First Flight #1: PasswordStore

Summary

The getPassword() function is a view which can be called with arbitrary msg.sender as it does not require a transaction.

Vulnerability Details

If the attacker knows the address of the s_owner they can call the getPassword() function, spoofing the msg.sender as that of the owner, resulting in disclosing the password.

The s_owner address can be obtained by using cast storage to read the value of the variable if the address of the contract is known.

First, obtain the address of s_owner by reading storage slot 0 of the contract:

The address of s_owner will be the right hand half: 0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266.

Pass this address as the from address via a cast call:

Pass the returned value to to-ascii to read the value:

You can see that the value of myPassword was obtained, without knowing the private key of the s_owner address.

Impact

The value of password which should only be accessible by the contract owner is actually accessible by any account.

Tools Used

• foundry

• cast

Recommendations

Require calls to getPassword() to be a transaction, which will require msg.sender to be valid. Alternatively, you can implement a public/private key setup, where the getPassword() function accepts input of a signed message, this signature is then validated by the function using the public key, and only revealing the password after the signature is validated.