CVE-2002-0080 in rsync
Summary
by MITRE
rsync, when running in daemon mode, does not properly call setgroups before dropping privileges, which could provide supplemental group privileges to local users, who could then read certain files that would otherwise be disallowed.
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Analysis
by VulDB Data Team • 06/16/2024
The vulnerability described in CVE-2002-0080 affects the rsync daemon implementation and represents a classic privilege escalation issue within Unix-like operating systems. This flaw exists in the way rsync handles user privileges when operating in daemon mode, specifically concerning the sequence of system calls executed during the privilege dropping process. The vulnerability allows local users to potentially access files that should be restricted based on group permissions, creating an unexpected access path that undermines the security model of the file synchronization utility.
The technical root cause of this vulnerability lies in the improper sequence of system calls within rsync's daemon implementation. When rsync operates in daemon mode, it must drop privileges from root to a less privileged user account to prevent unauthorized access to system resources. However, the implementation fails to properly invoke the setgroups system call before executing the setuid and setgid operations. This omission means that while rsync changes the user identity, it retains the original group memberships that were active before the privilege drop. The setgroups system call is essential for properly resetting the group access control list, and its absence allows the process to maintain elevated group privileges that should have been stripped during the privilege reduction phase.
This vulnerability operates under the broader context of Unix privilege management and aligns with CWE-250, which addresses "Execute Code with Unusual/Unanticipated Privileges." The flaw enables local users to leverage their existing group memberships to access files that would normally be protected by access control lists that consider both user and group permissions. The operational impact extends beyond simple file access, as it can potentially allow attackers to read sensitive configuration files, system logs, or other restricted resources that are typically protected by group-based access controls.
The security implications of this vulnerability are significant in environments where rsync daemon is deployed with local user access. Attackers who can execute code on the system or who have local accounts with specific group memberships can exploit this weakness to bypass access controls that are fundamental to Unix security models. This issue particularly affects systems where rsync is configured to run with elevated privileges and where local users have been granted group memberships that provide access to sensitive system resources. The vulnerability demonstrates a critical flaw in privilege management implementation and represents a common class of issues where the order of system calls during privilege reduction is not properly considered.
Mitigation strategies for this vulnerability should focus on ensuring proper privilege management sequence within rsync daemon implementations. System administrators should immediately apply patches or updates that correct the privilege dropping sequence by ensuring that setgroups is properly called before setuid operations. Organizations should also implement monitoring to detect unauthorized rsync daemon usage and review group membership assignments to minimize the potential impact of such vulnerabilities. The remediation process should include verifying that all rsync daemon configurations properly handle privilege reduction and that system calls are executed in the correct sequence to prevent the retention of unnecessary group privileges. This vulnerability serves as a reminder of the critical importance of proper privilege management in system security and the potential consequences of inadequate implementation of Unix security controls.