CVE-2000-0535 in FreeBSD
Summary
by MITRE
OpenSSL 0.9.4 and OpenSSH for FreeBSD do not properly check for the existence of the /dev/random or /dev/urandom devices, which are absent on FreeBSD Alpha systems, which causes them to produce weak keys which may be more easily broken.
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Analysis
by VulDB Data Team • 05/16/2019
This vulnerability affects OpenSSL version 0.9.4 and OpenSSH implementations on FreeBSD Alpha systems where the /dev/random and /dev/urandom device files are missing from the operating system. The flaw stems from improper device validation during cryptographic key generation processes, specifically when the software attempts to access these entropy sources for random number generation. When these devices are absent, the cryptographic libraries fail to properly handle the missing resources and instead fall back to weaker entropy sources or predictable patterns, resulting in the generation of cryptographically weak keys that are vulnerable to attack.
The technical implementation issue manifests in how these cryptographic libraries handle device existence checks during initialization. According to CWE-330, this represents a weakness in entropy sources where insufficient randomness leads to predictable cryptographic outputs. The vulnerability occurs because the software does not adequately verify that the required device files exist before attempting to use them for random number generation. This failure in input validation and resource checking creates a path where the system defaults to less secure entropy sources when the expected hardware random number generators are unavailable.
The operational impact of this vulnerability is significant for systems running FreeBSD Alpha architecture with the affected OpenSSL and OpenSSH versions. Systems relying on these cryptographic implementations for secure communications, authentication, and key management become vulnerable to attacks that exploit the predictable nature of the weak keys. Attackers can potentially perform brute force attacks or statistical analysis to recover private keys, compromise secure connections, and gain unauthorized access to protected systems. The vulnerability affects the fundamental security guarantees of cryptographic protocols, making encrypted communications and authentication mechanisms susceptible to exploitation.
Mitigation strategies for this vulnerability involve ensuring that affected systems either upgrade to patched versions of OpenSSL and OpenSSH that properly handle missing device files, or implement alternative entropy sources such as the rdrand instruction support or other secure random number generation methods. Organizations should verify that their cryptographic libraries properly check for device availability and implement fallback mechanisms that maintain cryptographic strength even when primary entropy sources are unavailable. This aligns with ATT&CK technique T1552.004 for accessing credentials and T1078.004 for valid accounts, as compromised cryptographic keys can lead to unauthorized system access. System administrators should also consider implementing proper entropy monitoring and ensuring that the underlying operating system provides adequate random number generation capabilities, particularly for Alpha architecture systems where hardware random number generators may be absent or non-functional.