CVE-2017-6076 in wolfSSL
Summary
by MITRE
In versions of wolfSSL before 3.10.2 the function fp_mul_comba makes it easier to extract RSA key information for a malicious user who has access to view cache on a machine.
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Analysis
by VulDB Data Team • 08/16/2020
The vulnerability identified as CVE-2017-6076 resides within the wolfSSL cryptographic library, specifically affecting versions prior to 3.10.2. This weakness manifests in the fp_mul_comba function which is part of the library's modular arithmetic implementation. The flaw represents a side-channel attack vector that exploits cache behavior during cryptographic operations, making it particularly dangerous in environments where attackers can monitor or access cache states. The vulnerability stems from the implementation's failure to properly obscure computational patterns that reveal information about the underlying cryptographic keys.
The technical flaw in fp_mul_comba function creates a timing and cache-based side-channel attack opportunity that allows malicious actors to infer RSA key information through careful analysis of cache access patterns. When the function performs multiplication operations during RSA key processing, it leaves detectable traces in the cache memory that can be exploited by attackers with sufficient access privileges. This vulnerability operates under the principle that cache behavior during cryptographic computations can leak information about secret key values, a well-documented attack pattern that falls under the category of cache timing attacks. The issue directly relates to CWE-310, which addresses cryptographic weaknesses involving side-channel attacks and information leakage through implementation details.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the capability to reconstruct RSA private keys through repeated cache monitoring. This compromises the fundamental security guarantees of RSA encryption, potentially allowing unauthorized parties to decrypt communications, forge digital signatures, and impersonate legitimate users within systems relying on wolfSSL. The vulnerability is particularly concerning in server environments where cache monitoring tools can be deployed, as it enables attackers to perform long-term surveillance of cryptographic operations. The attack requires only access to cache state information rather than direct access to memory or cryptographic keys, making it more accessible than other attack vectors and increasing the attack surface significantly.
Mitigation strategies for CVE-2017-6076 primarily involve upgrading to wolfSSL version 3.10.2 or later, which implements proper cache masking techniques in the fp_mul_comba function. Organizations should also consider implementing additional defensive measures such as cache randomization, constant-time algorithm implementations, and regular security assessments of cryptographic libraries. The fix addresses the underlying implementation issue by ensuring that cryptographic operations do not create predictable cache access patterns that could be exploited. Security teams should also evaluate their existing monitoring systems to detect potential cache-based attacks and consider implementing hardware-level protections where available. This vulnerability demonstrates the importance of proper side-channel resistance in cryptographic implementations and aligns with ATT&CK technique T1005 which covers data from local system. Organizations must also ensure their cryptographic libraries are regularly updated and tested to prevent similar vulnerabilities from being exploited in production environments.