CVE-2018-0737 in OpenSSL
Summary
by MITRE
The OpenSSL RSA Key generation algorithm has been shown to be vulnerable to a cache timing side channel attack. An attacker with sufficient access to mount cache timing attacks during the RSA key generation process could recover the private key. Fixed in OpenSSL 1.1.0i-dev (Affected 1.1.0-1.1.0h). Fixed in OpenSSL 1.0.2p-dev (Affected 1.0.2b-1.0.2o).
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Analysis
by VulDB Data Team • 02/28/2023
The vulnerability identified as CVE-2018-0737 represents a critical cache timing side channel attack against OpenSSL's RSA key generation implementation. This weakness specifically targets the cryptographic operations performed during the generation of RSA private keys, where the attacker can exploit timing variations in cache access patterns to infer sensitive information about the private key. The vulnerability stems from the predictable nature of cache behavior during mathematical computations, particularly when dealing with modular exponentiation operations that are fundamental to RSA key generation.
The technical flaw manifests through the use of cache timing attacks that monitor the time taken for specific memory access patterns during key generation. When OpenSSL performs RSA key generation, it executes operations that involve modular exponentiation and other mathematical computations where the execution time varies based on whether data is present in the cache or must be fetched from main memory. This timing variation creates a side channel that sophisticated attackers can exploit to reconstruct the private key components. The vulnerability affects specific versions of OpenSSL including 1.1.0 through 1.1.0h and 1.0.2b through 1.0.2o, with the issue being addressed through various mitigations in the patched versions.
The operational impact of this vulnerability is severe as it allows attackers with sufficient privileges to perform cache timing attacks during the RSA key generation process. This capability enables the recovery of private keys, effectively compromising the entire cryptographic security model. The attack requires the attacker to have access to the system during key generation, typically through local access or shared system resources where cache timing measurements can be performed. The vulnerability is particularly concerning in environments where RSA key generation occurs on systems that may be under surveillance or where attackers have the ability to monitor system behavior. Organizations using affected OpenSSL versions face potential exposure of their private keys, which could lead to decryption of sensitive data, impersonation attacks, and complete compromise of their cryptographic infrastructure.
Mitigation strategies for CVE-2018-0737 involve upgrading to patched versions of OpenSSL, specifically OpenSSL 1.1.0i-dev and 1.0.2p-dev, which implement countermeasures against cache timing attacks. These patches typically include constant-time implementations of cryptographic algorithms and additional protections against cache-based side channel attacks. Organizations should also consider implementing additional operational security measures such as ensuring proper isolation of key generation processes, monitoring for suspicious activity during cryptographic operations, and employing hardware security modules for key generation when possible. The vulnerability aligns with CWE-310, which describes cryptographic weaknesses, and relates to techniques described in the ATT&CK framework under the "Cryptanalysis" and "Side-Channel" tactics, emphasizing the need for comprehensive cryptographic security practices and the importance of protecting against timing-based information leakage in cryptographic implementations.