Close the second round of review findings: no credentials in the audit log

sigil/viewcodes.py

@@ -42,6 +42,18 @@ def _hash_code(code: str) -> str:
     return hashlib.sha256(normalise(code).encode("utf-8")).hexdigest()
 
 
+def _code_ref(code: str) -> str:
+    """How a code is referred to in the audit log.
+
+    Never the code, and never a prefix of it. Codes carry 40 bits; the first
+    four characters are 20 of those bits, so logging a prefix drops the search
+    space to about a million candidates, which is nothing to a reader holding
+    the log. A truncated digest identifies the code for correlation without
+    carrying any of the secret.
+    """
+    return "code:" + _hash_code(code)[:12]
+
+
 def normalise(code: str) -> str:
     """Canonical form: upper case, letters and digits only.
 
@@ -110,7 +122,7 @@ def issue_code(
         subject=f"{agent}'s human",
         fingerprint=agent_row["fingerprint"],
         detail={
-            "code_prefix": code[:5],
+            "code_ref": _code_ref(code),
             "scopes": granted,
             "redeem_expires_at": now + code_ttl,
         },
@@ -172,13 +184,13 @@ def redeem_code(store: Store, code: str) -> dict:
 
     # The session window starts here, at redemption, not at issue. Waiting for a
     # code must not eat into the hour the human was given.
-    return sessions.issue_view_session(
-        store,
+    grant = sessions.GrantedCode(
         agent,
-        scopes=_json.loads(row["scopes"]),
-        ttl=row["view_ttl"],
-        granted_by=agent,
+        _json.loads(row["scopes"]),
+        row["view_ttl"],
+        sessions._ISSUER,
     )
+    return sessions.issue_view_session(store, grant)
 
 
 def sweep(store: Store) -> int: