CWE-1267 Base Brouillon

Policy Uses Obsolete Encoding

This vulnerability occurs when a hardware system uses outdated or deprecated encoding methods to enforce security policies and access controls.

Définition

What is CWE-1267?

This vulnerability occurs when a hardware system uses outdated or deprecated encoding methods to enforce security policies and access controls.
In a System-on-a-Chip (SoC), different hardware components constantly generate transactions to read, write, or perform actions like reset or compute. Each transaction includes identifiers for its source and destination, and is often tagged with a Security Token. This token acts as a key, telling the destination what actions the transaction is permitted to perform. A policy encoder is responsible for creating these tokens by mapping transaction details to specific security permissions. A critical security flaw arises when this policy encoder relies on an obsolete or no-longer-trusted encoding scheme. Using weak or deprecated encoding undermines the entire access control system, as the security tokens can become predictable, forgeable, or easily bypassed. This leaves the chip's assets and functions vulnerable to unauthorized access or manipulation by malicious actors.
Impact réel

Real-world CVEs caused by CWE-1267

Aucune référence CVE publique n'est liée à ce CWE dans le catalogue MITRE pour le moment.

Comment les attaquants l'exploitent

Parcours de l'attaquant étape par étape

  1. 1

    For example, consider a system that has four bus masters. The table below provides bus masters, their Security Tokens, and trust assumptions. | Bus Master | Security Token Decoding | Trust Assumptions | | --- | --- | --- | | Master_0 | "00" | Untrusted | | Master_1 | "01" | Trusted | | Master_2 | "10" | Untrusted | | Master_3 | "11" | Untrusted | The policy encoding is to be defined such that Security Token will be used in implemented access-controls. The bits in the bus transaction that contain Security-Token information are Bus_transaction [15:11]. The assets are the AES-Key registers for encryption or decryption. The key of 128 bits is implemented as a set of four, 32-bit registers. | Register | Field description | | --- | --- | | AES_ENC_DEC_KEY_0 | AES key [0:31] for encryption or decryption, Default 0x00000000 | | AES_ENC_DEC_KEY_1 | AES key [32:63] for encryption or decryption, Default 0x00000000 | | AES_ENC_DEC_KEY_2 | AES key [64:95] for encryption or decryption, Default 0x00000000 | | AES_ENC_DEC_KEY_4 | AES key [96:127] for encryption or decryption, Default 0x00000000 | Below is an example of a policy encoding scheme inherited from a previous project where all "ODD" numbered Security Tokens are trusted.

  2. 2

    The inherited policy encoding is obsolete and does not work for the new system where an untrusted bus master with an odd Security Token exists in the system, i.e., Master_3 whose Security Token is "11". Based on the old policy, the untrusted bus master (Master_3) has access to the AES-Key registers. To resolve this, a register AES_KEY_ACCESS_POLICY can be defined to provide necessary, access controls:

  3. 3

    New Policy: | | | | AES_KEY_ACCESS_POLICY | [31:0] Default 0x00000002 - agent with Security Token "1" has access to AES_ENC_DEC_KEY_0 through AES_ENC_DEC_KEY_4 registers | The AES_KEY_ACCESS_POLICY register defines which agents with a Security Token in the transaction can access the AES-key registers. Each bit in this 32-bit register defines a Security Token. There could be a maximum of 32 security Tokens that are allowed access to the AES-key registers. The number of the bit when set (i.e., "1") allows respective action from an agent whose identity matches the number of the bit and, if "0" (i.e., Clear), disallows the respective action to that corresponding agent. Thus, any bus master with Security Token "01" is allowed access to the AES-Key registers. Below is the Pseudo Code for policy encoding:

Exemple de code vulnérable

Vulnerable code

For example, consider a system that has four bus masters. The table below provides bus masters, their Security Tokens, and trust assumptions. | Bus Master | Security Token Decoding | Trust Assumptions | | --- | --- | --- | | Master_0 | "00" | Untrusted | | Master_1 | "01" | Trusted | | Master_2 | "10" | Untrusted | | Master_3 | "11" | Untrusted | The policy encoding is to be defined such that Security Token will be used in implemented access-controls. The bits in the bus transaction that contain Security-Token information are Bus_transaction [15:11]. The assets are the AES-Key registers for encryption or decryption. The key of 128 bits is implemented as a set of four, 32-bit registers. | Register | Field description | | --- | --- | | AES_ENC_DEC_KEY_0 | AES key [0:31] for encryption or decryption, Default 0x00000000 | | AES_ENC_DEC_KEY_1 | AES key [32:63] for encryption or decryption, Default 0x00000000 | | AES_ENC_DEC_KEY_2 | AES key [64:95] for encryption or decryption, Default 0x00000000 | | AES_ENC_DEC_KEY_4 | AES key [96:127] for encryption or decryption, Default 0x00000000 | Below is an example of a policy encoding scheme inherited from a previous project where all "ODD" numbered Security Tokens are trusted.

Vulnérable 
If (Bus_transaction[14] == "1")
  	Trusted = "1"
  Else
  	Trusted = "0"
  If (trusted)
  	Allow access to AES-Key registers
  Else
  	Deny access to AES-Key registers
Exemple de code sécurisé

Secure code

New Policy: | | | | AES_KEY_ACCESS_POLICY | [31:0] Default 0x00000002 - agent with Security Token "1" has access to AES_ENC_DEC_KEY_0 through AES_ENC_DEC_KEY_4 registers | The AES_KEY_ACCESS_POLICY register defines which agents with a Security Token in the transaction can access the AES-key registers. Each bit in this 32-bit register defines a Security Token. There could be a maximum of 32 security Tokens that are allowed access to the AES-key registers. The number of the bit when set (i.e., "1") allows respective action from an agent whose identity matches the number of the bit and, if "0" (i.e., Clear), disallows the respective action to that corresponding agent. Thus, any bus master with Security Token "01" is allowed access to the AES-Key registers. Below is the Pseudo Code for policy encoding:

Sécurisé 
Security_Token[4:0] = Bus_transaction[15:11]
  If (AES_KEY_ACCESS_POLICY[Security_Token] == "1")
  	Allow access to AES-Key registers
  Else
  	Deny access to AES-Key registers
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Liste de contrôle de prévention

How to prevent CWE-1267

  • Architecture and Design / Implementation Security Token Decoders should be reviewed for design inconsistency and common weaknesses. Access and programming flows should be tested in both pre-silicon and post-silicon testing.
Signaux de détection

How to detect CWE-1267

SAST High

Exécuter une analyse statique (SAST) sur le code source à la recherche du motif non sécurisé dans le flux de données.

DAST Moderate

Exécuter des tests de sécurité applicative dynamique (DAST) contre le point de terminaison en ligne.

Runtime Moderate

Surveiller les journaux runtime pour détecter des traces d'exception inhabituelles, des entrées malformées ou des tentatives de contournement d'autorisation.

Code review Moderate

Revue de code : signaler tout nouveau code qui traite les entrées de cette surface sans utiliser les helpers du framework validés.

Correction automatique Plexicus

Plexicus détecte automatiquement CWE-1267 et ouvre une PR de correction en moins de 60 secondes.

Codex Remedium analyse chaque commit, identifie cette faiblesse précise et livre une pull request prête à être relue avec le correctif. Pas de tickets. Pas de transferts.

Obtenir une démo Essayer Plexicus gratuitement
Questions fréquentes

Frequently asked questions

Qu'est-ce que CWE-1267 ?

This vulnerability occurs when a hardware system uses outdated or deprecated encoding methods to enforce security policies and access controls.

Quelle est la gravité de CWE-1267 ?

MITRE n'a pas publié de note de probabilité d'exploitation pour cette faiblesse. Traitez-la comme un impact moyen jusqu'à ce que votre modèle de menace prouve le contraire.

Quels langages ou plateformes sont affectés par CWE-1267 ?

MITRE lists the following affected platforms: Not OS-Specific, Not Architecture-Specific, Not Technology-Specific.

Comment puis-je prévenir CWE-1267 ?

Security Token Decoders should be reviewed for design inconsistency and common weaknesses. Access and programming flows should be tested in both pre-silicon and post-silicon testing.

Comment Plexicus détecte et corrige CWE-1267 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-1267 à chaque commit. Lorsqu'une correspondance est trouvée, notre agent Codex Remedium ouvre une PR de correction avec le code corrigé, les tests et un résumé d'une ligne pour le relecteur.

Où puis-je en savoir plus sur CWE-1267 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/1267.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-1267

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CWE-1220 Frère

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CWE-1233 Frère

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CWE-1252 Frère

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CWE-1257 Frère

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CWE-1259 Frère

Improper Restriction of Security Token Assignment

This vulnerability occurs when a System-on-a-Chip (SoC) fails to properly secure its Security Token mechanism. These tokens control which…

Ressources

Further reading

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