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malicious franchisee can lock funds for full duration of trust #1

NickErrant opened this Issue Nov 7, 2017 · 2 comments


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NickErrant commented Nov 7, 2017

After start of trust, current franchisee can set franchisee to address of a contract with fallback function that always throws, preventing withdraw from functioning. Assuming custodian does not stop uploading conversion rates (which is likely as they are designed to provide conversion rates for more than one trust), the funds will be locked for the full duration of the trust.


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skilesare commented Nov 7, 2017

Awesome catch. The suggestion is to always use a withdraw pattern. Any idea of a way to catch that kind of throw in solidity and continue unmolested?


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NickErrant commented Nov 8, 2017

The most secure way would be separating withdraw into separate functions for each of the relevant parties so that they can only make their own transaction fail (as you said, always use the withdraw pattern). However, I understand how that could be suboptimal for UX purposes.

A possible workaround is changing the franchisee's--and only the franchisee's--transfer() to send(). When send() fails an exception won't be propagated, instead it returns false. This would close up the locking issue, but potentially leave a franchisee without malicious intent out of a payment if their transfer fails for whatever reason.

Perhaps the two approaches could be combined: keep track of whether franchisee's send was successful, and if it was not, allow the franchisee to withdraw the missed payment through their own withdraw function.

@skilesare skilesare closed this in a2db361 Nov 9, 2017

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