CVE-2018-0495 in Traffic Director
Summary
by MITRE
Libgcrypt before 1.7.10 and 1.8.x before 1.8.3 allows a memory-cache side-channel attack on ECDSA signatures that can be mitigated through the use of blinding during the signing process in the _gcry_ecc_ecdsa_sign function in cipher/ecc-ecdsa.c, aka the Return Of the Hidden Number Problem or ROHNP. To discover an ECDSA key, the attacker needs access to either the local machine or a different virtual machine on the same physical host.
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Analysis
by VulDB Data Team • 09/01/2023
The vulnerability described in CVE-2018-0495 represents a critical memory-cache side-channel attack targeting the Libgcrypt cryptographic library implementation of ECDSA signatures. This flaw stems from insufficient protection mechanisms during the signing process, specifically within the _gcry_ecc_ecdsa_sign function located in cipher/ecc-ecdsa.c. The vulnerability is categorized under CWE-203, which addresses "Observable Behavioral Changes," as it exposes information through timing and cache behavior patterns. The attack exploits the Return Of the Hidden Number Problem (ROHNP) technique, which leverages the relationship between the secret key and the signature to reconstruct private key information through careful analysis of cache access patterns.
The technical implementation of this vulnerability occurs when ECDSA signatures are generated without proper blinding mechanisms, leaving the cryptographic operations susceptible to cache-based timing attacks. During the signing process, the cryptographic library performs operations that create predictable cache access patterns which can be monitored by an attacker. The vulnerability specifically affects Libgcrypt versions prior to 1.7.10 and 1.8.x versions prior to 1.8.3, indicating a widespread issue across multiple release branches. The attack vector requires either local machine access or access to a different virtual machine running on the same physical host, making it particularly concerning in virtualized environments where multiple tenants share underlying hardware resources.
The operational impact of this vulnerability extends beyond simple cryptographic weakness, as it enables attackers to recover private ECDSA keys through careful analysis of cache behavior. This compromise directly violates the fundamental security assumptions of elliptic curve cryptography, where the private key should remain completely hidden from attackers. The attack can be executed by monitoring cache line usage patterns during signature generation, allowing an attacker to reconstruct the secret key through mathematical analysis of the observed behavior. This vulnerability is particularly dangerous in cloud computing and containerized environments where multiple virtual machines may share the same physical hardware, creating opportunities for cross-vm attacks. The implications align with ATT&CK technique T1059.001, which covers "Command and Scripting Interpreter: PowerShell", as attackers may use automated tools to exploit this vulnerability.
Mitigation strategies for this vulnerability require implementing proper blinding mechanisms during ECDSA signature generation, which is the recommended fix for the issue. The solution involves modifying the _gcry_ecc_ecdsa_sign function to incorporate randomization elements that prevent attackers from correlating cache access patterns with specific cryptographic operations. This approach aligns with the broader cryptographic best practices for preventing side-channel attacks, similar to those outlined in NIST SP 800-57 for key management and cryptographic operations. System administrators should immediately update to Libgcrypt versions 1.7.10 or 1.8.3 and later, which contain the necessary patches to address the cache side-channel vulnerability. Additionally, organizations should implement proper virtualization security measures, including hypervisor-level isolation and monitoring for suspicious cache behavior patterns, particularly in multi-tenant environments where the vulnerability could be exploited across different virtual machines sharing the same physical host.