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Document potential edge cases for hook receiver contracts.md

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102 - Document potential edge cases for hook receiver contracts

The functions withdrawTokenAndCall() and withdrawTokenAndCallOnBehalf() make a call to a hook contract designated by the owner of the withdrawing stealth address. There are very few constraints on the parameters to these calls in the Umbra contract itself.

Anyone can force a call to a hook contract by transferring a small amount of tokens to an address that they control and withdrawing these tokens, passing the target address as the hook receiver.

Recommendation:

Developers of these UmbraHookReceiver contracts should be sure to validate both the caller of the tokensWithdrawn() function and the function parameters.

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102.jpg

Slide Text

  • ConsenSys Audit Umbra Finding 5.2
  • Access Control & Input Validation
  • External Contract Call w/ Untrusted Parameters
  • Document/Validate Potential Edge Cases

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