CVE-2016-3995 in Crypto++
Summary
by MITRE
The timing attack protection in Rijndael::Enc::ProcessAndXorBlock and Rijndael::Dec::ProcessAndXorBlock in Crypto++ (aka cryptopp) before 5.6.4 may be optimized out by the compiler, which allows attackers to conduct timing attacks.
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Analysis
by VulDB Data Team • 11/14/2022
The vulnerability identified as CVE-2016-3995 affects the Crypto++ cryptographic library version 5.6.3 and earlier, specifically targeting the Rijndael encryption algorithm implementation. This flaw resides in the timing attack protection mechanisms within the ProcessAndXorBlock functions used for both encryption and decryption operations. The issue stems from compiler optimizations that can potentially remove or weaken the deliberate timing protections designed to prevent side-channel attacks, creating a significant security risk for applications relying on this cryptographic library.
The technical flaw manifests in the way Crypto++ implements constant-time operations for the Rijndael algorithm, which is the foundation for the Advanced Encryption Standard. The library includes intentional timing protections to prevent attackers from inferring cryptographic key information through timing analysis attacks. However, when compiled with certain optimization levels, the compiler may optimize away these protective measures, effectively removing the countermeasures that were specifically implemented to defend against timing attacks. This optimization can occur at various compilation stages and depends on the compiler's ability to analyze and optimize code patterns that appear to be redundant or unnecessary from a performance perspective.
The operational impact of this vulnerability is substantial as it allows potential attackers to perform timing attacks against systems using vulnerable versions of Crypto++. Such attacks can be particularly devastating in scenarios where the cryptographic library is used for sensitive operations like password verification, key derivation, or secure communications. The vulnerability enables attackers to measure the time taken by cryptographic operations and infer information about the encryption keys or plaintext data. This type of side-channel attack can be executed remotely and does not require direct access to the system, making it particularly dangerous for web applications and network services that rely on Crypto++ for security. The attack surface expands significantly when considering that many applications and systems use Crypto++ for their cryptographic needs, potentially exposing a wide range of services to this timing attack vector.
The vulnerability aligns with CWE-310, which specifically addresses cryptographic weaknesses related to improper implementation of cryptographic operations, and relates to the broader category of side-channel attacks that are systematically documented in the ATT&CK framework under the technique of "Credential Access: Steal or Forge Kerberos Tickets" and related timing-based attacks. The flaw represents a critical failure in the cryptographic implementation's resistance to side-channel analysis, where the very protections designed to prevent timing attacks are inadvertently neutralized by compiler optimization. Organizations using vulnerable versions of Crypto++ should immediately upgrade to version 5.6.4 or later, which includes fixes that ensure timing protections remain intact regardless of compiler optimization settings. Additional mitigations may include implementing runtime checks, using alternative cryptographic libraries with proven constant-time implementations, and conducting security audits of applications that depend on Crypto++ to identify potential exposure to timing attacks. The vulnerability underscores the importance of careful consideration of compiler optimizations in cryptographic implementations and highlights the need for thorough testing of security measures under various compilation environments.