Generation of Weak Initialization Vector (IV)

Opis

The product uses a cryptographic primitive that uses an Initialization Vector (IV), but the product does not generate IVs that are sufficiently unpredictable or unique according to the expected cryptographic requirements for that primitive.

By design, some cryptographic primitives (such as block ciphers) require that IVs must have certain properties for the uniqueness and/or unpredictability of an IV. Primitives may vary in how important these properties are. If these properties are not maintained, e.g. by a bug in the code, then the cryptography may be weakened or broken by attacking the IVs themselves.

Skutki

• Confidentiality

  Read Application Data

  If the IV is not properly initialized, data that is encrypted can be compromised and information about the data can be leaked. See [REF-1179].

Zapobieganie

• Implementation

  Different cipher modes have different requirements for their IVs. When choosing and implementing a mode, it is important to understand those requirements in order to keep security guarantees intact. Generally, it is safest to generate a random IV, since it will be both unpredictable and have a very low chance of being non-unique. IVs do not have to be kept secret, so if generating duplicate IVs is a concern, a list of already-used IVs can be kept and checked against.

  NIST offers recommendations on generation of IVs for modes of which they have approved. These include options for when random IVs are not practical. For CBC, CFB, and OFB, see [REF-1175]; for GCM, see [REF-1178].

Przykłady podatności

• CVE-2020-1472 ZeroLogon vulnerability - use of a static IV of all zeroes in AES-CFB8 mode
• CVE-2011-3389 BEAST attack in SSL 3.0 / TLS 1.0. In CBC mode, chained initialization vectors are non-random, allowing decryption of HTTPS traffic using a chosen plaintext attack.
• CVE-2001-0161 wireless router does not use 6 of the 24 bits for WEP encryption, making it easier for attackers to decrypt traffic
• CVE-2001-0160 WEP card generates predictable IV values, making it easier for attackers to decrypt traffic
• CVE-2017-3225 device bootloader uses a zero initialization vector during AES-CBC
• CVE-2016-6485 crypto framework uses PHP rand function - which is not cryptographically secure - for an initialization vector
• CVE-2014-5386 encryption routine does not seed the random number generator, causing the same initialization vector to be generated repeatedly
• CVE-2020-5408 encryption functionality in an authentication framework uses a fixed null IV with CBC mode, allowing attackers to decrypt traffic in applications that use this functionality
• CVE-2017-17704 messages for a door-unlocking product use a fixed IV in CBC mode, which is the same after each restart
• CVE-2017-11133 application uses AES in CBC mode, but the pseudo-random secret and IV are generated using math.random, which is not cryptographically strong.
• CVE-2007-3528 Blowfish-CBC implementation constructs an IV where each byte is calculated modulo 8 instead of modulo 256, resulting in less than 12 bits for the effective IV length, and less than 4096 possible IV values.

Słabość nadrzędna

• CWE-330 Use of Insufficiently Random Values

Słabości podrzędne

• CWE-329 Generation of Predictable IV with CBC Mode

Kiedy powstaje

• Implementation

Dotyczy

Not Language-Specific

Uwagi

As of CWE 4.5, terminology related to randomness, entropy, and predictability can vary widely. Within the developer and other communities, "randomness" is used heavily. However, within cryptography, "entropy" is distinct, typically implied as a measurement. There are no commonly-used definitions, even within standards documents and cryptography papers. Future versions of CWE will attempt to define these terms and, if necessary, distinguish between them in ways that are appropriate for different communities but do not reduce the usability of CWE for mapping, understanding, or other scenarios.

Źródła

1. Intercepting Mobile Communications: The Insecurity of 802.11 — Nikita Borisov, Ian Goldberg, David Wagner, 3. Risks of Keystream Reuse, ACM, 2001
2. Intercepting Mobile Communications: The Insecurity of 802.11 — Nikita Borisov, Ian Goldberg, David Wagner, Appendix C, ACM, 2001
3. Birthday problem — Wikipedia, 2021
4. Initialization Vector — Wikipedia, 2021
5. Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC — NIST, 8.2 IV Constructions, 2007
6. CBC Mode is Malleable. Don't trust it for Authentication — Arxum Path Security, 2019