CVE-2008-5162 in FreeBSD
Summary
by MITRE
The arc4random function in the kernel in FreeBSD 6.3 through 7.1 does not have a proper entropy source for a short time period immediately after boot, which makes it easier for attackers to predict the function s return values and conduct certain attacks against the GEOM framework and various network protocols, related to the Yarrow random number generator.
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Analysis
by VulDB Data Team • 05/01/2017
The vulnerability described in CVE-2008-5162 represents a critical weakness in the FreeBSD operating system's cryptographic random number generation capabilities. This issue specifically affects kernel-level implementations of the arc4random function across FreeBSD versions 6.3 through 7.1, where the underlying Yarrow random number generator fails to establish sufficient entropy immediately following system boot. The fundamental problem lies in the insufficient seeding of the random number generator during the critical early boot period, creating a window of opportunity for attackers to predict subsequent random number outputs. This weakness directly impacts the security of cryptographic operations that depend on unpredictable random values, particularly affecting the GEOM framework which handles disk geometry and storage operations.
The technical flaw stems from the improper initialization of the Yarrow random number generator, which is designed to collect entropy from various system sources to produce cryptographically secure random numbers. During the brief period after system boot, when the system has not yet accumulated sufficient entropy from hardware interrupts, disk I/O operations, and other unpredictable events, the arc4random function relies on potentially predictable initial states. This vulnerability maps directly to CWE-330, which addresses insufficient entropy in random number generation, and represents a failure in the proper implementation of cryptographic primitives as defined by security standards. The weakness becomes particularly pronounced in the immediate boot timeframe because the system's entropy pool remains dangerously low, making it possible for adversaries to reconstruct the random number sequence through statistical analysis or by observing patterns in network protocol behavior.
The operational impact of this vulnerability extends beyond simple random number prediction to compromise several critical system functions and network protocols that depend on secure randomness. Attackers can exploit this weakness to predict values used in network protocol implementations, potentially enabling man-in-the-middle attacks, session hijacking, or cryptographic key generation weaknesses within the GEOM framework. The vulnerability affects the security of various network protocols that rely on random values for session identifiers, nonce generation, and cryptographic key material. This weakness allows adversaries to perform targeted attacks against the system's cryptographic security mechanisms, particularly those involving network communications and storage operations that utilize the affected random number generator. The impact is significant because it undermines the fundamental security assumptions of cryptographic systems that depend on unpredictable random values for their effectiveness.
Mitigation strategies for this vulnerability require immediate system updates to patched FreeBSD versions that properly address the entropy initialization issue. System administrators should implement comprehensive entropy gathering mechanisms including hardware random number generators, additional entropy sources, and ensure proper system boot procedures that allow sufficient time for entropy collection. The recommended approach involves applying security patches that improve the Yarrow random number generator's initialization process and ensure adequate entropy collection before the arc4random function begins generating values. Organizations should also implement monitoring systems to detect unusual patterns in random number generation and establish proper entropy management practices. This vulnerability highlights the importance of proper entropy initialization in cryptographic systems and aligns with ATT&CK techniques related to credential access and privilege escalation through predictable random number generation, emphasizing the need for robust cryptographic implementation practices that meet industry standards for secure random number generation.