolve(store: Store, token: str) -> dict:
     """Look up a session and reject it if revoked or expired."""
-    row = store.get_session(token)
+    row = store.get_session(hash_token(token))
     if row is None:
         raise errors.SessionUnknown("no such session")
     if row["revoked_at"] is not None:
         raise errors.SessionExpired("session revoked")
     if time.time() >= row["expires_at"]:
         raise errors.SessionExpired("session expired")
-    import json as _json
-
     return {
         "token": token,
         "kind": row["kind"],
         "subject": row["subject"],
         "on_behalf_of": row["on_behalf_of"],
         "granted_by": row["granted_by"],
-        "scopes": _json.loads(row["scopes"]),
+        "fingerprint": row["fingerprint"],
+        "revoked_reason": row["revoked_reason"],
+        "scopes": json.loads(row["scopes"]),
         "expires_at": row["expires_at"],
     }
 
@@ -179,5 +197,5 @@ def assert_may_act_as_agent(session: dict) -> str:
 
 
 def revoke(store: Store, token: str) -> None:
-    store.revoke_session(token)
+    store.revoke_session(hash_token(token))
     store.record("session.revoked", actor="system", detail={"token_prefix": token[:8]})