First Flight #17: Dussehra

Summary

The current implementation of the ChoosingRam contract contains a vulnerability in the randomness generation process within the increaseValuesOfParticipants and selectRamIfNotSelected functions. These functions utilize on-chain randomness generated using block.timestamp and block.prevrandao (formerly block.difficulty). While block.prevrandao provides a slightly more random value than block.timestamp, it still falls short of providing full randomness. This vulnerability undermines the fairness and integrity of the protocol, potentially leading to biased outcomes and loss of trust among participants.

Vulnerability Details

The vulnerability arises from the use of on-chain randomness generation in the increaseValuesOfParticipants and selectRamIfNotSelected functions. These functions rely on block.timestamp and block.prevrandao for randomness, which can be predicted or influenced, allowing participants to manipulate outcomes in their favor. This undermines the fairness and integrity of the protocol, as randomness should be unpredictable and unbiased. While block.prevrandao offers slightly better randomness, it still lacks full unpredictability.

Cause of the Issue

The primary cause of the bad randomness vulnerability lies in the reliance on on-chain sources for generating random values. In the Dussehra event's Ram selection process, the function utilizes block.prevrandao to derive randomness. While block.prevrandao introduces some level of randomness, it is still deterministic and susceptible to manipulation. This reliance on on-chain sources for randomness compromises the integrity of the selection process, as it cannot guarantee truly random outcomes.

Explanation of block.prevrandao

1. block.prevrandao (formerly known as block.difficulty) is the most recent block's random value.
2. It is determined by miners and, although somewhat unpredictable, can be influenced by miners to a certain extent.
3. Combining block.timestamp and block.prevrandao with the sender's address provides some randomness, but this method is still susceptible to manipulation and prediction.

Likelihood of Exploitation

The likelihood of this vulnerability being exploited is high. Since the random value generation is predictable and can be influenced , the fairness and randomness of the selection process are compromised.

Impact

1. Unfair Advantage: Allows for potential prediction and manipulation by miners or participants, undermining the fairness of the event.

2. Participant Disadvantage: Honest participants are at a disadvantage due to the compromised random selection process, leading to a potential loss of trust in the event.

3. Protocol Integrity: Compromises the integrity of the ChoosingRam protocol, making it susceptible to manipulation and abuse.

Tools Used

1. Manual Code Review

2. Foundry

Recommendations

To address the bad randomness vulnerability in the ChoosingRam protocol, we'll integrate the Randomizer.AI service for secure and reliable randomness generation, which provides robust and secure randomness. This solution works on all of the chains that this project will be deployed. Below are the steps and modifications necessary to implement this solution:

Detailed Code Changes

1. Step 1: Add the Randomizer Interface, this defines the functions we need to interact with the Randomizer service, including requesting randomness and withdrawing funds

2. Step 2: Initialize Randomizer in the Constructor, update the contract's constructor to accept the Randomizer address and initialize it.

3. Step 3: Implement Random Value Callback, add the randomizerCallback function to handle the callback from Randomizer.

4. Step 4: Modify Vulnerable Functions, increaseValuesOfParticipants and selectRamIfNotSelected functions are updated to request randomness from Randomizer and use the received random value.
   The random value is stored in the random state variable, which is then used to determine the outcome in each function.

By implementing these changes, the contract now uses a secure and reliable source of randomness, ensuring fairness and integrity in the participant selection process.