python: fix unbounded recursion DoS in FieldMask path handling#26509
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CHIRANJEET1729DAS wants to merge 1 commit intoprotocolbuffers:mainfrom
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python: fix unbounded recursion DoS in FieldMask path handling#26509CHIRANJEET1729DAS wants to merge 1 commit intoprotocolbuffers:mainfrom
CHIRANJEET1729DAS wants to merge 1 commit intoprotocolbuffers:mainfrom
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A FieldMask path string with thousands of dot-separated segments bypasses wire-level parser depth limits (they treat it as a flat string) and causes unbounded Python call-stack recursion in _FieldMaskTree, crashing the process with RecursionError. Two complementary defences: 1. AddPath() now rejects paths exceeding _MAX_FIELD_MASK_DEPTH (64) segments with a ValueError before they enter the tree. 2. _AddFieldPaths(), AddLeafNodes(), and _MergeMessage() are rewritten iteratively using explicit stacks, eliminating all unbounded Python call-stack growth as defence-in-depth. Security impact: any server using Union(), Intersect(), or CanonicalFormFromMask() on attacker-controlled FieldMask input was vulnerable to remote DoS via a ~2KB payload. Fixes: https://github.com/protocolbuffers/protobuf/issues/<ISSUE_NUMBER>
CHIRANJEET1729DAS
requested review from
haberman
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a team
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Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA). View this failed invocation of the CLA check for more information. For the most up to date status, view the checks section at the bottom of the pull request. |
Contributor
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I replied on #26489 for the shape of fix that I think we could accept, but we can't take a look at your PR without the CLA first. Thanks! |
Contributor
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Thank you for raising this issue; resolved in 7adc4b6 so closing this PR Thanks! |
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A FieldMask path string with thousands of dot-separated segments bypasses wire-level parser depth limits (they treat it as a flat string) and causes unbounded Python call-stack recursion in _FieldMaskTree, crashing the process with RecursionError.
Two complementary defences:
AddPath() now rejects paths exceeding _MAX_FIELD_MASK_DEPTH (64) segments with a ValueError before they enter the tree.
_AddFieldPaths(), AddLeafNodes(), and _MergeMessage() are rewritten iteratively using explicit stacks, eliminating all unbounded Python call-stack growth as defence-in-depth.
Security impact: any server using Union(), Intersect(), or CanonicalFormFromMask() on attacker-controlled FieldMask input was vulnerable to remote DoS via a ~2KB payload.
Fixes: #26489