half broken

internal/api/auth.go

@@ -17,13 +17,14 @@ import (
 //
 // Two details matter for security here:
 //
-//   - Every comparison is constant-time, including the API key scan. A
-//     byte-at-a-time comparison leaks a valid key prefix to anyone who can
-//     measure response latency, which is a real attack on a network-exposed
-//     admin API.
-//   - Keys are compared by hash, not by string, so the stored form is not a
-//     raw key and a timing difference between a long and short key cannot
-//     reveal length.
+//   - Credentials are never compared in plaintext. An API key is hashed with
+//     SHA-256 and looked up in a map keyed on that hash, so the long-lived
+//     structure holds no key that could be read back out of a core dump, and a
+//     lookup is a hash-map hit whose cost does not depend on how much of the
+//     key the caller guessed. There is no byte-at-a-time scan: the comment that
+//     used to describe one described a function with no callers.
+//   - The two fields that are compared directly — the basic username and the
+//     hashed password — go through subtle.ConstantTimeCompare.
 type authenticator struct {
 	mode string
 	// readOnly maps key hash -> key label.