CVE-2012-6140 in Authenticator
Summary
by MITRE
pam_google_authenticator.c in the PAM module in Google Authenticator before 1.0 requires user-readable permissions for the secret file, which allows local users to bypass intended access restrictions and discover a shared secret via standard filesystem operations, a different vulnerability than CVE-2013-0258.
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Analysis
by VulDB Data Team • 05/05/2018
The vulnerability described in CVE-2012-6140 represents a critical security flaw in the Google Authenticator PAM module version 1.0 and earlier, specifically affecting the handling of secret files within the authentication framework. This issue stems from improper file permission management that creates an unintended access vector for local attackers seeking to compromise two-factor authentication mechanisms. The vulnerability is classified under CWE-732 as inadequate permissions for critical resources, which directly undermines the security model of multi-factor authentication systems.
The technical flaw manifests in the pam_google_authenticator.c module where the shared secret files are created with user-readable permissions, typically allowing world-readable access to the secret key material. This design decision enables any local user on the system to access these secret files through standard filesystem operations, effectively bypassing the intended access controls that should restrict secret file access to the specific user account and the authentication service itself. The vulnerability operates at the file system level rather than through network-based attacks, making it particularly concerning as it requires no network connectivity and can be exploited from within the system itself.
The operational impact of this vulnerability extends beyond simple information disclosure, as it fundamentally compromises the security of two-factor authentication implementations that rely on Google Authenticator. When local attackers can read secret files, they gain the ability to generate valid authentication tokens for any account that uses the compromised secret, effectively neutralizing the second factor of authentication. This allows for unauthorized access to systems and accounts, potentially leading to privilege escalation, data breaches, and complete system compromise. The vulnerability is particularly dangerous in multi-user environments where attackers can leverage this weakness to gain access to other users' accounts without requiring additional credentials or network-based attack vectors.
This vulnerability aligns with ATT&CK technique T1550.001 for use of legitimate credentials and T1078 for valid accounts, as it enables attackers to leverage legitimate authentication mechanisms while bypassing intended access controls. The flaw demonstrates poor security hygiene in file permission management and highlights the importance of proper privilege separation in authentication modules. Organizations implementing Google Authenticator for two-factor authentication should immediately address this issue by ensuring that secret files are created with appropriate permissions, typically restricting access to the specific user account and the authentication service itself. The recommended mitigation involves configuring the PAM module to create secret files with restrictive permissions such as 600, ensuring that only the owner can read and write the file content, thereby preventing unauthorized access to the shared secrets that are critical for maintaining the security of the two-factor authentication system.