Signature Verification Can Be Bypass With Zero Address

Submitted by (4) vlad_bochok, also found by indijanc, Lambda, and wastewa

Summary:

https://code4rena.com/reports/2022-08-rigor/#h-05-add-members-to-the-not-yet-created-community

Anyone can add himself as a member of community for any future community. This can be done due to a combination of facts:

• Non initialized address storage values are defaulted to address(0)

• addMember doesn't check if community is already created

• checkSignatureValidity doesn't check for address(0)

Mitigation:

1. checkSignatureValidity/recoverKey should revert the call if an address == 0.

2. addMember should have a require(_communityId <= communityCount)

TAGS: #sig