CVE-2005-1720 in Mac OS X
Summary
by MITRE
AFP Server for Mac OS X 10.4.1, when using an ACL enabled volume, does not properly remove an ACL when a file is copied to a directory that does not use ACLs, which will override the POSIX file permissions for that ACL.
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Analysis
by VulDB Data Team • 10/07/2018
The vulnerability described in CVE-2005-1720 affects the AFP Server implementation in Mac OS X 10.4.1, specifically when handling access control lists on volumes that support both ACL and POSIX permissions. This issue represents a critical security flaw in the file system permission management system that can lead to unauthorized access and privilege escalation. The vulnerability stems from improper handling of file copy operations between directories with different permission models, creating a scenario where security controls can be bypassed through seemingly routine file management operations.
The technical flaw occurs when a file with an ACL is copied from an ACL-enabled directory to a destination directory that does not support ACLs. During this copy operation, the AFP Server fails to properly remove the existing ACL from the copied file, leaving behind the original access control list information. This failure results in the system maintaining both the original ACL and the POSIX permissions, creating a conflict where the POSIX permissions effectively override the ACL settings. This behavior violates the fundamental security principle that access control mechanisms should be properly enforced and maintained during file operations, as outlined in the CWE-256 category of incomplete protection mechanisms.
The operational impact of this vulnerability is significant as it allows attackers to potentially gain unauthorized access to files by exploiting the inconsistent permission handling during file copy operations. An attacker could copy a file with restrictive ACLs to a directory with permissive POSIX permissions, thereby bypassing the intended access controls and potentially gaining access to sensitive data. This vulnerability particularly affects environments where mixed permission models are used, creating an attack surface that can be exploited to escalate privileges or access restricted resources. The issue demonstrates poor implementation of the principle of least privilege, as described in the ATT&CK framework under privilege escalation techniques.
Mitigation strategies for this vulnerability should focus on immediate system updates and configuration adjustments. Organizations should ensure that all Mac OS X systems are updated to the latest available patches from Apple, as this vulnerability was addressed in subsequent releases. Additionally, system administrators should implement strict monitoring of file copy operations and permission changes, particularly when transferring files between directories with different permission model support. The recommended approach includes disabling ACL support on volumes where POSIX permissions are sufficient, or implementing proper access control policies that prevent mixed permission model scenarios. Regular security audits should verify that file permissions are correctly enforced and that no residual ACLs persist on files copied to non-ACL directories. System hardening measures should also include restricting administrative access to AFP server configurations and implementing automated monitoring solutions that can detect and alert on anomalous permission changes that might indicate exploitation attempts.