Hawk High

Summary

this is a critical business logic caused due to Arithmetic Error calculation, where the earning of Teachers must be 35% of all school fees paid but the logic to perform this process is implemented incorrectly causing to give each Teacher a complete 35% of all school fees paid instead of sharing a 35% of all fees among teachers. This is a critical flaw because if the total teachers exists >= 3 teachers then the total money received will equal : 3 × 35% = 105%, which exceeds the total fees collected, causing the LevelOne::graduateAndUpgrade function to revert and no one will be collected with their wage not even the Principal .

Vulnerability Details

1- Navigate to test/LeveOnelAndGraduateTest.t.sol file.

2- Add the following PoC code to the test file:

3- In the command line, run the following command: forge test --match-test testEachTeacherTake35PercentOfAllFees -vvv

4- Note the output :

The balance of both alice and bob is 35% of Total school Fees For each.

5- Now change the content of this function and uncomment all the comments in this function (This would add a third teacher). The output will be like this:

Note the transaction has been reverted and no one get paid.

Impact

• payout function & graduate/update function LevelOne::graduateAndUpgrade which is the most critical function for the Principal & Teachers to get paid and for Students to graduate to become unusable.

Tools Used

• Manual Recon.

• foundry Test Suite.

Recommendations

in the LevelOne::graduateAndUpgrade function the Arithmetic flow for the Teachers to get their wage should be as following: