| commit | b4a333fea588b0df6f441f0e9838cff9338c71c4 | [log] [tgz] |
|---|---|---|
| author | Filippo Valsorda <filippo@golang.org> | Wed Mar 05 12:08:35 2025 +0100 |
| committer | Gopher Robot <gobot@golang.org> | Fri Mar 07 11:32:59 2025 -0800 |
| tree | 38d1b2195a2170901df41537f0ef54cad06bfc4c | |
| parent | e0b110b926c47227aa0669b630f5292152945bba [diff] |
crypto/internal/fips140/bigmod: explicitly clear expanded limbs on reset Russ Cox noticed that reset was clearing limbs up to the *previous* Nat size, not up to the new size, because clear(x.limbs) was happening before the x.limbs[:n] reslice. That's potentially a severe issue, because it may leave garbage in x.limbs[len(x.limbs):n] if n < cap(x.limbs). We were saved by an accidental invariant caused by the bug itself, though: x.limbs[len(x.limbs):cap(x.limbs)] are always zero. reset was always clearing all exposed (and hence potentially non-zero) limbs before shrinking the Nat, and the only other function that could shrink the Nat was trim, which only trims zero limbs. Near miss. Preserve the accidental invariant in the fix, because memclr is cheap and it just proved it can save us from potential mistakes. Change-Id: I6a6a4656a77735d8e8d520c699c4d85dd33ce497 Reviewed-on: https://go-review.googlesource.com/c/go/+/655056 Auto-Submit: Filippo Valsorda <filippo@golang.org> Reviewed-by: Junyang Shao <shaojunyang@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Roland Shoemaker <roland@golang.org>
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