论文标题

在任何副本上不安全:混合案例敏感性发生的碰撞

Unsafe at Any Copy: Name Collisions from Mixing Case Sensitivities

论文作者

Basu, Aditya, Sampson, John, Qian, Zhiyun, Jaeger, Trent

论文摘要

长期以来,已将文件名称混乱攻击(例如恶意符号链接和文件蹲)作为安全漏洞的来源研究。但是,最近出现的类型,即尚未审查案例敏感性诱导的名称碰撞。这些碰撞是通过对病例敏感和对病例敏感的文件系统或目录下的名称分辨率差异引入的。一个突出的例子是最近的GIT漏洞(CVE-2021-21300),当它在受害者客户端插入一个恶意精心设计的存储库时,它可能会导致对受害者客户的执行。随着趋势包括EXT4增加了对人均情况敏感性的支持以及Windows子系统为Linux的广泛部署,即使在一个系统中,这种漏洞的前提也越来越有可能存在。 在本文中,我们首先努力研究如何以及缺乏任何统一的处理名称碰撞的方法导致责任和结果漏洞的扩散。有趣的是,我们证明了由于名称碰撞而引起的一系列新型安全挑战的存在及其不一致的处理方式和应用程序的处理不一致。具体来说,我们的实验表明,公用事业不安全地处理许多名称碰撞方案,不幸的是,其责任不幸的是,其开发人员尚未意识到威胁。我们将三个案例研究视为系统地了解新兴名称碰撞漏洞的第一步。

File name confusion attacks, such as malicious symbolic links and file squatting, have long been studied as sources of security vulnerabilities. However, a recently emerged type, i.e., case-sensitivity-induced name collisions, has not been scrutinized. These collisions are introduced by differences in name resolution under case-sensitive and case-insensitive file systems or directories. A prominent example is the recent Git vulnerability (CVE-2021-21300) which can lead to code execution on a victim client when it clones a maliciously crafted repository onto a case-insensitive file system. With trends including ext4 adding support for per-directory case-insensitivity and the broad deployment of the Windows Subsystem for Linux, the prerequisites for such vulnerabilities are increasingly likely to exist even in a single system. In this paper, we make a first effort to investigate how and where the lack of any uniform approach to handling name collisions leads to a diffusion of responsibility and resultant vulnerabilities. Interestingly, we demonstrate the existence of a range of novel security challenges arising from name collisions and their inconsistent handling by low-level utilities and applications. Specifically, our experiments show that utilities handle many name collision scenarios unsafely, leaving the responsibility to applications whose developers are unfortunately not yet aware of the threats. We examine three case studies as a first step towards systematically understanding the emerging type of name collision vulnerability.

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