CVE-2007-3528 in DAR
Summary
by MITRE
The blowfish mode in DAR before 2.3.4 uses weak Blowfish-CBC cryptography by (1) discarding random bits by the blowfish::make_ivec function in libdar/crypto.cpp that results in predictable and repeating IV values, and (2) direct use of a password for keying, which makes it easier for context-dependent attackers to decrypt files.
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Analysis
by VulDB Data Team • 08/12/2022
The vulnerability identified as CVE-2007-3528 affects the DAR (Disk Archive) software version 2.3.4 and earlier, specifically targeting the Blowfish-CBC cryptographic implementation within the library component. This weakness stems from fundamental flaws in how the cryptographic functions are designed and implemented, creating significant security risks for users relying on the software for data protection. The vulnerability resides in the libdar/crypto.cpp file where the blowfish::make_ivec function operates, demonstrating a critical design flaw that undermines the entire cryptographic framework. The issue manifests through two primary mechanisms that compound the security weakness, making the encryption susceptible to various attack vectors.
The first critical flaw involves the deliberate discarding of random bits within the blowfish::make_ivec function, which directly results in predictable and repeating initialization vector values. This design decision fundamentally compromises the security properties of the Blowfish-CBC mode by creating deterministic patterns in the encryption process. When initialization vectors repeat or become predictable, attackers can exploit these patterns to perform statistical analysis and potentially recover plaintext information. This weakness maps directly to CWE-327, which addresses the use of insecure or weak cryptographic algorithms and implementation flaws in cryptographic functions. The predictable IV behavior eliminates the essential randomness that CBC mode requires to maintain security guarantees, effectively rendering the encryption vulnerable to pattern analysis attacks.
The second vulnerability involves the direct use of passwords for keying without proper key derivation functions or salting mechanisms. This implementation flaw makes the system particularly susceptible to context-dependent attackers who can leverage various attack techniques including dictionary attacks, brute force attempts, and rainbow table lookups. The lack of proper key stretching or derivation means that weak passwords can be easily cracked, while the direct mapping of user input to cryptographic keys creates additional attack surface. This weakness aligns with CWE-326, which addresses the use of weak encryption algorithms and improper implementation of cryptographic functions, and also relates to CWE-256, which covers the use of passwords without proper salting or key derivation.
The operational impact of CVE-2007-3528 extends beyond simple data confidentiality breaches, as it creates a comprehensive vulnerability that affects the integrity and security of archived data. Attackers with context-dependent knowledge can exploit these weaknesses to decrypt files without proper authorization, potentially compromising sensitive information stored in archives. The vulnerability affects users who rely on DAR for backup and archival purposes, particularly in environments where data security is paramount. The combination of predictable IVs and weak key derivation creates a scenario where even moderately skilled attackers can successfully decrypt protected data, making the vulnerability particularly dangerous in production environments where data protection is critical.
Mitigation strategies for this vulnerability require immediate software upgrades to version 2.3.4 or later, where the cryptographic implementation has been corrected. Organizations should implement proper key derivation functions such as PBKDF2 or scrypt to address the password-based keying issue, and ensure that all cryptographic components use properly randomized initialization vectors. The fix addresses the core design flaws by implementing proper randomization in the IV generation process and introducing secure key derivation mechanisms that prevent attackers from easily deriving keys from user passwords. Additionally, system administrators should conduct thorough security assessments of archived data to identify any potential compromise and consider re-encrypting sensitive information with properly implemented cryptographic libraries. This vulnerability serves as a critical reminder of the importance of proper cryptographic implementation and the dangers of using weak or predictable cryptographic elements in security-critical applications.