CVE-2018-0734 in Enterprise Session Border Controller
Summary
by MITRE
The OpenSSL DSA signature algorithm has been shown to be vulnerable to a timing side channel attack. An attacker could use variations in the signing algorithm to recover the private key. Fixed in OpenSSL 1.1.1a (Affected 1.1.1). Fixed in OpenSSL 1.1.0j (Affected 1.1.0-1.1.0i). Fixed in OpenSSL 1.0.2q (Affected 1.0.2-1.0.2p).
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Analysis
by VulDB Data Team • 11/26/2024
The vulnerability identified as CVE-2018-0734 represents a critical timing side channel attack against OpenSSL's implementation of the Digital Signature Algorithm. This flaw resides in the cryptographic operations performed during DSA signature generation, where variations in execution time can inadvertently leak information about the private key components. The vulnerability affects multiple versions of OpenSSL, specifically impacting the 1.0.2 series through 1.0.2p, the 1.1.0 series through 1.1.0i, and the 1.1.1 series through 1.1.1a. The timing variations occur during the modular exponentiation operations that are fundamental to DSA signature generation, creating measurable differences in computation time that can be exploited by sophisticated attackers.
The technical implementation of this vulnerability stems from the non-constant time execution of certain mathematical operations within the DSA signing process. When OpenSSL performs DSA signature generation, it executes modular exponentiations and other cryptographic operations that do not maintain consistent execution timing regardless of the input values. This inconsistency creates a timing side channel where an attacker can measure the time differences between various signature operations and correlate these measurements to deduce information about the private key. The vulnerability is particularly dangerous because it operates at the core cryptographic implementation level, making it difficult to detect through conventional security scanning methods.
From an operational perspective, this vulnerability poses significant risks to systems relying on OpenSSL for DSA-based digital signatures, including certificate authorities, secure communication protocols, and cryptographic applications. The attack requires an attacker with access to the signing system or the ability to observe timing variations during signature operations, which may be feasible in cloud environments or shared hosting scenarios. The potential impact extends beyond immediate private key compromise to include long-term security degradation of systems using affected OpenSSL versions, as recovered private keys can be used to forge signatures and undermine the entire certificate infrastructure. This vulnerability directly maps to CWE-385 and aligns with ATT&CK technique T1552.004, which involves the use of timing attacks to extract cryptographic keys.
The remediation for CVE-2018-0734 requires immediate deployment of patched OpenSSL versions, with the specific fixes available in OpenSSL 1.1.1a, 1.1.0j, and 1.0.2q. Organizations should prioritize updating their OpenSSL installations to prevent exploitation, as the vulnerability can be leveraged by attackers with relatively modest resources to compromise cryptographic security. System administrators should also implement monitoring for unusual timing variations in cryptographic operations and consider additional security measures such as constant-time implementations for critical cryptographic functions. The fix addresses the underlying timing variations by ensuring that all cryptographic operations execute in constant time regardless of input values, thereby eliminating the side channel that enabled the attack. This vulnerability highlights the importance of constant-time cryptographic implementations and demonstrates how seemingly minor implementation details can have catastrophic security implications for cryptographic systems.