CVE-2004-2135 in Linux
Summary
by MITRE
cryptoloop on Linux kernel 2.6.x, when used on certain file systems with a block size 1024 or greater, has certain "IV computation" weaknesses that allow watermarked files to be detected without decryption.
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Analysis
by VulDB Data Team • 12/09/2024
The vulnerability identified as CVE-2004-2135 represents a significant cryptographic weakness in the Linux kernel's cryptoloop implementation affecting versions 2.6.x. This flaw specifically manifests when cryptoloop is utilized with file systems that employ block sizes of 1024 bytes or greater, creating a scenario where the encryption implementation suffers from insufficient initialization vector (IV) computation. The core issue lies in how the cryptographic algorithm processes data blocks during the encryption process, particularly when dealing with larger block sizes that are common in modern file systems.
The technical flaw stems from inadequate IV generation mechanisms within the cryptoloop subsystem, which operates as a loop device driver that provides transparent encryption for file systems. When file systems use block sizes of 1024 bytes or more, the IV computation algorithm fails to properly randomize the encryption state for each block, resulting in predictable patterns that can be exploited by attackers. This weakness directly violates fundamental cryptographic principles where each encryption operation should maintain independent randomness to prevent pattern analysis and correlation attacks. The vulnerability is categorized under CWE-327, which addresses the use of weak or broken cryptographic algorithms, and specifically relates to improper implementation of cryptographic primitives within the kernel space.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables attackers to perform watermark detection without possessing the encryption keys or performing actual decryption operations. This capability allows adversaries to identify whether specific files contain encrypted content and potentially determine the presence of certain data patterns, which can be particularly damaging in scenarios involving sensitive information protection. The vulnerability affects the confidentiality guarantees provided by the encryption implementation, as the detection of watermarked files undermines the security assumptions that users rely upon when employing encrypted storage solutions. Attackers can leverage this weakness to perform reconnaissance activities and potentially identify specific file types or content patterns within encrypted volumes, representing a significant threat to data privacy and security.
Mitigation strategies for CVE-2004-2135 require immediate kernel updates to versions that address the IV computation weaknesses in the cryptoloop implementation, as well as the adoption of alternative encryption mechanisms that do not suffer from similar cryptographic flaws. Organizations should implement comprehensive monitoring to detect potential exploitation attempts and consider transitioning to more robust encryption solutions such as dm-crypt with LUKS or other modern encryption frameworks that properly handle IV generation and block size considerations. The vulnerability demonstrates the critical importance of proper cryptographic implementation in kernel space components and highlights the necessity of thorough security testing for cryptographic primitives before deployment. According to ATT&CK framework, this vulnerability maps to technique T1552.004 for unsecured credentials and T1005 for data from local system, as it enables unauthorized detection of encrypted content without proper authorization. System administrators should also consider implementing additional security controls such as access logging and integrity monitoring to detect potential exploitation attempts and ensure that all systems are running patched kernel versions to prevent this specific weakness from being leveraged against encrypted storage solutions.