CVE-2019-9472 in Android
Summary
by MITRE
In DCRYPTO_equals of compare.c, there is a possible timing attack due to improperly used crypto. This could lead to local information disclosure with no additional execution privileges needed. User interaction is not needed for exploitation. Product: Android Versions: Android kernel Android ID: A-130237611
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Analysis
by VulDB Data Team • 01/07/2020
The vulnerability identified as CVE-2019-9472 resides within the DCRYPTO_equals function located in the compare.c file of the Android kernel cryptography implementation. This flaw represents a critical timing attack vulnerability that exploits improper cryptographic implementation practices, specifically in how the system compares cryptographic values. The issue stems from the function's failure to perform constant-time comparisons, which creates measurable differences in execution time that can be exploited by attackers to infer sensitive information through timing analysis.
The technical implementation flaw occurs when the cryptographic comparison function does not execute in constant time regardless of input values. In traditional secure cryptographic comparisons, the execution time should remain consistent whether comparing identical or different values, preventing attackers from determining the actual values through timing variations. However, the DCRYPTO_equals function exhibits variable execution times based on input differences, creating timing side channels that can be systematically analyzed. This vulnerability falls under the CWE-203 weakness category, which specifically addresses "Observable Timing Discrepancy" in cryptographic implementations, and aligns with ATT&CK technique T1059.001 for the use of timing-based attacks against cryptographic systems.
The operational impact of this vulnerability is significant as it enables local information disclosure without requiring any additional privileges or user interaction for exploitation. Attackers can leverage this timing discrepancy to potentially extract cryptographic keys, authentication tokens, or other sensitive data through careful timing measurements. The vulnerability affects the Android kernel, which means it operates at the most fundamental level of the operating system, providing attackers with direct access to core cryptographic functions that protect system integrity and user data. This local privilege escalation path allows adversaries to access sensitive cryptographic material that should remain protected, potentially leading to broader system compromise.
Mitigation strategies for CVE-2019-9472 require immediate implementation of constant-time cryptographic comparison functions throughout the Android kernel's cryptographic libraries. System administrators should prioritize applying security patches released by Google and device manufacturers, as these updates specifically address the timing attack vulnerability in the DCRYPTO_equals function. The solution involves modifying the comparison algorithm to ensure that all execution paths take identical amounts of time regardless of input values, typically achieved through bitwise operations or other constant-time comparison techniques. Additionally, organizations should conduct comprehensive security assessments of their Android kernel implementations to identify similar timing vulnerabilities in other cryptographic functions, ensuring that all cryptographic comparisons adhere to constant-time execution principles as recommended by NIST SP 800-131A and other cryptographic standards.