CVE-2022-29185 in totp-rs
Summary
by MITRE • 05/21/2022
totp-rs is a Rust library that permits the creation of 2FA authentification tokens per time-based one-time password (TOTP). Prior to version 1.1.0, token comparison was not constant time, and could theorically be used to guess value of an TOTP token, and thus reuse it in the same time window. The attacker would have to know the password beforehand nonetheless. Starting with patched version 1.1.0, the library uses constant-time comparison. There are currently no known workarounds.
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Analysis
by VulDB Data Team • 05/27/2022
The vulnerability identified as CVE-2022-29185 affects the totp-rs Rust library, which implements time-based one-time password authentication for two-factor authentication systems. This library serves as a critical component in securing applications through TOTP-based authentication mechanisms, where users receive time-sensitive codes that validate their identity. The flaw resides in the token comparison functionality that was previously implemented using non-constant time algorithms, creating a potential side-channel attack vector that could be exploited by malicious actors.
The technical implementation of this vulnerability stems from the use of variable-time string comparison operations during TOTP token validation. When comparing the user-provided token against the expected value, the library employed algorithms that varied in execution time based on the position of matching characters. This timing variation creates a measurable difference in processing time that can be exploited through side-channel analysis techniques. Attackers could potentially determine the correct token values by measuring these timing differences, effectively performing a timing attack against the authentication system. The vulnerability is classified under CWE-203, which specifically addresses the exposure of information through timing discrepancies in software implementations.
The operational impact of this vulnerability extends beyond simple authentication bypass scenarios, as it fundamentally compromises the security model of TOTP-based systems. While attackers still require knowledge of the user's password to initiate the attack, the ability to guess or deduce TOTP values significantly weakens the overall security posture. This weakness particularly affects systems where TOTP tokens are generated for short time windows, as the window of opportunity for successful exploitation increases when attackers can make educated guesses about token values. The vulnerability affects the core principle of TOTP security, which relies on the unpredictability and uniqueness of each generated code within its validity period.
The remediation for this vulnerability involved upgrading to version 1.1.0 of the totp-rs library, which implements constant-time comparison algorithms for token validation. This fix ensures that the comparison operations take the same amount of time regardless of the input values, eliminating the timing side-channel that previously enabled attackers to extract information about the correct token values. The fix aligns with industry best practices for cryptographic implementations and follows the ATT&CK framework's guidance on preventing information disclosure through timing attacks. Organizations using this library should immediately upgrade to the patched version as there are no known workarounds available, as the vulnerability fundamentally lies in the comparison algorithm rather than in the token generation process itself. The implementation of constant-time operations represents a critical security improvement that aligns with NIST SP 800-57 recommendations for cryptographic algorithm implementations.