CVE-2006-1320 in rssh
Summary
by MITRE
util.c in rssh 2.3.0 in Debian GNU/Linux does not use braces to make a block, which causes a check for CVS to always succeed and allows rsync and rdist to bypass intended access restrictions in rssh.conf.
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Analysis
by VulDB Data Team • 07/21/2019
The vulnerability identified as CVE-2006-1320 resides within the rssh 2.3.0 package distributed through Debian GNU/Linux systems, specifically in the util.c source file. This flaw represents a classic programming error that undermines the security controls implemented within the restricted shell environment. The issue manifests as a missing brace in a conditional code block, which fundamentally alters the execution flow of access control logic. The vulnerability affects the configuration file rssh.conf which is designed to restrict users to specific commands and prevent unauthorized access to system resources through the rsync and rdist protocols.
The technical implementation flaw stems from improper C language syntax where a conditional statement lacks the necessary curly braces to define a complete code block. This syntactic omission causes the compiler to interpret the conditional logic incorrectly, resulting in the CVS access check always evaluating to true regardless of the actual configuration settings. According to CWE-484, this represents a missing brace or block delimiter issue that leads to incorrect program behavior. The flaw allows malicious users to bypass intended access restrictions by exploiting the improper conditional logic that governs command execution permissions.
The operational impact of this vulnerability is significant as it effectively neutralizes the security controls designed to restrict user access within the rssh environment. When users authenticate through the restricted shell, they can bypass the intended access controls that should limit their capabilities to only the commands specified in rssh.conf. This creates a potential for unauthorized data transfer operations through rsync and rdist protocols, which are commonly used for file synchronization and distribution. The vulnerability essentially provides a backdoor mechanism that allows users to execute commands outside the intended restricted environment, potentially leading to data exfiltration or system compromise.
This vulnerability aligns with ATT&CK technique T1078.001 which focuses on valid accounts and legitimate credentials for unauthorized access. The flaw enables attackers to leverage legitimate system access to perform unauthorized operations. The issue demonstrates how seemingly minor code defects can have major security implications, particularly in restricted shell implementations where access control is paramount. Organizations using rssh for managing user access to system resources face potential exposure to privilege escalation attacks and unauthorized data access. The vulnerability also relates to CWE-691, which covers insufficient control flow management, highlighting the importance of proper code structure in maintaining security boundaries. System administrators should immediately apply patches or updates to address this vulnerability and ensure that the restricted shell functionality operates as intended. The flaw underscores the critical need for thorough code review processes and proper testing of access control mechanisms in security-sensitive applications.