MONGOCRYPT-922 Make padding strings unique#1182
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Gets test passing to ensure padding tokens are obtained from unique strings
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erwee
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May 26, 2026
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Discussed this with the crypto team. We'll be disputing the finding that an adversary can tell the real affix length after the document has been inserted (They shouldn't because each of the "fake" padding tokens have already been mapped to unique safeContent tags). So I don't think this change will be needed (perhaps not yet).
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Summary
Make padding strings unique.
Background & Motivation
See report in MONGOCRYPT-913 for details. This addresses finding with ID 1.
Quoting https://docs.google.com/document/d/1KhCFiofunsk7VeVB4VftvxFd9rQQOZrBQaTqHCljHtU/edit?tab=t.0:
This PR proposes appending a four byte counter after the
0xFFto ensure all padding strings are unique.Testing
Appending an additional four bytes resulted in needing to extend the test data in
RNG_DATA.hin substring tests to avoid the error "Out of random data".To additionally verify changes, the QE Text driver spec and prose tests were run locally with the C driver. The only necessary changes in tests were to update the exoected
__safeContent__(which I expect is a direct result of updating the padding string contents).