Multisig approve call binding - Require inner call payload in approve#622
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Approvers now resubmit the proposal's encoded inner call, which must be byte-equal to the payload stored at the proposal id. This binds each approval signature to the actual call being approved, so offline/cold wallet signers can decode and inspect what they sign instead of trusting an opaque proposal id. Bumps transaction_version (breaking encoding change for approve). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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illuzen
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Jul 23, 2026
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Summary
Multisig::approvenow takes the proposal's encoded inner call as a parameter and rejects the approval (CallMismatch) unless it is byte-equal to the payload stored at(multisig_address, proposal_id).This binds each approval signature to the actual call being approved: a cold wallet decodes the inner call directly from the extrinsic it signs, instead of trusting the hot/mobile wallet's claim about what an opaque proposal id contains. Wallets fetch
Proposals(multisig_address, proposal_id).callfrom state and embed it in the approve params.CallMismatchis appended after existing error variants so error indices are stable. No migration needed.MaxCallSizeand charged by the length fee; the O(n) comparison is covered by the existing call-size-linear weight component.transaction_versionbumped 2 → 3 (breaking encoding change forapprove); wallet integrations must pass the new parameter.transaction_extensions.rschange is test-only (a runtime test constructs an approve call).