CVE-2010-2450 in Shibboleth SP
Summary
by MITRE
The keygen.sh script in Shibboleth SP 2.0 (located in /usr/local/etc/shibboleth by default) uses OpenSSL to create a DES private key which is placed in sp-key.pm. It relies on the root umask (default 22) instead of chmoding the resulting file itself, so the generated private key is world readable by default.
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Analysis
by VulDB Data Team • 11/08/2019
The vulnerability described in CVE-2010-2450 represents a critical security flaw in the Shibboleth Service Provider 2.0 implementation that directly impacts the confidentiality and integrity of cryptographic materials. This issue stems from improper file permission handling within the key generation process, specifically within the keygen.sh script that is part of the Shibboleth SP installation. The vulnerability occurs in the default installation path at /usr/local/etc/shibboleth where the script generates cryptographic keys for the service provider. The root cause lies in the script's reliance on the system's default umask value of 22 rather than explicitly setting secure file permissions during the key generation process. This design flaw creates a fundamental security weakness that allows unauthorized users to gain access to sensitive cryptographic materials, potentially compromising the entire authentication and authorization infrastructure that relies on these keys.
The technical implementation of this vulnerability demonstrates a classic improper privilege management issue that aligns with CWE-732, which addresses incorrect permissions for critical resources. The keygen.sh script leverages OpenSSL to generate a DES private key, but fails to properly secure the resulting sp-key.pm file through explicit chmod operations. Instead, it depends entirely on the umask setting to control file permissions, which is inherently problematic since umask values can be modified by system administrators or users without proper authorization. When the umask is set to the default value of 22, it results in file permissions of 644 for regular files, meaning that the private key file becomes world-readable, exposing the cryptographic key to any user on the system. This creates a significant attack surface where malicious actors could extract the private key and potentially impersonate the service provider or decrypt sensitive communications that were intended to be protected by the cryptographic infrastructure.
The operational impact of this vulnerability extends far beyond the immediate exposure of a single private key. The compromised cryptographic material could enable attackers to perform man-in-the-middle attacks against the Shibboleth authentication system, potentially allowing them to impersonate legitimate users or service providers within the federated identity ecosystem. This vulnerability undermines the fundamental security assumptions of the Shibboleth implementation, as it allows unauthorized access to the private key that is essential for secure authentication and authorization processes. The exposure of the private key could lead to session hijacking, unauthorized access to protected resources, and potential data breaches within organizations that rely on Shibboleth for identity management. Additionally, the vulnerability affects the trust model of the entire federation, as compromised keys could be used to validate fraudulent assertions and compromise the integrity of the identity verification process. The impact is particularly severe in environments where Shibboleth is used for single sign-on services, as the compromise of a single key could affect multiple applications and services within the organization's infrastructure.
The mitigation strategies for this vulnerability must address both immediate remediation and long-term architectural improvements to prevent similar issues from occurring in the future. The most direct solution involves modifying the keygen.sh script to explicitly set secure file permissions using chmod operations after key generation, ensuring that the private key file is only accessible to the intended user or service account. This approach directly addresses the root cause by eliminating the dependency on potentially variable umask settings. Organizations should also implement proper file permission monitoring and alerting mechanisms to detect unauthorized access attempts to cryptographic materials. The remediation process should include immediate review and correction of existing key files, ensuring that any previously generated keys are properly secured and potentially rotated if compromise is suspected. From a defensive perspective, this vulnerability highlights the importance of following the principle of least privilege and explicit permission management in security-critical systems. The issue also demonstrates the necessity of implementing proper input validation and output handling in automated security tools, as the script should enforce secure default behaviors regardless of the system configuration. Organizations should consider implementing configuration management practices that enforce secure file permissions as part of their standard deployment procedures, and should regularly audit their security infrastructure to identify similar permission-related vulnerabilities that could compromise cryptographic materials. This vulnerability serves as a reminder of the critical importance of proper file permission handling in security-sensitive applications and the potential consequences of relying on system defaults for critical security controls.