CVE-2018-17968 in RuletkaIo
Summary
by MITRE
A gambling smart contract implementation for RuletkaIo, an Ethereum gambling game, generates a random value that is predictable by an external contract call. The developer wrote a random() function that uses a block timestamp and block hash from the Ethereum blockchain. This can be predicted by writing the same random function code in an exploit contract to determine the deadSeat value.
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Analysis
by VulDB Data Team • 04/06/2020
The vulnerability identified as CVE-2018-17968 represents a critical weakness in the cryptographic randomness implementation of the RuletkaIo Ethereum gambling smart contract system. This flaw fundamentally undermines the integrity of the gaming platform by creating a predictable pseudo-random number generation mechanism that can be exploited by malicious actors. The smart contract's random number generation relies on blockchain parameters including block timestamps and block hashes, which are inherently predictable and manipulable by attackers who can synchronize their exploit contracts with the blockchain state. The vulnerability stems from the fundamental misunderstanding of how blockchain data can be used for cryptographic purposes, as these parameters are publicly available and can be manipulated by miners or sophisticated attackers who control the execution timing of their exploit contracts.
The technical implementation of this vulnerability directly violates established security principles for cryptographic randomness in distributed systems. The random() function's reliance on block timestamp and block hash creates a deterministic sequence that can be reproduced by any external contract calling the same function with identical parameters. This predictable behavior allows attackers to compute the exact values that the gambling system expects to be random, specifically targeting the deadSeat value which determines game outcomes. The flaw operates at the core of the smart contract's operational logic, where the predictability of the random number generation directly translates to financial loss for legitimate players and potential profit for exploiters. This type of vulnerability is classified under CWE-330 Use of Insufficiently Random Values, which specifically addresses the use of predictable pseudo-random number generators in security-critical applications.
The operational impact of this vulnerability extends beyond simple gaming manipulation to represent a complete breakdown of trust in the smart contract system's fairness and security. Players who rely on the gambling platform for entertainment or financial gain face significant risk of losing their funds to attackers who can predict game outcomes with 100% accuracy. The vulnerability creates an attack surface that allows for automated exploitation through external contracts that can monitor blockchain state and execute their own random function calculations to determine the exact values needed to manipulate game results. This creates a scenario where legitimate users cannot trust the system's outcomes, potentially leading to complete loss of user confidence in the entire platform and broader implications for the legitimacy of smart contract-based gambling systems. The attack pattern aligns with ATT&CK technique T1059.006 for smart contract exploitation and demonstrates how predictable randomness can be leveraged for financial gain.
The mitigation strategies for this vulnerability require fundamental architectural changes to the smart contract's random number generation mechanism. The most effective approach involves implementing a verifiable random function that incorporates multiple unpredictable data sources or utilizing external oracles that provide cryptographically secure random numbers. The system should avoid relying on blockchain parameters that are inherently predictable and instead incorporate entropy from multiple sources or use established cryptographic randomness libraries. Additionally, the smart contract should implement proper time delays and additional verification mechanisms to prevent immediate exploitation. The solution must ensure that any random number generation process cannot be replicated by external contracts through simple code duplication, requiring complex cryptographic operations that cannot be easily reverse-engineered or predicted. Organizations should also implement comprehensive security audits and formal verification processes to identify similar vulnerabilities in other smart contract implementations.