Function: sendMessage(byte[3] _destination_chain, byte[32] _destination, byte[32][] _contents)

This function is used to send a cross-chain message to another blockchain. It charges a toll and emits a MessageSent event. This event will be monitored by the bridge system, which will relay the message to the destination chain.

Inputs

• _destination_chain

  • Control: Arbitrary.

  • Constraints: Valid supportedChains mapping.

  • Impact: Chain ID of the destination chain.

• _destination

  • Control: Arbitrary.

  • Constraints: None.

  • Impact: Target address of the destination chain.

• _contents

  • Control: Arbitrary.

  • Constraints: None.

  • Impact: Content of the message being sent, including token address, amount, and recipient address.

Branches and code coverage

Intended branches

• Check message toll is paid.

  Test coverage

• Check destination chain is supported.

  Test coverage

• Increment the nonce.

  Test coverage

• Send the toll to the miner.

  Test coverage

• Emit a MessageSent event.

  Test coverage

Negative behavior

• Revert if message toll is not paid.

  Negative test

• Revert if destination chain is not supported.

  Negative test

Function call analysis

• block.coinbase.call()

  • What happens if it reverts, reenters or does other unusual control flow? If miner is the contact address, the reentrance risk exists, which can result in a nonsequential ethNonce occurrence of MessageSent.