Fix GH-21731: Random\Engine\Xoshiro256StarStar::__unserialize() accepts all-zero state#21732
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iliaal wants to merge 1 commit intophp:PHP-8.4from
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Fix GH-21731: Random\Engine\Xoshiro256StarStar::__unserialize() accepts all-zero state#21732iliaal wants to merge 1 commit intophp:PHP-8.4from
iliaal wants to merge 1 commit intophp:PHP-8.4from
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…cepts all-zero state The constructor rejects a seed that would leave the internal state all zero, because xoshiro256** with zero state produces 0 on every call forever. The unserialize callback didn't check the same invariant. A caller feeding a crafted serialized payload through __unserialize() ended up with a live engine that returned 0 from every operation. Match the constructor: reject the all-zero state from the unserialize callback too. The Mt19937-aliased __unserialize() wrapper turns the false return into the standard "Invalid serialization data" exception. Closes phpGH-21731
TimWolla
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Apr 12, 2026
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Please run this actually through unserialize(), as in ext/random/tests/02_engine/all_serialize_error.phpt.
| --TEST-- | ||
| GH-21731: Xoshiro256StarStar::__unserialize() must reject the all-zero state | ||
| --FILE-- | ||
| <?php declare(strict_types = 1); |
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Tests should not contain unrelated logic.
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| /* An all-zero state generates zero forever. The constructor rejects | ||
| * such a seed; reject it here for symmetry. */ |
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| /* An all-zero state generates zero forever. The constructor rejects | |
| * such a seed; reject it here for symmetry. */ |
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Fixes #21731.
Random\Engine\Xoshiro256StarStar::__construct()rejects a seed that would leave the internal state all zero, because xoshiro256** with zero state returns0on every call forever. Theunserializecallback didn't check the same invariant. A caller feeding a crafted serialized payload through__unserialize()ended up with a live engine that returned 0 from every operation.Match the constructor: reject the all-zero state from
unserializetoo. The Mt19937-aliased__unserialize()wrapper maps thefalsereturn into the standard "Invalid serialization data for ... object" exception, so the wrapper needs no changes.