Function: function withdraw()

This function withdraws an amount of the defaultToken if the ECDSA signature verifies the given id, trader, and amount.

The withdrawToken and withdrawNative functions work similarly except that the token address is included in the signature. The same threat model applies to them.

Inputs

• id

  • Control: Controlled by the caller.

  • Constraints: The mapping processedWithdrawals of the given id must not be true. The id in the given signature must match.

  • Impact: Prevent replay attacks.

• trader

  • Control: Controlled by the caller.

  • Constraints: The trader in the given signature must match.

  • Impact: Ensure the address of the recipient was authorized.

• amount

  • Control: Completely controlled by the caller.

  • Constraints: The amount in the given signature must match, and the value must be bigger than zero.

  • Impact: The amount to transfer.

• v

  • Control: Completely controlled by the caller.

  • Constraints: The v argument of the ECDSA signature can be either 27 or 28, arbitrary to be compatible with the AWS KMS.

  • Impact: A part of the signature to verify.

• r

  • Control: Completely controlled by the caller.

  • Constraints: This must be a part of the valid ECDSA signature for the given id, trader, and amount.

  • Impact: The first part of the signature to verify.

• s

  • Control: Completely controlled by the caller.

  • Constraints: This must be a part of the valid ECDSA signature with the given id, trader, and amount.

  • Impact: The second part of the signature to verify.

Branches and code coverage (including function calls)

Intended branches

• Verify the signature.

  Test coverage

• Verify the signature with another v value.

  Test coverage

• Send the defaultToken to the given trader, and verify the balance is correct.

  Test coverage

Negative behavior

• Revert when it fails to verify an incorrect signature.

  Negative test

• Revert when the amount is zero.

  Negative test

• Revert when the id is already withdrawn.

  Negative test

• Revert when the transfer fails.

  Negative test

Function call analysis

• withdraw -> getDigest(id, trader, amount, defaultToken, false)

  • External/Internal? Internal.

  • Argument control? id, trader, and amount are controlled.

  • Impact: Compute the hash of the parameters before the signature.

• withdraw -> verify(digest, v, r, s)

  • External/Internal?: Internal.

  • Argument control?: v, r, and s are controlled.

  • Impact: Verify the ECDSA signature.

• withdraw -> makeTransfer(trader, amount, defaultToken)

  • External/Internal? Internal.

  • Argument control?: trader and amount are controlled but must be signed correctly.

  • Impact: Transfer the token to the trader.