CVE-2023-32076 in in-toto
Summary
by MITRE • 05/10/2023
in-toto is a framework to protect supply chain integrity. The in-toto configuration is read from various directories and allows users to configure the behavior of the framework. The files are from directories following the XDG base directory specification. In versions 1.4.0 and prior, among the files read is `.in_totorc` which is a hidden file in the directory in which in-toto is run. If an attacker controls the inputs to a supply chain step, they can mask their activities by also passing in an `.in_totorc` file that includes the necessary exclude patterns and settings. RC files are widely used in other systems and security issues have been discovered in their implementations as well. Maintainers found in their conversations with in-toto adopters that `in_totorc` is not their preferred way to configure in-toto. As none of the options supported in `in_totorc` is unique, and can be set elsewhere using API parameters or CLI arguments, the maintainers decided to drop support for `in_totorc`. in-toto's `user_settings` module has been dropped altogether in commit 3a21d84f40811b7d191fa7bd17265c1f99599afd. Users may also sandbox functionary code as a security measure.
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Analysis
by VulDB Data Team • 05/10/2023
The CVE-2023-32076 vulnerability affects the in-toto supply chain integrity framework, which is designed to protect software supply chains through cryptographic verification of package integrity and provenance. This framework operates by reading configuration files from various directories that follow the XDG base directory specification, a standard for defining where user-specific files should be stored in Unix-like operating systems. The vulnerability specifically stems from the framework's handling of a hidden configuration file named `.in_totorc` located in the working directory where in-toto is executed, representing a significant security concern within the software supply chain protection mechanism.
The technical flaw manifests in the framework's permissive configuration file handling that allows arbitrary user-controlled input to influence the execution behavior of in-toto processes. Attackers with control over supply chain steps can exploit this vulnerability by placing a malicious `.in_totorc` file in the execution directory, thereby masking their activities through the configuration's exclude patterns and other settings. This capability directly violates the principle of least privilege and undermines the integrity verification mechanisms that in-toto is designed to provide. The vulnerability aligns with CWE-276, which covers improper privileges, and represents a classic case of insecure configuration file handling that enables privilege escalation through configuration manipulation.
The operational impact of this vulnerability extends beyond simple configuration override, as it fundamentally compromises the security posture of in-toto implementations. The attack vector allows adversaries to craft malicious supply chain steps that appear legitimate while actually executing unauthorized operations, making detection extremely difficult. This vulnerability particularly affects organizations relying on in-toto for critical supply chain security, as it provides a stealthy method for attackers to bypass security controls without raising immediate alarms. The issue is exacerbated by the fact that configuration files are commonly used across various systems, and security researchers have documented similar vulnerabilities in other software systems that handle user-provided configuration files, making this a well-known class of attack pattern.
The maintainers addressed this vulnerability by completely removing support for the `.in_totorc` file in version 1.4.1 and later, effectively eliminating the attack surface through the removal of the problematic configuration mechanism. This decision reflects a security-first approach that prioritizes the integrity of the framework over backward compatibility, as evidenced by the complete removal of the `user_settings` module in commit 3a21d84f40811b7d191fa7bd17265c1f99599afd. The solution aligns with ATT&CK technique T1566.001, which covers "Phishing: Spearphishing Attachment", as the vulnerability enables attackers to use configuration files as a vector for supply chain attacks. Organizations should implement proper sandboxing of functionary code as an additional security measure, which provides defense in depth and aligns with the principle of least privilege. The remediation approach demonstrates the importance of continuous security assessment and proactive vulnerability management, particularly in critical infrastructure components like supply chain integrity frameworks that are increasingly targeted by sophisticated adversaries.