CVE-2017-5681 in OpenSSL
Summary
by MITRE
The RSA-CRT implementation in the Intel QuickAssist Technology (QAT) Engine for OpenSSL versions prior to 0.5.19 may allow remote attackers to obtain private RSA keys by conducting a Lenstra side-channel attack.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 09/04/2020
The vulnerability identified as CVE-2017-5681 represents a critical security flaw in the RSA-CRT implementation within Intel QuickAssist Technology QAT Engine for OpenSSL versions prior to 0.5.19. This issue stems from the improper handling of cryptographic operations that expose sensitive information through timing variations and other side-channel characteristics. The vulnerability specifically affects systems utilizing Intel's QAT hardware acceleration for cryptographic operations, creating a pathway for remote attackers to exploit weaknesses in the implementation of RSA-CRT (Chinese Remainder Theorem) computations.
The technical flaw manifests in the way the QAT engine processes RSA private key operations using CRT optimization techniques. When performing RSA decryption or signing operations, the implementation does not adequately mask the timing differences that occur during modular exponentiation operations. This lack of constant-time execution allows attackers to observe variations in processing time that correlate with the secret bits of the private key. The vulnerability enables what is known as a Lenstra side-channel attack, where multiple timing measurements are collected and analyzed to reconstruct the private key components through mathematical analysis and statistical correlation techniques. This represents a classic example of a timing side-channel vulnerability that violates fundamental cryptographic security principles.
The operational impact of this vulnerability is severe and far-reaching across organizations relying on Intel QAT technology for secure communications. Remote attackers can exploit this weakness to compromise RSA private keys without requiring physical access or complex attack vectors. The implications extend beyond simple key theft, as compromised private keys can lead to complete certificate impersonation, man-in-the-middle attacks, and the decryption of previously intercepted communications. Systems utilizing the affected QAT engines for SSL/TLS termination, code signing, or digital signature generation become particularly vulnerable, potentially affecting web servers, email systems, and any infrastructure relying on RSA-based cryptographic operations. This vulnerability directly relates to CWE-310, which addresses cryptographic issues involving side-channel attacks, and aligns with ATT&CK technique T1552.004, focusing on credentials from password storage.
Mitigation strategies for CVE-2017-5681 require immediate action to update the affected Intel QAT Engine software to version 0.5.19 or later, which includes proper constant-time implementations and side-channel resistance measures. Organizations should also implement monitoring solutions to detect unusual patterns in cryptographic operations that might indicate exploitation attempts. Additional defensive measures include disabling RSA-CRT optimizations when possible, implementing proper key rotation procedures, and ensuring that all cryptographic operations are performed in environments with adequate physical and logical security controls. The fix addresses the root cause by introducing proper constant-time algorithms that eliminate the timing variations that enabled the side-channel attack, thereby protecting against both current and future variants of similar vulnerabilities in cryptographic implementations.