Recommend signatures only contain one sig per keyid

In an attempt to help implementers protect against incorrect threshold computation, update "File formats" to suggest that the signatures list contain only a single signature per keyid at metadata creation time. Suggested-by: Jussi Kukkonen <[email protected]> Signed-off-by: Joshua Lock <[email protected]>
theupdateframework · Jun 2, 2023 · 2ec6edd · 2ec6edd
1 parent 19174f4
commit 2ec6edd
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diff --git a/tuf-spec.md b/tuf-spec.md
@@ -547,6 +547,11 @@ All signed metadata objects have the format:
       ::
         A hex-encoded signature of the canonical form of the metadata for <a for="role">ROLE</a>.
 
+Note: The "signatures" list SHOULD only contain one <a>SIGNATURE</a> per
+<a for="role">KEYID</a>. This helps prevent multiple signatures by the same key
+being counted erroneously towards the minimum <a>THRESHOLD</a> indicating valid
+metadata.
+
 ### Key objects ### {#file-formats-keys}
 
 All <dfn>KEY</dfn> objects have the format: